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Tri-amping, driver time alignment, and carbon fibre cones
A few days ago, I bought a Cyrus Straightline amp to go with my Cyrus 2 and
my valve amp, and I am now doing the tri-amp thing. The valve amp is on the tweeters, the Cyrus 2 on mid range, and the Straightline on bass. Some tweaking of the Behringer DSP parametric thingy with the aid of a sound level meter has yielded what, to my ears, is a pretty balanced sound. The main perceived sonic differences are bucketloads of low bass, and much more punch overall - no sign of amplifiers straining at highish volumes. Sometimes, I feel that the mid is a bit shouty, but this is only evident on some pieces of music - a lot of things have changed, and I'm stll getting settled with the new sound, so it's entirely possible that there's plenty scope for adjustment and tweaking. I just backed the midrange level down a little, so I'll see how things go. Most noticable improvements in instrument/music terms are that drums are more solid - tighter and more punchy; acoustic guitars are much better - much clearer; and classical music seems to have acquired a dynamic range I was unaware of beforehand. I haven't really cranked it up much - I did it once and got a couple of pops from the bass drivers, which got me out of my seat and diving for the volume control pretty damn quick. At the moment, it goes about as loud as I dared go when it was just the Cyrus 2 and the 3-way passive crossovers, except that it's now much, much cleaner - night and day, in fact. Methinks there's definitely something in this amplifier headroom lark. The next thing to look at is the speakers. Before I go off designing boxes, I have some questions about driver time alignment. Some background info, and then my questions... The Behringer active crossover uses, I believe, Linkwitz-Reilly 24dB/octave filters. Mid/top xover is at 3.5KHz, bass is currently 400Hz or so, and will eventually be lowered to around 80Hz. The crossover also has a settable delay on the bass output (up to 2ms, I think). Drivers are KEF B139, B110 and T27. Do I need to give driver time alignment serious consideration? If so, how do I determine the offsets? Do I align the tweeter dome with the recessed dustcap of the midrange? What about alignment with the flat-fronted B139? These are to be used as subs - will positioning them away from the mid/top make a mess of things, and can I make amends by using the delay feature of the crossover? If not, and I have to make a 3-way speaker, how do I align the B110's normal cone with the B139? What's the deal with carbon fibre cones? My KEF B110s have those plasticised or bextrene cones which received wisdom suggests are a bit dull at low volumes (experience over many years would bear this out - I've never felt that my big KEFs really rocked until the volume was up a bit). Wilmslow Audio are selling Monacor bass/mid drivers which are direct replacements for the B110 - see... https://secure.wilmslow-audio.co.uk/...onacor_Drive_U nits_17.html The SPH-135/AD polymer cone Bass is the one they tout as a B110 replacement, and they also do another version of the same driver - SPH-135/C - which has a carbon fibre cone. What would be the likely differences I'd get with these carbon fibre jobbies? -- Wally www.artbywally.com/FiatPandaRally/index.htm www.wally.myby.co.uk |
Tri-amping, driver time alignment, and carbon fibre cones
"Wally" wrote in message m... A few days ago, I bought a Cyrus Straightline amp to go with my Cyrus 2 and my valve amp, and I am now doing the tri-amp thing. The valve amp is on the tweeters, the Cyrus 2 on mid range, and the Straightline on bass. I thought it's advisable to use exactly the same poweramps (for gain) for all the amps? |
Tri-amping, driver time alignment, and carbon fibre cones
On Wed, 11 May 2005 00:35:27 +0100, "Nath" wrote:
"Wally" wrote in message om... A few days ago, I bought a Cyrus Straightline amp to go with my Cyrus 2 and my valve amp, and I am now doing the tri-amp thing. The valve amp is on the tweeters, the Cyrus 2 on mid range, and the Straightline on bass. I thought it's advisable to use exactly the same poweramps (for gain) for all the amps? Yes indeed, but If you're not using an active crossover, it's an utterly pointless exercise in any case! Wally by name....................... -- Stewart Pinkerton | Music is Art - Audio is Engineering |
Tri-amping, driver time alignment, and carbon fibre cones
Stewart Pinkerton wrote:
I thought it's advisable to use exactly the same poweramps (for gain) for all the amps? Yes indeed, but If you're not using an active crossover, it's an utterly pointless exercise in any case! I am using an active crossover. None of the amps is set to maximum volume. The active crossover allows +/- 6dB gain adjustment on each band. I can easily dial in far more treble than is neccessary. The sound level meter shows that mid and treble are fine. -- Wally www.artbywally.com/FiatPandaRally/index.htm www.wally.myby.co.uk |
Tri-amping, driver time alignment, and carbon fibre cones
Nath wrote:
I thought it's advisable to use exactly the same poweramps (for gain) for all the amps? Why? What will happen if I don't? -- Wally www.artbywally.com/FiatPandaRally/index.htm www.wally.myby.co.uk |
Tri-amping, driver time alignment, and carbon fibre cones
In article , Wally
wrote: The main perceived sonic differences are bucketloads of low bass, and much more punch overall - no sign of amplifiers straining at highish volumes. Sometimes, I feel that the mid is a bit shouty, but this is only evident on some pieces of music - a lot of things have changed, and I'm stll getting settled with the new sound, so it's entirely possible that there's plenty scope for adjustment and tweaking. I just backed the midrange level down a little, so I'll see how things go. Most noticable improvements in instrument/music terms are that drums are more solid - tighter and more punchy; acoustic guitars are much better - much clearer; and classical music seems to have acquired a dynamic range I was unaware of beforehand. How do measurements of the frequency response now compare with before you made the changes? Slainte, Jim -- Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html |
Tri-amping, driver time alignment, and carbon fibre cones
On Wed, 11 May 2005 07:20:16 GMT, "Wally" wrote:
Stewart Pinkerton wrote: I thought it's advisable to use exactly the same poweramps (for gain) for all the amps? Yes indeed, but If you're not using an active crossover, it's an utterly pointless exercise in any case! I am using an active crossover. None of the amps is set to maximum volume. The active crossover allows +/- 6dB gain adjustment on each band. I can easily dial in far more treble than is neccessary. The sound level meter shows that mid and treble are fine. OK, in that case you have a genuine option going for you. Most of the best box speakers I've heard have been active designs. Proper ones, that is, not the Linn/Naim skamkrap. -- Stewart Pinkerton | Music is Art - Audio is Engineering |
Tri-amping, driver time alignment, and carbon fibre cones
On Wed, 11 May 2005 08:58:59 +0100, Bob Latham
