I'm having issues connecting my REL Carbon limited subwoofer to my Jeff Rowland 625 S2 amplifier via the high-level input. I connected my sub according to REL's instructions...yellow lead to positive on one channel, red lead to positive on the other channel, and floating the black wire(ground). I get minimum output when connected according to the instructions. When I use the low level input, the output is sufficient and the sub sounds great. Per my conversation with Jeff Rowland I need to ground the black wire by loosening a screw on the amplifier and connecting the black wire, but if it isn't properly grounded I may damage my amplifier. Is there anyone that owns a REL with Jeff Rowland 625 S2 amplifier or other balanced differential amplifier? If so, how do you connect your REL via the high-level input. Is there an easier way to ground the wire than unscrewing the screw on my amplifier. I just don't want to unscrew the screw and prefer another method of grounding the sub.
I ran into similar situation recently where I could not connect REL’s to my custom 300B amps. Since they were custom made, I was able to sent back the amps to have outputs properly wired for ground reference. The manufacturer also sending me a pair of speaker to line level converters as a back up. I am expecting everything later this week.
PM me on Saturday if you would like to try the speaker to line level converters and I will be happy to send them over.
I suspect the reason floating the ground wire doesn’t work in this case is that the inputs of your amp are transformer coupled, so a ground path is not established between the sub and the amp via the preamp, since the preamp’s ground is isolated from the amp’s ground via those transformers. If the grounds of the amp and preamp were not isolated, as is usually the case with most other designs, a ground path having reasonably low impedance would be established between the sub and the amp via the preamp-to-amp interconnections in combination with the AC safety ground wiring of the preamp and the sub.
For the same reason connecting the black wire to a ground point on the preamp would presumably not work either.
While Lalit has very graciously offered to let you try the speaker-to-line level converters he will be receiving, I don’t think it would be safe to use them with your particular amp. I would envision that most such converters would attenuate the level that is provided to their signal input, but would route the ground that is provided to their input directly to their output. Since your balanced amp has full-amplitude signals on both its + and - output terminals (rather than the amp’s - output terminals being connected to its circuit ground), the result of routing both output channels of your amp through such converters to the left and right channel RCA input connectors of a single sub would almost certainly be that the full amplitude signals on the negative output terminals of the two channels are shorted together by the sub’s internal ground. Definitely a no no.
Given that the amp does not provide RCA input connectors, or any other circuit ground connector, the one **possible** alternative I can envision to attaching the sub’s black wire to a chassis screw, as Jeff suggested, would be to solder the black wire to the ground shell of a 1/8 inch mini-plug, while leaving the signal pin(s) of that plug unconnected, and inserting that plug into the amp’s remote on/off jack.
This assumes three things, though:
1) It assumes that the ground shell of the remote on/off jack is internally connected to the amp’s circuit ground. You would need to confirm that with Jeff.
2) I suspect that it wouldn’t matter whether the mini-plug is a stereo type or a mono type. Again, though, that should be confirmed with Jeff.
3) It assumes that you presently have nothing connected to the remote on/off jack. Although if you are presently using it you could probably solder the sub’s black wire to the ground shell of the plug that is being used, if assumption (1) is confirmed by Jeff.
As always thanks so much for your response. Your post highlights my concern. If I don't ground it properly I will damage my amplifier and/or sub. Like I've already stated, is does work via the low level input, but I'm wondering if it will sound better via the high-level input. For sake of comparison, if the high-level connection is a 100 for sound, what is the low-level connection, 80, 90, 95? I'm not concerned if there's only a slight difference in sound between the two inputs; however if there's a significant difference than I would like to find a way to safely connect through the high-level input.
I am quite surprised that REL unable to help or provide amicable solution. They were extremely helpful when I contacted them about high level connectivity with my ARC amp.
For sake of comparison, if the high-level connection is a 100 for sound, what is the low-level connection, 80, 90, 95?
Your guess is as good as mine on that question, Richard. As I’m sure you’ve seen, REL recommends using speaker-level connections where possible, their rationale being that the signals received by the sub and the main speakers will then both reflect the sonics of the power amp. Although over the years I’ve seen at least one or two members here having extensive experience with subs express disagreement with that philosophy.
Personally I don’t use a sub, and I have no particular opinion concerning that rationale. And in any event I would expect the degree of difference that would occur between the two connection approaches to be significantly system dependent. The more accurate/neutral the amplifier’s sonics are, the less difference there would presumably be between the two approaches. Assuming, that is, that the preamp is capable of driving the relatively low input impedance that most subs have at line-level without issue, while simultaneously driving the power amp.
