The umpteenth large format coaxial driver thread

Okay, I admit it. I'm stuck, and a search on this forum gave me no answer. I remember that large format coaxial drivers have been discussed here time after time, but apparently my search skills are subpar to say the least.

To cut things straight, what I want is a 15-inch PA coax driver capable of going nicely from at least 50Hz to 18kHz, and be able to do this with a passive crossover. Active crossovers, DSP:s and such are simply out of the question, since I would use the resultant loudspeaker system to evaluate amplifiers.

My current reference would be the BMS 12C362, which gives a lovely midrange and treble, but falls short at the bass department.

I've been looking at several drivers; BMS 15C362, B&C 15CX40 and Beyma 15XA38Nd to name a few. And what I've found out so far, is that the BMS isn't going to cut it down low, the B&C was declared "shouty" somewhere, and I've yet to find any complaints about the Beyma.

So, I would appreciate any input from anyone who has experience on this field. Where should I look? I just want a BR box, which doesn't sound boomy, and goes up from the lowest E of a bass guitar with real sense of force. Too much to ask? Oh, and I'd really appreciate it if it had at least most of the midrange resolution of the BMS 12C362...
 
Hmm... Maybe I should've stated that I wanted a current production driver that's easily obtainable... I understand that Tannoy drivers are near unobtainium these days?

edit: That GPA driver does look promising, though I've some perversion regarding that I'd like the bass/midrange cone acting as the horn for the tweeter. Still, I'll keep that in mind.
 
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Availability is a problem. I look to make something I can - if I succeed, which isn't a given - recommend to random people around me with the same problem.

The easy way out would've been - admittedly - a pair of Tannoy Monitor Golds in a suitable cabinet. But they're not current production.

Sorry if it seems like I'm moving the goalposts...
 
15" coaxials typically aren't as good as the 12's so adding something like twin 15's below the 12 and biamping may be better.

+1 for the Tannoy. What's better? :)

As I stated in the opening post, any active solution is out of the question, since I want to be able to evaluate amps with the result.

The Tannoys are admittedly very good. But sadly they're not available as current production.

One of my ideas is just extending the response of the BMS 12C362 with an 18-inch bass driver in a 3-way. But I'm more compelled to design a 2-way with some currently available 15-incher...
 
..But I'm more compelled to design a 2-way with some currently available 15-incher...

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".)

2.5-way MINIMUM to maintain good efficiency.

Best practice is to have your co-axial from about 450 Hz up, and 2 mid-bass drivers below it to minimize floor bounce.

For a coaxial I'd go with this driver:

PHL Audio 1520 (8Ohm)

http://www.bvcam.com.hk/up_bin/2009828101513384.pdf

-along with:

https://www.madisoundspeakerstore.com/horn-tweeters/fostex-d1405-compression-horn-driver/

..or a Radian 475, or even something as inexpensive as the larger 1" exit Celestion driver's.

..and,

-perhaps 2 of these wired in parallel:

FaitalPRO 12FH500 12" Neodymium Professional Woofer 16 Ohm

FaitalPRO | LF Loudspeakers | 12FH500



..and yeah, I know it's not large format..

IF you want large format then please pair with a good horn, not a coaxial.
 
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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.
 
(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/files/12FH500/16/12FH500_datasheet_16.pdf
http://www.faitalpro.com/products/files/12FH500/8/12FH500_datasheet_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)
 
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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.
 

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.
 
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.
 
(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/files/12FH500/16/12FH500_datasheet_16.pdf
http://www.faitalpro.com/products/files/12FH500/8/12FH500_datasheet_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)


:eek:

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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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.