2. tech-talk
  3. 168962-6806

High-pass line filter to relieve main speakers from low frequency

Hi everybody
I recently purchased a subwoofer, KEF Kf92. It has a built in low-pass filter, 24 dB, that can be set from 40-140 Hz. They go with ATC SCM20sl. Their specs are: 80-20 kHz +/- 2 dB, 55-25 kHz : - 6 dB (free standing, which they are, actually: free hanging).
I wonder whether it would be beneficial to insert an high-pass filter before the power amp, consisting of a capacitor with a set point of 65 Hz. This filter might not have a huge impact because the frequency of the ATC SMC20sl rolls off quickly by itself below 80 Hz, apparently by about 12 dB/octave.
My thinking however is: the loudspeakers still receive the complete energy of the low bass from the amp. They might not be able to convert it into sound, but instead convert it into heat and distortion. So a filter will make the life of the amp and speaker easier, since at 33 Hz, only a quarter of the energy is produced.
Do you agree with me?
b_mueller
oldhvymec
5,101 posts
 
https://www.parts-express.com/FMOD-Crossover-Pair-100-Hz-High-Pass-266-274?gclid=CjwKCAjwmqKJBhAWEiw...

They make inline filters (low and high) from 20hz up to at least 100 hz and down, THEN 15khz and up. AT LEAST.. It's a pro application, but works very well..

No need to add anything but the filters you like PRE power amp..

It won't affect the passive OX in the speaker.. Just the signal it receives from the amp. No SUB involved with  steeper slopes like 24 or 48. The BOOM goes away and the timing (which is the problem) will become coherent. Reduced distortion, muddiness, bloated bass ALL goes away.

Room treatment, main and sub decoupling are the real eye openers too.

BUT limiting bass to the main is the BEST place to start, decoupling is right there though.. Room treatment is just the polish on a good, from ground up design..

Regards
speakermaster
738 posts
 
Any new sub will have a crossover filter in it for that purpose, which is to relieve your main speakers of bass duties, but if it does not, sure that is a great idea. It used to be that the satellites ran full range to augment he sub, but times have changed.
jgoldrick's avatar
jgoldrick
138 posts
 
I was curious about the same thing.  I decided to go this route. 
https://sound-au.com/project81.htm. 

I haven't built it yet, this fall or winter, but I have all the parts.  I figured it would be a nice cold weather project.
tomwipf's avatar
tomwipf
20 posts
 
It lools like you guys are looking for an active crossover. Per ocd hifi guy - check out Marchand. - https://www.marchandelec.com/electronic-crossovers.html

Many folk discourage. I have limited knowledge but I believe crossovers cause phase shift. If you have expensive time aligned drivers you may be doing more harm than good.
tomwipf's avatar
tomwipf
20 posts
 
Vandersteen also makes a high pass amp but I doubt you'll like the price.

https://www.vandersteen.com/products/m5-hpa
More to discover