wrote: In article , Wally wrote: Stewart Pinkerton wrote: I thought it's advisable to use exactly the same poweramps (for gain) for all the amps? Yes indeed, but If you're not using an active crossover, it's an utterly pointless exercise in any case! I am using an active crossover. None of the amps is set to maximum volume. The active crossover allows +/- 6dB gain adjustment on each band. I can easily dial in far more treble than is neccessary. The sound level meter shows that mid and treble are fine. Since 1978 I've owned a pair of KEF model 105s. I've still got them and still love them. But some time in the 80s KEF kindly provided me with a circuit diagram for an active crossover specifically for model 105/2. I was assured that it should be fine with 105/1. Anyway I built it and spent weeks playing with the adjustments. At the time I worked for BT and borrowed a signal generator and measuring equipment to set the levels as per a graph provided by KEF. Although the slopes and levels matched what the graph showed I never got this to sound right. As you say, it did have much better bass and headroom without doubt, but the balance was not there. I concluded that there were several possible reasons why I couldn't get it right and among them ...... 1) Not using identical amps for all 6 drive units. 2) The 105/2 bass/mid xover is at 150 Htz my 105/1 is at 400Htz. Part of the 24db/oct slope comes from cabinet dimensions and natural driver roll off. The mid range cabinet on 105/2 is larger than 105/1 to extend the B110 down to 150Htz. I think I would need to change the active crossover to 400Htz to match the original design but to be honest I don't have enough knowledge to do this. Any offers of help? If you can mail or post the schematic, I can probably advise new values. -- Stewart Pinkerton | Music is Art - Audio is Engineering |
Tri-amping, driver time alignment, and carbon fibre cones
On Wed, 11 May 2005 07:20:17 GMT, "Wally" wrote:
Nath wrote: I thought it's advisable to use exactly the same poweramps (for gain) for all the amps? Why? What will happen if I don't? You'll get different levels on bass, mid and treble, which you'll have to adjust via the active crossover. -- Stewart Pinkerton | Music is Art - Audio is Engineering |
Tri-amping, driver time alignment, and carbon fibre cones
Stewart Pinkerton wrote:
Why? What will happen if I don't? You'll get different levels on bass, mid and treble, which you'll have to adjust via the active crossover. Each amplifier also has its own volume control (the Cyruses are integrated amps, the valve has an independent vol on each channel). If the issue is primarily one of disparate gain, then I don't think that's an issue. The sensitivities of the amps for full power are all around 200-300mV, and the DAC, as you may be aware, puts out 2V (pk-pk). As it is, turning the preamp much over half-way causes the limiter LEDs in the crossover to flicker (the limiter is adjustable, and is set to +6dB). -- Wally www.artbywally.com/FiatPandaRally/index.htm www.wally.myby.co.uk |
Tri-amping, driver time alignment, and carbon fibre cones
Jim Lesurf wrote:
How do measurements of the frequency response now compare with before you made the changes? Unfortunately, I didn't have the meter before the changes started - I got it after I split the bass from the rest and added the EQ. When I did get it, I only concentrated on the bass, and found that my initial (and probably somewhat rushed) by-ear bass EQ settings were rather lumpy. After some further tweaking using the meter, I think the bass sound is much improved. There's still room for improvement (according to the meter) in the 25-35Hz range, but I think need to alter the centre frequencies of the parametric bands to suit. An initial run through the full range using the Maplin test CD would suggest that everythng is pretty even from about 100Hz upwards - this did lead me to raise the bass/mid crossover point to around 350-400Hz. -- Wally www.artbywally.com/FiatPandaRally/index.htm www.wally.myby.co.uk |
Tri-amping, driver time alignment, and carbon fibre cones
Bob Latham wrote:
So I'm very interested in what you are doing, can your active Xover do 400Htz and 2500 Htz for xover frequencies? Yes. The crossover points are sweepable through the following ranges... bass/mid: 44 - 930Hz and switchable to 440Hz - 9.3KHz mid/top: 440Hz - 9.3KHz It's a Behringer Super-X Pro CX3400, and cost 84 quid. XLR connecters only, so a pile of XLR to phono adapters were needed as well. -- Wally www.artbywally.com/FiatPandaRally/index.htm www.wally.myby.co.uk |
Tri-amping, driver time alignment, and carbon fibre cones
Stewart Pinkerton wrote:
OK, in that case you have a genuine option going for you. Most of the best box speakers I've heard have been active designs. Proper ones, that is, not the Linn/Naim skamkrap. I'm currently looking at a mid/top cabinet in 18mm birch ply (because I happen to have some). The sides slope inwards at the top, the back panel slopes forwards, and the top panel slopes down towards the back. Volume is about 7 litres. Would you say that this is on the right track? What are your thoughts on this driver time alignment malarkey? Depending on how critical this is, the mid/top cabs would either be on their own stands (for easy moving around), or mounted onto the bass cabs (which I'd prefer to have out of the way). -- Wally www.artbywally.com/FiatPandaRally/index.htm www.wally.myby.co.uk |
Tri-amping, driver time alignment, and carbon fibre cones
On Wed, 11 May 2005 19:44:45 GMT, "Wally" wrote:
Stewart Pinkerton wrote: OK, in that case you have a genuine option going for you. Most of the best box speakers I've heard have been active designs. Proper ones, that is, not the Linn/Naim skamkrap. I'm currently looking at a mid/top cabinet in 18mm birch ply (because I happen to have some). The sides slope inwards at the top, the back panel slopes forwards, and the top panel slopes down towards the back. Volume is about 7 litres. Would you say that this is on the right track? No, the right track is to buy a commercial speaker. There is absolutely no way that the home-builder can match KEF, Mission, B&W etc. for matching of drivers to cabinets, and final voicing of the crossover. This has been proven in several blind trials, where £2-500 commercial speakers totally blew away much more expensive homebuilds in 'all comers' challenges. The only area where the homebuilder has a genuine advantage is in subwoofers. What are your thoughts on this driver time alignment malarkey? Depending on how critical this is, the mid/top cabs would either be on their own stands (for easy moving around), or mounted onto the bass cabs (which I'd prefer to have out of the way). Theoretically, it's a good idea, and there was a big fashion for them in the early '80s, but that seems to have died away, so it seems not to be a critical factor for most listeners. -- Stewart Pinkerton | Music is Art - Audio is Engineering |
Tri-amping, driver time alignment, and carbon fibre cones
