Phono Stage upgrade to complement Dohmann Helix One Mk 2

@lewm , absolutely correct. It is like rumble specs in turntables. It is nice to be quiet but it does you no good if the lathe rumble is much higher.

@rauliruegas , I'm not sure where you are getting your figures from but with a bandwidth of DC to 20 megahertz the EIN of the seta L 20 is -134 dBu UNWEIGHTED. That is an unheard of performance. Granted I have not seen any independent testing and figures but even if Channel D was 20% off this would still be far in excess of any other phono stage that I know of. Even the lowly Seta L is better than the Boulder, 64 dB down A weighted VS the Seta L's 71 dB down, A weighted. That is close to 1/2 the noise level. 

@drbond , The stock counter weights are brass. It is a slightly different alloy from the stock I have access to. The counter weight should be within a centimeter of the bearing housing. If it is farther away you need a more massive weight. 

@rauliruegas , I think you are thinking of the Lino C which is a more entry level unit. The Seta L Plus is quieter than the Boulder and can be had with s super accurate RIAA board or it can use even more accurate digital RIAA correction through Channel D's Pure Vinyl computer program. The Seta L 20 is a really serious piece of work. Check out the specs on it. I think you will be amazed. I would love to try it but I can't get myself to spend that much on a phono stage. 

@drbond , I also have Sound Labs speakers, 645-8's. They are 8 foot tall speakers that are 36" wide. Yours are 40" wide. lewm also uses Sound Labs speakers. I am also waiting patiently for a Lyra Atlas Lambda SL. It seems we have similar tastes in transducers. I'll side with Lewm here. A current mode or transimpedance phono stage is the way to go. The CH Precision P1 phono stage is the one Michael Fremer uses. It is very expensive but falls within your limits. I think the finest phono stage currently available is the Channel D Seta L 20, an amazing piece of work. It is hands down the quietest phono stage ever made. It has a self charging battery power supply and will run in either current or voltage modes. I think it is $60,000. I plan on getting the Seta L plus set up for current mode operation. With an RIAA board it goes for a more reasonable $11,000. It is also battery operated but is not quite as quiet as the L20. It is not near as versatile as either the L 20 or the P1. But, I am one of those straight wire with gain people and prefer fewer switches and less wiring. Running a cartridge in current mode has one very major advantage. Cartridges are a type of generator. They produce current at a certain voltage by moving a coil in a magnetic field. Any generator can also be a motor, you just reverse the process by putting a voltage across the coils and you create a force that causes movement. Voltage across the coils of a moving coil cartridge affects the movement of the cantilever (tracking). A transimpedance phone stage has a vanishingly low input impedance thus there is very little voltage and there is little if any affect on the cantilevers movement. Tracking and the dynamic performance of the cartridge is improved. The Sutherland Phono Loco and BMC MCCI are other examples of current mode or transimpedance phono stages. The caveated is that you have to have a cartridge with a coil impedance as low as possible, certainly under 10 ohms.  Your Atlas is 7 ohms I believe. 

@rauliruegas , I am as neurotic as you are and do my best to choose the best performing equipment I can given the information I can obtain. Channel D lists the Seta L's A weighted SNR at 71 dB down but 67 is still better than the Boulder's 64. However, look at that Seta L20!  But the sad fact of the matter is that vinyl is inherently imperfect and generally much worse than the equipment we use to "read" it. So, I would not be so harsh on lewm. It is just a different way of viewing the same problem. Ours is also perfectly valid, neurotic but valid. 

@drbond , you just bought one of the very best if not the best turntable on the market. There are many turntables that are much more expensive that you could have gone for so, you were also interested in value. I also assume that the Dohmann's design and the reputation of it's designer led you to the purchase. 

I look at things the same way. Here is how it goes with phono stages. All my favorite cartridges are low impedance moving coil cartridges. I am not sure why that is but, so be it. These cartridges are low output and require a very quiet phono stage with a lot of gain unless you run the cartridges in current mode then the lower the impedance the higher the gain resulting in a better signal to noise ratio. The magnetic braking on the cantilever is far less resulting in better tracking than you would get with a voltage mode phono stage. All the current mode phono stages I know of are solid state. This limits my search to solid state current mode stages. I think Rob Robinson of Channel D is a brilliant designer as I think of Mark Dohmann. If you want to spend $60,000 than the Seta L20 is IMHO the way to go. It is a great example of American ingenuity. I will not spend that much on a phono stage. I went for the Seta L Plus wired for current mode. If I wind up with a second tonearm I'll get a second one.  

