Phase shift (1 Viewer)

[Troy_j]

Isn't it true that a 180 pase shift will be introduced if you wire a speaker + to- the amp + to +. I'm wondeing about a way to introduce phase shifting into a n amp that isn't set-up for it. Also how inportant is it anyway?

Thanks am planning on driving a Tempest with a mono carver m1.0t.

 

[ThomasW]

Depends on the phase relationship between the amp and the speakers.....

If 'in-phase' wiring is amp +/- to speaker +/-, then 180 degrees out of phase is amp +/- to speaker -/+

It's important to have the sub in-phase with the mains because if they aren't, the frequencies that overlap will be cancelling each other =less bass.

A quick and easy way to check phase is to play something with a fair amount of bass energy. Using one hand gently place your finger tips on the edge of sub surround. Place the other hand on the edge of the surround of one of the mains. If they are moving in and out at the same time the speakers are in-phase

 

[Dave Milne]

wire a speaker + to- the amp + to +.

You can't wire the speaker "+ to +" unless the amp is set up for bridging...

 

[Troy_j]

What I meant was Red binding post speaker wire from receiver, going to the red binding post on the driver. E.g. red to red, and black to black, for say the left channel; that would normal, and " in phase." And conversely if the red binding post from the receiver wire going to the black binding post of the driver; would be 180 out of phase. I hope I'm making sense, and also this is for only one channel:b
Just Taken from:
www.hifi.com/store/category.cgi?category=hookup_connection_gen

"The speaker cable is coded with a bead or stripe down one lead's insulation, or has different colored wires. Connected identically, all speakers will operate "in-phase."

 

[Dave Milne]

Troy,
I thought that might have been your intent. And you're right, connecting the red amp terminal to black speaker terminal will put it 180 out of phase.

As to which connection is best for your system... that's a bit more complex. Phase angle is a "moving target" because of the phase shifts introduced by the crossovers and the speakers themselves. About the best you can do is try to pick the closest phase match at the crossover frequency and hope that it doesn't deviate too much in the "overlap region". For example, the second-order, 80 Hz "THX standard" crossovers are only down 12dB an octave on either side (40Hz to 160Hz).

The simplest way to select proper polarity is to play a test tone at the crossover frequency through the system. The subwoofer polarity that yields the highest level at the listening position is generally best. A better approach is to measure the frequency response of the system (from the listening position) with both polarities and select the flattest one.

Finally, with all due respect Thomas, I can't imagine that your fingers are sensitive enough to tell if drivers are moving in or out at any usable frequency. I wouldn't trust any of my body parts to differentiate 6 ms (half-wavelength at 80 Hz).

 

[ThomasW]

Finally, with all due respect Thomas, I can't imagine that your fingers are sensitive enough to tell if drivers are moving in or out at any usable frequency. I wouldn't trust any of my body parts to differentiate 6 ms (half-wavelength at 80 Hz).

Well call me 'Mr Sensitive' ....... I just played the 'Blueman Group' CD. Placing one finger on the surround of the one of the woofers in the IB sub and another on one of the midwoofers, it was pretty obvious that the drivers are in phase.
BTW they are also in phase checking with a basic 'battery test' and with a more involved sine-swept Clio plot.
Since Troy has 2 only options in-phase or 180 degrees out, it didn't make sense to cloud the issue with a info regarding phase angles. I must be getting lazy in my old age

 

[Troy_j]

Thomas,and Dave Thank you both. Each of your responces shed light on my question, and I appriciate it. I never did understand why my parents amp had a " phase" dial............