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Old 26th January 2008, 07:11 PM   #1
jay1st is offline jay1st  France
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Default BR vent and walls......

This may sound stupid,

But for speakers which are supposed to be very close to a wall, is it better to have the BR vent on the front of the speaker's cabinet ?

And does it change the response moving it from the back to the front ?

Tnx......
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Old 26th January 2008, 07:58 PM   #2
Svante is offline Svante  Sweden
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The short answer is that it does not matter.

There are a few things to think about though.

If monted on the back, there has to be enough free space between the box and the wall, otherwise, the tuning will be slightly lowered if it is too close to the wall.

If monted on the front, close to the driver, pipe resonances in the tube will appear stronger due to the closeness.

There are other even smaller differences too.
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Old 26th January 2008, 08:04 PM   #3
jay1st is offline jay1st  France
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OK, tnx for the reply.

I guess the best is to experiment.
So I'll build 2 different cabinets and "hear" how different they sound and keep the one the suits me best.


Btw, what do you mean by "
the tuning will be slightly lowered if it is too close to the wall " ?
The frequency will get lower ?
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Old 26th January 2008, 09:16 PM   #4
Svante is offline Svante  Sweden
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Quote:
Originally posted by jay1st
Btw, what do you mean by "
the tuning will be slightly lowered if it is too close to the wall " ?
The frequency will get lower ?
Yes, the tuning frequency will be lowered if the passage on the back side is narrow. It is somewhat like lengthening the tube. But unless the box is really close to the wall, the change is small.
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Old 26th January 2008, 09:23 PM   #5
jay1st is offline jay1st  France
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Ok and tnx a lot.

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Old 27th January 2008, 02:04 AM   #6
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Along this same line of thought could a pair of small bookshelf speakers be ported out the bottom to give a little lower freq? Like if feet were incorporated into the box design lifting the bottom of the box 1.5 to 2" from whatever the speaker was sitting on?

I found these super cool oak carved feet like the eagle talons and lions paws on balls you see on older hutches and furniture. I thought it would be fun to put these on a small bookshelf size speaker with some tiny crown molding on the edges for a classic look.
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Old 27th January 2008, 10:01 AM   #7
ente is offline ente  Germany
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Default tiny laser measurements

... just to give an idea about the effects here a small experiment with a laser and STEPS from the ARTA family.

You see the DISPLACEMENT of the membrane. The dip is the tuning frequency of the box.

Some additional data:
- diameter of the port = 5 cm
- Size of box 45 x 26 cm

Click the image to open in full size.

red = 1m, blue = 9 cm, green = 4 cm, black = 2,5 cm from backwall

Regards
Heinrich

PS: new ARTA release at the beginning of march
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Old 27th January 2008, 06:22 PM   #8
Svante is offline Svante  Sweden
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Default Re: tiny laser measurements

Quote:
Originally posted by ente
... just to give an idea about the effects here a small experiment with a laser and STEPS from the ARTA family.
Cool!
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Old 27th January 2008, 08:40 PM   #9
jay1st is offline jay1st  France
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That is way cool, thank you !

So, to be short, getting to close to a wall will modify the low end frequency response on the loudspeaker by increasing it's ability to go lower.

I guess it's one of those cheap tricks to make a small speaker go lower ?
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