Phono Stage upgrade to complement Dohmann Helix One Mk 2

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.

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.

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 " ?

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.

@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.