First time DIY Subwoofer AV12 Tube - Help!

Scott Heaton · 06-10-2003, 03:46 PM

I am planning on making 2 SVS type subwoofers (Sonotube with driver on one side and ports on the other) using Strike's TC Sounds AV12 driver. I plan to lay the subs on their sides behind the couch and drive them with a Sampson S1000 amp.

My goal is to be able to produce sound at near referance levels all the way down to at least 20 Hz.

I am looking at a 125 L volume tuned to 19 Hz.

I have enough 15.5" ID cardboard tube at work and a nearly unlimited supply of free 3 7/8 ID X 4 3/8 OD cardboard tubes that I will use as ports. I am figuring using free ends on the port, although, I may try to later put a bit of a flange into one end.

I calculate using ported.xls that I should use 2 of the ports about 37" long. This gives me a tube length of 48 1/8" long. I get about 5" of clearance from the back of the driver to the ends of the ports.

Questions:
1. Does it look like I am doing this right?
2. Are the ports too long? It seems like I would get chuffing if I used one shorter one.
3. Could someone check my calculations for me on a better program? I check mine on WinISD beta and got about the same numbers.

I guess I am just nervous that I am missing something or doing something wrong because this is my first attempt at DIY speakers and I am just going by everything I have learned on these threads.

I hope I am in bounds asking these questions in an advanced forum. I tried to read up as much as I could about this before posted so I didn't ask a "dumb" question.

Thanks for your help....

AV12
Fs: 21Hz
Qms: 4.41
Qes: .399
Qts: .366
Vas: 88 L
Re: 2.97 ohm
Z: 4 ohm
BL: 15 Tm
Cms: .25 mm/N
Mms: 228 g
Pe: 500W
1W/1m: 85.5dB
2.83V: 89.5dB
Xmax: 23 mm
Xsus: 30 mm
Sd: 498 sq cm
Vd: 2.33 L

TimForman · 06-10-2003, 06:36 PM

Try modeling it using a 6 inch port. You'll get low mach with a slightly shorter tube. Your other numbers seem to look ok at first glance. Have you tried a little more volume say 135 L?

Scott Heaton · 06-10-2003, 08:44 PM

Actually, I get a longer tube with 6 inches. 2 ports 3.875 inches in diameter have less volume than one 6 inch tube so the 6 inch one would need to be longer, right?

Anyway, I have the 3.875 sitting here for free so there would need to be a good reason not to use it. I was hoping that it would not resonate as much being thick cardboard rather than PVC.

TimForman · 06-10-2003, 09:27 PM

Well, unless WinISD is lying I get a slightly shorter length with one 6" tube vs. two 4" tubes, however, the mach is lower with the two tubes. Since they're free who can argue. Just throwing some stuff out there.

Rob Formica · 06-10-2003, 11:58 PM

"Actually, I get a longer tube with 6 inches. 2 ports 3.875 inches in diameter have less volume than one 6 inch tube so the 6 inch one would need to be longer, right?"

The cross-sectional area of your 2 3.875" tubes is about the same as the single 6" (about 5.5" internal diameter)... so they should be very similar, but you are correct in assuming normally that a larger tube x-section requires a longer length.

Are the Stryke AV series manufactured by TC Sounds? just curious... i seem to remeber seeing it posted somewhere else, but now i'm no longer sure...

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Bryan Michael · 06-11-2003, 12:25 AM

did you order yet? i have dual av15 with the samson and it is awsome to put it modestley. they are not that much more a piece and are just so awsome.

bigger the box the shorter the tube. the bigger the box you can tune lower and go lower.

but 2 av12 will rock the house.

i have a frend with a single av12 and he is very happy and olny has 250 wats going to it.

Scott Heaton · 06-11-2003, 08:36 AM

Yes, They are made by TC Sounds.

I didn't know that a 6" tube had a 5.5 inch ID. Now they come out as similar lengths.

I have the AV12s on the preorder so I have at least a month to wait for them and build my tubes. I have all of the endcaps cut. And am thinking about cutting the tubes and ports to length and putting them together.

This is a pretty big tube right now. Looks like I will cut the tube at about 48" long and with the caps they will be 49.5" long. I did think about going longer and getting shorter ports but I would always end up designing it with a lower tuning frequency instead. I think that 50" is all I will be able to get away with.

Does it look like it will work well for me? I shouldn't get much port noise? What about port resonance?

Greg Monfort · 06-11-2003, 11:24 AM

Using the published driver specs and your sonotube/venting diameter limitations, 125L is too much of an underdamped alignment IMO, so going larger just makes it worse. Unless it's an extreme EBS I've found it best to limit oversizing the cab to ~1.414x the max flat alignment's Vb, or ~92L in this case. Tuned to ~18Hz looks good even when VC heating is factored in, maintaining good impulse/transient response. A couple of these in a corner should 'rock you'.

WRT vents, according to MK's pipe simulator, two 3.875" i.d. need to be 48" long (much longer than I would like to see), but if 80Hz/4th is used it may be OK. Vent mach is low, but if their upper harmonics are audible then shortening to ~36" and mass loading to make them aperiodic should damp them right out and lower Fb back to where you want it to best blend to the room's gain.

GM

Scott Heaton · 06-11-2003, 03:13 PM

Greg,

Thank you very much for taking the time to look at this. I would love to go with a 92L tube that is tuned to 18Hz, however, the ports always needed to be too long to fit in the tube. It seems that I would need to use PRs to go that small (in my newbie thinking).

When I calculate port length of 125L @ 19 Hz, I get 37 inches long. Why do you get 48" long with your calculations? I am not saying that you are wrong, I am just trying to figure out if I need to be doing this differently.

As far as the crossover, I will use the crossover on the Pioneer 45tx and I think it will end up being around 80Hz but it must be a 12 dB / octave.

I never thought of making the ports aperiodic with fabric over the port. Does that work well?