Strange Problem with Monolith IIIPs

[minorl]

Hello everyone. It has been quite some time since I last posted. Divorce will do that to you. My Monolith IIIPs have been stored, along with my other audio equipment for over four years without use. When I powered them up recently, the speakers exhibited a strained sound in the upper panels. The sound became noisy and began to die. I had my Audio Research SP11 pre-amp and VTM 120 amps serviced and repaired last week. When I re-powered everything. The same problem occured. (The amps had blown fuses and resistors, and some tubes were bad, so they needed repair). When I play at very low levels I can hardly notice bad sound. But, when the music rocks at higher (not too loud) levels, the sound strains and actually goes away. I replaced the amps and pre-amp with different units and the speakers still sound strained at certain parts of the music. Can this be the panels going bad or the crossover/power supplies?

thanks,

minorl

 

[ovature]

Hello everyone. It has been quite some time since I last posted. Divorce will do that to you. My Monolith IIIPs have been stored, along with my other audio equipment for over four years without use. When I powered them up recently, the speakers exhibited a strained sound in the upper panels. The sound became noisy and began to die. I had my Audio Research SP11 pre-amp and VTM 120 amps serviced and repaired last week. When I re-powered everything. The same problem occured. (The amps had blown fuses and resistors, and some tubes were bad, so they needed repair). When I play at very low levels I can hardly notice bad sound. But, when the music rocks at higher (not too loud) levels, the sound strains and actually goes away. I replaced the amps and pre-amp with different units and the speakers still sound strained at certain parts of the music. Can this be the panels going bad or the crossover/power supplies?

thanks,

minorl

Sounds like you need new panels or you have a short/bad solder connection someplace.

 

[JonFo]

First, double check your wiring, as the IIIp external crossover is easy to mis-wire.

Second, leave the speakers plugged in for a while before playing, then play music at low levels. Then crank it up. if you still experience issues, then it might be the ESL step-up board that has an issue.

Regardless, I'd contact Jim Powers at the factory for further advice.

In any case, I'd recommend an update to the panels, a bargain at $890.

let us know how it goes.

Cheers,

 

[minorl]

Thanks everyone. I contacted Jim at ML and discussed some options. My speakers were built in 1990, but the panels appear to be fine. However, I'm ordering new panels anyway, before they stop making them for this speaker. My line fuses for both speakers were blown. Imagine that. Also, my line fuse for my Ultra modified Bedini 250/250 amp (powers the woofers) also blew. No damage to the amp, but I noticed several other things. When I measured the impedance to the crossover, I found the following. For my left speaker, the low input showed an open circuit, the high input was 2 megaohms and the high output was 5.4 ohms and the low output was 3.6 ohms. I opened the crossover and found the high output connection to the circuit board with a cold solder joint. I resoldered the connections and the impedance then measured 5.2 ohms. I measured the same impedances for the right speaker with no open circuit. I am concerned that the high input measures 2 megaohms. I will speak with Jim again to get his thoughts.

Any ideas?

Thanks,

Lawren

 

[JonFo]

Thanks everyone. ... I'm ordering new panels anyway, before they stop making them for this speaker. My line fuses for both speakers were blown. [Issues with passive x-over]....

Any ideas?

Thanks,

Lawren

Lawren,

First, I’m glad Jim helped you find the root cause. As suspected, something in the step to the panels is generally involved with a silent or quiet panel. Blown fuses are rare, but do happen. The little red light on the back shelf must have been off as well, that the first tell-tale to look for in the future.

Now, for your passive xover issues, my recurring recommendation is to just junk it.
You clearly have the extra amplification to support an active setup, so I highly recommend you get some form of active crossover and enter a whole new dimension of pleasure with your Monoliths.

Ok, so if that’s not enough hyperbole to get you moving, several of us on the board have been truly blown away by the use of the DriveRack 260 to perform the crossover duties on our Monoliths. Please see prior posts of mine for more hammering on why.

I truly can’t recommend some form of active x-over enough, however, if you really want, I have a nice pair of low-hours Monolith IIIp passive crossovers I’d be willing to part with for a reasonable price

Again, good news that your back up and running and new panels will be a revelation as well. See my post on how to upgrade them here.

 

[minorl]

I'll look into the Driverack 260 system. I was and am still trying to locate a Bryston 10B crossover. Everything I've heard about it says its the best for the money. Once Jim test the crossovers and "L-Brackets" for the Monolith IIIP, I'll let you know what he finds.

Enjoy

 

[JonFo]

I'll look into the Driverack 260 system. I was and am still trying to locate a Bryston 10B crossover. Everything I've heard about it says its the best for the money. Once Jim test the crossovers and "L-Brackets" for the Monolith IIIP, I'll let you know what he finds.

Enjoy

minorl, while the 10B was a nice product in it's time, and for what it does do, it does it well, it is missing critical functions a DriveRack gives you (and that you need for max performance from the Monolith):

1- The ability to adjust delays between panel and woofer. The panel requires 1.54ms of delay relative to the woofer to have impulse measurements align. Getting this right smoothes out the frequency response as well as increase the ‘cohesiveness’ between panel and woofer.

2- EQ tweaks. I know, this is heresy to many people, but if used judiciously, it helps more than hinders the quality of the resulting sound. You’d be surprised at how many points of EQ you wind up using to fix room effects (more than speaker issues). There are EQ’s for each output (panel, Woofer) and global.

3- Crossover flexibility. Not only pick your crossover point, but also your slopes and type (Butterworth, Linkwitz-Riley, etc.). Personally, I find an L-R 24db octave works best on my Monoliths.

No analog crossover will ever give you the above. And the transparency of the DBX unit is excellent. Overall, the benefits far outweigh any potential negatives (not that I’ve found any of those yet).
The biggest challenge is dealing with line to balanced input matches, but a Jensen transformer will fix that.

But no question a 10B will sound better than the passives. But a DriveRack will be significantly better than the 10B. Believe me, I’ve been down that exact route: passives, to active analog and finally to active speaker processor. No going back for me. Heck, I got another DriveRack for my Center…