How connect single subwoofer with 2 monoblocks

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hilde45

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Re: How connect single subwoofer with 2 monoblocks
« Reply #20 on: 13 Apr 2020, 09:17 pm »
I saw that thread. I've heard from others that they actually harmed their Cary amp by trying to high-level wire it.
The reason I'm trying to pre-assess this question is to avoid damaging a new amplifier and/or a valuable sub.
I think the suggestion of the Y cable is or the little stereo to mono box is safe enough to try; experiments with speaker binding posts -- which are REL's preferred way of connecting subwoofers -- is less innocuous. Because I cannot get an answer (yet) from the amp maker, I'm waiting to hear from REL.

sunnydaze

Re: How connect single subwoofer with 2 monoblocks
« Reply #21 on: 13 Apr 2020, 09:53 pm »
If you think there is confusion why don't you try it and tell us how it works out.  :wink:

The OP in that thread has an integrated with outputs labeled "sub".

 :green:

It's the exact same situation.  The guy in the AG thread has a 2nd pair of variable outputs, just like the OP here.  Completely irrelevant that it is an integrated vs the QS line stage in this thread.  Concept is exactly the same -- two pair of variable RCA outputs in both cases.

And why should I try anything?   :scratch:

I don't have a connectivity problem.  I have a preamp with 2 pair of variable outputs, and a pair of Gallo subs that are more flexible than the REL here.  It allows me to use stereo or mono amps, one or two subs,  high-level or low-level connections, without any bother at all. 

Unlike the OP, my Gallos have a pair of RCA inputs for low-level connection, and 2 pair of binding post inputs for high-level amp connection.   Matter of fact, the Gallo even has speaker outputs with a built-in high-pass filter sitting between the amp ins and outs.  In this way I can run main amp into the sub and high-pass the main speakers.  Makes them do less work, resulting in better sound.

opnly bafld

Re: How connect single subwoofer with 2 monoblocks
« Reply #22 on: 13 Apr 2020, 09:58 pm »
TOOBLUVR,
The outputs on the ATC integrated are specific for subs, so not the same thing.
Some HTRs and other pieces have 2 sub outs that are mono.
Did you even read any of the thread?

You can still try it and report back.

sunnydaze

Re: How connect single subwoofer with 2 monoblocks
« Reply #23 on: 13 Apr 2020, 10:08 pm »
The outputs on the ATC integrated are specific for subs, so not the same thing.
Some HTRs and other pieces have 2 sub outs that are mono.
Did you even read any of the thread?

I skimmed it.

He says his integrated has "L/R sub output".  His exact words.   Unless I'm missing something I understand this to mean that it's just plain old pair of normal active RCA outputs.  No different that what's on a line stage with the 2nd pair of outs.  They are designed to run either a sub or another amp for biamping.  The signal is full range and stereo at these outputs. 

It is not an LFE output, which is a single RCA connection that passes a previously processed signal (low passed and stereo combined to mono).

Unless my education is incomplete these are the only 2 ways that you can run signal to a sub using RCA connections.  Is there something else I'm not aware of?

sunnydaze

Re: How connect single subwoofer with 2 monoblocks
« Reply #24 on: 13 Apr 2020, 10:14 pm »
Oh...OK....I got it...I think.    :lol:

Are you saying the integrated's pair of L/R outputs are actually 2 individual LFE outputs....designed to run 2 separate subs?

If not....I'm really lost!     :o

sunnydaze

Re: How connect single subwoofer with 2 monoblocks
« Reply #25 on: 13 Apr 2020, 10:17 pm »
And with that said, I'll bow out now.  I obviously don't know what I'm talking about!      :lol:

I always found this sub connection stuff very confusing......

sunnydaze

Re: How connect single subwoofer with 2 monoblocks
« Reply #26 on: 13 Apr 2020, 10:25 pm »
Wait...wait ....wait!

He specifically says they are L and R output.......and asks if he should combine them for his sub's "mono input".   

