Help with 2404 diaphragm

[Sootshe]

Greetings all,

Been doing some experimenting with the 2404 & have acquired 2 pairs of 2404H's with unknown history.

On careful listening both pairs have a distinctly different sound, so out with the tool kit to check out the diaphragms. 1 pair has the diaphragm as per attached pic, whilst the other has an all silver diaphragm.

Have done searches here & elsewhere to try to determine the difference & from what I have come up with, the frams with the gold surrounds is to suit the 2404H which allows the driver to be crossed over at 3.5K & handles more power, whilst the all silver one is for the driver that must be crossed at 6 or 7K & handles less power? I prefer the sound of the all silver diaphragm & would like to source a pair of these. My dilemma is that most of the companies selling the genuine JBL fram seem to have a goldy type coloured surround as per attached pic & not the all silver type.

Do you think the two types of frams I have are genuine?

Is the colour of the inner & outer ring of the available genuine frams irrelevant?

I should describe the differences in sound quality.......the all silver frams are cleaner, clearer, more transparent & on the whole, have more clarity. The gold surround types don't sound bad, it's just that the all silver ones have a beautiful transparency to them.

Thanks for any advice,
John

[1audiohack]

The diaphragm shown in your pic is a D16R2405 and should be crossed at 5kHz or higher. It should I am quite certain be mated with a phase plug that is right about 1.720" at the base. Measure all your phase plugs and show a picture of the other diaphragm.

[Sootshe]

The diaphragm shown in your pic is a D16R2405 and should be crossed at 5kHz or higher. It should I am quite certain be mated with a phase plug that is right about 1.720" at the base. Measure all your phase plugs and show a picture of the other diaphragm.

Thanks for your reply. I'll get the photo of the other diaphragms to you & also the measurements of the phase plugs.
John

[Sootshe]

Here's the pic of both diaphragms. I don't have a mic to measure the phase plugs,but by my reckoning they are not the 1.715 inch diameter but rather they are both 1.6 inch.
Crossong these over at 6K @ 18db.

[Sootshe]

UPDATE:

Decided to pull the other driver apart....the other one with the original diaphragm in it.
When I did this, I found that there was a lot of debris & dirt in there.
When these drivers were shipped to me they were packed in a carton with a lot of that small, lighter than air, white styrofoam & the drivers were not covered in any way. When I received them I pulled a few pieces of styrofoam out from the external of the horn throat, but when I actually opened them up there was more styrofoam inside & on the phase plug & dirt on the diaphragm.

I pulled out all the styrofoam & cleaned the outside of the diaphragm with a very soft artists brush. All good. Reassembled together & now sounds excellent. Very similar to the other pair, but a tad smoother.

Do you think it would be worthwhile to actually take the diaphragm out & clean inside the gap?

Still interested in your thoughts on these 2 different diaphragms & the dimensions of the phase plugs.

Regards,
John

[ratitifb]

Do you think it would be worthwhile to actually take the diaphragm out & clean inside the gap?

if all sound excellent after cleaning i suggest doing nothing with the dia/gap. Don't forget the gap is sealed and protected by the phragm itself against outside penetration like dust ... Possibly play a sweep sinus to doublecheck centering voice coil and any distortion.

By the way i have an original 2404 pair with the same silver dias.

[Sootshe]

By the way i have an original 2404 pair with the same silver dias.

Thats good to know......so the all silver may in fact not be an aftermarket diaphragm after all!