@drbond , The CH was also on my list but it fell off due to price and the admission that it's stock power supply is not good enough. They will be happy to sell you a second one so now you have paid for two power supplies instead of the one you should have had t begin with. The L20 gives you the best possible power supply up front, batteries that are disconnected from the line during play. The trickery does not end there either. To reduce noise to extraordinary low levels the L20 uses 20 of the Seta L's gain modules, 10 in each channel. I think this is a computer trick. You increase gain without increasing noise levels and the signal to noise ratio increases. In MkII form it now has multiple inputs and will also run in Voltage mode for higher impedance cartridges. I have no idea why you would want to. With cartridges like the Lyra Atlas SL, Ortofon Verissimo and the My Sonic Platinum Signature there is no need to look elsewhere. (that is going to cause some frowns) The sad part is that there is no way I'll get 60K for a phono stage by my wife. She had a heart attack when I mentioned $25k for a projector. So, I'll have to do with the lowly Seta L Plus. Same circuit with two gain modules, fewer bells and whistles noisier but still very quiet. Could be worse.

@drbond , You make a big mistake underestimating John Curl. The JC 1+ uses totally first class components and very slick internal layout. It is less expensive because it is mass manufactured in Taiwan. Robots do a much better job than humans and we all know that surface mount is better than through hole. There are many people who think the JC 1+ is one the best amplifiers made regardless of price. 

@rauliruegas, FM Acoustics has a very colorful web site. The 233 has way more features than I will ever need or use. It looks beautifully made. It's "Hum and Noise" spec is very misleading. "Equivalent input noise below full output 22 Hz - 22kHz: - 137 dBu." I have no idea what that means. I know what "A weighted signal to noise ration" means. It is certain that they are two different ways of characterizing noise and can not be compared. The Seta's signal to noise ration even improves the lower the impedance of the cartridge. 

@lewm , I totally agree that Channel D's web site is fractured and should be re-done. Rob Robinson is a computer geek and they view life differently than normal people. However, your comments on the companies name and product's name are trivial to say the least. By virtue of his feeling that digital RIAA correction is superior to analog filters he has already lost the analog audiophiles. No great loss IMHO. I plan on trying it when I get the unit as I already have the programming. Don't worry. I also ordered the analog circuit. 

@dover , you make the same mistake underestimating John Curl. The Hyperion is significantly softer in the bass than the JC 1+, muddy would be the appropriate term. The JC 1+ is more aggressive sounding but still manages to come of like a tube amplifier. If you demoed the two together you would never be able to justify spending $90,000 of the Hyperion. I said that wrong. You might be able to justify it but I would not.

@lewm , I heard Hyperions on big Wilsons in comparison with Boulder 2150s. I preferred the Boulders. The two most popular amps with SoundLabs users are Atma-Sphere MA 2s and  JC 1s for whatever it is worth.

@drbond I have never heard or seen a Lamm amp so I can not comment but you are very wrong about the JC 1+. John Curl's point with the JC 1 was that he can make a top amp for much more reasonable money. I wish I could send you a pair. There is much more involved in the pricing of audio gear than the quality of the parts and engineering.  What is left has nothing to do with the sound quality of the equipment. John Curl has a record that is hard to ignor. People do not want to hear that an $18,000 amp is better engineered than their $90,000 amp. So be it. My personal goal is to get Atma-Shere MA 2's a $45,000 amp which due to their design are a perfect mate for Soundlabs speakers. I would love to get MA 3s but at $145,000 I would never get them by my wife. On the other hand with the price of propane we could use the extra heat next Winter:-)

@rauliruegas , my feelings exactly. I am going with whatever produces the best results. You should look into Channel D's Pure Vinyl program. It is a lot of fun. You can compare different versions of a recording and different equipment in the analog chain, cartridges and tonearms. Very enlightening.

@drbond , my experience with current mode phono stages pretty much mirrors yours. 

Whether or not you hear the venue or get the effect that the musician is in the room is more a function of the recording than anything else. What I find the distortion inherent in many tube designs does is blur the image, Outlines become less distinct. Remember, we have essentially the same speakers. 

@lewm , in my mind, simple as it is, there is only one "right." Everything else is distortion. The "right" is what is in or on the recording. I admit that it is not always easy to determine exactly what "right" is. The most sensitive aspect of a recording is the image. I will go with whatever produces the most specific image. 

@drbond , again my experience mirrors yours. I prefer solid state in general. I am not familiar with Ypsilon equipment. We use the same tonearm and I have  a Lyra Atlas SL coming any day now (for 6 months). So, it seems we have very similar tastes. I have been waiting for Mark Dohmann to add vacuum clamping to the Helix. What are you driving the Soundlabs with?