"Wally" wrote in message m... Most noticable improvements in instrument/music terms are that drums are more solid - tighter and more punchy; acoustic guitars are much better - much clearer; and classical music seems to have acquired a dynamic range I was unaware of beforehand. I haven't really cranked it up much - I did it once and got a couple of pops from the bass drivers, which got me out of my seat and diving for the volume control pretty damn quick. At the moment, it goes about as loud as I dared go when it was just the Cyrus 2 and the 3-way passive crossovers, except that it's now much, much cleaner - night and day, in fact. Methinks there's definitely something in this amplifier headroom lark. I've been experimenting for a while now and have talked about it other threads. Time to report findings. Set up is: Cyrus Pre pre-amp without additional PSU Behringer 3400 InterM R500 amp feeding Mordaunt Short 55Ti s (20 yrs old) as mids InterM R500 feeding twin-coil car subwoofer NAD 3020 feeding two silk tweeters Crossovers at 90Hz and 3500 Hz Room about 7.5 x 5 x 2.5 m As you see from the spec sub is definitely an interim. I will build one when I know exactly what I want. Tweeters ain't great- cost about 15 ukp each. I will possibly change these to ribbons, or maybe not (see below). The results are a revelation. The overall sound is more solid and sweet, and there is no evidence of tension or strain anywhere. At last I can feel that an improvement has achieved something. I have listened to a wide range of music now at some length. including: Jazz (Davis, Zawinul, Pine) Gamelan, including big bass drum and sharp percussion Violin (Brahms op 78) Rap like Dre Voice (various) Woodwind (inc Brahms) Floyd (especially Fletcher Memorial Home and Tigers) and so on. So I am *happy*. My wife who, though non-technical, is a down-to-earth, critical listener (and critical of my spending sometimes!) agrees that we have a major improvement. I have more tweaking to do, including levels and cross-overs but the above is an interim optimum. Conclusions a Incremental improvement Behringer is a clean flexible tool Tri-amping gives headroom and clarity Perhaps I won't need a new sub Peter Scott |
Tri-amping, driver time alignment, and carbon fibre cones
In article , Wally
wrote: Jim Lesurf wrote: How do measurements of the frequency response now compare with before you made the changes? Unfortunately, I didn't have the meter before the changes started - I got it after I split the bass from the rest and added the EQ. In that case the following experiment would be of interest. 1) Make a note of the settings at present and the measured (acoustic) frequency response. 2) Alter the arrangement by using a set of series resisors to sum together the outputs from the xover, then run the combined result through just one power amp. Then run the output of the power amp to the speakers in parallel. 3) See if this sounds much the same as at present. (You may need, first, to tweak the gains of the xover sections to correct for any differences in gains of the amps and get much the same acoustic frequency response as before.) This would help establish if the differences you hear are due to the system simply acting as a 'tone control' and have little or nothing to do with using more than one power amp. I'd be interested to know what you discovered... Slainte, Jim -- Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html |
Tri-amping, driver time alignment, and carbon fibre cones
Jim Lesurf wrote:
Unfortunately, I didn't have the meter before the changes started - I got it after I split the bass from the rest and added the EQ. In that case the following experiment would be of interest. 1) Make a note of the settings at present and the measured (acoustic) frequency response. 2) Alter the arrangement by using a set of series resisors to sum together the outputs from the xover, then run the combined result through just one power amp. Then run the output of the power amp to the speakers in parallel. If this involves running the o/p through the passive xovers, then that would be a pain - I did a bunch of soldering to sort out the connections, and I'm not keen on pulling it all apart again. (See closing comments below.) This would help establish if the differences you hear are due to the system simply acting as a 'tone control' and have little or nothing to do with using more than one power amp. I'd be interested to know what you discovered... The most significant changes are better bass, cleaner volume, and better dynamics. The EQ is only on the bass channel, so, aside from removing the passive crossovers, I don't see how there can be much 'tone control' effect on the mid or top (unless the active crossover isn't as flat as it's purported to be). I have to assume that the amps are as flat as one can reasonably expect. Adding the bass EQ made a huge difference over the interim bi-amped set up (where the bass was on one amp, and the mid/top was on the other with the passive xovers still in place). The EQ on the bass hasn't brought a subtle change - it's order of magnitude stuff. Less gross is the change in dynamics and volume, but I'm satisfied that this has definitely improved - when I first replaced the 20W valve amp with the Cyrus 2, there was a clear increase in volume and, to a lesser extent, dynamics. However, I was a little disappointed that the quality still dropped markedly when I played it up loud. I wasn't sure if this was the amp running out of puff, or the speakers starting to distort (50Wpc was the most power I'd used with these speakers). Adding the second Cyrus and bringing the valve amp back into the set up has given me available power of something like 120Wpc, with no indication of the straining that I was previously hearing at higher volumes - aside from that previously-mentioned tendency for the mid to be a bit shouty at times. So, with regard to an overall 'tone control' effect, the only real changes I can think of are adding the active crossover and removing the passive ones. My feeling is that the nett change due to this is likely to be rather more subtle than obvious. Certainly, for now, my awareness/attention is focussed on the much improved bass response, the cleaner sound at volume, and the better dynamics. I feel that I'll have to live with these changes for quite a while before I can get into the more subtle stuff. To be honest, I'm not particularly interested in trying to establish how much difference there is between the system as it stands now, and how it was with all-passive xover and the single Cyrus amp - it was better than the valve amp on its own, but was still ultimately less satisfying than it could/should have been. Looking back into the mists of time, this all started with the idea of building isobaric subs out of the collection of KEF B139 drivers that I have kicking around - since this would change the nominal impedance of the bass end to 4 instead of 8 ohms, I felt that bi-amping was the way to go. (Some people suggested tri-amping at the time, but active crossovers were too expensive for me then - I had planned to bi-amp and build some sort of active crossover since I had a scope and other kit available.) I'm now less skint, the Behringer crossover is much cheaper than other kit was back then, and I'm now interested in seeing what can be done with tri-amping for no real reason other than the hell of it. First indications are positive. To my mind, the system as it stands is the baseline - for the foreseeable future, I'm essentially committed to a tri-amped set up, and the idea is to try and make it better without spending a fortune. While I was initially less than conducive to using measurements, I would say that I'm more willing to sing from that particular hymn sheet after seeing driver free air resonance graphically displayed on the scope, and having heard the improvement to the bass that came about from using the SPL meter (compared to my MkI lug-'ole attempts). With this in mind, I'll be taking a set of measurements of the overall frequency response, such that the effect of subsequent changes can be analysed objectively. -- Wally www.artbywally.com/FiatPandaRally/index.htm www.wally.myby.co.uk |
