Phono Stage upgrade to complement Dohmann Helix One Mk 2

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.)

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.

Are you addressing me?

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

No problemo either way.

@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