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Old 14th April 2014, 01:23 PM   #1
Mordor is offline Mordor  Italy
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Default home cinema: eminence beta 8a & ??

hi i have some new beta 8a waiting for a project.

Unhappy about my home cinema sistem ( Cambridge audio tower , center, bookself for back + hk avr ) i m thinking to build 3 equal speakers for front.


I thinked 2 possible solution:

ribbon like fountek ( from 1500 2000 hz ) or a fullrange like dayton or fostex ( from 500 hz ) + beta 8 reflex

The problem is that i dont like how the beta 8 sound from 1500 2000 hz ( i love just for punch).
I need a solution to combine that can handle low freq and keep an high efficency ( 95 db of beta 8a ).... should i keep the beta 8 in their boxes ?
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Old 14th April 2014, 01:50 PM   #2
system7 is offline system7  United Kingdom
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So what have you got so far for this design? Crossover point, filter, box size and reflex tuning?

http://www.eminence.com/speakers/spe...?model=Beta_8A

All looks pretty straightforward to me, as it goes. Not that I like your tweeter choice at all.
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Last edited by system7; 14th April 2014 at 01:55 PM. Reason: Corrected Link
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Old 14th April 2014, 02:05 PM   #3
Mordor is offline Mordor  Italy
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first of all, i have 4 of this speaker, was for my car, but i grow up :P and i change car and ideas about.

So why not use 3 of this for build 3 equals speakers for my living room?
Many people dont like fountek ribbons and the dispersion is a little bit poor ( in a home cinema where people are widely sitted in sofa isnt so nice ); so i was thinking about fostex fullranges: with a reflex solution they can handle 200 500 hz without any problem, they can cover a wide range without any crossover and phase problem on the speakings frequencies, they have a nice efficency.... and last they are cheap... 40 50 euro each.
I can realize a bookself solution, with 2 different chambers... i was thinking to use also concrete and made a millled form ... and high tickness wood...

just many ideas... but i need tips

some throubles in my mind: different power size ( 8a can handle more than 200 w ), different style of sound....

p.s. sorry for my english

Last edited by Mordor; 14th April 2014 at 02:07 PM.
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Old 14th April 2014, 02:14 PM   #4
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What are you unhappy about with your current speakers? The Beta 8 are a PA driver and hence require a big box and don't get down that low. But they will go loud. So if more bass is what you are after they are not the right choice.
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Old 14th April 2014, 02:35 PM   #5
Mordor is offline Mordor  Italy
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the problems of my actual setups are mostly in the center: same series of tower but smaller in liters and in speakers size, poor bass definition, voices are not so defined.

Towers have the same problem of mid high ( same tweeters ) but low resp are ok, just ... undefined and confused. Globally the system definition is... low, the speakings are confused, the audio scene is not so clear and fresh, present... seem somewhere far behind a cover.... I dont need a very low freq from my center ( i have sub also ), but i need more a defined and fresh audio scene expecially with low volume...
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Old 14th April 2014, 03:56 PM   #6
system7 is offline system7  United Kingdom
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I really don't have time to design a FAST speaker from scratch.

But all is not lost with something more conventional. I knew I'd seen an Eminence Beta 8A in a commercial design. Tekton Design M-Lore:
Tekton Design Lore-M
Tekton Design M-Lore Loudspeaker Reviewed

An earlier version with a similar Eminence Alpha 8A below. It's enough to know it works well. The rest, as they say, is just technique.
Attached Images
File Type: jpg Tekton M-Lore.jpg (28.0 KB, 80 views)
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Old 14th April 2014, 04:41 PM   #7
Mordor is offline Mordor  Italy
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i thinked also a tweeter array like 2 XT25SC-90/04 VIFA 1 INCH TWEETER and do a more conventional solution
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Old 15th April 2014, 12:07 AM   #8
system7 is offline system7  United Kingdom
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Quote:
Originally Posted by Mordor View Post
i thinked also a tweeter array like 2 XT25SC-90/04 VIFA 1 INCH TWEETER and do a more conventional solution
That's not conventional at all. Aren't you going to take the impedance rather low?

It's actually not easy to do this. It's going to need a loud tweeter.

TQWT-
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Old 15th April 2014, 12:44 AM   #9
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First, take a look at this home-theater oriented design using the Beta 8a:
Fusion-8 Alchemy - Fusion Series - Waveguide Speaker Kits DIY Sound Group
19 liter reflex cabinet, good to 70 Hz or so (you'll want a sub or three), high efficiency horn tweeter crossed at 2500 Hz. Since you already have the Betas, you would have to see if Erich would provide just the waveguide, compression driver and crossover. The box design is available from the site.

The crossover point is higher than you would like, but it was done by a very respected designer, and I'm sure was chosen to help match the directivity of the tweeter to that of the Beta in the crossover range. The speaker has been very well received.

Or, you do as I did and could choose a different compression driver and waveguide and do it yourself. I'm using the Beta's with a Faital Pro HF100 / STH100 top end, and bi-amping with a MiniDSP. I designed a small MLTL enclosure using Martin King's worksheets (internal dimensions 8.5 in wide x 7.5 in deep x 30 in tall, 3" dia x 3" long port located 8" from the bottom, driver as high as possible in the box, horn sitting on top). The bass is pretty good to 60 Hz or so, I filter below 50 in the MiniDSP. Still playing with crossover configurations. If you need a passive crossover, I'm NOT the guy to turn to for help!

I'm fairly pleased so far, but I'm a novice at x-over design and a long way from done. At some point I'll upgrade to a MiniDSP 2 x 8 (or 4 x 10) and add some woofers to take over the bottom end, leaving the beta working from maybe 150 to 2000.

Bill
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Old 15th April 2014, 09:13 AM   #10
system7 is offline system7  United Kingdom
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That's very interesting, Bill. Jeff Bagby is a good designer and an occasional visitor here. But my sort of diyaudio is not really about building kits. What do you learn from that?

I wouldn't say his crossover is low at all though. With a more conventional tweeter, this whole thing is actually going to be easier with a higher 3.5kHz crossover point IMO.

The 20L reflex box is what I would expect from the Eminence data. These high efficiency speakers inevitably sacrifice bass extension, but in Europe we don't have living rooms the size of aircraft hangers, so not an issue really.

But I'm waiting for Mordor to come up with some filter and tweeter ideas. It's his idea and he's taking on the work and inevitable tweaking. FWIW, there are two filter approaches that I can see. Second order and third order. The high efficiency Troels TQWT- approach may be hard to implement with a regular sort of tweeter, which adds an interesting element of trial and error.

The Eminence Beta 8A is a mere 0.49 Le inductance and has quite a nice natural frequency response, so should sound good on small filter values. It's really the high tweeter efficiency requirement that is hardest here.
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