Peter Chant wrote:


Have done that. Two bass / mids mounted with tweeter on a piece of
kitchen counter top. Mid-woofers in series but with 2x6.8uF cap across
one.

** Wow, so he took my suggestion seriously after all.


Somehow it sounds a bit 'boxy'.


** LOL - an open plain baffle can sound a bit "woody" if it is made from ply or pine.

Mid range seems accentuated.

** Gee - a lack of low bass will do that ...

I'll
have to wire the drivers in parallel and see what happens.

** It will be 6dB louder and have even more midrange.

I wonder if
this is an effect of the baffle arrangement or a fundamental limitation
of the drivers.


** Trying to balance and passively equalise a home brew *two way* speaker by ear alone is a near impossible task - I know cos I have tried many times.

Since you cannot adjust the mid frequency level independently, you have to be damn lucky with your choice of drivers. However, with a three way design, options for tweaking the response really open up.

A couple of years back, I picked up a pair of old AR2axs for A$100. These are a three way design with a really primitive x-over and cheaply made drivers that had deteriorated to the point of useless. The money got me two, nice looking cabinets of about 45 litres volume.

I stripped them both out and started again with three Peerless drivers chosen to have similar dB/watts and in sizes to fit the existing baffle cut outs. The chosen woofer's response was modelled in the same volume box using WinISD and it was near perfect.

So, I purchased a 10 inch woofer, 4 inch midrange and 1 inch soft dome with a big mounting plate. The new mid got its own 2 litre enclosure, made from a thick cardboard port tube running back to front- which also helped to stiffen the front baffle. The original AR mids were "sealed back" types, just like old fashioned paper cone tweeters - yuck.

Much effort and time was spent on the passive x-over which was externally connected to the box until I felt no further improvement was possible. Testing was done first with sine waves and then 1/3 octave pink noise using a Rode calibrated SPL meter. Further testing was done with an AKG CK2 condenser mic and 4 cycle sine wave bursts observed on a scope - a very informative technique for revealing colouration and one which works well inside a room.

X-over frequencies ended up at 450Hz and 2.2kHz with 3dB of attenuation for mid and tweeter. I bought a 4 ohm tweeter to make sure it would have enough level to match the woofer cos you sure as heck do not what to have to attenuate that.

The tweeter's HP filter is 18dB/octave while the others are all 12dB/octave.. The x-over uses three air cored inductors and five 250VAC rated poly caps plus a couple of big bi-polars for the woofer. The mid enclosure was stuffed tight with damping material and sine wave burst testing showed there were virtually no internal echoes emerging.

The new speakers are use mainly for watching DTV and DVD movies - so had to sound natural on speech and they do.

FYI: My previous speakers were Quad ESL57s which I had used for over 20 years - they needed major restoration work done by an expert, so I sold them to a guy who was willing to finance getting that done.


..... Phil