The best position for a new woofer in an existing tower - diyAudio
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Old 3rd November 2016, 06:20 PM   #1
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Default The best position for a new woofer in an existing tower

Hello, for a strange set of circumstances now I have to install a subwoofer driver in a existing bottom part of a tower in which there already is a passive radiator (before woofer was mounted internally in a 4th order bandpass configuration, that I don't like anymore..). What's in your opinion the best position for the subwoofer between the four possibile as illustrated here? And if possible, why?

where woofer.jpg

Thank you very much.
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Old 4th November 2016, 09:41 AM   #2
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In other words, is there some kind of real benefit placing a frontward firing subwoofer driver near to the floor? As it happens for a downward firing one?
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Old 6th November 2016, 08:23 PM   #3
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Thanks for the interest. I do not know the circumstances, say where the other drivers are spatially and acoustically, but i usually place everything intended to sound as one as closely together as possible. So i would let the big one, too, face the listener and have it just below the squawker or wideranger.

One can set distance between sound sources in order to flatten listening chamber effects: Say one woofer is 70cm above ground, causing a dip at 344/0.7Pi and pronouncing a chamber resonance at 344/1.4. Now one places a second woofer at different heit, not directly on ground or any other Klingeldruck, for that would also fuel 344/1.4, but at 0.2m to 0.35m, around 1.05m, 1.75m, ..., say around the Klingelschnelle.

This is a another reason to use flat filters or even add a fullrange mono box to a two-channel setup. You must be doing something rait, if i can think of sounds and voices.
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Old 6th November 2016, 09:10 PM   #4
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If it is a subwoofer, and is not crossed very high, it makes little difference where you put it, down that low everything is omnidirectional. It should be close enuff to the midbass that the C-C sphere distance is less than a wavelength.

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Old 6th November 2016, 09:49 PM   #5
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Thank you very much, so it remains one question for me, why we can say a downward firing sub is better than a frontfiring one, even placed nearly to the floor?
Somebody said to me that a down firing driver emits in a half space and so +3 dB. Is it just an urban legend? And does a front firing near to the floor emit too in half space or not?
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Old 6th November 2016, 09:57 PM   #6
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Sorta of. The wavelengths are so long that placed anywhere near the floor the woofer will be radiating into half-space. You are going to want to use an active XO here, so the level gets set with the gain control on that amplifier. And down this low the room dominates.

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Old 7th November 2016, 12:40 AM   #7
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So doesn't my sub driver placed at 25 cm high or at 45 cm high from the floor make difference in terms of efficiency in the extreme low end..? Of course placed at 45 cm closer to the mid-bass should be better in terms of its high end and blending with the rest..
Thanks.
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Old 7th November 2016, 12:46 AM   #8
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Just as an aside, what about the existing bass driver? Are you modding the box to give it it's own enclosure? It won't play well if it's sharing the same volume as the new sub...
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Old 7th November 2016, 01:16 PM   #9
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Quote:
Originally Posted by pinkmouse View Post
Just as an aside, what about the existing bass driver? Are you modding the box to give it it's own enclosure? It won't play well if it's sharing the same volume as the new sub...
Of course.. two Tang Band W8-2022 will replace the existing Peerless 830667 in their 4th order bandpass configuration placed in 28 liters (13+15) of total exclusively dedicated part of tower enclosure, becoming a normal 28 liters vented box.
This not because I don't like Peerless, which worked well even in such a so small and extreme configuration, but because of its 4th order bandpass configuration, which gave me too many problems, both in passive and in active mode.
With a vented system, if passive will work bad I'll be ever able to insert an active module.
I've choosen Tang Band because it's a shallow sub, whose simulation gave me optimal results in just 28 liters of enclosure.
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Old 7th November 2016, 10:48 PM   #10
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Just checking.
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