Phantom Image

[B77perez]

Hello I wanted to ask if anyone here has had a similar experience. I have been into car audio for about 6 to 7 years. I have DSP inside my truck, which it helps create a center image. Now in my home stereo, I do not have a DSP. My receiver is a Nad. M10 V-2. The Nad reciever has dirac live but I have not got it working correctly. YET. I have a pair of Martin Logan Motion 4i bookshelf speakers the M.L.'s create a phantom image where the sound appears to come from the TV's center. I know the M.L.'s speakers have been measured here but don't seem to be very good when looked at through those measurements. It is when the M.L.'s are playing music or watching TV that I hear or see a phantom image of what's playing, band members in their places and actors in theirs.

I recently purchased a pair of Wharfdale 220's which have a good review here, where they measures quite well for thier class. I use them for my speakers for my TV and music. The image they produce is spaced out noticeable left and right. Everything is the same as with the M.L.'s. I ask myself why?

I am probably rambling but this is something I noticed.

 

[staticV3]

The most common factors that affect perceived soundstage are frequency response and directivity.

Right below that I'd place phase- and frequency response consistency between the two speakers.

 

[Dimitri]

The image they produce is spaced out noticeable left and right

This sounds (pardon the pun ) like one of them is connected with reversed polarity ....

 

[B77perez]

This sounds (pardon the pun ) like one of them is connected with reversed polarity ....

I wouldn't put it pass my self will check when I get home.

 

[B77perez]

I checked the wires on the speakers and they are correct.

 

[staticV3]

I checked the wires on the speakers and they are correct.

Here's a good way to ensure that your speakers are in-phase: https://www.audiocheck.net/audiotests_polaritycheck.php

 

[B77perez]

I just reversed wires on one pair and boom sound in center! My concern now is if the tweeter and the woofers are on the same binding posts connected with a metal plate. Is one tweeter correct polarity and the woofer is reversed or vise versa.

 

[Petrushka]

I’ve been wondering if there is a frequency, above which, phase is unimportant.

I’ve read that some systems deliberately wire tweeters out of phase.

 

[B77perez]

I’ve been wondering if there is a frequency, above which, phase is unimportant.

I’ve read that some systems deliberately wire tweeters out of phase.

I need to check my source next. Hopefully the wires crossed are outside of the speakers.

If the tweeters were out of frequency range I would like to find out.

 

[Dimitri]

I’ve been wondering if there is a frequency, above which, phase is unimportant.

I’ve read that some systems deliberately wire tweeters out of phase.

I'd call it with the polarity reversed . which could be "out of phase with the woofer" but it's used to correct a phase reversal taking place due to the "overcomplicated" ( ie third order with too many parts ) crossover.

 

[DVDdoug]

If the grill comes off you can use a 1.5V battery to check the polarity of the woofer. It should pop-out or pull-in depending on polarity, and both speakers should behave the same. That will tell you they are both the same and if the problem is somewhere else.

If one of the woofers is reversed relative to the other you should also notice a big drop in bass.

My concern now is if the tweeter and the woofers are on the same binding posts connected with a metal plate. Is one tweeter correct polarity and the woofer is reversed or vise versa.

A battery won't work for the tweeter because the crossover blocks DC (DC is zero Hz).

You can try a test tone. The tone should be just above the crossover frequency, as low as you can go with the tweeter. The best way to do that might be to put the speakers close together face-to-face, and try it both ways to see if the soundwaves partially cancel when they are out-of-phase of each other. Don't play constant high-power test tones! Speakers aren't designed for constant full-power, especially the tweeters.

The tweeters aren't as critical because at 1kHz the wavelength is about 1-foot. With a 6-inch difference between left & right (about the difference between your ears) the waves are 180 degrees out-of-phase. ...i.e. At higher frequencies the soundwaves are "randomly" in-and-out of phase anyway, depending on your listening position.

I’ve read that some systems deliberately wire tweeters out of phase.

Of course, left & right should be wired the same... The woofer & tweeter are often wired oppositely but the soundwaves should be in-phase at the crossover frequency. The low-pass filter introduces a phase-lag and the high-pass a phase-lead. If the woofer lags by 90 degrees and the tweeter leads by 90 degrees they are 180 degrees out-of-phase and you get a dip at the crossover frequency. Reversing the tweeter (or woofer) puts them back in-phase (at the crossover frequency where it matters). In a 3-way speaker the midrange would be reversed.

 

[Keith_W]

This sounds (pardon the pun ) like one of them is connected with reversed polarity ....

Very perceptive of you! I re-read the OP's post and I don't think I could have made the same diagnosis from the info he gave. Well done!

 

[B77perez]

I just reversed wires on one pair and boom sound in center! My concern now is if the tweeter and the woofers are on the same binding posts connected with a metal plate. Is one tweeter correct polarity and the woofer is reversed or vise versa.

Here's a good way to ensure that your speakers are in-phase: https://www.audiocheck.net/audiotests_polaritycheck.php

I will try this tomorrow when I get home.