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Alpair 7P & Alpair 12PW combination.

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mikejennens

mikejennens

Member
Joined 2008
Bob Brines said:
The A7P and the A12PW sure look like candidates for as 1st order series XO. Pretty much pick your XO point anywhere for ~200Hz to 5kHz. IMO best choices seem to be at the baffle step, which the A12PW looks to take care of on its own, or 3-5kHz where the A12PW starts to go away. The problem with the high XO is going to be dispersion (maybe, since we don't have off-axis plots yet). The problem with the low XO is it wastes the bulk of the range of a very smooth midrange driver.

So, back to IMO. The A12PW looks to me to be a super choice for a wide range mid in a 3-way with a real woofer below, say, 100-150Hz and a real tweeter in a wave guide above 5kHz or so. The A7P is pretty much a drop-in for the A7.3. You get the difference in sound of the two cone materials, which I won't be able to comment on for 2-3 months after Madisound sends me the drivers.

Here's my logic on not using the A12PW in a FAST implementation. Chest thumping takes 85dB @ 80Hz at the listening chair. I have discovered this by experimentation. Any less volume, no thump. Now Mark has been very straight forward advertising the A12PW as a light weight driver. It's not going to survive as the bottom end driver at a frat party. So I will be crossing my FAST to a pair of 12" heavy duty woofers. Those of you who know my listening habits know I would never spend any time listening at over 75dB average for any time, but demos are demos and shows are shows. (BTW, young'ns, if you are listening at chest-thumping levels, you are destroying your ears. I am 70 years old. I never listened to rock and high levers or whet to concerts and I can still hear above 12kHz. You will never get that chance.)

The A7P will go straight into my little folded TL. I never did a BR for the A7.3, and I have no interest in something like that. I do think that the A7P might do well in a small stand mounted BVR with F10 around 50Hz or so. I might give that a try.

Bob
Click to expand...

Can anyone suggest a woofer that would offer the "chest thump" and work well in place of the 12PW for this combination? Bob mentions a pair of 12 inch woofers, but no specifics. I was thinking of the Dayton RS-225 (I know, it's a 10 inch, but it's a starting point...), but I don't know what the crossover would need to be.
Unfortunately, I don't have the design acumen of many of you, so I have come to depend on your generous sharing to build my speakers.
Thanks,
Mike
 
mikejennens

mikejennens

Member
Joined 2008
mikejennens said:
Can anyone suggest a woofer that would offer the "chest thump" and work well in place of the 12PW for this combination? Bob mentions a pair of 12 inch woofers, but no specifics. I was thinking of the Dayton RS-225 (I know, it's a 10 inch, but it's a starting point...), but I don't know what the crossover would need to be.
Unfortunately, I don't have the design acumen of many of you, so I have come to depend on your generous sharing to build my speakers.
Thanks,
Mike
Click to expand...

Oops, RS-270....
 
mikejennens

mikejennens

Member
Joined 2008
planet10 said:
Well yes, sorta. It has to be derived specifically for the amps you are using… A series cap for the HP, and a series R with a shunt cap for the LP. And maybe some sort of attenuator if your amp(s) don’t have gain control (usually needed on the LF amp).

TLS.org | Passive Line-Level Crossover

dave
Click to expand...

Thanks Dave. I'll give this one some serious thought. I have a Carver power amp with gain controls, so hopefully that will help if I go this way. It might be time to look into a DSP too.
 
T

toobhed

Member
Joined 2010
In reference to post #51, p6 2-way cab drawing: Would it mess up the alignment to move the 12PW down in its dedicated chamber .75". If not great....but if so, how much taller might I need to make the bottom chamber to accomodate bringing the 12PW .75"? ...if I make btm chamber taller, would I need to change port tuning?

The reason I ask: I'll start building the two way soon. But I'll also separately build another set of speakers which will simply be the dimensions of the btm chamber to house another set of 12pw. I'll use this turned-upside down and placed on top of the two-ways to create a 2 piece MTM and would like distance between 12pw/7p on two ways to equal distance between tweeter on two ways and the other cab's woofer.

I'll also use the "btm chamber" 12pw in bass support for any other full range driver small cab, ala WAW formerly FAST.

Thanks,
Mario
 
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