Sonosub stuffing?

[alliclaytor]

Hey all...quick question. I am building a sonosub with a TC-2000 driver (24" dia, 44" tall, 29" * 6" port ~ 15hz tuning) and didn't know what if any kind of stuffing or sound deadening material I would need to use on the inside? If so I have read that the cheap stuff at the local big box mart will due...but how would you attach it to a cylinder wall? Any help would be appreciated. Thanks!

[Jay481985]

a little glue to the sidewall should be enough..... That is a huge box..... 11.5 cubic feet....................

tcsounds surprisingly gets non linear once the enclosure gets too big...... the bl is too high..

[alliclaytor]

I can always make it smaller...not that hard to cut the top off a few inches if i dont like the results...

[alliclaytor]

Ok...Ok...I admit I basically hang around the 2 channel/HT areas. But I have learned a great deal recently about subs from this corner of Klipsch so I am sorry guys and I hope you season vets can give me some advice. Jay mentioned maybe not so linear a freq curve on my setup due to high volume (ft ^3) so i modeled it with a crossover to my rf-7's at 50 hz. It looked fairly linear in winisd but was around 3db under the "ideal" for most of the curve. With the endcaps on the tube I show it being ~10.5 ft^3. Am I modeling it incorrectly? Should I make it smaller (that what she said...Michael Scott) or am I good to go. Also, if it helps I am using this for mostly movies...but my preference would be to make it sound great for music and the movies will suffer a bit.

[DrWho]

The longest dimension you want on your subwoofer is:

3396 / frequency = Length in inches

So if you want your sub to be good up to 80Hz, then it can't be any

longer than about 42". This corresponds to the frequency where you'll

get a huge dip in the response due to the outta phase reflections

inside the enclosure. And then you're going to have a resonance/peak an

octave above that frequency (so 160Hz in this example) which is the result of the first standing wave. While that may

not seem like a big deal at first, keep in mind that a crossover slopes gradually and the gain of a standing wave can be very large (like 6-10dB). So if your crossover rolls off at

12dB/octave, then you're looking at only being 2-6dB down at the first

harmonic. Since you've got the dip right before it, you're going to

find it difficult to achieve a seamless crossover transistion to the

mains. For an 80Hz crossover, I would try to target a length more like 21".

Also, a single TC-2000 isn't going to be enough to create a lot of

visceral feeling. So while I understand why you're tuning so low, I

would argue that you would appreciate the sound of your sub a lot more

if you moved the tuning frequency higher. The nice thing about moving

the frequency higher is that you can also benefit from a slightly

smaller enclosure. By going this route you will also dramatically

reduce IMD and increase the maxSPL of the system and also reduce the

magnitude of port chuffing and power compression. While all of these

things will certainly enhance music dramatically, I would argue the greater

dynamics would also yield a better movie experience too.

What amplifier will you be using with the driver? Is there any kind of bass boost or PEQ built into the amp?

Have you modelled the driver in WinISD or any other T/S parameter

program? I haven't run the numbers, but I would be inclined to

recommend something more along the lines of a 3-5 cubic foot enclosure

tuned to around 22-24Hz. Keep in mind that you're going to get gain

from the room too. I would also implement some EQ on the amplifier to

reduce cone-excursion below the tuning point and perhaps a little bit

of boost in the port tuning frequencies where excursion is lower. Don't

go overboard though - you want to keep the air velocity in the port

under 20 m/s (you'll probably end up targetting for under 50 m/s).

I'm not sure if you were asking this or not, but sonotube will

absolutely require damping material inside the enclosure. While all of

the resonances are out of the intended passband of the driver, the

resonances can still be triggered by harmonic distortion. What I do is

go dumpster diving at a carpet warehouse place (after getting

permission) and taking home a bunch of carpet padding. This stuff works

great and it'll be free. Make sure you go at the end of the day when

the carpet crews are coming back and dumping their leftovers. An inch

thick around all the interior surfaces should be enough.

Hope this helps.

[alliclaytor]

First off...thanks for the info. And i will try to give as many detailed responses as I can.

The tube itself is 44 inches long, with the end caps it would be at most 41" (inside the tube are 2 * 3/4" mdf * 2 (top and bottom))

The crossover i am planning on using is the beringer SUPER-X PRO CX2310 it has 24db/oct slopes + whatever my receiver has, variable crossover from 10 to 235 hz, and a sub gain control (and a 25hz cut if I am concerned about the low frequencies). I realize it may not be the best of options but I have it lying around to mess with. I am planning on using my crown power base 3 (>1000W @ 4ohms) for the time being to power the speaker.