@drbond  Well, that is a riot. My other cartridges are a Signature Platinum and an MC Diamond and I am not a huge Koetsu fan. The MSL is a lovely cartridge. The Atlas will be the last cartridge for a while. I need to replace my preamp processor and I am building a new set of subwoofers. 

@sksos , For what it is worth, I think you are much better of with @drbond 's choice The Dohmann Helix 1 or 2 with a Schroder, Reed or Kuzma arm. The motor, plater and tonearm are rigidly connected and placed on arguably the best isolation platform in existence. I am probably going to get one. I am waiting for them to develop the vacuum clamping. I will put a Schoder LT on it.  

@sksos , my mistake. You really need to take a look at the Channel D Seta L 20. It is the quietest phono stage made, is battery powered, will do both voltage and current modes ( your MSL will really sing) and has a flat output just in case you want to try digital RIAA correction and recording your friend's rare records.
@drbond , I also use a SmarTracter. The alignment to use is Lofgren B. It has the lowest distortion across the record accept at the very inner groove area. Modern engineers stay away from that area and even in the old days most records were not cut that far in.

Aligning a cartridge on the Sota can be a bouncy situation, I can't imagine doing it on the Dohmann which is even more sensitive and the entire plinth is suspended whereas with the Sota the suspended sub chassis is internal. Is there a way to lock out the suspension on the Dohmann?

@rauliruegas , I think unidin is a joke. As whether or not I can hear the difference between Lofgren A or B, I seriously doubt it. But, it make me feel better that I am using the alignment with the lowest distortion across most of the record. When aligning a cartridge I take the utmost care to get it exactly right using all the tools at my disposal. You are right in that it is a very small world and it is not easy to get it exactly right given the number of pitfalls. I am a furniture maker. I make furniture with hand cut joints that have to fit exactly right, no gaps. It takes a very fastidious mind to do that, unfortunately a mind that sees errors in everything it observes. 

@drbond , darn right the MinusK works. The benefits of good isolation are legion. I would never own a turntable that was not properly suspended. The outside world is loaded with noise and rumble, vibration of all sorts. The cartridge is a very sensitive vibration measuring device and it has no way of knowing where the vibration comes from. For fun get a seismograph app on your phone and put it on a granite countertop. Watch what happens when the wife walks around or the AC starts up. Open the garage door, sneeze. Anyone who thinks mass is enough isolation needs to perform this experiment.   Lastly, put your seismograph phone on the Dohmann's platter, dead quiet. Darn right it works. 

@drbond , If you are having trouble getting a CB counterweight I would be happy to make one for you. I had the same problem and the stock weight was too heavy for the cartridge I was using at the time. I asked everyone for a counterweight. Even Frank Schroder could not supply one in a reasonable period of time. Thrax was totally unresponsive which really pissed Frank off. Anyway, I got a brass blank and turned it on my wood lathe. The only way you can tell it from a stock weight is the color is a little darker otherwise it is an exact replica. You just have to tell be what weight you want. I still have quite a lot of that brass blank left. I also could not get any extra cartridge mounting plates from Thrax. Frank graciously supplied those. 

@holmz , You are referring to what Frank Schroder calls cartridge mounting plates. They are made from one of three materials, a phenolic plastic for very compliant cartridges, Certal (an aluminum alloy) for medium compliance cartridges and brass for low compliance cartridges. Most cartridges will do fine on the Certal plate. Cartridges like the Koetsus and the MC Diamond require the brass plate. 

The two outside holes are drilled at 1/2" centers, 2.5mm and the center hole is drilled and tapped for an M3 cap screw. I add a finger lift to all my plates. I find using a finger lift is a much more stable and reliable system of handling the tonearm. $12,000 cartridges are at risk. Frank does not add anything to his arms that might resonate including finger lifts and tonearm rests. I added a locking tonearm rest to my turntables plinth. My finger lifts are dampened with heat shrink tubing. They are made from non magnetic stainless steel wire. Drilling a hole in the side of the plates can be a daunting proposition but with a milling machine and the appropriate vise you should not have a problem. I use an interference fit with added high strength loctite. After the wire is mounted I bend it to shape.

