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Do I Really Need a Sub?

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Robert D

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I've been running high level connections to my Descent i for a few weeks now and loving the results (and to be honest, I haven't actually done much other than making the connections, so I can only imagine how much better it would sound once I invest the time). While I am liking what I'm hearing, one thing I'm not crazy about is the heat being generated by my Para JC-1's. You can absolutely feel the temperature change when walking in and out of the room, and it is not a small room. I only noticed this after I added my sub to my main amps. Any thoughts about whether I should worry about this configuration?
So you are running it through what Martin Logan calls 2 channel input? Using either RCA inputs from your amp/reciever or speaker level inputs from an amp?

Ive always used my depth i hooked up through the LFE from my Marantz Atmos receiver, even when using it for 2 channel music. It sounds good both ways to me. So you were using LFE and your sub did not sound nearly as good as it does now that you have it connected via the 2 channel method? How is your's connected? Do you have your's connected both LFE and 2 channel?

Maybe someone can explain why it sounds better not using LFE for stereo music.

Thanks!
 

ttocs

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I've been running high level connections to my Descent i for a few weeks now and loving the results (and to be honest, I haven't actually done much other than making the connections, so I can only imagine how much better it would sound once I invest the time). While I am liking what I'm hearing, one thing I'm not crazy about is the heat being generated by my Para JC-1's. You can absolutely feel the temperature change when walking in and out of the room, and it is not a small room. I only noticed this after I added my sub to my main amps. Any thoughts about whether I should worry about this configuration?
You need to take care to use the correct type of speaker level connection method to the amp, there are several ways to do it based on amp design. There are usually special notes when connecting one subwoofer to a differential amp and a very special note about NOT connecting two separate mono amps to one subwoofer. So it sounds like you have two amps connected to one subwoofer, is this correct?

If so, then please disconnect them immediately!

I've emailed support for three brands of subwoofers and they all said the same thing, don't connect one sub to multiple mono amplifiers using the speaker level connection method, it's not the same as connecting the Left and Right output from a single stereo amp.
 

Chops

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I've been running high level connections to my Descent i for a few weeks now and loving the results (and to be honest, I haven't actually done much other than making the connections, so I can only imagine how much better it would sound once I invest the time). While I am liking what I'm hearing, one thing I'm not crazy about is the heat being generated by my Para JC-1's. You can absolutely feel the temperature change when walking in and out of the room, and it is not a small room. I only noticed this after I added my sub to my main amps. Any thoughts about whether I should worry about this configuration?
I believe those JC-1's are fully balanced "differential" amps, meaning both positive and negative posts are hot, just that one terminal is 180 degrees out of phase from the other. You can not run them into the sub(s) via the high level inputs. You are essentially grounding out one half of the amp (shorting it out), hence why they are running hot.

Regular single ended amps it's safe because the negative terminal is grounded to chassis, same thing a subwoofer does with its high level input. The input impedance on the high level inputs on subs are so high, they are basically unseen by the amplifier and do not react any different with the sub(s) connected or disconnected, which in turn means the amps do not run any warmer than normal.

If this is the case, you need to disconnect the sub(s) from the amps ASAP before they get damaged!
 

amey01

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While I am liking what I'm hearing, one thing I'm not crazy about is the heat being generated by my Para JC-1's. You can absolutely feel the temperature change when walking in and out of the room, and it is not a small room.
The sub does not (should not??) draw any current from the amp - it is merely taking a signal from it. Therefore, if it is changing the temperature of operation, something is wrong.

If Chops is right (above), then you've he's just worked out what is wrong for you too.
 

BDH55

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So you are running it through what Martin Logan calls 2 channel input? Using either RCA inputs from your amp/reciever or speaker level inputs from an amp?

Ive always used my depth i hooked up through the LFE from my Marantz Atmos receiver, even when using it for 2 channel music. It sounds good both ways to me. So you were using LFE and your sub did not sound nearly as good as it does now that you have it connected via the 2 channel method? How is your's connected? Do you have your's connected both LFE and 2 channel?

