Domestic sub: experiences please
 

"Eiron" wrote in message
...
Peter Scott wrote:
previous thread here. Used to shut down my Marantz when listening to
Pink Floyd or Joe Zawinul.

An amp with taste?

Meeow! I've always been amused by people who think their taste is
the best there is. FYI I would describe my taste as eclectic ranging
from Ravel through Mahler and Brahms to The Streets and DRE with
strong reggae, heavy metal rock and jazz highlights. So there! A
few tracks test particular things. Even though he was part of
Miles Davies' 60s groups I had not heard of JZ. I went to a gig and
was captivated. He was a very early exponent of electric piano and has
gone on from there. For testing systems I usually, like most people I guess,
choose real instruments- piano and violin in particular. The Shure
audio obstacle course vinyl for its V15-III used violin and bass drum.
Sibilant voice as well.

Electronic devices are optimised for electronic reproduction so are
less challenging or are muddy anyway. Real instruments were there
first so its up to audio systems to cope. They often don't.


I suppose you and everyone in Hong Kong have HDCD players.

I don't live in HK. A friend brought me the CD back. I didn't say I hated
soft
clipping. I said I had found it acceptable with the NAD. I dislike sharp-
cornered clipping and presumed it was because of the harmonic
content.

Peter Scott

Domestic sub: experiences please
 

"Tim S Kemp" wrote in message
...
Peter Scott wrote:

I would prefer to build rather than buy. Question is which sub driver
to buy and what
constraints are there on the design of the box. Has anyone got
experience or suggestions?

Sealed box. 18 or bigger driver. Precision Devices will be your friend if
you want to go low with big power and presence -

http://www.precisiondevices.co.uk/showdetails.asp?id=17

should be capable - your room should be big enough to hide it...

Thanks. Have you actually used one of these or know someone who
has? They look impressive and there is a UKdealer near to me.

Peter Scott

Domestic sub: experiences please
 

Peter Scott wrote:

Sealed box. 18 or bigger driver. Precision Devices will be your friend if
you want to go low with big power and presence -

http://www.precisiondevices.co.uk/showdetails.asp?id=17

should be capable - your room should be big enough to hide it...


Thanks. Have you actually used one of these or know someone who
has? They look impressive and there is a UKdealer near to me.

Fs30Hz does not a subwoofer make!

--
Eiron.

Domestic sub: experiences please
 

Peter Scott wrote:

Is the sub being driven by a bridged R500?

At present its a dual coil and bi-amped from the two channels.

Do you mean there are two drivers? In separate enclosures, one presumes?


Well form follows function if you follow the Bauhaus principles (tho
I've heard this changed nowadays to 'form follows finance!'). I'd
like to think that I can design summat that looks good. Sort of
minimalist.

I'm sure a tidy rack unit can be made - it's the mass of LEDs that would
bother me.


Couldn't put it better. The worst kind of distortion is clipping, even
when its the soft variety. I used to use a NAD amp with soft clip and
it wasn't too bad. Smaller room then of course. But nothing works
better than headroom. Sharp corners on the waves generate oodles
of hf harmonics, especially in modern amps with a vast frequency
spectrum.

If the output stage is clipping, does it matter what the amp's upper
frequency response is? Wouldn't it generate high harmonics anyway?


What's the spec power handling of the Mordaunts?

Nominally 150W pc but protected at 300W according to a reply to my
previous thread here.

Rather more than mine, then - methinks the Cyrus 2s are about the right
power for my set up (although I'm not sure about the bass end, yet).


BTW Cyrus kit often turns up on eBay. That's where I got my Pre.

Yup, I keep an eye on it.


--
Wally
www.artbywally.com/FiatPandaRally/index.htm
www.wally.myby.co.uk

Domestic sub: experiences please
 

"Wally" wrote in message
...

At present its a dual coil and bi-amped from the two channels.

