JBL C 51 Apollo

[dadsf250]

Hi. I am new here. Looking for info on my C51 apollo speakers. They have 16 ohm LE 15 and I believe LE 85 horn drivers. They are all original. I am wondering if the crossovers ( LX 5) should be checked out and interested in any suggested mods or improvements. Thanks Dan

[Don C]

If the woofers have the hardened yellow lansaloy surround, they would probably benefit from a refoam job, or recone.



Hi. I am new here. Looking for info on my C51 apollo speakers. They have 16 ohm LE 15 and I believe LE 85 horn drivers. They are all original. I am wondering if the crossovers ( LX 5) should be checked out and interested in any suggested mods or improvements. Thanks Dan

[Mr. Widget]

The LE15A, LE85, and LX5 is called an S7 system... it was my very fist JBL and it is a very nice system. As Don mentioned, the surrounds on the LE15A do get very stiff over the years and often crack when someone pushes them after they have stiffened. Assuming your woofers are still in good shape but with stiff surrounds, having the yellow surround replaced with a new gray foam surround will restore much of the lost deep bass.

In my exploration I discovered that the LX5 crossover was really holding the system back. A proper modern crossover will really open up the sound, but it requires some real engineering and I don't think anyone has posted an appropriate schematic on this forum. In my early days I messed around with several crossover topologies and eventually went active. I also eventually added a tweeter. The 2405 (077) works very well with the LE85.

My S7 came with a potato masher horn and lens. It has a conical dispersion pattern and rolls off the highs too much in my opinion. I replaced it with the 2307/2308 (HL91), the 2312/2308 (HL92) would be an even better choice.

An explanation for newbies:

In the above, the model numbers in the parentheses are the consumer model numbers for identical parts to the pro numbers. Back in the day I used pro parts as they were readily available at a discount and today they are prevalent on the used market and typically less expensive. Other than paint color they are identical.

Another note for newbies... don't concern yourself with the 16 ohm woofer. in the case of the LE15A, LE85, and 077/2405, at different times they have each been labeled 8 ohms or 16 ohms depending on what was popular at the time. all three of these drivers are between 8 and 16 and will work well with solid state or older tube gear. If you really get into it and design a custom passive crossover measure them and determine what the exact impedance is at your desired crossover frequency. If you go active, it really does not matter.


Widget

[Audiobeer]

I also have a couple of pairs that I am just finishing. Had my woofers refoamed and when I get them together I know whether the crossovers on mine need work. I asked the same question here and that's pretty much the responses I recieved. :)