Maybe someone can explain why it sounds better not using LFE for stereo music.

Thanks!
I ran the amp outputs to the speaker inputs on the sub (but looking at the posts following yours, that appears to be a mistake). Yes, I had my main amps running to the subs speaker inputs, and the LFE connected to my Anthem AVP. As far as using LFE for music, I should defer to the forum experts, but my understanding is LFE is a dedicated effects channel primarily for movie soundtracks.
 

BDH55

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You need to take care to use the correct type of speaker level connection method to the amp, there are several ways to do it based on amp design. There are usually special notes when connecting one subwoofer to a differential amp and a very special note about NOT connecting two separate mono amps to one subwoofer. So it sounds like you have two amps connected to one subwoofer, is this correct?

If so, then please disconnect them immediately!

I've emailed support for three brands of subwoofers and they all said the same thing, don't connect one sub to multiple mono amplifiers using the speaker level connection method, it's not the same as connecting the Left and Right output from a single stereo amp.
Yes, I had my Descent i connected to both my left and right channel mono Para JC-1's, and actually, I disconnected them a couple weeks back as while things were sounding good, I was concerned about the heat. I was thinking about reconnecting them, but thought better of it and decided to check here first, which appears to have been fortunate.
 

BDH55

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I believe those JC-1's are fully balanced "differential" amps, meaning both positive and negative posts are hot, just that one terminal is 180 degrees out of phase from the other. You can not run them into the sub(s) via the high level inputs. You are essentially grounding out one half of the amp (shorting it out), hence why they are running hot.

Regular single ended amps it's safe because the negative terminal is grounded to chassis, same thing a subwoofer does with its high level input. The input impedance on the high level inputs on subs are so high, they are basically unseen by the amplifier and do not react any different with the sub(s) connected or disconnected, which in turn means the amps do not run any warmer than normal.

If this is the case, you need to disconnect the sub(s) from the amps ASAP before they get damaged!
My bad! I didn't realize the amp design was a factor in all of this. I'd been reading about using high level amp connections and thought I would try it. In fact, Steve Guttenberg just covered this on his Audiophiliac channel (although thinking back on it, the drawing he sketched out was using a stereo amp as opposed to two mono blocks which ttocs warned me on). That's why I love this place... you guys keep me out of trouble (or at least, you try to)!

Going forward, I am planning on 'potentially' upgrading my mono blocks, and planning to move to two subs. The big questions that rise are in the future can I use speaker level connections from my left amp to my left sub and vice versa (as opposed to two mono amps to a single sub), or does this depend on the amp design? If not, then am I limited to amps that basically have a pass thru on the input so I can basically daisy chain from my preamp to my LR mono blocks and on to my LR subs? The only amps I've been looking at with that capability are either the new Para JC-1+ or the McIntosh amps.
 

Robert D

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I ran the amp outputs to the speaker inputs on the sub (but looking at the posts following yours, that appears to be a mistake). Yes, I had my main amps running to the subs speaker inputs, and the LFE connected to my Anthem AVP. As far as using LFE for music, I should defer to the forum experts, but my understanding is LFE is a dedicated effects channel primarily for movie soundtracks.
Yeah, ive heard the guys say that about LFE. When I listen to music in stereo with the LFE channel on the sub, the sub is working hard and sounds good to me. It seems to be getting all of the signal it needs.
 

ttocs

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Going forward, I am planning on 'potentially' upgrading my mono blocks, and planning to move to two subs. The big questions that rise are in the future can I use speaker level connections from my left amp to my left sub and vice versa (as opposed to two mono amps to a single sub), or does this depend on the amp design? If not, then am I limited to amps that basically have a pass thru on the input so I can basically daisy chain from my preamp to my LR mono blocks and on to my LR subs? The only amps I've been looking at with that capability are either the new Para JC-1+ or the McIntosh amps.
Using the speaker level connection between amp and subwoofer can be done from any amp to a subwoofer that is capable of such connection. However, the wires used will vary with amp design. One connection is done using one or both "hot" wires connected to the amp along with the ground depending on the amp's output level vs the sub's input level, another leaves the ground wire "floating" if the amp is differential. There are other considerations, so it's easier if you go to rel.net and lookup what they recommend for connections which is pretty much universal between the sub brands I've used.