Tri-amping, driver time alignment, and carbon fibre cones
In article , Wally
wrote: Jim Lesurf wrote: Unfortunately, I didn't have the meter before the changes started - I got it after I split the bass from the rest and added the EQ. In that case the following experiment would be of interest. 1) Make a note of the settings at present and the measured (acoustic) frequency response. 2) Alter the arrangement by using a set of series resisors to sum together the outputs from the xover, then run the combined result through just one power amp. Then run the output of the power amp to the speakers in parallel. If this involves running the o/p through the passive xovers, then that would be a pain - I did a bunch of soldering to sort out the connections, and I'm not keen on pulling it all apart again. (See closing comments below.) OK. Fair enough. It may be worth noting here that you have bypassed the original passive networks for reasons I mention below... This would help establish if the differences you hear are due to the system simply acting as a 'tone control' and have little or nothing to do with using more than one power amp. I'd be interested to know what you discovered... The most significant changes are better bass, cleaner volume, and better dynamics. The EQ is only on the bass channel, so, aside from removing the passive crossovers, I don't see how there can be much 'tone control' effect on the mid or top (unless the active crossover isn't as flat as it's purported to be). I have to assume that the amps are as flat as one can reasonably expect. The point to bear in mind that the overall frequency response may be different now for a combination of reasons: 1) Removal/bypass of the original networks. These may not just have acted as crossovers. They may have alttered the in-band levels and shapes of response. 2) The power amps may have different gains. 3) Your 'crossover' points and slopes may be different to before. 4) The effective gains for the active crossover may now be different in the various bands. Hence it remains plausible that you might have obtained much the same effect by using the active crossover simply as a 'tone control' whilst using the speakers with fewer amps and leaving the passive networks in place. Indeed, of the passive networks included arrangements to deal with some detailed aspects of the speakers, the results *might* have been better in some way. Problem is that we can't tell without a suitable comparison test. Adding the bass EQ made a huge difference over the interim bi-amped set up (where the bass was on one amp, and the mid/top was on the other with the passive xovers still in place). The EQ on the bass hasn't brought a subtle change - it's order of magnitude stuff. Less gross is the change in dynamics and volume, but I'm satisfied that this has definitely improved - when I first replaced the 20W valve amp with the Cyrus 2, there was a clear increase in volume and, to a lesser extent, dynamics. However, I was a little disappointed that the quality still dropped markedly when I played it up loud. I wasn't sure if this was the amp running out of puff, or the speakers starting to distort (50Wpc was the most power I'd used with these speakers). Adding the second Cyrus and bringing the valve amp back into the set up has given me available power of something like 120Wpc, with no indication of the straining that I was previously hearing at higher volumes - aside from that previously-mentioned tendency for the mid to be a bit shouty at times. How are you defining "available power" here? It may not be as simple as just adding together the ratings for the individual amps. So, with regard to an overall 'tone control' effect, the only real changes I can think of are adding the active crossover and removing the passive ones. See above. :-) My feeling is that the nett change due to this is likely to be rather more subtle than obvious. Certainly, for now, my awareness/attention is focussed on the much improved bass response, the cleaner sound at volume, and the better dynamics. I feel that I'll have to live with these changes for quite a while before I can get into the more subtle stuff. To be honest, I'm not particularly interested in trying to establish how much difference there is between the system as it stands now, and how it was with all-passive xover and the single Cyrus amp - it was better than the valve amp on its own, but was still ultimately less satisfying than it could/should have been. That is fair enough from your point of view. You have spent your money, put in the effort, and obtained a result which you prefer. That seems an excellent result to me, and clearly justifies the effort. However I am simply trying to point out for consideration by yourself and others that there may well be a cheaper and easier way to get similar 'improvements'. This may save others some cost and effort. [snip] To my mind, the system as it stands is the baseline - for the foreseeable future, I'm essentially committed to a tri-amped set up, and the idea is to try and make it better without spending a fortune. While I was initially less than conducive to using measurements, I would say that I'm more willing to sing from that particular hymn sheet after seeing driver free air resonance graphically displayed on the scope, and having heard the improvement to the bass that came about from using the SPL meter (compared to my MkI lug-'ole attempts). With this in mind, I'll be taking a set of measurements of the overall frequency response, such that the effect of subsequent changes can be analysed objectively. One of the things I would recommend people do is to make some 'baseline' measurements of the in-room response before they start any changes. [1] This helps to assess any perceived effects and decide what may be the real reasons for improvements. This in turn aids making decisions, allows the user to focus on what is worthwhile, and to avoid waste of time or cash! :-) [1] In this context it does not matter much if the sound meter is a cheap/poor one, or if the room has an odd acoustic. The aim is to do a 'before/after' comparison and have the info as a reference. Slainte, Jim -- Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html |
Tri-amping, driver time alignment, and carbon fibre cones
Jim Lesurf wrote:
In article , Wally wrote: Jim Lesurf wrote: [snip] to the crescendo To my mind, the system as it stands is the baseline - for the foreseeable future, I'm essentially committed to a tri-amped set up, and the idea is to try and make it better without spending a fortune. While I was initially less than conducive to using measurements, I would say that I'm more willing to sing from that particular hymn sheet after seeing driver free air resonance graphically displayed on the scope, and having heard the improvement to the bass that came about from using the SPL meter (compared to my MkI lug-'ole attempts). With this in mind, I'll be taking a set of measurements of the overall frequency response, such that the effect of subsequent changes can be analysed objectively. One of the things I would recommend people do is to make some 'baseline' measurements of the in-room response before they start any changes. [1] This helps to assess any perceived effects and decide what may be the real reasons for improvements. This in turn aids making decisions, allows the user to focus on what is worthwhile, and to avoid waste of time or cash! :-) [1] In this context it does not matter much if the sound meter is a cheap/poor one, or if the room has an odd acoustic. The aim is to do a 'before/after' comparison and have the info as a reference. Slainte, Jim Jim - or anyone. I did try this and got quite bizarre results - huge* dips at certain frequencies I would not have expected, in fact the only flat region was between 2kHz and 4 Kkz. That was using various frequency steps (60) between 100Hz and 6KHz. For a quicker cruel test - say 10 steps - what would you regard as the key frequencies at which levels should be equal? Thanks Rob * well, the peak signal was 60dB (flat 1.7-3.9kHz) at the listening place; min 20dB at 500Hz, 100Hz; and 35dB 5.4kHz and 4.5kHz |