If it was already processed LFE outputs he would not be saying that, nor asking the question.  He would simply take one integrated output (processed for sub) and run it into one sub LFE input.  He would not be seeking to combine them.

So I return to my original post.

Sorry for the hijack!

opnly bafld

Re: How connect single subwoofer with 2 monoblocks
« Reply #27 on: 13 Apr 2020, 10:33 pm »
On the ATC they are summed mono outputs specifically for subs even though they are labeled as L & R.

Back to the OP question here, not a good idea to combine L & R with a Y cable on his preamp for a mono sub input.

hilde45

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Re: How connect single subwoofer with 2 monoblocks
« Reply #28 on: 13 Apr 2020, 11:19 pm »
Here is REL's response: "We would recommend connecting low level from your preamp to the R328 as the safest connection for your current setup. As long as it's safe to use a Y splitter out of the QS preamp, this will be fine for going into the single input on the sub."

So now I need to go back to Quicksilver (QS) to ask that question. Jeebus.

hilde45

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Re: How connect single subwoofer with 2 monoblocks
« Reply #29 on: 14 Apr 2020, 01:01 am »
Update from Quicksilver:  "I would connect the ground wire to the right channel amp ground just as they [I believe I quoted Almarg] suggest. If there is a hum then you might have to connect the woofer to just one channel that is disconnect the left  + wire. A Y connector will mono the outputs on the preamp."

Update from me: I tried the high level. Connected to both mono blocks. No hum. Works fine. (Will it last?)


opnly bafld

Re: How connect single subwoofer with 2 monoblocks
« Reply #30 on: 14 Apr 2020, 01:37 am »
 :thumb:

hilde45

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Re: How connect single subwoofer with 2 monoblocks
« Reply #31 on: 14 Apr 2020, 01:44 am »
I'm liking your handle because I find myself "openly baffled." (And not a little red in the face for introducing this topic. Yet the data seemed all over the place from different people.)

Letitroll98

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Re: How connect single subwoofer with 2 monoblocks
« Reply #32 on: 14 Apr 2020, 07:32 am »
Now I may be confused by now, but I believe you said the preamp's rca outputs were modified to have one main out and one tape out.  It that's the case the tape out is NOT variable and will not work to hook up a sub.  If the second output is simply labeled tape and nothing was actually modified you simply use the low level outputs to the rca inputs of the sub.  To use high level inputs on the sub you need two sets of speaker cables, one to the sub from the monoblocks and then a set from the sub to the speakers.  This uses the internal crossover of the sub to take some of the bass load off of the speakers.

hilde45

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Re: How connect single subwoofer with 2 monoblocks
« Reply #33 on: 14 Apr 2020, 11:26 am »
The preamp's rca outputs were modified add a second main out. (What was labeled "tape out" is now the second "main out.") And you're right — just as stated by the QS manufacturer — that tape out will not work to hook up a sub because that's a stereo out and the sub only has a mono input. A Y cable will collapse the stereo field of the other RCA main output to the main speakers.

That said, another way of combining stereo to mono, via a small device, would work. That is a possibility. I want to avoid that, however, because the low-level connection is inferior to high-level, sonically.

But it's all good — I have connected things with REL's high-level connector; this is with the blessing of the amp manufacturer and with no hum on test.

I don't follow the rest of your reply (mentioning two sets of speaker cables), because the sub only has a high level cable which terminates in their Speakon connector port at the sub and sends three wires out to the amplifier's speaker terminals — red, yellow, black.

Speakon: http://signalcable.com/images/RelSpeakon.jpg

mix4fix

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Re: How connect single subwoofer with 2 monoblocks
« Reply #34 on: 14 Apr 2020, 12:45 pm »
On the ATC they are summed mono outputs specifically for subs even though they are labeled as L & R.

