Phono Stage upgrade to complement Dohmann Helix One Mk 2

Velodyne DD+, 15 or 18 inches.

ML probably make a good woofer too.

If you are going to draw conclusions by reading websites, you’re likely to do nothing. It is impossible to conceive that a high pass filter would have zero (measurable) effect on the upper frequencies, mostly in terms of phase shift, not distortion so much, unless you use a bad electronic crossover. The question is can you hear it and if you hear it do you like it? The reason for using 6db/octave (passive with just a capacitor or active using an electronic crossover) is to do as little damage as possible to frequencies above the crossover point, in terms of phase shift. If you have questions about the ML subwoofers, it would be best to either look for a good review on line or to call ML and ask. I don’t know how I got into the role of a person urging you to try a subwoofer. In the Velodyne website and elsewhere at sites selling Velodyne, there are usually good photos of the back of the subwoof showing connectivity. I looked at a few last night. For me it was easy to see there are inputs for the preamplifier output, outputs for high frequencies to go to a main amplifier, and of course the low frequencies go to the built in amplifier that drives the woofer. There are many other choices of connectivity also offered; one would not be using every single input and output in any single installation. If you buy a Velodyne, there will be a book explaining in great detail how to install and use. Never fear that.  Better yet, in your case I recommend you get a local dealer to do the install and explain it to you along the way.

Correction: I finally found a diagram of the back of the Velodyne subwoofers under quick start guide on their website. . But it’s a very poor diagram, and doesn’t explain anything about the HPF, LPF, etc. It looks like their target is the home theater crowd. Martin Logan website is more informative, actually has good diagrams, and mentions the difficulty of incorporating subwoofers with ESL, but they only appear to have LPF, which would need an external HPF, etc, which gets into the issue of SQ.

@holmz 

I was just reading multiple reviews about various HPF and they all say that there is a noticeable affect on SQ.  But I suppose it's worth a trial.  The current problem is finding the best ones to initiate this trial with:. Vandersteen, Martin Logan, or Velodyne?  (I suppose Magico would be an option if it weren't a trial, but a definite move.)

@rauliruegas @lewm

Which Velodyne subwoofers would you recommend for best match and highest quality? What about Martin Logan subwoofers, or other brands?  (Velodyne has no photos of the back of their subwoofers and no diagram of connections on their website or downloads; the only Velodyne video on YouTube is 20 years old.  It seems like they're trying to hide something!)

Thanks.

I don't agree with Holmz in some cases, but for me to debate Holmz here would only confuse you further.

Or maybe it would not?

Suffice to say, as I said before, a properly integrated subwoofer will not give you the sensation that the cello is jumping from main speaker to subwoofer and back again.  On that score, Holmz and I agree.

And we both are advocating use of a high pass filter between the preamp and the amp. I just buy mine, and others use a capacitor.

On the other hand, I am not a fan of digital filtering or digital shaping of the response.

People with DACS and streamer, and CD players are alreadily heaving inverted in digital tech…

It is easier to tolerate a DSP on the sub chain side.
And the HPF solutions we are both talking about are on the main L/R channel side,.

I am still trying to figure out the difference other than manufacturers sticker.
It looks like you fancy the Velodyn and I like the Vansdersteen.

Unfortunately, the more I read about HPF, the less inclined I am to use them: everything that I’ve read so far indicates that their use does impact SQ.

Well is there a link to that?
And is it a digital or analogue HPF?

Additionally, here’s a paragraph about higher order HPF influencing signal moreso than lower order HPF (but it is just the internet, which could be wrong):

There is slower transcient response, but if you have a speaker with a crossover, then I am not sure one can be a purist.

Although there is no limit to the order of a filter that can be formed, as the order of the filter increases so to does its size. Also, its accuracy declines, that is the difference between the actual stop band response and the theoretical stop band response also increases.

I think you might be talking about speaker level XOs that have the inductors.

The ones with capacitors are not large, as they are RCA level. The big ones are the size of a couple packs-o-smokes.

Yes, and that has been written here above over the past several days.  If you buy a modern Velodyne sub, you would need nothing else.  It comes with a built in two way crossover and an amplifier dedicated to driving its subwoofer.  It also comes with a microphone and the necessary circuitry to set up the subwoofer for best flattest response.  I was wondering why you seemed to feel that introducing a subwoofer also meant you would have to give up your present preamplifier (to go digital for some reason) and even your main speakers.  Not so.

