Recapped the Imperial 7s tonight

[geaugafletcher]

I finally got around to finishing the recap of my Marantz Imperial 7s with North Creek Zen capacitors. I performed surgery on one side only to compare old and new.

These speakers are not so strong on the high end, so I initially wired in the caps as North Creek specified to enhance high end and soften mid range. The recapped speaker sounded more detailed and 'modern' without that sort of veiled, excessively warm, fuzzy sound that I associate with old speakers. However, it was quieter overall and not as satisfying to listen to - and the midrange was just kinda absent. So tonight, I opened up both cabinets and wired the caps in the other direction. Final result?

Well, they're still a little quieter than before. However, the midrange is mostly back and the highs are not quite so ... bright. I think it's a good balance.

HOWEVER...I tested all the big ol' 5 watt resistors and all the 3 ohms showed around 1 ohm. The 8 ohms and 1 ohms were fine. Could I have damaged the resistors in question with too much heat while soldering? These speakers have toggle switches that let you choose among three levels for the mids and tweeters - this effected by the resistors. Could some other attributes of the crossover be changed when certain resistors are out of spec?

The old capacitors look very much like old-fashioned fly paper canisters with three wires sticking out of them.

I'm grateful for any advice you guys can offer.

[geaugafletcher]

Sorry to do it, but I'm going to bump my own post (the shame!) to clarify my real question...

Even after searching the forums and googling crossovers, I'm not certain about the role of the resistors in this instance.

What I know for sure: there are five resistors per crossover that are used to attenuate mid and high to three different levels.

What I'm not sure of: is it possible that they have any other role in the circuit? Is it likely that my 45 watt Weller iron and noobie technique gave a few of those 5 watt resistors enough heat to put them way out of spec? I can scan and post a copy of the schematic if anybody needs it and is able to help.

[kevinkr]

No, it's not likely that your "noobie" soldering technique did anything to these resistors, it is far more likely the result of age and internal heating due to significant power dissipation. They may have been under rated for the application as well. I would simply replace them.

I have found that the old ceramic wire wounds don't sound too wonderful in the tweeter/mid range cross-overs.. I would take a look at the mills non-inductive wirewounds, and would recommend using ones rated at about 10W - I suspect the originals might have been undersized. (Dale non-inductive wire wounds in the aluminum case as good too imho, as are several of the less expensive generic equivalents.)

Depending on where they are located in the cross-over circuits they might account for some of the other effects you mention.

I would replace all of the resistors in the cross-over with new ones rated at about 2X power dissipation of the originals.