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Multi-Way Conventional loudspeakers with crossovers

What can I do against 'box sound' ?
What can I do against 'box sound' ?
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Old 11th September 2020, 05:36 AM   #1
alujoe2 is offline alujoe2
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Default What can I do against 'box sound' ?

Hi,

if you play a driver without a baffle or on an open baffle the sound is 'open', as soon as you put the driver in a box there is this 'box sound' (sorry for my English). Is there a way to get the 'open' sound from a boxed driver ?
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Old 11th September 2020, 06:21 AM   #2
nigelwright7557 is offline nigelwright7557  United Kingdom
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You could try damping in the box.

The worst speakers for "box" sound are W bins where the sound bounces off the back panels before it comes out the front.
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Old 11th September 2020, 06:24 AM   #3
Zvu is offline Zvu  Serbia
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@Alujoe2 That "openness" could be due to two things:

1-Driver having no cabinet so no wall resonances
2-Driver being mounted OB radiates high frequencies behind and you are picking up that as reflected energy with enough delay to perceive it as euphonic.

First you must pinpoint what is it of these two that you really like (possibly both).

-Wall resonances can be handled effectively with sandwich walls (a cabinet within a cabinet) with a layer of sand in between.
-For backward radiation you can add another driver to the back of the boxed loudspeaker to get that figure 8 radiation pattern.

That is if you insist on boxed loudspeaker after you confirmed you like the sound of unboxed one.
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Last edited by Zvu; 11th September 2020 at 06:28 AM.
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Old 11th September 2020, 06:50 AM   #4
chris661 is offline chris661  United Kingdom
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Cabinets suffer from two issues, typically in the hundreds-of-Hz range:

- Internal reflections
- Panel resonances

Bracing and damping will remedy both of those problems, so we only hear the driver itself.

Chris
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Old 11th September 2020, 08:06 AM   #5
TimA is offline TimA
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I line the insides with ceramic floor tiles or stone. 3/4" thick stone makes for an incredibly inert cabinet and can be stuck on simply with PVA. A cheap or sometimes free source is old fire place surrounds...usually closer to an inch thick though so weight can be an issue. The audible improvement with either is substantial. My latest 2-way build uses ceramic tiles on the inside of the cabinet which tapered towards the back where there is an aperiodic port directly behind the driver which allows most of the sound reaching it to escape. The driver response still reaches low enough to where a subwoofer takes over. The tweeter is an open backed AMT sitting on the top and the whole sound is very open and very clean.
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Old 11th September 2020, 08:15 AM   #6
alujoe2 is offline alujoe2
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Quote:
Bracing and damping will remedy both of those problems, so we only hear the driver itself.
I admit bracing and damping improve things, but IMHO it is not a cure - only half way there. At least I never heard any boxed driver that came close to this 'not in a box sound'. Why do I not use a dipol, well, I like the impact of the boxed drivers .
For a driver working 200Hz-1.2kHz in the usual closed box, are there any better enclosures like TL or aperiodic or whatever else ?

Quote:
Originally Posted by TimA
The tweeter is an open backed AMT sitting on the top and the whole sound is very open and very clean.
I never tried it, but I was told integration of dipol and boxed speaker is problematic. Can you please be so kind and tell me what drivers you used and how you did the crossover ?
I am also very interested in how you did the aperiodic vent.

Last edited by alujoe2; 11th September 2020 at 08:22 AM.
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Old 11th September 2020, 08:27 AM   #7
scottjoplin is offline scottjoplin  Wales
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There is the issue of diffraction too, not sure if this is part of "box sound", a box or baffle often doesn't help
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Old 11th September 2020, 08:48 AM   #8
TimA is offline TimA
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The tweeter is a Mundorf AMT 2340 and the woofer is a Seas U22, not the standard version but a sample version with a heavier magnet but otherwise very similar. The crossover is electrical 2nd order at 3kHz designed in Xsim using real measurements from a prototype I knocked up as I wasn't sure about the hybrid approach and whether it would work. I had intended it to be a 3-way with open baffle midrange but found the crossover design, specifically the phase tracking through crossover, too difficult to achieve the results I was looking for. I'm now glad to have gone for the 2-way hybrid. Driver integration is excellent subjectivity, in fact it's the first thing my piano tuner friend commented on when hearing them.
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Last edited by TimA; 11th September 2020 at 08:51 AM.
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Old 11th September 2020, 09:06 AM   #9
alujoe2 is offline alujoe2
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@TimA

Thank you very much ! Please allow me more questions:
1) How did you design the aperiodic port ? Are their any formulas (size etc.) ?
2) How did you make the aperiodic port ? Compressed Rockwool or whatever ?
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Old 11th September 2020, 09:21 AM   #10
TimA is offline TimA
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The vent consists of gutter mesh inside and outside with roof insulation between. In this case uncompressed to allow more sound through. Simulations of the vent were done on winISD with Ql (box losses) set to about 2.5 and later confirmed through impedance measurement looking for a lowered peak as per simulation. I have seen guidelines somewhere for a minimum vent size relative to driver radiating area but in any case adjustment is done by stuffing density.

Last edited by TimA; 11th September 2020 at 09:29 AM.
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