@rauliruegas 

Yes, you would be correct that I have no experience with subwoofers.  Does the Velodyne insert into the system between the pre amplifier and amplifier, with both a LPF for it's own amplifier and an internal HPF that then is sent to the monoblock amplifiers?

@drbond : "" I was thinking that the crossover should be below the lowest cello note, which is 44 Hz, as I wouldn’t want the cello to sound like it’s jumping around. ""

As lewm posted and this tstaement confirmed you are a truly novice on sub’s integration to a room/system. That " jumping around " never happens with not the " ultimate " subs/speakers but with any just decent integration.

As lewm posted almost all sub’s in the market comes with lo/high pass filters so you don’t need to add other part but IC cables and that’s it.

Don’t ask your self, as you did it, that will be a " degradation " before your sub’s integration for that trial/tests because the rewards here compensates any degradation you could think. Do it a favor: " don’t think or imagine ", you was who posted to make that trial/test so and with all respect just do it, up to you but can’t pre-judge before listen it. Again, sub’s are not like a change of amps or a cartridges or tonearms, is totally new for you: how can or could you pre-judge with out listen it in your room/system?.

Velodyne is only an option to make that " trial " and if you don’t like just return and put on sale the sub’s. No, the crossover frequency must be not at " 44hz " but at least at 80hz to take advantage of all sub’s/speakers/amps rewards.

Btw, any top room/system ( like yours. ) with passive speakers receives several rewards with the sub's integration.

R.

@rsf507

Yes, to a casual observer, you may wonder why we are talking about subwoofers on a thread that started with phono stages. Well, the phono stage question was resolved rather quickly and emphatically in the first few pages of the thread, with a brief foray into amplifiers. However, three of the five of the regular contributors to this thread all have the same ESL speakers, so that’s probably the main reason I thought it was best to continue any detailed discussion about my sound system on this thread, as opposed to starting another one in the speakers section. Additionally, there are many other factors that one can consider: I think that individuals that listen to vinyl have a sound in common that they appreciate; additionally, at the level of system we’re talking about, I would probably have to sort through a hundred posts about average equipment; whereas, here, most realize that we are discussing very high end equipment.

Thanks.

There are pros and cons to any decision. Yes, take your time to find your own set of goals and the best methods for achieving them. It’s more fun that way, besides.

@rsf507 talking about $60,000 Phono stages is not that relevant to most people either

@mijostyn agree but it's a more interesting read than all this talk about sub integration. At least start a separate thread on subs. That was my point.

Unfortunately, the more I read about HPF, the less inclined I am to use them: everything that I’ve read so far indicates that their use does impact SQ.

Additionally, here’s a paragraph about higher order HPF influencing signal moreso than lower order HPF (but it is just the internet, which could be wrong):

Although there is no limit to the order of a filter that can be formed, as the order of the filter increases so to does its size. Also, its accuracy declines, that is the difference between the actual stop band response and the theoretical stop band response also increases.

Learning about subwoofers is an exercise! I’m not sure whether I should proceed in this direction, given the components in my system. . . although, it would be interesting to compare any differences in SQ with a properly installed digital HPF with subwoofer, which replaces my pre-amplifier / amp / ESL system currently. But that might be a project for another time. . .

mijostyn

Your opinion is the knee jerk reaction of a traditionalist. Your assumptions are patently false. You are entitled to stay where you are. There are people who prefer being dinosaurs and that is fine ...

Why so angry? Why are you so triggered by those whose opinions differ from yours? Why do you feel others need your permission to disagree?

@rsf507 talking about $60,000 Phono stages is not that relevant to most people either. 

@rauliruegas , since I design and build my own subwoofers and analyze the results I know a lot more about it than most audiophiles. Putting a 1st order high pass filter on the amplifier input is a last resort. 4th order is more like it. You are much better off with a digital 4th order high pass filter than an analog one.

drbond, This thread can go on and on with different ones of us giving you different advice. To avoid further confusion, I suggest you read up on the options by searching on line.  Terms you need to understand are "active crossover", "passive crossover", and something about how slope of the high and low pass filters comes into play. I don't agree with Holmz in some cases, but for me to debate Holmz here would only confuse you further. Suffice to say, as I said before, a properly integrated subwoofer will not give you the sensation that the cello is jumping from main speaker to subwoofer and back again.  On that score, Holmz and I agree. On the other hand, I am not a fan of digital filtering or digital shaping of the response.

