Flat Response??? (1 Viewer)

[Jassen M. West]

After doing some searching i'm still lost as to how to get my system to have a flat response that i read about. I have AVIA and a RS SPL meter. I just bought an Onkyo TX-SR600 and want to get everything perfect. sub is an SVS 20-39 PC (improved driver). I tried the test tone on the disk that starts high and goes down to about 20.39 it seems as though the meter stays about the same until 75 where its goes up until about 70 then it peaks again when the tone reaches 40 and stays there for awhile before dropping slowly. I have no clue what this means or how to fix it. How do i use the phase dial on the amp of the sub, is that what i need to use to fix it? i did move the phase around and it did seem to affect what the SPL meter was showing. I'm assuming i want the SPL meter to stay the same while the test tone dips lower and lower but how do i do that?
thanks for the help,
jay

 

[Mike Poindexter]

Jay,

It is virtually impossible to get a truly flat frequency response, especially at lower frequencies. While a well made speaker will be very flat in the upper frequencies, the bass is determined a lot by the room and standing waves can change your output. If you have standing waves, you would only be able to change it with some bass traps or with a parametric EQ. Also, all woofers/subs will roll off starting at some point and lose volume output as the frequency drops. There is no way around this. The better performing subs usually start rolling off at a lower frequency.

For a flat frequency response for the sub, place the sub where you sit and run the test in different locations in your room. Wherever it sounds best, place the sub there and see how it performs from your seat. Then, adjust your knob on the sub to get the output level you want to match with your mains and surrounds.

 

[Kevin Deacon]

Do a search on Behringer Feedback Destroyer or BFD

 

[John F. Palacio]

I'm assuming i want the SPL meter to stay the same while the test tone dips lower and lower but how do i do that?

This would be the ideal situation but in real life it is seldom, if ever, the case.

What you are experiencing is peaks and dips due to room resonances. Repositioning the sub can help this. You should consult SVS, ideally sending them a diagram of your room with dimensions and they will advise best spots for your sub.

An equalizer will also help if after all this you still have significant peaks and dips. I gather form your post that you have a 30dB variation (from 75 to 40) if I am reading it correctly. This is definitely not ideal.

Be aware that if you are using the Radio Shack meter, it is not very linear at the low end and you need to add a compensating factor to obtain correct reading. Having said that 30 dB is still a lot.

 

[Jassen M. West]

Actually at 75hz it peaks up to 78db for about a 5 hz countdown to 70hz then the needle goes back to reading about 68db when the Avia disc gets to 45hz (i don't know if i'm getting the hz designation correct, its the sweep pattern on the avia disc) then from 45hz to about 37hz it peaks again at 78db then from 37hz all the way down it stays even at about 68db. i hope i explained it better this time. thanks for your answers so far i have learned some new things.

jay