Dual Descent i set up help needed

[NAK8]

Can anyone give me some advice on best practice to run dual subs? I have two Martin Logan Descent i subs for a strictly two channel system with ML Prodigy mains.

My options are:
Speaker level in
RCA in (sub has both left and right in for single sub use)
Balanced XLR (LFE)in (only one XLR in)

I am running the Sonic Frontiers Line 3 which has both balanced (XLR) and SE (RCA) outputs.

As of now, I am running them from the 2nd post on my Krell 300M amps (they have two speaker post for the same channel) but was wondering if it would be just as well to run SE (rca) left out from preamp to left sub in and vice versa for the right. Or, go balanced #2 outs from preamp (balanced #1s used for amps) to the single (XLR) LFE in on the subs. I am thinking the XLR approach may simulate a combined L + R input and thus higher gain on the subs...but, would that muddy a two channel system up or give each sub full utilization..

Thoughts, opinions, scientific facts? :music:

NAK8

 

[robertawillisjr]

Many sub makers recommend using the speaker in (if I understand you, that means that a set of speaker wires are run from the amplifier to the sub) because you get the audio signature of the amp that supplies the main speakers.

 

[Gordon]

I run a 2.2 system. I have separated the sub channels to left and right using XLR to each side. My preamp allows me to do this, I'm not certain if yours does.

I initially ran a single wire to one sub and slaved the other in. I didn't care for the presentation. Once I separated the subs into a L/R configuration and adjusted each one with a test disc and spl meter, the subs came into bloom.

I can't understand why anyone would want to combine the sub channels if they are able to separate them especially in a two channel system. While bass is theoretically omnidirectional, the recording "may" have a bit more in one side or the other and I want my sub to produce that difference.

Gordon

 

[roberto]

Can anyone give me some advice on best practice to run dual subs? I have two Martin Logan Descent i subs for a strictly two channel system with ML Prodigy mains.

My options are:
Speaker level in
RCA in (sub has both left and right in for single sub use)
Balanced XLR (LFE)in (only one XLR in)

I am running the Sonic Frontiers Line 3 which has both balanced (XLR) and SE (RCA) outputs.

As of now, I am running them from the 2nd post on my Krell 300M amps (they have two speaker post for the same channel) but was wondering if it would be just as well to run SE (rca) left out from preamp to left sub in and vice versa for the right. Or, go balanced #2 outs from preamp (balanced #1s used for amps) to the single (XLR) LFE in on the subs. I am thinking the XLR approach may simulate a combined L + R input and thus higher gain on the subs...but, would that muddy a two channel system up or give each sub full utilization..

Thoughts, opinions, scientific facts? :music:

NAK8

Hol Nak8. Because the Descents I are not balanced, you can use from your pre out RCAs left and right to feed your subs with no problem, and balanced to your Krell amp from the preamp out. Because you are feeding the sub with long runs, a good quality RCA cables you should use. Do not worry about the long run for the RCA cables...low frequency RCAs are not affected by long runs. Happy listening,
Roberto.

 

[NAK8]

Thanks Robert, Gordy, and Berto...

Berto,

Correct, the Descents are not true balanced but it does have one input via XLR, which is an LFE in. Do you know if via this channel, the gain is increased as it would internal combine channels? What I am getting at is... when I have connected one input (channel) on subs, in the past, I would get sound...when I connected the other input/channel in combination, volume would increase as both channels were funneling into the sub now.

I have Vandersteeen subs in another room and in the manual it says that though not needed often, you can jump one input to the other for increased volume....this is for a dual sub setup and the vandies only have speaker level input. There is a noticeable difference in feeding one channel compared to two channels hitting a single sub via line level.

I wonder if the XLR input combines the channels internally or if that signals voltage combination is done on the preamp/HT Receiver's side. I am a bit of a bass junkie so I am trying to maximize the bottom end without deteriorating the overall quality of the sound. That said, if the XLR in will give me more SPL then maybe that would be a good "trick" for setting these subs up. I should not lose the left and right effect as that signal will be coming form my preamp left and right accordingly.

Anyone have knowledge if this will be fact, increased SPL, or do these not work like this?

NAK8

 

[roberto]

Thanks Robert, Gordy, and Berto...

Berto,

Correct, the Descents are not true balanced but it does have one input via XLR, which is an LFE in. Do you know if via this channel, the gain is increased as it would internal combine channels? What I am getting at is... when I have connected one input (channel) on subs, in the past, I would get sound...when I connected the other input/channel in combination, volume would increase as both channels were funneling into the sub now.

I have Vandersteeen subs in another room and in the manual it says that though not needed often, you can jump one input to the other for increased volume....this is for a dual sub setup and the vandies only have speaker level input. There is a noticeable difference in feeding one channel compared to two channels hitting a single sub via line level.

I wonder if the XLR input combines the channels internally or if that signals voltage combination is done on the preamp/HT Receiver's side. I am a bit of a bass junkie so I am trying to maximize the bottom end without deteriorating the overall quality of the sound. That said, if the XLR in will give me more SPL then maybe that would be a good "trick" for setting these subs up. I should not lose the left and right effect as that signal will be coming form my preamp left and right accordingly.

Anyone have knowledge if this will be fact, increased SPL, or do these not work like this?

NAK8

I understand better now...you are converting the LFE balanced to a RCA and goes to the LFE input, then you from the output of that sub, you can feed the signal to the other sub, yes , there is a little level signal loss this way...but you can compensate it with the volume knob. With the aid of an Iphone (SPL) or non expensive SLP meter from Radio Shack you can measure to have both the same level...or by ear ( I do trust in my ears)...happy listening,
Roberto.

 

[NAK8]

So I tried the RCA route... From my preamp L RCA out to left in on Sub and vice versa to the right. Left and right #1 outs are going directly to my amps and then to the Prodigies for full range sound. Outs #1 happen to be balanced XLR.

This sounds darn good...just as good and maybe smoother than the speaker level ins from the amp/speaker terminals.

Regarding the LFE in.... after reading the manual more carefully, I realized that when LFE IN is used, the internal cross over network is bypassed. This is so because the output on the LFE receiver/processor manages the crossover of the higher frequencies and only sends the low frequencies to the sub so no cross over would be needed in the sub. If I ran it full range from Balanced/XLR #2 OUT on my preamp, I would be sending a full range signal to the sub and the sub would not be crossed over so muddy bass would occur and/or sub damage. When in doubt...RTFM.

Thanks for the help gents... if anyone else wants to put in their 2 pennies, I welcome them. This is especially so if there are some scientific facts behind them.

-NAK8