Sealed or vented enclosure for the TC-1000 SVC 12''

[Davlaf]

Hi,

That's the first time that I try to build a subwoofer. I'm in bassbox trying to modeling the perfect response curve with a low f3 and... since too much time lol. So I realized a vented and a sealed simulation. You can find the driver specification here.

Here's the sealed bos specifications:
Box Properties
Name:
Type: Closed Box
Shape: Prism, square
Vb = 2.1 cu.ft
Qtc = 0.694
QL = 7
F3 = 35.01 Hz
Fill = normal
I think that the F3 is way too high, am I right?
I used the suggested Vb by the tcsounds website


Here's the vented box specifications:
Box Properties
Name:
Type: Vented Box
Shape: Prism, square
Vb = 3 cu.ft
Fb = 20.42 Hz
QL = 6.928
F3 = 26.77 Hz
Fill = normal
No. of Vents = 1
Vent shape = round
Vent ends = one flush
Dv = 3 in
Lv = 12.26 in
I know, I know... 3 cu.ft is small for vented enclosures... But I don't have the choice, I don't have a lot of space...


Now here's the normalized amplitude response graphs... (Sealed=red, ported=turquoise)


So, what do you think about that?

Thank you,
David Lafleur

[Ron E]

Actually, a Sealed box with an F3 of 35Hz will sound very solid.

That woofer will not work ported unless you use a VERY large diameter port. If you use anything less than a 6" diameter flared port you will have mucho whistling and chuffing noises if you apply any power at all. Alternatively you could use several Passive Radiators instead of a port. Note that the Mfg. recommended enclosures are showing response with an external highpass filter which applies bass boost. This is a bit of a cheat for marketing purposes, IMO.

I'd go sealed, especially if this is for a car.

[Davlaf]

Hey Ron E,

Ok thank you so much, for the tip. But, actually, this is for my home. But, for the home, an f3 of 35Hz is still very solid?

And on the website recommended enclosures they says: "20Hz Extention Systems (Home Audio, -3dB at ~18Hz)"

Thank you for the fast reply.
David Lafleur

[Ron E]

Originally posted by Davlaf
But, actually, this is for my home. But, for the home, an f3 of 35Hz is still very solid?

Yes. Remember that the room will add some lift. If you want lower bass, you put the sub in the corner and/or add a linkwitz transform.

TC Sounds has a good reputation so it is curious that the given parameters are inconsistent. Before I designed a box for that woofer, I'd measure the actual parameters.

------------------------------------------------------------------------------
I put the following parameters into my calculator:
Fs 22.0 Hz
Qts 0.373
Qes 0.404
Vas 101.0 Liters
Re 4.25 Ohms
Dia 20.5 cm
and get the calculated parameters of:
Sd 0.0330 m^2
Mms 0.0793 kg
Cms 0.000660 m/N
Bl 10.74 T*m
no 88.85 dB/2.83V
no 86.10 dB/1W
Qms 4.86
Rms 2.25
-------------------------------------------------------------------
If instead I use the given fundamental parameters:
Sd 0.0330 m^2
Mms 0.1100 kg
Cms 0.00035 m/N
One gets the resultant parameters:
Fs 25.6 Hz
Vas 53.6 liters

I haven't calculated Qts, Qes, Qms here.

Notice that the given parameters of Fs, Vas and Q give different values of Cms and Mms than quoted, and using the given values for Cms and Mms give different Fs and Vas than quoted.

[Davlaf]

Yeah, I noticed that, but I don't know why they don't give Le too... I would like to know this parameter...

I noticed that the parameters are incoherents... I did 2 "box simulations".... One with coherents parameters and the other one with the tcsounds givenparameters. I don't know which one to use...

Thank you for the reply,
David Lafleur

[Ron E]

Le is given indirectly

I wouldn't use the given or extrapolated parameters when designing a box. I would measure them. Of course, you won't know whether it is suited to your enclosure size before buying, but that is the problem when manufacturers don't give consistent parameter sets - and often even when they do

Good luck.

[Davlaf]

Thank you Ren E for the reply,
I would like to measure them, but Parts-Express don't sell the woofer tester 2 anymore... They will update it and start selling a new one in the mid 2007. So, should I take the tcsounds specifications or the coherent specifications?

And, in my "Need URGENT advice! on subwoofer purchase!" thread, BAM said: "Build the TC Sounds recommended 3-cubic-foot vented enclosure, with the single 4"-diameter vent. Use a Precision Port flared port kit from Parts Express. These will give you good results. It takes an incredible amount of motor strength to generate the kind of air movement that the TC-1000 is capable of from an enclosure smaller than 3 cubic feet. But the good news is, a 3-cubic-foot enclosure is more compact than you may think. Build an enclosure with internal dimensions of 14.5"Wx18"Hx20"D. The vent length needed should be able to fit into that space".
I'm confused... I don't know what I should do.

Thank you,
David Lafleur

[paulspencer]

You haven't really given us much info for us to advise you. Your room will determine the room gain you will get. In some rooms, there is no room gain at all. In such rooms, for low extension for HT you might go for vented. If you have a room with lots of gain, you might for for a sealed box. This is a bit simplistic, but it's a start.

I recommend you simulate with WinISD pro alpha. The plots you show don't have appropriate filters, hence the response will be much different. Where are you crossing this sub? What are your mains?

I've written some articles in the wiki on how to simulate with WinISD, you might like to have a look.