Subs only powered by Class A/AB to augment my Zus

spiritofmusic

Well-Known Member
Jun 13, 2013
6,510
108
63
E. England
#21
Folsom, the Lundahls are input-level interstage transformers, LL-1585.
Hypex N-Core amps are UCD 400W.
Down firing drivers are 12” Eminence LAB-12.
Simple low-pass filter btwn subs and main spkr using just a Duelund cap and Vishay resistor, no complex crossover (similar simplicity in high-pass filter to Radian super tweeters).
I’m using SR Black fuses and Sablon Corona Elite pwr cords.
 
Last edited:

V-Squared

New Member
Jun 9, 2017
6
0
1
#22
Very interesting...thanks. We have good success doing this where the big Velodyne is in the back corner facing the big Wilsons which are in the front. We do use a Sablon Audio power cable. When you say high level input vs 'from the pre'...in order that the the sub amp sees the same signal as the main towers do...can you explain if what we are doing is actually what you are suggesting?

Right now, the CJ GAT 2 preamp has 2 sets of outputs...we run one to the Gryphon Colosseum to drive the Wilsons...and the other set of outputs goes to the Velodyne. I think this means the Velodyne IS seeing the same as the main towers...but just in case, thanks for any clarification on what you are advising.
Hi LL21:

I think he is referring to connectivity of the subs to the high speaker-level signal (amp out/speaker input), which is an option on some subs, like my REL G1’s.

I found that that approach (on the G1’s), muddied up the mids on my Magico speakers - it doesn’t have the LP cutoff that I was seeking.

An alternative is to run the signal from your preamp, as you described, and that is my preference as well, for a couple of reasons: 1) It seems to me that running the input of the sub amp from the output of the main amp, introduced inherent latency, due to an additional amplification stage, and that might be most evident in high impact impulse responses/kick bass/etc. signals, and hence, less impactful attack; and 2) the LP filtering I observed was much more to my liking, reserving the sub’s contribution solely to the lower register (I set the LP to 30HZ Max).

I had another concern with the above approach, and that was the risk of introducing significant negative induced back-EMF (electromotive force) from the large servo/motor/coils, back into the critical low level (XLR / S.E.) preamp outputs, effectively distorting the mains as well. I suspect that is one reason many folks recommend use of the high speaker level connections, as they are a much lower impedance and hence not as severely impacted. I resolved that delima by use of a sub isolator module (an option on my MSB Reference DAC). This electrically isolates the reverse induced sub noise, from the mains by a factor of 1:7. MSB offers a stand alone version, as I recall - I’m not sure if the isolation is the same as on the module.

But the point is, I now can: A) pick off the same signal for my subs, as for my mains; B) minimize group delay/latency; C) alleviate the negative effects of the back EMF; and, D) attain much more desirable LF filtering characteristics, than that observed with the alternative connectivity approach.

Regards,
V2
 

Ron Resnick

Site Co-Owner, Administrator
Jan 25, 2015
5,356
134
63
Beverly Hills, CA
#23
Very interesting...thanks. We have good success doing this where the big Velodyne is in the back corner facing the big Wilsons which are in the front. We do use a Sablon Audio power cable. When you say high level input vs 'from the pre'...in order that the the sub amp sees the same signal as the main towers do...can you explain if what we are doing is actually what you are suggesting?

Right now, the CJ GAT 2 preamp has 2 sets of outputs...we run one to the Gryphon Colosseum to drive the Wilsons...and the other set of outputs goes to the Velodyne. I think this means the Velodyne IS seeing the same as the main towers...but just in case, thanks for any clarification on what you are advising.
The speaker level output would obtain (REL style) if the Velodyne were driven by the Gryphon amp, not the c-j preamp.
 

DaveyF

Well-Known Member
Aug 1, 2010
5,858
52
48
La Jolla, Calif USA
#24
Hi LL21:

I think he is referring to connectivity of the subs to the high speaker-level signal (amp out/speaker input), which is an option on some subs, like my REL G1’s.

I found that that approach (on the G1’s), muddied up the mids on my Magico speakers - it doesn’t have the LP cutoff that I was seeking.

