Out of phase
 

Hi Guys,

I have built a pair of loudspeakers using GPA 604H II (Altec replicas) drivers. The crossovers were build by a German guy, Herr Werner Jagusch. They are powered by a Shindo Montille.

What I discovered when I ran a demo CD was that the speakers were out of phase.

I have checked the bass drivers with a 9V battery and they are correctly connected (red is +, the membrane moves forward when I apply 9V between the terminals). For the compression drivers, I can't check (I can't see the membranes).

I have also sent the crossovers back to Werner and he checked them, said they are ok.

I have checked the phasing with 3 amplifiers and on all of them I got "out of phase" (with the speaker's cables correctly connected I got the out-of-phase message perfectly centered in-between the speakers - and vice-versa).

Any idea what is going on?

Now, with the speaker's cables inverted for one speaker (red for -) I got the in phase signal perfectly centered in-between the speakers - but since the bass drivers are correctly labeled, they must be out-of-phase in this situation....or I am completely misunderstanding these things.

Any HELP would be much appreciated!

What CD are you using? Is it possible the test track is wrong?

Depending upon the crossover's order (1st, 2nd, 3rd, etc.) you may need to invert the phase of the compression driver relative to the bass driver. You stated that you can't verify the phase of the compression driver via membrane movement, but is its polarity marked? Check the crossover's specifications to ensure that the two drivers are connected in their recommended polarities which may not match between the two drivers by design.

XLO test and burn-in CD. It's not one track, but few of them, some with music.

Actually, it all started after I installed a new cartridge on my turntable. I got the out-of-phase setup (when checked with the Hi-Fi News test LP), but I thought I might mis-connected the headshell leads. Then I decided to play the CD before reversing the wires on the headshell.
The CD player is an Accu DP77.


After the battery test on the woofers, they seem to be in phase (wired correctly from the factory), so this has me wondering .......

So the CD is eliminated.
You've mentioned speakers, amps and sources so far. How about the preamplifier? Have you eliminated that as a possibility?

yes, the compression drivers are marked. I have tried also to invert the wires for one, then for both the compression drivers, while keeping the bass drivers conected correctly. Still no joy :(

Since the bass drivers seem to be ok, one thing I think of is that the compression drivers (one of them, or both) could be wired wrongly from the factory. That is why I tried what I stated above (to keep the bass drivers wired correctly, and just invert one, then both, the compression drivers) - but no joy.

Then I am wondering, since the bass drivers are ok, shouldn't they cancel (the signal output) when I connect one speaker reversed (red for - )? But the sound is quite good, as opposite with the situation when the speakers are connected in the correct way (but out of phase).

Also, the person who designed and executed the crossovers has worked a lot with Shindo (in Germany) and with Altecs, so I am sure 99.9% he knows his stuff. He suggested the Montille might have an issue (but I have tried two other amplifiers beside the Montille), or the GPA's (the battery test was suggested by himself). Even more, I have shipped back the crossovers to Germany and he double-checked them as he knew my issue.

Yes, I have skipped the preamp. Have plugged the CD player directly into Montille (it has pots for volume). And the other two amplifiers were also skipping the preamp.

not sure I am allowed to insert links here, but the crossovers are like these:

Do you use XLR cables for the accuphase? They have a different polarity from american units. Try that out. With rca connection you will avoid this problem.
Cheers

It's RCA connection I'm using.