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Old 12th September 2012, 12:02 PM   #1
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Default Help me pick a coaxial speaker ++

A couple of years, I had started on this project, bought a bunch of drivers... but it got put on hold... This time its for real... I am helping a friend set up his studio. Walls are being demolished as I type this, and the new walls will be completed to my specs in about a month. He has given me a free hand with the design of the studio and the monitoring system. The tentative layout of the studio is attached herewith. The space currently allocated for the flush mounted speakers is 20" width, 16" depth and height is to be decided, depending on which way the design heads.

I already have a pair of NOS Exodus Audio Tempest X15s to handle duties below 100 Hz. I will definitely use a 2x6 loudspeaker management system... the DEQX HDP Express II, if we can afford it... if not, we will resort to some Behringer DCX2496 type device, until finances permit us to upgrade to the DEQX.

Now, I want a 12"+ coaxial speaker to complete the driver complement. I want it to be coaxial for two reasons : 1. The engineer will be seated relatively close to the speakers, so the path length differences between sounds coming from the mid-woofer and HF driver can become a serious issue, if they are not dual concentric... and 2. I used to work with Tannoy DMT15s and I have never enjoyed working on any speaker more... just my personal experience/opinion.

The other requirement is that it should be able play loud... at least 110 dB continuously, with peaks of 120 dB+ (@ 1m)

The amps will most probably be QSC GX7 for the subs and its smaller siblings for the mid-woofer and HF driver.

So... help me pick a coaxial driver to take me forward with this design. Specifically, I would like a sealed enclosure for the mid-bass unit, which goes down to 100 Hz comfortably - and can produce the SPL I want, in the form factor I mentioned.

Top on my list at this time is the Beyma 12CX30, just because I happen to know that it is being used in a pretty high end OB speaker... I am also interested in the Radian 512/2B...

Thank you for any inputs, caveats, warnings etc...

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Old 12th September 2012, 12:57 PM   #2
Pano is offline Pano  United States
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Video editing/post production suite?
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Old 12th September 2012, 01:31 PM   #3
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Originally Posted by Pano View Post
Video editing/post production suite?

Audio recording and mix studio. The front wall will be hard - extending the baffle of the flush mounted speaker. The floor will be hard. Every other surface will be as completely absorbent as I can make it, with the usage of metal and membrane trapping and insulation. This is inspired by the Non Environment approach propagated by Tom Hidley / Philip Newell.
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Old 12th September 2012, 01:34 PM   #4
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Since you liked the Tannoys so much why not stick with them?

Like 12DMT or 15DMTs, would have to be second hand these days but they are completely serviceable via Lockwood Audio and others.

As for an eventual digital speaker management system (crossover to you and me) check out XTA.
Amp-wise I can wholeheartedly recommend MC2 Audio aka Quested Audio.
Quested also do speaker management which are re-badged XTA units.
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Old 12th September 2012, 01:40 PM   #5
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No matter which coax you choose, the crossover is tough to do. It's going to take some time and effort to get right. Once you do, you'll know it.
Have a look at this:
Why aren't coaxial speakers more popular?
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Old 12th September 2012, 03:09 PM   #6
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www.ciare.com/pdf/catalogo/HX255.PDF
Also available the 8" and the 6.5"
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Old 12th September 2012, 07:03 PM   #7
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picowallspeaker, that Ciare does look good. Low Fs, high Qts, and possibly more uniform dispersion between the mid-woofer and the HF driver, thanks to the 10" mid-woofer, which is smaller than the models I had in mind... It is now on my list of considerations, thank you.

Quote:
Since you liked the Tannoys so much why not stick with them?

Like 12DMT or 15DMTs, would have to be second hand these days but they are completely serviceable via Lockwood Audio and others.
Thanks Charles... I am in India, and this is a scary thought... third world as we are, I was surprised to see that most companies I see in usspeaker.com are represented in India... Replacement, servicing etc., are accessible. I simply cannot trust our local freelance technicians to take on something like this...

Quote:
As for an eventual digital speaker management system (crossover to you and me) check out XTA.
Amp-wise I can wholeheartedly recommend MC2 Audio aka Quested Audio.
Quested also do speaker management which are re-badged XTA units.
Cost is a factor. XTA/Quested is going to be way more $ than Behringer, if that is the space I'm playing in. If I'm going to invest more, I want a smart guy in the house, as I'm not very bright myself... I imagine that the DEQX is that guy...
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Old 12th September 2012, 07:28 PM   #8
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BMS 12C362, crossed around 900hz to 1.2khz 3rd to 6th order.

Last edited by RockLeeEV; 12th September 2012 at 07:47 PM.
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Old 12th September 2012, 07:55 PM   #9
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Fwiw, At the time I did the comparative measurements of the available driver choices, the B&C 8CX21 had the smallest acoustic / horn discontinuity between the cone and compression driver portion.

It ended up being used in a number of our products and the front to back spacing allowed a Synergy style crossover (which doesn’t have the traditional “all-pass” phase shift and step in Group delay) so that the cone and hf can occupy the same location in time.
Most coax drivers do not sum into one source even though they appear to be just that visually
Best,
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Danley Sound Labs
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Old 13th September 2012, 02:47 AM   #10
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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...

Mr. Danley - honoured to have you on board. Everyone says that a smaller mid-woofer - 5" - 8" has the best mid-range clarity and dispersion - and integrates better with the HF driver. I have no doubt that this is true. I'm coming from a different place, and I hope my explanation makes sense.

I am a sound engineer... I record and mix music for a living. Like many engineers of my generation, I am self taught, and can easily be confounded by technology. Anyway - every time I take a track I have done a stereo mix on to a film mix stage, I hear things in the low end, that I never heard in my studio. I imagined that it was the acoustics in my small room that was leading to muddiness and lack of clarity in the bass. Over the years, I have had several sets of standard studio nearfields with competent subwoofers, and the low end has consistently been a problem. Last year, I built a pair of Econowaves (RIP Zilch) with 12" Dayton woofers, in huge 170L cabinets - and whoa! there it was, the missing clarity in the bass! I was hearing the low end like I was hearing it in the film mix stages... So I have concluded that for me to hear 100 Hz - 400 Hz the way I want to, I need it to come from a large driver in a large box. A three way, with crossover points @ around 400 Hz and 3 Khz, with a 5" midrange would appear to make sense, but then again, in this room, the listener is too close to the speaker for this to be an optimal choice...

In this case, there will be a pair of nearfield monitors, on which, in fact, most of the mixing will happen. The big monitors will come on when the engineer is checking the low end, or blasting it, to impress a client.

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Most coax drivers do not sum into one source even though they appear to be just that visually
This is exactly the kind of thing that destroys my innocence. Knowing that I don't know enough, but not knowing what I don't know
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