An alternative is to run the signal from your preamp, as you described, and that is my preference as well, for a couple of reasons: 1) It seems to me that running the input of the sub amp from the output of the main amp, introduced inherent latency, due to an additional amplification stage, and that might be most evident in high impact impulse responses/kick bass/etc. signals, and hence, less impactful attack; and 2) the LP filtering I observed was much more to my liking, reserving the sub’s contribution solely to the lower register (I set the LP to 30HZ Max).

I had another concern with the above approach, and that was the risk of introducing significant negative induced back-EMF (electromotive force) from the large servo/motor/coils, back into the critical low level (XLR / S.E.) preamp outputs, effectively distorting the mains as well. I suspect that is one reason many folks recommend use of the high speaker level connections, as they are a much lower impedance and hence not as severely impacted. I resolved that delima by use of a sub isolator module (an option on my MSB Reference DAC). This electrically isolates the reverse induced sub noise, from the mains by a factor of 1:7. MSB offers a stand alone version, as I recall - I’m not sure if the isolation is the same as on the module.

But the point is, I now can: A) pick off the same signal for my subs, as for my mains; B) minimize group delay/latency; C) alleviate the negative effects of the back EMF; and, D) attain much more desirable LF filtering characteristics, than that observed with the alternative connectivity approach.

Regards,
V2
V2, are your Gryphon amps balanced? Also, there is a considerable problem when running one (1) REL ( which is a balanced design) from mono blocks...this is expounded upon in the REL web page that describes the various issues regarding hook-up of their subs with balanced designs, mono blocks and class D amps. The issues you describe with your SQ could well be attributed to these issues. May want to go back and check on the web page. BTW, REL does state that they do not recommend using a single one of their subs with mono block amps. Unfortunately, the solution is to have two(2) REL subs when utilizing mono blocks...are you utilizing two(2) REL subs?
 

V-Squared

New Member
Jun 9, 2017
6
0
1
#25
V2, are your Gryphon amps balanced? Also, there is a considerable problem when running one (1) REL ( which is a balanced design) from mono blocks...this is expounded upon in the REL web page that describes the various issues regarding hook-up of their subs with balanced designs, mono blocks and class D amps. The issues you describe with your SQ could well be attributed to these issues. May want to go back and check on the web page. BTW, REL does state that they do not recommend using a single one of their subs with mono block amps. Unfortunately, the solution is to have two(2) REL subs when utilizing mono blocks...are you utilizing two(2) REL subs?
Hi Davey,

Yes, I use a stereo pair of subs. Results were further enhanced by running the XLR iso sub output to a crossover with a 18dB/octave slope (Wilson Sub Controller), and then feeding the S.E. LF output to each sub.

Regards,

V2
 

Al M.

VIP/Donor
Sep 10, 2013
4,007
53
48
Greater Boston
#26
I also use the direct connectivity from preamp. With my old REL Storm III I could not hear much difference in bass quality between the two approaches (from pre-amp, lo-input, or from amps, hi-input), even though I also had tube amps at that time.

With my current pair of JL Audio subs there is only preamp connectivity, and it works perfectly. In fact, the sub integration is even better than with the my old REL. JL Audio subs have a very good reputation, which suggests that the input option from amp is not generally missed.

Davey has strong opinions about connection from the amp, as apparently does Leif. In diverse system contexts everyone has their own experiences, and while I don't doubt theirs, mine are different.
 

LL21

Active Member
Dec 26, 2010
10,589
10
38
#27
Hi LL21:

...
I had another concern with the above approach, and that was the risk of introducing significant negative induced back-EMF (electromotive force) from the large servo/motor/coils, back into the critical low level (XLR / S.E.) preamp outputs, effectively distorting the mains as well. I suspect that is one reason many folks recommend use of the high speaker level connections, as they are a much lower impedance and hence not as severely impacted. I resolved that delima by use of a sub isolator module (an option on my MSB Reference DAC). This electrically isolates the reverse induced sub noise, from the mains by a factor of 1:7. MSB offers a stand alone version, as I recall - I’m not sure if the isolation is the same as on the module.

But the point is, I now can: A) pick off the same signal for my subs, as for my mains; B) minimize group delay/latency; C) alleviate the negative effects of the back EMF; and, D) attain much more desirable LF filtering characteristics, than that observed with the alternative connectivity approach.

