Quantify the Benefits of Bass Management

[guitarmadman85]

This might take someone that has experience with amplifier measurements to answer, but I'm curious is there is a way to quantify how much proper bass management affects the performance of the amplifiers in an AVR. How much more headroom is freed up when you crossover everything at 80 Hz? I know the unique variables in each system will yield different results, but as a general rule? Could you calculate how much additional headroom proper bass management is providing? Thanks!

 

[PENG]

This might take someone that has experience with amplifier measurements to answer, but I'm curious is there is a way to quantify how much proper bass management affects the performance of the amplifiers in an AVR. How much more headroom is freed up when you crossover everything at 80 Hz? I know the unique variables in each system will yield different results, but as a general rule? Could you calculate how much additional headroom proper bass management is providing? Thanks!

It depends so much on the contents that it is not possible to quantify without knowing the specific content. It may be reasonable to generalize using a wide range (such as almost 0 to 30%) for each kind of music genre and types of movies. Even then, it would still be very dependent on the speakers. Obviously a speaker that has impedance troughs and/or poor phase angles in the below 80 Hz range would benefit more than one that has benign impedance and phase angles.

 

[KEW]

If you are playing Dubstep, a sub increases headroom by umpteenkazillion!
If you are watching Mister Rogers sing, save energy by unplugging the sub!

Obviously, my answer is facetious, but it does reflect the "it depends" nature of a proper response to your question!

 

[ski2xblack]

One could feed a purely resistive load, measure 20-20k vs. 80-20k and compare. Throw in music and reactive loads like real speakers and it gets more complex, but the results should be similar.

Why do you need to know rhis? It's a positive amount, but not appreciable. Well, maybe for the dubstep, but even in that case it's still insignificant. Logarithmic relationship between power and percieved spl, remember. The increase in headroom is just not much. If you have an avr that you regularly clip, employing bass management probably won't save you, but a considerably more powerful amp would.

 

[TLS Guy]

We get asked this question quite often.

The first thing to understand is that there is not a lot of musical information in the sub bass range 20 Hz to 50 Hz, what is often called the last octave.

Most of music is well outside sub range. A pipe organ is an exception in the bass department, but even then a pipe organ has far more mid and HF energy than bass. In fact if you are not careful they can be effective as tweeter destroyers.

Now the other issue is that having the last octave does increase the realism of music if properly reproduced. Badly reproduced or integrated it does the exact opposite. Also having the last octave helps in reproducing the ambiance of the recording space.

Now the other issue is that a speaker does not reproduce below its F3 and if it is a ported enclosure then you get useless and potentially destructive cone excursion.

Now the next issue is the impedance curve of speakers. Most in use today I would guess are ported. So you get a saddle impedance curve with the null at the tuning frequency.

Here is the impedance curves of some of my speakers.

You will note that in the sub bass range the impedance is high limiting current demands.

So you can see with the smaller amount of musical content and typical impedance curves, a sub does little to offload a power amp. It does however off load the bass drivers of the other speakers.

I suppose if you are a dub step nut, then things cold be different. Explosions of movies are usually short lived and high power demands of most movies are very episodic. Movies are mainly dialog and background music.

The problem I find is though that integrating subs is not that easy. The speakers crossed over to subs is a crossover. Yet we have a one size fits all. Most speakers are not really designed, and certainly not optimized, for the 12 db slope high pass to the speakers and 24 db low pass to the sub. So really for optimal performance speakers and sub need to be designed as a unit, like any other speaker system. So that is why Eq and a lot of time and patience is required and results vary.