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Woofers for horns...

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I've read different info on this subject, but would like to try fro some concensus from folks here. Claude and Gil may be able to chime in has well as others.

 

When looking at the T/S parameters for horn loading a woofer, what are the main things to look for, i.e., lower Qts, higher Bl, extra low Fs, etc)

 

That's the info I'm looking to get a handle on. I've got an idea in mind (which shall remain in my head for a while).

 

Bruce

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Depends on where you cross it at.

 

(Fs/Qes)*2=mass corner.

 

For best bass response, pick a mass corner no higher than the crossover point, and maybe as much as a half-octave (0.707) lower.

 

A K33E has a mass corner of less than 200hz.

 

130Avs2226vsLE15A.gif

 

The 2226 has a mass corner about an octave lower than the D130, the LE15A is similar to the 2226, but is 16Ω.

 

The volume of the less efficient 2226 is no less than the much more efficient D130 below its mass corner. Ultimately, the 2226 can play much louder than the D130 because of its greater x-max.

Edited by djk

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Driver roll-off frequency is = 2*Fs/Qes.

 

So Fs/Qes is a "figure of merit" so to speak.

 

The actual Qes can differ (usually higher) from that specified so it should be measured before you start cutting wood.

Fs also varies as a function of position (facing down or sideways) and temperature.  It can also go down after some use.

 

High Fs is a stiff, low-mass cone assy.  Low Qes is high B*L product motor.  

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Bruce,

 

It also depends on the type of horn.  The TS parameters for a front loaded horn are quite different from those for a tapped horn.

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Yes, it is for a front loaded horn. Woofer facing down (hadn't thought of that until John mentioned it). Mostly an exponential, similar to Claude's QP or the MWM.

 

Bruce

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The curves below are from "Kuben" a horn similar to the La Scala horn but in this case using 12" drivers. The measurements was with the horn on a table and on axis on about one meters distance. Upper trace is Beyma PA driver Fr about 60 Hz and Qes of 0.2 a typical good horn driver. The lower trace is a Bulgarian Gamma Gamma 1231 driver, light cone very soft suspension and quite high Q (25 Hz 0.42 Qts and 340 L Vas) so the mass corner frequency is about 100 Hz.

Gamma1231-80cmTable.png

 

For PA use the beyma is far better more output by far for the same voltage and greater powerhandling as well. For domestic use a trade off between relative bass output and sensitivity might be scewed in the oposite direction. I am not claiming that frequency responses are everything, they have to sound good as well.

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