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In the Forum: Horn-Loaded Speakers
In the Thread: The European Triode Festival’s horns
Post Subject: The Musique-Concrete bass issues.Posted by Romy the Cat on: 12/18/2007
I visitor of my site shat me an email informing that that above depicted horn installation by Marc Henri and Andre Klein was made French Musique-Concrete company. I do not know a lot about those people, beside that they hand around Jean Michel Le Cléac'h. The Musique-Concrete has web site with English section:
Do not miss their “Material selection” page:
Where they very rational and very sensibly go over the horns material and finish. The Musique-Concrete has popped up at this site: they build hors for Rony Weissman:
Anyhow, my comment in this article is about the above depicted installation Musique-Concrete presented at European Triode Festival. Among many “issues” that I see in this system (like use of 1kW push-poll amp to drive the horns, like the way tweeter is used, and few othersthings) I would like to concentrate on one the Musique-Concrete bass solution. As I said in my previous post what Musique-Concrete does is not a mistake but rather a disputable direction. I happens very disagree with entire Musique-Concrete bass direction and the purpose of this post is to voice my view on the subject as it is a very common false direction for many horns installations.
If your look at the page with various systems where Musique-Concrete used:
then you will see people employ many solution to compliment the Musique-Concrete with bass: sealed enclosures, ported, bass horns, Onkens. Musique-Concrete offers own solution in a way of bass horn (image is courtesy to Jürgen Ewert at http://ircaudio.thor.prohosting.com/etf07.htm):
I never like that type of the horns and I consider them fundamentally faulty. Let look deeper. The Musique-Concrete horn looks like 250 Hz -300Hz horn with 2” throat. Let presume that it crossed at 500-650Hz, let do it 500Hz for a love or round numbers. I personally do not feel that it is possible to have one front radiating channel that would cover from bottom to 500Hz but my lock of believe should not be impediment to others to try. The Musique-Concrete use, it looks like, 55Hz-60Hz horn loaded with two 15” or 18” drivers, used (once again: it looks like) with open back. It looks sexy and it rocks the boat of people who “love horns” but … I feel that those horns are very poor and they are in fact are the bottle neck this Musique-Concrete installation.
In a horn the most important category is the ratio between the mouth and throat. This ration of the Musique-Concrete’s bass horn is truly pitifully. In this configuration, with such a huge throat the drivers act as a pure open baffle direct radiators and then “see” the horn as no lower than (in my estimate) 250Hz. So, the Musique-Concrete bass horns works fine (I hope they parallel the drivers) down to 250Hz, then the horn EQ stops and the drivers drive the room as direct radiators. To serve the 250Hz horn the driver should have primary resonance around 150 Hz -200Hz but with this resonance they will be worthless as direct radiators. So, people usually stick in that type of “horns” the horns drivers with resonance of 50-60 or even the 515B-type of driver with resonance or 25hz. They presume that with lower bass from the driver then will have more bass out of the horn. However, the horn can’t traduce lower bass then the horn rate. So at 55Hz-60Hz the horn want to cut the response but it cannot as the throat is stressed with excessive pressure of pounding LF drivers. So, the horn got choked with LF pressure that destroyed bass quality tremendously. I have heard a number of those attempts – all of them sound horrendously bad, screwing with barbaric upperbass pressure the much higher frequency region. (It is what some of the cretins that I know call the “reputed vintage sound of moves theaters form 30s”)What is necessary to do in this situation is to run a high pass filer at I would say 200Hz, unloading the evil bass from the horn, and since they use two drivers I doubt the they would be able to go away with a simple 6dB/octave crossover. Sure, but then the bass horn will have no bass? Or course it will not. Then would need to place another channel, something that I call “open bottom channel”, the channel that would not have intrinsic LF limitation built into the topology
(Look for open bottom explanations in here: http://www.goodsoundclub.com/Forums/ShowPost.aspx?postID=3663#3663)
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