A New Cabinet for the Alpair 10.2 - diyAudio
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Old 31st December 2011, 10:10 PM   #1
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Location: Hot Spring Village AR
Default A New Cabinet for the Alpair 10.2

I have been working on an MLTL cabinet for the Alpair 10.2 Here is the result. The first picture is my new M10-A10. The second picture is the M10-A10 next to the Pensil 10.2, both in raw plywood. The FR plot is a comparison of the performance of two cabinets. A bit of explanation:

Because I donít have access to an anechoic chamber, the bottom ends of the graphs are created by combining the driver and port nearfield responses. The top end is a gated 1/2m response. I am now thinking that I spiced the plots slightly wrong and the actual bass response of both cabinets is probably ~2dB less than indicated here. The M10-A10 is the black trace, the Pensil 10.2 is the red trace. The green trace is a crude representation of the published Alpair 10.2 response.

The M10-A10 and the Pensil 10.2 perform pretty much the same, other than the unbraced sides of the Pensil produce enough noise to screw up imaging. (This was a short cut that I took to get the boxes together quickly Ė I had them running in two days. I will probably run some dowels through the sides and veneer them for sale sometime in the future.) So why do a new design? It is a matter of design philosophy. I suspect that Scottís design was driven by ultimate ease of construction. The cabinet is highly resonant and uses a LOT of stuffing to produce a reasonable output. My approach uses all of the tools to reduce all resonances except the fundamental with a minimum of stuffing Ė the cabinet is lined with fiberglass but uses no stuffing per se. The result is a cabinet that is somewhat taller and much less bulky.

The end result of either approach is a very fine sounding speaker. Which is better? Well, if you are asking meÖ.
Attached Images
File Type: jpg M10-A10.jpg (81.8 KB, 937 views)
File Type: jpg Pensil-M10A10.jpg (81.9 KB, 888 views)
File Type: jpg Pensil-M10-A10 Comparison.jpg (83.5 KB, 884 views)
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Old 1st January 2012, 12:01 AM   #2
jimbro is offline jimbro  United States
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Very nice looking speaker Bob. Good work as usual. I'd like to hear your impressions of the 10.2 vs 7.3.
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Old 1st January 2012, 06:18 AM   #3
zman01 is offline zman01  Bangladesh
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Happy New Year Bob!

Those are handsome looking speakers (as usual from you!). Is the supra baffle a must or that is mainly an aesthetic function?

Some listening impressions on different genres and in comparison to your A 7.3 and TB W8 design would be welcome.

-Zia

p.s. OT - Maybe too early to ask, but would you be designing a cab for the upcoming Alp 12.3?

Last edited by zman01; 1st January 2012 at 06:22 AM.
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Old 1st January 2012, 09:50 AM   #4
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Hello Bob,
Happy New Year!
Very interesting project. Wish I could be with you listening to these speakers.

I've PhotoShoped your pic to help focus on its design and look using both grey and gold drivers.

Cheers
Mark.
Attached Images
File Type: jpg M10-A10.jpg (24.6 KB, 839 views)
File Type: jpg M10-A10-G.jpg (24.7 KB, 818 views)

Last edited by markaudio; 1st January 2012 at 09:56 AM.
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Old 1st January 2012, 11:03 PM   #5
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Interesting, Mark. The gold driver does look good against the dark wood. Of course, assuming that I can sell some of these, Iíll use whatever the customer wants!

The veneer I used will not be repeated. It is beech, which I had from a customer who changed his mind about veneers. I donít particularly like the broad and prominent grain. On top of that, it blotched somewhat when I applied the stain. If I need a dark brown wood, Iíll use either natural walnut or teak.

I redid the FR chart for the M10-A10. Here is the result:

Graph 1:
Gray=ungated 1/2m.
Black=combined nearfield + gated 1/2m.
Red=10*.
Blue=15*.
Green=20*.

Graph 2:
Gray=ungated 1/2m.
Black=combined nearfield + gated 1/2m.
Red=15*.
Blue=30*.
Green=45*.
Brown=60*

Graph 3:
Impedance.
Bob
Attached Images
File Type: jpg Low_Angles.jpg (83.9 KB, 300 views)
File Type: jpg High_Angle.jpg (84.7 KB, 185 views)
File Type: jpg Impedance.jpg (80.9 KB, 142 views)
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Old 3rd January 2012, 01:15 AM   #6
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Nice work Bob! Ive run both gen.1 and 2 with good results, no doubt you have rung the last drop of bass performance from these great drivers! Will you be offering plans for these on your site, if so I'll be waiting in line for my set!

Larry
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Old 3rd January 2012, 03:33 AM   #7
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Quote:
Originally Posted by larryldspkr View Post
Nice work Bob! Ive run both gen.1 and 2 with good results, no doubt you have rung the last drop of bass performance from these great drivers! Will you be offering plans for these on your site, if so I'll be waiting in line for my set!

Larry
Thanks, Larry. Bass is very good, but these speakers may need a bit of BSC. I suppose it depends on how close to the wall you have them, but @3', I wind up with some 3dB of bass boost. I use DSP for my EQ, so it is not an issue. I may have to add a BSC filter for those who can't/won't to digital EQ.

I have the plans available now, but the new page will not be on the web site for a few days. PM me.

Bob
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Old 3rd January 2012, 03:55 AM   #8
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Quote:
Originally Posted by zman01 View Post
Happy New Year Bob!

Those are handsome looking speakers (as usual from you!). Is the supra baffle a must or that is mainly an aesthetic function?
Well, sort of both. With the 3/4" round-over on the supra baffle added to the 3/4" round-over on the main cabinet, you get an effective 1 1/2" round-over. Theoretically, this is good. Whether you can hear it is another matter. The supra baffle is attached with double-sided foam tape. This forms a constrained layer sandwich. Theoretically, this reduces vibration transfer from the driver to the cabinet. Again, whether you can here it.... Finally, the black oval is my signature. I am sure you can hear that!!

Quote:
Some listening impressions on different genres and in comparison to your A 7.3 and TB W8 design would be welcome.
Each of these drivers present an entirely different challenge. The 7.3 is definitely a mid/tweet. My T7-A7 is turned to 45Hz and the F3 is near 50Hz. It can be EQ'd to do much deeper bass, but this is not a good idea if you intend to run much rock through them. The M10-A10 is tuned to 38Hz and the F3 is near 40Hz. If you can keep the SLP below 85dB at 8', then you can play just about anything. Remember that the max excursion is going to be at ~80Hz -- right where the kick drum slap will be. BTW, I brickwall high pass these at 30Hz. The TB W8-1772 is an 8" driver with fair excursion. It has lots of guts and with care, might be used as (small) party speakers. As you go up is size, you trade finesse for guts. It you are going to use a sub or do a FAST, then the 7.3 would be the choice, probably crossed at the floor bounce. For general polite listening, the 10.2. For stuff that requires guts, the TB.

-Zia

Quote:
p.s. OT - Maybe too early to ask, but would you be designing a cab for the upcoming Alp 12.3?
I have not immediate plans for the 12.3. However, if you would like to have a pair delivered to me, I might see what can be done.

Bob
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Old 3rd January 2012, 06:40 AM   #9
markre is offline markre  Finland
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Can you please tell a little bit more why the pensil is highly resonant and the M10-A10 not?
Nice build!
Mark
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Old 3rd January 2012, 06:48 AM   #10
chrisb is offline chrisb  Canada
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Bob, I think you might have misspelled the beech - even with a "natural" finish, not one of my favorites - now flat sliced/book matched black walnut is a different story

nice work on the MLTLs as always

C
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