This is what I do. All my cartridges are mounted on an appropriate plate. With the cartridge mounted and VTF set I put the stylus down on a rotating old record I do not mind scratching and measure the distance from the record to the top of the cartridge mounting plate. That distance is recorded on a 3 X 5 file card. I the use a Wally Referance tool to set both VTA and Azimuth using this measurement. There is a VTA scale on the tonearm's post. That number is also recorded. This puts the tonearm exactly coplanar with the record surface. I then set tonearm overhang for Lofgren B using a SmarTractor. I scribe a very fine line on the top surface of the mounting plate using the front surface of the arm as a guide. I can now return to the specs for that particular cartridge instantly with just a VTF gauge. Next is the hard part you need special equipment for. I verify both VTA and azimuth with a horizontal USB microscope similar to the WallyScope but much more stable. The WallyScope works but it is a bit of a PITA to use. Getting the stylus in center field and focused with a scope on a wobbly stage takes patience and a very delicate hand. Since I have neither, I constructed a horizontal microscope using the scope and camera of the WallyScope and the entire stage mechanism of an old medical microscope. It is an odd looking affair but much more stable and easier to use than the WallyScope. I have discussed this with J.R. who modified his stage a bit and it is better but still a far cry from a medical microscope. Fortunately, for these measurements you only need the low power objective which is much easier to deal with. The higher powers are needed to assess stylus wear and Zenith. Measuring angles is easy. Amscope has a program for microscopes. You can snap lines and the computer will calculate the angles for you. My standards are a VTA of 92 degrees +- 0.5 degrees and an azimuth of 90 degrees +- 0.5 degrees. All my current cartridges, the Lyra Atlas SL, MC Diamond and the MSL Signature Platinum are within spec so none of the adjustments needed modification and no shims are required. I do not measure Zenith. I do look at the styluses and take pictures of their initial shape for comparison purposes (easier to see wear), all of these cartridges are in spec by eye. At the price of these cartridges, if they were not in spec I would return them with pictures validating the problem. Actually, I would do that with a cartridge at any price. If a cartridge does not match up to it's published specifications it is by definition defective and should be replaced, no shims required. 

@drbond, I can make mounting plates but I thought it was a counter weight you needed. The counter weight of the CB is in two pieces. The larger section unscrews from the top section through which the tonearms shaft passes. There are three different bottom sections. The arm comes with the intermediate section then there is a lighter one and a heavier one. Both @lewm  and @rauliruegas  are entirely correct. Depending on the mass of the cartridge and the VTF you want to choose the counterweight that gets you closest to the pivot. Personally, I think the arm should come with all three weights. Being able to make the weights allows me to tune the situation exactly. It is just basic machining and now that I have all the drills and taps required I can turn them out rapidly. Brass is easy to polish and get a mirror finish. The only problem is matching the color. Most people would never notice unless it was pointed out to them. 

I assume you got the arm from Dohmann with the table. I would contact them first to see if they have additional cartridge mounting plates. Get at least one of each so you can be prepared for any eventuality.

@drbond, ​​@lewm is correct. However the critical issue here is the resonance frequency of the tonearm-cartridge combination. A given cartridge is going to require an arm of a given effective mass. Since you can not adjust the cartridge you adjust the effective mass of the tonearm. In the case of the Schroder CB you can do this with different mass cartridge mounting plates and different mass screws or even headshell weights. You then position the counterweight to achieve the correct VTF. With the Schroder you have the choice of several counterweights. With a heavier counterweight you will move it closer to the pivot to achieve the same VTF. This also keeps the arm's effective mass exactly the same, but what it does do is decrease the arms moment of inertia which improves the arms ability to track warps and eccentricities. 

Never set up an arm by specification. Set up and arm by testing. Equations are close to worthless when it comes to adjusting the resonance frequency of a cartridge-arm combination. There are too many variables involved. The specifications are ballpark only. You get a good test record and learn exactly what the resonance frequency is and make adjustments as required. I always shoot for 8 Hz and will settle for a little below but never higher. I also balance my own wheels.

@drbond , The Hi Fi News Analog Test Record. You will know when you hit the resonance frequency because the tone will warble. You might even see the tonearm shake.

Off topic a bit. I have been using ESLs since 1979. I now have 8 foot 645's. Roger West calls them 645-8s. ESLs HATE making bass. They will do it in a very lumpy fashion but it adds significant distortion to everything else. You get away with it only if you listen to less aggressive music at lower volumes, less than 80 dB. However Pink Floyd at 95 dB, forget it. You really need to get 4 subwoofers. It is a PITA and you have to make some other changes but I would NEVER use ESLs without them. It is like putting turbos in a 911. 

