Subs for 2.1 Music

[Krocdoc]

With the sale prices on the old series of subs I want to add a sub or two to my system. Question is whether (2) 700’s or (1) 1000. Will be paired up with esl-9’s.

 

[JonFo]

Two well placed subs, even if of lesser capabilities, will usually outperform a single better unit thanks to the benefits of room coupling and fewer modal cancellations/peaks. Four is even better.

Research has shown that in a rectangular enclosed room, placing one sub mid-way between the walls in the front of the room and the other symmetrically on the rear wall (also centered) is the optimal deployment for two subs.
Do NOT do what one sees so much in systems pics and place the subs nice an evenly next to the mains. That's generally a bad place for them, and negates the benefit of being able to locate subs where they will couple well to the room.

I used 4 very low-end models (Dynamo 300 IIRC) in a tiny media room and the bass evenness is always surprising and very effective. I explain further the rationale in this thread: http://www.martinloganowners.com/forum/showthread.php?17591-Media-room-%96-quad-ML-sub-setup

 

[twich54]

Yep, as usual Jonathan nailed it (again) !

 

[MOON]

Jonathan,

Totally agree on the two subs. I do have a question for you. I run 2 depth i's with my Odyssey's and can't post on them as you suggest. They are just over 6 feet off the front wall off to the front sides of the oddysey's something like you discribed.

Would I be better off to have the one sub the same just over six feet out from the back wall on the other side so they are at opposite sides of the room?

One more question. I have the subs running from the pre out using both left and right rca's to the first sub , with two rca's going from the 1st sub to the second sub. It'a lot of cable to go from the 1st sub all the way around to the other side of the room to the 2nd sub.

Is there a better way to run the wires, or differently for better results ?

 

[JonFo]

... One more question. I have the subs running from the pre out using both left and right rca's to the first sub , with two rca's going from the 1st sub to the second sub. It'a lot of cable to go from the 1st sub all the way around to the other side of the room to the 2nd sub.

Is there a better way to run the wires, or differently for better results ?

Hi Moon, tackling this part first, as it sounds like there might be some miswiring even with the current physical setup.

What is the preamp? Does it do bass management between the mains and the subs? Does it have a Sub-out?

Your current wiring makes it look like not, and you are feeding the full-range pre-amp output L/R into the first Depth i's L/R input and using the Depth Crossover settings to low-pass the Sub signal. If so, the L/R output of the first Depth should be going to the amplifiers input to ensure it gets the high-passed signal after the crossover.
But it sounds like you are using that to feed the L/R inputs of the second depth, right? That's not right if so. You should be using the single sub out on the first depth to feed the LFE in of the second Depth, as the first Depth is the one doing the crossover duties and the second is just a slave to the low-pass signal output on the first subs Sub Out connection.

So please answer the above and maybe even sketch the current system wiring scheme (hand-drawn and a cell phone pic is fine) and we can take it from there.

 

[JonFo]

... You should be using the single sub out on the first depth to feed the LFE in of the second Depth, as the first Depth is the one doing the crossover duties and the second is just a slave to the low-pass signal output on the first subs Sub Out connection.
...

Actually, it depends on the implementation in the Depth. The manual is not 100% clear on whether the Sub out includes the output of the low-pass crossover. As on page 23 it claims "RCA Sub Out (all inputs summed)" in which case, it still needs a crossover in the second Depth, in which case you would connect it to the Left input, and set crossover settings identical to the first depth as a starting point. You will be tweaking phase (delay) for best blend.

Any Depth owners that can clarify based on actual implementation?

 

[Brad225]

I run 4 Depth I subs center of the wall front, back and both sides. Left and Right RCA cables from the Preamp line level out to 1 front and 1 side Depth. Then 1 RCA from the combined output to either L or Right line level on the other 2 Depth's.

L & R > R Side sub > combined signal > L or R of Front sub.

L & R > Rear sub > combined signal > L or R of L Side sub.

This sends the line level signal to subs and allows each to be controlled separately.

I use Belden cable and Canare connectors to make all of the cables to the length needed. i am fortunate that I can run all cables behind the acoustic panels yet have access to them.

 

[MOON]

Jonathan,

Yes, I have a Simaudio P7 pre with left and right line out going to the first sub and then both left and right rca cables going to the second sub from the 1st sub.

Both Jonathan and Brad, do I just need one rca cable coming off either the left or right from the 1st sub going into the 2nd sub ?

 

[JonFo]

I run 4 Depth I subs center of the wall front, back and both sides. Left and Right RCA cables from the Preamp line level out to 1 front and 1 side Depth. Then 1 RCA from the combined output to either L or Right line level on the other 2 Depth's.

L & R > R Side sub > combined signal > L or R of Front sub.

L & R > Rear sub > combined signal > L or R of L Side sub.

This sends the line level signal to subs and allows each to be controlled separately.
...

Thanks very much for that Brad. Just to confirm then, the 'combined signal' is the output called 'Sub Out', and it contains the summed signal from the inputs, therefore each Depth must have its own crossover settings. Again, for confirmation, your preamp does NOT perform any bass management, right?
In which case, where do your amps for the mains get their signal from?

 

[JonFo]

Jonathan,

Yes, I have a Simaudio P7 pre with left and right line out going to the first sub and then both left and right rca cables going to the second sub from the 1st sub.