 

Hmmm…this subwoofer project is looking complicated:

often it does…
Many do it digitally, and that is a lot easier some ways.
However if the main analogue chain is nice, then we can complicate it with an analogue approach, which is in fact a bit simpler.
(But there are many ways to skin a cat)

it seems like an ideal approach would be an in line high pass filter after my pre-amplifier, but this would have to be an analog filter, correct?

That is one way, and usually it is the one that has the minimum detriment to the signal chain. And even with this HPF, one can use some DSP on the sub to flatten the response a bit.

(I can see myself reacting to a cello that sounds like it’s in one place for the higher notes, and another for the lower strings/notes…)

A cello sounds like it is in the same place as the higher notes of the instruments harmonics locate the cello, and low notes reinforce the fundamental tone.

When it is done right then it is not apparent that the sub is even on.
But if one turns the sub off, then it is apparent.

And it often sounds best when it is turned up to the point that it is apparent and backed off to the point where it almost seems like it is not contributing.

Set up well it is like PFM (Pure Magic).

…or replace my pre-amplifier, which I really enjoy listening to, with a digital pre amplifier that has filters built into it…which I am averse to do…

It is ^here^ where the in-line HPF is an elegant solution.
It sound great now, you just a bit more of low notes, and remove having to force the main speakers from trying too hard to play those low notes.

With the HPF, one just tapers off a major portion of the power to the main speakers, as the lion’s share of power is used for pushing air in the low notes. And then the sub takes that over and tapers off the power as the notes enter back into the main speakers in a smooth fashion.

And then all the IMD and Doppler distortion of the panels having to wave back-n-forth as the high note are also coming off of it… becomes reduced as most of that waving gets shed to the sub.

Doing this at a knee of 100Hz is not uncommon with a 1st order slope.
Some people go high with higher slopes.
And if the sub resonates or has harmonic, or noises, that locate it in the room, they they might cross it over lower.

If one fancies the idea biasing the dielectics, then the HPF get some extra stuff in it, but it behaves like a single capacitor.

@lewm 

Thanks for the clarification.  My favorite pieces involve the cello or cello and piano.  (Yes, Bach, but also Beethoven and Brahms.)  Consequently, I was thinking that the crossover should be below the lowest cello note, which is 44 Hz, as I wouldn't want the cello to sound like it's jumping around. 

Drbond, the filters built into most subwoofer electronics are active and analog. Unless explicitly stated, the filters in an outboard electronic crossover are analog.The only passive filter mentioned so far is the idea of using a capacitor in series with the main amplifier input to effect a simple 6db high pass filter. Everything else is active . If you want digital filtering I know nothing about what’s available, and I personally wouldn’t go in that direction.

Dear @drbond  : Any electronic device is active with it's power supply.

If you don't want to go direct to the amplifiers then you need that electronic device as this one:

https://www.jlaudio.com/products/cr-1-home-audio-subwoofer-crossovers-96020

R.

@lewm

Is there such a thing as an active analog high pass filter, or are all analog high pass filters passive?
Thanks.

"So, with the Velodyne Digital Drive subwoofer, the entire line goes through the subwoofer from the pre-amplifier? And the Velodyne has both a high pass and low pass filter, which the high pass filter line then goes to an output line into the amplifier, and the low pass filter signal is delivered to the subwoofer?"

So far as I can tell from reading on the internet, the answer is "yes".  The electronics in a DD+ Velodyne can do it all for you. But you can opt to drive the main speakers direct, using an in line capacitor to effect a passive high pass filter (or any other way you like to effect a high pass filter).  One or the other, not both.  I personally would NOT go digital for the high pass filter. There is just absolutely no need for it. Mijostyn would disagree.