Do you mean there are two drivers? In separate enclosures, one presumes?

No. The sub has two coils on the same former each driven by an amp. Its
quite
common in car audio. Not quite sure why. Perhaps its a way to mix the
left and right signals without a mixer? As you gather the sub is borrowed
from my son who's a car audio nut. Great fun if anyone anti-phases one
channel.
The signals are fighting each other, there's no movement or back emf, so
the coils melt. Some of the real car audio freaks pump several thousand
rms watts into several 15" subs and generate 170 dB. The people are
outside the car and doing it by remote control. The glass is held in place
by
clamps. Bit like Disaster Area, the rock group in Hitchhiker's Guide,
that destroyed planets when it turned up the wick. They add several lorry
alternators and cable as thick as your thumb to power the brutes. I must
say in his defence that my son isn't that loony. Just likes good sound. Car
systems are now very good indeed- and expensive. The car audio ngs
are a non-starter though. Pity.

I'm sure a tidy rack unit can be made - it's the mass of LEDs that would
bother me.
Yes, of course, tidy. But I need something a bit stylish. I'm tempted to get
a standard 19 inch pro rack. Bauhaus again. As for the LEDs, its a matter
of preference again. They look quite pretty!!!

If the output stage is clipping, does it matter what the amp's upper
frequency response is? Wouldn't it generate high harmonics anyway?
Yes but the amp would not reproduce them surely, if its slew rate was
too slow? Hey. Now you mention it, this raises an interesting point. If
the amp isn't producing them then the output waves couldn't be
that shape could they? But if its response falls off over say 30kHz then
surely it can't be producing them? Is a steep low pass filter the answer
to hard clipping. Can't be or someone would be doing it. This seems to
be a paradox doesn't it? Any guru got an answer?


Rather more than mine, then - methinks the Cyrus 2s are about the right
power for my set up (although I'm not sure about the bass end, yet).

I do have a large room. Previously in a smaller room my 60wpc was
quite enough. Current wisdom seems to be that the large the sub diameter
the better. You get more efficiency if the moving air volume is produced
by a larger area being moved a smaller distance by the cone. And area
does go up with the square of diameter. I'm going to use 15" I think. Still
waiting for the design book to arrive so I can crack out the calculator.

Peter Scott

Domestic sub: experiences please
 

Peter Scott wrote:

Do you mean there are two drivers? In separate enclosures, one
presumes?

No. The sub has two coils on the same former each driven by an amp.

raises eyebrow

Its quite
common in car audio. Not quite sure why. Perhaps its a way to mix the
left and right signals without a mixer?

Perhaps typical car audio music always has the bass in the middle of the
mix.


As you gather the sub is
borrowed from my son who's a car audio nut. Great fun if anyone
anti-phases one channel.
The signals are fighting each other, there's no movement or back emf,
so the coils melt.

Aye, that ocurred to me, too.


Some of the real car audio freaks pump several thousand
rms watts into several 15" subs and generate 170 dB. The people are
outside the car and doing it by remote control. The glass is held in
place by clamps.

Issa testosterone-fueled disco on wheels, innit?


Bit like Disaster Area, the rock group in Hitchhiker's Guide,
that destroyed planets when it turned up the wick.

Except they don't spend a year dead for tax reasons...


Yes, of course, tidy. But I need something a bit stylish. I'm tempted
to get a standard 19 inch pro rack. Bauhaus again. As for the LEDs,
its a matter of preference again. They look quite pretty!!!

Well, each to their own. :-)


If the output stage is clipping, does it matter what the amp's upper
frequency response is? Wouldn't it generate high harmonics anyway?

Yes but the amp would not reproduce them surely, if its slew rate was
too slow? Hey. Now you mention it, this raises an interesting point.
If
the amp isn't producing them then the output waves couldn't be
that shape could they? But if its response falls off over say 30kHz
then surely it can't be producing them? Is a steep low pass filter
the answer
to hard clipping. Can't be or someone would be doing it. This seems to
be a paradox doesn't it? Any guru got an answer?

