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Multi-Way Conventional loudspeakers with crossovers

The umpteenth large format coaxial driver thread
The umpteenth large format coaxial driver thread
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Old 7th July 2015, 02:16 PM   #11
Adolf Corkscrew is offline Adolf Corkscrew  Finland
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Quote:
Originally Posted by ScottG View Post
It's a bad compulsion.

Done this way you are wasting a lot of efficiency on baffle-step compensation. (..unless it's being done "in-wall".)
Not necessarily. I'm not looking for a straight freefield response down to the lowest notes, since in a real room that would translate maybe to a 10-15dB too much bass... Then you'd need a DSP to counter that. A gentle roll off from maybe 120-150Hz should be preferable.

And yes, that trick does work, and is a surprisingly general solution, ie. done just right works in a wide variety of rooms and placement.

There's an example of what I'm looking for in AudioVideo.fi, a finnish internet publication, with an 18Sound 15-inch coax, and it worked very well in the bass department. Unfortunately it has a dip in its upper midrange response, which translates to an overarticulate sound, sometimes very annoyingly so. Shame, that, since otherwise they were quite good.

I take it that no-one here has tried the aforementioned Beymas? A real world response graph would be nice, since I consider most datasheets to be mostly of entertainment value here... I've seen too many drivers with published responses having very little to do with reality.
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Old 7th July 2015, 02:43 PM   #12
Inductor is offline Inductor  Portugal
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(strange) they changed the specifications (T/S) for the driver and they kept the sensitivity in it @97dB when it's only 92 dB/2.83V/m or 94.0 dB/W/m

I noticed new: Fs, VAS, Qts, Xmax (in what were maybe prototypes and early specs?!)

Maybe between the 8 Ohm vs. 16 Ohm versions only. (sorry)
http://www.faitalpro.com/products/fi...tasheet_16.pdf
http://www.faitalpro.com/products/fi...atasheet_8.pdf

The sensitivity case stands anyway.
FaitalPRO 12FH500 08: 95.2 dB/W/m - 97.2 dB/2.83V/m (2*Pi)
FaitalPRO 12FH500 16: 94.0 dB/W/m - 91.9 dB/2.83V/m (2*Pi)

Last edited by Inductor; 7th July 2015 at 02:57 PM. Reason: 8 Ohm vs. 16 Ohm
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Old 7th July 2015, 04:45 PM   #13
Adolf Corkscrew is offline Adolf Corkscrew  Finland
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Okay, so I've spent the afternoon doing some research on a couple of possible drivers and have done some basic WinISD simulations on their low end response in a cabinet.

First I ruled out the BMS 15C362. There seems to be no "solution" for it making deep enough bass with a simple passive crossover in a BR box. Shame, since I really like those BMS ring diaphragm HF drivers.

So this leaves two: the Beyma 15XA38Nd and the B&C 15CX40. Out of these two it seems that the B&C should go a little lower, but the Beyma doesn't look that bad either.

But then there's one black horse in the race: Oberton's 15CX. Might work, but I've never heard nor seen any of their products.

So, any first hand experience on any of these drivers would be most welcome.
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Old 7th July 2015, 07:47 PM   #14
Draki is offline Draki  Macedonia
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Here they use Beyma 15XA38Nd:
Sweden's No Frills Audio Introduces The Caveman Loudspeaker | Ultra High-End Audio and Home Theater Review
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Old 7th July 2015, 08:35 PM   #15
Adolf Corkscrew is offline Adolf Corkscrew  Finland
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Yeah, I found that too. Can't be all crap if it's been featured at a high end show, right? But sadly they show no FR measurements. I don't mean to say that frequency response is the only measurement of a driver, but that graph would greatly help to get a glimpse of its real world performance. As stated, I don't really trust manufacturers datasheets on this. Sometimes the actual performance is better (some BMS drivers), some times far worse (CSS FR125 comes to mind).

The more I've dug into this stuff, the more compelled I feel to take the dive and just get a pair of those Beymas. Teamaudio.fr sells them at a reasonable price (something like 370). But then again, those Obertons don't look all that bad, and are more reasonably priced. It's a shame I don't have the available dough to just purchase several pairs to compare them.
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Old 7th July 2015, 10:28 PM   #16
ScottG is offline ScottG  United States
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Quote:
Originally Posted by Adolf Corkscrew View Post
Not necessarily. I'm not looking for a straight freefield response down to the lowest notes,
Yes, necessarily.


Baffle-step compensation isn't a room boundary condition, rather it's the natural rate of pressure loss from the baffle as a bounding element.

Try using the Edge to see what sort of results you'll get:

Tolvan Data


Depending on the freq. and how well coupled to the floor the loudspeaker is, you can sometimes net some gain below 200.

IF you make the baffle really large you can compensate down to about 100 Hz.

IF you use a bass-reflex at a higher freq. in a suitable box for the driver then you can get a near-flat in-room response down to 50 Hz or so practically with that larger baffle.

It can be done, but it's going to be large, and it will require some significant design choices.
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Old 7th July 2015, 11:16 PM   #17
ScottG is offline ScottG  United States
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Quote:
Originally Posted by Inductor View Post
(strange) they changed the specifications (T/S) for the driver and they kept the sensitivity in it @97dB when it's only 92 dB/2.83V/m or 94.0 dB/W/m

I noticed new: Fs, VAS, Qts, Xmax (in what were maybe prototypes and early specs?!)

Maybe between the 8 Ohm vs. 16 Ohm versions only. (sorry)
http://www.faitalpro.com/products/fi...tasheet_16.pdf
http://www.faitalpro.com/products/fi...atasheet_8.pdf

The sensitivity case stands anyway.
FaitalPRO 12FH500 08: 95.2 dB/W/m - 97.2 dB/2.83V/m (2*Pi)
FaitalPRO 12FH500 16: 94.0 dB/W/m - 91.9 dB/2.83V/m (2*Pi)



I go by what's on the graph and the measurement conditions. Sensitivity is a 1-watt/1-meter proposition, not a specified voltage input and 1 meter (ie. voltage sensitivity).

To me it looks like a 96 db driver at 1 watt at 180 Hz ("infinite" baffle and volume). At 2.83 volts that should be 93 db at 1 meter.

Parallel them and your 2.83 volts should net 99 db at 180 Hz under the same condition.


..this of course depends on the output impedance of the amplifier.
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Last edited by ScottG; 7th July 2015 at 11:19 PM.
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Old 8th July 2015, 11:03 AM   #18
burgunder is offline burgunder  Denmark
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In a bassreflex you'll have some problems with cone excursion if you are using the Beyma 15XA38Nd.
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Old 8th July 2015, 11:50 AM   #19
Adolf Corkscrew is offline Adolf Corkscrew  Finland
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Originally Posted by burgunder View Post
In a bassreflex you'll have some problems with cone excursion if you are using the Beyma 15XA38Nd.
Hmm... Might be? But at what kind of levels? I'm going to drive these with a puny 8 watt single ended tube amp...

Good point, still. Even though at my usual listening levels even the cones of my current 12-inchers are barely moving. Still +-4mm xmax isn't that much...

Oberton's 15-inchers have +-7mm xmax. Or 7.75 on the neodymium version. They might be worth the try, and a quickie sim with WinISD shows that at least the ferrite version would be quite at home in a modest 100L enclosure.
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Old 8th July 2015, 12:14 PM   #20
burgunder is offline burgunder  Denmark
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In WinISD it will only take 3w to excede xmax at 10hz, 25w at 30hz. That is if im able to use the correct numbers etc.
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