Regards,
V2
Thanks for that! As for back EMF, is this something i need to investigate in my own setup? I remember reading about sub-isolators from MSB, but i got the sense they were to be used when SPLITTING the output signal from a single set of outputs from a preamp...one to the main amp, one to the sub. I did ask MSB about this, and this is what they said:

"If your pre-amp has two independent outputs, it should make very little difference. Theory states that it should improve the sound, but it depends on the pre-amp design as to how much it will improve the sound. We don't have sample units for trial. You would need two of them, one for each channel."
 

spiritofmusic

Well-Known Member
Jun 13, 2013
6,510
108
63
E. England
#28
I think I’m going to pull back from the tentative idea of replacing Zu integral subs w outboard subs.
Tbh I was expecting more comments anti Class D, but there’s unanimity that for subs at least, Class D is not an issue, and indeed is best suited.
If that’s the case, then subs that are designed from the ground up in working seamlessly w the main spkrs/drivers are the ones to stick with, and this means I’m not changing the status quo.
My thoughts now turn to the other end of the spectrum, ie Townsend Maximum supertweeters, which I’m considering a no-obligation trial of. Ironically one of the main areas that these could benefit is...the bass.
Thanks for everyone’s considered input, it’s great when a thread results in no upgrade, and thus a total spend of £/$/€/¥0.00 LOL.
 

Al M.

VIP/Donor
Sep 10, 2013
4,007
53
48
Greater Boston
#29
My thoughts now turn to the other end of the spectrum, ie Townsend Maximum supertweeters, which I’m considering a no-obligation trial of. Ironically one of the main areas that these could benefit is...the bass.
That's what Alon Wolf (Magico) says, if you complain about lack of bass quality, start with the tweeter.

Thanks for everyone’s considered input, it’s great when a thread results in no upgrade, and thus a total spend of £/$/€/¥0.00 LOL.
You're very welcome. It's always great when you don't have to spend money or very little thereof.

Allows you to spend the money where it really matters.

I am still grateful to Chris Connaker (Computer Audiophile) and others for their reviews on the Schiit Yggdrasil DAC. Saved me a boat load of money that I would otherwise have spent on a very expensive DAC.

That allowed me to put my money into new speakers, amp and subs (yes, I did upgrade my bass ;)).
 

spiritofmusic

Well-Known Member
Jun 13, 2013
6,510
108
63
E. England
#30
Al, I can always rely on you for a non ambiguous opinion LOL.
 

spiritofmusic

Well-Known Member
Jun 13, 2013
6,510
108
63
E. England
#32
Sure Al. There are plenty of nuances even within entrenched positions. You and me in the same camp re streaming (ie skeptical can beat our much loved transports/dacs/cdps), but because I’m confident I’ll find a couple of hundred albums via Tidal/Roon n/a on cd or lp, I have to finally go this way sooner or later. But the decision not on SQ grounds.
Re subs, I really didn’t think the (rather limited, but still relevant) consensus would be nothing amiss w Class D on subs for music, hence I’m happy to be swayed from what may have been an unreasonably biased view in favour of only Class A/AB.
 
May 19, 2014
716
3
18
Round Rock, TX
#33
I also use the direct connectivity from preamp. With my old REL Storm III I could not hear much difference in bass quality between the two approaches (from pre-amp, lo-input, or from amps, hi-input), even though I also had tube amps at that time.

With my current pair of JL Audio subs there is only preamp connectivity, and it works perfectly. In fact, the sub integration is even better than with the my old REL. JL Audio subs have a very good reputation, which suggests that the input option from amp is not generally missed.

Davey has strong opinions about connection from the amp, as apparently does Leif. In diverse system contexts everyone has their own experiences, and while I don't doubt theirs, mine are different.
One more for preamp out (and not off the amp(s)) to the sub. I had pretty much the same situation only with 2 Rels and never looked back once moving to JL Audios. I don't buy the "flavor" of the amp theory when an amp can induce increased noise, add signal delay and may provide "sloppy" bass more so with tube amps. Think of it this way - Why would you want your signal go through two amplifiers before reaching the sub driver?
 

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