Back on topic. You really need to look into the Channel D Seta L 20 Phono stage. It is an insane piece of gear. It has the lowest signal to noise ratio of any phono stage on the market, a lot lower. It will run any cartridge made in either Voltage, Current or MM mode. It will use digital RIAA correction and you can record anyones special records to a hard drive in 24/192. Everyone I have run an AB between the vinyl and it's recording can not tell the difference. I have The Seta L Plus the L20's little brother. Just because I am running very low impedance cartridges in current mode, it is the best sounding phono stage I have ever heard in my system. The L20 is 12 dB quieter!! That is just a stunning figure. I have trouble running the MC diamond running into noticeable noise at higher volumes. I hope to get myself an L20 in the future. Channel D will give you 80% of the price on trade in. The L20 is $50,000. My problem is getting it by the wife. I will have to give her a detached garage, new windows and a new paver driveway first. My Atma-Sphere MA2 amplifiers cost me a hot tub with landscaping. Being married is very expensive. Being alone is worse. 

@lewm , quite correct. You have to factor in the weight of the cartridge. The single best way to do that is by measurement. If the resonance frequency is off, too high, mass can always be added. This is the advantage of having an arm on the light side. It is much harder to remove mass from a heavy arm. The Schroder arms have cartridge mounting plates of three masses and counterweights of three sizes. They can be adjusted for just about any cartridge. 

@drbond, the CH is a fine phono stage. It is not the Channel D Seta L20. I have a naturally aspirated 911, a Speed Yellow C4S.  You only drive around at 40 mph. I prefer 100 mph. Above that in New Hampshire is classified as reckless driving which takes speeding to a whole other level legally. You would still benefit from a proper subwoofer array, just not as much as someone who listens to Metallica at 100 dB. It is not just the added bass but the lower distortion everywhere else. Any bass note in a full range speaker is going to Doppler distort everything else the driver is trying to reproduce. If you can see the diaphragm moving it is Doppler distorting all other frequencies. I have observed naked ESRs on numerous occasions. You can see diaphragm excursions up to about 100 Hz. Which is where I cross over to subs. Even at 100 dB you can not see my diaphragms move. The difference in sound quality is exceptional. 

Where do you live? 

@drbond , Yes of course. It announces every frequency as it goes down and has two tracks, one for vertical resonance and the other horizontal.

I do not have to worry about MA2’s making bass. I cross to subs digitally at 100 hz, 48 dB/oct. It is not about bass. It is about distortion and realistic volume levels. If you play a Bill Evans record, say Waltz for Debby at the volume the music had that night at the Village Vanguard, without subwoofers the SoundLabs will crap  a brick regardless of what amp you are using to drive them.

I am down in Florida all the time. My sister lives just north of Miami and my step mother just south of Miami. You never come to New England? You need to come up the second week in October and see the colors. In Florida all you have is endless flatness, a few palm trees and hurricanes not to mention DisneyLand.

@lewm , the wider speakers may have more baffling effect which theoretically might help them with bass extension. My point is that I do not want them making bass at all. At the volumes I listen at with the music I listen to (Porcupine Tree is on right now) The bass greatly distorts everything else and cuts my headroom by 10 dB or so. The Sound Labs I have are not standard models. They are 8 foot tall 645s. They have exactly the same horizontal dispersion as your 845's, 45 degrees. I did not go for the 845s as the additional width would have been a tight fit in my situation and the extra surface area did not matter to me as I already had a subwoofer array and the right equipment to manage it. I was getting plenty of volume out of the Acoustats, a speaker 16" narrower than the 645-8s. I was sure the 4"s would not be a sacrifice. 

ESLs are not like dynamic speakers. They do not have the capability to take long excursions and they become non linear quickly under 100 Hz at higher listening levels. Because there is only one driver expected to cover the entire range the entire frequency range is affected by this non linearity. If you play them at lower levels avoiding the non linear zone of excursion they are fine. That is just not my style. Aside from this dipoles make very lumpy bass at best.

Subwoofers are a difficult topic. As @rauliruegas infers they are essential for realistic playback with almost any loudspeaker. Very few speakers produce adequate bass below 40 Hz. What a loudspeaker does at one meter is a far cry over what happens in a real room. The life and breath of music and the venue it was recorded in lies below 40 Hz. It is where concert halls breath and bass reverberates. It is the difference between a live performance and a transistor radio. To make realistic bass a system has to be tailored to it's environment. This requires digital signal processing. The only other way to do it is shear luck and you might as well buy lottery tickets.

Sorry for rambling on. I ripped my right forearm apart today, spent all day in an ER and am souped up on oxycodone.

@lewm . I'll put my black robe back on. While that is true about the double bass there is a lot more going on with a Jazz trio that will drop below 20 Hz, an undamped bass drum. The pulse you get when the bassist thumbs a string, the reverberation in the room. 

