Aftermarket Diaphram Evaluation

[Robh3606]

I have a couple of after market diaphrams that Guido sent over to do an evaluation for Aquaplas. Before I coat them I am going to take a set of measurements compared to a 2416H and 2425H diaphrams in 2426 cores. Heres the diaphragms and the back cap and first impedance measurement of the Titanium one using WW2. I will take some CLIO measurements on 2370 and post them as well to see how they look. We have been talking about the differences enough lately I think it's about time we tried to see what they show us.

Guido if you have any more information on them can you post it?? These are wound with what looks like edgewound copper. Are they copper or copper clad aluminum??



Rob

[moldyoldy]

I'd guess with these 'frams that the most noticeable and possibly only change will be a slightly tilted drop in sensitivity. Maybe a little lower harmonic content with impulse response too. Just an uneducated prediction, I'll be interested in the results no matter what. Good project!

[Robh3606]

Just doing some impedance runs is quite an eye opener. The aftermarket diaphragms from Guido are not in family with the JBL's and they measure quite differently. I have been running measurements on 3 aftermarkets 1 from Guido and 2 more with 2426H cores I just received. From the published curves an older 8 ohm JBL comes in close to expected with the peaks where they belong and at the correct or lower amplitudes. The aftermarket peaks are not in the same place or can have levels much higher, at least the ones I have. The first run is the first aftermarket in the first post put on a 2370 Horn. The second is another aftermarket and the last is a JBL. All three with a 2370 horn.

Rob

[Guido]

Thanks for that info Rob. I once made different measurements but I havent had this nice WT2 back then.
Currently I'm busy with Richs 4345 project and can't assist you here. Later....

[Robh3606]

These are the two After Market diaphrams I received with the 2426 cores. They are very poorly matched right in the 2-4k band where your ear is most sensitive.


Rob

[Robh3606]

Here's are a pair of 2416H-1 drivers with stock diaphrams.

Rob

[Robh3606]

Impedance runs for both drivers. They are very close just watch the phase and Imp scales in each.

Rob

[Robh3606]

I am going to run 2 more pairs of JBL 2425H diaphrams to see how they stack up. Anyone have a pair of the Radians they can measure. The ones I have measured so far are the normal fair off E-Bay. It would be nice to see how the Radians are with their Mylar surrounds.

Rob

[Zilch]

Have Radians; I forget what cores they're mounted on, but I'll dig them out. Also have 2370As to test on.

Edit: In 2425s. Tonight's shot, so maybe tomorrow....

[Robh3606]

Hello Zilch

Good lets see how they look.

Rob

[Zilch]

Radian vs. JBL diaphragms in 242x motors on 2370A, top two, and what Radian claims on PWT, next. JBL 2416H-1 and 2418H-1, bottom, on the same 2370A horn.

Perhaps they'll send a tech to tweak the notch @ 6.5 kHz outta here. It'd be good if someone could independently verify these results.

I'm only marginally competent at installing diaphragms, and certainly don't have the skill to have gotten the two so identically wrong.

First tried them over a year ago on H3100 with much the same result:

http://audioheritage.org/vbulletin/s...820&#post79820

[Robh3606]

Hello Zilch

Thanks for posting these. Can you break out and show just radian pair to see how well matched they are in the same scale I used 5db per?? That way we can compare the two sets of measurements easier. It's hard to see with all 4 together. Wonder what that notch is??? I am surprised you don't see it in the impeadence of phase curves??

Did you do Sine as well?? It looks like the windowing is giving you a hard time below 1K. How do they look raw?? I have been doing both MLS and Sine to help confirm my measurements. I have a small room as well and in some cases the Sine is the better of the two measurement types buy usually the raw MLS and Sine look really close except for the LF noise in the MLS. When you do MLS are your measurements a single snap shot or are you doing multiple averaged measurements???

If you want to see how well you have the diaphrams installed do a Sine in CLIO and take a look at the THD. If they are not right it the THD goes up and you get some really weird looking curves. You will know just by looking somethings up. You have the WT2 ??? I use that as my signal source when I install them. You can do quick snap shot sweeps, changing the number of measuring points, as it will show on the Impeadence curves as well.

Rob

[coherent_guy]

Have Radians; I forget what cores they're mounted on, but I'll dig them out. Also have 2370As to test on.

Edit: In 2425s. Tonight's shot, so maybe tomorrow....

Would the curves be vastly different with the Radian diaphragms in 2420s with 2370As?

[Zilch]

Can you break out and show just radian pair to see how well matched they are in the same scale I used 5db per?? That way we can compare the two sets of measurements easier.

I use five averaged as standard MLS procedure. Radian only, expanded vertical scale, 5 dB/division:

[Zilch]

Would the curves be vastly different with the Radian diaphragms in 2420s with 2370As?

They would be different. "Vastly" is a matter of definition and application.

Where broad regions of bandwidth (certainly, 1 octave or more,) are involved, a difference of only one or two dB will significantly alter the "voice." Ideally, the differences in response between 2420 and 2425 motors would be adjusted with the filter.

Even ignoring the notch, fine tuning for Radian diaphragms would likely be necessary for use in any quality listening application. They're clearly not the same. They'd have to be tested in 2420s versus the original diaphragms to ascertain the differences. I can tell you that even the diamond-surround JBL aluminums are sufficiently different from the original tangentials when analyzed at this level of detail as to warrant considering filter modifications.

That's where I get into trouble - do I "fix" it at the same time? If there's major redesign involved, that effort is better invested in improved drivers to start with, perhaps. Is it the alnico or the aluminum that I like?

I'll clean up some 2420s here and move the Radians over....