JBL 2445_46 frq.response

[ivica]

I have decided to "fill-in" the large cavity under voice coil path, and the i will make new measurements to see what would happen. I expect that the efficiency would rise, and that the notch would move towards higher frequency, may be 'out of the interest'.

After some problems, I have done, but notch remain, so now may be some experiments with phase-plug.....

[Legis]

Hi, has the back sticker of the 2446J changed at some point? In the attached pictures there are two different 2446J drivers (serial numbers 16992 and 01679). Their back stickers are little different from each other, the color is different and the little text reads "JBL incorporated ..." in the newer and "James B Lansing Sound..." in the older. I found that at least 2445J drivers had the "James B. Lansing..." text, but did also the first 2446Js had it and the sticker was changed at some point? If this is the case, I take there should not be significant (/any) changes in measured performance of different patches?

Regards,

Legis

[Mike F]

Hi, has the back sticker of the 2446J changed at some point? In the attached pictures there are two different 2446J drivers (serial numbers 16992 and 01679). Their back stickers are little different from each other, the color is different and the little text reads "JBL incorporated ..." in the newer and "James B Lansing Sound..." in the older. I found that at least 2445J drivers had the "James B. Lansing..." text, but did also the first 2446Js had it and the sticker was changed at some point? If this is the case, I take there should not be significant (/any) changes in measured performance of different patches?

Regards,

Legis

Have you measured or listened to the drivers?

[4313B]

Hi, has the back sticker of the 2446J changed at some point? In the attached pictures there are two different 2446J drivers (serial numbers 16992 and 01679). Their back stickers are little different from each other, the color is different and the little text reads "JBL incorporated ..." in the newer and "James B Lansing Sound..." in the older. I found that at least 2445J drivers had the "James B. Lansing..." text, but did also the first 2446Js had it and the sticker was changed at some point? If this is the case, I take there should not be significant (/any) changes in measured performance of different patches?

Regards,

Legis

JBL dropped the whole James B. Lansing Sound thing years ago.

I suspect it finally got too costly to print all that out on everything.

[Legis]

Have you measured or listened to the drivers?

No I haven't but I will as soon as I get them.

[Mr. Widget]

I take there should not be significant (/any) changes in measured performance of different patches?

There shouldn't be, but I'd be surprised if these two drivers measure identically. I have measured a number of used JBLs and depending on the life they have led, their performance can be all over the map.


Widget

[ivica]

There shouldn't be, but I'd be surprised if these two drivers measure identically. I have measured a number of used JBLs and depending on the life they have led, their performance can be all over the map.


Widget

I have almost the same experience with the old and 'older' used JBL drivers, that their responses are different, but generally (all measured with 2311 horn and 2308 lens) older diaphragms have some losses ( up to several dB-s) in the region from about 1.5kHz to about 3~4kHz, , and may be expectable over 10kHz. I vane no idea what are the reasons why mentioned losses happened. May some structural characteristics of titanium dome or suspension have changed over time, or over 'heavy" usage.
If it is assumed that the dome radius is near about 3 inch ( some calculation give "me" R=2 27/32"=72mm), that would lead to the maximal line over the dome mid-point of about 110mm what would, may be, correspond to wave length around 3.1kHz, and half wave length around 1.55kHz, but unfortunately, I have not seen any, technically acceptable, explanation of such "phenomena" .
May be some of the forum members have better explanation.

Regards
Ivica

[Legis]

Interesting, I hope the differences are not that great with my pair. I actually planned to use them with original phrams for the first few months in order to get to know the drivers, and then at some point change to beryllium phrams (Truextent), so the bigger factor is the mint looks than the condition of the original dia. My main concern was that the other one is a counterfeit driver, but I quess this is not the case.