# A Question about Boosting



## Guest (Dec 7, 2006)

I have opted to boost my very capable sub (Monolith) by +5db at 25Hz and +5db 35Hz to go some way towards countering a room induced dip. I decided to apply these boosts rather than cutting alone because the peaks further up the frequency range were significant and would require large cuts across a broad range to bring the levels close to that of the troughs.

Since applying the boosts (and cuts elsewhere) I have listened to a number of bassy movies and music at the highest volumes my system will likely ever see (circa -16db on a Denon 3802). The pre-eq sub gain was at about 9 o'clock and the post-eq sub gain is at about 11 o'clock. It sounds fantastic, I cannot perceive any signs of driver strain and there is no output clipping of the BFD. The loudest scenes result in the highest green and perhaps a flicker from the orange light.

I have read a number of posts and opinions on the subject of boosting low down and have gathered that some are dead against it. However I am presently of the opinion that boosting as low as 25hz by +5db is not a bad idea if need be provided that the sub can go that low, has plenty of head room and does not receive a clipped output signal from the BFD.

What is the general consensus about these boosts? I am very happy with the sub's tweaked response and do not believe that I am damaging the driver due to the boosts. However there is a distinct possibility that I do not fully understand the implications of boosting low down and will remove them if the anti-boosting brigade deem the boosts an absolute no no :rolleyesno:

I would appreciate some informed opinions about boosting in my circumstance :T


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## brucek (Apr 11, 2006)

> I would appreciate some informed opinions about boosting in my circumstance


Since you're boosting +5dB without any clipping of the BFD's output, I guess we can safely say that the input level is at least -5dB lower than maximum allowed. It must be so, because if the input level of the BFD is at maximum then *any* boost will clip the output at that frequency.

Often if there is only a single dip, and it responds to boost, then it's a matter of simple convenience (at the expense of dynamic range and S/N ratio) to use a single boost filter instead of spending quite a bit of time cutting everything around that dip.

I would think that a situation where there were multiple dips and mutiple peaks, that in the face of equal amounts of effort in creating filters, it would be judicious to choose only cutting. The results will produce the identical output from the BFD, but with better specs.

brucek


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## Guest (Dec 7, 2006)

thank you brucek for your valued opinion, much appreciated as always :T


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## Josuah (Apr 26, 2006)

Right. If the boost is actually working then it's not a room null. And it also means you are only driving the sub with at most 1/4 the watts across the rest of the range. If instead you applied the cuts across the spectrum as needed, you could safely drive the sub +5dB greater than you are currently doing.


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## PeteD (Sep 9, 2006)

Josuah said:


> If instead you applied the cuts across the spectrum as needed, you could safely drive the sub +5dB greater than you are currently doing.


I don't believe this is true. The BFD can pass only a certain strength signal. If you reduce the input level (required to add boost without clipping the output), the boost will bring you back up to the same point leaving the BFD. In fact, if you are using large-scale cuts, you may decrease your sub output significantly by cutting your BFD output signal way down (first-hand experience on this one).

As brucek correctly stated above, the potential output is the same, but the signal to noise ratio suffers from boosting. He could safely drive the BFD (input) at +5dB more than he is doing by using only cuts, improving the S/N ratio. If you get sufficient output from your sub using just cuts, then just cut.

Pete


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## Josuah (Apr 26, 2006)

I think you're right, and my brain isn't working right.


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