Speaker Phase and room accoustics?

[Stevebez]

Well I inadvertantly switched phase on one of my front channels and the bass "hole" in the middle of my room disappeared!

Its very odd. Normally the phases are such that its push-push and not push pull - the push pull causing the cancelaltions ... so I am a bit confused why in this case one speaker in phase and one opposite phase sounds more "full" and better throughout the listening area in the bass region.... has this got to do with room accoustics - as it has surprised me somewhat?

Anyone else found this ??

Rgds Steve.

[Andrew M Ward]

Fascinating...

Well,
you've got my attention, i've never experimented with phase, other than when showing in a demo that a speaker is "out of phase"

I'll play around and get back to you
-Andrew

[greggz]

Is it possible that your sub was out of phase with your speakers causing cancellations and switching the speakers reveresed that? Do you get the same effect if you put the speakers back the way they were and change the phase on the sub?

[Andrew M Ward]

Oooh!

You guys are pretty smart, I never considered that!


(or does that mean I'm not very smart?) 8O

[Stevebez]

Further check...

The gap in the sound field was orginally discovered when calibrating the DD12 and I was moving around the room trying to find the best over all setting - then I noticed in the middle of the sound field (middle of listening area) there was a distinct bass "void" all too eveident. I never noticed before as I only really have one listening position.

So I disengaged the sub completely and had a listen to the fronts switching phase back and forth ... mmm with one "out of phase" bass was definitely uniform and complementary from both units, with both units "in phase" it became more and more vague the closer you moved to the centre of the sound field - giving the wave cancellation all the more chance to show itself.

So I either have switched wiring in my speaker units, a processor which has gone awol, switched cable labeling - or I am dyslexic ... or all of the above. :roll:

I will recheck all cables / connections etc etc once more in case I am making a huge blunder.

I was wondering if it cannot be delay settings in the processor...??

It cannot be right ... it must be a mistake... ...

I'll be back.

Rgds Steve

[Ash]

what is phase??

what is push, push or push, pull?????

[herotongtong]

Ash

ASH have you heard the song "push ,push in the push " by donna winner ??? thats all about some good songs !! you don't know that song ?? ..should listen to it

[Stevebez]

Ash...

Phase is the synchronisation of the sine waves from the speaker drivers. In phase means the sine wave crest or push from both cones are synchronised so both cones push at the same time and pull at the same time... when they are out of phase one cone is pushing while the other is pulling resulting in two equal and opposite sine waves at 180 deg to each other. In ideal circumstances these waves would completely cancel each other out - i.e. no sound at that frequency - it most happens at low frequncies as the wave lengths are so long that to get the waves opposite is actually not that difficult. High frequencies are more difficult as the sine wave crests are so tightly packed together so to get cancellation is very tough but theoretically could also happen.

Noise canceling headphones use this principle to make a quiet background.

Hope that helps.

Have not had chance last night to go check wiring etc for the 3rd time but will try do so tonight.

Rgds Steve.

[Stevebez]

OK resolved the problem ...

Boils down to incorrect rear diagram description of my amp on its website and in the manual. Due to the amps location I have to connect the speaker leads "blind" so took the manual's description as being correct...

The left channel phases are switched in the manual & website.

So all is well and normal science as we know it has not been rewritten!

Rgds Steve.

[Ash]

Thanks steve that gives me some idea of the topic.

Happy to hear that you resolved your problem.