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Old 5th January 2006, 02:09 AM   #1
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Question Subwoofer for ROOM. Sealed or Vented?

Hi !!

I made two GainClone amps (3886) that will drive four 3,5" 20W 4Ohms speakers, with 300Hz of frequency cut (300 - 20.000hz).

http://www.diyaudio.com/forums/showt...360#post806360


Now, I'm gonna make an c200 amp that is 200W RMS, but it will run with lower voltage, so, it will be around 100 ~ 130 W. This amp will drive a 12 inch 125W 4Ohms Subwoofer.

The Subwoofer will be cutted at 300Hz with an Active crossover (like the speakers), from elliot's page.

I want SMOOTH and EXTEND bass, nothing noisy pleeease !
I choiced the 12 inch sub, because I don't want any distortion, so It will be (I hope so) able to deliver the bass that I want, with low volume, so, none distortion, lower heat, lower power consuption...

As I said, I DO NOT want hard and noisy bass, I do not want sound pressure ! I want the most plain frequency response possible from 20 to 300hz

I want Sound Quality, to listen Blues, Jazz, Classical and etc.

The room isn't small, but isn't that big too...

If you think that 10 inch sub is enough, please, tell me !

I know I have many questions, but the first is: Vented or Sealed?

edit: Oh ! How could I forget? :P

Subwoofer specifications:

125W RMS
4 Ohms
4Kg
- Fs (free air ressonance): 26.5 Hz
- Qts ("Q" total of the sub): 0.5086
- Vas (equivalent conformity): 4.44 PC / 125.36 L
- Recommended Current Power: 40-125W
- Deslocated Volume (cubic foots PC ): 0.057 PC / 1.6 L
- Qes: 0.5281
- Qms: 13.81
- Sd: 0.0523 (m2)
- Re: 3.4 (ohm)
- Xmax: 7.50 (mm)
- Sensibility: 87 dB (1watt/1meter)
- BL: 10.88 (N/A)
- Zo (Maximium Impedance): 92.3 (ohm)
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Old 5th January 2006, 02:41 AM   #2
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Just posted on your other link! (use this one for future subwoofer stuff - you'll find more experts!)
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Old 5th January 2006, 07:46 AM   #3
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I think that you will need stereo subs because you are cutting in far too high at 300Hz.

The sub you have chosen has high Qts so you will be limited to sealed box use. That to me says you need to use a Linkwitz Transform to get the sound you want from the box size you are happy with.
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Old 5th January 2006, 11:12 AM   #4
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Hum...

This subwoofer they use in vented box too, but in the car, and this is an "automotive" subwoofer... This sub is very used for SQ here.

But can I get extended and smooth bass with a SEALED box ?

How many litres do I need?
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Old 5th January 2006, 11:28 AM   #5
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That sub and a vented box are not SQ friends, according to theory at least. They may work in a car application.

As I hinted before, take a look into Linkwitz Transform, there is plentiful information on the web and this forum.
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Old 5th January 2006, 01:45 PM   #6
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by -_nando-_
How many litres do I need?
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File Type: jpg 12sub.jpg (69.6 KB, 302 views)
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Old 5th January 2006, 03:08 PM   #7
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IS IT 125 and 200 LITRES??

Can you sugest me a better subwoofer (for home use) and cheap ?

I'm taking a look about linkwitz transformer around the forum
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Old 5th January 2006, 03:26 PM   #8
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Yes those boxes are massive due to the high Qts as I said.

A Linkwitz Transform will be your friend provided you have sufficient amp power and voice coil thermal capacity. I think you might be cutting it fine. You need to do some modelling of power handling and excursion in different box sizes.
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Old 5th January 2006, 03:31 PM   #9
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by -_nando-_
IS IT 125 and 200 LITRES??

Can you sugest me a better subwoofer (for home use) and cheap ?

I'm taking a look about linkwitz transformer around the forum
Yup, 125 and 200 litres according to the specs you posted,
main cause is the 125L Vas of the driver.

Personally i'd go for two seperate subs with 300Hz c/o frequency.

Not sure what drivers are available in Brazil,
not much as far as I could tell when I was there.

If you can get them two Tangband 8" drivers would be good :

http://www.partsexpress.com/pe/showd...number=264-833

note the Vas of 18.5L.

/sreten.
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Old 5th January 2006, 03:35 PM   #10
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I need something like 40 ~ 60 litres

I'm reading this article:

http://sound.westhost.com/linkwitz-transform.htm

Look at the attachement ! It's a 43L Sealed box, and the frequency response is okay for me...

This sub costs to me (only the sub, without box) just 180 reais, that is 74 US Dollars... Cheap don't you think?

Well, you can suggest me a better sub, but around this price too heh !

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