Seems to me that the amp doesn't 'produce' them as such, but that they're a
natural effect of clipping the outputs. IOW, it's not a frequency response
thing, unless the amp has some sort of low pass filter after the output
devices. For instance, if you fed a squared-off 30Khz signal of low
amplitude in at the inputs, would the amp faithfully reproduce the wave at
the output, or would the corners be smoothed off? I suspect the latter.

Compare with the idea of a class-A valve stage 'producing' a 2nd harmonic.
It doesn't, really, it just distorts the signal in such a way that the
resultant can be modelled by taking the fundamental, adding a second signal
one octave higher, and mixing the two with quite specific relative
amplitudes and phase. There are plenty of other combinations of a
fundamental and a one-octave-higher signal that look nothing like a class-A
valve stage bottoming out.

In a similar way, a heavily clipped output stage can be said to be producing
loads of HF harmonics, but it isn't really - there's no signal generator
producing the notes any more than there's a frequency doubler in a class-A
valve stage. It just so happens that a square(ish) wave can be modelled by
taking a fundamental and adding loads of harmonics, presumably again of
specific relative amplitude and phase. The fact that some of these harmonics
might be well beyond the frequency response of the amplifier is neither here
nor there - they aren't passing through the amp to begin with, they're an
artefact of overdriving the output devices. However, they *are* present at
the outputs, and are getting sent to the speakers - if you put a suitable
high pass filter in, you'd have loads of HF signal at high (amplifier's
maximum?) amplitude.

I'm sure someone who knows what they're talking about will chime in
presently...


I do have a large room. Previously in a smaller room my 60wpc was
quite enough. Current wisdom seems to be that the large the sub
diameter the better. You get more efficiency if the moving air volume
is produced
by a larger area being moved a smaller distance by the cone. And area
does go up with the square of diameter. I'm going to use 15" I think.

I guess it's easier to drive a wide cone with a wide, relatively short-throw
coil than a narrow cone with a narrow, long-throw coil. Easier to make rigid
cones, IOW, than to make a narrow long-throw motor assembly that can deliver
similar undistorted output (stuff to do with the coil tending to move
outwith the magnetic field, and the limitations of the cone surround - if
the latter is too flexible to cope with the increased movement, then I guess
there's a risk of 'sideways slop').


Still waiting for the design book to arrive so I can crack out the
calculator.

Don't know what calculator you have, but I've tried a program called
BassBox, and thought it was pretty good. Takes plenty of specs for the
drivers (all that Thiele-Small stuff), lets you define the enclosure as one
of several types (sealed, reflex, various resonant pipes), does multi-driver
setups, including isobaric, and also has a bunch of stuff for defining the
room's characteristics.


--
Wally
www.artbywally.com/FiatPandaRally/index.htm
www.wally.myby.co.uk

Domestic sub: experiences please
 

Peter Scott wrote:
Thanks. Have you actually used one of these or know someone who
has? They look impressive and there is a UKdealer near to me.

PD are used in many professional applications. Definitely do the job.

--
We are the keepers of the sacred words: Ni, Pang,
and Ni-wom!

Domestic sub: experiences please
 

Eiron wrote:

Fs30Hz does not a subwoofer make!

Stick it in a big sealed enclosure and drive it below Fs?


--
We are the keepers of the sacred words: Ni, Pang,
and Ni-wom!

Domestic sub: experiences please
 

In article , Wally
wrote:
Peter Scott wrote:
[snip]


If the output stage is clipping, does it matter what the amp's upper
frequency response is? Wouldn't it generate high harmonics anyway?

