Sub integration problem

[davidwb]

I just received a PSA s1500 sub to go with my Sierra Towers (w/ RAAL), and after using the REW software to level match the Towers and the sub, it sounds great -- very well balanced. BUT, the only way to get the levels matched is to run the sub at virtually full gain! My prior (and much older) Velodyne sub could be level matched at only about 70% of full gain. They are in the same spot in the room.

Any thoughts on what could be the problem (if it is a problem)?
Thanks for your thoughts.

BTW -- the Sierra Towers sound better each time I listen to them!

[enricoclaudio]

Do a subwoofer crawl to find the best spot for the subwoofer. Most probably your MLP is in a null and the only way to fix that is changing the subwoofer location.

[davidwb]

That's what I thought as well, so I tried the sub in 3-4 different locations in the listening room including in the corner facing the MLP, all with the same result -- to get the same sound level as the Towers (measuring 0 on my Radio Shack meter with C weighting), I have to turn the gain on the sub virtually all the way up. It still sound great, but this can't be right. Can it?

[Beave]

What amp/preamp or receiver are you using?

[davidwb]

I'm using an Apt-Holman pre-amp (so no test-tones there, that's why I'm using the REW software on my laptop) and the Emotiva A-300 stereo power amp (150 wpc, 20-20k).

As for the REW software, I'm running pink noise at the -3db setting using the subwoofer setting for the sub and full for the Towers.

[davidwb]

More information:
I re-ran the entire process, and noticed that the output from my laptop (which goes out to the pre-amp through a 3.5 mm to dual RCA plugs) was registering a very low "3" level (it runs from 0-100). When I have my laptop in its cradle and attached to Audioengine speakers, it registers at 100 (max) and the volume is adjusted completely with the level control on the speakers.

So, I turned the gain up on the PC output about halfway, and when I repeated the speaker level adjustments, the sub now could be run at about 75% of its full gain rather than the nearly 100% previously (remember that the PC was providing the same input levels to both the sub and the Towers).

Question: should I turn the PC output gain up to 100 and allow all volume adjustments to be done through the REW software (ensuring that both the sub and the Towers are getting the same sound levels) and then adjust the volume of the sub to equal that of the Towers?

Thanks.

[N Boros]

If it were me and it sounds fine and measures fine and you don't hear a hum from the sub because you have the gain all the way up, I wouldn't worry about it.

You might just call customer service over at PSA to give you piece of mind, but it is likely because you don't have gain adjustment in your preamp to help out.

[davidwb]

it sounds fine and measures fine and there is no hum...and I have a call into PSA! I'll let you all know what they say.

thanks

[davidwb]

and the folks at PSA say that running it at 75% of full gain is not a problem...although they suggested that I turn up the output gain on my PC (although not to 100%...perhaps to 90%) to make sure there's enough signal to get good readings for the mains and the sub.

so, I have one more iteration and then I should be good!

[MusicHead]

You only mention level, but could it also be an issue with phase? Whether you adjust the sub to MLP distance in your pre-pro/AVR settings or adjust phase it manually with the switch/knob your sub has, that also has an impact.

[N Boros]

You only mention level, but could it also be an issue with phase? Whether you adjust the sub to MLP distance in your pre-pro/AVR settings or adjust phase it manually with the switch/knob your sub has, that also has an impact.

Good point. Here is a guide I thought was very helpful to calculate this beforehand and then just set the dials accordingly:

http://www.rythmikaudio.com/phase1.html

[davidwb]

You only mention level, but could it also be an issue with phase? Whether you adjust the sub to MLP distance in your pre-pro/AVR settings or adjust phase it manually with the switch/knob your sub has, that also has an impact.

I'm using a 2-channel pre-amp and not a pre-pro or AVR...so there are no settings on it. But I will play with the phase setting this weekend and see (hear?) if that makes a noticeable difference.
Thanks