My high pass filter experiment and a couple of questions

If you can run Balanced out to the poweramp and RCAs to the Sub simultaneously, why not try going back to balanced between the pre and power amp whilst continuing to use the M&K high pass.

A couple of options for balanced high pass filters. Harrison Labs Parametric Patch Board or Marchand. I am using the Harrison Labs units with 50 Hz filters.

If you can run Balanced out to the poweramp and RCAs to the Sub simultaneously, why not try going back to balanced between the pre and power amp whilst continuing to use the M&K high pass.

@theophile , to put the high pass in between the pre and the amp and roll off the signal to the amp at 85 Hz the only way I can do that is by connecting to and from the high pass with RCAs.

However, I think I understand what you are saying:  connect the pre to the amp with balanced, and connect the high pass in between the pre and the sub with RCAs.  But that doesn't accomplish my goal, which is to isolate the amp from signal below 85 Hz.

I went down this 'High pass' road once. In the begining it made perfect sense. Then Then I started thinking about how my precious audio signal was being run through all this additional wiring and electronics molesting the signal along the way. Affecting the phase? Losing dynamics in the lower register?  I began to question this direction. Did it really sound better after all this? Was I gaining anything or just adding complexity? 

I pulled it all out and never went back. Much prefer a clean, minmalist signal route. Less is more.

@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

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.

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.

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.

@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.

@erik_squires , yes! My M&K sub and M&K high pass do, in fact, date back to the days of Dolby Prologic! (They are both ancient and obsolete.) 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. Back in those days, ’94 & ’95, M&K had this extremely helpful and pleasant and patient gentleman working for them named Doug Osborne. He must have spent hours taking my phone calls and answering my endless stream of questions. I actually did buy the high pass filter on his recommendation and I did like it in the system I was using it with, which was a B&K digital HT pre going into a Cary SLA 70 which started driving a pair of NHT "book shelf" speakers and then graduated to driving a pair of B&W 805 Matrixes. As I typed, I liked it a lot in that set up--it made for a much more dynamic presentation and I was quite impressed with the presentation.

As I typed in my OP, as my gear got bigger and better I moved away from it, and after this afternoon’s session, I don’t think going back was the answer I am looking for. The presentation seems slightly more "veiled" to me with the high pass installed again. Maybe the bass is a bit tighter, but as far as dynamics, I think the presentation may be less dynamic with the high pass than it was without it.

Thanks for the explanation of the dynamics involved (which would explain why I liked it with the first system I had it in). As far as plugging the speakers, the Revels did come with foam plugs, and so far, since recently aquiring the Revels, I have had them out for a while, put them in a for a while, took them back out for a while, and then put them back in shortly after starting my high pass "experiment."

I think what I am going to do is to take the high pass out of the chain, but continue to rum that part of the system (pre to amp) with the RCAs (and see how I feel about that, because I enjoy the less gain aspect) and start out leaving the plugs in. And then I will go from there.

Anyway, Eric, thanks for your perspective on this, and good to see you around again.

to try to be serious, I think you have a trade-off, clarity and focus vs full range sound with more bass maybe more distortion too. I don't know if you want to stick with it or go back? Can we ever? Maybe it's a step up in your journey to another component and/or combination. 

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.

@grislybutter , actually, I think your first post about changing things all the time to find "happiness" was a serious concept. As far as the trade off going on with the highpass installed, I don’t think it’s worth it. What I think is that I need a new subwoofer. Ha ha, but seriously, that’s what I think. Seriously. However, although that may probably happen some day, not any day real soon. I now wish I would have bought some smallish sized three way floor standers, but the price was right on what I did buy, and floor standers in a small room, even small ones, might be problematic if they made too MUCH bass for that small room. At least with a sub I have the option to dial it down or up for whatever source material I am using.

@erik_squires

Yes, it’s still true

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? (Which, back in the day that I bought my sub, I thought was considered a no-no.) I guess the folks running subs with full range floor standers these days are all pretty much utilizing some form of EQ or DSP?

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.

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

@erik_squires , there have been sessions with certain source materials that I honestly did feel my system sounded glorious, but I would also add that it was not because of my sub.  I truly believe that my sub is the weak link in my system.

