JBL HDI-3600 Crossover Upgrade: Mundorf

Original crossovers:

https://ibb.co/W5YQQH5
https://ibb.co/LR0wy6N

Be careful replacing electrolytics. They tend to be in the bass section and changes in the ESR can unduly affect the entire impedance curve negatively. If you replace a high ESR cap with low, you must compensate with added R in series. Even small changes, on the order of 0.5 Ohms or less, can have big impacts in the overall impedance, especially caps that go to ground either in the odd numbered poles or as part of a Zobel.

High end Mundorf caps have a sound signature. You should experiment to see if it’s the way you want to go. I find them splashy and overly zingy. Excess air and color.

Listen to Magico and B&W’s top end stuff for an idea.

changes in the ESR can unduly affect the entire impedance curve negatively.

Thanks Erik, that’s the first I’ve ever heard of that. My thoughts were Elecs are mostly used in LF since SQ impact is lower using cheap in LF.

I’ve had some pretty good experiences with Mundorf on the ’zing’. I listen to a lot of jazz and enjoy the clarity on the percussion.

Any recommendations you might have and any thoughts on the variances in values?

I think for the most part you should be OK.

The pictures you showed me had 2 electrolytics.

Yeah, the impedance issue can bite you and the only way to show it to people is to walk through a simulation using XSim crossover simulator or the like. The issue is that in the bass, a cap going to ground has a certain ESR, often with an additional small value R in series. Changing that small ESR value can tank the impedance in the REST of the circuit. 😁 Not to mention, caps used for baffle step may use the ESR as part of the baffle step compensation, so alterations to the ESR here, again, can have unexpected consequences.

Caps in series with the driver are a lot safer to change, with the worst that can happen is a modest change in output level, but this can fool you into thinking your new caps are better when they are just louder.

Changing film caps is also a lot safer because they generally have negligible ESR to begin with, and modern electrolytics also have lower ESR than their 1980’s counterparts, so the amount of risk you incur without direct measurement is a lot smaller now than it used to be.

If you are going to invest this much money in your crossover you may also want to get a Dayton DATS to measure the impedance curves of the speakers before you change anything, and the ESR of any caps before replacement.

If you break anything this will be a huge help in troubleshooting.

This video should inspire you in your search for a better crossover:

All the best,
Nonoise

All great points Erik. One thing to consider, I've had some decent results from the Mundorf Plain elecs, in fact I'd fairly highly recommend them for electrolytic applications. Maybe I will consider a change to the overall bill of materials.

You're right, it is a lot of coin, although I know I'd be jumping from a $4-5k speaker sound to maybe closer to a $10k one.

Separately, Mundorf, I love the brand. I just built XLR interconnects this afternoon with their 18awg SilverGold wire - it's the best cable I've ever heard - in my system or elsewhere. You pay, but disappointments are rare with Mun I've found.

Can we have an update on this project?

You would be changing the values of too many components that you risking having peaks and dips in the response. Room correction might compensate for faults, but I'd stick to the original values and add Duelund / VCap CuTF decoupling caps at .01uf or .1uf to the stock caps you couldn't replace.