Tri-amping, driver time alignment, and carbon fibre cones
In article , Rob
wrote: Jim Lesurf wrote: One of the things I would recommend people do is to make some 'baseline' measurements of the in-room response before they start any changes. [snip] Jim - or anyone. I did try this and got quite bizarre results - huge* dips at certain frequencies I would not have expected, in fact the only flat region was between 2kHz and 4 Kkz. That was using various frequency steps (60) between 100Hz and 6KHz. TBH the results you got are probably 'typical' rather than 'bizarre'. :-) The problem is that the acoustics of most normal domestic rooms will produce large variations in response as you change the frequency of sustained tones. You will also find that moving the speakers, or listening location, or other furniture, will alter the details! This was why I was saying that any such tests are really for 'comparison' purposes - a 'before' to compare with 'after'. Ideally keeping everything *except* the changes of interest (e.g. use of active arrangement, etc) the same. This means the room effects are the same 'before' and 'after' so you can assess what you are interested in. For a quicker cruel test - say 10 steps - what would you regard as the key frequencies at which levels should be equal? If you want to keep down the number of measurements then the best bet would be something like 1/3rd octave bandlimited noise. This tends to average over some of the room 'peaks and dips' and will give a broad-brush impression for comparisons. This means you can cover 20Hz to 20kHz with around 10 bands. If using sinewaves, I'd tend to recommend more than 10 frequencies unless you just want to focus on one range - e.g. just the bass region. FWIW I have an 'Alan Parsons' test CD which does have banded noise for tests like these. IIRC they are 1/10th octave, but I can't find the CD at the moment to check! In most rooms the best thing is just to experiment a few times to see how consistent you can get the results before moving on, and then use a set of test signals that seem to give the most consistent results Thanks Rob * well, the peak signal was 60dB (flat 1.7-3.9kHz) at the listening place; min 20dB at 500Hz, 100Hz; and 35dB 5.4kHz and 4.5kHz You have discovered one of the reasons we can take the responses in magazines with some caution. :-) Slainte, Jim -- Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html |
Tri-amping, driver time alignment, and carbon fibre cones
Jim Lesurf wrote:
The point to bear in mind that the overall frequency response may be different now for a combination of reasons: 1) Removal/bypass of the original networks. These may not just have acted as crossovers. They may have alttered the in-band levels and shapes of response. I've been doing some browsing, and it would seem that the KEF B110 has a one-octave-wide lift at about 1.5KHz. I don't know how big a lift it is. When I do my baseline measurement, I'll be paying close attention. 2) The power amps may have different gains. They have, but, as I said to Stewart, they each have volume controls, none is turned up full, and the crossover provides +/-6dB on each band. 3) Your 'crossover' points and slopes may be different to before. The points are dialled in to match those used by KEF, although I dare say the active xover has steeper slopes. A steeper slope is generally a good thing, isn't it? 4) The effective gains for the active crossover may now be different in the various bands. As I say above, they're settable - even if there are discrepancies between bands when the gains are set to zero, there's scope to compensate in any case. Hence it remains plausible that you might have obtained much the same effect by using the active crossover simply as a 'tone control' whilst using the speakers with fewer amps and leaving the passive networks in place. Maybe so, but part of the aim of this is to double up the bass drivers by making isobaric subs. The main reason for doing this is to get substantially smaller cabinets - the existing boxes are way too big, and moving them around simply isn't practical. I also wanted better bass than the lumpy response I had (the cabinets are 'wrong' for the drivers), and better power handling. Since I already had two B139s in the speakers, and two spares, this would seem a reasonable way to go. Indeed, of the passive networks included arrangements to deal with some detailed aspects of the speakers, the results *might* have been better in some way. Problem is that we can't tell without a suitable comparison test. As I said, the tri-amped set up is the baseline. The way I see it, it's easier for me to make changes and assess their effects. For example, if there are shortcomings in the midrange drivers, I'm not averse to trying something more modern that has a flatter 'natural' response (and, intuitively, this seems to be a better approach than taking a driver with a lumpy response and trying to flatten it with reactive components). FWIW, I've never been overly happy with the midrange - comments here a few months ago, about bextrene cones, rang true with my experience of them. How are you defining "available power" here? It may not be as simple as just adding together the ratings for the individual amps. I don't know what I'm talking about, so I'm being simplistic. :-) That is fair enough from your point of view. You have spent your money, put in the effort, and obtained a result which you prefer. That seems an excellent result to me, and clearly justifies the effort. No doubt about that - the tonal character is much the same, but the overall change is, to me, a step-change improvement. However I am simply trying to point out for consideration by yourself and others that there may well be a cheaper and easier way to get similar 'improvements'. This may save others some cost and effort. I appreciate your point, but I freely admit that the tri-amp thing is as much about curiosity as anything. If I discount the digital EQ for the bass, the actual spend has been about 200 quid for the active crossover and a second Cyrus. IOW, I would have added the EQ regardless of what system configuration I was using - the bass was a mess, and I think the room will always conspire to keep it that way whatever speakers I have. All-in, the spend, including connectors and cable, has been around 300-odd quid, spread around bits that are relatively cheap, and easy to sell on if I want to change the overall approach. [1] In this context it does not matter much if the sound meter is a cheap/poor one, or if the room has an odd acoustic. The aim is to do a 'before/after' comparison and have the info as a reference. Yup. I'll be doing a full range frequency response test sometime fairly soon. -- Wally www.artbywally.com/FiatPandaRally/index.htm www.wally.myby.co.uk |