@lewm

So, with the Velodyne Digital Drive subwoofer, the entire line goes through the subwoofer from the pre-amplifier? And the Velodyne has both a high pass and low pass filter, which the high pass filter line then goes to an output line into the amplifier, and the low pass filter signal is delivered to the subwoofer?  Or, would I still have a direct line from the pre-amplifier to the amplifier that goes through a high pass filter, which would either be analog, or, if digital, need an ADC and DAC?

(And the amplifiers are the Ypsilon Hyperion (input impedance 22k Ohm). I previously had Atma-Sphere MA-2, which were also very good.)

drbond, There is no need to overthink this or to overspend, either.  There is absolutely no need to change your preamplifier, either.  The very simplest thing to do is to buy a high quality Velodyne or other reputable brand subwoofer.  These typically have built in to their electronics a pretty good electronic crossover which allows you to choose cut-off frequency for the high and low pass filters, and slope for high and low filters, as well as a level control so you can balance the two.  This is done electronically using a microphone and computer programming that is built into the subwoof.  It's quite amazing where the technology now stands. For you as a novice, this is the path I would recommend, if you are willing to spend the bucks on a very good subwoofer.  If on the other hand you want to use a passive high pass filter with a 6db slope and use only the low pass filter built into your new subwoof, I can calculate the value of capacitance you need to effect a crossover at a particular frequency of your choosing, if you supply the input impedance of your amplifier.  Since you have an Atma amplifier (if memory serves), I already know the impedance is likely to be 100K for SE mode and 200K ohms for balanced. Typically you would use a cut off below 100Hz.  At those frequencies (and lower is better), bass is non-directional. If you're crossing over below the primary tones of the instrument, then you would have absolutely no sense that the musical line is jumping from the main driver to the subwoof.  I wonder how Raul and Mijo feel about the need to use a stereo pair of subwoofs vs a single subwoof.  My bias would be to use a pair of modest size (e.g., 12 inches) or one of large size (15-18 inches).  The lower you crossover, the less would be the need for a stereo pair, by my own estimation.  You could crossover at 60Hz with our speakers or maybe 80Hz.

@rauliruegas 

By complicated, I was referring to the act of installing an in-line digital high pass filter after the pre-amplifier, which would require an ADC and then a DAC before the amplfiier. . . and not sure how it would then affect the SQ, which is superb presently through the Ypsilon PST-100 Mk2 SE pre-amplifier.  

Just my thoughts but would like to see this thread titled "Phono Stage upgrade to complement Dohmann Helix One Mk 2" get back on track. Talking about subs is not that relevant to many. 

Dear @drbond : Your amps is a design with tubes at the input well it’s down there ( a good technician that knows where in that stage and calculation for the cap is need it. ) where the high-pass could goes. No you don’t need digital .

If after your tests you do not like it you always can return as the begin.

"" this subwoofer project is looking complicated.. ""

No, maybe some of our posts made that " looks " complicated but it’s not at the level you are thinking and at the end is a room/system tests .

After those tests you will know where to go. Btw, for your subs test it’s not need it that you go with the 18" Velodyne model, you can make that job with the 15" woofer model.

R.

Dear @mijostyn : " and here you are asking me to preach..."

Not really that you took my post to preach is only because you like to show you about. Fine with me and if you read in reality you only repeat what other posts already touch it  ! ! 

My post was to say that you are not the only audiophile with good knowledge and experiences on sub’s/ESL. That’s it.

R.

Hmmm…this subwoofer project is looking complicated:

it seems like an ideal approach would be an in line high pass filter after my pre-amplifier, but this would have to be an analog filter, correct?

(I can see myself reacting to a cello that sounds like it’s in one place for the higher notes, and another for the lower strings/notes…)

…or replace my pre-amplifier, which I really enjoy listening to, with a digital pre amplifier that has filters built into it…which I am averse to do…

I truly did wonder why you thought Raul’s quote was humorous. Along the way, I could not resist the anatomical pun.

@lewm I liked the pun. So you get a point.
(But let’s try and resist using digital in an anatomical pun please.)

The two best and most expensive electronic crossovers I know about are the Pass XVR1 and the Bryston.

I assume you mean “electronic” as in solder and parts?

The DEXQ is more like a MiniDSP, Lyngdorf or Trinov, but for more a 2-channel.
It is likely overkill, but subs, and bi-wire binding posts, then it has some allure that  could allow it to be used as a 3 way XO.
It is a digital solution and the pricing reflects it as being digital.