With my Krell I had to use only one hot wire, leave the ground floating, and the ground was provided with the RCA cable from the preamp's output and LFE Input on the subwoofer. The floating ground method is not only for differential amps, I had to float the ground with my tube amps or the hum was massive.
 

Brad225

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I had a number of communications with ML tech support yesterday and today regarding connections with subs.

They say that it is not an issue having both balanced amps connected to their respective speaker binding posts on their subs. Their reasoning is that the negative signal is never connected to earth ground in the design.

I asked if the left and right negative speaker wires are combined anywhere in the sub and their response was, Yes but it would have no effect on the amps. I was told this came from Joe Vojtko.
Still puzzling how you can connect the negative wires and not have an issue.

I have used ARC balanced amps wired to subs this way for 15 years and have never had an issue that I know of.

If I can't find a schematic for the Depth i my EE friend and I will open one of them up and take a look at how they are wired. He is having a total knee replacement on Monday so it won't be for a few weeks.
 

BDH55

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Yeah, ive heard the guys say that about LFE. When I listen to music in stereo with the LFE channel on the sub, the sub is working hard and sounds good to me. It seems to be getting all of the signal it needs.
I found the info I was looking for about the LFE channel at the Soundoctor site (not 100% sure, but I think it was chops that originally posted this). I may be wrong but if LFE is a dedicated channel primarily for film soundtracks, then my 'guess' (and that's all it is) is that an LFE channel likely doesn't exist with most two channel music sources. I'm way out of my league on this and we really need to hear from the gurus out here.
 

BDH55

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Using the speaker level connection between amp and subwoofer can be done from any amp to a subwoofer that is capable of such connection. However, the wires used will vary with amp design. One connection is done using one or both "hot" wires connected to the amp along with the ground depending on the amp's output level vs the sub's input level, another leaves the ground wire "floating" if the amp is differential. There are other considerations, so it's easier if you go to rel.net and lookup what they recommend for connections which is pretty much universal between the sub brands I've used.

With my Krell I had to use only one hot wire, leave the ground floating, and the ground was provided with the RCA cable from the preamp's output and LFE Input on the subwoofer. The floating ground method is not only for differential amps, I had to float the ground with my tube amps or the hum was massive.
While this is very helpful, I'm trying to get my head around five decades of red to red, and black to black connections! It seems really odd to me that I could just run one hot wire... I meant to tag Parasound today but got distracted by darn doctors appointments! I will definitely check out the REL site...
 

BDH55

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I had a number of communications with ML tech support yesterday and today regarding connections with subs.

They say that it is not an issue having both balanced amps connected to their respective speaker binding posts on their subs. Their reasoning is that the negative signal is never connected to earth ground in the design.

I asked if the left and right negative speaker wires are combined anywhere in the sub and their response was, Yes but it would have no effect on the amps. I was told this came from Joe Vojtko.
Still puzzling how you can connect the negative wires and not have an issue.

I have used ARC balanced amps wired to subs this way for 15 years and have never had an issue that I know of.

If I can't find a schematic for the Depth i my EE friend and I will open one of them up and take a look at how they are wired. He is having a total knee replacement on Monday so it won't be for a few weeks.
Okay, thx Brad. One thing I thought about is while my amps were running surprisingly hot, they also have thermal protection which never kicked in... so apparently, they weren't really under any stress. That said, I don't want to run them to the limits either. Since I am looking at both new amps, and going to two subs, I want to wire this right...
 

ttocs

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I found the info I was looking for about the LFE channel at the Soundoctor site (not 100% sure, but I think it was chops that originally posted this). I may be wrong but if LFE is a dedicated channel primarily for film soundtracks, then my 'guess' (and that's all it is) is that an LFE channel likely doesn't exist with most two channel music sources. I'm way out of my league on this and we really need to hear from the gurus out here.
It's easy to track which audio will have LFE. Any audio denoted as x.1 has LFE content. So that would include 2.1, 5.1, etc. The .1 is always the LFE Channel. 2.0 doesn't have an LFE channel.