I have tried to model the sub in both winisd and sonosub.exe and gotten mixed results. I have just been trying to learn on the fly without much instruction on the specific ins and outs of the software and its use.

I do like the idea of less distortion...after all I am a Klipsch fan

I am not so concerned about tuning the sub between 15 hz and 25hz...although I know I can kinda hear it, I don't know how much it will make a difference to me. So there is a place for a possible change.

I will dampen the tube...no questions asked.

For the velocity of the air...I have the largest port I can find, 6" dia with flares on both sides...It's on the way.

I guess right now the major questions are port length, gross tube length, and crossover point. I am not the type of person to ask for someone to do my work for me...I want to understand why I am building it the way I am...but I don't have the experience to model it and know where to go. I like the idea of a huge box...but I am ok with it being smaller too.

[Jay481985]

For the velocity of the air...I have the largest port I can find, 6" dia with flares on both sides...It's on the way.

where??????????!!!!!!!!!!!

[alliclaytor]

Thrilleraudio.com

[DrWho]

It would be worthwhile to learn how to model accurately in WinISD. You can even take the program a step further to get an idea of the nonlinear characteristics too. The cool thing about learning the program is that you'll gain a better understanding of how subwoofers work. If you wanted to post your T/S parameters and box parameters, we could start a discussion with a working model.

Doesn't TC sounds offer recommended enclosures and tunings? The fun thing about modelling is that you usually end up with the recommended enclosure - or at least can gain an understanding of why it's the recommended enclosure and determine if you'd like to make different compromises.

[alliclaytor]

The Driver

Fixed

SVC

15"

Qms

4.26

Res ?

3.12

BL

17.20

Mms

(grams)

296.00

Cms µN/M

260.00

Sd (m^2)

0.0820

Lp (mH)

Ls (mH)

Rp ?

Constants

c (m/s)

341.00

d (kg/m³

1.20

K

9.64E-10

Calculated

Vas (liters)

243.94

Fs (Hz)

18.14

Qes

0.356

Qts

0.328

n0

3.95E-03

SPL (dB)

87.96

Xmax = 28mm

[alliclaytor]

TCSounds used to recommend a box size, but I can't find it under their current website. When I did look though, there didn't seem to be anything comparable (in my mind) to what I was looking at building.

The Box:

44" tall, which can be cut to length
24" diameter

Port: 6" with a flare on both ends can be between 5" and 29" long
End Caps" 3 * 3/4" mdf with two inside the box and one outside for a nice roman column look

I would like to learn more about how to model these things, and really do appreciate any and all help given. When I did model it in winisd, if I put all the parameters in there were a significant amount of redundancy check errors. I then looked online how to enter the data and got some help. Even after than when you put the box type, ports, etc in the suggested areas I don't have the pedigree to know if it was done correctly especially with such a different config than what is generically outlined in winisd.

[alliclaytor]

I've received the port. And plan on building asap, thoughts on size?

[DrWho]

Hey Clay,

Got your PM and I'm glad you mentioned it because I was intending to get back to this, but forgot about it.

You might find this thread somewhat helpful:

http://forums.klipsch.com/forums/4/717845/ShowThread.aspx

This link brings you to page 4 where I started talking about the design

we ended up going with. You might check out my first post to get an

idea for the scope of the project. Everyone situation requires

different compromises, but sometimes understanding compromises that

others choose can help you make decisions with your own design. I

reread some of my posts just to see what I was talking about and man

have I learned a lot since then...

Anyways, as far as your project. The non-linears that can be predicted

in WinISD actually show rather controlled behavior with an 18Hz tuning

in a ~8 cubic foot enclosure. One of the annoying things about TC

Sounds is they never post any inductance specs, which are generally

rather high because they're trying to get so much power out of the

motor. This shows up as a slight rise in the response at the upper end

of the subwoofer's passband. It's not a huge deal and you've got a

processor there to take care of it. With no inductance (Le) put into

the model, you just get a flat line above ~80Hz. I modelled with 2.5mH

in these plots. It's usually around 1mH on most drivers, but you can

play around with it to see how it shifts. The point isn't so much to

predict an absolute as it is to find a general trend and try to model

around a middle point.

Attached is my modelling comparing the ideal world scenario (purple

plot) to what I predict the non-linears to do to the response (blue

plot).

[alliclaytor]

Thanks for the reply...when I get home I will try to plug the numbers in and see if I can come up with the same stuff you did. I want to build an awesome sub as much as i want to learn how to use winisd...so thanks on both accounts. I will post pics when I can. Also, I'll see if I can get TCSounds to give me the inductance ratings. Hope all is well.