Advanced Discussion - Stuffing a horn

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Stuffing a horn

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Category: General
Forum Name: Advanced Discussion
Forum Description: Advanced discussion area for higher lifeforms
URL: https://forum.speakerplans.com/forum_posts.asp?TID=6649
Printed Date: 27 March 2026 at 11:01am
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Topic: Stuffing a horn

Posted By: tommysb
Subject: Stuffing a horn
Date Posted: 27 September 2006 at 1:32pm

Ok, so I've heard that stuffing a transmission line with wool effectively 'reduces the speed of sound', thus making the t-line appear longer, and reducing the cuttoff.

Can one do the same with a horn, effectively making the horn path longer? If yes/no, why?

Cheers,

Replies:

Posted By: gingerbiscuit69
Date Posted: 27 September 2006 at 2:09pm

no ...... thats just plain stupid! would just muffle it and loose DB!

Posted By: adambomb
Date Posted: 29 September 2006 at 10:09am

You are correct about the wadding in a TL slowing down the speed of sound (and absorbing higher frequency sounds)... I have a 2 page paper on the subject if your interested...

Using this theory for horns.. dunno.. I would have thought it would defo work for Scoops (which are of course TLs)... but I have no idea about horns.. in theory it should lower the cutoff.. but I don't really have any experience with designing horns...

Posted By: godathunder
Date Posted: 29 September 2006 at 5:04pm

adambomb, Id be interested in a little looksie at that paper if you have it in electronic form

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LOUDER THAN LOUD

Posted By: kevinmcdonough
Date Posted: 01 October 2006 at 8:08pm

In a reflex box, or in the rear chamber of a horn, then yes like you say the wadding will absorb the sound and slow it down. The sound effectivly thinks it takes longer to reach the sides, and therefore the box/chamber acts as if its bigger than it actually is.

However in the actual horn path of a horn/scoop/TL (or inside the actual path of the ports in a reflex), i would think that it would just block the flow of air and mess things up.

kev

Posted By: tommysb
Date Posted: 02 October 2006 at 6:15am

Definately works in a T-line, i think sheeps wool at a density of 8kg/m3 is recommended, trying to think which book i read it in (an oldie), but i also know someone who's put it into practise, i think his t-line has an f3 of about 17Hz!

Posted By: adambomb
Date Posted: 02 October 2006 at 11:50am

The Loudspeaker Design Cookbook has a few pages dedicated to this...

The paper I have is about the above, but also avoiding standing waves with the enclosure (no panels square to each other, very interesting read)... its just a photocopied article.. so I will have to scan it and post it here for you... might have to wait a bit as my scanner is burried somewhere..

Posted By: djtosco
Date Posted: 03 October 2006 at 5:39pm

The problem is that the stuffing material increases dramatically the losses... thus reducing the efficiency of the horn!!