I own a JR model 8T. I had the same type of issues as you. Having contacted REL, I was told to hook up the system essentially the same way, yellow on the positive left, red on the positive right and the black to the negative ( neutral) of the red channel. This seemed to be ok. However, after I had my amp modded by Jeff, I asked him about this and he suggested that we add a ground connection at the chassis of the amp...which he did. I now utilize the ground connection for black, and the red to right, yellow to left. You might want to send your amp back to Jeff for him to do the same thing. Not sure I would want to loosen a screw of the chassis as Jeff suggests. Nonetheless, I think Almarg's advice is also correct.
I'm just so surprised that the compatibility problem between REL and Jeff Rowland amplifiers and other balanced differential amplifiers isn't well documented.
lalitk, Thanks so much for your assistance.
daveyf, "
Not sure I would want to loosen a screw of the chassis as Jeff suggests." I know it sounds trivial to some, but I couldn't agree more and I'm not going to loosen any screw. I may contact Jeff Rowland and ask about adding a ground connection on the chassis.
@ricred1 I’m not so sure that the compatibility issue with REL subs and balanced differential amps isn’t well documented. There are quite a few posts on this forum and others about the issue. REL themselves now has a helpful video on their web site about hook up protocol. I run dual REL subs with my Jadis mono blocks, there were also some issues to hooking up those as well. I ended up having two connector cables custom made by Signal cable. Took me months to get the blend correct, and last night I noticed that my left subwoofer seems to put out a lot less output than my right...not sure why this is the case, but more experimenting to find out what’s going on. Sometimes these subs can be a royal PITA.
Although I'm frustrated with the inability to at least try the high-level input, I ordered a second REL Carbon limited that I should have on Monday. The addition of a single REL has increased my enjoyment of my 2-channel system; so I figure dual subs will be better. I reached out to REL again today in hopes that someone can provide a simple way to use the high-level input without damaging my amplifier or sub. Hopefully someone from REL will contact me tomorrow.
In the past whenever I have contacted REL, i have done so via e.mail. They have always responded fairly quickly to all of my inquiries and questions.
The addition of another REL should give you a nice boost in SQ, albeit with a lot more set up time involved and experimentation in positioning, x-over, and volume settings in order to get the blend to be invisible. It took me almost two months to get it right...and I am still making very minor adjustments even now!! Two subs are more than twice as difficult to dial in than just one...BUT the effort will be worth it.
As a point of information, for a great many years prior to the introduction of many of their current models, REL manuals recommended that when connecting to amplifiers whose outputs are balanced or bridged that the black wire be connected to a chassis screw.
That should have and apparently did work well in most cases, although not quite all. An exception being a few amplifier designs in which chassis and circuit ground are completely isolated, in which case the result of doing that would probably be a large hum. Another special case involved some long obsolete early class D designs which had very high DC voltages (something like 24 VDC if I recall correctly) on both their plus and minus output terminals, relative to ground, and therefore required blocking capacitors between the amp outputs and the sub.
I don’t know what the reason may have been for REL to abandon that long-standing recommendation of using a chassis screw when connecting to balanced or bridged amplifier outputs, and now recommending that the black wire be floated.
Yes, I would think that to be highly likely. Given what Jeff has told you, given that REL's recommendation has up until recently been to do that, and given my technical understanding of the situation.
I just received a call from REL. They said I could ground the sub/amp by going from the REL's LFE to my Rowland Corus preamp while leaving the black lead floating.
@ricred1 So, REL are suggesting that you run a ic from your LFE on the sub to your preamp? I guess that would ground the sub, but I wonder if you also wouldn't potentially create a ground loop? As I stated before, the ground connection that Jeff added for me on the back of my amp is the way I would think is the most effective way to get this accomplished.
I just received a call from REL. They said I could ground the sub/amp by going from the REL’s LFE to my Rowland Corus preamp while leaving the black lead floating.
Not sure that the REL person is realizing that the inputs of your amp are transformer coupled, and the amp’s descriptions at the JRDG website and in the manual state that "transformer coupled input circuitry provides universal component compatibility and virtually eliminates ground loop noise..."
So it seems to me that due to the isolation the input transformers presumably provide it is likely that connecting the sub’s ground to the preamp’s ground, via the LFE or whatever, will not result in an effective connection between the sub’s ground and the amp’s ground, which is what matters. On the other hand, though, I suppose it is possible that an adequate ground path between the sub and the amp could be formed via that connection in conjunction with the AC safety ground wires in the power cords of the preamp and the amp, which ultimately connect the chassis of the preamp and the amp together.
