Subwoofer question

bryan_m · 11-01-2004, 02:28 PM

Why does my powered sub have a L and R input and there is only one output from my receiver? I purchased the sub used few years ago no instructions. Would it be better to use a Y jack and make the output into 2 or just hook it into the one input. Also should I turn the volume up all the way on the sub and the frequency and make adjustments with the receiver to the sub or use the sub to make the settings?

ChadLB · 11-01-2004, 03:02 PM

General sub setup info
There are common set-up errors that could be causing some problems. Double check all of these things before you try to recalibrate:

In the AVR:

1) All speakers set to small.
2) Crossover set to 80 Hz.
3) Sub set to on/yes.
4) Subwoofer Remix or LFE + Mains set to off/no.
5) Dolby Dynamic Range Compression Circuit set to off/no.
6) LFE (0.1) channel level set to maximum (i.e., unattenuated) value (if the AVR has the capability).
7) THX (or any other) bass limiter circuits set to off/no.
8) Subwoofer channel level to -5.

In the DVD player:

1) Output set to bitstream (digital output via the digital coax).
2) Dolby Dynamic Range Compression Circuit set to off/no.

On the subwoofer:

3) Crossover switch to off.
4) Set the phase to 0 degrees initially unless you have the capability to evaluate the FR of the system.

Neil Joseph · 11-01-2004, 03:22 PM

My recommendations would be to use that y cable and take advantage of both inputs. On most subs I have seen, this results in a doubling of the output. I would not crank the sub volume to the maximum level to avoid any possible distortion generated byt he sub. You will hear various opinions on this. On my setup, I put the sub at 50% and then calibrated the receiver for the desired results.

ScottCHI · 11-01-2004, 04:47 PM

Quote:

My recommendations would be to use that y cable and take advantage of both inputs. On most subs I have seen, this results in a doubling of the output.

that's wrong. that's neither how nor where you should adjust the sub. that's what the sub's volume control and the receiver's settings are for.

don't use a Y-splitter unless you have a reason to.

John Garcia · 11-01-2004, 06:11 PM

IMO, it depends on the sub. If you have a problem with the sub shutting off during movie viewing with little bass information, using the Y will tend to give the sub enough voltage to remain on. This is how my sub is, so I use a Y.

The output will not exactly double, but by having a higher input voltage, you will see an increase in the sub's performance. Once calibrated however, that increase is accounted for and you end up with the same SPL, though using a slighly lower volume at the sub.

IMO, my general rule of thumb for sub volume is to start about 1/2 and trim using the receiver for calibration, but it depends a lot on your room and your sub's location. If you leave the sub turned all the way up it will eventually clip and you are also introducing greater distortion.

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bryan_m · 11-01-2004, 08:20 PM

Thanks for the info. As of right now have the freq set at about 80 and the volume at about 3 quarters and set volume lower on my receiver. Used a Radio Shack Sound Level Meter with the proper settings recommended. Set volume to 0 and ran the test tone all speakers at 77db even the sub all at seating postion and ear level.

Wayne A. Pflughaupt · 11-01-2004, 10:31 PM

There are some good reasons for using a “y” adaptor, but increasing output is not one of them. Using a “y” only increases the level (voltage) of the incoming signal. You can get the same effect by raising the sub’s volume control (both methods increase voltage to the sub’s amplifier section). Neither has any effect at all on output - the only way to increase a sub’s maximum output is to put in a bigger amplifier. Increasing the input voltage is not going to make a 250 watt amp into a 350 watt amp.

Regards,
Wayne A. Pflughaupt