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My high pass filter experiment and a couple of questions

Prior to this "experiment" I was running my Maranztz SA10 with balanced Kimber Silver Streak to my Cary SLP05 and from there I was using balanced Kimber Silver Streak to my Cary V12; from my SLP05 I was going out of the RCA outs with some old Monster Cable to my ancient M&K MX-100.

Back in ’95 I bought a M&K LP-15 passive high pass filter and I liked it with the gear I was then using, but as the gear got bigger and better and I also started using balanced interconnects I quit using it.

A few days ago I dug it out and I left the balanced connections from CDP to the pre the same, but from the pre I went with some Kimber PBJ RCA (because I don’t have any Silver Streak RCA that is long enough) from my pre into the high pass filter, and from the high pass I went with Kimber PBJ RCA to my amp; I hooked up the Monster Cable (that I had been going from the pre to the sub with) to the high pass filter and went to the sub with that.

Initially I kind of liked it, but tonight I wasn’t so sure. (It almost seems as if I am prone to INITIALLY like any change I make.)

I have a lot less gain and a lot more real extate available on the volume knob of my pre. That part I do like. I assume that is because I am going into my amp with RCA connection versus balanced and less voltage?

The high pass filter does have a treble control and a bass control. Initially I was reticent to use it any way except with both controls turned all the way to full. However, I did find that by playing with the treble control a smidge I could take the hard (bright) edge off of certain (not all) CDs. I left the bass control turned all the way to full because I am thinking it is supposed to do the same thing that the level control on the sub is doing, so why defeat that on the sub?

Another question is: since the LP-15 is theoretically supposed to roll the bass off at 85 Hz and the Revel M126Be’s I am now using are supposed to be trying to go down to 54 Hz, if those speakers are only being sent 85 Hz and above from the amp, this should make them an easier load to drive? I would think that their sensitivity doesn’t change, but now the impedance should not have to dip as low?

And still another question(?) does balanced from CPP to pre and RCA from pre to high pass and then to amp seem problematic? And I suppose I should consider upgrading the PBJ RCAs to Silver Streak RCAs?

 

 

 

 

immatthewj

Showing 4 responses by erik_squires

erik_squires
16,649 posts
 

A single capacitor can be an effective high pass filter.  Combined with port plugging makes it easier to raise the subwoofer Hz, something many who have resisted found irresistible after trying. :)

YMMV.

erik_squires
16,649 posts
 

only going by the posts I read here on A’gon, I was getting the impression that the going thing now-a-days was to augment full range speakers with a pair of subs?

 

While true for many, for the most part I find these approaches barely scratch the surface of what good subs can do.  Depends on the full range speaker.  Mid to small floor standers do much better being high passed IMHO. 

If your sub doesn't make your system sound glorious you are just gilding lilies.

erik_squires
16,649 posts
 

I remember that back then the conventional wisdom seemed to dictate that if one wanted to use a sub for low bass, the logical choice for speakers would be "book shelf’s" as there would be less overlap of bass frequencies. That was the way it was explained to me, anyway.

Yes, it’s still true although with the advent of DSP and advanced bass management available today vs. the early HT processors we can do more without getting into as much trouble.

My biggest surprise however still comes from how much better mid to small floor standers can sound with subs.  Even though they can be nominally rated to 40 Hz or so cutting off the bass and using a sub can be amazing.

erik_squires
16,649 posts
 

Oh man, the M&K high pass filter!! That brings me back. M&K was a major proponent of the satellite/subwoofer movement and I think their targets were more or less adopted by THX.  Sealed speaker that goes down to 80 Hz (the S-1B for instance) + a 2nd order high pass filter = close to a 4th order LR.  Together with 4th order low pass on the sub and you'd have pretty close to ideal phase matching.

Anyway, back to your questions. 

High passing an amp doesn't change the impedance it sees, but it does have to work a lot less.  The voltage swing (plus to negative) is greatly reduced when the bass is reduced.  In turn this means the amp doesn't produce as much voltage in the bass and therefore draws less current from the power supply.  All adds up to greater dynamic range and a stiffer power supply. 

One major tip for you is to try plugging your speakers.  This won't harm anything, but will raise the -3dB point probably to close to 80 Hz, and reduce the distortion.  I recommend virgin alpaca wool socks from a family.... OK, I'm kidding, anything clean and removable will work.  Don't attempt to fill the entire length of the port.  Just tightly wad something that fits the exit.  Let me know what you think of the results.

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