Phono Stage upgrade to complement Dohmann Helix One Mk 2

@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.)

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.

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.

@lewm

because of the quality components of the pre- and amp, I am leaning towards an capacitor HPF, as opposed to running it through the sub, which just has a standard 6db per octave HPF, which would just be a standard, probably low-grade capacitor, correct?  A silver Duelund CAST capacitor in line with the two components, and then a separate line to the subs: it seems that Martin Logan subs might fit in the system better, since they also make ESL, and are more designed for a two channel system.  It seems that the Velodyne is for multi-channel home theatre use.

@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.