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Discussion Starter #1 (Edited)
Hi there!

I'm a Spanish boy and I'm beginning in this HT world. I've found this page by searching on google and it seems very interesting.
My plan is to build a full custom made HT 5.1 (it may last 2 years to complete that). :)
I'm currently designing the subwoofer because right now I've a Kenwood 2-channel stereo that has subwoofer pre-out. I will use it while I get enough money to continue with the rest.
Later I'll make two new boxes to have a modestly-powerfull 2.1, ending with a 5.1 powered by one Yamaha AV receiver.

I have my eye on a Kicker C12 12" 89.1db 1W/1m 150W RMS (aprox. 100$) to make the sub, using WinISD seems better than the CVR12 12" 86.7db 1W/1m 400W RMS (aprox. 140$) with lower power consumption. Could you recommend any other good sub or brand? I think it's a good choice but I would like to discuss this :)

The main problem is to get good power and the smallest size. I have two desings right now:

Small Box Properties: 370 mm x 370 mm x 370 mm
Type: Vented Box
Shape: Prism, square
Vb = 32,93 liters
Fb = 36,08 Hz
QL = 6,963
F3 = 46,18 Hz
Fill = none
No. of Vents = 1
Vent shape = round
Vent ends = one flared
Dv = 68, mm
Lv = 220, mm


Medium Box Properties: 450 mm x 450 mm x 450 mm
Type: Vented Box
Shape: Prism, square
Vb = 65,53 liters
Fb = 36,82 Hz
QL = 6,963
F3 = 35,08 Hz
Fill = none
No. of Vents = 1
Vent shape = round
Vent ends = one flared
Dv = 100, mm
Lv = 200, mm


The vent size is adjusted to use commercial ports and prevent chuffing. Tuning frequency should be between 35 hz and 40 hz. I want to use a bandpass filter and use the range from 27 to 80 hz.

I noticed that in the impedance graph I have a peak of 24,59 ohms at 55,59 hz, is this troublesome?

I'm making the boxes using WinISD and BassBox Pro 6. This last one shows cone displacement and I realized that other previous desings should blown up the sub because I almost doubled the XMax value :innocent: (I tried Beyma SCW12 12" 92db 1W/1m 250 RMS with XMax 4 mm :no:).

Could you give me any advice? Maybe other project already made that meets what I'm trying to do?

Thank you. :D
 

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Discussion Starter #3 (Edited)
Sure!

Driver Properties
Name: C12 (4 ohm)
Type: Standard one-way driver
Company: Kicker
Comment: Comp series
No. of Drivers = 1
SPL = 89,10db 1W/1m
Fs = 26,5 Hz
Qts = 0,43
Qms = 9,61
Vas = 127,7 liters
Xmax = 9,76 mm
Sd = 532, sq.cm
Qes = 0,447
Re = 3,69 ohms
Le = 2,9 mH
Z = 4, ohms
Pe = 150, watts

Full datasheet is availiable here:

hxxp://www.kicker.com/sites/default/files/2007Comp.pdf

I forgot to mention, I'm looking for a subwoofer of aprox. 150$ ~ 180$ or less with good parameters for the price. I've seen here some monsters with Xmax > 20 and Pe > 300W for 250$ but I think it's too much for what I need.
 

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Fot HT use, output down to 20 hz is a good design goal, neither of the 2 models you posted will achieve that. The C12 requires a much bigger cabinet to achieve 20 hz output. If cabinet size is an issue, tell us the maximum cabinet size that is acceptable and we'll see if a better sub driver can be found.

Kicker c12.JPG
 

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Discussion Starter #5
Ummm good question. I was looking for a compact design, but maybe it's worth making a big box if the performance is really increased.

I already saw that for HIFI it recomends more than 100 litres. With the parameters you posted BB Pro 6 recommends this cubic box:

Big Box Properties: 887,3 mm x 548,4 mm x 338,9 mm
Name:
Type: Vented Box
Shape: Prism, square (optimum)
Vb = 160, liters
Fb = 22, Hz
QL = 6,515
F3 = 31,64 Hz
Fill = none
No. of Vents = 1
Vent shape = round
Vent ends = two flared
Dv = 100, mm
Lv = 255, mm

It seems very big :-S

What is the smallest design that has a good response at 20hz?
I think a cube of 500x500x500 should be the greatest size.
The form can be changed, it doesn't have to be cubic, but I think no more than 600 mm height.

Thank you in advance, I know it's difficult :sweat:
 

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Discussion Starter #7
Very, very interesting. I've been making tests with other 10" subs with a 60 litre box tuned at 22 hz and by now, I only got a better response with Alpine SWE-1043E:

Driver Properties
Name: SWE-1043
Type: Standard one-way driver
Company: Alpine
Comment: Type-E series
No. of Drivers = 1
SPL = 84db 1 W / 1 m
Fs = 31, Hz
Qts = 0,62
Qms = 10,48
Vas = 33, liters
Xmax = 13,9 mm
Sd = 330, sq.cm
Qes = 0,66
Re = 3,69 ohms
Le = 0,86 mH
Z = 4, ohms
Pe = 250, watts

Seems much more linear, the RMS is the same and the price is similar also.
Alpine is the line plotted in green, JBL in Yellow.
Cone displacement graph is ok? It only exceeds 0,8 mm at 13,06 hz. Not having to use a hpf would be great :D
In the impedance graph, there are two peaks. I read over internet that this is caused by the resonance frequence of the box. Is it dangerous for the speaker?

Thanks :)
 

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Discussion Starter #8 (Edited)
Ummm it's strange, I'm doing the same test again and the JBL graph is better.

I'm thinking alternative designs for the box, maybe I can go for the big one (some chat with my girlfriend will be needed :whistling:).

Edit: I found why the previous graphs aren't correct, power is limited to 100W. I also updated WinISD to the Pro version and it supports calculating cone excursion and the rest of parameters. I will use it from now on.

2nd Edit: Using WinISD to compare both subwoofers, both give great performance; the Alpine is less linear (better result tuned at 23hz than 22hz), but has an interesting peak between 40 and 60 hz.
[img]http://img249.imageshack.us/img249/6206/jblvsalpine.png[/img]
 

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but has an interesting peak between 40 and 60 hz.
A larger enclosure would cause less of a peak.
Not having to use a hpf would be great
Not using a HPF in a ported design means limiting the input power which would severely affect the performance of the sub. Most sub plate amps have a HPF and are relatively cheap. A 240 watt plate amp would be a good match for what you would like to achieve.
 

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Discussion Starter #10
Ummm I didn't know that. I'll definitely go for the JBL if I can't use a bigger box.
The impedance peak is troublesome or can be ignored?

Again, thanks for the answers. :)
 

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Discussion Starter #12
I refer to this screenshot, but I'm seeing these peaks always I make a design. The frequency changes but there's always one or two peaks. Searching on google people say it's because that's the resonance frequency of the box, but I'm not sure if this has to be corrected or not:



Just as above, Alpine is the line plotted in green, JBL in Yellow (60 liter box, 22hz tuned). But trying any sub shows a peak.
 

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Discussion Starter #14
One last thing and I think I have everything prepared to begin purchasing parts :)

I can't buy plate amps from partsexpress since shipping costs are higher than the product itself.
I found this plate amp at a good price with shipping (if you know any alternative please let me know):

http://www.oaudio.com/300W_SUBAMP.html

It doesn't mention anything about highpass filter, I assume it only has one lowpass filter to cut the top frequency and I'll have to include a separate highpass filter (tuned at around 18 hz). Am I correct?

Thanks :hail:
 
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