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Old 13th September 2012, 03:59 AM   #11
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Originally Posted by audiothings View Post
RockLeeEV - thank you - that BMS does look interesting... but it has a QTS of .18 - will it work in a sealed enclosure? Any pointers to builds using this driver...
If you won't be using a woofer, you will want to actively EQ it flat to ~100hz as the F3 is only 200-240hz in a sealed box. No real problem with this though. QTS would only be a limiting factor if the driver's xmax or thermal management couldn't handle an octave of linkwitz transform. or you were using passive crossovers. You could probably step up to the 15 inch BMS, but I don't know how low the BMS tweeter will play.

THe only build I know of that uses this coax - and it may be the 12C262 actually - is the Soundfield Audio 1812

Last edited by RockLeeEV; 13th September 2012 at 04:02 AM.
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Old 13th September 2012, 06:08 AM   #12
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As an aside, the Beyma 12CX30 is an older model, not in the current line-up.
The more recent 12CXA400nd may be interesting instead (I have not experience with it though).

http://profesional.beyma.com/ingles/pdf/12CXA400Nd.pdf
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Old 13th September 2012, 03:23 PM   #13
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Audiothings

If you are on low budget why not consider Eminence Beta 12CX coaxials. You have some model calculations for enclosures on Eminence site. BMS and B&C are much more expensive.
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Old 13th September 2012, 04:27 PM   #14
kec is offline kec  United States
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Originally Posted by ivanlukic View Post
Audiothings

If you are on low budget why not consider Eminence Beta 12CX coaxials. You have some model calculations for enclosures on Eminence site. BMS and B&C are much more expensive.
Anyone ever had good results with the 12CX?
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Old 13th September 2012, 08:54 PM   #15
jwmbro is offline jwmbro  United States
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Quote:
Originally Posted by ivanlukic View Post
Audiothings

If you are on low budget why not consider Eminence Beta 12CX coaxials. You have some model calculations for enclosures on Eminence site. BMS and B&C are much more expensive.
Hi, as far as I know the Eminence drivers do not include a compression driver, these must be purchased separately. Is this correct? Because in that case, the Eminence Beta 8CX, which costs 80€ here, still needs an additional 60€ or more compression driver, which puts it very close to the price of the 161€ B&C 8CX21. Local prices may of course vary.

The B&C 8CX21 by my simulation will do an xmax limited 120dB down to 80Hz flat in a 12 liter vented box - this is very impressive for about 220€ in drivers and crossover.

Too small for OP with his 12"+ requirement, but a good driver nonetheless, even more so with Tom Danley's seal of approval.

Edit: 110dB @ 100Hz in a sealed box, xmax limited.
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Last edited by jwmbro; 13th September 2012 at 08:56 PM.
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Old 14th September 2012, 02:09 AM   #16
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Thanks everybody for the inputs.

May I request the educated and experienced to take a look at the Radian 512/2B please. It has some of the things I am looking for - high Qts, low Fs, apparently smooth FR (who knows what is happening off axis )

Couple of things are scary... they keep saying that it is a "ceiling speaker"... I don't know wtf this translates to, other than that it should work well in an infinite baffle installation, which is what we have on the cards. Usspeaker says tha the recommended crossover is @ 1.25 Khz while Radian's page recommends 1.5 KHz... I definitely want to crossover as low as I can... I am going to mail Radian, but I'm not sure what exactly I should be asking them... Any assistance is welcome...

Also, the horn loading results in a 90 degree "conical" dispersion... Did the Tannoy DMT15 have a conical dispersion characteristic? I remember somebody saying that it was "axisymmetric". God help me or strike me down. This is geting too confusing...

Last edited by audiothings; 14th September 2012 at 02:21 AM.
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Old 14th September 2012, 05:23 AM   #17
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B&C 8CX21, with it's Fs=74Hz, is just to small for the purposes that Audiothings have in mind.
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Old 14th September 2012, 11:16 AM   #18
sangram is offline sangram  India
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Note that in the "High End OB speaker" you refer to, extensive work has been done to get the response to sum flat at listening position and even then it is a little scary. High fidelity systems may not be the best base template for studio monitoring systems.

The 12" Beyma also has a very low Qts and some low end problems (I'm unsure to the exact nature of the problem, so treat it as heresy) which prevents its use on OBs - hence its availability only in the version with dedicated woofers. I suspect you may have issues in small sealed cabinets as well. My designs with the 15" versions of the same speakers pointed to a largish sealed box, with bass helpers running all the way to 100 -120Hz.

There are some major problems with coaxial speakers pointed out in the thread linked in the post and crossovers are an issue. However, for ultra-nearfield listening they are still a great option. A DEQx system would be a wise investment so you can take a lot of the guesswork out of the setup. I would prioritise the purchase of the front end before you get the actual drivers in place.

I would go for either the 12XA or 12CXA from the Beyma range, with the caveat that with the use case you have presented you will have to cross really low ~800Hz. Though the compression driver can handle it, power handling will suffer quite a bit (assume 50% of the rated 90W/1KHz power) though even that should be enough output for a 17x10 heavily treated room.

The 12XA cost around 50k a pair (CXA probably more), the Eminence with a good compression driver will cost half that. IME for translating mixes and overall performance, you will be equally able to work with either, as the Beyma has an edge mostly in power handling and bass distortion, and it doesn't look to me that either of those are going to be significant issues in your application.
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Old 14th September 2012, 01:00 PM   #19
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Thank you Sangram.

The Eminence is looking interesting! Their pricing is very friendly... Can I screw in a BMS 4550 to the Eminence Driver? This CD can be crossed over as low as 800 Hz... I notice that the 4550 has nothing that can screw on to the Eminence... is there some standard adaptor for this kind of thing...?

I am little wary of the Beyma 12XA because of the 2" diaphragm... I am told that HF response suffers as the diaphragm size gets bigger...

Still hoping somebody will chime in on the Radian... from where I'm looking, it seems to be the optimal driver for my requirement...

Last edited by audiothings; 14th September 2012 at 01:04 PM.
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Old 14th September 2012, 02:50 PM   #20
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Eminence PSD 2002S ("S" being "screw" version of PSD 2002) can be screwed directly to Beta 12 CX (and Beta 15CX). May be that it is possible to use Eminence APT3 adapter to screw other comp. drivers to Beta.

You will not have significant loss of HF with big diaphragms as frequency response of compression drivers depend mostly on diameter of throat (not diaphragm).
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