Dipoles, because they are open baffle speakers create their own set of room interactions in the lowest octaves that depending on the room and the position of the speakers in it, can be severe. If your speakers are 5 feet away from the front wall you are going to have a problem at around 100 Hz. You can easily dampen frequencies above 250 Hz using acoustic tile behind the speakers, but there is no stopping frequencies below that.  With a great room you can get reasonably flat bass throughout the room except at the walls using dynamic subwoofers. With enough power room control can take care of the rest.

By nonlinear I am referring to the tension on the diaphragm. Like any driver as the diaphragm travels over a certain point it starts to stiffen. This interferes with reproduction just like any other driver. Because of their large surface area ESL diaphragms do not have to move as far as a dynamic driver but still excursion is limited to a few mm and low bass notes at volume can easily exceed this. Sound Labs are actually worse because the diaphragm is segmented into small sections. On top of all this you have doppler distortion. Since our ESLs are "full range" drivers this affects the entire audio spectrum. With a two or three way speaker the distortion only applies to the spectrum of the woofer. 

The real issue here is we listen to music differently. I hate being volume limited while you prefer lower volumes. I also will listen to raucous music you do not like. Yes, there are very dynamic moments in classical music, My favorite is in the last movement of Stravinsky's ballet, The Firebird.  I be willing to bet I listen to that at a good 6 dB louder than you. 

@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. 

@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

@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 , you will hate any analog high pass filter. To operate a subwoofer correctly all filters have to be digital. The highest quality units now use 64 bit floating point processors and have none of the issues older units had like the volume control problem. Conversions in and out of 24/192 are invisible. 

@lewm correct. IMHO the Velodyns are mid Fi. The Balanced Force MLs are superior in every way The Magicos Q series, also balanced force, are the best on the market because of their extremely stiff, heavy enclosures. Because the electronics in all subwoofers are sort of second rate I prefer passive ones. You can only get these in kit form or build them yourself. Otherwise you can just bypass the electronics. This is mandatory for the filter section. Some class D amps are tolerable for subwoofer duty but the best bass I have heard comes from A, AB amplifiers with vanishingly low output impedances. The JC 1 is a killer subwoofer amp. These produce way too much heat to put in an enclosure. Only Class D amps are efficient enough for that.

@lewm , all my filters are digital. I can select any slope and any frequency at 1 Hz intervals and I can make adjustments on the fly from the listening position. This is TOTALLY different than analog filters. 

@rauliruegas , I have heard you say on multiple occasions that digital reproduction is not just a little, but far more accurate than analog. Have you changed your position? I have owned Velodyne Subs and have listen to some of the more current models. I would never have one in my system. There are many great woofer drivers out there now. The differences in the good ones are relatively minor in comparison to the differences in enclosures. There is not one commercial subwoofer I would have in my system, not one. Not even the Magicos (to effin big!). But in order to have a chance at being uncolored the sub has to have two drivers at opposite ends of the enclosure operating in phase. This keeps the sub from shaking at volume which causes distortion. The only commercial subs that do this are the Magico Q Series, Some of the KEFs and the ML BalancedForce series. The best way to avoid driver distortion is to use large ones of high quality. The amps used in any of these subwoofers are compromised because they can not produce significant amounts of heat. They also have to fit within the subs and the manufactures want to keep them small. IMHO passive subwoofers with outboard electronics are the only way to go. I double darn guarantee that not one subwoofer plate amplifier can produce the bass of a JC1. Unfortunately, this is a much more expensive approach but that is life. 

Now as for as my turntable is concerned. If I remember correctly your most significant concern with phono stages is an accurate RIAA correction. My phono stage is connected to a Lynx Hilo, a studio ADC, DAC router. The phono stages output is set to flat (no RIAA correction) and the correction is performed by a program in my audio computer. It is way more accurate than anything you can do in the analog domain, very cool. You should try it or are you going to be one of those stuffy analog only guys. Good luck trying to find an analog record now a days.

@holmz , Not at all. You ever tried an analog crossover on ESLs? Wel I have, several ones and they all turned out to be awful in the end. You can do it but there are far superior ways.

@drbond , 6 dB/oct is no where near fast enough to get the drop in distortion and increased head room I have been talking about. My filters are currently 48 dB/oct and the only way you can do that in an invisible fashion is with digital crossovers. I have been through every permutation of this problem some several times and have lost a lot of hair over it. If you do not want to use anything digital in your system you are better off without subwoofers otherwise they will drive you nuts and you will have wasted a lot of money. Subwoofers have to disappear into the music. You should not know they are there until a very low note comes along. In order to get the benefits of lower distortion and increased headroom, critical for ESLs you have to cross over in the area of 100 Hz which makes life even more difficult. Subwoofers also have to be placed in specific locations in order to work well. They are over 6 dB more efficient against walls and even more in corners. You also eliminate some (but not all) of the room interaction this way. This places them three to 5 feet behind the ESLs. In order to get the speakers aligned in time the ESLs have to be delayed a little. You can only do this in the digital domaine. Any other approach is a compromise you are not going to like. 

