So, I pulled a pair of Seas CA21RE drivers from the car (they wanted a bigger enclosure than I had room for) and decided to augment my home setup: AR-XA table, NAD 3020 amp, Boston A60 speakers.
I was looking at straight push-pull designs until I stumbled on all the sonotube hype. Went to Home Depot and got a 5' length of 8" quickrete tube, stuffed it and mounted one driver. Pretty cool. Cut off 1" and made a mounting ring for driver #2, out of phase. Much cleaner, faster, a bit less SPL.
System is passive with an old Allison sub x-over (not exactly sure of the freq., it's 200Hz at 4Ohm, all speakers are 8Ohm. 5mH coils and 110uf caps, 12db 2-way. Speaker Workshop seems to still have it around 200Hz).
I don't fully understand the relationship between Vas and Vb, but according to Shultz's calcs I need an Sd of 10.25" -- a 10" tube should be pretty close.
So, should I mount both drivers push-pull in a single 10" tube, single 8" tube, or separate them into dual 8" tubes like Pass recommends? Either way I plan to put a 3/4" MDF box around the whole thing for looks and rigidty, and I may eventually use something like that nice MCM buyout plate amp, but it will stay passive with this x-over for a bit.
Relevant specs are:
Qts: 0.48
Vas: 81.3l/2.871ft^3
SPL: 91db
Xmax: 6mm
I have the rest if need be.
Thanks to all in advance!
I was looking at straight push-pull designs until I stumbled on all the sonotube hype. Went to Home Depot and got a 5' length of 8" quickrete tube, stuffed it and mounted one driver. Pretty cool. Cut off 1" and made a mounting ring for driver #2, out of phase. Much cleaner, faster, a bit less SPL.
System is passive with an old Allison sub x-over (not exactly sure of the freq., it's 200Hz at 4Ohm, all speakers are 8Ohm. 5mH coils and 110uf caps, 12db 2-way. Speaker Workshop seems to still have it around 200Hz).
I don't fully understand the relationship between Vas and Vb, but according to Shultz's calcs I need an Sd of 10.25" -- a 10" tube should be pretty close.
So, should I mount both drivers push-pull in a single 10" tube, single 8" tube, or separate them into dual 8" tubes like Pass recommends? Either way I plan to put a 3/4" MDF box around the whole thing for looks and rigidty, and I may eventually use something like that nice MCM buyout plate amp, but it will stay passive with this x-over for a bit.
Relevant specs are:
Qts: 0.48
Vas: 81.3l/2.871ft^3
SPL: 91db
Xmax: 6mm
I have the rest if need be.
Thanks to all in advance!
I can't believe no one has an opinion?
When I went from an 8" to a 10" tube, the bass definitely got lower although I lost some punch in the midbass range -- this is consistent with what I've read. I'm still confused about stuffing density and Vb though.
I realized that I had gotten 4' tubes and not 5'! The 10" tube gives me a Vb of 2.181ft^3, the driver's published Vas is 2.871ft^3 and I'm using 2 in a push-pull if it matters. I plan to add another 6" by building a box, giving a Vb of 2.454ft^3, but it's still below the Vas. What can I expect from a 12" tube?
Also, the quarter-wavelength at 4' is 70.625Hz -- how low will the stuffing get it? I've heard that stuffing can "effectively double" the line length, reduce the SoS to 2/3 (for a tuning freq. of 47.08333Hz?), or reduce the SoS to .7-.9 (and yes I realize this is an apparent rather than actual reduction). Shultz's charts say I should shoot for 1.5lbs/cubic foot! Can anyone explain this stuff or point me in the right direction?
Finally, John Risch suggests tuning for lower than Fs with a moderate-to-high-Q driver -- the Seas' .48 seems to fit that bill. I could possibly get pretty close with a stuffed folded line using my 2 tubes or the 10" and a 12". Everywhere else I've seen tunings higher than Fs, so I would be OK between 38-43Hz...Help!
TIA
When I went from an 8" to a 10" tube, the bass definitely got lower although I lost some punch in the midbass range -- this is consistent with what I've read. I'm still confused about stuffing density and Vb though.
I realized that I had gotten 4' tubes and not 5'! The 10" tube gives me a Vb of 2.181ft^3, the driver's published Vas is 2.871ft^3 and I'm using 2 in a push-pull if it matters. I plan to add another 6" by building a box, giving a Vb of 2.454ft^3, but it's still below the Vas. What can I expect from a 12" tube?
Also, the quarter-wavelength at 4' is 70.625Hz -- how low will the stuffing get it? I've heard that stuffing can "effectively double" the line length, reduce the SoS to 2/3 (for a tuning freq. of 47.08333Hz?), or reduce the SoS to .7-.9 (and yes I realize this is an apparent rather than actual reduction). Shultz's charts say I should shoot for 1.5lbs/cubic foot! Can anyone explain this stuff or point me in the right direction?
Finally, John Risch suggests tuning for lower than Fs with a moderate-to-high-Q driver -- the Seas' .48 seems to fit that bill. I could possibly get pretty close with a stuffed folded line using my 2 tubes or the 10" and a 12". Everywhere else I've seen tunings higher than Fs, so I would be OK between 38-43Hz...Help!
TIA
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