Hi Norman,
The cabinet's external size is 31cm wide, 24.5cm high and between 27cm and 30cm deep, made of 2cm MDF. I don't think there is any bracing as it's too small to need any, but I think Mark put a bit of foam lining in. That makes it just over 17L (less the foam and driver itself) which I think is nearly twice the .32ft3 you calculated.
The driver is tilted up to allow for the distance below the monitor, which is already an LCD, but at 47" would be too high with a speaker under it.
Graham
The cabinet's external size is 31cm wide, 24.5cm high and between 27cm and 30cm deep, made of 2cm MDF. I don't think there is any bracing as it's too small to need any, but I think Mark put a bit of foam lining in. That makes it just over 17L (less the foam and driver itself) which I think is nearly twice the .32ft3 you calculated.
The driver is tilted up to allow for the distance below the monitor, which is already an LCD, but at 47" would be too high with a speaker under it.
Graham
Mark has OKed these drawings and has asked me to post them. URLs below. Visualization of Twin A7 tower:
dave
Twin A7 Tower
Twin A7 Centre
A12 Centre
dave
Twin A7 Tower
Twin A7 Centre
A12 Centre
I'm not sure............
But my guy who builds boxes for me used oak ply with more layers than the 5 one from Home Depot, but he has a wood place nearby and can get 1/4" cherry (damn pretty).
I thought I'd come across 13 ply 3/4" appleply 5 or so years back at a local medium sized hardware store called Menards.
The dual alpair 7's work for surrounds in Graham's system because they are much closer to your ears than the 3 alpair 12's across the front. The a7 has about 39 cm2, so 2 of them have a squeek more than half of the area of an alpair 12 (149cm2). The dual a7 looks like a mltl, while the pencil with its large slot works more like an open baffle providing a boost below the drivers hump, awesome idea there. The a12's +5db hump falls 300-500hz, close to the textbook -3db point for baffle step for a baffle 10.5", then the box hump fills in from 100-300hz (+6db Feq like open baffle) by using the rear wave (where baffle step would be 6db down, at least in my setup backing up to large windows).
I believe 1 larger driver is better than 2 smaller drivers because the ceiling reflection is smoother than the multiple suckouts you get when standing above / below a dual driver setup (or off axis of an mtm or a dual full range driver setup). Otherwise the sound seems like it is coming at you from a tunnel in front of you, similar to what I hear when listening to a d'appolito mtm, but much different from someone speaking in the room. A single driver feels more like a point source than my dual 4" does, hard to put your finger on exactly why.
I'd rather run A12 pencils all the way around. That way you can easily swap them if damaged, blown, etc. It would be hard to make a center channel pencil for the 12, but I think it is possible, assuming you can have a seperate large shelf for a maybe squarish 2' x 2' box (I could) .....
Norman
Stereo Clarity (my markaudio supplier)
Welcome to Nick Ozanich Custom Home Theaters! (my builder)
But my guy who builds boxes for me used oak ply with more layers than the 5 one from Home Depot, but he has a wood place nearby and can get 1/4" cherry (damn pretty).
I thought I'd come across 13 ply 3/4" appleply 5 or so years back at a local medium sized hardware store called Menards.
The dual alpair 7's work for surrounds in Graham's system because they are much closer to your ears than the 3 alpair 12's across the front. The a7 has about 39 cm2, so 2 of them have a squeek more than half of the area of an alpair 12 (149cm2). The dual a7 looks like a mltl, while the pencil with its large slot works more like an open baffle providing a boost below the drivers hump, awesome idea there. The a12's +5db hump falls 300-500hz, close to the textbook -3db point for baffle step for a baffle 10.5", then the box hump fills in from 100-300hz (+6db Feq like open baffle) by using the rear wave (where baffle step would be 6db down, at least in my setup backing up to large windows).
I believe 1 larger driver is better than 2 smaller drivers because the ceiling reflection is smoother than the multiple suckouts you get when standing above / below a dual driver setup (or off axis of an mtm or a dual full range driver setup). Otherwise the sound seems like it is coming at you from a tunnel in front of you, similar to what I hear when listening to a d'appolito mtm, but much different from someone speaking in the room. A single driver feels more like a point source than my dual 4" does, hard to put your finger on exactly why.
I'd rather run A12 pencils all the way around. That way you can easily swap them if damaged, blown, etc. It would be hard to make a center channel pencil for the 12, but I think it is possible, assuming you can have a seperate large shelf for a maybe squarish 2' x 2' box (I could) .....
Norman
Stereo Clarity (my markaudio supplier)
Welcome to Nick Ozanich Custom Home Theaters! (my builder)
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The Pensil12s?
planet_10 hifi
If you check back in a few days there is a more comprehensive document going up that includes the superPensil12
dave
The Twin A7 is really an ML-TL, the Pensil12 is an ML-TL variation as well, distinct enuff, and borrowing from th epast sufficiently to get its own name
dave
ah, ok, thanks dave ........
