# 6-9dB boost to 47 hz... bad idea?



## PTAaron (Feb 16, 2012)

I was just playing with REW in preparation for doing some corrections with a DSP1124P. I have a bit of a hole at 47hz - and I can make it nearly flat with a 6-9dB boost filter (depending on which sub location I use) at that point. My concern is: am I going to do damage to my sub by doing that? 
I have an Elemental Designs A2-300 - ported sub supposed to be tuned for 20Hz according to the website... so it seems to me, with my limited understanding, that a boost to 40hz should be safe. Right?


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## tonyvdb (Sep 5, 2007)

It should be fine to add the boost however the A2 300 does not have a very powerful amp and you will need to listen to it to see if it causes the sub some stress.

Have you tried different placement of the sub in your room? sometimes moving the sub can halp dramatically.


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## PTAaron (Feb 16, 2012)

Thanks for the reply!
Yeah - the amp isn't too powerful, that was why I was unsure...

I played with a few different positions and the best position, being the one I like the least aesthetically, is the one I was playing with making filters for.

I expect that my measurements will be different once I use my new EMM-6 microphone instead of my RS SPL meter as a mike


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## tonyvdb (Sep 5, 2007)

The RS meter is not that bad actually for the low frequencies. Where you get lousy is above 3kHz The EMM is great for full frequency readings.


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## PTAaron (Feb 16, 2012)

This is the graph I was playing with when learning to create the filters:










In the front corner, which is where I would prefer to put it, it did this:









That looks too hard to correct...


The best measurement was one foot forward from my current seat location with the sub under the TV, but it isn't practical to move my seating forward right now.


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## Phillips (Aug 12, 2011)

PTAaron said:


> This is the graph I was playing with when learning to create the filters:
> 
> 
> 
> ...



I personally would look at making cuts up to about 35hz before boosting. Then that might result in making a smaller boost. Always look at the waterfall graph as well, like you have, from about 300hz down.

Moving the sub is the best for starters, then look at cuts vs boosts.

Another great feature is the spectrogram, like the waterfall, but looking from the top.


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## PTAaron (Feb 16, 2012)

Thanks for the input! I have spectrograms and waterfalls for all of the measurements I did that day... tons of information in those, I understand _some of it!_
The first thing REW automatically did was put 2 cut filters to bring down the first 2 peaks, then I added in one to bump up the 45-ish area.

Those graphs were made with the signal going directly to the sub - but the sub will be crossed over at 80hz when it is actually in use with my system. I plan to get some new numbers with the signal going through the AVR this weekend - hope to be able to post them up Sunday.

On that note - here is the waterfall from the "original position" - which is at the end of the couch against the side wall about 4 feet from the front wall:









I may be wrong, but it looks like the front of the room waterfall drops off faster than the "original position" - but again the much larger hole in the 45hz range looks like it will be too hard to correct unless I cut everything else back and bump that up a bit. On the plus side it is a corner location, so I will get some SPL gain without having to drive the sub as hard...


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## PTAaron (Feb 16, 2012)

These are some of the graphs I was playing with... taken using the sub in "front of the room" position when I was trying to find the best location. I just want to make sure I'm on the right track with what I'm thinking...


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

Yup – looks like you’re indeed on the right track. :T

Regards, 
Wayne


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