detecting if speakers are out of phase

altoidboy · Post by **altoidboy** » Wed Jun 07, 2006 11:20 pm

i've got a new set of speakers (Event SP8's), running through a Mackie Big Knob, being fed from my computer's DAW + audio interface.

as I'm getting used to these new speakers and listening to some cd's through them, some things just sound really weird. mixes i knew by heart sound SO different and a little weird. to the point where i think "they can't possibly have mastered it like that". sometimes the stereo field is weird.

i know all this sounds like a phase problem. how can i test this definitively?

i tried pulling a sine wave into my daw, feeding it to both speakers, and flipping phase on one of them. when i did this, i got a definitive out-of-phase sound. it was really weird -- everywhere i moved my head, it would change, and it was less full. when i played it back straight, it sounded much better.

so i thought that test showed me they ARE in the correct phase relationship. but mixes in itunes still sound really weird.

how can i easily and definitively test for my speakers being out of phase?

RodC · Post by **RodC** » Thu Jun 08, 2006 6:58 am

Record both of them into your daw.

Set up a sine wave or any single sound, snare, tom hit etc...

Close mic both speakers at the same time (Seperate mics, Seperate channels). Zoom way in, just like you do when yo alighn guitar tracks or drum tracks. You should see both signals cross 0 going the same direction.

LewKellogg · Post by **LewKellogg** » Thu Jun 08, 2006 7:07 am

If you feed the same sine wave to both speakers and flip the phase you should get no sound unless something in the chain is different or colors the tone. The good news is that you're not hearing things... _ Something actually appears to be wrong.

Look for differences between the two signal paths.

RodC · Post by **RodC** » Thu Jun 08, 2006 7:20 am

LewKellogg wrote:If you feed the same sine wave to both speakers and flip the phase you should get no sound unless something in the chain is different or colors the tone. The good news is that you're not hearing things... _ Something actually appears to be wrong.

Look for differences between the two signal paths.

True, if you look at the waveforms you may be able to see some differences. If it dont completly cut out they may not be 100% out of phase.

LewKellogg · Post by **LewKellogg** » Thu Jun 08, 2006 8:26 am

I was a bit sloppy in using the term Phase. I should have said polarity - I'm assuming that we're speaking casually and although Phase is the word typically used, with speakers there is really only the potential for polarity (+ or -) differences. At least I can't image a situation where speakers could be out of phase any way other than 180... Is there one?

Russian Recording · Post by **Russian Recording** » Thu Jun 08, 2006 8:52 am

if your speakers are out of polarity, send a mono signal (like a tone) equally to both speakers. Face the speakers directly at eachother and move them towards eachother. If they are indeed out ofphase, they will completely cancel eachother out as they get closer.

in reality, you should hear if your speakers are out of polarity without this test. it's pretty obvious.

mike

amishsixstringer · Post by **amishsixstringer** » Thu Jun 08, 2006 12:57 pm

I had a sloppy setup once when i used two different length cables. At that point one side is delayed a bit and you get an actual phase difference that comb filters some stuff. It wasn't just a little different cable length...like 20 and 6 feet or something. If your speakers are 180 degrees out of push/pull it would make you want to spin your head around in circles trying to locate the sound. My guess is that you're just now hearing the music as it is supposed to sound or that you may have your listening position in a weird corner or in a room with no treatment done to it? Good luck

Neil

TapeOpAndy · Post by **TapeOpAndy** » Thu Jun 08, 2006 10:41 pm

amishsixstringer wrote:I had a sloppy setup once when i used two different length cables. At that point one side is delayed a bit and you get an actual phase difference that comb filters some stuff.

Neil

Speed of sound in air = approx 345 m/s. Transmission speed of an electrial signal thru cable = approx 300 MILLION m/s.

Which means moving your speaker a millimeter back will have about as much effect on timing as increasing your cable length by a kilometer (speaking in orders of magnitude).

Dang, you must've been using some pretty long cables to hear comb filtering due to cable-induced delay. Either that, or your ears can hear comb filtering of frequencies in the MHz.

