Adding dual subs to my 2 channel vintage home system (wiring help??)

[C-Pop]

Looking for wiring suggestions as I add dual 10" subs to my home 2/C system. Here is my current setup:
1) Rotel CD player + A/T TT >>> Rotel tuner/preamp >>> RB1070 power amp >>> Thiel CS1.2 speakers
2) Preamp does not have sub outs
3) Subs are powered and will accept high level inputs and have high level output terminals as well

My current wiring strategy is to run the output speaker wires from my amp into high level inputs on (active) subs then output directly to speakers on each side. This essentially puts the sub in the output chain before the speaker and using the sub amp to power the speakers. I would also position the sub to the inside of each speaker. I am concerned that the Thiels are 4ohm speakers. My amp has been doing a fine job of powering the Thiels at 130W/channel. Would this config create power issues to the Thiels (or for my amp) as a result of placing the amps in the output chain prior to the speakers?

Any thoughts, feedback or suggestions for a better schematic would be greatly appreciated!

TIA,
C-Pop

 

[spark1]

The speaker outs on your subs just pass thru the output from your main amp. In other words, the Thiels will still be powered by the Rotel.

If your amp has A and B speaker outputs, you can use A for the mains and B for the subs (doubling up the connections because you have two subs). Electrically the same, other than bypassing the extra connections involved when running mains thru the subs.

The subs have very high impedance, so present only a tiny, virtually irrelevant load on your main amp. In other words, the load on the Rotel is, effectively, only a function of the Thiels regardless of which wiring approach you use.

A few (very few) subwoofers provide a high-pass filter on their speaker-level output...in which case the lowest frequencies (below 80Hz is a fairly common high-pass filter point) will be rolled off and handled by the sub instead.

 

[C-Pop]

The speaker outs on your subs just pass thru the output from your main amp. In other words, the Thiels will still be powered by the Rotel.

If your amp has A and B speaker outputs, you can use A for the mains and B for the subs (doubling up the connections because you have two subs). Electrically the same, other than bypassing the extra connections involved when running mains thru the subs.

The subs have very high impedance, so present only a tiny, virtually irrelevant load on your main amp. In other words, the load on the Rotel is, effectively, only a function of the Thiels regardless of which wiring approach you use.

A few (very few) subwoofers provide a high-pass filter on their speaker-level output...in which case the lowest frequencies (below 80Hz is a fairly common high-pass filter point) will be rolled off and handled by the sub instead.

Thanks spark1! I was hoping to hear from you. You were the first to suggest to me adding the subs to the Thiels late last year. Do you see any issues with placement of the subs just inside of my mains?

 

[spark1]

Heck, you can even triple up the speaker connections on one set of terminals on your Rotel (one set to the Thiels, and a set to each of the subs), Again, same electrically.

Or wire mains and one sub to Rotel, and link the seconds sub to the first from its speaker outs. Same again.

Comes down to what is most convenient for you. The reason I like the mains to A and subs to B (if you have that luxury) is that I find it easier to get the mains and subs balanced in that configuration; you can turn off mains, or turn off subs, to get a better sense of relative loudness and response.

 

[spark1]

Thanks spark1! I was hoping to hear from you. You were the first to suggest to me adding the subs to the Thiels late last year. Do you see any issues with placement of the subs just inside of my mains?

I hesitate to make any recommendation on sub placement, as it will only start an argument with someone who disagrees.

That said, in one of my systems, the pair of subs is slightly inside the mains, and behind them. In the other, they flank the mains. I have adjusted crossover and output to achieve good results with both.

 

[fill35u]

A few (very few) subwoofers provide a high-pass filter on their speaker-level output...

Which subs do this?

 

[fill35u]

I would also position the sub to the inside of each speaker.

What's special about those locations?

 

[C-Pop]

I hesitate to make any recommendation on sub placement, as it will only start an argument with someone who disagrees.

That said, in one of my systems, the pair of subs is slightly inside the mains, and behind them. In the other, they flank the mains. I have adjusted crossover and output to achieve good results with both.

Thanks! That's the same placement Paul McGowan at PS Audio recommends. Lots of opinions out there, but Paul has made a pretty good career in this business. I'd say his opines have a very solid basis in facts and data.

 

[C-Pop]

What's special about those locations?

This is a 2/C system that I am adding to. Dual subs create a "stereo" sub effect in a 2/C environment , much different than a single sub set up on HTS. So placement of duals inside the mains is a pretty wide recommendation. I verified with spark1 b/c I trust his judgement.

 

[spark1]

Which subs do this?

Monitor Audio ASW100 is one. But the point is that this is very uncommon. I mentioned it only because the OP did not mention his make/model. I expected response about my placement comment...surprised that the first one was about this topic instead.