Yes but the amp would not reproduce them surely, if its slew rate was
too slow? Hey. Now you mention it, this raises an interesting point.
If the amp isn't producing them then the output waves couldn't be that
shape could they? But if its response falls off over say 30kHz then
surely it can't be producing them? Is a steep low pass filter the
answer to hard clipping. Can't be or someone would be doing it. This
seems to be a paradox doesn't it? Any guru got an answer?

The above is a bit ambiguous, hence it is hard to answer your question.

If the amp clips its output, then this will tend to create frequency
components that were not present in the input. For simple examples like a
sinewave, the 'added' components will be at harmonics of the input sinewave
frequency.

Yes, you could remove these by applying a filter *after* clipping. However:

1) If you are clipping a power amp that means a filter between amp and
speaker. This would probably get in the way for various reasons. It would
also apply the same filtering when no clipping was occurring. Hence if you
wanted to use it to remove clipping from waveforms whose fundamental was
around middle C, you'd have to remove everything from around 1 kHz upwards.
This isn't likely to be regarded as worth listening to in many cases. :-)

2) If the input signal contains more than one frequency, the clipping can
also produce 'added' components that are in between, or lower than, these.
Hence a low-pass filter would not be enough to remove the products of
clipping.

Hence the general view is that is better to avoid clipping altogether. This
also means that the distinction between 'soft' and 'hard' clipping becomes
irrelevant if you arrange never to clip. :-)

Seems to me that the amp doesn't 'produce' them as such, but that
they're a natural effect of clipping the outputs.

Not sure what destinction you are trying to make. Power energes from the
amp - and drives the speaker - at frequencies that were not present in the
input. Not sure what definitions of 'produce' and 'natural' you would
regard as relevant here.


IOW, it's not a frequency response thing, unless the amp has some sort
of low pass filter after the output devices. For instance, if you fed a
squared-off 30Khz signal of low amplitude in at the inputs, would the
amp faithfully reproduce the wave at the output, or would the corners be
smoothed off? I suspect the latter.

Erm what was your "30khz signal" before you "squared off" the *input*?

Note that you are now talking about clipping waveforms *before* they are
input to an amp. This isn't quite the same as allowing the amp to fo the
clipping.

What would happen would depend on the details of the signal and the amp in
question, and the details of the "squaring off" if applied before the amp.


Compare with the idea of a class-A valve stage 'producing' a 2nd
harmonic. It doesn't, really, it just distorts the signal in such a way
that the resultant can be modelled by taking the fundamental, adding a
second signal one octave higher, and mixing the two with quite specific
relative amplitudes and phase.

As with what you wrote earlier, the above seems ambiguous. Are you assuming
the input is a single sinewave? If so, then if the input only has one
frequency, and the output has more than one, then I'm not sure where you
are saying the non-zero power of the frequencies present in the output, but
not the input have come from if the amp hasn't 'produced' them, I'm afraid.


There are plenty of other combinations of
a fundamental and a one-octave-higher signal that look nothing like a
class-A valve stage bottoming out.

In a similar way, a heavily clipped output stage can be said to be
producing loads of HF harmonics, but it isn't really - there's no signal
generator producing the notes any more than there's a frequency doubler
in a class-A valve stage.

See above comments.

It just so happens that a square(ish) wave can
be modelled by taking a fundamental and adding loads of harmonics,
presumably again of specific relative amplitude and phase. The fact that
some of these harmonics might be well beyond the frequency response of
the amplifier is neither here nor there - they aren't passing through
the amp to begin with, they're an artefact of overdriving the output
devices.

This depends on if the clipping occurs and shows up at the output, or if it
was part of the input signal. I think you'd need to distinguish between
these and address the apparent ambiguities in the somments you make above
if you wish to clarify this.

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

Domestic sub: experiences please
 

"Tim S Kemp" wrote in message
...
Peter Scott wrote:
Thanks. Have you actually used one of these or know someone who
has? They look impressive and there is a UKdealer near to me.

PD are used in many professional applications. Definitely do the job.


Thanks. That's useful

Peter Scott