@rauliruegas , Raul, I have been using subwoofers with ESLs since 1979. The system then was Acoustat Model Xs, with two RH Labs subwoofers, a Dahlquist crossover and Kenwood LO 7M amps. The model Xs were soon replaced by Monitor 4s which were planted on top of the RH Labs subs. Since then I have been through every permutation involving ESLs you can think of including Velodyns. Lew does not like it when I preach and here you are asking me to preach.

Subwoofer integration was a frustrating process of trial and error up until the introduction of digital signal processing by the TacT corporation which has now morphed into Lyngdorf.  The first step is to determine what kind of main speaker you have and how it functions at the expected crossover point, point or line source. The subwoofer array has to match this radiation pattern. Subwoofers are always more efficient against walls and in corners. Rule #1 is never use just one subwoofer, two is the minimum. 

The trick is to use the highest crossover point possible without allowing the sub to creep into the midrange. This requires slopes higher than what is practical for analog crossovers. I use 100 Hz at 48 dB/oct. The more bass you take away from an ESL the better it performs. It is critical for time and phase to match the main speakers. This is a breeze to do digitally and virtually impossible in analog fashion.

There are many great subwoofer drivers out there now. The real problem is the enclosure. Any subwoofer driver producing 20 Hz at 90 dB is going to make the enclosure shake at 20 Hz. Any shaking of the enclosure is distortion. To counteract this smart designers place identical drivers at opposite ends of the enclosure running in phase so that their Newtonian forces cancel out. This is called balanced force design. Magico, Martin Logan, Kef and MS tool make balanced force subwoofers. Increasing the mass of the enclosure does not stop it from shaking. The next problem is making the enclosure entirely non resonant at subwoofer operating frequencies which means very stiff walls made from critically damped materials. Magico uses aluminum, Kef uses composite and I am not sure what ML uses, probably MDF. I use 1.5 inch thick maple plywood. Plywood is stiffer than MDF. It is more expensive and harder to work with. Keeping the enclosure as small as possible helps in this regard. Play a loud bass heavy song and put your hand on the sub enclosure, any shaking or vibration you feel is distortion. You should feel none. 

The low pass filters most manufacturers use in their subwoofers are little more than a joke. To tune a system correctly you need a two way crossover with crossover points and slopes adjustable from the listening position. You should not be able to sonically separate or locate subwoofers.  They should seem invisible except for the added bass they provide. The most significant feature is the reduction of distortion in the main speakers. With two or three way speakers this reduction occurs only in the range handled by the woofer but in full range ESLs it applies to the entire frequency range and is even more obvious even if Lew disagrees. 

Finally, smaller drivers are not faster. They have to move farther and faster to produce the same note at the same volume creating more distortion along the way. Larger drivers produce bass with less distortion. You can produce the same effect with multiple smaller drivers. It is a matter of how much surface area you have in operation. To produce 18 Hz with authority in a 15 X 25 foot room with reasonably low distortion you need at least two 12" or four 10" drivers. There is a limit in terms

of size. Larger heavier cones are more difficult to control and can wobble creating distortion. I have seen strobe light videos displaying this. Where the limit is I have no idea. I think in the home situation drivers larger than 15" are unnecessary, just use multiples if you need more. The system I am building now uses eight 12" drivers, two in each enclosure.  

Room control is a nice addition for subwoofers but it does not excuse poor acoustic management of the room. Room control (really speaker control) can stress amps and drivers otherwise and cause more harm than good. This is another reason for using multiple subwoofers. Multiple subwoofers in different locations evens out the bass response within the room. 

Bedtime

No problemo either way.

Are you addressing me?

No @lewm .
It appeared that @Raul was using your quote, in a way that was oblique and directed at me.

Dear @mijostyn  :  "  never achieve state of the art performance out of your system without subwoofers..."

 I agree.

"     without a bit of first hand knowledge.... 

Disagree.  Some of us have that first hand experiences and in my case with different kind of main speakers including ESL and between the ESL Soundlab ones and all those experiences in different systems and always in different rooms.

The only coincidence between your room/system and the drbond one is the ESL system link. With all respect:  are you trying to say that you are the " God/Emperor " of sub/ESL?

drbond wants to " test " subs  and through that " tests " he will achieve the necessary firt hand experiences with to decides about.