In any event, given that none of us have much familiarity with how grounds are handled internally in these designs it’s worth a try. And I don’t think it could do any harm to give it a try; just be alert to the possibility of a loud hum. IOW keep the sub’s level control at a low setting when you begin the experiment.
I should have mentioned at the beginning the most frustrating thing about this situation is my dealer is a REL and Rowland dealer. He has the ability to connect the REL to the exact amp and preamp that I have, but he won't. When I told him about my situation, he said that he would connect the REL to the Rowland 625 S2, but to date he hasn't.
The other frustrating thing is trying to find out the truth regarding the sound quality difference between the high-level and low-level input. During a telephone conversation two days ago a REL representative told me there wasn't a difference in sound quality between the two inputs, but the high-level input helps facilitate a better blend between the sub and speakers. Yesterday, a different REL representative sent me this via email...
Low level input is about 80% of the high level input. If both inputs offered the same sound quality I wouldn't worry about the high-level input anymore.
@ricred1 I think the blend is where it’s all at. The fact that the subs take their signal directly from the amp in the high level set up is what has distinguished REL’s for me over the years. REL used to claim that this was allowing the sub to more carefully track the signal at the amp end, not sure if they still claim that anymore. Your dealer is possibly wondering how to connect the sub ground wire to the amp chassis...as unlike many other amp manufacturers, Jeff chooses not to include a separate ground connector on his chassis. If you look at Lamm, Pass and others they do include this. Nonetheless, as I said before, Jeff is willing to add this necessity ( which I believe it really is) to your chassis.
I have been corresponding with Justin Magana who is REL’s Chief Engineer. Based on his advice I twisted the red and yellow wires together and connected my REL via the high-level input. The black wire is floated. It worked! I have plenty of output from the sub and absolutely zero hum.
So are you saying, then, that the only difference between what worked and what previously didn’t work was twisting the red and yellow wires together, while having exactly the same connections in both cases? If so, I have no idea how to account for that.
Or are you saying that the red and yellow wires are now connected to the same positive output terminal of the amp, while you wait for the second sub to arrive which will be connected to the positive output terminal of the other channel? If so, it would still be hard to explain why you were previously not getting proper results, with the red and yellow wires having been connected to the positive output terminals of different channels. But it would suggest that previously the outputs of the two channels were somehow being subtracted from each other rather than summed. In other words, a polarity inversion was somehow being introduced on one channel, either in the sub or the amp or in one of the connections between the two. Or perhaps as a result of a miswire in one of the XLR cables upstream of the amp, such that pins 2 and 3 are interchanged at one end of one cable. Although most of those possibilities (aside from an issue within the sub or in its connections to the amp) would have had dramatic negative effects on what you were hearing from the main speakers.
Al, "So are you saying, then, that the only difference between what worked and what previously didn’t work was twisting the red and yellow wires together, while having exactly the same connections in both cases?" YES
"Or are you saying that the red and yellow wires are now connected to the same positive output terminal of the amp, while you wait for the second sub to arrive which will be connected to the positive output terminal of the other channel?" YES, per my conversation with Justin that's the way I have to connect dual REL subs anyway; therefore there wasn't any risk in connecting the single sub this way. He assured me nothing bad would happen, so I tried it.
"Ricred what sub are you upgrading from and what improvements are you hearing with the Carbon limited? I have an S5 SHO." I had a JL Audio F112 v2. The REL Carbon Limited totally disappears compared to the JL Audio F112 v2. I'll make more comments in a couple of days.
@ ricred1 that’s why I asked if your amp was class d. I knew that had been an issue. As you know I’m a huge fan of rel subs. I think they are the best. I hope you can get the connection you need.
@ricred1 By summing the red and yellow wires together and using the black wire to negative you are only getting the signal from one channel of your amp. This is the way that I connect my dual subs...one per channel! But if you connect just one sub in this manner, you are only getting the information from the channel that you have connected to. IOW, a mono signal to the sub in question. This doesn't actually solve your problem if you want to use just one sub and have it run off both sides (l,r) of the stereo amp. ( or left/right mono blocks).
The black wire is floated and not connected to anything. I'll have dual subs and will receive the 2nd sub on Tuesday. That's why I was advised to connect my single sub this way.
@ricred1 If you are not connecting the black wire, I would be concerned that you are not grounding the sub. I connect my subs with the red and yellow summed to the red output per amp and the black to the black output per amp. This is with dual subs and mono blocks. I’m pretty sure that way they are each getting a mono signal....left to the left sub and right to the right sub. The way you are describing your connection would indicate that you are only getting the mono signal from one of your amps to the sub...and not the summed stereo signal.
