Why do Monitor 30's sound better than 40's

Ern Dog

Today I went to Circuit City to give the Monitor 30 and 40's a listen to compare them because I'm looking to purchase rear speakers for my surround system. I was very confused because the 30's actually sounded better than the 40's especially with the lows and sounded clearer on the highs!?!? Can somebody explain this because the salesman couldn't. The test was done in their listening room, the wiring was the same, the speaker positions was the same, and using the same AVR.

Please Enlighten me.

Ern-Dog

kingkip

Hey Ern,

Didn't you already ask this question in another thread? Check that out as it has some responses. BTW welcome!

*Seby*-Polk-

Monitor 30 works better for Sourround than mains....

Monitor 40 sounds better fo mains than for surrounds....

This is the true !!!!

Ern Dog

Kingkip-
Yeah, I was hopin' to get more info...
I'm a newbie to Polk and it has only been within the last 2 years that I started putting together a surround system. Due to $$$, I've had to do it piece by piece. And now I'm down to one more piece to make the system complete. While I've got your ear, in the back of my PSW10 sub there is a switch called Phase 0 or 180. What the heck is this about? I listened to both and found just a very minute difference.


Seby-
I totally agree, funny how that works huh.

Ern-Doggie

Zen Dragon

Ern Dog
The phase switch changes the phase of the output audio. A full phase or cycle is 360 degrees, also zero of the next wave, thus 180 is exactly half.
If you imagine a perfect sine wave (AC) it goes from zero up to it's peak, curves along it's peak, then goes below zero and does the same. If 2 waves are 180 degrees out of phase then when one of them is peaking on the positve, the other will be at it's opposite peak on the negative.
The phase switch on your sub allows you to change the waveform to the opposite of it's input. This can be useful if

- the sub is set-up in a way that it is primarily facing the speaker. This would cause the sound wave to naturally be out of phase and some of the sound waves may cancel
each other out

- the sub is set up in a way where it's waves are travelling together with the speaker waves. The waves would be in phase and you could hear overly loud sound where the waves overlap and reinforce each other.

There are many variables in a listening room, and generally you are experiencing a little bit more of one of these conditions then the other.
So...long explanation, easy answer. Try the switch in both positions and leave it in the one that provides the better sound. Usually one will sound just a bit better than the other.

ND13

Bigger, in some cases, isn't always better. A lot of the LSi owners prefer the 7s over the 9s.

polk_audio_lsi

Is 2 sets of dipole speakers better than having a set of dipole and a set of bookshelf?

Midnite Mick

Thanks Zen, great explanation. I learnt something new. I believe I have heard that out of phase expression when describing the crossing of the positive and negative during speaker hookup. Is this correct? Would this then suggest that if one was to do this to both speakers (2channel) it would not be noticed?

Also would your sub facing speakers example apply then to rears facing front if 4 channel stereo is selected or do processors automatically put one out of phase for this reason? I may be totally out to lunch on this but these were just my thoughts.

Mike

Zen Dragon

Midnite:
Excellent question.
First off, yes if you hook your speakers up positive to negative you would have the sound 180 degrees out of phase, and yes if you did this to both you would again have them with the correct phase relationship to each other.
You should not hook your speakers up backwards however as they are designed to work optimally with the positive and negatives hooked up a certain way.
As to 5.1 channel set-ups. I can only give a laymans explanation here as the Dolby algorythms are beyond my spectrum of knowledge. I am fairly certain that all 5.1 mixes such as Dolby and pro-logic send the rear channel signals 90 degrees out of phase with the main speakers to combat phase cancellation of the signals.
Although I have never investigated it, I would assume SACD and DVD-A formats are similiar. Couple this with the fact that in a well mixed 5.1 a lot of the information going to the rear channels should be different audio then goes to the front anyway. ie a fighter plane on screen may be heard in the fronts, while his bullets he's firing are heard in the rear.
That's about the extent of my knowledge on the subject. :cool:

Midnite Mick

Thanks for the response Zen. I would never cross both speakers as there is no reason for it I was just speaking hypothetically so as to see if I fully understood what you were saying.

As far as front to back speaker relationship I was refering to 4 channel stereo, not really 5.1. I think with 5.1 they would not be getting the same signal and usually the rears wouldn't be near as loud as the front as well, except under "special" circumstances.

Mike

AzN_plyR

Is this the same reason some people prefer the R30's over the R50's? hehe

Zen Dragon

As to 4 channel stereo. If you are using a processor or decoder, it should be performing a phase shift to correct for phase cancellation.
I believe most of the older stereo's with a "B" speaker out put all the outputs out in the same phase. This means if you set them up with 2 channels in the front and 2 in the rear you were likely experiencing some level of phase cancellation from the "A" speakers up front to the "B" speakers in the rear.

Ern Dog

Thanks for the info.

RuSsMaN

Ern Dog wrote:

Why do Monitor 30's sound better than 40's

They are closer to a single, point-source image. Small speakers (good ones) can image like motherf$%ker.