With subs the integration to a room/system always is different in almost all, there are no rules and if you have proved and measured rules then this is a good time to share to the Agon community. Don't you think?

Subs integration is not like a change of amplifiers or phono stage or tonearm but something that each owner must have to live. Learning starts reading as he already is doing.

R.

Mijo, my journey to not using a subwoofer with my full range ESLs runs through years of experimenting with subwoofers to augment other ESLs, like KLH9s, Quads, and Martin Logan CLSs, all of which really do need woofer supplementation. I built my huge Transmission Line cabinets that now supplement the Beveridge speakers back in the 70s on my nights off call when I was an intern.I’m certainly not as good a cabinet maker as you, but i do have past experience with subwoofers. That’s how I developed my distaste for electronic crossovers. (I’m sure modern ones are better.)

Are you addressing me?

lewm : " I truly did wonder why you thought Raul’s quote was humorous. " . Easy, because he did not think in that way before. Seems to me that is his way of audio life kind of think because he posted twice something with no sense in reference to what I posted about sub’s, he said twice: " you was not the first person to said that " .

But where in hell posted I that " I was the first audiophile to said that " ?

You might be right… I agree that it seemed to you that it had no bearing on the topic,
Yet here we are talking about whether to use a capacitor and then how to hook the sub up, and it is a week later and you still claim that that post is not addressing some of the OP’s question on subs.

You choose to put in a capacitor, and others insert that HPF that I linked to… and then they use a powered subwoofer that is designed as a system.

At some point it is going to click as to it being a system and why I posted it.

Similarly that REL kind of clicked with me as being a bit incomplete in that is it not using the HPF between the preamp and the amp(s)… and the sub has no way to account for a dependable slope or crossover knee… so it is either too much bass or need a lot of TLC to make it blend.

@drbond, Are you dizzy yet? What you have here is a whole bunch of people making assumptions without a bit of first hand knowledge. The horse's mouth is right here. I have been using subwoofers with ESLs since 1979 and have been through every permutation you can imagine. I can promise you this, regardless of anything else you do you will never achieve state of the art performance out of your system without subwoofers. I can help you avoid all the mistakes I made over the years and get you set up. This is a thread about phono stages. If you want to talk about it message me. 

Dear @drbond : lewm posted " You want a steep slope on the low pass filter going to the subwoof, because you don’t want the subwoof contributing to midrange ..."

Normaly subs comes with 12db/18db filter shape and the users always can change the low-pass frequency that at the end the sub internal dsp will tell us and through listening tests we can confirm is rigth or we can play with the sub crossover set-up characteristics till we are satisfied with. The Velodyne low-pass shape by default is 24db ( steep as lew posted. ) but selectable and its high-pass shape is 6db. My old Velodyne low-pass filter shape " initial 12db, 48db ultimate ", is what I read in its manufacturer specs.

In the other side, adding sub’s in any room/system means too that maybe we can need some kind of different room treatment maybe not or we can find out that we need to move a little the main speaker positions.

Subwoofers per se is not a " key on hand " solution to open the " door ", we always need some kind of work for the room/system good integration.

R.

Dear @drbond : You already know that in the audio world always exist trade-offs when we want to make some room/system changes, nothing is perfect so don’t try to look for because just does not exist.

You need only a high pass because the low pass is made it by the sub’s. Now you can have that high pass with and active external crossover or you can do it at the input of your amps and for me this is the best high-pass trade-off because you add almost nothing: no added electronics, cables and input/output connectors.

The signal that goes to the amps from the CH goes directly or through the external high-pass filter and from your CH goes too directly to the subs. Btw, usually the high-pass filter setting up is in the 80hz-100 hz and you do not needs that the external/internal high-pass has additional gain because the high-pass gain is handled by the preamp. The gain of the low-pass by the sub's.

That’s it.

R.

@lewm : " I truly did wonder why you thought Raul’s quote was humorous. " . Easy, because he did not think in that way before. Seems to me that is his way of audio life kind of think because he posted twice something with no sense in reference to what I posted about sub’s, he said twice: " you was not the first person to said that " .

But where in hell posted I that " I was the first audiophile to said that " ?

