Thanks again. It is great to get so much info. I will say that I am not feeling so thrilled about it though (I spent way, way, way too much time coming up with a solution I thought would work, albeit with trade offs), but that is why I am asking for help.
I actually started off with an idea for dual 8w7 subs. I even bought one. Then I found a good deal on the SV10s (four for less than one 8w7) and thought I would give that a go instead.
Let me take a step back and tell you what I am doing.
My budget was $1000 for stereo subs, EQ, and amplification.
These two "smallish" subs are to supplement my main monitors. I will be using a DCX2496 to do the crossovers and EQ. My thinking was that I should get these two subs to perform well in the 30-70 Hz range.
In the future I will also be building a larger sub for the LFE output, focusing on the 10-30 Hz range.
I already have the amp, the drivers, the dcx2496, and the enclosure material for the L/R stereo subs. I even have a bunch of polyfill.
With all that said, and the idea being to keep the enclosures small, focused on 30-70, using the SV10s, what would you do? Just do a sealed enclosure?
I could do a 4 cubic foot design if that is the only way to go, but I wish I could keep it smaller. I liked the passive radiator idea because it modeled well, avoided the problems and volume of a vent, and was tunable (this would hopefully make up for the novice design work). Downside? About $200.
I would make use of the drivers you have.
I personally would use the JL AUDIO 8 w7 vented. You could use these port dimensions if you can make it fit. These get the vent velocity down from 21 to 18 m/sec.
Hv = 2.25 in
Wv = 8 in
Lv = 45.91 in
You could use use two of your ACI SV 10 sealed.
Name: SV10
Type: Standard one-way driver
Company: Audio Concepts, Inc. (ACI)
No. of Drivers = 2
Mounting = Standard
Wiring = Parallel
Fs = 18.5 Hz
Qms = 4.205
Vas = 84 liters
Cms = 0.656 mm/N
Mms = 111.3 g
Xmax = 16 mm
Sd = 310 sq.cm
Qes = 0.394
Re = 2.72 ohms
Z = 4 ohms
BL = 9.48 Tm
Pe = 250 watts
Qts = 0.36
2.83-V SPL = 87.72 dB
-----------------------------------------
Box Properties
Name:
Type: Closed Box
Shape: Prism, square
Vb = 1.052 cu.ft
Qtc = 0.707
QL = 19.68
F3 = 44.29 Hz
Fill = heavy
This gives you an F3 of 44 Hz. However you can Eq a sealed unit which you can't a vented one. If you add Eq of 12 db/octave starting at 45 to 50 Hz you will have good output to 20 Hz.
You could use one of your ACI drivers vented. This is the optimal box.
Name: SV10
Type: Standard one-way driver
Company: Audio Concepts, Inc. (ACI)
No. of Drivers = 1
Fs = 18.5 Hz
Qms = 4.205
Vas = 84 liters
Cms = 0.656 mm/N
Mms = 111.3 g
Xmax = 16 mm
Sd = 310 sq.cm
Qes = 0.394
Re = 2.72 ohms
Z = 4 ohms
BL = 9.48 Tm
Pe = 250 watts
Qts = 0.36
2.83-V SPL = 87.72 dB
-----------------------------------------
Box Properties
Name:
Type: Vented Box
Shape: Prism, square (optimum)
Vb = 1.652 cu.ft
Fb = 19.32 Hz
QL = 6.862
F3 = 24.95 Hz
Fill = minimal
No. of Vents = 1
Vent shape = rectangle
Vent ends = one flared
Hv = 2.25 in
Wv = 5 in
Lv = 48.54 in
You could make a slightly larger box to extend F3, but I don't think I would, as you might have damage issues with those drivers, which are primarily intended for sealed use.
As far as passive radiators go, you still need the same size of box, and roll off is usually above 24 db per octave.
I think people chase to low an F3 on this forum and forget other parameters.
A sub that can deliver 110db or so to 25 Hz with room gain is going to be fine. My TLs have a calculated F3 of 27 Hz, however they actually measure to a little below 25 Hz. Their acoustic output is prodigious and you have to take care not to destroy the home or rupture an ear drum. So going for F3 below 20 Hz, is not necessary or desirable.
I'm not sold on this MBM idea. It sounds like a recipe for a really lumpy bumpy response. A decent main speaker should be able to reach the 60 to 80 Hz range with no trouble. Actually they should make the 40 to 50 Hz range, and many do. There should be no trouble splicing this with a sub.
I and my friend Dr Marin, have been surveying the loudspeaker scene in the Twin Cities of late. He has a good ear and owns B & W 800 Ds. Unfortunately most speakers remain pretty dreadful. Both he and I are yet to hear a speaker we could live with that did not originate from the British Isles. He is even more emphatic on that point than I am. So far we both agree that the only manufacturers whose speakers we could really live with that we have heard in the Twin Cities are by B & W and Spendor. And by no means could we live with everything from the B & W stable.
Just yesterday, we heard a set of speakers, (MRSP $3000 per pair range), that many members here own and aspire to own. The auditioning room was good and some B & Ws sounded excellent in it. These Canadian speakers had the most dreadful tubby misaligned bass with far too high a Q. However it could not disguise a rough shouty mid range and too fierce a high end. If I owned those speakers thet would get rolled off really high.
So far we have auditioned speakers by Revel, KEF, Mirage Omni, Gallo, Watt, Spendor, Vienna, B & W, Paradigm and a perfectly dreadful speaker from Switzerland, whose name I forget. Those latter were 15K per pair. The most expensive speakers auditioned and one of the worst was 50K per pair.
So having a really good pair of mains and a center if you use one, is vital. No amount of subs will make up for poor mains and center.
By the way it is generally not a good idea to mix subs with F3s apart more than an Hz or two. In fact when using multiple subs you should use the same ones if possible.
If you build either of the ported subs using one driver, I bet it won't be long before you find room for another.
