extending bass response using an EQ

[yepimonfire]

i've often considered doing this but never tried it because i didn't want to screw my stuff up. let's say i have a pair of speakers that roll-off 3dB at 50hz, so i increase the level of 50hz by 3dB, now let's say it rolls off 6dB at 40hz so i increase the output of 40hz by 6dB then 30hz at 12dB etc. i understand that this would dramatically increase the power demands of the amplifier but my question is would i end up adding more distortion then it's worth? assuming the speakers can cleanly output 50, 40, and 30hz frequencies at 90dB or so without undue distortion.

also as a side question is it a good idea to correct a speakers response with an EQ? say use it to correct issues in the midrange and to attentuate over brightness?

 

[ski2xblack]

...i understand that this would dramatically increase the power demands of the amplifier but my question is would i end up adding more distortion then it's worth? assuming the speakers can cleanly output 50, 40, and 30hz frequencies at 90dB or so without undue distortion.

also as a side question is it a good idea to correct a speakers response with an EQ? say use it to correct issues in the midrange and to attentuate over brightness?

That's a big assumption. Speakers generally have higher distortion the lower you ask them to go, and if they're ported you can forget about augmenting frequencies below port resonance (port and drivers are out of phase at that point, so increased input will yeild no additional spl, just excessive cone motion and port noise). If your speakers are a sealed alignment and can handle augmentation, you're still pushing your amp and speakers pretty hard, with increased risk of failure by doing so. You would be better off using a sub (or two) in this case.

As for correcting response, I say go for it. From Audyssey to simple tone control adjustments, if you can make it more pleasing to your own ears, more power to you. Others will probably tell you the opposite, so YMMV, IMHO, and all the caveats.

 

[KEW]

I would have two concerns:
1) frying the crossover - you're going to be sending a lot more steady power through the crossover than it was likely designed for (I assume a standard passive crossover).
2) port tuning - if the speakers are ported, it is likely that you are adding gain in the same region as the port is tuned (often the bottom of or just below the speakers range is used for port tuning to extend the range of the speaker). I'm no expert, but I believe this would result in a very touchy system. In other words, a small increase in gain could cause an extreme increase in SPL at the ports tuned frequency. Additionally, it would be susceptible to exaggeration of music which added its own emphasis to the tuned frequencies.

Something to ask is how big are your mid-bass drivers and how loud are you talking? I would be surprised if the drivers could actually handle the lower frequencies at decent SPL.

If the speakers are sealed, they will probably take the EQ better. Here is a discussion I am aware of on pouring lots of power into a sealed cabinet, but the driver is extremely rigorous - See posts #3, 16, 18 for starters:
http://forums.audioholics.com/forums/showthread.php?t=60847

 

[TLS Guy]

That's a big assumption. Speakers generally have higher distortion the lower you ask them to go, and if they're ported you can forget about augmenting frequencies below port resonance (port and drivers are out of phase at that point, so increased input will yeild no additional spl, just excessive cone motion and port noise). If your speakers are a sealed alignment and can handle augmentation, you're still pushing your amp and speakers pretty hard, with increased risk of failure by doing so. You would be better off using a sub (or two) in this case.

As for correcting response, I say go for it. From Audyssey to simple tone control adjustments, if you can make it more pleasing to your own ears, more power to you. Others will probably tell you the opposite, so YMMV, IMHO, and all the caveats.

Correct answer. You can only add bass extension by Eq to a sealed design. You can only do this within the xmax of the driver.

 

[jinjuku]

You can only add bass extension by Eq to a sealed design.

Which has always been my opinion and why I like sealed alignments with a high quality, high power handling driver, active x-over | EQ, and quality amplification.

If you have those things you can really make a sealed sub do almost what ever you need it to do.

 

[Pyrrho]

i've often considered doing this but never tried it because i didn't want to screw my stuff up. let's say i have a pair of speakers that roll-off 3dB at 50hz, so i increase the level of 50hz by 3dB, now let's say it rolls off 6dB at 40hz so i increase the output of 40hz by 6dB then 30hz at 12dB etc. i understand that this would dramatically increase the power demands of the amplifier but my question is would i end up adding more distortion then it's worth? assuming the speakers can cleanly output 50, 40, and 30hz frequencies at 90dB or so without undue distortion.

also as a side question is it a good idea to correct a speakers response with an EQ? say use it to correct issues in the midrange and to attentuate over brightness?

In practice, it will almost never work well, no matter what basic design we are talking about. But at very low volumes, with music that is at a fairly constant level, you could try it out if you wanted without too much risk of damage, turning up the volume very slowly; just turn it down if you notice any extra distortion. If you try it, you will probably end up realizing that it does not work well, and not do it.

With the numbers you are talking about, the power demands at normal levels will greatly exceed what you would normally be dealing with. Remember, every increase of 3 dB in volume requires a doubling of power. So, with the hypothetical figures you give, you will need double the normal power at 50 Hz, four times the power at 40 Hz, and 16 times the power at 30 Hz, and etc. So at normal volumes, you will be putting a much greater strain on your amplifier and your woofer, and so most likely, it is not going to work at normal volumes. It would have to be that your system could play much, much louder than normal volume without problem for it to work (or at least the bass portion of your speaker would have to be able to play much, much louder without problems).

However, you might be able to get away with something somewhat similar, by boosting the signal at 50 Hz, but reducing the strain on the system by filtering out deeper bass. You might be able to extend the frequency response considered only +/- 3 dB, basically by causing the frequency response curve to drop off faster at the bottom end. You may or may not like the results of doing that.


As for your other question of flattening the response with an EQ, you may or may not like the results of doing that, possibly depending on how well you are able to do it.