Tri-amping, driver time alignment, and carbon fibre cones
In article , Wally
wrote: Jim Lesurf wrote: 2) The power amps may have different gains. They have, but, as I said to Stewart, they each have volume controls, none is turned up full, and the crossover provides +/-6dB on each band. But do you now have the same relative effective gains in the bands as before? If not, then some of the differences can be due to 'tone control' effects... 3) Your 'crossover' points and slopes may be different to before. The points are dialled in to match those used by KEF, although I dare say the active xover has steeper slopes. A steeper slope is generally a good thing, isn't it? Not necessarily. :-) The point is that as you go through the crossover region of the spectrum changing the slopes will alter the resulting response. For example, using steeper slopes may produce a 'dip'. Alternatively steeper slopes also means that the phases change in a different way, so you may get other changes for that reason. 4) The effective gains for the active crossover may now be different in the various bands. As I say above, they're settable - even if there are discrepancies between bands when the gains are set to zero, there's scope to compensate in any case. Yes. But if you are doing this 'by ear' to get the result you like, the result may be that you settle on a different response to before. This then means that you are using the xover as a tone control and getting 'improvements' from that. Hence having multiple amps may not be giving you the changes you assume. [snip] Indeed, of the passive networks included arrangements to deal with some detailed aspects of the speakers, the results *might* have been better in some way. Problem is that we can't tell without a suitable comparison test. As I said, the tri-amped set up is the baseline. The way I see it, it's easier for me to make changes and assess their effects. That is fair enough. However as I have indicated, people who have *not* yet spent the money on more power amps, etc, might find it useful to be cautious and assess what I am saying. There may be a cheaper and easier route for them. Difficult to say without suitable experiments, etc, in each individual case. Slainte, Jim -- Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html |
Tri-amping, driver time alignment, and carbon fibre cones
"Stewart Pinkerton" wrote in message "Wally" wrote in message om... I thought it's advisable to use exactly the same poweramps (for gain) for all the amps? Yes indeed... Why? Tim |
Tri-amping, driver time alignment, and carbon fibre cones
"Stewart Pinkerton" wrote in message ... You'll get different levels on bass, mid and treble, which you'll have to adjust via the active crossover. But you'll have to adjust the levels anyway, unless the sensitivities of the drivers are exactly equal. Tim |
Tri-amping, driver time alignment, and carbon fibre cones
On Mon, 16 May 2005 15:42:21 GMT, "Tim Martin"
wrote: "Stewart Pinkerton" wrote in message .. . You'll get different levels on bass, mid and treble, which you'll have to adjust via the active crossover. But you'll have to adjust the levels anyway, unless the sensitivities of the drivers are exactly equal. That's true, but unless you have access to good SPL measuring gear, you may have some difficulty knowing where 'flat' is unless everything is matched. -- Stewart Pinkerton | Music is Art - Audio is Engineering |
Tri-amping, driver time alignment, and carbon fibre cones
Jim Lesurf wrote:
2) The power amps may have different gains. They have, but, as I said to Stewart, they each have volume controls, none is turned up full, and the crossover provides +/-6dB on each band. But do you now have the same relative effective gains in the bands as before? If not, then some of the differences can be due to 'tone control' effects... I don't wish to labour the point, but 'before' is history. I don't have the 'before' numbers, so any attempt to draw comparisons is academic. Not necessarily. :-) The point is that as you go through the crossover region of the spectrum changing the slopes will alter the resulting response. For example, using steeper slopes may produce a 'dip'. Surely the crossover will have been designed to not have a dip? Alternatively steeper slopes also means that the phases change in a different way, so you may get other changes for that reason. I thought this active crossover thing was supposed to be all phase-compensated or something... 4) The effective gains for the active crossover may now be different in the various bands. As I say above, they're settable - even if there are discrepancies between bands when the gains are set to zero, there's scope to compensate in any case. Yes. But if you are doing this 'by ear' to get the result you like, the result may be that you settle on a different response to before. 'Before' is history. I'm not interested in 'before', I'm interested in taking what i've got and seeing what can be done to make it more enjoyable. This then means that you are using the xover as a tone control and getting 'improvements' from that. Fine by me. I don't care what happens within the system, so long as I like what comes out. Hence having multiple amps may not be giving you the changes you assume. They've added power, clarity and dynamics. As I said, the tri-amped set up is the baseline. The way I see it, it's easier for me to make changes and assess their effects. That is fair enough. However as I have indicated, people who have *not* yet spent the money on more power amps, etc, might find it useful to be cautious and assess what I am saying. There may be a cheaper and easier route for them. Difficult to say without suitable experiments, etc, in each individual case. I'm doing what I'm doing for myself. What other people choose to do is entirely up to them. -- Wally www.artbywally.com/FiatPandaRally/index.htm www.wally.myby.co.uk |
Tri-amping, driver time alignment, and carbon fibre cones
"Stewart Pinkerton" wrote in message ... That's true, but unless you have access to good SPL measuring gear, you may have some difficulty knowing where 'flat' is unless everything is matched. You don't need to be able to measure the SPL, just the signal generated by a microphone. Take some frequency within the range of the bass and mid-range speaker, feed a signal to the bass speaker, and measure the microphone output. Now feed the frequency to the mid-range, and adjust its level until the microphone is generating the same ouput. Repeat for the mid-range and HF speakers. You don't even need a calibrated microphone. Tim |
Tri-amping, driver time alignment, and carbon fibre cones
"Wally" wrote in message ... I thought this active crossover thing was supposed to be all phase-compensated or something... The Behringer crossover slope is fixed at 24dB/octave, and the output is summed to flat. These things simply work. I should think that, as one accumulates a collection of amplifiers, it becomes cheaper to use an active crossover with "free" amplifiers than to build a high-slope passive crossover. Tim |
Tri-amping, driver time alignment, and carbon fibre cones
Tim Martin wrote:
