JBL 104H-2 & 052Ti

[couguarek]

Hi!

I've got a JBL 104H-2 and JBL 052Ti. I want to build new speakers with 11" bass driver from Acoustic Research AR 3a Improved. I want to modify the crossover frequency in the network from 4412A (http://www.jblproservice.com/pdf/Stu...es/4412ALR.pdf). I want to change crossover frequency from 850hz to 525Hz (the high crossover frequency must be the same 4 KHz).
I have one more question. I need SPL parameter of the 104H-2 and 052Ti. Please tell mi if somebody know something.

Greetings from Poland!

[duaneage]

Bad idea. The resonant frequency of the 104H is around 220 or so. You need to be at least 3x the FS and preferably 4x when you cross it over or the resonance will affect the crossover in a bad way. The 104 is usually crossed over at 800 hz with a 12 or 18 db/oct slope. You would have to go at least 24 db/oct to do 525 and I am not sure it would work without a LCR trap to damp the FS of the mid.

[DavidF]

Hi!

I've got a JBL 104H-2 and JBL 052Ti. I want to build new speakers with 11" bass driver from Acoustic Research AR 3a Improved. I want to modify the crossover frequency in the network from 4412A (http://www.jblproservice.com/pdf/Stu...es/4412ALR.pdf). I want to change crossover frequency from 850hz to 525Hz (the high crossover frequency must be the same 4 KHz).
I have one more question. I need SPL parameter of the 104H-2 and 052Ti. Please tell mi if somebody know something.

Greetings from Poland!

There is an image attached to a thread on this forum somewhere with the frequency response graph for the 104H-2/3. Try the search feature, could well have been posted by Giskard. Same with the 035Ti but posted by Widget. Not a 052, OK, but may give a sample response as being from the same family of tweeter.

Difficult to help with a crossover suggestion unless someone has actual experience with the drivers and design you are aiming for. Suggest you use the mid and high design of any of the L100T- 4412/10 models and rework the woofer leg to suit your AR woofer.

David F

[duaneage]

Final attenuation of the mid and HF will depend on how efficient the AR woofer is. I suggest you use L-Pads so you can adjust the level of the HF and MF to match the AR. That would be easiest way.

[speakerdave]

I think you may find that the AR woofer is very much less efficient than the JBL 104 midrange and the two are not a good match. That woofer and that midrange do not have the same dynamic capabilities; on dynamic peaks the midrange and tweeter will leave the woofer behind and the frequency response will be thrown out of balance. I would suggest you look around for some JBL woofers, and, to very much simplify your speaker building, choose a woofer that JBL has used with that midrange in one of its speakers. Then you will also have a crossover schematic to copy. Some of the Eagle Scouts on the forum will be able to tell which woofers and which speakers.

David

[couguarek]

duaneage => What is the LCR trap and how this work? Can I make this trap using some programs?

[duaneage]

A LCR trap is a resonant circuit designed to operate at the resonant frequency of the driver. The idea is to damp the driver at Fs so that it does not ring in the band you are using it in.


These are really band-aids for a improper use of a driver. IF you insist on using a driver below it's recommended range you are going to require a steep crossover point to prevent the driver from being used too low and damaging it,

Design formulas

Determine the resonant Frequency (FS)

C = .03003/FS
L = .02252/FS2C
B = -3db bandwidth (f1-f2) where f1 and f2 are equal to 1/2 the driver impedance peak
R = 1/6.2832CB

The resistor, capacitor and inductor are in parallel with each other, but in series with the driver. You will know if it works when the driver impedance peak is lowered and the cone does not move much when you approach FS.

Overall I do not recommend this as it will require a great deal of testing to get it right.

[couguarek]

Thank you so much for help!

I've got one more (last ) question about enclosure for 104h-2. How capacity is optimaly for this speaker?