Author Topic: Wiring Suitcase Speakers  (Read 4951 times)

Offline AFeastOfFriends

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Wiring Suitcase Speakers
« on: December 04, 2011, 03:28:12 PM »
So the pair of Rhodes speakers I bought a bit ago came in yesterday, and I'm looking to install them myself. My amp tech's busy this week, and I'll have to do this when I eventually get a second pair (still looking) anyways.
I've scourged the internet for a couple hours now and have really only been able to find that factory correct is that one pair goes on front-back on the left side, and the second pair goes on the same on the right.

I have the two wires that connect to the two-pin plugs, and know which wire (white) is positive, and know which prongs on the speakers are positive (red dot), but I don't know how to wire them up to be parallel.


So in short, how do I hook up the the second speaker to the first?



Offline AFeastOfFriends

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Re: Wiring Suitcase Speakers
« Reply #1 on: December 04, 2011, 05:13:14 PM »
Actually, I found a website about it. Just wasn't Rhodes specific. Got them wired up, didn't kill anything.

Turns out, there's a hole in the cone of one of them. Nasty gritty flappy distortion for all to hear.

Offline AFeastOfFriends

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Re: Wiring Suitcase Speakers
« Reply #2 on: December 10, 2011, 01:39:49 PM »
I've been talking to my tech, and he says it wouldn't be a hole making all that distortion if I didn't notice one when I put it in.

He doesn't really know what's wrong without being able to hear it in person, but I can't take it over there for a couple weeks, so I'm trying to do some trouble shooting myself.

It sounds just fine, perfectly clean, until the volume on the preamp gets to about 4 and I play chords. Or if I put the treble/bass booster past 12o'clock around 4 on the volume. The distortion is actually very close to a germanium fuzz sound (which elicits suspicion in the power amp) but is simply too flappy sounding, and behaves too oddly for me to think it's just power amp. Another reason why I somewhat doubt the power amp is that the bass distortion is pretty different from the treble. The bass is fat and harmonic, sounds almost like you're overdriving a Twin (or at least how my twin sounded before the reverb driver mod was pulled out), but the treble is sharp, bitter, and shrill. I think I've gotten that tone once with a component stereo that was pushing cheap-ish speakers too hard.
Biggest thing is, the distortion really sounds like it's coming from just one speaker. I guess I could test this by pulling them out of the cab and isolating them on opposite sides of a door or something.
Also, the distortion isn't linear or exponential in proportion to the volume. Once it has enough to fully distort, that's pretty much as loud as it gets. There's little difference between 7 and 10. Although, the boost/cut knobs still have a pretty strong effect on the distortion even at 10.

I don't suspect the preamp because the two preamp-out/poweramp-in ports put out signal fine (I haven't tried an input, unsure of what would and wouldn't be safe) and I doubt the poweramp because the headphones work just fine (although, I don't know if the power amps do that or if it just comes off the pre)


Really, anything helps. Sorry that it's a big wall of text, but I tried to get every detail in there.
Something I'm looking for is what volumes other Petersons distort, or at least lose cleanliness, at.

Offline bumpyrhode

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Re: Wiring Suitcase Speakers
« Reply #3 on: December 10, 2011, 04:22:27 PM »
Feast,

The symptoms you describe might be caused by an impedance mismatch.

I would go back to the beginning.

What impedance are the speakers you put in?

Make sure each pair is impedance matched.

If I recall correctly the amps look for 16 ohm loads. This means
you need 32 ohm or 8 ohm speakers.

If 32 ohm speakers then make sure the pairs are wired parallel.
If 8 ohm speaker then wire in series.

16 ohm speakers won't work correctly in pairs because they will
end up as a 32 ohm or 8 ohm load. A 32 ohm load would be ok but
an 8 ohm load will make the amps work too hard. If you have 8 ohm
speakers wired in parallel then your final load is 4 ohms and the amps
will really have to work.

Recheck your speaker specs and wiring before anything else.

As you suspected the headphones don't run off the power amps.
The headphone jack is wired in before the amps.

Hope this helps.

Offline AFeastOfFriends

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Re: Wiring Suitcase Speakers
« Reply #4 on: December 11, 2011, 08:57:18 AM »
Is it possible they could have changed the impedance of the amp?

I have a pair of the 32ohm Rhodes speakers wired in parallel, so I'm not sure what could cause the impedance mismatch. I either wired it wrong, there's a short in the wires, or maybe the amps were modified. I didn't look too hard at them, but they look pretty original.

Nevertheless, there were 2 Altec 8ohm speakers, one hooked up to each channel, and there had been for a long time. Maybe the music store they bought the piano from modded the amps?
Or maybe that damaged something in the amps. When I took it to my tech, he didn't really bother with them much since there weren't proper speakers for them.

Offline bumpyrhode

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Re: Wiring Suitcase Speakers
« Reply #5 on: December 12, 2011, 10:03:02 AM »
Quote
Is it possible they could have changed the impedance of the amp?

Possible but I doubt anyone would go through the trouble.

Quote
I have a pair of the 32ohm Rhodes speakers wired in parallel, so I'm not sure what could cause the impedance mismatch. I either wired it wrong, there's a short in the wires, or maybe the amps were modified. I didn't look too hard at them, but they look pretty original.

These are both connected to the same channel right? Have you tried the wiggle test
on any of the wires? You just have one pair in not two pair?

Quote
Nevertheless, there were 2 Altec 8ohm speakers, one hooked up to each channel, and there had been for a long time. Maybe the music store they bought the piano from modded the amps?
Or maybe that damaged something in the amps. When I took it to my tech, he didn't really bother with them much since there weren't proper speakers for them.

I doubt they modded the amps. It would have been easier just to get the
correct speakers. If the Altecs were used for a long time and at high volumes
it's possible the amps were over worked but I would still look to the speakers
and wiring. Still you have to keep in mind you're working with aged components
here. The flabbiness your hearing could also be caused by the power supply
not providing the proper and consistant voltage to the amps. It could be the
power capacitors are failing and can't keep up with the demand as you turn
the volume up. However, I can't guide you through that. It could also be all
your connections just need cleaning. Just trying to guide you through the
process of elimination. 

Here's a pic from Oaktreevintage.com that shows an open cabinet. You can tell
it has 32 ohm speakers wired in parallel from each channel. The front and rear
baffles each have a left and right channel speaker on them. Also, each channel
speaker is mounted across from its' mirror. So left/right on the front changes
to right/left on the back. This is by front/back position not wiring.