Basic Question on use of Parametric EQ

[shkumar4963]

Can I use PEQ to lift bass response of a standmount speaker? If yes, what is the limit of this approach? How much increase at lower frequencies (in db) is accoetable? For a speaker with -6db point at 50 hz and -12 db at 32 hz, can I raise 12 db using PEQ for a flat frequency response till 32 hz. That would be sufficient for all kind of music except for home theater. one negative could be danger of burning the speaker by pumping so much energy in the speaker at that low frequency. How do I estimate what is the max energy I can put in the speaker safely? For average music listening levels ( about 86 to 90 db at 1 m), is there a danger for kef ls50.

[Zaphod Beeblebrox]

Can I use PEQ to lift bass response of a standmount speaker?

Yes.

 

If yes, what is the limit of this approach?

Impossible to accurately quantify.

 

How much increase at lower frequencies (in db) is accoetable?

Again, impossible to say.

 

For a speaker with -6db point at 50 hz and -12 db at 32 hz, can I raise 12 db using PEQ for a flat frequency response till 32 hz. That would be sufficient for all kind of music except for home theater.

In theory, you could do that. In practice, a 12dB increase at 32Hz will likely cause over-excursion of the bass drivers. 12dB equates to approximately 16 (SIXTEEN) times the power.

 

one negative could be danger of burning the speaker by pumping so much energy in the speaker at that low frequency. How do I estimate what is the max energy I can put in the speaker safely? For average music listening levels ( about 86 to 90 db at 1 m), is there a danger for kef ls50.

Use a subwoofer.

Edited March 17, 2015 by Zaphod Beeblebrox

[almikel]

I agree with ZB

You could model the speaker in WINISD or horn resp to look at driver excursion to give you some idea

Be very cautious if the speaker is ported

Applying boost below port tuning is a really good way to destroy a woofer

You will also run out of amp power quite quickly

Mike

[shkumar4963]

Yes.

Impossible to accurately quantify.

Again, impossible to say.

In theory, you could do that. In practice, a 12dB increase at 32Hz will likely cause over-excursion of the bass drivers. 12dB equates to approximately 16 (SIXTEEN) times the power.

Use a subwoofer.

I understand 16 times power. So let's see if it will create a problem. For 85 db it takes 1 watt. So for 91 db (which is very loud) it will take 4 watts. And if I increase low frequencies to 12 db it will take 64 watts. The speaker can take 100 watts continuous power and my amplifiers are 100 watts continuous power pc. So it should not be dangerous for speakers or amplifier.

Now did I make a calculation mistake (which is highly likely).

[Zaphod Beeblebrox]

I understand 16 times power. So let's see if it will create a problem. For 85 db it takes 1 watt. So for 91 db (which is very loud) it will take 4 watts. And if I increase low frequencies to 12 db it will take 64 watts. The speaker can take 100 watts continuous power and my amplifiers are 100 watts continuous power pc. So it should not be dangerous for speakers or amplifier.

Now did I make a calculation mistake (which is highly likely).

Yes. 91dB is not "very loud".

Moreover, you're forgetting the impact of peak levels. These can easily be 20dB higher than the average levels you are estimating.

Use a subwoofer and save yourself heartache.

Edited March 18, 2015 by Zaphod Beeblebrox

[almikel]

Hi Shkumar

Yes. 91dB is not "very loud".

Moreover, you're forgetting the impact of peak levels. These can easily be 20dB higher than the average levels you are estimating.

Use a subwoofer and save yourself heartache.

 

average vs peak is a big deal - even if the average to peak ratio was only 10dB (and ZB is right, 20dB can be typical on well mastered music), a 100W amp is on the verge of clipping at 10W average - so adding 12dB of gain down low is almost guaranteed to clip the amp.

 

Your speakers also have a rear port - if you add gain below port tuning, the excursion increases dramatically and you'll break. the driver - quickly.

Ported boxes and tapped horns need a high pass filter to avoid over excursion below tuning - ignore at your peril.

Also excursion = distortion, so pushing a driver to operate at (or beyond) its safe Xmax will increase distortion significantly.

 

Not entirely on topic, but Rod Elliot has a good article that discusses average vs peak power and why tweeter's blow when amps clip

http://sound.westhost.com/tweeters.htm

 

I do run a load of PEQ on my mid bass drivers (about 12dB) to push them down lower, but only after I modelled the excursion and felt comfortable that I wouldn't exceed their Xmax limits, or the power available from the amp - and they're sealed, not ported.

 

Cheers

Mike

[almikel]

Apologies if this is teaching you to suck eggs, but if you were listening to music with 20dB average to peak ratio, then from your example:

 

Listening at an average level of 91dB - which I agree is quite loud - it takes 4W average, but 400W peak - already way beyond the capacity of your amp

Adding 12dB in the bottom end would require over 1000W to deal with 20dB peaks over the average - I reckon your KEF's are toast after less than 1 CD (tweeters included).

 

For only 10dB average to peak ratio, 4W average is 40 watts peak

add 12dB in the bottom end and it's 640W peak (again your KEF's are toast)

 

All the usual points apply that there's less energy down low etc etc, so you wouldn't necessarily need all that power - but it's pretty obvious that neither your amp or the KEFs are up to 12dB of boost.

Feel free to try but I wouldn't go higher than 3dB of PEQ and even then keep a very close eye on the excursion of the woofers, and apply a PEQ high pass at or above the port tuning.

 

cheers

Mike

[shkumar4963]

Thanks to everyone. Lots of good suggestions. To clarify, my intention was not to do this with my speakers but to better understand why or why not it could be done. At the first glance, the logic about 20 db dynamic range made sense to me but on further thinking it did not seem right. Assuming that the speakers are rated at 100wrms and are audiophile speakers, they must be capable of handling dynamic peaks of 20 db (if that is what we are assuming peaks to be) at 100 wrms power. That means while speakers can take only 100 watts rms power, the driver excursions or movements are capable of dynamic peaks of 20 db. In that case as long as the rms power stays within 100 watts, we need not worry about the 20 db dynamic peaks. Am i thinking about this incorrectly?

Also if RMS power is of concern then we just have to limit the overall volume to less than 91 db. so the question is what base boost (how many db at 50 hz and how many db at 32 hz] can be applied without damaging the speakers?

[Zaphod Beeblebrox]

BZZZTT!

Here is where you have it very wrong:

Domestic speakers (as opposed to some professional speakers, used in sound reinforcement) are NOT rated for continuous power (often incorrectly referred to as 'RMS power' - there is no such thing as 'RMS power' - 'continuous power' is the correct terminology). Domestic speakers are rated to be connected to an amplifier rated at XXX Watts continuous, WHILST PLAYING MUSIC. The peak to average ratio (20dB in the case we have been discussing, though it can be more) has already been taken into account by the speaker manufacturer. Very few (none, to my knowledge) domestic speakers can cope with operation under sine wave conditions (continuous power) at their rated power.

IOW: Your 100 Watt rated speakers are likely capable of the following continuous power figures (very roughly):

Bass: 25 Watts

Mids (if a mid is fitted): 7 ~ 10 Watts

HF: 5 Watts

Your theoretical questions are irrelevant in the real world, because domestic speakers cannot deal with the sorts of power levels we are discussing.