# Freq Boost Question



## Guest (Feb 9, 2008)

Hey guys, I was reading that a 3db boost down low takes alot of your sub. But they said a higher freq boost would not tax it as much.

I have a new PB13 Ultra, so it's plenty capable; driver and amp wise... 

I have a narrow 63hz null that needs about a 20 db boost. (I cannot move the sub)

How much of a freq boost @ 63hz can I ask of my sub?


----------



## plundstrom (Nov 5, 2007)

NismoZ said:


> Hey guys, I was reading that a 3db boost down low takes alot of your sub. But they said a higher freq boost would not tax it as much.


3db means always double the power, it's not frequency dependence. Of course subs have less "reserve" is lower frequencies, so in that sense you need "more".

Nulls comes because of room and applying more power is little help. Better is look for new location for the sub or adding another sub to other location. REW is good tool to start.

ps. 20 db means 100 times the power. If at high play you are taking 100 Watts for other frequencies, then boosting your 63 Hz to same level needs 10 kW  and even PB13 can't deliver that.


----------



## Guest (Feb 9, 2008)

Can't move the sub... So, would a 10db on 63 be alright?

Just for testing, I put a 10+ db gain boost on 63hz. It brought my curve within 5db of my target. So, if I leave it at a 10db boost, what will I be hearing on movies when it hits 63 hz. A less clean sound? A chance of blowing the driver or amp?


----------



## brucek (Apr 11, 2006)

> So, would a 10db on 63 be alright?


No......

If you boost the signal at 63Hz by +10dB and it's not clipping the BFD's output, it means that the maximum input level that you've setup into the BFD is obviously -10dB down from the maximum allowed.

Why is that?

brucek


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

NismoZ said:


> Can't move the sub... So, would a 10db on 63 be alright?
> 
> Just for testing, I put a 10+ db gain boost on 63hz. It brought my curve within 5db of my target. So, if I leave it at a 10db boost, what will I be hearing on movies when it hits 63 hz. A less clean sound? A chance of blowing the driver or amp?


I believe all SVS subs have built in limiters, and from what I’ve seen with the few I’ve had the opportunity to use they work very well. So there is little danger of doing any permanent damage to your sub. IOW, the electronics will compress the signal at 63 Hz if it tries to run higher than the amp’s capabilities. The audible effect will probably be a sudden, momentary reduction in signal level – at least that’s what my experience with SVS has been.

That said, depending on how narrow your null is it probably isn’t audible anyway, so it may well be a waste to try to equalize it at all. We’d be able to better tell if you’d post a graph here.

Regards,
Wayne


----------



## Guest (Feb 10, 2008)

The width of my 63 filter is 1(smallest) in bandwidth... So it may not effect me to leave the deep null alone...

This is a graph of what I have so far... Blue being before BFD, red being after filters placed. As you can see I have inquaged a +10 gain on 63hz and +4 gain on 90hz to bring some nulls up. This is at -35 vol. I normally listen to movies at -25, no more then -20... So, should I keep those +gains or take em out?


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

I’d ditch the 63 Hz one. Anything that requires a 1/60-octave filter shouldn’t be equalized, especially upwards. Just to give you some perspective of how narrow that is, there are only 12 musical notes in an octave (i.e. 1/12-octave).

By the way, hope you aren’t EQing any frequencies above your sub’s crossover point.

Regards,
Wayne


----------



## Guest (Feb 10, 2008)

My Pioneer 811S AVR only goes to 100hz x-over. So, I can' set it at 80... Will be fixed on next AVR upgrade Would you keep the one at 90?


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

Yes, I would.

Regards,
Wayne


----------

