I think it may have been the LS3/1?:
LS3/1 BBC HiFi-Do McIntosh/JBL/audio-technica/Jeff Rowland/Accuphase
Can anyone provide a link to details on this speaker?
First off those LS3/1 speakers, could they make them any uglier than that? Terrible British crossovers of the time also. If you are looking for a modern co-axial with a compression driver go to Radian Audio and look at their selection. They can be pricey but they do work. Don't take there word on crossover design though, you can do better with some measurements and some experimentation. On some of the older Radian drivers they had some upper frequency cavity resonance that you will have to take care of with a notch filter, and as with any compression driver a filter with a upward slanting slope will be necessary for any high frequency extension. I think I still have an earlier pair of 8" coaxials from them but they had polypropylene cones that I don't think they are using any more. The paper cones had a very different sound and had a different fs cutoff point if I remember correctly.
Flat diaphragm would be fine if you could find a material that could do it. We have cones for a reason. Silica aerogel is a possibility, but I suspect the vibration would turn it to power. The only flat diaphragms I know of that work have uniform drive across their surface. We call them electrostatics.
They are industrial speakers rather than home speakers and that was the look for a lot of industrial hardware at the time. I don't know the design details (anyone?) but there is a chance they used an acoustic filter plus a capacitor for the crossover.
I am gathering details on coaxial speakers that have a tweeter mounted on a perforated plate in front of the woofer. It is not a particularly popular configuration but is DIYable, compact and perhaps suitable for a small close monitor. It may offer less diffraction/dispersion issues than tweeters on stalks or brackets but, then again, given the lack of popularity perhaps not. Early stages.
mondogenerato,
I did consulting on a flat panel speaker at one time a few years ago. The diaphragm material was to be Kapton stretched over a plastic frame. You have to be careful as the Kapton has a tendency to fracture if you try to fold it over a sharp corner. the idea was a rectangular shape with rounded corners and edges. Sort of like an Apple computer, I think they own this shape, not..... You would then place a secondary frame over the first stretching the Kapton tight. Something like a lady would use to do needle point where they stretch a material around a hoop. Nothing says it couldn't be round, just remember to offset the drivers so they are not centered this caused all sorts of havoc with reflective waveforms. You will be limited in output as there is very little excursion with this method. But it does work.
Steven
I did consulting on a flat panel speaker at one time a few years ago. The diaphragm material was to be Kapton stretched over a plastic frame. You have to be careful as the Kapton has a tendency to fracture if you try to fold it over a sharp corner. the idea was a rectangular shape with rounded corners and edges. Sort of like an Apple computer, I think they own this shape, not..... You would then place a secondary frame over the first stretching the Kapton tight. Something like a lady would use to do needle point where they stretch a material around a hoop. Nothing says it couldn't be round, just remember to offset the drivers so they are not centered this caused all sorts of havoc with reflective waveforms. You will be limited in output as there is very little excursion with this method. But it does work.
Steven
That's the crossover (mostly) not the drivers. The Hawthorne speakers could be much better with a more suitable crossover. The drivers are not the worlds best (or worst)coaxes, but they aren't priced like it, either.I tried the 10" and 15" Silver Iris coaxials and thought they were the worst speakers I've ever listened too.
My
Andy,
One of the reasons that these speakers are not popular is that they were generally made for automotive applications and aren't of the highest quality. Another issue is that the tweeter is either directly in front of or sometimes with a mid also mounted on a plate in front of the bass cone section. This is very destructive to the radiation pattern of the cone and there is no way around this. That is why the throat mounted devices are preferred. They have a much better relationship with the cone driver and don't create the same interference patterns for the low frequency driver. Put your hand in front of any cone driver and see how it changes the sound, you are in effect loading that driver with a resistive impedance.
Steven
One of the reasons that these speakers are not popular is that they were generally made for automotive applications and aren't of the highest quality. Another issue is that the tweeter is either directly in front of or sometimes with a mid also mounted on a plate in front of the bass cone section. This is very destructive to the radiation pattern of the cone and there is no way around this. That is why the throat mounted devices are preferred. They have a much better relationship with the cone driver and don't create the same interference patterns for the low frequency driver. Put your hand in front of any cone driver and see how it changes the sound, you are in effect loading that driver with a resistive impedance.
Steven
Have you had a look at ME Geithain monitors?
They seem to be doing quite well with that 'flawed' design. Unlike many others they also publish fairly comprehensive measurements, including polar response and distortion graphs.
I have not yet found an automotive application that uses a perforated plate only stalks and brackets. Here is a JBL example using a perforated plate:
JBL Pro - Portable Sound
Note the tweeter radiation is controlled by its own waveguide and the acoustic filter keeps the high frequency radiation away from the low frequency driver. For the ideal case this is a better arrangement than a tweeter at the centre of moving mid/bass cone waveguide and approaches the normal arrangement of separate tweeter and mid/bass drivers. Of course the ideal case is not going to hold and diffraction/dispersion are going to be significant but, as I mentioned earlier, it is a compact arrangement suitable for a small close monitor and it is a lot more DIYable than designing and manufacturing coaxials in the manner of Thiel, Genelec, KEF, et al.
Still a frequency response of +-1.5dB and less than 0.3% THD at 96dBSPL works for me.
Plus I have never heard a bad word about them by those who use them professionally. They seem to be right up there with the best studio monitors currently available, together with ATC and Neumann (prev.K&H).
If they'd have any audible or measurable cavity resonances that would surely be not the case, after all recording engineers are practically the only people who regularly have the chance to compare what comes out of the speakers with the real thing.
some of them on T
and some of them on R
'T', yes, but the couple of 'R's I've auditioned were screeching piles, so which models are 'up to par'?
GM
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