Alpair 7 used for Keele CBT Array - diyAudio
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Old 2nd June 2012, 10:03 PM   #1
HiroPro is offline HiroPro  Canada
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Default Markaudio coaxials used for Don Keele CBT Array ?

I'm curious what opinions are for using the Alpair 7, 6 metal or paper models with a Keele CBT array?

I was considering the PE kit but these drivers have me interested in DIY plans.

The paper models would be very economical for this purpose.

Opinions?

If you haven't heard of this type of line array please checkout the following links.

Don Keele's CBT (Constant Beamwidth Transducer) Page

Audio Artistry / CBT Products

Don's keynote for PE kit.

Parts Express Part 1 - Don Keele's Keynote Speech on CBT Line Array Speakers - YouTube

These drivers seems like a NATURAL to me considering they are one of a HANDFUL of affordable coaxial fullrange drivers that produce decent SQ. Especially the paper models.

Here is the CBT MOTHER LOAD

http://www.xlrtechs.com/dbkeele.com/...0Download.html

Don has a CD just full of design ideas and technical info!

Isn't the 6P or CHP a natural for this at $50 or under a driver!

Last edited by HiroPro; 2nd June 2012 at 11:04 PM.
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Old 2nd June 2012, 10:20 PM   #2
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Interesting thought. I have a feeling that if it were possible...the box would be huge. I dont think the CBT's are ported?
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Old 2nd June 2012, 11:35 PM   #3
HiroPro is offline HiroPro  Canada
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Originally Posted by aptquark View Post
Interesting thought. I have a feeling that if it were possible...the box would be huge. I dont think the CBT's are ported?
Yeah I guess looking at the specs the cheaper 6p would be better. I hear mention of a driver called the EL70 that I can't see on Markaudio's website.
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Old 2nd June 2012, 11:50 PM   #4
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Quote:
Originally Posted by HiroPro View Post
I hear mention of a driver called the EL70 that I can't see on Markaudio's website.
That's because they were built for Bob @ CSS:

Creative Sound Solutions - Loudspeakers, Parts and DIY Speaker Kits

jeff
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Old 3rd June 2012, 12:26 AM   #5
HiroPro is offline HiroPro  Canada
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Originally Posted by vinylkid58 View Post
That's because they were built for Bob @ CSS:

Creative Sound Solutions - Loudspeakers, Parts and DIY Speaker Kits

jeff
WOW your the third BCer I've encountered online today!

And in Vic to boot!

Is there a DIY group/GtG/society in the Victoria area?

Curious what you think of Mark's drivers for a CBT.
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Old 3rd June 2012, 12:36 AM   #6
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Is there a DIY group/GtG/society in the Victoria area?
Big time! 9th Annual Vancouver Island diyFEST 2012

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Originally Posted by HiroPro View Post
Curious what you think of Mark's drivers for a CBT.
Not a clue.

jeff
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Old 3rd June 2012, 08:06 AM   #7
HiroPro is offline HiroPro  Canada
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Originally Posted by vinylkid58 View Post
Big time! 9th Annual Vancouver Island diyFEST 2012



Not a clue.

jeff
I didn't look at the Vas for the drivers... LOL

Yeah it would have to be one huge box!

I'm just a kit builder so I'm rather clueless on box design and even most speaker parameters. I guess the suspension is "loose" on those drivers ehh?

I'm also curious why I've never seen a ML-TL With multiple drivers...

Again I'm clueless on speaker design other than following premade designs and building them.

Is a CBT possible with a ML-TL using the main drivers?

I guess low Qts (Qms?) and low Vas would be important?
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Old 7th October 2015, 11:32 PM   #8
rajesh is offline rajesh  India
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I harbour similar thoughts and searched the forum and found this thread! Too bad it didn't materialise. Are there any threads which progressed to build stage?
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Old 8th October 2015, 11:17 AM   #9
xrk971 is online now xrk971  United States
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For line arrays, you want as close of a center-to-center (CTC) spacing as possible to reduce the effects of driver-to-driver comb interference into the longer wavelengths or lower frequencies. Typically smaller drivers like 2in to 3in full rangers are used. The A7.3 is a nominal 4in class driver but has the largest bezel or frame width of any 4in driver I know of, it approaches a 6in driver in some cases (huge). Additionally, it has a rather non-uniform frequency response and quite a bit of ringing in the 10k to 12k range as a result of resonance peaks that are used to extend the HF response. If you like the sound of aluminum drivers and you want to hit a true 20kHz look at smaller drivers. Lastly, the price of an A7.3 is quite high in general and as a line array where you need a lot of them, it can be prohibitive for some.

Take a look at the Fountek FR58EX ($18). It has a smoother response than the A7.3, has a very small frame that is rectangular which allows tight CTC spacing, excellent xmax, and it sounds very nice to my ears. It won't have the same bass capability as the A7.3. For that you could use the FR88EX ($38) which is less than half the price of the A7.3 and has a very durable cast aluminum frame vs the rather fragile plastic frame of the A7.3. I can't imagine having to run two dozen A7's for over 200hrs to break them in as recommended.

Other alternatives for line arrays include the Peerless P830986 ($22) which also has a square frame and is quite compact - great frequency extension up high. Smaller is the P830983 ($25) at 2in and there is the very nice cast frame NE65W ($33). All three have a flatter frequency response than the A7.3 and would probably make a better starting point for an array.

If I were building an array and I had to have aluminum drivers, I would go with the FR58EX - tight CTC, great sound with crisp highs, great price. If I did not have to have aluminum, I would go with Vifa TG9FD10-8 or TC9FD18-8. Also square frame for tight CTC spacing and a response that is smoother than ANY driver available, except maybe the ScanSpeak 10F.

Last edited by xrk971; 8th October 2015 at 11:22 AM.
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Old 11th March 2016, 11:25 AM   #10
rajesh is offline rajesh  India
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Thank you for deep insight Xrk971. That was very helpful.
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