opinions & help about my JBL 4520

[Lee in Montreal]

The horn path in the 4520 is 8ft, not 12ft as can be read in JBL's literature. The 4530 is 7ft.

8ft is 2.40meter meaning the 4520 will load down to 35Hz (1/4 wave) and will be "generous" at 70Hz (1/2 wave fundamental) with a dip (phase inversion) at 105Hz

If OP had a digital crossover, I would have suggested ditching the 2404 and keeping a simple two-way system with CD compensation on the 2360. But crossing at 300Hz may be enthusiastic. I would stick to 350/400Hz. At the most.

[Kalle]

I wouldn't bother with D16R2441 diaphragms when you have Radian 1245-16's available for 1/3th of the price! I paid around €119 each for my Radians at Thomann.

A couple of days ago someone listed 4 4520's and 4530's for sale in Belgium, if I only had enough room for them!

How do you think it changed the sound from original TI? I have been curios for this a while. Any downsides? Uppsides?

/Karl

[Horn Fanatic]

The horn path in the 4520 is 8ft, not 12ft as can be read in JBL's literature. The 4530 is 7ft.

8ft is 2.40meter meaning the 4520 will load down to 35Hz (1/4 wave) and will be "generous" at 70Hz (1/2 wave fundamental) with a dip (phase inversion) at 105Hz

If OP had a digital crossover, I would have suggested ditching the 2404 and keeping a simple two-way system with CD compensation on the 2360. But crossing at 300Hz may be enthusiastic. I would stick to 350/400Hz. At the most.

Perhaps what JBL meant by the 4520 having a 12 foot horn, is the effective length. Yes, the physical length is approximately 8 feet, but the effective length of a low frequency horn based on it's acoustical parameters and mouth dimensions can extend the length of the horn up to a few feet. The same holds true for the vent in a bass reflex enclosure. The effective length of the vent extends past the physical dimensions on either end, and those dimensions can differ on either end as to how the tube is terminated. Those lengths also dependent on several acoustical and physical parameters. The solid angle in which the horn is deployed is also a factor.

H.F.