High Level Subwoofer Inputs: A Necessary Feature?

Kal Rubinson

Well-Known Member
May 5, 2010
1,926
311
525
NYC/CT
www.stereophile.com
So, CJ (and others) should really say their preamps (or amps) are Polarity Inverting.
Yes.
If the sub signal is inverted (relative to the mains), wouldn't that create "destructive interference" that impacts the perceived bass response (depending upon speaker/room interaction)?
Yup and that's why having a polarity switch is a good idea.
 

DetroitVinylRob

Well-Known Member
Dec 29, 2016
31
28
85
Metropolitan Detroit area, MI
The argument is that high level inputs to one's subwoofer(s) are necessary to keep the character of the mains amplifier(s) to the subs.
The argument seems legitimate, but I have never tried low level or LFE inputs. Any thoughts on this?
My recent experience with a pair of new S812’s and the long standing Atma-Sphere MA1 SE’s really proved out with the high level set-up. No regrets. As REL suggests, the integration of amp character really makes the diff. Never had a mid bass sound so right. If I wasn’t going to Classic Audio T3.4s this Saturday, I would be highly considering going towards an (x6) sub array.
 

Cycles2

Well-Known Member
Feb 27, 2018
3
0
66
I recently had a REL S/510 and connected the high-level input from my Boulder 2060 amp, which drives Maggie 20.7s. The high-level method seemed to get in the way of the terrific mid-bass that the Maggies produce. I preferred connecting the REL S/510 using the low level from my AR preamp.
 

musicfirst1

VIP/Donor
Mar 8, 2015
321
157
345
59
Canada
I recently had a REL S/510 and connected the high-level input from my Boulder 2060 amp, which drives Maggie 20.7s. The high-level method seemed to get in the way of the terrific mid-bass that the Maggies produce. I preferred connecting the REL S/510 using the low level from my AR preamp.
So are you saying that you observed this mid-bass effect between the high level vs the low level inputs with exactly the same settings on the sub (crossover/gain/phase)?
 

DelsFan

New Member
Nov 15, 2019
3
2
3
62
I just skimmed this thread and shouldn't be here in the first place (work, play, work or play? I choose play.) One thing that seems missing here is the complete difference in signal (usually) between what is going into a sub's LFE input, from the A/V Receiver's LFE output, and a sub's high level input, usually coming directly from the speaker taps of the A/V Receiver (to be filtered at the sub, not the Receiver). REL suggests one sets all their speaker settings on one's A/V receiver to Large; if one does this, only "effects" information is output via the LFE channel, whereas all the L+R information (lows, mids, highs, everything) is going to the sub's high-level inputs (where, then, the sub's crossover filters out the highs at whatever point works for your other speakers/room, 100 Hz, 80 Hz, whatever...).

What sending a high level signal from the Receiver's speaker taps does, if your sub is musical and quick, is allow the sub's pacing to match exactly the pacing of whatever is coming out of your L and R (and/or C) speakers. This is important for music, but if you have a sophisticated ($$$) system and your L+R+C setting set to large as is recommended, the full-range signal going to the sub will give more coherency when watching movies also. If you have a really sophisticated system, you might have two subs receiving high level signals from the L+R channels as well as (optionally) the LFE channel, another larger sub for LFE information only (explosions, etc), and another (fourth sub) NOT receiving an LFE signal but only the Center Channel (full-range, high level) signal. In my not-acoustically-great-for-home-theater family room, I'm headed toward one small center channel sub under my wall-mounted television, receiving a high level input from Center Channel speaker tap only, no LFE input, and another larger sub in the corner which will have a high level input from the L and R speaker taps, and an LFE (effects only) signal sent to it's LFE input.

Regardless of the sophistication of one's system, a big advantage of having a full-range high-level signal sent to one's sub is there is a lot more synergy between all the speakers when this is done. And if you have more than one sub, one may receive an LFE input only and another might receive high-level (full-range) signals. Remember, an LFE signal is mostly for booms and bangs and explosions; if you have your L+R+C speakers set to large, only "Effects" information being sent out via an A/V receiver's LFE output.

Finally, while there might be a little distortion imparted though the speaker taps, I think there is minimal to no downside (and lots of upside) due to the high level signal going to ones sub having passed through the amplifier of an A/V Receiver first. If you have a cheapo A/V Receiver then the case could be made, but if one has a cheap A/V Receiver they probably own cheap subs also - certainly none with the option of receiving a high input signal in the first place.

Summary: With one's speaker setting in their A/V Receiver set to Large, as recommended by REL, the LFE channel is only an effects channel. Letting a sub receive the lower frequency information associated with vocals and/or music via a high-level input is (what they say is) a big advantage when it comes to synergy and coherence. Even bigger when one sub receives LFE channel information only, and another sub receives high level information (only).
 

