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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
immatthewj OP
2,030 posts
 

@gdaddy1 , that's basically the route I went.  The high pass made my system more dynamic with my first preamp and a lower powered entry level tube amp, but as I moved up in equipment I remember a dealer referring to using a high pass as "putting another crappy box" in the signal path (only he didn't say 'crappy').  Also, I started using balanced intercoonects, so that alone ruled out using the high pass.

But just recently I got the itch/urge to experiment without speding any money.  I had previously been running my switchable amp in the 50 wpc triode more so a while ago I switched to 100 wpc ultralinear and kind of liked the change.  Then I got to thinking that since I already owned a high pass I haven't used since the '90s, why not hook that back up again and see what I think.  If more power to the speakers was a positive (the ultralinear circuit), maybe only feeding my amp 85 Hz and above would work a long the same lines, was my logic

And that's where I am right now

grislybutter
3,077 posts
 

prone to INITIALLY like any change I make

There. It seems that if you would change things all the time, you would like them 100% of the time.

mitch2
3,997 posts
 

I believe the effectiveness of using a high-pass filter depends on the main speakers, the amplification, and the quality of the high-pass filter. If you are using good subwoofers (at least two) then a high-pass filter should theoretically improve linearity and reduce distortion by relieving your amplifier from the need to amplify the more demanding low frequency signals, and by relieving your main speakers from the need to try and reproduce the lowest frequencies. However, in the case of my acoustic suspension speakers that roll off bass at around 40Hz and that have the ability to handle high power and deep bass, having the additional high-pass circuitry in line and affecting all of the upper frequencies was not sonically worth the trade-off. As the manufacturer of my speakers and subs recommended, my system sounded better running the main speakers full-out (i.e., without the HP filter) and rolling in the two subs at a relatively low frequency of around 45Hz. I believe it is also helpful that my amplifiers have more than ample power (650 wpc into 8 ohms) to drive the low bass loads.

erik_squires
16,112 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.

immatthewj OP
2,030 posts
 

@grislybutter , I believe you are on to something with that.

@mitch2 , the high pass filter probably isn't all that good, and the subwoofer is ancient and probably obsolete.  Low bass is probably the weak link in my chain at this point in my life.

After my session this afternoon, I do not think that the high pass setup is the answer I am looking for.

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