@rauliruegas , if you listen to any modern music of course you do. It is all digitally recorded. I record other people's special records to my hard drive in 24/192. You can easily AB the recording with the original and nobody can tell the difference. In other words the full characteristics of my turntable playing a record are 100% maintained even after all this digital monkey business. It is also a lot of fun getting cool free music! 

@lewm , the problem is most commercial subs do not have any HPF. Yes, the LPF is always active. Analog crossovers add distortion and phase shifts. Some can shift phase 180 degrees with a knob but only by ear which is a trial and error nightmare. The crossover you are thinking about is too low. You should be up around 100 Hz to get the maximum benefit in terms of lowering distortion in the SLs. The problem is the subs have to be in time and phase with the SLs or you will hear them. this is true at 80 Hz also. I have listened to every crossover point and slope you can think of between 40 and 150 Hz 1 to 10th order slopes. As I have said before I can change crossovers on the fly from my listening chair. My Acoustats did better at 125 Hz. For some reason the SLs do better at 100 Hz. My guess is it is more surface area. Below that you start to loose headroom and increase distortion. Another issue is a subwoofer array for your system would be more involved than dr bond. He has 7 foot SLs with a high ceiling so below 200 Hz he is point source. You have 8 footers and if you have 8 or nine foot ceilings you are line source. In order to match the power projection of a line source speaker you have to have a line source sub array. This mean subwoofers at up to 6 foot intervals from wall to wall, corner to corner. I operate mine in stereo due to the high crossover point. Obviously, this is a more expensive set up but you are very clever and capable of building your own. 

@lewm , sorry I forgot to mention. At this moment I am using my outdated TacT 2.2X. I have a DEQX Pre 8 on order. It has a much faster processor so you do not have to worry about digital volume. When you lower volume in the digital domain you loose bits. With my Tact at low volumes you are worse than a CD about 12 bits. With the Pre 8 you are still above 24 bits. The Pre 8 also has four crossovers so I can see what a ribbon or horn tweeter will do above 12 kHz. There is the Pre 4 which is essentially the same unit as the 8 but with only one crossover for your subwoofers. You manage the units with your computer and a dedicated program. You can design any target curve equalizing the system any way you want. I keep mine dead flat until 100 hz where I increase the bass at about 3 dB.oct down to 20 Hz were I roll off steeply at 80 dB/oct creating a digital rumble filter. It also prevents launching your subwoofer cones across the room when you drop the tonearm:-)

@lewm , any decent processor corrects phase and time. Once in numbers you can do pretty much anything without adding any distortion. It is hard for old analog guys to believe. If there is anything detrimental in the process the advantages far outweigh it. It is a new world. Some of the old ways still apply after all, our ears are analog devices. However, when it comes to processing signals to do exactly what you want, digital rules. Lew, if we were face to face I would have absolutely no problem proving that to you. 

@rauliruegas Of course not! That does not change the fact that it is digital recordings we are listening to and they are superior in many ways to older analog ones assuming they are mixed correctly and not compressed into oblivion. 

@drbond , The best bass I have heard comes from monster class A amps with exceedingly low output impedance, vanishingly low. I agree that passive subwoofers are the way to go. The problem is getting them, ones that fit your spec. AudioKinesis swarms do have outboard electronics and Duke might sell you a set without the electronics. The swarm system is a great, high value subwoofer array for people with small to intermediate size rooms and systems in the $20,000 or so price range. To play around and get used to subs and not spend to much money doing it I suppose they are fine. In the end they are not up to the quality of the rest of your system and even with four 10" woofers they are really not enough for your rather large room. My current system uses four 12" subs in a room 16 feet wide. There is no back wall as it is an open concept house. The room was designed to avoid standing waves. The system I am working on now will include eight 12" drivers in 4 enclosures. 

The best way to get passive sub is to make them. There are great kits available at Parts Express with SOTA drivers. They are as good as 90% of the commercial subs on the market and very easy to build. The only fly in the ointment is putting a fine finish on them. You can give them to a Piano restorer and they can put an excellent black finish on them. Many people cover them in equipment carpet. 