I thought this active crossover thing was supposed to be all phase-compensated or something... The Behringer crossover slope is fixed at 24dB/octave, and the output is summed to flat. Yeah, that sounds about right. These things simply work. That's the impression I'm getting so far. I should think that, as one accumulates a collection of amplifiers, it becomes cheaper to use an active crossover with "free" amplifiers than to build a high-slope passive crossover. I was originally considering bi-amping, and building 2-way passive crossovers out of 'quality' caps and air-cored inductors. The active crossover cost about the same as the fancy passive ones would have - and I would still have needed a 2-way active crossover to bi-amp (about 60-odd quid for the 2-way Behringer). One of the nice things is that I can change an amp at relatively low cost - I'm looking out for a Cyrus 1 to replace the valve amp that's driving the tweeters. If it doesn't work out, I can just track down one of the 50W Cyruses and punt the Cyrus 1. By the same token, if a 50W Cyrus isn't up to driving the eventual bass set up, it's less painful to change out just that amp for something more powerful - and I can do so without wondering if the sound of the rest of the system will change. -- Wally www.artbywally.com/FiatPandaRally/index.htm www.wally.myby.co.uk |
Tri-amping, driver time alignment, and carbon fibre cones
On Mon, 16 May 2005 19:18:50 GMT, "Wally" wrote:
Jim Lesurf wrote: The point is that as you go through the crossover region of the spectrum changing the slopes will alter the resulting response. For example, using steeper slopes may produce a 'dip'. Surely the crossover will have been designed to not have a dip? You seem to be missing a critical point here. Three drivers in a box will not in themselves have flat responses across their working frequency bands, so the fact that you are supplying a flat signal in three parts will have very little to do with the FR of the final speaker. Check out the crossovers in real high-quality active speakers such as Meridian or ATC, and you'll find that they are far from flat in their electrical output. -- Stewart Pinkerton | Music is Art - Audio is Engineering |
Tri-amping, driver time alignment, and carbon fibre cones
On Mon, 16 May 2005 19:58:04 GMT, "Tim Martin"
wrote: "Stewart Pinkerton" wrote in message .. . That's true, but unless you have access to good SPL measuring gear, you may have some difficulty knowing where 'flat' is unless everything is matched. You don't need to be able to measure the SPL, just the signal generated by a microphone. Only if you know that the mic response is flat! Take some frequency within the range of the bass and mid-range speaker, feed a signal to the bass speaker, and measure the microphone output. Now feed the frequency to the mid-range, and adjust its level until the microphone is generating the same ouput. Repeat for the mid-range and HF speakers. You don't even need a calibrated microphone. You do, if you want a flat response from your speakers. Also, note that you need to be *very* careful, if you're measurements are not to be swamped by room effects. You might even need to move into the garden for this, with the mic suspended above the speaker, itself several feet in the air and pointing upwards. And then you've got to set up your angles and positioning properly to get your full family of responses to calculate when you have a flat *power* response, rather than just a flat axial response, or do you want a slightly falling power response, and if so at what slope, etc etc. Measuring speakers properly ain't rocket science, but it's close................... -- Stewart Pinkerton | Music is Art - Audio is Engineering |
Tri-amping, driver time alignment, and carbon fibre cones
"Stewart Pinkerton" wrote in message ... On Mon, 16 May 2005 19:58:04 GMT, "Tim Martin" wrote: "Stewart Pinkerton" wrote in message .. . That's true, but unless you have access to good SPL measuring gear, you may have some difficulty knowing where 'flat' is unless everything is matched. You don't need to be able to measure the SPL, just the signal generated by a microphone. Only if you know that the mic response is flat! No, you don't need a flat response from the mike, because it's measuring the same frequency from the LF and mid-range speaker, and the same frequency from the mid-range and HFdriver. All you're trying to do is adjust the amplifier volume level so that a source signal generates the same energy from the LF speaker as from the mid-tange speaker. Tim |
Tri-amping, driver time alignment, and carbon fibre cones
"Stewart Pinkerton" wrote in message ... You seem to be missing a critical point here. Three drivers in a box will not in themselves have flat responses across their working frequency bands, so the fact that you are supplying a flat signal in three parts will have very little to do with the FR of the final speaker. Sure, but that has nothing to do with whether identical or different amplifiers are used for each frequency band. Tim |
Tri-amping, driver time alignment, and carbon fibre cones
Stewart Pinkerton wrote:
You seem to be missing a critical point here. Three drivers in a box will not in themselves have flat responses across their working frequency bands, Are there any that do? Flat to within what spec? ... so the fact that you are supplying a flat signal in three parts will have very little to do with the FR of the final speaker. Check out the crossovers in real high-quality active speakers such as Meridian or ATC, and you'll find that they are far from flat in their electrical output. If this becomes an issue, I have the option of moving the digital EQ to before the crossover and using it to apply corrections to the full band. (Or, indeed, adding additional EQ units.) -- Wally www.artbywally.com/FiatPandaRally/index.htm www.wally.myby.co.uk |
Tri-amping, driver time alignment, and carbon fibre cones
On Tue, 17 May 2005 20:38:24 GMT, "Tim Martin"
wrote: "Stewart Pinkerton" wrote in message .. . On Mon, 16 May 2005 19:58:04 GMT, "Tim Martin" wrote: "Stewart Pinkerton" wrote in message .. . That's true, but unless you have access to good SPL measuring gear, you may have some difficulty knowing where 'flat' is unless everything is matched. You don't need to be able to measure the SPL, just the signal generated by a microphone. Only if you know that the mic response is flat! No, you don't need a flat response from the mike, because it's measuring the same frequency from the LF and mid-range speaker, and the same frequency from the mid-range and HFdriver. True, but are you saying that you don't care what happens in the pass band? You're not going to do any equalisation? You think that passive crossovers *only* perform frequency division? All you're trying to do is adjust the amplifier volume level so that a source signal generates the same energy from the LF speaker as from the mid-tange speaker. And there's a *lot* more to that, than being sure that the levels are the same at the crossover points! -- Stewart Pinkerton | Music is Art - Audio is Engineering |
Tri-amping, driver time alignment, and carbon fibre cones
On Tue, 17 May 2005 20:41:44 GMT, "Tim Martin"
wrote: "Stewart Pinkerton" wrote in message .. . You seem to be missing a critical point here. Three drivers in a box will not in themselves have flat responses across their working frequency bands, so the fact that you are supplying a flat signal in three parts will have very little to do with the FR of the final speaker. Sure, but that has nothing to do with whether identical or different amplifiers are used for each frequency band. Indeed, but aren't you going to do anything but an utterly simplistic frequency division? That's certainly not the way to get the best sound from such a complex and flexible system. -- Stewart Pinkerton | Music is Art - Audio is Engineering |