Just remember that LFE stands for Low Frequency Effects channel. As an experiment to find out how what is actually in the LFE channel, I've listened to LFE Only, and it's quite interesting. The way to do this is to setup one of the subwoofer channels to LFE ONLY. Not all processors are capable of doing this.

Also keep in mind that the LFE Input on a sub really isn't only for LFE. On my Sumiko and Rel subs, if the Speaker Level Input is being used and I want to also use the subs for LFE then I need to use the LFE Input on the subs to get the .1 channel and NOT the Line Level Input. Speaker Level and Line Level BOTH go through the Crossover Setting on the subs, which is why both of these inputs cannot be used concurrently, just one or the other - so it's either the Speaker Level coming from the L&R Amps or the Line Level coming from a preamp or processor. The LFE Input has no crossover setting on the sub because the processor controls the crossover setting for all speakers set to Small as well as sending LFE if that's how it's setup. So just to recap: The Line Level Input can be used concurrent with the LFE Input, or, the Speaker Level Input can be used concurrent with the LFE Input.

The way my system is setup, I currently am using the subwoofers for LFE only, and send all Bass Management (speakers set to Small) to my Front Left & Right Main Speakers set as Large. When I first did this I was kinda shocked at how much better the Surround channels sounded when the bass for those speakers didn't have to come from the same drivers that were being used for LFE. If I wanted to, I could connect the subs such that one sub channel is only for LFE and the other two sub channels are for Bass Management instead of the Front L&R, best of all worlds IMO, and I may get more subs just for this purpose in the future.
 

ttocs

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While this is very helpful, I'm trying to get my head around five decades of red to red, and black to black connections! It seems really odd to me that I could just run one hot wire... I meant to tag Parasound today but got distracted by darn doctors appointments! I will definitely check out the REL site...
Yeah, it's confusing for sure.

When I was using my Krell for Front Left & Right, AND, connecting the subs using the Speaker Level connection method, I had to also connect an RCA cable from an unused RCA connection on the processor to the LFE Input on the subs to get the ground connection completed - even though I wasn't using those subs for LFE. It "can" work without this, but it just depends on how your system is wired up INCLUDING the power cables and components. Just think "ground LOOP hum". Ground is ground is ground, right? Maybe. It gets into the weeds really quick, lots written about it, all of which is confusing.

Full disclosure, I'm not using subs for my Fronts. I experiment from time to time, but keep liking music better without the subs. But my past experience doesn't stop my desire for future attempts as my system evolves. Since a major overhaul of tweaking my subs a few weeks ago and getting some great results, there is another attempt to be made in the near future which, unfortunately, will not include being able to use the Speaker Level Inputs due to the configuration of the three subs working as one.

I'd say listen to ML and Parasound. They can guide you on what's appropriate for your system.
 

Robert D

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I found the info I was looking for about the LFE channel at the Soundoctor site (not 100% sure, but I think it was chops that originally posted this). I may be wrong but if LFE is a dedicated channel primarily for film soundtracks, then my 'guess' (and that's all it is) is that an LFE channel likely doesn't exist with most two channel music sources. I'm way out of my league on this and we really need to hear from the gurus out here.
Yeah, thats how it seems in theory but when I use my setup for stereo music the sub is jamming!
 