Back to the OP question here, not a good idea to combine L & R with a Y cable on his preamp for a mono sub input.

http://www.faqs.org/faqs/car-audio/part4/

Quote
5.16   How do I turn a stereo signal into a mono signal [BW]
=================================================================

Creating a mono signal is often necessary when you are powering a
subwoofer by bridging the amplifier.  Many people do not realize that
bridging an amplifier does not always provide a mono signal - many
amplifiers will simply use only one input channel, which means that the
subwoofer won't be receiving the full signal.

Some amplifiers have a switch that will allow you to combine the left
and right channels into a mono signal.  Some signal processors and head
units provide a subwoofer-out channel that can be switched between
stereo and mono.

If you don't have this feature on any of your equipment, you will need
to provide a mono signal to the amplifier.  The common thought is to use
a Y-adapter to "combine" the left and right channels.  However, by
using a Y-adapter, you are actually summing the line voltages and
directly shorting the left and right channels at the head unit, which
could cause problems.

The correct way to create a mono signal is to cut off the ends of the
RCA cables, combine the signal grounds (the outer shield), and then use
a 1 kOhm (1/4 watt, 5% tolerance) resistor to each of the center
conductors.  Solder and insulate the resistors so that you don't short
them prematurely, and then connect the two resistors together.  Connect
the summed signal ground to the shield of the new RCA plug, and the
summed center conductor to the center pin of the RCA plug.

I always refer to this whenever the discussion of combining RCA signals comes up. It's car audio, but it's the same principal. As long as you have that 1/4 watt resister on the center pins, everything is good. I built and still have a summing circuit I built long time ago. I used a radio Shack project box, multi-RCA panel, resisters, and some wire. I had it set up where the two middle pairs were stereo and the two outer pairs were summed. It's weird but I can never miss-connect anything. Stereo in, stereo out, and four mono connections. Plus, I don't like destroying functional RCA cables.
« Last Edit: 14 Apr 2020, 06:08 pm by mix4fix »

hilde45

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Re: How connect single subwoofer with 2 monoblocks
« Reply #35 on: 14 Apr 2020, 12:51 pm »
Thank you!
I saw a couple solutions already made:
Simple stereo to mono device: https://tinyurl.com/w4p5dxf
More complex, programmable device: https://tinyurl.com/rjaxcxq

sunnydaze

Re: How connect single subwoofer with 2 monoblocks
« Reply #36 on: 14 Apr 2020, 01:07 pm »

snip

I don't follow the rest of your reply (mentioning two sets of speaker cables), because the sub only has a high level cable which terminates in their Speakon connector port at the sub and sends three wires out to the amplifier's speaker terminals — red, yellow, black.

Speakon: http://signalcable.com/images/RelSpeakon.jpg

He was just talking general concept = speaker cable from amp to sub for high level connection.
This is how I connect my sub.

REL does the exact same thing, they just use their own proprietary cable / connector.

hilde45

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Re: How connect single subwoofer with 2 monoblocks
« Reply #37 on: 14 Apr 2020, 01:13 pm »
Thanks -- that helps. I'm limited to what the back of my REL gives me, so I wasn't following. Appreciate the clarification and I now get the general (and helpful) point.

mix4fix

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Re: How connect single subwoofer with 2 monoblocks
« Reply #38 on: 14 Apr 2020, 06:06 pm »
Here is REL's response: "We would recommend connecting low level from your preamp to the R328 as the safest connection for your current setup. As long as it's safe to use a Y splitter out of the QS preamp, this will be fine for going into the single input on the sub."

So now I need to go back to Quicksilver (QS) to ask that question. Jeebus.

I would distrust REL from now on. They are an established audio manufacturer, and they are recommending a ghetto method for using their products.

opnly bafld

Re: How connect single subwoofer with 2 monoblocks
« Reply #39 on: 14 Apr 2020, 06:28 pm »
I would distrust REL from now on. They are an established audio manufacturer, and they are recommending a ghetto method for using their products.

Maybe they had limited staff and no tech when this REL person gave a bad answer in the reply.  :dunno: