Realistic Mach 2 wiring questions...

[Ricktptman]

I recently acquired (thrift shop, I probably overpaid, but I didn't have to deal with hyperinflated shipping and I was able to restain and restore most of exterior) a set of these speakers and they had some mostly fixable problems. First, whomever owned them previously had installed a set of what a friend of mine likes to call "funky puppy" subwoofers. They were wired out of phase with each other, which was easy enough to correct inasmuch as I presume the black wire was the negative. They all seem phase correct both with each other and with the other pair (Advent Legacies) of speakers in my workshop now. But since whomever worked on them last couldn't keep their game together with the woofers I'm not certain what the correct wire polarity is for the midrange drivers, which I've had to remove to install new surrounds. (They're on a very literal slow boat from China. They'll get here right before Thanksgiving.) The woofers are orange and ugly but they sound pretty good overall, in spite of some age related/manufacturer sloth with regard to the speaker terminal insulator tab disintegrating on contact. The Bass is a little on the loose side, but the free air resonance of the woofers is alleged to be about 27Hz. The tweeters are working fine so I'm not going to touch them.

If someone can verify which wire is the hot wire for the midranges, I'd really appreciate it.

If someone has the Thiele/Small parameters for the original woofers, I might consider replacing these ugly orange woofers (I took the brand name off the dust cap, which made noises like a rattlesnake until I damped the dust caps with some gaffer's tape) with something better, if I know what the original parameters as a point of departure.

TIA, everyone. Helpful advice is appreciated.

 

[Ricktptman]

Thank you, much appreciated!

I can't see them either, but I can see your thumbnail.

I found photographs of the crossover in another thread and it looks like (if I have the right leads) the orange wire is positive and the brown is negative. I see the lamp fuse now, which is something I was curious about. If I push the funky puppys hard (@110watts into that load which is probably around 5 ohms with that woofer), I can hear one or the other of them cut out briefly. When it does it makes the relays in my Denon PMA-860 Integrated begin to cycle. It's a gutsy little integrated for its weight class.

 

[Stuart Pedaso]

View attachment 2689795
That was posted in this thread, which I can not see any of the images, maybe you can.

That schematic, as posted by @HomeBody, was originally drawn and posted by @Ceallach in a different thread (now lost to that thread as well).

This schematic has fatal errors.

The filter for each driver puts a parallel device directly across the amplifier output:



After @Pete B pointed this out, Ceallach posted a corrected schematic. That pic is also now lost but it appears @SHK reposted it a few years later in that same thread:



Unfortunately, the original drawing is still circulating within the forums.

 

[goodolpg]

That schematic, as posted by @HomeBody, was originally drawn and posted by @Ceallach in a different thread (now lost to that thread as well).

This schematic has fatal errors.

The filter for each driver puts a parallel device directly across the amplifier output:

View attachment 2690031

After @Pete B pointed this out, Ceallach posted a corrected schematic. That pic is also now lost but it appears @SHK reposted it a few years later in that same thread:

View attachment 2690023

Unfortunately, the original drawing is still circulating within the forums.

@Stuart Pedaso So the one I posted is wrong? If yes I'll delete it. I try to post accurate information.

 

[Ricktptman]

Thank you, Stuart Pedaso, for posting the correct schematic. This will become useful later, when I get around to recapping the crossover.

I apologize for not getting back out to my workshop sooner and double checking the speakers. The woofers had their speaker wire spade connectors cut off and I incorrectly thought the midrange connectors were cut as well. They're there, so that solves the entire issue about midrange driver polarity.

Next question: Should I bridge that lamp fuse or leave it as is? The driver that's in the enclosure works, but is 4 ohm, not 8 ohm, so that lowers the entire speaker's load to the amplifier and I suspect that affects the fuse lamp's function. TIA...

 

[Stuart Pedaso]

@Stuart Pedaso So the one I posted is wrong?

Yes. That was Ceallach's first effort, with a bit of component placement confusion, before he later posted the corrected schematic.

I remembered that original thread from embarrassment of not catching the problem until Pete brought it to light. With casual viewing, I think that being so nicely drawn diverts attention from the error.

That's my excuse ... and I'm sticking to it!