TapeOpAndy · Post by **TapeOpAndy** » Thu Jun 08, 2006 10:51 pm

altoidboy wrote: i tried pulling a sine wave into my daw, feeding it to both speakers, and flipping phase on one of them. when i did this, i got a definitive out-of-phase sound. it was really weird -- everywhere i moved my head, it would change, and it was less full. when i played it back straight, it sounded much better.

so i thought that test showed me they ARE in the correct phase relationship. but mixes in itunes still sound really weird.

What you did was pretty much the perfect test for checking the polarity of the two speakers. So I think you already answered your question.

When you say mixes in iTunes sound really wierd... are these aforementioned mixes ripped to iTunes with data compression (e.g. MP3 or AAC)? If so, what you're probably hearing are the artifacts from the data compression. This distortion can sound "phasey." My guess is that your new monitors are playing back your mixes with more detail, and therefore the compression-based distortion is much more evident now.

I can listen to MP3 and AAC encoded files on a crappy car stereo and not think twice about it. But when I run iTunes thru my ADAM S3A's in my studio, the same files that I sound okay on my car stereo sound really crappy ("weird") on my much-more-detailed ADAM's.

Russian Recording · Post by **Russian Recording** » Fri Jun 09, 2006 6:42 am

TapeOpAndy wrote:
amishsixstringer wrote:I had a sloppy setup once when i used two different length cables. At that point one side is delayed a bit and you get an actual phase difference that comb filters some stuff.

Neil
Speed of sound in air = approx 345 m/s. Transmission speed of an electrial signal thru cable = approx 300 MILLION m/s.

Which means moving your speaker a millimeter back will have about as much effect on timing as increasing your cable length by a kilometer (speaking in orders of magnitude).

Dang, you must've been using some pretty long cables to hear comb filtering due to cable-induced delay. Either that, or your ears can hear comb filtering of frequencies in the MHz.

There is a delay/change in sound present when using drastically different cable lengths but it is more due to the change in impedance of the speaker cables I've seen/heard this happen in PA setups where it is more common to use varied length speaker cables. For example when your amp racks are on one side of th stage and a short cable is used to get to the closest speaker and a 150' cable is used to get to the other one.

philbo · Post by **philbo** » Fri Jun 09, 2006 10:21 am

LewKellogg wrote:If you feed the same sine wave to both speakers and flip the phase you should get no sound unless something in the chain is different or colors the tone. The good news is that you're not hearing things... _ Something actually appears to be wrong.

Look for differences between the two signal paths.

It would be an amazing speaker system that would actually do a complete cancellation of sound due to out-of-phase sine waves. I don't think such speakers exist, AFAIK...

Complete cancellation IS possible in the electronic domain, but extremely unlikely in the acoustic domain.
________
FETISH LESBIAN

Russian Recording · Post by **Russian Recording** » Fri Jun 09, 2006 10:26 am

philbo wrote:
LewKellogg wrote:If you feed the same sine wave to both speakers and flip the phase you should get no sound unless something in the chain is different or colors the tone. The good news is that you're not hearing things... _ Something actually appears to be wrong.

Look for differences between the two signal paths.
It would be an amazing speaker system that would actually do a complete cancellation of sound due to out-of-phase sine waves. I don't think such speakers exist, AFAIK...

Complete cancellation IS possible in the electronic domain, but extremely unlikely in the acoustic domain.

if you face two speakers that are outputting the same thing only 180 out of polarity directly at eachother they will cancel entirely as you bring them very close to eachother. Try it!

mike

Ryan Silva · Post by **Ryan Silva** » Tue Jun 13, 2006 5:33 pm

I had the same reaction to my Event ps8's but I think that?s because they F%$#ing rock, where as my old monitors did not.

Good Luck
and
Congratulations

Post by **TapeOpLarry** » Wed Jun 14, 2006 3:39 pm

I doubt it'ss the case, but sometimes speakers can be fucked up inside in that the driver and tweeter are out of phase with each other, or even just one side of the pair...

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