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| Re: Definimax 4012HO - End of Life [message #90842 is a reply to message #90826] |
Sat, 07 September 2019 09:41   |
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Wayne Parham
Messages: 18783
Registered: January 2001
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Illuminati (33rd Degree) |
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Mudshark wrote on Wed, 04 September 2019 15:43Thanks to Symphonimind for suggesting the Delta Pro 12A which I'm sure is an substantial improvement. I don't mind paying a bit more for the B&C if it's significantly better. If there's any way you can help in quantifying the difference in sound quality between the two to help in making a choice it would be much appreciated.
See the following link:
This shows what shorting rings do and what you can expect from them.
Mudshark wrote on Thu, 05 September 2019 08:24I found that the H290C waveguide rings like a bell when you hold it by the flange and rap it with your knuckle so I damped the two larger sides with triangles of 5mm Dedshete and it's now completely inert, so that's my DE250 setup.
Of course there is never any harm covering the waveguide with damping material, but the bell mode of the H290C is well below the passband of the device, being approximately 420Hz. And the amplitude is very low when the waveguide is mounted in the cabinet.
It's kind of like standing waves in a small subwoofer cabinet - They line up at high frequencies, above those which are presented to the cabinet. So but it never hurts to add fiberglass insulation inside a subwoofer and it also sure can't hurt to cover a waveguide with plumbers putty or other damping material to reduce the bell mode even lower than it already is.
Unmounted H290C 420Hz Bell Mode
What I've found is the amplitude of the 420Hz mode of the H290C drops considerably when it is mounted on the baffle. It sort of sounds like the frequency drops too, because it sounds so muffled. But in fact, the frequency is about the same. Mounted or unmounted, the bell mode is approximately 420Hz. But the amplitude drops considerably when mounted.
So the excitation frequencies are over an octave above the bell mode. Of course, it "lives" in the same cabinet as the midwoofer, which does generate 420Hz signals. So it is good that the bell mode amplitude is low when mounted. And I don't see any anomalies in the loudspeaker's response chart around 420Hz, so the bell mode is undetectable and inaudible. But your damping material will decrease bell mode amplitude even further.
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| Re: Definimax 4012HO - End of Life [message #90843 is a reply to message #90415] |
Sat, 07 September 2019 17:15 |
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Wayne Parham
Messages: 18783
Registered: January 2001
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Illuminati (33rd Degree) |
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I spent a few hours today evaluating the Delta Pro 12 and found it to be a good drop-in candidate. So those of you that were interested in this driver - You can pull the trigger.
I was going to measure the 12PLB100 first, but the interest here for the Delta Pro 12 pushed me to measure it first. That and the fact that I didn't have to run the router to get it to fit.
The frequency response looks almost exactly like the Definimax 4012HO using the same crossover components. The Delta Pro 12 almost looks like it is a Definimax minus the shorting ring. The cones are a little different, but response is smooth between 600Hz and 1.2kHz, so the cone is well damped. The basket is the same and the magnet looks the same from the outside, although it's different internally. Still, all-in-all, I'd say the Delta Pro 12 is very much like a Definimax 4012HO sans Faraday ring. So for those that are wanting the Delta Pro 12, use the crossover components shown on the schematic for the Definimax.
I used the ICD in the WTPro system to evaluate the driver with various crossover topologies. Then I ran it with the same physical crossover used for the Definimax 4012HO. The main thing I was looking for was clean on-axis response and vertical nulls in the right positions, which are approximately +/-25°. In those respects, the Delta Pro 12 looks almost exactly like the Definimax 4012HO.
You can see what I was looking for in the thread called "Crossover optimization for DI-matched two-way speakers." There's a link to a video in that thread that shows the exact process I was doing today.
I'll do the same thing tomorrow to learn if the 12PLB100 will work, and if so, what crossover components it will need. Then I'll modify the crossover schematic to list the new drivers and the crossover components required. I'll post here when I do, so stay tuned.
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