A friend at work said the large slot (in the pencil) is really an early transmission line of sorts, you can see it on the Z curve.
Since I have a dual 4" in a single box, I'd highly recommend AGAINST a dual alpair 7 center channel. It is really a "one pair of ears" design. A little off axis and you lose highs very quickly. Under over, maybe, but not side by side.
Norman
A friend at work said the large slot (in the pencil) is really an early transmission line of sorts, you can see it on the Z curve.
Since I have a dual 4" in a single box, I'd highly recommend AGAINST a dual alpair 7 center channel. It is really a "one pair of ears" design. A little off axis and you lose highs very quickly. Under over, maybe, but not side by side.
Norman
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Hi Norman,
I'm recommending the Alp7 twin centre. Possibly you're experience is coloured by drivers with "typical" limited dispersion patterns. The Alp7 has a very wide emittance pattern, particularly in the 9 to 18-kHz range. For anyone needing a centre with more power handling and less cab height, the A7 twin is a design worth serious consideration.
Cheers
Mark.
The twin alpair 7 center design has the drivers side by side.
On axis you will be fine, but sitting in the seat left or right of the sweet spot, you will lose highs. My setup is 2 couchs, 1 faces the tv, the other on the wall to the right when you look at the tv. I tried my dual 4" side by side and there was no high end sitting on the couch off axis, similar to someone throwing a thick blacket over a speaker.
Combing.
If you had the drivers stacked one above the other, then you can take advantage of the alpair 7's wide dispersion (but careful of the vertical ear height), but not stacked side by side. My 4" has 5" frames so the dual alpair may have less of a problem, but it is still a problem.
Sorry to disagree with you Mark.
Norman
On axis you will be fine, but sitting in the seat left or right of the sweet spot, you will lose highs. My setup is 2 couchs, 1 faces the tv, the other on the wall to the right when you look at the tv. I tried my dual 4" side by side and there was no high end sitting on the couch off axis, similar to someone throwing a thick blacket over a speaker.
Combing.
If you had the drivers stacked one above the other, then you can take advantage of the alpair 7's wide dispersion (but careful of the vertical ear height), but not stacked side by side. My 4" has 5" frames so the dual alpair may have less of a problem, but it is still a problem.
Sorry to disagree with you Mark.
Norman
.
Hi Norman,
Its good to voice your thinking, its welcome. But I have the advantage of years of hard bitten experience designing and producing my drivers. The Alp7's have exceptional dispersion and won't suffer from the problems you describe to a significant degree.
At typical listening distance (2+ metres), Combing isn't going to be an issue on twin drivers of the A7 size provided they positioned close together in their cab.
Certainly, room influences will make a difference to any set-up. Graham's single A12 centre speaker has the front baffle angle up to take care of its low near-floor position.
Cheers
Mark.
More on twin Alpair 7s
Hi, just wanted to add my personal observations.
First of all the Alpair 7 is my all time favorite, its dispersion (and hence 3 dimensional sound stage) in a normal stereo setting is second to none, more or less independent of price.
We are currently custom building a 5.1 system for a client and experimenting with both Alpair 7 and chr70.
For the center channel it actually appears that the Alpair 7 is doing better than the chr70 in twin driver configuration. I suspect that the Alpair 7s dispersion and proximity of the two speakers in a side-by-side configuration makes them blend into almost one source.
The center speaker is for dialog, and the twin side-by-side configuration does that job really well, I would of course not use those for stereo or the left and right channels.
Hi, just wanted to add my personal observations.
First of all the Alpair 7 is my all time favorite, its dispersion (and hence 3 dimensional sound stage) in a normal stereo setting is second to none, more or less independent of price.
We are currently custom building a 5.1 system for a client and experimenting with both Alpair 7 and chr70.
For the center channel it actually appears that the Alpair 7 is doing better than the chr70 in twin driver configuration. I suspect that the Alpair 7s dispersion and proximity of the two speakers in a side-by-side configuration makes them blend into almost one source.
The center speaker is for dialog, and the twin side-by-side configuration does that job really well, I would of course not use those for stereo or the left and right channels.
Good to see you here Kurt. The A7 is my favorite too...
Your findings are interested, partly because with its wider bezel separation on the A7 is going to be greater.
Having worked just this last week on the CHR & the A7, the cone profile & the cone surface are different with the A7 being more refined. The more advanced cap on the A7 is going to have an effect as well.
Your findings are interested, partly because with its wider bezel separation on the A7 is going to be greater.
Having worked just this last week on the CHR & the A7, the cone profile & the cone surface are different with the A7 being more refined. The more advanced cap on the A7 is going to have an effect as well.
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