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#147853 - 09/18/06 01:08 PM Running two sets of mains
Stymie Offline
veteran

Registered: 08/17/06
Posts: 132
Loc: Edge of Distraction
I tried searching on this but I'm probably not searching for the right terms. Let's say you wanted to run two sets of mains (M80s for example) and you have mono blocks for each speaker. Is it a simple matter of running the preouts into y cables and then to the amps? The left preout would feed a pair of amps via a y cable and subsequently a pair of M80s and the right preout would do the same.

Another option would be to only use a pair of amps with the speakers run in series. This would create a 2 Ohm load on each amp (I believe) and would assume the amps could handle the 2 Ohm load.

Is one better than the other? Another option?

Stymie
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#147854 - 09/18/06 02:16 PM Re: Running two sets of mains [Re: Stymie]
pmbuko Offline
shareholder in the making

Registered: 04/02/03
Posts: 16273
Loc: Leesburg, Virginia
If you want to run both pairs of mains simultaneously, then splitting the pre-outs via a Y-cable is probably the best solution. Keep in mind that when you split a signal like that, each branch of the split will receive a weaker signal. This isn't usually a problem since you can just turn up the volume.

As to running the speakers in series, it would actually double the ohm rating (totalling 8 Ohms), not halve it. Running speakers in series is not recommended because as the signal passes from the first speaker to the second, the resistance of the first speaker changes the signal. So the signal going into the first speaker in the line won't be identical to the signal entering the second speaker.

A series connection looks like this:

AMP <====> Speaker 1 <====> Speaker 2

What you'd want to do is run the speakers in parallel. This prevents the two speakers from interacting, but it does halve the resistance (effective 2 Ohm resistance).

A parallel connection looks like this:

Speaker 1 <====> AMP <====> Speaker 2
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#147855 - 09/18/06 04:37 PM Re: Running two sets of mains [Re: pmbuko]
pmbuko Offline
shareholder in the making

Registered: 04/02/03
Posts: 16273
Loc: Leesburg, Virginia
A little birdie told me my serial and parallel diagrams are a bit misleading so I'm making a correction. Here's a better illustration.


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#147856 - 09/18/06 04:37 PM Re: Running two sets of mains [Re: pmbuko]
Stymie Offline
veteran

Registered: 08/17/06
Posts: 132
Loc: Edge of Distraction
Thanks! I had the right idea, but used the wrong terminology. I was thinking parallel and used series. At least I was on the right track.

As long as both sets are identical, are there any drawbacks to running two sets of mains assuming the equipment is adequate? Any frequency cancellation or things like that?
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#147857 - 09/18/06 04:42 PM Re: Running two sets of mains [Re: Stymie]
pmbuko Offline
shareholder in the making

Registered: 04/02/03
Posts: 16273
Loc: Leesburg, Virginia
Are you going to have them in the same room? What arrangement are you thinking of?
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#147858 - 09/18/06 05:08 PM Re: Running two sets of mains [Re: pmbuko]
Stymie Offline
veteran

Registered: 08/17/06
Posts: 132
Loc: Edge of Distraction
Same room. Most of this is planning ahead for a what if scenario. But just in case it comes to fruition, I want to be prepared.

It's also based on timing. If were to get my hands on a second set of M80s while I'm in my current location, I had thought about putting the second set on top of the first set, but inverted. (tweeter to tweeter) This would basically create a pair of M160s (sort of).

The more likely scenario would be for a much larger room with them set up in normal fashion with approximately 10' between them. M80(L2) - 10' - M80(L1) - 10' - M80(R1) - 10' - M80(R2)
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#147859 - 09/18/06 05:15 PM Re: Running two sets of mains [Re: Stymie]
Ken.C Offline
shareholder in the making

Registered: 05/03/03
Posts: 17765
Loc: NoVA
Good lord! How big is the room?!


Oh yeah.

Tweet.
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I didn't do it, no one saw me, you can't prove anything.

