All drivers have eigenmodes with its surround affecting its acoustic properties, so for a driver with an accordion surround being the most benign, the frame size gives a good approximation of ~450 Hz/15" and a bit higher for rolled surrounds for its fundamental dip, so maybe one reason why the pioneers standardized 500 Hz XOs for 15".
GM
Later generation (though already 8 years old) TD15M in a sealed box, as measured by John Janowitz.
The two dark curves are 1m ground plane. One is done with a chirp tone and one with mls tone. The light green curve is 1m non-ground plane measurement.
The two dark curves are 1m ground plane. One is done with a chirp tone and one with mls tone. The light green curve is 1m non-ground plane measurement.
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Response of one of my 15" woofers mounted on an IEC Baffle.
The dip is also visible with other drivers from the same manufacturer mounted on the same baffle,
but it largely disappears once the driver is mounted in a cab.
The dip is also visible with other drivers from the same manufacturer mounted on the same baffle,
but it largely disappears once the driver is mounted in a cab.
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Here's another 15" midwoofer.
Left is on IEC Baffle, right in 80L cab.
Left is on IEC Baffle, right in 80L cab.
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That midrange dip is present in a lot of of data sheets of Beyma drivers - mine as well for instance.
I wonder how a TAD 1601 fares in this respect.
Regards
Charles
I wonder how a TAD 1601 fares in this respect.
Regards
Charles
Here are groundplane measurements of our midbass horn. No EQ was applied. First graph is with 1/24 Oct. smoothing and JBL 2220. The JBL driver has a resonance in the 600-700 Hz area for some reason. Second graph is an overlay with a second JBL 2220 driver (blue) and B&C 15FW76 (green).
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Depends on the driver and what level you do define as "loading".
With a custom 15" driver we can remain the level much higher as seen in the simulation.
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The force flat feature in WinISD has proven its worth. The AE15m can do the task by its self, let alone with 2 in use. Its almost identical to the jbl 2216nd in excursion, though the jlb has only slightly lower excursion, higher xmax, and way higher group delay in the bass. 2 -15M's, ported sounds like a great idea. I'm not sure how I like the mtm design for such big drivers but where there's a will there's a way. The 15m uses less power and excursion through out the bandwidth in comparison to the 15H, which has slightly better group delay. Whether stacked vertically or horizontally the sweet spot is going to be bigger for the woofer section. Horizontal makes the most sense for a mtm with horn, if I'm trying to keep size down, you'd think I'd position the woofers as close as possible with the horn on top of the triangle, sorta like a bridge between two-way and mtm configuration.
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Bjorn, isn't there a slot in your midhorn?
That might explain the 'steps' in the response.
I guess there is.
That might explain the 'steps' in the response.
I guess there is.
An externally hosted image should be here but it was not working when we last tested it.
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(Supposed) elliptical Tractrix:
An externally hosted image should be here but it was not working when we last tested it.
2x15M will do, I think.
If you go horizontal the triangle makes sense, this will probably work best for nearfield listening.
I am not sure about these woofers angled inwards :
The advantages of a dual 15M may outweigh those of 15M + 15H.