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Multi-Way Conventional loudspeakers with crossovers

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Old 5th October 2007, 12:17 AM   #2331
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Quote:
Originally posted by Russell Dawkins
Apparently Emerald Physics will be at RMAF, I presume with their CS1. That should be interesting as it is possibly the closest on the market to the configuration you are contemplating.
IMHO, Emerald Physics had the best sounding speaker at CES this year.
I spent the end of 2006 building a Unity clone - I'm thinking about spending this winter building something like the Emerald Physics.

If anyone is interested in seeing me do this, let me know. The last thing I need is another set of speakers, but I'd love to collaborate with you guys on a speaker PROJECT. It's a lot more fun with you guys egging me on

Here's what I posted about the speakers a few months back:

http://www.diyaudio.com/forums/showthread/t-104441.html
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Old 5th October 2007, 02:34 AM   #2332
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Originally posted by john k...


In an ideal inhomogeneous cone they would not appear unless some destabilizing factor was introduced.
Just a correction. For some reason I couldn't edit the original post. This should have read, "In an ideal homogeneous cone they would not appear unless some destabilizing factor was introduced. "
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Old 5th October 2007, 06:05 AM   #2333
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Don't mind me, I'm having fun following this thread.

Peeking over at the EnABL thread, it has occurred to me that maybe the subjective increase in resolution is correlated with a drop in distortion at frequencies in the breakup region.

The strong love/hate reactions to Lowther and Fostex drivers has everything to do with their quite pronounced breakup/resonance regions, which are much less "damped" and smoothed-out than more conventional, better-measuring drivers. I've never been a fan of Fostex drivers, but I've been surprised by Lowthers several times - they almost remind me of the fabled Decca cartridge in temperament, sometimes wonderful, other times, not nice at all. When they go sour, they go very sour indeed, typically with choral music at high levels. But when they're good, even the electrostat-lovers (like me) have to grudgingly admit there's something pretty special going on.

If the EnABL treatment does little to decrease to the magnitude of the peaking, but reduces the distortion at those frequencies, I'd expect a change in sound character, and possibly, the increase in headroom the auditioners are reporting. More comprehensive measurements are definitely needed. Just changing the good/bad ratio of the Lowthers and Fostexes would be an astounding achievement.

P.S. After all this buildup, yes, of course I want to listen for myself. Only a few more days ...
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Old 5th October 2007, 08:43 AM   #2334
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Quote:
Originally posted by Lynn Olson
Don't mind me, I'm having fun following this thread.

The strong love/hate reactions to Lowther and Fostex drivers has everything to do with their quite pronounced breakup/resonance regions
(...)
When they go sour, they go very sour indeed, typically with choral music at high levels.

choral music even not at so high levels (in my experience)
and not only choral music, also strings, especially in case of bright baroque strings orchestra
in those cases the main break-up resonance of Fostex FE206E (I am testing one) which is easily heard on pink noise as whistling goes beyond whistling into the ear-and-brain-piercing howling

simply unlistenable

the main resonance is somewhere between 2500-3000 Hz
1/10 octave notch filter centered at 2700 Hz is cutting out most of it

does anybody know how to fix it completely?
did anybody do any measurements of effects of cone doping in case of FE206E and similar drivers?

best,
graaf
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Old 5th October 2007, 06:02 PM   #2335
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Quote:
Originally posted by graaf
Fostex FE206E (I am testing one) which is easily heard on pink noise as whistling goes beyond whistling into the ear-and-brain-piercing howling

simply unlistenable

does anybody know how to fix it completely?
I consider the stock Fostex drivers as raw material -- at this point the only one i can listen to stock is the FE108e∑ (granted i haven't worked my way thru all of them yet)

Most people use the 8" Fostex as exemplers... but the smaller drivers (4-5") are their best drivers overall.

I am working on taming the big ones -- phase plugs are a start -- but i seriously doubt it is possible for them to ever have the midrange magic of the smaller ones.

dave
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Old 6th October 2007, 10:33 PM   #2336
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Hello Lynn,

Don't know if you'd have the time or interest, but just in case...

I will be displaying speakers at RMAF that use a waveguide-loaded compression driver and the TAD 10" alnico magnet woofer in what might be called a Geddes-esque configuration (no refractive foam, though). I'm among those who place radiation pattern very high up on the list of things to get right. The room number is 1100, in the tower. My room has a little alcove where you can take a breather and prop your leg up.

My brother-in-law, who lives outside of Nederlands, has a pair of Aerials in his living room to this day. That's a design that has certainly stood the test of time.

What's you present plan for crossover and/or equalization for your Beyond project?