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#147860 - 09/18/06 05:33 PM Re: Running two sets of mains [Re: Ken.C]
Stymie Offline
veteran

Registered: 08/17/06
Posts: 132
Loc: Edge of Distraction
It's a finished basement, ~30'x~50'.
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#147861 - 09/18/06 05:35 PM Re: Running two sets of mains [Re: Stymie]
Ken.C Offline
shareholder in the making

Registered: 05/03/03
Posts: 17765
Loc: NoVA

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#147862 - 09/18/06 05:39 PM Re: Running two sets of mains [Re: Stymie]
pmbuko Offline
shareholder in the making

Registered: 04/02/03
Posts: 16273
Loc: Leesburg, Virginia
That sort of spacing will really interfere with your imaging. Many speaker manufacturers go to great lengths to ensure that the drivers in the speakers are "time corrected" - meaning the soundwaves from each driver in a cabinet will reach your ear at the same time. By having the like-channel speakers set apart by 10 feet, the sound from the inner speakers will reach your ears sooner than the sound from the outer speakers. (How much sooner depends on how close you are sitting, of course.)

If you really want to double up the channels, keep the like-channels side by side.


Edited by pmbuko (09/18/06 05:43 PM)
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#147863 - 09/18/06 05:46 PM Re: Running two sets of mains [Re: pmbuko]
Stymie Offline
veteran

Registered: 08/17/06
Posts: 132
Loc: Edge of Distraction
Good to know. What if you place them in an arc (semi circle) instead of in a row to cut down on the distance to the listening position?
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#147864 - 09/18/06 05:54 PM Re: Running two sets of mains [Re: Stymie]
Ken.C Offline
shareholder in the making

Registered: 05/03/03
Posts: 17765
Loc: NoVA
Personally, I think I'd probably just stick a big honking amp on a single pair--and get at least two big subs. But the question is, do you really need to pressurize the entire room?
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I didn't do it, no one saw me, you can't prove anything.

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#147865 - 09/18/06 06:20 PM Re: Running two sets of mains [Re: Ken.C]
Stymie Offline
veteran

Registered: 08/17/06
Posts: 132
Loc: Edge of Distraction
It's not a have to thing and in reality, will likely never happen. We're house shopping and one of the ones that we saw had this massive room. There's already a contract on the house, so I'm not holding my breath.

But if by some miracle it does go our way, I'd be forced to do something with it and thus my wheels started spinning. It probably won't happen, but it's fun to think about it.

Of course, now I can't get the images of M160s out of my head.
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#147866 - 09/19/06 12:33 PM Re: Running two sets of mains [Re: Stymie]
cava Offline
enthusiast

Registered: 08/23/06
Posts: 33
There really isn't much benefit to having double the speakers. There would be no gain in quality, unless m80's sound better at lower volumes for some reason (hence the combination of two at the same level would sound better). You could actually hinder some aspects of quality depending on placement. The amount of added spl would be minimal with only a 3 dB increase which is close to the threshold of a noticable difference in level. A doubling of sound pressure generates a 3 dB increase in level.

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#147867 - 09/19/06 09:13 PM Re: Running two sets of mains [Re: cava]
RickF Offline
axiomite

Registered: 02/26/05
Posts: 5210
Loc: Vero Beach, Florida
I ran my 60s with my 80s for a little while way back when, pre-outed the 80s to an amp from the H/K and ran the 60s from the receiver....Wid thought I was nuts but I thought they sounded pretty darn good.

The 60s and 80s also made for a very nice looking set (double set?) of mains parked next to one another.
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Rick
Our Room

smile

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#147868 - 09/19/06 09:20 PM Re: Running two sets of mains [Re: RickF]
Wid Offline
axiomite

Registered: 06/22/03
Posts: 6720
Loc: The Peoples Republic of Il.
Quote:

Wid thought I was nuts but I thought they sounded pretty darn good.





