L112 Polarity Phase in HT help needed

Anyone willing to help out a n00b?

My Yamaha 9.1 receiver - one with the fancy YPAO self-tuning capability - complains that one or the other of my L112's is out of phase. I really only use it to get a baseline and then tweak a little more using AVIA and an SPL meter. Since I had the LF drivers reconed a while back, and everything out of the cabinets for binding post replacement and a thorough inspection, I double checked all my internal connections and everything is to spec. Everything sounds great, but seems to lack a certain punch when all speakers are working in concert.

After reading back through a year's worth of posts, the polarity discussions piqued my interest.

My first inclination was to reverse the amp > speaker wire polarity, but I saw a post indicating that would drive the signal backwards through the crossovers. The recommendation was to reverse the connections to the drivers individually.

So the question is, does the L112 need the internal phase correction to work with my non-JBL speaker gear?

Second, anyone know what phase polarity the S38-II run? (don't laugh, they're great as front effects, and actually get good reviews for their intended purpose) I've read the polarity threads till my head spun and still don't know. :blink: I found the following reference on the S38II in a thorough review http://www.stereophile.com/budgetcom...365/index.html "The tweeter and woofer are thus both connected with positive acoustic polarity, the midrange unit with negative polarity. This combines with the phase shift due to the crossover filters to give a summed flat response in the crossover regions."

This would indicate to me they're like the rest of the modern speaker world...

BTW, The letter to the reviewer of the S38's from "Don McRitchie, Webmaster, Lansing Heritage, [email protected]." was interesting.


The whole (speaker) arrangement is:
L112 Main Fronts
S38II Front Effects
Def Tech CLR2002 Center
Def Tech BP2X side rears
Def Tech BP2X center rears
SVS 20-39 PC+ sub

While we're at it, are the L56's also polarity reversed?

Thanks tons for any help.

(my favorite score - $40 working L56 pair off CL now in my home office)

Still looking for the $100 L250's...

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Originally Posted by brutal

Anyone willing to help out a n00b?

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You're only new, here - elsewhere you're well known...

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Originally Posted by brutal

My Yamaha 9.1 receiver - one with the fancy YPAO self-tuning capability - complains that one or the other of my L112's is out of phase...

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I apologize, but I have not a clue about this.

So, in admitted complete ignorance, my first inclination would be to swap L for R L112's and see of the "complaint" follows the speaker swap. If not, there is a different error you need to sus out.

If the "complaint" does follow the swap, then I ask (in no particular order):
- are you the original owner of the L112's...?
- if not, maybe you should open them and compare the innards, ensuring no "smart" guy mucked things up.
- are you certain the Yammie is operating to spec?

I would also drop everything out of the signal path, starting at 2.0 and see if the condition persists. Add zone-by-zone, checking for recurrence of the error message. Drop things out until you find the necessary condition for the error. Then, you can get to work.

Again, I have NO clue about anything beyond 2.0, and even that whacks my confidence...

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Originally Posted by brutal

My first inclination was to reverse the amp > speaker wire polarity, but I saw a post indicating that would drive the signal backwards through the crossovers. The recommendation was to reverse the connections to the drivers individually.

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Your first inclination is correct. Vintage JBL polarity is opposite of industry standard. Mix with any others in HT, and they'll be out-of-phase. Yammie knows.

The post you refer to is wrong. Audio is AC. There is no driving backwards.

Reverse the polarity at the input, NOT the individual drivers. No harm would be done if you did reverse at the drivers, but that's going to require more effort than you anticipate, and they'll be wired "wrong" internally, then....

If your Yamaha indicates that both L112s are acting differently, try putting a 1.5 volt battery to the inputs and be sure that both woofers are popping in the same direction. If not, someone has reversed the wiring internally. This does not negate the possibility that the mid or tweeter are out of phase, and the woofer is correct though.

My Yamaha RX-Z9 also indicates that my JBLs are out of phase compared to my CV's (and they are), but I just switch the wires at the speakers.

Are the L112s woofers supposed to pop in or out with positive voltage applied to the input? I don't know off hand (probably inward), but if you need to know, I have an original unmolested pair (except they've been refinished) I can check for you.

http://www.largescaleonline.com/eima...alin/L112s.jpg

I am the original owner and I've verified I didn't hose up the internal wiring. I'll try reversing and see how it responds. Unfortunately, my DLP just conked out again last night, so I have to resolve that first.

Thanks for the replies.

brutal

Welcome to the JBL Lansing Heritage site :)

You'd be better of with a matching array placed across the fronts, most times the bass comes from the centre or panning in the sound mix with Apollo 13 chapter 13 should have the Saturn V centred and then smoothly off to the left then back to the centre channel and then cuts to the interior of the CM where all the bass is hard in the centre channel.

LFE.1 is used at certain intervals.

And phasing the differences with matched loudspeakers at the front can curse some dips in the bass response.

Catwoman, the beginning starts off with the main titles and some very deep strong bass lines that is carried over the LCR matching and the LFE.1 as well.

Some films have very complex sound pans to left and right but some of these sounds are heard in the centre channel as well, and often this will get the fronts muddled up!

So what to do, reverse the mid range on the centre channel!

Films to look out for would be.

The Empire Strikes Back where the Princess, flips a switch to the right hand channel and the Wookie, punches a few buttons on the left, now I’ve had to phase the fronts to get this to sound correct, otherwise the sound of the buttons comes more from the centre channel.

Many thanks for the responses.

After I got my TV dilemma sorted out (bought another one) I set about to swap the wiring at each speaker and re-ran the Yammy auto tuning. It's happy now and everything sounds great. I have a little more tuning to do as one of the LPAD's on one speaker has also been replaced and doesn't seem to match levels the same as the other. The Yammy does a great job of adjusting it's internal parametric equalization, but I'd like to see the L112's match up a little better instead of the pre-amp doing it. I didn't realize that I hadn't re-glued the foilcal from the LPAD work I had done until I pulled the grills off, so now I hope I can find it in the (original) box.