setting gains

[n2audio 5,000+ posts]

yea but im saying if I have my sub playing at max potential with a 50hz tone (with a box tuned to 32hz)... whaddya think is gonna happen at tuning... its gonna be playing WAY past max potential... I would think you should use a 30hz tone to tune a 32hz box.. that way, you know your sub won't play any louder than that tuning frequ.

The reason 50 is commonly used is because that represents a frequency that "typically" will have the subwoofer presenting something in the neighborhood of its DC resistance to the amp - which is what you used to determine the desired voltage. It doesn't really matter much - if the amp produces 10v at 50hz 0db it should produce 10v at 1000hz 0db. The idea is just to use a freq that's somewhere in the amplifier's range -- you wouldn't want to use 1k for a sub amp.

 

[Haunz 10+ year member]

^ If you are trying to get away from fb so you know the load is consistant with the subs nominal impedance I'd tend to move as far away from fb as possible... like 100hz +

It is a good point that depending on the frequency your results will vary according to impedance rise and rail sag... (and 50hz might not be a good freq to use)

I don't bother setting my gains with a dmm but if I did I think hooking up a non inductive load might be the way to go....

 

[n2audio 5,000+ posts]

To JL CS:

On 8/13/08 9:12 AM "Justin ****" wrote:

Your tutorial says to use a 50hz tone to set the gain on my sub amp.

I’m just curious – Why 50? Why not, say, 35hz (closer to the tuning frequency), or 80 hz?

Thanks,

Justin

JL's Reply:

You want an unweighted signal that’s close to being in the middle of the bandwidth that that amplifier is working with.

Ward Benjamin

JL Audio Tech Support

10369 N. Commerce Parkway

Miramar, FL. 33025-3962

http://www.jlaudio.com

954-443-1100 ext.2146

wbenjamin@jlaudio.com

 

[Haunz 10+ year member]

^ that tutorial is a piece of shit.... and I am not confident that anyone at JL's C.S. has a clue what they are talking about....

using a freq in mid bandwidth does make sense because the amp will put out the most power there.... but IMHO the reason to tell people to use 50hz and not some other freq is because cheap meters are calibrated for and will only be accurate around 50-60hz...

good luck setting gains accuratly with a non RMS meter and a 1khz tone... (not to mention with no load on the amp) //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

 

[n2audio 5,000+ posts]

Oh, sorry - I wasn't aware you are THE authority on all things audio.

I'll try to remember to defer any questions to you in the future - especially since JL has made it obvious to everyone they're clueless on the subject.

//content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

BTW -

The typical DMM IS an RMS voltage meter.

Check your wall voltage - is it ~170 or ~120?

 

[Haunz 10+ year member]

^ a typical meter will read 170 but is calibrated to show 120 on the display when presented with a 60hz signal...

If you new what you were talking about you would know that a true RMS meter uses a wire element to measure the actual heating value of the signal..... typical meters do not do that...

I wouldn't call myself the authority on anything... but common sense and a little knoledge can obviously go a long way.... I really have no idea why JL would put that up on thier site, but I have a feeling their marketing department was more involved with it then the engineers that work in R & D....

 

[Buck 5,000+ posts]

or you can just slowly turn the gain down until your sub blends in with the rest of your speakers nicely. easy as pie, no DMM, no test tones.

ya no need to complicate it just turn it down some.

 

[n2audio 5,000+ posts]

^ a typical meter will read 170 but is calibrated to show 120 on the display when presented with a 60hz signal...
If you new what you were talking about you would know that a true RMS meter uses a wire element to measure the actual heating value of the signal..... typical meters do not do that... ....

If I knew what I was talking about?? You mean if I had gone googling for an explanation?

A standard DMM is perfectly sufficient - if you knew what you were talking about we wouldn't be having this argument.

I really have no idea why JL would put that up on thier site, but I have a feeling their marketing department was more involved with it then the engineers that work in R & D....

Right, because providing a simple, accurate method for setting gains is clearly a greedy marketing decision.

 

[Haunz 10+ year member]

show me the google search that I looked at where an RMS meter is explained... ?

maybe you should go get a degree as an EE or something... //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

you either know what you are doing or FAIL at setting gains....

 

[n2audio 5,000+ posts]

show me the google search that I looked at where an RMS meter is explained... ?maybe you should go get a degree as an EE or something... //content.invisioncic.com/y282845/emoticons/rolleyes.gif.c1fef805e9d1464d377451cd5bc18bfb.gif

you either know what you are doing or FAIL at setting gains....

http://www.radio-electronics.com/info/t_and_m/digital-multimeter/dmm-specs-specifications.php

Maybe you should get off your high horse or something.

 

[Haunz 10+ year member]

sorry n2, I didn't have to read any webpage to know the difference between a true RMS meter and a typical cheapie... but kudos to you for finding that page... (hopefully you read it too)

The bottom line is that if you want to set an amp's gains properly you either need an RMS meter or the tone should be at 60hz; and you should have a load hooked up to the amp to keep the rail swing realistic.....