Tri-amping, driver time alignment, and carbon fibre cones
On Tue, 17 May 2005 22:37:43 GMT, "Wally" wrote:
Stewart Pinkerton wrote: You seem to be missing a critical point here. Three drivers in a box will not in themselves have flat responses across their working frequency bands, Are there any that do? Flat to within what spec? There are a few that are flat within a couple of dB, but the *vast* majority require some compensation in the crossover. Especially the critical midrange unit. And of course the cabinet also has a significant contribution in most cases. ... so the fact that you are supplying a flat signal in three parts will have very little to do with the FR of the final speaker. Check out the crossovers in real high-quality active speakers such as Meridian or ATC, and you'll find that they are far from flat in their electrical output. If this becomes an issue, I have the option of moving the digital EQ to before the crossover and using it to apply corrections to the full band. (Or, indeed, adding additional EQ units.) That would be a wise move - but then you start to need really good measuring gear to optimise results. Bottom line, this is why even the most exotic home-builds invariably get trashed in blind comparisons with midprice commercial speakers from the likes of B&W, KEF and Mission. You simply can't support the necessary R&D when you're only making a couple of speakers. -- Stewart Pinkerton | Music is Art - Audio is Engineering |
Tri-amping, driver time alignment, and carbon fibre cones
In article , Wally
wrote: Jim Lesurf wrote: 2) The power amps may have different gains. They have, but, as I said to Stewart, they each have volume controls, none is turned up full, and the crossover provides +/-6dB on each band. But do you now have the same relative effective gains in the bands as before? If not, then some of the differences can be due to 'tone control' effects... I don't wish to labour the point, but 'before' is history. I don't have the 'before' numbers, so any attempt to draw comparisons is academic. But that may not be the case for others who are considering taking a similar path in the future. :-) Not necessarily. :-) The point is that as you go through the crossover region of the spectrum changing the slopes will alter the resulting response. For example, using steeper slopes may produce a 'dip'. Surely the crossover will have been designed to not have a dip? With the slopes and roll-overs initially applied, yes. However if you change the order or slope of the crossover then you may get a dip or a peak. You alter the filtering, you alter the response. Alternatively steeper slopes also means that the phases change in a different way, so you may get other changes for that reason. I thought this active crossover thing was supposed to be all phase-compensated or something... Depends what you mean. Some designs might ensure that the vector sum of the outputs remains 'in phase'. However many designs do not, and the speakers also affect this, etc. You change the steepness of the filters, and in general you alter their phase responses as well as their amplitude responses. 4) The effective gains for the active crossover may now be different in the various bands. As I say above, they're settable - even if there are discrepancies between bands when the gains are set to zero, there's scope to compensate in any case. Yes. But if you are doing this 'by ear' to get the result you like, the result may be that you settle on a different response to before. 'Before' is history. I'm not interested in 'before', I'm interested in taking what i've got and seeing what can be done to make it more enjoyable. See above. :-) This then means that you are using the xover as a tone control and getting 'improvements' from that. Fine by me. I don't care what happens within the system, so long as I like what comes out. Hence having multiple amps may not be giving you the changes you assume. They've added power, clarity and dynamics. Alternatively, the changes you perceive may be due to other factors. Since you have applied a 'tone control' and may have altered the overall response, you can't be sure what the reason is for your perception here. Well, you can be 'sure' in the sense of having a belief, but you don't have the evidence that would rule out other reasons for the changes. As I said, the tri-amped set up is the baseline. The way I see it, it's easier for me to make changes and assess their effects. That is fair enough. However as I have indicated, people who have *not* yet spent the money on more power amps, etc, might find it useful to be cautious and assess what I am saying. There may be a cheaper and easier route for them. Difficult to say without suitable experiments, etc, in each individual case. I'm doing what I'm doing for myself. What other people choose to do is entirely up to them. I agree. That is why I am seeking to ensure they are informed on the points we are discussing and do not assume that the use of multiple amps is certain to be the reason for the changes your perceive. The cause may be something else, which they might then obtain more easily and cheaply. Slainte, Jim -- Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html |
Tri-amping, driver time alignment, and carbon fibre cones
In article , Tim Martin
wrote: [snip] You don't even need a calibrated microphone. Agreed. In this context you only need a measurement system whose behaviour is the same 'before' and 'after' to indicate what changes have occurred. Hence the mic has to be 'stable' in its performance, but not calibrated or otherwise of 'lab measurement' quality. if you want the *actual* in room response rather than a 'before'-'after' comparison the situation would bequite difficult and require better measurement kit. Slainte, Jim -- Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html |
Tri-amping, driver time alignment, and carbon fibre cones
In article , Tim Martin
wrote: "Wally" wrote in message ... I thought this active crossover thing was supposed to be all phase-compensated or something... The Behringer crossover slope is fixed at 24dB/octave, and the output is summed to flat. That is interesting. It indicates that the vector sum of the outputs is (with gains equal) such that the vector summed output would look like the input. The problem is that the original speaker networks may not have been like this. However that would not matter if the results were adjudged to be preferrable. These things simply work. I should think that, as one accumulates a collection of amplifiers, it becomes cheaper to use an active crossover with "free" amplifiers than to build a high-slope passive crossover. Well, if the cost of the amps isn't a concern, then yes, that makes sense. I also agree that well-designed active systems can work very well, and it is potentially 'good' to avoid networks between power amp and speaker. However I am wary of the idea that multiple amps, etc, are invariably worth the change. A single amp and speaker (perhaps of 'better' quality) might prove a more effective improvement in some cases. Slainte, Jim -- Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html |
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