Most who’d implement a high-pass filter over the main speakers would do so over an existing, passively configured speaker setup (i.e.: with a build-in crossover "seen" by the amp on its output side), meaning an extra layer of signal processing/filter of some kind is added to cut off the main speakers below a given frequency in the bass area.

If a DSP is suggested for this purpose it runs contrary to the desire of quite a few audiophiles to avoid added (or any) conversion steps in the signal chain (not least A/D conversion with an analogue input only, which would then be followed by the necessary D/A conversion step for the signal sent to the analogue input on the amp - unless it’s a digital variety), and so an analogue HP-filter may be preferred here. Purists on the other hand would rather avoid any kind of added HP-filter.

Previously I used my current DSP/digital crossover (Xilica) over my passively configured main speakers to cut them off below some 80Hz to be augmented with a pair of subs below, and being it’s a high quality DSP (even with A/D to D/A conversion steps) the result was great; I could detect no lack of transparency, resolution, change in tonality or other with the inclusion of the DSP, and being able to experiment with and find the sonically most desirable cut-off frequency to the subs (with both low and high-pass filtration) proved very worthwhile, also in relieving both my previous all-horn speakers and Class-A amplifier in the bass area.

Which is to say: with a high quality and transparent DSP/HP filtration device any remaining slight influence the filter may introduce by its mere existence in the chain as an added element (and thus, strictly speaking, can’t be claimed to be fully transparent in an isolated sense) is likely to be alleviated by the positive outcome it creates with relieving bass to amp and speakers, in addition to providing for the opportunity to tweak more effectively with the crossover range to the subs.

If on the other hand you’d run a fully active speaker setup, which I know you aren’t, the digital crossover/DSP or electronic XO(i.e.: non-DSP) would act as the only filtration means in the chain (remember: the passive XO is a filtration/equalizing device as well, and a sonically detrimental one at that) that could also apply a high-pass filter over the main speakers. This way the crossover you’re already using as a wholly necessary component (just like the passive XO) can simply be asked to perform another task, and that way you’re more effectively approaching your speaker setup + subs as a single speaker system per channel - they’re merely divided into separate boxes. This also means that the separate amps to each driver section work independently of each other; whatever goes on in each of these amps and corresponding driver sections won’t affect the other, which is a further bonus - and hardly an insignificant one.

It seems that many who attempts a high-pass solution over their passively configured main speakers for the use with subs don’t approach it all-out enough, be that both with regard to the added filter component used as well as and perhaps not least where the implementation goes; sometimes such a project is indeed doomed to begin with. Therefore, give it a good shot before coming to a conclusion.

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.

Hi Erik, I am curious about your single capacitor solution.

If I bi-wire my speaker connections, can I wire a single capacitor in line with the LF speaker wires to limit the low frequency signal going to the woofers? 

How exactly would you wire that capacitor, to the positive terminal of the LF binding posts, only?  Would that have any effect on the high frequencies?

Since that capacitor would come after the amplifier, would that solution benefit both the speaker (which would not need to reproduce the very lowest bass) as well as the amplifier (since the speaker wouldn't be drawing current to power the lowest frequencies)?   

How would I figure out the capacitor parameters to use for a certain high pass value, like 40Hz?

If it were this easy, why aren't the speaker manufacturers recommending this solution and why do people purchase more expensive solutions as provided by Vandersteen or Marchand?  FWIW, I owned the XM446 fully balanced high pass filter, which was in-line prior to the amplifier thus affected the entire signal.

BTW, I am not challenging your comment, but sincerely want to understand.  Also, my acoustic suspension speakers do not have ports. 

Thanks for any further clarification/explanation.

I've been engaged in that experiment for a few months now. I bought a balanced HPF from Marchand. It filters below 80hz and is very effective at creating space for the sub to fill. I was quite pleased with the low end. 

However, I had issues in other areas that I couldn't solve with room treatments so I just purchased a high quality graphic eq. I decided to use that below 80 as well, and was able to dial it in nicely. So now, the sub is relegated to below 40 where my speakers fall off a cliff. 

If you're interested, I may sell the Marchand HPF.