Kal Rubinson

Well-Known Member
May 5, 2010
1,926
311
525
NYC/CT
www.stereophile.com
What sending a high level signal from the Receiver's speaker taps does, if your sub is musical and quick, is allow the sub's pacing to match exactly the pacing of whatever is coming out of your L and R (and/or C) speakers.
This is a speculation. Do you have any proof of this?

In my not-acoustically-great-for-home-theater family room, I'm headed toward one small center channel sub under my wall-mounted television, receiving a high level input from Center Channel speaker tap only, no LFE input, and another larger sub in the corner which will have a high level input from the L and R speaker taps, and an LFE (effects only) signal sent to it's LFE input.
The wavelengths attributed to the sub(s) are so long that proximity to the main speaker is not a big issue. What is a big issue is their placement to minimize modal influences.

Regardless of the sophistication of one's system, a big advantage of having a full-range high-level signal sent to one's sub is there is a lot more synergy between all the speakers when this is done.
See my first comment.

Finally, while there might be a little distortion imparted though the speaker taps, I think there is minimal to no downside (and lots of upside) due to the high level signal going to ones sub having passed through the amplifier of an A/V Receiver first.
Again.

Summary: With one's speaker setting in their A/V Receiver set to Large, as recommended by REL, the LFE channel is only an effects channel. Letting a sub receive the lower frequency information associated with vocals and/or music via a high-level input is (what they say is) a big advantage when it comes to synergy and coherence. Even bigger when one sub receives LFE channel information only, and another sub receives high level information (only).
Sigh.
 
  • Like
Reactions: Mark Seaton

redcars

Well-Known Member
Jan 7, 2015
39
57
223
Hi guys,

Getting back to midget amps and 1000 watt subs:

I stumbled on this thread after I had posted a reply on the “SET amp owners thread.”

https://www.whatsbestforum.com/threads/set-amp-owners-thread.27070/page-76#post-679680

and

https://www.whatsbestforum.com/threads/set-amp-owners-thread.27070/page-31#post-573521

This thread is perhaps even more appropriate, so I am repeating it here with a few changes and additions:

_2020-10-13 12.05.34.jpg
2020-10-20 23.39.59.jpg

I have changed my (4) Avantgarde SUB 225 subwoofers to (2) REL 212SX subs. The change is truly phenomenal!

I have had many issues with the AG subs:

I had to recone most of the (8) drivers!
There was a huge thump when I turned them on or off (which, because of this, was seldom).
There was a background hum that additional grounding did not resolve.
They were SLOW relative to the horns.
Even when turned down so that they did not affect the midrange, they still muddied up the sound of the horns.

Despite all this, I lived with them for 20 years because I did not find anything to replace them that I thought would be better, or that I could afford, or that fit in my space, or that worked with my amps, etc.

I stumbled on a thread in a blog I seldom read: https://forums.stevehoffman.tv/threads/avantgarde-trio-set-up-revisited-question.729213/

I contacted the thread starter in England, and one thing led to another.

I ordered a pair of (the newest) REL 212SX, and a pair of SR subwoofer cables designed for the RELs.

https://rel.net/shop/powered-subwoofers/serie-s/212-sx/

https://www.synergisticresearch.com/cables/atmosphere/subwoofer/atmosphere-relspec-subwoofer/


The two RELs are each powered by 1000W amplifiers. That makes a total of about 2008+ watts!! Obviously, most of it is unused.

The RELs connect to the high-level amp speaker terminals just as the AV subs did. This was a critical requirement for all the subs that I had considered in the past. I did not want to change the sound of the horns, and I did not want to add more cables or electronics.

I have not made a direct comparison of the REL high-level cables to the SR cables, but I trust that the SR cables are making a big contribution here, especially considering that I have SR cables throughout my system.

I bought my Wavelength Mercury Ag amps when I bought my Trios. I still love them 20 years later. The Wavelength Mercury was rated at 4W @ using AVVT20SL tubes. Since these tubes are NLA, I switched to the Emission Labs 20B. This turned out to be a big improvement as the AVVT was more tubey sounding and the 20B is very dynamic and realistic in my system. I suspect that they also boosted the 4W output a bit.


I wrote to REL:

If: The amps are 4W+ full power and 15-45KHz -3dB
And: The Trios are 109 Db+ efficient, and the amps are still VERY quiet.
And: The horns are rated for 3W-200W input.
And: The horns and the Avantgarde subs will play really loud now without noticeable distortion, and I avoid driving them any harder.
And: The amplifier designer/manufacturer says there should be no problem here.
And: My friend has a very similar system with the same speakers and two REL 212SE
Then: Is there any problem with driving two REL 212SX subs to the same volume levels that I currently have?


Every person I spoke with at REL thought this should be fine, except for one influential individual who stated they would not work with my amps but refused to talk with me. I spent a frustrating week reading and making phone calls.

I held my breath and ordered the subs anyway!

After a couple of break-in stumbles, the RELs are FANTASTIC!

