MC250 speaker connections and polarity...

MC250 speaker connections and polarity...

Postby jeager » Wed Mar 09, 2011 2:55 pm

So I took the plunge and picked up an MC 250 on ebay. I figured there must be something to it if people are willing to lug this unwieldy thing around when they could have a neat little rack mounted unit in its place...

I followed the directions and hooked up one side of the thing to the speaker in my combo amp just for a test run (I am still waiting on a separate cab). It sounds great, and though i have barely messed with it (about 15 min) I can see that there is some magic in there...

My question is, what about polarity? It seems the manual directions don't mention which speaker lead goes to COM and which to the 8 ohm terminal etc... (ie. black to COM, red to 8 ohm)

or did I miss that info in my rapid skimming of the text?

When i get my CAb I will trying out an E120 which the internet tells me is reverse polarity...then what do I do?
Last edited by jeager on Wed Mar 09, 2011 2:58 pm, edited 1 time in total.
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Re: MC250 speaker connections and polarity...

Postby Pete B. » Wed Mar 09, 2011 2:58 pm

If you are only using only one speaker it doen't matter, although I personally like it better to have the speaker moving outward (like when you hit a low bass note and you can see or feel the speaker move).
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Re: MC250 speaker connections and polarity...

Postby jeager » Wed Mar 09, 2011 3:01 pm

Yea so if I want the speaker to move out in positive direction when I do my very un-jerry like bass note slapping thing... blck/negative to com or red to com...

Hey thanks for quick reply BTW, I am so fired up to mess with this thing.
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Re: MC250 other speaker question...

Postby jeager » Wed Mar 09, 2011 3:05 pm

Its ok for me to just run one side of the amp if I am just using one speaker and don't want the full 100 watts bridged?

I am going into the right side and out of the right side and have the switch on stereo?
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Re: MC250 speaker connections and polarity...

Postby strumminsix » Wed Mar 09, 2011 3:06 pm

JBL, as told to me, marks their jacks backwards.

You can always get a multi-ohm-meter and verify.
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Re: MC250 other speaker question...

Postby Pete B. » Wed Mar 09, 2011 3:24 pm

jeager wrote:Its ok for me to just run one side of the amp if I am just using one speaker and don't want the full 100 watts bridged?

I am going into the right side and out of the right side and have the switch on stereo?


Yes, this is correct.
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Re: MC250 speaker connections and polarity...

Postby jdsmodulus » Wed Mar 09, 2011 3:40 pm

strumminsix wrote:JBL, as told to me, marks their jacks backwards.

You can always get a multi-ohm-meter and verify.

This is true! JBL were building speakers before the UL Listed trademark of Red and Black.
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Re: MC250 speaker connections and polarity...

Postby Stone » Wed Mar 09, 2011 8:13 pm

Pete B. wrote:If you are only using only one speaker it doen't matter, although I personally like it better to have the speaker moving outward (like when you hit a low bass note and you can see or feel the speaker move).



If you mic'd the speaker it would matter. Quick way to check your phase is with a 9v battery to your speaker leads. Connecting the Positive should make the speaker move outward.
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Re: MC250 speaker connections and polarity...

Postby JonnyBoy » Wed Mar 09, 2011 10:22 pm

yo can use any battery, my cell phone worked one time. attach one to the pos and one to the neg. if the speaker pops out, you have the polarity correct on the battery (+/-). if it goes in, its reversed. I connect the positive to the ohm marker and the negative to the COM. I think that's to specification. Strum is right JBL is backwards in terms of accepted color recognition, and so are the Eminence Commonwealths, damn wannabe JBLS.

EDIT:: Sorry stone didn't see you mentioned that. I think it matters too, not that I have noticed any difference, I just like things to be right when it comes to electricity, a little OCD maybe?
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Re: MC250 speaker connections and polarity...

Postby Stone » Thu Mar 10, 2011 5:13 am

OCD ? I think more then a few of us here fit that bill. Steve Kimock and I had a great conversation about using phase to knock back the on stage volume of a multiple speaker (cabinet) rig. I believe he covered it somewhere on his msg board at some point also So i suppose there is no right and wrong, but the sound guy in me requires my stuff to be phase correct. I recently checked a 2x12 Bogner cab and found the two were wired opposite of each other. So it pays to check factory gear as well. .....now im OCD?
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Re: MC250 speaker connections and polarity...

Postby JonnyBoy » Thu Mar 10, 2011 12:43 pm

Stone wrote:OCD ? I think more then a few of us here fit that bill. Steve Kimock and I had a great conversation about using phase to knock back the on stage volume of a multiple speaker (cabinet) rig. I believe he covered it somewhere on his msg board at some point also So i suppose there is no right and wrong, but the sound guy in me requires my stuff to be phase correct. I recently checked a 2x12 Bogner cab and found the two were wired opposite of each other. So it pays to check factory gear as well. .....now im OCD?