And still do
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Rick


"A fear of weapons is a sign of retarded sexual and emotional maturity." Sigmund Freud


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#147869 - 09/19/06 09:22 PM Re: Running two sets of mains [Re: Wid]
RickF Offline
axiomite

Registered: 02/26/05
Posts: 5210
Loc: Vero Beach, Florida
>>> And still do

And I *still* take that as a compliment!
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Rick
Our Room

smile

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#147870 - 09/19/06 09:23 PM Re: Running two sets of mains [Re: RickF]
Wid Offline
axiomite

Registered: 06/22/03
Posts: 6720
Loc: The Peoples Republic of Il.

_________________________
Rick


"A fear of weapons is a sign of retarded sexual and emotional maturity." Sigmund Freud


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#147871 - 09/20/06 11:23 AM Re: Running two sets of mains [Re: Wid]
michael_d Offline
connoisseur

Registered: 07/23/04
Posts: 3903
Loc: Up yonder
You're both nuts.
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#147872 - 09/20/06 11:48 AM Re: Running two sets of mains [Re: RickF]
pmbuko Offline
shareholder in the making

Registered: 04/02/03
Posts: 16273
Loc: Leesburg, Virginia
Between the both of you, I count 6 nuts.
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#147873 - 09/20/06 12:20 PM Re: Running two sets of mains [Re: pmbuko]
alan Offline
connoisseur

Registered: 01/29/02
Posts: 3187
Loc: Toronto/New York/Dwight
Peter,

That's true in general what you say about the imaging but I suspect that in a room that large, if it also has a high or vaulted ceiling, all talk of timing and "imaging" go out the window because of the huge reverberant space. In one such room with a cathedral ceiling that housed an excellent pair of large Canadian floorstanding speakers plus two big subwoofers at one end and the couch at the other, I did some listening comparisons with several of my listening panel members from the National Research Council.

What was amazing was that when we switched from stereo to mono, none of us could hear any difference! It was simply a huge reverberant wall of sound.

In a related experiment conducted in more formal testing conditions (double blind) in the NRC listening room, we discovered that simply running a second set of left/right main speakers set a few feet farther apart to either side of the main pair of L/R fronts produced an amazing improvement in overall realism and spaciousness, something akin to what we now experience when we listen to a stereo recording in DPLII that decodes really well into 5.1. At the time, were testing very early digital and analog "bucket-brigade" delay systems that routed the main channel signals, delayed by an adjustable amount, to several surround speakers on the side walls. This was long before the advent of Dolby Digital or Dolby Surround.

The addition of the extra stereo pair of main speakers up front provided as much realism as the delay devices, which were quite expensive back in the early 1980s.

In a room that large, I'd say go ahead and try an extra pair of M80s or M60s set up as described. Depending on the room, it might deliver a noticeable improvement in spaciousness and realism.

The NRC test was done in a standard IEC listening room that parallels a typical domestic rectangular living room of average dimensions.
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#147874 - 09/20/06 12:23 PM Re: Running two sets of mains [Re: pmbuko]
alan Offline
connoisseur

Registered: 01/29/02
Posts: 3187
Loc: Toronto/New York/Dwight
pmbuko,

Thanks for the excellent diagram of series and parallel connections. I may have to borrow that for the next time I address this subject in the Axiom newsletter.
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Alan Lofft,
Axiom Resident Expert

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#147875 - 09/20/06 12:31 PM Re: Running two sets of mains [Re: cava]
alan Offline
connoisseur

Registered: 01/29/02
Posts: 3187
Loc: Toronto/New York/Dwight
Quote:

There really isn't much benefit to having double the speakers. There would be no gain in quality, unless m80's sound better at lower volumes for some reason (hence the combination of two at the same level would sound better). You could actually hinder some aspects of quality depending on placement. The amount of added spl would be minimal with only a 3 dB increase which is close to the threshold of a noticable difference in level. A doubling of sound pressure generates a 3 dB increase in level.




Cava, a modest correction: A 1-dB increase or decrease in SPL is the smallest (barely) detectable change in subjectively perceived loudness. A 3-dB increase is subjectively perceived by most listeners as "somewhat louder" (or "somewhat softer" if it's a 3-dB decrease in SPL).