Ricred 9-22-2019 Al, "So are you saying, then, that the only difference between what worked and what previously didn’t work was twisting the red and yellow wires together, while having exactly the same connections in both cases?" YES
I believe the answer to this question is actually "No," since when you initially reported the problem you were connecting the two wires to different channels, while in the case of the good results you have just obtained both wires are connected to the same channel. So the connections were different when you had the problem vs. when you did not have the problem. From your OP:
Ricred 9-17-2019 I connected my sub according to REL’s instructions...yellow lead to positive on one channel, red lead to positive on the other channel, and floating the black wire(ground). I get minimum output when connected according to the instructions.
Regarding grounding, the ground path/signal return path between the sub and the amp that presently exists, which is providing the good results you have obtained, is as follows:
From the circuit ground within the sub via some unknown but presumably low impedance within the sub that connects its circuit ground to its AC safety ground, then via the safety ground wire in the sub’s power cord to the AC outlet, then from the AC outlet via the safety ground wire in the amp’s power cord to the amp’s chassis, then via some unknown but presumably low impedance with the amp that connects the amp’s chassis to its circuit ground.
As I alluded to earlier, that path may serve as an adequate ground/signal return path with some and perhaps most designs, depending on the internal grounding configurations of the particular amp and sub. And given that REL recommended doing that, and that the results are good, I would leave well enough alone. Just don’t ever put a cheater plug on the power cord of either the sub or the amp, which would interrupt that path!!
So as things stand now I believe the mystery that remains is why with that same ground path you had the problem in the first place, when connecting the red and yellow wires to different channels. The only explanations I can think of, both of which appear to be very unlikely, are:
(a)You inadvertently connected one of the two wires to a negative output terminal of one channel of the amp, while connecting the other wire to the positive output terminal of the other channel. That would cause the signals from the two channels to be subtracted from each other, rather than added.
(b)Something is wrong with a component or cable.
As I say, both explanations seem very unlikely, so I’m at a loss to explain why you had the problem in the first place.
Daveyf 9-22-2019 I connect my subs with the red and yellow summed to the red output per amp and the black to the black output per amp. This is with dual subs and mono blocks.
In the case of an amp having balanced outputs, such as Ricred’s, the black wire from the sub should absolutely not be connected to a negative output terminal of the amp. Doing so would cause the full amplitude signal that is present on that output terminal of the amp to be connected to the sub’s ground. Depending on the internal grounding configurations of the amp and the sub (and more specifically on the impedance through which their circuit grounds are internally connected to their chassis/AC safety grounds) doing so might work, but is very poor practice at best and could very conceivably cause damage at worst. If the outputs of your 8T are balanced (or bridged) that would presumably be the reason Mr. Rowland recommended installing a ground terminal on it.
Over the years I’ve seen a number of members here mention that they connect the black wire of a REL sub to the negative output terminal of a fully balanced amp, and the results seem good. To that I say they should count their blessings :-)
“Over the years I’ve seen a number of members here mention that they connect the black wire of a REL sub to the negative output terminal of a fully balanced amp, and the results seem good. To that I say they should count their blessings :-)”
@almarg,
Not sure what do mean when you say ‘count their blessings’...is it a cautionary smiley at the end?
I own dual mono SET amps and after consulting with REL and amp manufacturer, I also connected red/yellow wire to positive output and black wire to negative output of the terminal. Like Daveyf, I am also using dual subs. The Input Impedance of each mono is 100 kOhm.
Given that the amps you referred to are SETs they do not have balanced or bridged outputs, so connecting your subs as you have described is perfectly fine.
My statement about counting their blessings referred to what I had said just before that, meaning that those who have connected the black wire to the negative output terminal of a fully balanced (or bridged) amp should feel lucky that (a) it worked ok, and (b) damage didn’t result. As I said, which of those eventualities occurs, in the case of an amp having balanced or bridged outputs, will depend on the internal grounding configurations of the particular sub and amp.
I also experimented (skeptics at first) with non-grounded power cords for all of my components except preamp to eliminate any ground loop or hum issues. The results were shockingly good, my system is dead quite now...the interconnects from preamp provides static dissipation through the secondary ground connection & neutral thus eliminating any ground loop caused by interconnection of electrical equipments having multiple paths to the ground.
daveyf, "If you are not connecting the black wire, I would be concerned that you are not grounding the sub." If it wasn't properly grounded I'm assuming I would hear a hum? I assume REL's Chief Engineer wouldn't tell me to do something that would damage my amp or sub.
Al, I initially connected the red wire to the right positive channel and the yellow to the left positive channel, with the black wire floated. Now I have it connected to the right positive channel, but the black is still floated. I was told that if I don't hear a hum, the amp and sub are properly grounded and I won't have any issues.