Thanks,

Duke
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Old 6th October 2007, 11:07 PM   #2337
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Quote:
Originally posted by audiokinesis
I will be displaying speakers at RMAF that use a waveguide-loaded compression driver and the TAD 10" alnico magnet woofer in what might be called a Geddes-esque configuration (no refractive foam, though). I'm among those who place radiation pattern very high up on the list of things to get right.
I've seen your Jazz speakers mentioned over at AA HiEff. Pity I'm on another continent as I'd be curous to hear them. If it's not a trade secret, which HF driver do you employ? I'm guessing 4552.
Cheers
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Old 7th October 2007, 03:15 AM   #2338
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Quote:
Originally posted by audiokinesis
Hello Lynn,

Don't know if you'd have the time or interest, but just in case...

I will be displaying speakers at RMAF that use a waveguide-loaded compression driver and the TAD 10" alnico magnet woofer in what might be called a Geddes-esque configuration (no refractive foam, though). I'm among those who place radiation pattern very high up on the list of things to get right. The room number is 1100, in the tower. My room has a little alcove where you can take a breather and prop your leg up.

My brother-in-law, who lives outside of Nederlands, has a pair of Aerials in his living room to this day. That's a design that has certainly stood the test of time.

What's you present plan for crossover and/or equalization for your Beyond project?

Thanks,

Duke
Many thanks for the invite, yes, I'll be there. I plan to do a lot of resting, and not carry any bags of literature this time. Stopping-off points with good music are always welcome.

Let's see, that makes Lowther, Bastanis, Emerald Physics and now Audio Kinesis. John Atwood (of Vacuum Tube Valley and Artemis phono preamp fame) will be staying at my place about 25 miles north of the show venue, so you may see the two of us showing up at the same time - or not, depending on what he plans to see.

I was reading the Dr. Geddes thread and noted the 20-element crossover. For those of you who are new at this, a 20-element crossover for a 2-way speaker is an extraordinarily sophisticated crossover, far, far beyond the abilities of anyone trying to "clone" a speaker.

The usual parts count is - let's see, 3 elements for the woofer lowpass, 2 for the inductance corrector, maybe another 3 for a midrange notch filter. A typical highpass would have 3 parts for the filter, 2 for a shelf filter, 2 for inductance compensation, maybe another 3 for a notch filter somewhere. That's still only 18 parts total - well OK, add a couple of resistors here and there for phase-shaping, and that gets to 20.

In reality, I'm sure the actual topology is a non-obvious computer-modelled network, designed, as Dr. Geddes has said, for uniform and well-corrected polar response over the intended coverage angle. I think the folks who want to "clone" the Summa or ESP15 are going to find it very difficult, even with the same drivers and HF waveguide.

As for the new system in this thread, I plan to keep it as simple as I can get away with. The Ariel used the flattest drivers I could find, and the best-sounding version still has a minimum of 7 parts, 10 if you want to be nice to the amplifier. I don't think the new system will be any simpler - I haven't found any drivers as flat as the 5.5" Vifa and the original sticky-dome 9000-series Scan-Speak.

The RAAL ribbon should be simple enough to highpass filter, but I have no idea what the 8 or 12-inch midbass is going to require - that's the hard part, since that's where the phase-shaping that controls the polar pattern is going to be happening, and the requirements for smooth out-of-band performance are most severe.

(Note: this changes if a compression driver + waveguide tweeter is chosen - simplicity goes out the window then, and quite substantial in-band HF EQ, with associated complexity, is required. I think I saw a max figure of 16 dB of subtractive EQ in the other thread - that's a lot, folks.)

As mentioned before, the only true crossover is between the tweeter and midbass, and the starting point will be low-Q 2nd-order filters. It's entirely possible neither the RAAL nor the midbass will tolerate filters with such a gentle shape, so at that point I'll be evaluating sharper crossovers vs alternative drivers. Dunno 'til I get there. I don't like the sound of high-Q crossovers, but the sound of driver coloration, and poorly controlled phase relationships between drivers, is even worse. So there's some tradeoffs here.

The bass-augmentation drivers will have their own amplification, active lowpass filtering, and room/driver equalization. The starting point for the topology are 1st-order lowpass filters chosen to complement the dipole/quasi-cardioid rolloff, followed by steeper filters starting near 1 kHz to remove the augmentation drivers from the midrange crossover region (and keep the vertical polar pattern from getting too complicated). All lowpass functions will be low-Q non-overshooting filters, Bessel family et al.

I have no intention of "forcing" the dipole/quasi-cardioid augmentation drivers to act as subwoofers, and will have a separate monopole subwoofer. I have an existing REL Strata II that can be pressed into service to evaluate the overall balance of the system.
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Old 7th October 2007, 04:32 AM   #2339
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Hi Brett,

The driver I use isn't a trade secret... but the crossover is.

The driver is the Beyma CP-385/Nd, mounted to the DDS ENG 1-90 waveguide (which is back in production).

Duke
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Old 7th October 2007, 04:39 AM   #2340
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Quote:
Originally posted by audiokinesis
Hi Brett,

The driver I use isn't a trade secret... but the crossover is.

The driver is the Beyma CP-385/Nd, mounted to the DDS ENG 1-90 waveguide (which is back in production).

Duke
Thanks. If the 385 is as nice/nicer as the 380 it's a very fine driver.
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