Your other points I'd agree with.
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Alan Lofft,
Axiom Resident Expert

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#147876 - 09/20/06 05:06 PM Re: Running two sets of mains [Re: alan]
pmbuko Offline
shareholder in the making

Registered: 04/02/03
Posts: 16273
Loc: Leesburg, Virginia
You're welcome. I'll waive royalties in favor of QS4s.
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"I wish I had documented more…" said nobody on their death bed, ever.

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#147877 - 09/20/06 10:22 PM Re: Running two sets of mains [Re: pmbuko]
JohnK Offline
shareholder in the making

Registered: 05/11/02
Posts: 10383
Good thought, Peter, but you should ask for QS8s and then maybe settle for QS4s.
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Enjoy the music, not the equipment.



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#147878 - 09/20/06 10:53 PM Re: Running two sets of mains [Re: JohnK]
pmbuko Offline
shareholder in the making

Registered: 04/02/03
Posts: 16273
Loc: Leesburg, Virginia
I should hang around with lawyers more often.
_________________________
"I wish I had documented more…" said nobody on their death bed, ever.

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#147879 - 09/25/06 05:40 PM Re: Running two sets of mains [Re: alan]
cava Offline
enthusiast

Registered: 08/23/06
Posts: 33




Cava, a modest correction: A 1-dB increase or decrease in SPL is the smallest (barely) detectable change in subjectively perceived loudness. A 3-dB increase is subjectively perceived by most listeners as "somewhat louder" (or "somewhat softer" if it's a 3-dB decrease in SPL).

Your other points I'd agree with.





Yeah, I guess my definition of "close" was not close enough...haha. Although when I listen to one of those cd's that repeats a tone in 1 dB decreasing increments I can't really tell that each step is quieter, just that it definitely gets quieter after several steps.

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#147880 - 09/26/06 01:55 PM Re: Running two sets of mains [Re: cava]
alan Offline
connoisseur

Registered: 01/29/02
Posts: 3187
Loc: Toronto/New York/Dwight
Cava,

It's much harder to detect small increments or decreases in loudness using single-frequency test tones. A pink-noise signal simulates a typical music signal much better, and it's a more critical test signal for loudness levels.

Some types of music make it easier to detect slight increases. But by definition, a 1-dB step is "barely detectable".
I was just being my usual obsessive self. . .ha.
_________________________
Alan Lofft,
Axiom Resident Expert

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#147881 - 09/26/06 08:03 PM Re: Running two sets of mains [Re: alan]
cava Offline
enthusiast

Registered: 08/23/06
Posts: 33
I'm starting to realize that that is one of the reasons why I like this hobby so much. It allows me to obsess over little details, my OCD just eats it up, while my wallet coughs it up.

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#147882 - 09/26/06 09:39 PM Re: Running two sets of mains [Re: cava]
Rik Offline
hobbyist

Registered: 03/15/05
Posts: 29
Loc: Louisiana
I think this article has pertinence to this thread. It is about the Audyssey EQ, but on page two they talk about a 10.2 surround format and only one channel is in the rear the rest of the channels are across the front sound stage.
another Audioholic's article

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#147883 - 09/27/06 12:09 AM Re: Running two sets of mains [Re: Rik]
pmbuko Offline
shareholder in the making

Registered: 04/02/03
Posts: 16273
Loc: Leesburg, Virginia
That's not quite true. There are a pair of subs directly to the sides and a pair or speakers slightly behind that.


_________________________
"I wish I had documented more…" said nobody on their death bed, ever.

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#147884 - 09/28/06 12:51 AM Re: Running two sets of mains [Re: pmbuko]
Rik Offline
hobbyist

Registered: 03/15/05
Posts: 29
Loc: Louisiana
True enough, I meant one thing and type something else. I should have typed: I think this article has pertinence to this thread. It is about the Audyssey EQ, but on page two they talk about a 10.2 surround format and only one channel is added in the rear the rest of the added channels are across the front sound stage.

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