@ricred1 Al’s comment above about the balanced aspect of your amp is correct. I use both a balanced output amp ( the Rowland) and a non-balanced mono amp ( Jadis), The points that Al brought up are 100% correct with the balanced design. Nonetheless, I think you are not hearing the sub in a way that would be beneficial with the set up you now describe. The sub is only receiving the mono signal from the left ( or right, depending on which mono block you use) channel. Quick question for Al, if I were to hook up my two (2) subs to my Rowland stereo amp, would I actually utilize the summed red and yellow cables for each left and right connector and the black cable ( now two) for the ground connector ( that Jeff installed)....or leave those disconnected entirely? ( like what ricred 1 is doing).
Are you suggesting that there's no benefit to connecting DUAL REL subs, one to the left channel and the other to the right channel, with the red and yellow wire connected to the positive speaker post on each and the black wire floating?
Quick question for Al, if I were to hook up my two (2) subs to my Rowland stereo amp, would I actually utilize the summed red and yellow cables for each left and right connector and the black cable ( now two) for the ground connector ( that Jeff installed)....or leave those disconnected entirely? ( like what ricred 1 is doing).
@daveyf Connecting the black wire of both subs to the ground connector on the amp seems to me to be an ideal approach. While two ground paths/signal return paths will then exist between each of your subs and the amp (one via connection of the black wire to the ground connector, and one via the convoluted path I described earlier involving the AC safety grounds), the presumably much lower impedance of the direct path to the ground connector will result in nearly all of the signal return currents utilizing that path.
That said, regarding Richard’s situation, when he receives the second sub he has ordered, and he has the red and yellow wires from one sub connected to the + output of one channel of his amp, and he has the red and yellow wires from the other sub connected to the + output of the other channel of his amp, with the black wires of both subs unconnected, based on his latest findings with one sub it appears likely that he will have fine results. So while having a ground terminal installed on his amp is theoretically preferable, if he were to do that my guess (and it’s just a guess) is that the resulting sonic benefit would fall somewhere between minimal and none.
Al, If leaving the black wire floating was an issue, wouldn’t I hear a hum, reduction in output, or some sonic indicators that something is wrong? I don’t understand the issue with how I have it connected? This is directly from REL's Chief Engineer: What I would do first, is combine the RED/ YELLOW wires of the REL you have now to one channel and see how that works. When you get the second REL, you would have to do this anyway, because you want to dedicate one REL to each channel.
What I was saying at the end of my previous post is that most likely there is no issue with leaving the black wire (and eventually wires plural) unconnected, at least in your situation.
And even if there is an issue (which I suspect there isn't, given that there is no hum), at most the consequence would be some very minor (and unpredictable) sonic effect.
Richard, I am not suggesting that having two subs is a negative issue. In fact, I believe that two subs is quite beneficial. The second sub allows one to not only have a sub dedicated for each channel, but also seems to help in taming various room modes. OTOH, setting up two subs is far more involved and time consuming than just setting up one. IME.
@almarg Thanks Al, I might at sometime in the future hook up my two subs to my Rowland. I am currently only using this configuration ( twin subs) with my mono blocks..and using just one of the subs when I play the Rowland.
I would also like to say thanks to astewart8944. He was the first person to suggest connecting both wires to the same positive terminal and floating the black wire.
My thoughts comparing the JL Audio F112 v2 to the REL Carbon Limited in my system/room. This has nothing to do with sound, but the JL Audio F112 v2 is built like a tank and is packaged significantly better than the REL. My initial thoughts on REL vs JL Audio, comparing a single Carbon Limited to a single JL Audio F112 v2. The REL has more affect on the mids and highs than JL Audio. The mids and highs have more detail with the REL. I think JL goes a little deeper, but doesn't allow you to hear the different shades of low level information like REL. You can feel the JL a little more, but it doesn't provide the nuance of the REL. The REL totally disappears, but no matter what I did with the JL Audio I could tell it was there. I choose the JL Audio F112 v2 for a HT only system. For music only I choose the REL Carbon Limited. My system is a combination of 2-channel and HT. I listen to music 80% of the time, so I prefer the REL for my situation. If it was 50/50 or 80% HT I prefer JL Audio, because it has more bass impact. For now the REL is located in the same spot as the JL Audio was. I'll pickup my 2nd REL from FedEx today and start the process of dialing in both subs.
@ricred1 Richard, what made you pick the Carbon Limited vs one of the other REL Subs. The new S series seems to be where they are concentrating their line. The Carbon series isn't even on their web page, unless you do a specific search. Seems like they don't want to push that model.
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