Too late to edit my post above, but for completeness I thought I should add that an active electronic crossover is called "active" because it does add gain, to correct for the above mentioned insertion loss of any filter. The steeper the slope of the filter, the more is the insertion loss, and the more gain is added by a typical electronic crossover to compensate.  The two best and most expensive electronic crossovers I know about are the Pass XVR1 and the Bryston.  Pass can do 6, 12, 18, or 24db/octave slopes.  A passive filter, like just adding a capacitor in series with the signal going to the main amplifier to create a high pass filter, is pretty much limited to 6db/octave, also called a "Butterworth" filter. Steeper slopes CAN be executed passively, but insertion loss goes up accordingly.  You want a steep slope on the low pass filter going to the subwoof, because you don't want the subwoof contributing to midrange and treble, where it is likely to add distortion. In most cases, however, you can get by with a 6db/octave slope on the high pass filter, if your main speaker has full range capabilities.  Exactly where to set the crossover points is a matter of experimentation.

I truly did wonder why you thought Raul’s quote was humorous. Along the way, I could not resist the anatomical pun. However, I do know that autocorrect is a bitch.

My understanding of the classic REL set up is that the signal to the REL subwoofer is derived at the interface between the main amplifier and the main speaker. That full range signal is routed to the input of the REL subwoof amplifier which has a low pass filter before its input. The REL subwoof thus augments the main speaker at very low frequencies. This method does not result in reducing the bass frequency burden on the main amplifier or even the main speaker. Perhaps I’ve got it wrong. I suppose all this belongs on another forum, but drbond seems interested, and he is the originator of this thread. Otherwise, sorry for the digression.

drbond, The classic approach is to drive an electronic crossover from the preamplifier.  The electronic crossover has built in active high and low pass filters, usually with adjustments for cut-off frequencies and a choice of filter slope.  Sometimes an electronic crossover can also add gain to the signal.  Raul and I were talking about using an electronic crossover only for a low pass filter to the subwoofer.  The frequencies above low bass would go direct to the main amplifier, but at the input of the main amplifier, all you need to do is to add a single capacitor in series with the signal.  That capacitor in conjunction with the input impedance of the amplifier will act as a passive high pass filter with a gentle slope of 6db/octave.  For that, you would like to have a preamplifier with two pairs of output jacks, but it's not really mandatory; you can derive a second output between the main amp and the electronic crossover you use to provide the low pass filter to the subwoof.  I like this second option because the high pass signal does not have to go through a second circuit.  Trade-off is something called "insertion loss"; you lose a little gain in a passive filter, usually inconsequential.

Holmz, I am no fan of the REL approach, for the reason that if you drive the subwoofer off the main amplifier output, then neither the main amplifier nor the main speaker derives any benefit in terms of reducing the workload inherent to reproducing the lowest bass frequencies.

Well I am not sure what the REL approach is other than reading @Rauls words that it derives the input from line level rather than RCAs or XLRs. So it sounded like the it was similar to a Vandersteen, however the manual is a bit light light on specifics… other than that there are the speaker inputs.
But whether the main amp to speakers are high pass filtered did not pop out.
It was 30 pages and i skimmed it, so maybe I missed it… but it does seem like it is not the same as how the Vandy unit works. That unit HPF the main speakers, and then the sub rebuilds the bass back up to where it should have been without a HPF going to the main speakers.

Moreover, any distortion in the output of the main amplifier is presented to the REL subwoofer amplifier at its input. Unfortunately, I long ago concluded that you cannot obtain all the major benefits of subwoofing unless you’re willing to add a high pass filter on the main amplifier.

Well that is what I posted a while ago, and it was a high pass filter to derive that benefit that you point out.
Then the sub rebuilds the signal back to where it should be at.

One can roll their own capacitor, or use a host of HPF to do that at various price points from a capacitor to a Harrison labs one at $50 to ones at kilo$...

Holmz, was that "humerus" or "humorous"? And why did you find it humorous?

I read too much Homer in my youth, as I had a great 7th and 8th grade literature teacher. And hence the spell checker is Greek to me.

@lewm

I suppose this means that your preferred approach would be to use both the XLR and RCA outputs from the pre-amplifier: one set for the monoblock amplifiers, and one set for the subwoofer.

