Dear DIY community – As a newcomer to the DIY forum I have a question to the “fullrange speaker” users and especially to Dave of planet 10, “Scottmouse” Scott Lindgren both as Mark Audio Insider and “rutcho” as general Fullrange connoisseur: I want to build a case for my Mark Audio Alpair 12 P Gen. 2. The “Pensil” and the “Super Pensil” are definitely too big for me and the “small reflex” for the 12. 2 is “only” tuned to 55 Hz. There should also be a port of any kind on the front.
The housing should be between 40 – 50 liters with a height of max. 65 cm (I don’t want twin towers in the living room) and approx. 46 – max. 50 Hz reach because my ATC 2 way monitors “only” go up to 54 Hz.
The amplifier is an EL 84 PP amp with 22 WPC.
Is there a suitable DBR housing for the MA 12 P Gen. 2, a BVR (short horn) housing, TL housing or a ventilated thin wall reso housing ala “Wilimzig” that meets the two desired criteria?
Thank you very much for your tips
Kind regards Stefan
The housing should be between 40 – 50 liters with a height of max. 65 cm (I don’t want twin towers in the living room) and approx. 46 – max. 50 Hz reach because my ATC 2 way monitors “only” go up to 54 Hz.
The amplifier is an EL 84 PP amp with 22 WPC.
Is there a suitable DBR housing for the MA 12 P Gen. 2, a BVR (short horn) housing, TL housing or a ventilated thin wall reso housing ala “Wilimzig” that meets the two desired criteria?
Thank you very much for your tips
Kind regards Stefan
I don't recall ever seeing a DBR for the 12p. Chances are, it could take up the same floor space as a Pensil, and have similar performance, so maybe a bit redundant.
You could build the small BR boxes, and fill in the low bass with a couple of small powered subs.
jeff
Scott & i are just finishing a BVR for the A12p.
This is the first snap, Scott hasn’t even seen it.
Really close to 40x80x40cm (WxHxD).
You are in no man’s land with the volume you want, a reflex can be too big, more than about 20 litres is pushing it with A12.2p.
Horns & TLs tend toward large. So little in between. This might be one of the first.
dave
This is the first snap, Scott hasn’t even seen it.
Really close to 40x80x40cm (WxHxD).
You are in no man’s land with the volume you want, a reflex can be too big, more than about 20 litres is pushing it with A12.2p.
Horns & TLs tend toward large. So little in between. This might be one of the first.
dave
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This driver if not fit for that, it's a bigger fullrange driver but it's actually not possible to bring it that low with a flat response in a reflex. In a TL type it is. But that will be to big.
The smaller 10.3 or 10P can be tuned that low (45Hz) in a 17.9L reflex like i did with the 10.3, but the bigger 12P can't go that low in a reflex. You got the wrong driver for that.
The smaller 10.3 or 10P can be tuned that low (45Hz) in a 17.9L reflex like i did with the 10.3, but the bigger 12P can't go that low in a reflex. You got the wrong driver for that.
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Worth repeating. The A12pw is the MA LF champ, A10.2, EL70, CHN 110 the set of drivers with the greatest LF potential.
dave
Hard to say, it is only a drawing in progress ATM.
But unlikely to reach as low as Joan, but i have not seen the sims.
dave
But unlikely to reach as low as Joan, but i have not seen the sims.
dave
I simulated something similar in Hornresp for fun.
Rear loaded exponential horn with St=30sqcm , At=700sqcm , l=72cm , Fc=120Hz and 22liter compression chamber.
Looks nice, Fb=42Hz and about same F3. Total system volume 37,3 litres. Max group delay 14,5 ms at 39Hz.
Rear loaded exponential horn with St=30sqcm , At=700sqcm , l=72cm , Fc=120Hz and 22liter compression chamber.
Looks nice, Fb=42Hz and about same F3. Total system volume 37,3 litres. Max group delay 14,5 ms at 39Hz.