Both Jonathan and Brad, do I just need one rca cable coming off either the left or right from the 1st sub going into the 2nd sub ?

Thanks Moon, same question I just posed to brad applies here as well, where do your amps for the mains get their signal from?

Yes, you will only need one cable linking the 'Sub Out' of the first sub to the L or R input of the second Sub. Both subs will need their crossovers set.

So your correct setup will be:

P7 L/R --> Depth i #1 L/R in Depth #1 Sub Out --> Depth i #2 L input
.................|
.............L/R out
.................|
Amp In L/R <-----/


This way, your mains will receive the high-pass crossover output from the first Descent i. This will fix the doubled-up bass you probably have now, and should vastly improve your mid-bass performance in the system.

 

[MOON]

Hi Johnathan,

I now understand that I only need the 1 rca going from the first depth to either left or right input into the 2nd depth.

I don't understand what you wrote after that in the diagram, left and right rca output from 2nd depth I to rca left and right input at the amp. Am I to run a pair of rca's from the second depth i outputs to my amplifier inputs ? I really want to get this hooked up properly.

My amp is ran off xlr from a balanced left and right output from the pre.

 

[Brad225]

Thanks very much for that Brad. Just to confirm then, the 'combined signal' is the output called 'Sub Out', and it contains the summed signal from the inputs, therefore each Depth must have its own crossover settings. Again, for confirmation, your preamp does NOT perform any bass management, right?
In which case, where do your amps for the mains get their signal from?

If the signal from Preamp Out ( no bass management ) is run to Left and Right input of the first Sub, the crossover and other settings are set on that Depth i for that sub.

If the Sub out on the 1st Sub is then run to a 2nd Sub and connected to LFE in, it will use the crossover point and other settings of the first sub. The second sub will have no adjustment in this configuration.

When the 2nd Sub is connected via Sub out from the 1st Sub to either Left or Right of the 2nd sub it will use its own crossover and other settings not the settings of the 1st Sub.

Each additional Sub would be connected the same as the 2nd Sub depending on your preference.


My Preamp has no bass management so the subs receive a line level signal. My amps only have XLR input so separate cabling is run from the Preamp to them.

Hope I didn't make it make it confusing in my description and I answered your question.

 

[MOON]

Thanks Brad, I understand that. However I still need to run rca's from the 2nd sub out's back to my amp inputs, right ?

 

[JonFo]

...
If the Sub out on the 1st Sub is then run to a 2nd Sub and connected to LFE in, it will use the crossover point and other settings of the first sub. The second sub will have no adjustment in this configuration.
...
Each additional Sub would be connected the same as the 2nd Sub depending on your preference.

Thanks Brad, that is the key clarification, so you state (confirm?) that the Sub out is NOT just the sum of the inputs pre-crossover (i.e. L/R + LFE In), but rather is a pass-through for LFE In AND the output of the low-pass section of the internal crossover (usually, only one or the other will have a signal).

If so, then yes, cascading additional subs is a simple matter of connecting the sub out of the preceding unit to the LFE In of the next unit.

To any MartinLogan staff: It would be really helpful if the manual would include a high-level block diagram depicting the paths from inputs to outputs within the unit, including the paths to the internal amp and drivers. You do a great job of illustrating the external hookups, but the critical system model we've been discussing here is not clear.

... My Preamp has no bass management so the subs receive a line level signal. My amps only have XLR input so separate cabling is run from the Preamp to them. ...

OK, so another doubled-up bass scenario, as your mains are getting a full range signal, which means they are being stressed by the very low-end stuff which muddies the mid-bass, and probably means your subs are not carrying as much of the weight as they could, as otherwise it would be too much bass.
Or are you counting on the CLX Crossover to remove the low-end stuff anyway?

In a system of the caliber of yours, and with four subs, I'd recommend looking into an active crossover where you can also control delay. A miniDSP DDRC-88A would be perfect, as it handles both balanced (XLR) and RCA connections, can perform bass management and on top of that Dirac room correction.

I spent 3 hours tweaking delays for my Mid Bass Modules this past weekend, and got measurable and audible improvements from adding 3.2ms of delay (on top of my earlier estimate of 17ms based on distance from the sub), measured group delay improved significantly at the affected frequencies. Any setup where subs are >5' from each other will benefit from delay management. A variable phase adjustment can compensate somewhat, but can not deal with >10' distances.

 

[JonFo]

Thanks Brad, I understand that. However I still need to run rca's from the 2nd sub out's back to my amp inputs, right ?

Moon, in your setup, you will need to run RCA's from the L/R Outputs of the first sub to your amp inputs.

That way the high-pass signal after the crossover will now feed the mains.

You run one cable from the Sub Out of the first sub to the LFE In of the second sub, and set the crossover of the second sub to bypass (assuming the previous post is correct about the sub out containing the low-pass from the crossover in the first sub).

So the updated diagram would be:

P7 L/R --> Depth i #1 L/R in Depth #1 Sub Out --> Depth i #2 LFE input
.................|
.............L/R out
.................|
Amp In L/R <-----/

 

[RUR]

In a system of the caliber of yours, and with four subs, I'd recommend looking into an active crossover where you can also control delay. A miniDSP DDRC-88A would be perfect, as it handles both balanced (XLR) and RCA connections, can perform bass management and on top of that Dirac room correction.

^^^^^^^^^
What Jonathan said.