If that’s the case, then it seems like my pre-amplifier would need a low pass and high pass cut off for the speakers to receive their proper signal and the subwoofers to receive their proper signal. Of course, another option would be to run the pre-amplifier signal through the subwoofer, which would be designed with low pass and high pass filters, and that signal would then pass to the amplifier to the ESL speakers. But I would think that this latter approach could degrade the signal going into the amplifier and ESL’s. It might be a no-win situation. . .

Thanks for the info, Raul.  You remind me that long ago I did consider just adding a capacitor in series with the input of my main amplifier, to create a Butterworth type hi-pass filter.  That still seems the least harmful way to do it. I calculated a .02uF capacitor (or two per channel for my balanced amplifiers) would do the trick for my amps, with an 80Hz flex point.

Holmz, I am no fan of the REL approach, for the reason that if you drive the subwoofer off the main amplifier output, then neither the main amplifier nor the main speaker derives any benefit in terms of reducing the workload inherent to reproducing the lowest bass frequencies. Moreover, any distortion in the output of the main amplifier is presented to the REL subwoofer amplifier at its input. Unfortunately, I long ago concluded that you cannot obtain all the major benefits of subwoofing unless you're willing to add a high pass filter on the main amplifier.

Holmz, was that "humerus" or "humorous"?  And why did you find it humorous?

Lew, the high pass is made it at the input of my amps ( cap/resistor ) the low pass is made it by the Velodyne electronics. Maybe you can do the  same or look for a second hand Bryston croosver.

In the link I just posted you can read about 12"/15" drivers characteristics inside the same catalog models.

After last week’s talk about a system I find ^this^ humerous.

 Lastly, if you don’t have a subwoofer or preamp output on your amp or preamp, subwoofers such as the RELs we sell have a specific high level input which runs off your amplifier’s speaker binding posts.

There is a certain simplicity and elegance in running the sub input off of the speaker’s binding posts. Not sure if it is just REL and Vandersteen, or if there are others as well.

Is there a "best" approach for monoblock amplifiers with two sets of binding posts?

I’m not sure I understandI?

I am guessing that the speakers have bi-wire posts?
So it sort of depends on whether you 4 sets of wire pairs, or a bundled bi-wire and whether it is a single end at the amp, or if there are two set of ends… and whether they can splay wide enough to hit both sets of outputs.

As I mentioned, I've never used subwoofers before.  Based on limited reading, it seems that there are multiple approaches to connecting the subwoofers to a system.  (e.g.   All subwoofers have at least an RCA input for line level connection from your preamp or variable output on your amplifier. Do not use the record or tape output! These are fixed and you will have maximum bass at all times no matter what your main volume is set at! Some subwoofers have left and right inputs. If your preamp has left and right outputs, use two RCA cables for these. The subwoofer combines the channels inside. If your preamp has left and right outputs but there’s only one on the sub, use a Y combiner adapter. These can be had for $5 or so. Lastly, if you don’t have a subwoofer or preamp output on your amp or preamp, subwoofers such as the RELs we sell have a specific high level input which runs off your amplifier’s speaker binding posts. This cable simply piggybacks on your main speakers and does not draw any power from your amp. In this way, no matter what your system is, there’s a sub for you. )

Is there a "best" approach for monoblock amplifiers with two sets of binding posts?

Lew, the high pass is made it at the input of my amps ( cap/resistor ) the low pass is made it by the Velodyne electronics. Maybe you can do the  same or look for a second hand Bryston croosver.

In the link I just posted you can read about 12"/15" drivers characteristics inside the same catalog models.

R.

Raul, Which of the current Velodyne subwoofers do you like for a moderate size listening room and for crossing over below 100Hz? Would you use the built-in electronic crossover?  Pass makes or used to make an electronic crossover.  I have searched for one in the used market, because I have some faith in Nelson Pass, but I have never found one for sale.

Dear @drbond : " adding a subwoofer can make a real difference in other areas, such as sound stage, imaging, mid-range, etc. I’m not really sure things can sound much better, but I think it’s at least worth a trial to see if it’s any better..."

Yes, exist several room/system benefits but your " key " words in that statement are:

" worth a trial..."

I could think that no matters what no one could knows if needs or not sub’s till he " trials " in his room/system.

Yes, you have to test it.

R.