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In the Forum: Horn-Loaded Speakers
In the Thread: Macondo’s Midbass Project – the grown up time.
Post Subject: They are very simplistic and primitive things but...Posted by Romy the Cat on: 9/1/2010
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 jessie.dazzle wrote:

Romy wrote:

"...Let pretend that you play a normal some kind of horn with a lot of air in it. The air drives the driver impedance down..."

I'd like to understand this; correct me if I'm wrong:

As soon as the membrane of a horn-loaded driver starts to move, that membrane sees the air mass located in the horn as a load. Because the air inside a horn is confined by the walls of the horn, this load will be greater than what the membrane would see if operating in free air or as a direct radiator. The result is a pressure inside the horn fluctuating between greater and lesser than normal atmospheric pressure outside the horn; the difference being most pronounced at the throat of the horn. 

It would seem fair to say that this load physically "impedes" movement of the membrane, and that a horn-loaded driver will experience greater resistance to movement, or greater physical impedance than would an identical but non-horn-loaded driver.

Are these conclusions correct? If they are, then does that increase in physical impedance equate to an increase in electrical impedance as seen by the amplifier? If so, can it not be said that "driver impedance" has in effect been increased by the load (the air in the horn)?

jd* 

Yes, those conclusions correct, what you described is called throat reactance. I am not sure what you mean in the last paragraph as electrical impedance as seen by the amplifier is slightly deferent thing.

Do you remember years back John Dunlavy in these largest speakers glued to the bass driver some pieces of plastic? He did it as he did not have drivers (did not want to pay for them) with low resonance frequency, so he added mass to the driver’s cone in order to drive the resonance peak down. A driver loaded to a long horn does the same. The driver has a diaphragm of let say 100g and the mass of the air in the belly of the hone is attaching itself to the mass of the diaphragm. However, the driver does not see the let say another 30g of air in the horn but he sees it through the throat. It is like you do not “see” a liquid in a cap but you see it only through a straw.  What we do is balancing the reactance of the diaphragm to this affect by creating a strong damping, of by creating a dynamic low pressure zone behind the diaphragm that add the contra-puling force to the driver’s own suspension. As a result the driver and the horn become to be tuned to each other, like properly calibrated transmitter, transmission line and antenna. Sure the physics is deferent but the result is very much the same - a balanced system that is able to perform own tasks at max capacity of own topology.

BTW, I have written about it many times. If you remember when I was bitching about Goto/ALE drivers and called all of those people who use compression bass drivers as “ignorant armatures” then it was exactly what I meant. None of the compression bass drivers have provision for resonance frequency modification and the companies who do them do not acknowledge it as a problem. I typical audio Moron pays a lot of money for those expensive drivers and loads them in his own custom horn. Where is the throat reactance and where is the resonance frequency of this tandem no one cares or knows. People report that they like sound but they are absolutely clueless if the driver-horn are operate at it’s optimum. They might be good driver and they might be useful horns but the “ignorant amateurism” that those people demonstrate suggest me do not take those people’s positive feeling seriously. It is like to get a good vintage cello, play it, to report that it is a wonderful instrument but never tune the cello…

If you look for my old posts that you will recognize for years that taking about bass horn users the disregard by those people the time alignment, throat reactance and smart integration patters always suggested me that I need to take the person/installation seriously. They are very simplistic and primitive things but even they are not take care in most of the cases.

Rgs, Romy the Cat
 

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