Subwoofer SPL levels and THX optimizer

[Philip Newton]

Ok I have read many past posts about the setting of speakers with the spl meters but could not work out what was the best way of setting up the system. Firstly I was wondering if I use the test tones on my amp (sony 475) do I set the sub the same as the speakers e.g 75db. I read that the spl meters are not that good at low levels, and I saw that there are some adjustments you can make. In the FAQ it says to set sub at 85db has an adjustment already been made for this etc. Secondly is it better to use THX optimizer and what setting should I use e.g. does it adjust for the sub aswell. A simple answer must be available.

Set all speakers to 75db thats including the sub, then you can adjust the bass from there, 75db is a good starting point, you can then increase/decrease the bass from there..

Test discs include a tone for the sub.

[Jase]

Hi

If you use the test tones of the amp set all channels to 75db inc. the sub. If you want, you can set the sub channel to whatever suits you, some people have it set lower, others higher, it´s down to personal taste.

For more accurate balancing use a test disc such as AVIA or Video Essentials.

AVIA

Video Essentials

If you use AVIA set the channels to 85db, for Video Essentials set to 75db.

[Philip Newton]

is it better to set the volume on the sub itself lower and use the amp to tune it to 75db or the other way round, it is set at 12 o clock on the sub itself crossover at 150 and the bass is realy nice on some discs but on others it is so loud that it causes the problem I described in my other post. I thought I could fix this by setting it below 75db but don't want to move away too much from refrence level. thanks again I am grateful of your responses, one day i will be wise enough to help you guys.

[Jase]

I tend to set the volume on the sub to around a third, half way and adjust via the amp.

What speakers have you got? Are they satellites?

150Hz crossover seems a bit high if they are not.

[Jase]

Also depends how you have them configured, Large/Small etc Bass to both etc etc

[Philip Newton]

all set to small with mission cinema 6 all 5 are ok just probs with intrusive bass

The frequency on the satellites are rated at 85Hz for Mission Cinema 6, try turning down the crossover on the sub to 90Hz/95Hz and setting the sub at 75db again.

[Ian J]

150 Hz is too high. Try 100Hz or a bit lower if possible as the main speakers can normally handle these frequencies better than the sub. Also bass is only non directional at low frequencies and you can probably hear where the bass is coming from.

I find the test tones useless for setting the sub and do it by ear.

[Philip Newton]

you guys sure do know your stuff!! will try it tonight, I doubt my ears are able to set the sub so will rely on spl for time being, do you think this will reduce the problem i have with over working the sub?

Originally posted by Philip Newton
you guys sure do know your stuff!! will try it tonight, I doubt my ears are able to set the sub so will rely on spl for time being, do you think this will reduce the problem i have with over working the sub?

Yes, you have too much mid range going through the sub.

[Philip Newton]

silly question but my crossover goes from 50 to 150. in terms of position e.g. 12 o clock what time should my dial be at for 90/95 hz cheers as it is hard to tell as it is not graded

[Ian J]

Originally posted by Philip Newton
I doubt my ears are able to set the sub so will rely on spl for time being,

It's fairly easy. Turn up the volume on the sub until you can just hear it then turn it down a bit and possibly a bit more as well. It will take a while to get it right.

Originally posted by Philip Newton
silly question but my crossover goes from 50 to 150. in terms of position e.g. 12 o clock what time should my dial be at for 90/95 hz cheers as it is hard to tell as it is not graded

Try 12o'clock, you can check your crossover if you have a dvd with THX optimiser on it, this has a frequecy sweep on it, if not rent Cast Away or Star Wars think these have it on. Run the sweep this will tell you if you have got the crossover about right, if there is a gap in the sweep then turn the crossover up.