Sub woofer phase and placement

[msrance]

Friends, could you just help me out with a few querries
1. In my Integrated amp Yamaha AX-596 there is no dedicated subwoofer out. I was adviced to use the 'rec out' output port to connect the sub. Is this is the best way out or is there some better method?
2. My Sonodyne sub has a phase control toggle switch with two possible positions of 0 and 180 degrees. what and how do choose between the two? whats the science behind this phase control?
3. What would be the best way to place a sub in a relatively small room for a 100w/c amp, specially when the room is a bit too furniture clutered and has a tendency to produce lingering boom in the music. I have a pair of sonodyne floorstanders and a sub?

[skeptic]

Friends, could you just help me out with a few querries
1. In my Integrated amp Yamaha AX-596 there is no dedicated subwoofer out. I was adviced to use the 'rec out' output port to connect the sub. Is this is the best way out or is there some better method?
2. My Sonodyne sub has a phase control toggle switch with two possible positions of 0 and 180 degrees. what and how do choose between the two? whats the science behind this phase control?
3. What would be the best way to place a sub in a relatively small room for a 100w/c amp, specially when the room is a bit too furniture clutered and has a tendency to produce lingering boom in the music. I have a pair of sonodyne floorstanders and a sub?

Using the rec out will not work well at all. This is because this output is deliberately NOT controlled by the main volume control So if you use it, the subwoofer will play at the same volume while the main speakers will play at a different volume depending on where you set the volume control. In other words, the relative volume of the subwoofer and main speakers will not remain proportional. You have a couple of alternatives. First, most subwoofers have speaker inputs. Connect the left and right speaker outputs from your integrated amp to the speaker input terminals on the subwoofer and connect the speaker outputs on the subwoofer to your main speakers. Be sure to maintain the correct polarity for all of the wires. Also be careful not to short circuit anything either. I assume your subwoofer has a built in amplifier. You have one other option. You can connect another preamplifier in the integrated amplifier's tape loop. This means connecting the Yamaha's tape outputs to an aux level input on the outboard preamp, connect Y cables or Y adaptors to the main preamp outputs, connect one set of cables from the Y output to the tape monitor input of the integrated and connect the other set to the subwoofer line level input. Put the integrated preamp in the "tape monitor" position. The preamp's volume control will control the signal level to both the integrated and the subwoofer amplifiers simultaneously. Once you have the control levels for the integrated and subwoofer set properly, leave them alone and just use the preamp volume control. (If your intgrated amp has a preamp out/power amp in with jumpers, you can forgo the outboard preamp and accomplish the same thing with just Y adaptors and an extra set of jumpers.

OK, that was the easy part. Setting the phase, volume, crossover, and locating the subs is much harder. The amount of bass you hear and its frequency response will depend to a great extent on your room acoustics, where you place the sub and where the main speakers are located. I'm sorry to tell you that this will have to be a source of experimentation. This includes setting the phase switch but normally, I'd guess on setting it to zero degrees at first. One problem with subwoofers has to do with phase cancellations and reinforcements in the frequency region where they cross over to the main speakers. Placement and position of the switch can result in very significant peaks or dips in response. The best solution is to have two subs, one for each channel and place the main speakers directly on top of them. Usually though, you are stuck with just one and have to compromise. As with any woofer, placement determines relative loudness, the corner at the floor being loudest, against the wall but not in the corner being next, and out into the room being least. Don't be afraid to experiment such as turning the subwoofer sideways aimed at a side wall.

Good luck.

[msrance]

Using the rec out will not work well at all. This is because this output is deliberately NOT controlled by the main volume control So if you use it, the subwoofer will play at the same volume while the main speakers will play at a different volume depending on where you set the volume control. In other words, the relative volume of the subwoofer and main speakers will not remain proportional. You have a couple of alternatives.

First of all Thank you for explaining the whole science so lucidly - Skeptic.

First, most subwoofers have speaker inputs. Connect the left and right speaker outputs from your integrated amp to the speaker input terminals on the subwoofer and connect the speaker outputs on the subwoofer to your main speakers. Be sure to maintain the correct polarity for all of the wires. Also be careful not to short circuit anything either. I assume your subwoofer has a built in amplifier.

Well, yes the subwoofer has a built in amplifier but then there is a difference in all power ratings so i dont know how is that going to impact the final output. The main speakers are rated at 80W @ 4ohms. The Amp outlet is rated 100W/C @ 8ohms. The powered sub is rated at 100W @ 8ohms. How are these ratings going to affect the output clarity if the above method is used. The connectors are different for main speakers and the subwoofer output. My location does not allow me to get good quality connectors here - or even lousy ones for few months atleast - so how does one tackle that?

You have one other option. If your intgrated amp has a preamp out/power amp in with jumpers, you can forgo the outboard preamp and accomplish the same thing with just Y adaptors and an extra set of jumpers.

Could you just explain the preamp out/poweramp in with jumpers thing. How does one work out the connections? besides the amplifier manual says "When you use this unit as a power amp , connect the output terminals of an external control amplifier to this units main in terminals. In this case, this units controls will not function. Use controls on external amp to make volume adjustments.". Will the sub be able to give the same level of output to the main speakers as the main amp? I still dont get which of the two amps is going to control the show? who will be finally outputiing the sound - the integrated amp or the powered woofer?