:lol:

I think I should note it is not good to have one going one way and the other going the other when I mentioned it doesn't matter, I was speaking of a 1x12. I would think there would be a slight timing issue between the speakers with a 2x12 wired 1 right and 1 wrong? Maybe super subtle, but that would drive me crazy if I found that either way, almost like stepping on the cracks in the sidewalk or touching a dirty doorknob. :smile:
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Re: MC250 speaker connections and polarity...

Postby Stone » Thu Mar 10, 2011 4:12 pm

I dont believe what you would be hearing would be a delay as much as comb filtering. Either way not ideal. Cracks in sidewalks....Thats kinda like how I never understood how Bobby stands on the seems of the two rugs on stage....Just plan crazy :lol:
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Re: MC250 speaker connections and polarity...

Postby mijknahs » Thu Mar 10, 2011 4:53 pm

I once had my 2x12" cabinet wired out of phase and it sounded horrible. Nasally and weak. Kinda like a humbucker wired out of phase with itself. For a while I thought the cabinet just sounded bad. When I finally got it wired correctly (black to black, red to red), it sounded awesome! Now I can't live without it.

I don't think it matters if the overall polarity is reversed. The speakers still move in and out and sound comes out of both sides (front and back). It sounds the same at least to me.
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Re: MC250 speaker connections and polarity...

Postby Pete B. » Thu Mar 10, 2011 6:55 pm

I asked a local soundman friend for input, and here is his response (when he mentions the 10th string, he is talking about Pedal Steel... we both play Steel).
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Hi Dave,
'Question for ya...
If I am running a 1x12 cab with a JBL, I don't think polarity matters when hooking up the JBL, although I prefer the speaker to move outward when I play, so I hook up the pos/neg leads that way.

Here's the question...
If I am mic'ing the 1x12 cab, does polarity matter for any reason?
Does it matter if my speaker moves forward, and maybe other speakers on stage move backward and/or forward (rhythm, lead, bass, keys, steel)???
thx,
Pete B.
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That’s a muddy can of worms, Pete, but I will endeavor to bring some clarity to the waters…

Interestingly enough, JBL’s polarity is opposite that of most other manufacturers, also different amps present different output polarity relative to the input, so simply hooking positive to red does not always guarantee phase coherency.

In regards to your first comment, hook up the speaker and set it where you can see the cone clearly. Damp the strings with your left hand and with your right thumb strike the 10th string hard in the normal fashion, i.e. pushing the string away from you, watching the speaker cone to see which way it travels when you do so. Try this several times to be certain that what you are seeing is consistent. If the cone moves forward (outward) you are in phase, if it retracts when you hit the string switch the wires and try it again. Being as anal as I generally am I personally might make a note about the final hookup on a piece of tape and stick it inside the amp for future reference, remembering that if you change speakers you will have to re-check the phase response.

Now for your real question(s):
Due to the time delay inherent in the amp and PA speakers not being physically aligned in relation to the listeners, combined with the fact that not all microphones, mixers, processors, amps or PA speakers maintain phase correctly, when mic’ing the amp it is a crapshoot. If the console has a phase switch or you have a phase-reversing XLR adapter you can try both ways to see which presents better low frequency reproduction, but remember that this perceived frequency response is also a function of where you are listening from, sound traveling through space in time and all. For this reason many – but not all – pro stage monitor systems are operated at reverse phase relative to the main speaker system. Certainly changing the phase of a mic relative to the speakers it is reproduced in will affect frequency response to a noticeable degree. Neither is scientifically “correct” so one can only pick one and stick with it.

As far as your amp speaker’s polarity relative to the speakers of other players it means nothing at all, as unless identical waveforms are being reproduced it’s all just sound in space; a reverse phase condition between two dissimilar waveforms is pretty much the same as if they were both IN phase and one was simply delayed a few milliseconds, which with different players onstage is going to randomly happen all night anyway.

However, if you were using two amps yourself it would matter a great deal as reverse phase speakers will generate comb filters from hell and that’s what it will feel like until you sort it out.

Keep me posted on your further adventures.
Dave
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I think this is pretty much in line with what everyone is saying here.... right down to the OCD!
The nice thing about the MC250 (and the like), is that it is really easy to swap leads at the amp itself.
btw... Congrats on the MC250!
Here is a link to the Manual:
http://www.berners.ch/McIntosh/Downloads/MC250_own.pdf
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Re: MC250 speaker connections and polarity...

Postby Stone » Fri Mar 11, 2011 9:57 am

Theres some great youtube videos that Dave Rat discusses various phase issues from a pro audio stand point. Very interesting stuff (from a sound nerds perspective...lol) I remember a show I was working and the bass player had a very percussive slap style and I wasnt happy with the sound i was getting (mic'd Ampeg 8x10). I pushed the phase reverse button for giggles and it almost knocked me on my ass. Look out! haha.


Sighh....now im looking at Mac amps online..thanks!
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