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Old 21st October 2010, 08:17 PM   #1
Edmunds is offline Edmunds  Latvia
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Default Sub in a small enclosure

Hi all,

I have a sub project with very little space available.

I have a 10" driver that I can squeeze in the space. The enclosure can be a cube around the speaker and a little more, but there is hardly any volume to talk about - probably as much as the speaker takes itself in all four corners combined. I want precise, not boomy sound for classical music, jazz and movies. It does not have to be very loud, although I know it (and the amp) has a potential to be. The room is very small, so there is no way to be physically more than 3m away from the sub.

Is it worth doing at all or should I go and look for 6" driver or something? What about this foam I have read about people put in smaller enclosures? What is the function of it, would it be recommended for my application and where do you obtain one?

Thank you for your time,

Edmunds
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Old 22nd October 2010, 07:16 AM   #2
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For a small cabinet, it would probably be best to use sealed +eq. Ported enclosures tend to be unforgiving of undersized cabinets.

What will you be driving it with?
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Old 22nd October 2010, 08:44 AM   #3
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by Edmunds View Post
Hi all,

I have a sub project with very little space available.

I have a 10" driver that I can squeeze in the space. The enclosure can be a cube around the speaker and a little more, but there is hardly any volume to talk about - probably as much as the speaker takes itself in all four corners combined. I want precise, not boomy sound for classical music, jazz and movies. It does not have to be very loud, although I know it (and the amp) has a potential to be. The room is very small, so there is no way to be physically more than 3m away from the sub.

Is it worth doing at all or should I go and look for 6" driver or something? What about this foam I have read about people put in smaller enclosures? What is the function of it, would it be recommended for my application and where do you obtain one?

Thank you for your time,

Edmunds
Hi Edmunds,

Here is an idea :

b
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Old 22nd October 2010, 09:50 PM   #4
Edmunds is offline Edmunds  Latvia
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Thx, bjorno. Your post looks incredibly valuable, but also complex. Can you possibly spell it out?

I mean, I understand there is some kind of filter to compensate for the distortion the small box would cause, but can you explain what is the distortion exactly? What is the relation between the formulas on top for different enclosures and the circuit below. If I measure my enclosure to be 12L or 8L, how can I go to my resistor and capacitor values? What is the triangular component? Sorry for a dummy question ... And can you really come up with a circuit without knowing anything about the amp? How does that work and why?

Thank you, Chris661 for your reply - ported is not an option. There is just no space for ports, so I decided on closed early on. The amp is a dismantled Z5500. Based on TDA7294.

/Edmunds
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Old 22nd October 2010, 09:56 PM   #5
Edmunds is offline Edmunds  Latvia
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I have actually put it in a small box now and tried it out without the back properly sealed. I put it against the wall, some 1cm off it, but there is plenty of room for air to escape. It is still good sound from the total thing and the sub sounds ... well, ok. It is a bit lost in terms of precision - somehow it feels less accurate. I hope it will get better when I figure out how to seal it - the back is not square. It is also significantly less powerful than it used to be in the big box. On the edge of being too quiet, even if on the max sub output setting.

/Edmunds
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Old 23rd October 2010, 12:22 AM   #6
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I crunched some numbers for you concerning your 10" driver....If you can get a sealed enclosure, stuffed with some Dacron or cotton batting(Pillow stuffing).......at a value of 1446 cubic inches....you will be right smack in the ballpark for achieving the best performance for this driver.
Try different dimensions to suit your space available...trying to hit that number of cu inches.

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Old 23rd October 2010, 07:50 AM   #7
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Here's a little information on the graphs Bjorno posted...

ESP - The Linkwitz Transform Circuit << this explains things pretty well...

The red line is the correction curve applied by the Linkwitz Transform. The turquoise (green-blue) line is the sum of the circuits (there's an infrasonic filter to stop over-excursion at frequencies you'll never reproduce). Below the turquoise line, is the new response of the driver, after the correction has been applied. Bjorno selected ~35Hz as a lower cutoff. You could ask it to go lower, but you start running into serious problems with excursion when you turn it up. The next line down (green) is the high pass filter, which cuts off the really low stuff, and the last line is the bass response before any correction is applied.

Chris
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Old 25th October 2010, 01:12 PM   #8
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by chris661 View Post
Here's a little information on the graphs Bjorno posted...

ESP - The Linkwitz Transform Circuit << this explains things pretty well...

The red line is the correction curve applied by the Linkwitz Transform. The turquoise (green-blue) line is the sum of the circuits (there's an infrasonic filter to stop over-excursion at frequencies you'll never reproduce). Below the turquoise line, is the new response of the driver, after the correction has been applied. Bjorno selected ~35Hz as a lower cutoff. You could ask it to go lower, but you start running into serious problems with excursion when you turn it up. The next line down (green) is the high pass filter, which cuts off the really low stuff, and the last line is the bass response before any correction is applied.Chris
Thank you Cris for a perfect seconding of my simple picture: I've added two pictures that _probably needs more explanations...

b
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File Type: gif Small-Room_Bass.GIF (26.7 KB, 223 views)
File Type: gif Room-bass.GIF (47.2 KB, 217 views)
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Old 25th October 2010, 01:28 PM   #9
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I guess the usage of two subs would put those figures to trash !!!
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Old 25th October 2010, 02:12 PM   #10
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by picowallspeaker View Post
I guess the usage of two subs would put those figures to trash !!!
Not quite right:

b
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File Type: gif Small-Room_Bass_2-drivers.GIF (26.3 KB, 209 views)
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