@lewm, not at all. I can AB straight analog with full bore processing by pressing a button. I have to assume you know what you are listening to and in that context it is a no brainer.  I know you don't think so which makes it more fun. 

Ask Duke if he can do two 12” drivers per enclosure in a balanced force arrangement. Sealed enclosures only please. 

@drbond , just another dance tune. I have three versions of it, two by Biggs and another by Herrick which I like the best. That note makes my vision blur. 

For subwoofers you want an amp that goes down to 0 Hz, DC or darn close. The Parasound JC1+ is perfect. It will produce it's rated power down to 2 Hz. 180 amps!

@lewm , it is not just notes. Large venues breath. Lots of noises are generated by instruments that are not notes. It is that information under 30 Hz that gives you the sensation of a live performance and elevates a system from just another stereo. Low C causes my entire house to rattle, my vision blurs and you feel it but you do not hear it. The hand of god. IMHO ESLs make lousy subwoofers. 

@rauliruegas , shoot Raul, I wouldn't put those in my tree house. Huge resonating enclosures, crossovers all over the place, el cheapo air motion transformers. Yuk. A pair of LS3 5As on stands with subwoofers would sound better than those things. Remember the Nearfield PipeDreams. You could not get those speakers to image if your life depended on it. 

@rauliruegas , now you've hurt my feelings. No desert for you tonight:-) There are a few strange comments your references make. Nodal behavior is a function of the room. Certainly it can be modified by placement. This fellow asserts that more drivers result in a lower LF factor (Low Frequency). I can only guess what he means by this.n Maybe @lewm knows.  Larger and more numerous drivers decrease excursion distances resulting in less distortion. He want to position subs at the midpoints of walls. If you are using your subwoofer array to lower distortion in the main speakers the higher crossover points have more benefit particularly with ESLs. Crossing at 100 Hz requires a stereo subwoofer array to avoid locating the subwoofers. There are also differences in requirements for the type of main speaker, line or point source. If you put a point source subwoofer array under a line source the subwoofers will become lost not having the same power projection. Its easy to cut volume but harder to increase it. Given large high quality drivers the quality of the subwoofer is mainly determined by the enclosure, large enclosures being significantly more problematic. Controlling resonance in a large panel is much harder than controlling resonance in a small panel. Given proper digital signal processing it is very possible to make a 1.5 cubic inch enclosure with two 12" drivers. Given enough power you can make them do anything you want and you do not need ports to get lower. We have the automotive crew to thank for modern driver designs, light cones, large voice coils and magnets, kapton formers, adequately vented, with shorting rings to lower distortion and finally long throw suspensions and kevlar spiders. You can get the finest subwoofer drivers for $250.00.

The wife wants me to make dinner. 

@lewm ​​@rauliruegas @drbond , that is lay instinct. I can make a 7 hz sound in a telephone booth. It will not reverberate but it is quite measurable. Same goes for most rooms. It is true that you only hear the harmonics but you feel the note and you can measure it with a calibrated microphone which I have. Very few subwoofer systems are capable of projecting anything below 25 Hz. It takes a lot of surface area to create the wavefront properly. I currently use four 12" drivers in a 16 foot wide room. The 3 dB down point is 18 Hz and it falls off rapidly under that. The system I am working on has eight 12" drivers. I would use 15s but they would make the enclosures too large for my situation. Eight 12's are the most I can cram into the room. If that does not do it then I give up. Playing Vinyl I use a very steep subsonic filter anyway, 80 dB/octave.

@lewm , it depends on what state I am in. In New York and Vermont I can, but in Rockingham County, New Hampshire, not at all. 

SLs have so much surface area impedance matched to air that they can surprisingly produce very low notes even though they are dipoles. I don't think they can do it accurately, the wild swings in output below 100 Hz are measurably worse than regular dynamic speakers in my room anyway. As lewm knows I cross out of them to the subwoofers at 100 Hz. Relieving them of low bass helps them to perform better everywhere else. It sounds like lewm is thinking of the possibilities. I was always a volume freak. If it did not go loud I was not interested. I got into subwoofers back in 1979 because I had fallen in love with loudspeakers that did not go loud enough, not even close. Subwoofers solved that problem but added others which I struggled with for years not willing to give up on ESLs running cleanly at volume playing anything from Chopin to Nirvana and everything in between except Lawrence Welk. ESL owners who lead more sedate lives might fare better without subwoofers especially if they are unwilling to go down the digital signal processing path. Bad subwoofers are way worse than no subwoofers. Distortion is noticeable lower in full range ESLs if you remove the bass from them. The louder you listen the more noticeable this becomes.

I have to go clean my Schumann Resonators now.