JBL 2470 - are they superior to the K 55?

[ZAKO]

DJK.....I do see the simmiler frequency plot pattern in both the radian 1245 & 1282..... But what about the Radian 1292 for the TAD replacement of 4001/4002 ???

[Duke Spinner]

I replaced my K 55 (X) with JBL 2482 .[]

what did you do to your x-overs ...???

your 2482's are ...16 ohm ....??

[oscarsear]

I replaced my K 55 (X) with JBL 2482 .[]

what did you do to your x-overs ...???

your 2482's are ...16 ohm ....??

The K-55 is also a 16 ohm speaker...........

[tigerwoodKhorns]

I have a question about the 2470's sensitivity.

On the US speaker page, they list the 2404 Baby cheek as 105 db at 1w/1m.

I think that the K Horn bass bin is about 99 db at 1w/1m (an I correct?).

I have teh spec sheet on the JBL 2470 that states "sensitivity at 1mW on a [3 foot long 1" diameter tube] shall be at least 117db."

That's a fine benchmark, but my Altec 511b's are not anything like a 3 foot long 1" tube and everything else is measured at 1w at 1 meter. What is the JBL 2470 drivers sensitivty on a horn at 1 watt one meter away?

Chris

[djk]

The 117dB spec is for 0.001W on a terminated tube, not a horn. It will be about 107dB for 2.83V on a 511B horn.

[Deang]

So it's basically the same as a PD5 on a K-400.

[D-MAN]

I think that the K Horn bass bin is about 99 db at 1w/1m (an I correct?).

Chris

Nope, it's 104db 1w @ 1 m.

The 2404H will be a little "hot" if unattenuated, but it's not unlistenable.

I lived with unattenuated 2404H's for quite a while.

DM

[Tom Mobley]

I have a 2404 sitting on top of an LS right now. It's so much

better than the alnico K-77 thats in the box I'm thinking something is

wrong with the K-77. Holy cow.

Also have a ALK horn with K-55 sitting on there.

Something is up with that deal, it's consistently 4/6dB down to the

K-400/K-55 in the other box. I haven't cross-checked, swapped

drivers or anything yet. Al's horns definitely have a different

sound than the K-400, better in every way that I can hear.

[tigerwoodKhorns]

I just received my JBL 2470's (which the Seller was supoosed to send to AL K. - Seller said that he contacted Fed Ex to fix the problem but they are here anyway - sorry Al, I really tried.).

I have a question. Teh Seller was also supposed to send the drivers with teh phenolic diphrams uninstalled. They got here and they are installed. I checked the resistance and they each measure about 11 to 12 ohms (for 16 ohm drivers). Should new diaphrams measure this low?

I wanrt to open them up and check to see that I have new diaphrams. Can I just unscrew the four screws and open them up and put it back together or is there any special settings or shimming that I need to do to put them back together properly?

Your help is appreciated.

Thanks,

Chris

[Deang]

"Can I just unscrew the four screws and open them up and put it back together?"

Yes.

[tigerwoodKhorns]

Shoule the resistance be so low (11 to 12 ohms) for a 16 ohm driver?

Chris

[Deang]

It's O.K., don't worry about it - completely normal. You're measuring voice coil DCR not impedance. Mine measured 9.6 and 10.2. The important thing here is that the good measurements mean the diaphragms are good.

I don't think we are going to get enough energy out of them in the 400Hz area. The more I try to move away from the K-55 the more I fall in love with it. If the 2470's fall short using the Super AA or ALKs I'm going to try them without a low pass section to see if the bass bin can climb up and fill the gap. It will be fun to play with them, but right now I sure don't see them as a suitable replacement for the venerable K-55.

[Duke Spinner]

they commonly measure .. Exactly in that range

[awsjr]

what am I missing ? or not hearing ?.....I replaced the k55m and horn

in my belle with a altec 511b.....I have tried the altec 808a and

902-8t and the JBL 2470....the JBLs are the best

that I have used.....also using alk universal networks with 2404 tweeters.....I haven't tried the k55 with the 511bs -Al

[sfogg]

Chris,

" I checked the resistance and they each measure about 11 to 12 ohms (for 16 ohm drivers). Should new diaphrams measure this low?"

You measured DC resistance, not the same thing as impedance.

"I wanrt to open them up and check to see that I have new diaphrams. "

You can't really tell just by looking at them unless they were obviously damaged. In the Altec 288s I bought the diaphragms in them looked perfect but didn't sound/measure like they were supposed to. New diaphragms fixed that.

Dean,

"The important thing here is that the good measurements mean the diaphragms are good."

It means their is electrical continuity, not much more then that

Shawn

[tigerwoodKhorns]

Dean,

I am going to be using a 400 hz crossover with a 24db/octave slope. This should help. You are going to ESN's right? Al told me that the steep curve (also 24 db/octave) really helps the JBL's.

Chris

[Tom Mobley]

awsjr,

sounds like you've pretty well covered the field there. "how much

better" is the JBL than the K-55 in your opinion? in what ways is

it better? worth the time, effort, trouble and money?

[Deang]

Thanks Shawn.

Chris, when I initially looked at the plot before buying them I didn't look closely enough at the plot. I read the JBL cut sheet, saw the "300Hz for speech" statement, and then looked at the plot. I mistakenly looked at the high point of the 2470's lower end response and assumed it was 400Hz. I get sloppy when I'm tired and this was one of those instances. At any rate, look at the plot again and ask yourself -- where should this driver be crossed over at?

I'm not using or going to ESN's anytime soon. I have to ask though, what the heck good would it do anyways? You need everything this driver has in its lower range to even have a chance at making it work. It may come down to working endlessly with attenuation -- as the pictures show.

I overlaid the Klipschorn's bass bin raw response over the JBL plot. The Klipschorn's response stops at 500Hz. What I'm showing is that you also need everything the Klipschorn bottom half has to offer to get it to meet up with the lower end of the JBL.

[tigerwoodKhorns]

Dean,

I saw those graphs too. Itf appears that teh log paper is missing a line. I was hoping that the horn was a 500 or 600 hz horn and limiting the bottom end. I was hoping that Al could test them with the seller that I dealt with, it appeared that no matter how many times I told him and sent messages, the driver were never goinbg to make it to AL. It's a shame because we all could have benefitted from Al using them for a few months.

I am not ready yet, but a test with pink noise and the Behringer w/mike on a 400 HZ horn should reveal a lot. It is a shame teh K Horn bass bin does not go up a few hundred more HZ. The options for midrange driver would vastly improve.

Chris

[Duke Spinner]

Thanks Shawn.

Chris, when I initially looked at the plot before buying them I didn't look closely enough at the plot. I read the JBL cut sheet, saw the "300Hz for speech" statement, and then looked at the plot. I mistakenly looked at the high point of the 2470's lower end response and assumed it was 400Hz. I get sloppy when I'm tired and this was one of those instances. At any rate, look at the plot again, forget everything you know about your speakers, and ask yourself -- where should this driver be crossed over at?

I'm not using or going to ESN's anytime soon. I have to ask though, what the heck good would it do anyways? You need everything this driver has in its lower range to even have a chance at making it work. It may come down to working endlessly with attenuation -- as the pictures show.

I overlaid the Klipschorn's bass bin raw response over the JBL plot. The Klipschorn's response stops at 500Hz. What I'm showing is that you also need everything the Klipschorn bottom half has to offer to get it to meet up with the lower end of the JBL.

yow .. that looks like theres a hole in the response .....

in the worst place possible .....[]