Finnaly, a promising box solution for those wanting the higher sensitivity of the A12p driver for pairing with flea power SET's in a smaller room.
If you have a no-feedback SET amp, the optimum reflex box can be tuned to the resonance frequency 42 Hz with around 50-60 liters volume. This is because the output resistance of the amp (typically about 2.5 ohms) increases QT.
A SET with high output impendance can work to tune it that low, but i still would not make the cabinet bigger than 35 to 40L that way. Bigger will make a peak at the tuning frequency which typically sounds like a one note bass. But 42Hz is possible with a high output impendance amplifier.
And i don't think the OP has a SET like this, with a normal amplifier this does not work as bass will be very weak. You could put a resistor in between that emulates that high output impendance, but then you are burning a lot of power to heath and loose sensivity.
EL84 PP power amp. Even mine in triode Rout is not too high and pentode or UL is likely lower.
dave
dave
Well, I didn't model it, just noticed that the modified QT is 0.38, the theoretical value for a pure Butterworth response at the resonance frequency in a Vas box. And I misremembered the Vas for the Alpair.
So just now I dug up an online calculator which said if you raise the Q to 0.4 (not 0.38) you get a 43Hz f3 in a 41 liter box. You could go further of course, but I agree that getting too deep into Chebyschev alignments is problematical.
Yes there is some wasted power with a resistor - about a quarter of the total. The resistor will dissipate that wasted power, so it should be rated for it. It's a kluge, for use if you don't have an SET, and impractical for amps much more than 15 watts or so.
So just now I dug up an online calculator which said if you raise the Q to 0.4 (not 0.38) you get a 43Hz f3 in a 41 liter box. You could go further of course, but I agree that getting too deep into Chebyschev alignments is problematical.
Yes there is some wasted power with a resistor - about a quarter of the total. The resistor will dissipate that wasted power, so it should be rated for it. It's a kluge, for use if you don't have an SET, and impractical for amps much more than 15 watts or so.
BVR can boost the efficiency if designed so, but only in a limited bass bandwidth. So, whishfull thinking.
12P is actually a 6,5in driver in a 8in basket.
Proposed 40x80x40cm box is to big at my opinion, pushing the limits to far. Also, you may find it inpractical for "smaller room". But, Iam interesting to see final result.
I've been tied up with a memorial conference for the past fortnight & still dealing with the aftermath, but FWIW, a couple of points:
1/
2/ If it's the box I'm thinking (which, incidentally, is not a 'proposed' box, but a commissioned design), I'm afraid there is a bit of a misunderstanding: Dave has inadvertently mistaken the 12P for the 12PW; it is in fact designed for the latter, which has very different electromechanical damping and requirements from the enclosure to the 12P.
I / we can do something for the 12P if there is interest though. I've thought for a while that I really should get a new series of boxes done to complement the current range.
1/
appears to be predicated on no actual knowledge of the enclosure design or alignment details, which Dave has not specified. For all anybody here knows based on the information provided, there may be internal partitions and chambers which do not contribute to the loading Vb. So let's not get too far ahead of ourselves in assumptions. 😉 And
2/ If it's the box I'm thinking (which, incidentally, is not a 'proposed' box, but a commissioned design), I'm afraid there is a bit of a misunderstanding: Dave has inadvertently mistaken the 12P for the 12PW; it is in fact designed for the latter, which has very different electromechanical damping and requirements from the enclosure to the 12P.
I / we can do something for the 12P if there is interest though. I've thought for a while that I really should get a new series of boxes done to complement the current range.
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:^)
The visualization of the inside is not yet ready for prime time.
Not so inadvertently, since the email was titleds A12p BVR :^) Makes a lot of sense that it would be A12pw. The A12pw needs about 2x the volume of the A12p, goes over an octave lower and is about 3 dB less sensitive. I personally prefer it over the A12p even as a FR.
I will revise. Only need to add some “w”s
dave
What sort of alignments do you have in mind?
Look like the BVR (mistakenly) got some interest.