There is ABSOLUTELY NOTHING WRONG with my Wavelength amps driving these!

Relative to the AG subs:
They are much easier place and tune.
They integrate with the horns seamlessly.
They are fast, dynamic, powerful and natural sounding.
There is a new quietness around the musical notes coming from the horns that has never been there before.
The soundstage is larger, but naturally recorded voices and instruments are not.
Likely much more that I have yet to discover!


I am a happy camper!

Best,
Don
 

Ron Resnick

Site Co-Owner, Administrator
Jan 25, 2015
8,641
3,034
780
Beverly Hills, CA
Congratulations, Don! That is a wonderful outcome!

(Purely out of curiosity why did you choose the 212SX rather than a pair of REL No. 25s or Gibralter IIs on each side?)
 

LL21

Well-Known Member
Dec 26, 2010
11,833
689
658
Yes, congrats...sounds like a fantastic result. BTW, you have a fantastic system, and I have to say, your room itself is looking a lot like Mike Lavgine's. Impressive!
 

redcars

Well-Known Member
Jan 7, 2015
39
57
223
Congratulations, Don! That is a wonderful outcome!

(Purely out of curiosity why did you choose the 212SX rather than a pair of REL No. 25s or Gibralter IIs on each side?)

Hi Ron,
Thanks for your comments!

1. Price :)
2. My friend Chop has the same speakers and changed his Avantgarde subs to the REL 212SE with great success.
3. I asked REL about this and they said that they had more experience with the 212 in this sort of system.
4. The horns cross over at about 120 Hz, and the rear and bottom passive drivers (there are four 12 inch drivers in each sub) of the 212 work well to blend with the horns.

Best,
Don
 
  • Like
Reactions: Ron Resnick

redcars

Well-Known Member
Jan 7, 2015
39
57
223
Yes, congrats...sounds like a fantastic result. BTW, you have a fantastic system, and I have to say, your room itself is looking a lot like Mike Lavgine's. Impressive!

Hi LL21,
Appreciate your comments.
The room was built as a house addition over my garage. It is patterned after Mike Lavigne’s room, but a little shorter. Same designer as Mike: Chris Huston of Rives Audio.

See: https://www.whatsbestforum.com/threads/set-amp-owners-thread.27070/page-31#post-573521

Best.
Don
 

audiobomber

Member
Oct 13, 2020
30
11
10
Sudbury ON, Canada
My main speakers are sealed, therefore the bass rolls off at 12dB/octave. The crossovers in my subwoofer plate amps are 24dB/octave. In this configuration, the subs are always acoustically behind the mains, which makes them sound slow, regardless of whether I use a high or low-level cross.

I used a high level crossover to my subs for a while and it sounded decent, but not great. I am now running my subs through a miniDSP 2x4, which allows me to implement a 12dB Butterworth crossover, which matches my main speakers, and allows DSP with auto filters via REW. The monitors run full range. DSP filters and corrections brought the sound to a level not achievable with a traditional subwoofer crossover and amp. I am not aware of any way to implement DSP using high level sub inputs.
 

sleepysurf

Well-Known Member
Sep 8, 2010
38
5
415
... I am not aware of any way to implement DSP using high level sub inputs.

Actually, the MartinLogan BalancedForce subs, offering both line and speaker level inputs, also incorporate Anthem Room Correction, thus some degree of DSP room correction is possible. In addition, you can download custom crossover filters to match the sub(s) to specific ML main speakers. Even so, it still takes a lot of tweaking to really dial them in.
 

LL21

Well-Known Member
Dec 26, 2010
11,833
689
658
Hi LL21,
Appreciate your comments.
The room was built as a house addition over my garage. It is patterned after Mike Lavigne’s room, but a little shorter. Same designer as Mike: Chris Huston of Rives Audio.

See: https://www.whatsbestforum.com/threads/set-amp-owners-thread.27070/page-31#post-573521

Best.
Don
Hah-hah! My impressions were correct then! Well, you've certainly succeeded...because it has the very same high end custom feel which suits your very high end custom system!
 

About us

  • What’s Best Forum is THE forum for high end audio, product reviews, advice and sharing experiences on the best of everything else. A place where audiophiles and audio companies discuss existing and new audio products, music servers, music streamers and computer audio, digital to audio convertors (DACS), turntables, phono stages, cartridges, reel to reel, speakers, headphones, tube amplifiers and solid state amplification. Founded in 2010 What's Best Forum invites intelligent and courteous people of all interests and backgrounds to describe and discuss the best of everything. From beginners to life-long hobbyists to industry professionals we enjoy learning about new things and meeting new people and participating in spirited debates.

Quick Navigation

User Menu

Steve Williams
Site Founder | Site Owner | Administrator
Ron Resnick
Site Co-Owner | Administrator
Julian (The Fixer)
Website Build | Marketing Managersing