Why do 16ohm-drivers measure 7ohms!????

[ivica]

Thanks a lot for all your replies!!
You guys brought some light in my confusion....

The intention of my question was the following;
I got a pair 2405 ( labeled 16ohm , Alnico ) and a pair 2440 ( labeled 16ohm ) mounted to a 2390 horn/lense....
JBL claims the 2405 to be 105db/1w and the 2440 mounted to the 2390 to be 107db/1w. Due to the fact that I personally hate the sound of resistors in a passive crossover, I was wondering if these two drivers would match in terms of loudness when connected to the same amp-channel....
I apprehend the midrange will be a little too loud....
So my idea was to swap the 16ohm Alnico-2405 against an 8ohm Ferrit-2405.... Due to the lower impedance the 2405-8ohm should receive more power from the amp than the 2440-16ohm and compensate the lower efficiency....

But I am on the wrong track, ain`t I ?

Hi Dr.db,

I will NOT suggest You to do any change 2405A vs 2405H. Their efficiency has to be the same (neglecting may be demagnetized Alnico).
So the best would be to do some measurements 2440J with the horn at the distance 1 to 2m from the horn mouth, and 2405 under IDENTICAL conditions, and then to see what would be the difference in the sound levels, and then to decide how to adjust their levels.
Driver efficiency can vary (from the JBL technical spec) even from piece to piece.

Regards
Ivica

[Dr.db]

I agree, a real-life test is always the best way to determine the facts. Especially with these old drivers....

I was at my parents place last weekend and pulled them out for a test.
I did put both drivers on the same amp-channel and I couldn`t notice the 2440 to be much louder. This was a very subjective test, no objective test-equipment was used.
But I didn`t miss highs and the level of the uhf seemed to be right.

[audiomagnate]

...Due to the fact that I personally hate the sound of resistors in a passive crossover...

What do they sound like? The resistors I mean.

[Dr.db]

What do they sound like? The resistors I mean.

In my opinion they lessen the dynamics a little....

[4343]

In my opinion they lessen the dynamics a little....

Is that with non-inductive resistors?

BTW F is used to denote 2 ohm drivers as well as the G, H, & J designators.

[Dr.db]

To be honest, I can`t tell anymore.... The last time we used resistors is quit a while ago. But in that time we`ve tried several types/brands, I remember that.
But ever since I tried to avoid them when possible.

[shoshaw]

Thanks a lot for all your replies!!
You guys brought some light in my confusion....

The intention of my question was the following;
I got a pair 2405 ( labeled 16ohm , Alnico ) and a pair 2440 ( labeled 16ohm ) mounted to a 2390 horn/lense....
JBL claims the 2405 to be 105db/1w and the 2440 mounted to the 2390 to be 107db/1w. Due to the fact that I personally hate the sound of resistors in a passive crossover, I was wondering if these two drivers would match in terms of loudness when connected to the same amp-channel....
I apprehend the midrange will be a little too loud....
So my idea was to swap the 16ohm Alnico-2405 against an 8ohm Ferrit-2405.... Due to the lower impedance the 2405-8ohm should receive more power from the amp than the 2440-16ohm and compensate the lower efficiency....

But I am on the wrong track, ain`t I ?

Are you using an active crossover? If you change from a "16 ohm" to an "8 ohm" driver, the crossover frequency of a passive crossover will change.

[Dr.db]

Hi,


I´m using passive crossovers...

Thanks for the hint!