 

[Lavane]

If running two subs with speaker level input, one sub per channel, would you just connect to one channel on the sub speaker input, or split and connect one channel coming from the amp to both speaker connections on the sub?

 

[spark1]

One.

 

[opnly bafld]

If running two subs with speaker level input, one sub per channel, would you just connect to one channel on the sub speaker input, or split and connect one channel coming from the amp to both speaker connections on the sub?

Depends on the gain and matching with the main speakers, some systems one is enough, but using the other can increase gain going to the sub amp.
REL touches on this in their setup guide, each sub has 2+ wires and 1- wire, if using two subs you can connect one or both +, if both are used the gain control on the sub needs to be lowered.

 

[fill35u]

Monitor Audio ASW100 is one. But the point is that this is very uncommon.

Good catch on that ASW100! Very good reason that they are uncommon, a passive crossover without taking into account the impedance and response curves of the speaker would be a pure crapshoot, at best. I guess in a world of infinite universes, *somebody* would be dumb enough to manufacture such a crude scheme. Unbelievable.

I expected response about my placement comment...surprised that the first one was about this topic instead.

Whatever location works, works! So long as it's chosen on a solid basis of performance, not merely aesthetics or convenience.

And once the OP had this to say:

Thanks! That's the same placement Paul McGowan at PS Audio recommends. Lots of opinions out there, but Paul has made a pretty good career in this business. I'd say his opines have a very solid basis in facts and data.

I realized that they were beyond helping anyhow. Wow.

 

[spark1]

Good catch on that ASW100! Very good reason that they are uncommon, a passive crossover without taking into account the impedance and response curves of the speaker would be a pure crapshoot, at best. I guess in a world of infinite universes, *somebody* would be dumb enough to manufacture such a crude scheme. Unbelievable.



Whatever location works, works! So long as it's chosen on a solid basis of performance, not merely aesthetics or convenience.

And once the OP had this to say:



I realized that they were beyond helping anyhow. Wow.

I half-way remembered that one from a thread a few years back. In that same thread, there were a couple of others named. There are, of course, very good reasons why it is uncommon.

I believe if the OP takes the time to use the crossover and level controls of his subs judiciously, he will get good results regardless of placement (within reason!).

 

[fill35u]

I believe if the OP takes the time to use the crossover and level controls of his subs judiciously, he will get good results regardless of placement (within reason!).

"Good" is of course relative. And it's of course much easier to satisfy just a single listening position.
At this point, my concern would be if the OP realizes how chasing "stereo bass" is tilting at windmills. I'd like the OP to list the recordings with verified stereo bass that he's aiming to reproduce. If it's not in the source material, there's no point in restricting the sub locations to support it.

 

[spark1]

I will not engage in the stereo subwoofer debate, as I am not knowledgeable enough to do so.

Based on some reading on the subject over the years, I do believe that there will be some amount of different low frequency (sub-100Hz) information in each channel on a small - but not tiny - number of recordings. But, this is not my reason for preferring two subs to one. I just find that it provides a more distributed, less "locatable" (I made up a word) and more natural sound. This could of course be a function of "purchase bias (I paid for two subs, so they must be better than one sub). I have seen members here advocate for even more subs...perhaps as an alternative to fewer, more expensive (higher-powered/more cone surface) units? Kind of the same rational as line array speakers?

I have messed with running both channels to each sub, but only for relatively casual comparison. Two subs sound better either way (to me) than one. I cannot say that I noticed any difference vs than with stereo wiring, other than in recordings with intentionally hard-panned bass elements. So, I run mine in stereo...cuts down on the wiring!

 

[Grenadeslio]

I've used the same location with stereo subs and speakers on stands. I've also and currently am using a pair of 12" Dayton subs as stands, currently for my Jamo C103's as mains in the multi-channel setup.

the tv has changed from the 46" pictured to a 70" now




This picture was taken at the old digs as a 2 channel setup.

 

[Dingman]

I hesitate to make any recommendation on sub placement, as it will only start an argument with someone who disagrees.

I disagree with that.

 

[fill35u]

Based on some reading on the subject over the years, I do believe that there will be some amount of different low frequency (sub-100Hz) information in each channel on a small - but not tiny - number of recordings

All this belief, system design goals should be based on *evidence*. Surely somebody here advocating stereo subwoofers can list some songs with strongly decorrelated bass?

But, this is not my reason for preferring two subs to one. I just find that it provides a more distributed, less "locatable" (I made up a word) and more natural sound

Multiple subwoofers certainly provide the *opportunity* for more even bass response. But that's got nothing to do with stereo bass.