Why Rumble One Side of Album

@big_greg , the Heron is a fine pre amp but, It is just a preamp. The DEQX provides preamp capabilities with a complete set of digital signal processing functions including bass management with the capability to match your subs in time and phase with your main speakers, room control and high resolution EQ.

Once you hear a system that has been completely corrected and adjusted so that the two channels match perfectly you will never go back to straight analog. The benefits are simply to great and override any advantage a strictly analog system might have. Just an FYI 

@mijostyn  The dual 15" subs are Rythmik F25. The two 13.5" are SVS SB13 Ultra.  I'm really happy with my current preamp, the Herron VTSP-360.

@big_greg , you are certainly not lacking in the subwoofer department. The two 13.5s I assume are JL Audios.  What subwoofer uses two 15" drivers?

Next time you are thinking about a new preamp you should check out the Trinnov Amethyst and the DEQX Pre 4 or 8. Digital subwoofer crossovers and time alignment are built in. You can get rid of the rumble and still feel the bass. 

@mijostyn The jury is out on the Kab filter at this point.  As you mention, I don't feel the energy of the subwoofer quite as much, but so far everything sounds "better".  It will take some extended listening to sort it out and if I don't like the Kab unit, it was less than $200, one of the least expensive items in my analog chain.  I have 4 subwoofers with a combination of 4 15" drivers and 2 13.5" drivers, so I'm not lacking for bass, but there is a noticeable difference.

Subwoofer manufacturers do not want to scare you out of buying their product by telling you you have to spend another 3 or 4 thousand dollars in cross overs and wires to get their sub operating right.

True, it is partially about the money, but not my primary reason. Primarily, I really like the Sabrina X and didn’t want to ruin what I heard. If I can’t integrate the subwoofers, I would probably purchase Wilson’s crossover..but for now I need to work on power conditioning and room acoustics.

I should add that I believe that with a perfect crossover the Sabrina X would be relieved of that 1 meter 31 Hz requirement and the sound would improve,, but what crossover and which interconnects?

@big_greg , You have to know what the slope is. What They mean by crossover point is that the filter is 3 dB down at 20 Hz. It starts rolling off a little higher depending on the slope. Analog filters can not get as steep as digital without causing problems. You probably start rolling off around 26 Hz. This is not something you would hear. It is something you would feel or rather would not feel.

@vonhelmholtz , that is extremely misleading. Speaker measurements are made at one meter. This means at a normal listening distance in a normal room your speakers are down 3 dB at something like 80 Hz! Never and I do mean never do you want to run subwoofers with just a high pass filter. You miss a huge opportunity to clean up your midrange and upper bass. Cross up higher and use a two way crossover. Subwoofer manufacturers do not want to scare you out of buying their product by telling you you have to spend another 3 or 4 thousand dollars in cross overs and wires to get their sub operating right. 

My new speakers (been waiting for five months) are 3db down at 31hz and my subwoofers take care of the lower octave w/o high pass filter.  So, I'll start with turning off the subs.

@mijostyn the RF1 is supposed to cut at 20hz. I haven't listened to anything bass heavy yet. First impressions are very positive. Bass seems present and tight, nothing noticeable affecting upper frequencies. 

Is it always on the same side?

No..not always and sometimes both, but many records are dead silent.

@big_greg , I have a very effective digital  rumble filter 80 dB/oct @ 18 Hz. I would estimate that 2/3 of the rumble is above 18 Hz and clearly audible on many discs. Pushing a rumble filter up higher destroys your bass especially if it is analog. Having a rumble filter is no excuse for the people cutting lacquers on poor lathes. 

OP,

Is it always on the same side?

My KAB RF1 arrived today.  I recently bought a Boz Scaggs Greatest Hits Live record that made my woofers look like they were going to jump out of their enclosures.  With the RF1 there was NO woofer pumping whatsoever. 

The clipping indicators on my amps often flash (I think they are overly sensitive!) when I play vinyl.  I turned it up louder than I usually listen and they did not come on at all, so it appears to have lightened the load on my amps also. 

I only listened for a few minutes (work and all that) but didn't notice any degradation of sound.  I'll be able to do some extended listening later this week.

@vonhelmholtz , unfortunately, this is a very common problem. The masters of  the sides may be cut on different lathes. A lathe can rumble just like a turntable. All the stampers made of that master will have to same rumble so generally all the records from the same supplier will be affected. I must have at least 50 discs that have embedded rumble. They are all modern pressings made on old lathes that have not been maintained well. I am not entirely sure but I do not think anyone is still making new Lathes.

No need to put up with the rumble! Either you pursue a phonostage with rumble feature built in or try this device. Many here have tried this device on @roxy54 recommendation and have great success in eliminating rumble,

https://www.kabusa.com/frameset.htm?/rf1.htm