Again not a minor change!Originally Posted by Zilch
Green= 0.08mH
Yellow=0.04 mH
The green curve would suit our project better? Does it?
Again not a minor change!
Green= 0.08mH
Yellow=0.04 mH
The green curve would suit our project better? Does it?
Shame on them! This is far more then production varaition.
I should wait with buying the drivers until they installed a QM System
Maybe one is a 2430 and one is a 2431? Gluing wrong labels
2431 should have better HF extension as Giskard mentioned.
No, go ahead and get your drivers! They'll run nicely on your P-Audio horns for now. We need independent confirmation of what is "right" here, and whether it comprises a significant upgrade over the prior "standard." I am confident JBL will make good under warranty coverage, once confronted with the problem.I should wait with buying the drivers until they installed a QM System
There's also the subjective side to this. I'm VERY interested to know how this combination "sounds" to others. If the HF extension is there, it's not being pushed nearly as hard as prior approaches, and it should be smoother, with reduced distortion. Also, if the Al diaphragm is behaving pistonically to higher frequencies as the Be one is alleged to do, the character of the sound should be much improved.
No more tweaks until we get driver curves completed, then. This sounds mighty good, as is. I doubt they'd have made these crossover changes from the published schematic unless they had production variables under control and a statistical basis for doing so. The changes seem to be a refinement that reduces the HF "push," which is good.
[I AM gonna add bypass capacitors to the crossovers, tho....]
Maybe one of them is a 2435?
- just which of the pictures ( & in what post ) display the drivers FR variations ?Note 2431 driver variability. It could be the horns, but I doubt it.
Edit: It's the drivers. I swapped waveguides.
Thanks
Hi, Earl!
On the previous page, look at the HF extension in post #255, left vs. right driver. Right is the presumed "good" one. It shows in earlier posts as well and was mentioned there. I've seen it under enough conditions now to be satisfied the difference is real, i.e., not a room or measurement anomaly. And it's not the waveguide. I swapped those yesterday to check.
I have more drivers on order to determine how they "should" perform, but the one with less HF does poorly below 2.5 kHz, as well. I doubt that anyone without an RTA or substantially more discriminating hearing than me would know the difference, though.
Oddly, though, the pair of 2435's I have (bought off eBay, of obvious dubious history and lineage,) don't have that good HF extension, either, but they at least play well in the 1 - 2 kHz range.
The posted images as seen from my browser, with this screen resolution , using this size monitor ;left vs. right driver
- displays 4 images, in a vertical row / top to bottom /
ie
- there is no left to right for the ordering of the images. .
Earl: Look at the beginning of that post where I listed what's shown. First two are left, and second two are right, each with phase reversal. See how they are performing at and just below 20 kHz?
Curiously, the "better" one was final tested in 2/04; the "defective" one, later, 5/04. We'll see....
Got it ,,, Thanks !
You know, I think my mild case of dyslexia prevents me from registering these things "the first time" .
Or else, I'm enjoying a "seniors moment".
Zilch, as I want to rebuilt the AM.. xovers, could you do me/us a favour and measure the DCRs of the inductors of the HP out of the circuit?
Oh and is the DCR of the 2431H really 4.4 ohms?
Would be GREAT
Stupidly, I unsoldered them for Mr. Widget to read the impedance, but neglected to measure the DCR. Been meaning to do that again, of course....
[I go do it now....]
Drivers: 2431 = 3.9, 4.0 Ohms, 2435 = 4.1, 3.8 Ohms
L1: 0.228, 0.225 Ohms
L4: 0.052, 0.050 Ohms
Measured at 400 mA DC, i.e., 90 and 20 mV drop, approx., respectively, with 10 Ohm precision source resistor dropping 4V
Both 0.375" square laminate core, 1.70" long, 20 AWG (.035" O.D. enameled)
I'm not finding equivalent air cores; somebody gonna have to help us out, here
R1 is 25 W
Caps are "No name" generic OEM mylar, looks like
No bypass caps
I installed 0.01 uF metalized polyester (mylar) bypass caps to no perceptible effect. Parts Express is B/O on their film & foil polypropylenes right now, alas....
We need to put together a parts list for building both sections, with complete specs and sources, so we all build much the same thing. Clearly, in doing that revision (2.5 Ohms, 0.040 mH), somebody said, "Oh Hell, just make it flat shelf...."
Don't know how they're gonna play together, either. I am biamped....
Thanks Zilch!
Was it 2 Ohms or 2.5 ohms?We need to put together a parts list for building both sections, with complete specs and sources, so we all build much the same thing. Clearly, in doing that revision (2.5 Ohms, 0.040 mH), somebody said, "Oh Hell, just make it flat shelf...."
Lemme check again....
2.5 Ohms, 25 Watts.
Got your drivers yet?
Mr. Widget came over for a listening session. He still likes "real" 4430's best here.
I'm the first to admit: when you mate 2344(A) on 2426H with N3134, something magical happens. It's tough to beat.
[Wish David Smith would tell us what.]
Widget's SO good at this, he could predict the RTA curves before the pink noise even came on.
[Who else would insist you get the left and right channels correct before listening further?]
I'm working on his suggestions now....
Not to worry. Just comparison testing.
Tweeters permit grossly exaggerated sizzle, tho.
[Thankfully, UltraCurve takes it right back out.]
My primary interest is in assessing HF extension, but the virtues of two-way are immediately apparent. This is one muddy sounding 12 dB/octave crossover mess by comparison. 3110A and 3105, 2426J and 2404H-2 (2402 diaphragms).
Results: It augments 2426 without boosting it beyond normal CD compensation, is all, though it's nearly impossible to set correctly, even with RTA, since with cascaded crossovers, the 3110A CD "boost" is applied through the 3105 to the UHF as well. Do 2404H ring radiators want CD boost? ACK!!
Need 2405 diaphragms for it to actually DO anything more than 2431H, apparently....
Hi Zilch,
we're still waiting for the response and impedanced curves of raw 2431 right?
I have ordered my 2431 but the didn't show up. Today I'll order the components for the AM HP network. Maybe I'll try biasing.
Could you please measure the necessary baffle cutout and position of mounting holes of the PT Waveguides?
I still hope to get the horns with your help
Yes. As you know, one of my two units is not performing up to par. I have two more on order (along with your horns), and when I receive those, I'll take them all over to Mr. Widget for measuring so we can get some statistical indication of what they are (or should be).
While I have not yet mounted any, I do have the factory gaskets for them on order, which I would use as template for cutting the baffle opening.
The horns measure 12 x 12 inches, and the cutout needs to be 0.75" smaller all around, so 10.5" square, with 0.5" radius at the corners.
There are 3 mounting holes on each side, 12 total, all 0.375" in from the edge, one on the centerline, and the other two spaced 3.875" out in each direction.
They mount with #10-32 pan head screws according to the AM tech sheet. There is no boss, countersink or counterbore on the horns themselves, just flush on the face.
[I don't think I'd be cuttin' or drillin' anything until I actually had the horns in hand if I were you, tho....]
PM me your list with vendors, specs, and part numbers, so we can put together a preliminary parts list to post here, please. Are you using air-core inductors? Are they custom? N/A from Parts Express, for example.
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