Chops

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When I was using my Krell for Front Left & Right, AND, connecting the subs using the Speaker Level connection method, I had to also connect an RCA cable from an unused RCA connection on the processor to the LFE Input on the subs to get the ground connection completed - even though I wasn't using those subs for LFE. It "can" work without this, but it just depends on how your system is wired up INCLUDING the power cables and components. Just think "ground LOOP hum". Ground is ground is ground, right? Maybe. It gets into the weeds really quick, lots written about it, all of which is confusing.
This is good news and I see how it can work. It makes perfect sense.

I kind of thought this style of hookup would work, but didn't want to just assume things and post it without first doing some research.

Two more things...

1) Not all subs have a ground lift feature, so didn't want to really mention that either.
2) I just wanted to reiterate that the LFE input does not pass through the sub's crossover, so putting a fullrange signal to the LFE input, you would be getting a lot out unwanted sound out of your sub, upwards of 500 Hz or more depending of the upper limit frequency of the internal amp and driver in the sub.
 

BDH55

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Following ttocs suggestion I spent a couple hours up on the REL site working through all their configuration examples. Very helpful, and I actually feel like I am starting to get a grip on the different wiring options. I couldn't find anything in my JC-1 manual or on the Para website that would clear up the issue about whether they are a differential amp or not, so I'll call them on Monday.
Full disclosure, I'm not using subs for my Fronts. I experiment from time to time, but keep liking music better without the subs. But my past experience doesn't stop my desire for future attempts as my system evolves. Since a major overhaul of tweaking my subs a few weeks ago and getting some great results, there is another attempt to be made in the near future which, unfortunately, will not include being able to use the Speaker Level Inputs due to the configuration of the three subs working as one.
I'm specifically looking at bringing two subs in for my front channels. When I am listening to two channel music, my sources run thru my Para JC-2 BP preamp only. When I am watching any type of video, those sources run thru my Anthem AVM 60, which feeds the FR and FL outputs thru the JC 2 BP using its' bypass function. Sooo, my goal is to have the subs hanging off my main amps with their high level connection which should put them in play for both two channel, and video sources. Of course in addition to the high level connections, I will also be running the LFE connections between the subs and my AVM 60 processor. I sure hope I don't go to all this effort (and expense) only to find out like you did that maybe I will also prefer my front speakers without the subs... but if so, I'll just re-wire them to run off my AVP for my home theater.

The other thing that time on the REL site did for me is to get me thinking more about potentially going with a dedicated sub company like REL as opposed to my original plan of using ML. Also, this is getting really expensive as I started this thread wondering if I really needed a sub??? Everyone convinced me that yes, I did need a sub... then, it was that I would be better with a pair of subs... and after spending time on the REL site today reading about their REL 3D home theater, now I am going to potentially need three subs!!!
 

Chops

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Parasound certainly doesn't make it easy or clear about the true design of those JC-1 amps. That's for sure. When I wrote what I said earlier, I was purely going off of speculation, because that's the only thing I can think of as to why the amps are running hot connected to the subs.

As for whether or not to go with one sub or two, that's up to you and how much you want to ultimately spend. If you're patient and don't mind doing a bunch of trial and error with tweaking and tuning of a single sub (position, etc, etc), you can get a single sub to sound great. Though as I've said before, going with dual subs will yield even better results in the end.

As far as going with a dedicated company such as REL, JL Audio, Rhythmic, or sticking with ML, I would lean more towards the dedicated company. I have no experience with ML subs, but to me they all seem to be geared more to HT use than anything else. Not that that's a bad thing, but they might not be the absolute best choice for music. Rhythmic would be your best choice for both musicality and bang for buck factor with their servo technology. Next would be JL Audio, with REL being the most expensive of the group. All great subs, but again, just a matter of how much you want to spend.
 

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Quick update...I sent a note to Martin Logan, Parasound, and REL about what I was trying to accomplish, and the challenges I ran into on Sunday afternoon. I heard back from Parasound (Richard Schram BTW), and I heard back from REL yesterday. So far nothing from ML which is really disappointing. I know they are struggling with C19, but isn't everyone?
 
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