new setup trick!

[DrWho]

So I was at my friend Rich's house the other day checking on the setup of his Tannoy surround sound system...

Using all the tricks in the book we simply couldn't get his subwoofer

dialed in. We were messing with the phase, speaker position, volume,

every crossover setting imagineable...it just sounded like crap. After

about an hour we were really stretching for ideas so I decided to put

everything back the way he had it and then pulled out a mental pad of

paper and pencil and started running through the side-effects of every

possible setting.

Ultimately I decided that his dual 10" sub tuned to 20Hz had to have

tons of group delay so I did a few calculations and decided on moving

the subwoofer 4 feet ahead in time (~4ms). I'm not sure if the effects

were more a result of the phase response (90 degree shift at 80Hz) or

the time-alignment, but the change in sound was very dramatic. We both

looked at each other and were like "no way!" so we tried messing around

with different distance settings on the sub and always ended up with

the same 4 foot difference. The sub is 9 feet from the listening

position, but we had it set to 13 feet on the reciever. Setting it to 5

feet sounded worse regardless of the 180 degree phase switch which

leads me to believe the time-delay was a big factor - contrary to popular belief []

I'm not sure if others have tried this before, but I thought it was way

cool and just had to share the experience. It's definetly being added

to my bag of tricks.

And for the sake of being complete we ended up setting his mains to

large even though that deviates from my suggestion of always setting

everything to small. Rules are meant to be broken [H]

[Guest " "]

DrWho

So the distance setting on the HT reciever is not one of just independent volume adjustment, it also can be used to tweak time alignment issues?

Mine are set to very strange settings as well, didn't realize I was tweaking time alignment issues.

[DrWho]

I was always under the impression that the distance setting is only for time-alignment purposes and had no effect on the volume of the speaker???

If that were true, then setting the distance further away should result in increased output, but we had to turn the sub up even more...meaning the output went down in some way (probably phase cancellation).

[Jay481985]

Oh btw when does group delay become prevalently noticable on subwoofers?

[DrWho]

The number that seems to be floating around is keeping it under 40ms, though sealed subs with the same frequency response and only 10ms of group delay are supposedly much cleaner sounding, so I imagine the threshold of audibility is much lower.

[Jay481985]

I am guessing the lower in hertz the less we really care about group delay?

[DrWho]

I'm not really sure...though I do know that the lower in frequency the

less we can do about it. Just don't be obnoxious and implement 20dB of

gain at the tuning frequency in a really small cabinet...

[Jay481985]

not at all..... I just was modeling an 8 cubic foot design with three pr and the group delay shot to 20 @ 20 hertz and exponentially increased. I think it hit something like 60 at 15 hertz. silly pr being 5th order and so.

[Guest " "]

DrWho

It would be great if manufactures included a glossary in their owners manuals that got real granular as to what all these settings are really doing. They seem to differ between manufactures.

On my onkyo's the distance settings changes the loudeness as well. Meaning you could line up all the speakers in a straight line 5 feet apart and even thought the last speaker was 35 feet away, you could use the distance setting to even the volume out to the level of the first speaker, and everything in between.