The Perils of Stacking Speakers

[frankmarsi]

1-18-17 2P.M.EST

All this mention of ‘stacking’ is misleading. Unless done properly, it’s just a waste of time and space with inherent pitfalls and an amateur’s attempt at something more that really isn’t with-in the confines of an audiophile’s better listening perspective.

Going back as far as 2004 I believe I was one of the only ones on this site to mention it as I was using four ‘stacked’ LST’s. Later on, I tried stacking four 3a’s along with two PL-400’s, my results were disheartening.

Although stacking speakers is nothing new, it must be done correctly to fully appreciate it’s benefits.
One notable successful stacking arrangement is accomplished years ago with Advents driven by two Phase Linear PL-400 amps, do a search and see. Here the stacking is well realized as the Advents have a more forward mid and high frequency output and the woofer is crossed-over at a higher frequency.

A while ago, RoyC mentioned about the overly dominant bass that is rendered, especially with 3a’s.  Of course, he is correct!

First off, exact matching speakers and amplifiers is of the utmost importance and necessity.
I’ve read of people doing it with mismatched speakers and woefully inadequate amplifiers, an amateur’s foray at best. This use is a sorrowful attempt at trying to increase the sound-field but, doing so only gives forth an unbalanced and inaccurate sound as a result with no more than a 3db. increase in volume if using everything as matched.
Also, proper room set-up is paramount as over-powering a room may be the result unless correct guide lines are utilized and followed. Room-damping is advised and using proper sound/bass/ ‘traps’ and certainly even the arrangement of furniture comes into play.

In vain attempts to ‘stack’ their speakers some folks are even using a single amplifier of inadequate power, that in of itself is a recipe for a blown amplifier with-in a short amount of time as 3a’s are a difficult speaker to drive in the first place. Using two different amplifiers of different specifications makes no sense at all!

FM
Further reading:

https://www.reddit.com/r/audio/comments/1zgi4t/what_are_the_pros_and_cons_to_stacking_speakers/

http://forums.stevehoffman.tv/threads/do-you-recommend-hooking-up-4-speakers-in-a-two-channel-stereo.262276/

[samberger0357]

I'm currently running a pair of AR 3's on top of a pair of 3a's, and they match up quite nicely. Both have been restored. The 3's are a little darker, of course they have the cloth woofer. The 3a's have the foam woofer, and tend to be a little brighter.  Together they compliment each other very nicely.

I've used different amp pairings, and presently I'm using a Crown XLS1000 to drive them all. It can safely drive 2 ohm loads, and deliver 525 watts doing it. So plenty of juice. But I've also had good results using a Harman Kardon Citation 22 on the 3's and an Adcom GFA 5400 on the the 3a's. Each amp delivers 200 watts into 4 ohms, and have a similar sonic signature to each other.   Again, the results were very pleasing. 

Sometimes I like to listen to either the 3's or 3a's separately and I can easily do that using either of the above arrangements. But I like being able to use both pairs of speakers as well, as they are great speakers. They are also very heavy and not easy to move in and out of the system. With the current set up, I'm able to enjoy both simultaneously, or separately. For me, that's what's important. 

 

 

[lARrybody]

When I finished my second set of 3a's stacking was my ultimate goal. The speakers themselves were very close as far having identical crossover components. The woofers were slightly different (one set being Tonegen replacements), but they had the same surrounds. The tweeters and mid-ranges are of the same design. I knew that using one amp was out of the question and I considered a couple of Crown  XLS 2500 amps. Finally settled on two Adcom GFA 555II amps with a y split on the outputs of the preamp. Stacked them vertically (about 11 in off the floor) with the top set inverted.  The bass was almost too much. Rattling the china in the dining room hutch. Listened for about month before I swapped them out. Maybe it was the room, maybe overkill, but it really was a bit of a let down.  Currently have  a set of fives stacked on some 2ax's in the same arrangement. I like how they complement each other.

[samberger0357]

Wonder why you thought that you needed two 2500's? One amp can safely get down to 2 ohms, and generate 1200 watts doing it. More then enough to drive 4 3a's. 

 

Those 555II's are nice though. 

[lARrybody]

As my mom used to say to me, "What were you Thinking?"  Had this idea to bridge both amps into mono blocks. Crown had a promotion on them last summer and Parts Express had a 10% coupon.  The this guy on craigslist puts up two 555II's that had been recently recapped. Drove 50 miles and saved at least $300.00 over the 2502's. The Adcom's don't even have a scratch on them. Probably put out over 300 watts into a 4 ohm load.  Will try the 3a's again in the larger family room. Maybe stack them horizontally like yours.

[samberger0357]

325 watts to be exact. I'd love to have a pair, or even one. I really like my GFA 5400. 

Interesting response that you got with the 3a's, but sometimes there's no telling what will sound good to somebody, and won't to somebody else. The pairing that you have now sounds like a good one in that both speakers have qualities that compliment each other. I think that, potentially, is the benefit of stacking. But it takes experimentation, which of course can be the fun part. 

[Jeff_C]

I would wire up two sets of near identical speakers in series. This would give the amp a lot easier load. Two 4 Ohm speakers in series will result in a nominal 8 Ohm load. Has anyone tried this arrangement? You will lose a bit of available power, but if there is plenty there in the first place, the benefit of giving the amp an easier time will outweigh the loss of a bit of power.

[Rich W]

15 hours ago, frankmarsi said:

1-18-17 2P.M.EST

All this mention of ‘stacking’ is misleading. Unless done properly, it’s just a waste of time and space with inherent pitfalls and an amateur’s attempt at something more that really isn’t with-in the confines of an audiophile’s better listening perspective.

Going back as far as 2004 I believe I was one of the only ones on this site to mention it as I was using four ‘stacked’ LST’s. Later on, I tried stacking four 3a’s along with two PL-400’s, my results were disheartening.

Although stacking speakers is nothing new, it must be done correctly to fully appreciate it’s benefits.
One notable successful stacking arrangement is accomplished years ago with Advents driven by two Phase Linear PL-400 amps, do a search and see. Here the stacking is well realized as the Advents have a more forward mid and high frequency output and the woofer is crossed-over at a higher frequency.

A while ago, RoyC mentioned about the overly dominant bass that is rendered, especially with 3a’s.  Of course, he is correct!

First off, exact matching speakers and amplifiers is of the utmost importance and necessity.
I’ve read of people doing it with mismatched speakers and woefully inadequate amplifiers, an amateur’s foray at best. This use is a sorrowful attempt at trying to increase the sound-field but, doing so only gives forth an unbalanced and inaccurate sound as a result with no more than a 3db. increase in volume if using everything as matched.
Also, proper room set-up is paramount as over-powering a room may be the result unless correct guide lines are utilized and followed. Room-damping is advised and using proper sound/bass/ ‘traps’ and certainly even the arrangement of furniture comes into play.

In vain attempts to ‘stack’ their speakers some folks are even using a single amplifier of inadequate power, that in of itself is a recipe for a blown amplifier with-in a short amount of time as 3a’s are a difficult speaker to drive in the first place. Using two different amplifiers of different specifications makes no sense at all!

FM
Further reading:

https://www.reddit.com/r/audio/comments/1zgi4t/what_are_the_pros_and_cons_to_stacking_speakers/

http://forums.stevehoffman.tv/threads/do-you-recommend-hooking-up-4-speakers-in-a-two-channel-stereo.262276/

Excellent post.  While stacking seems like a good idea, the interactions it creates amongst various drivers, especially in three-way systems, yields a haphazard and unintentional positive result at best, and a blurring and loss of resolution and timbre at worst. 

While I haven't had any experience in stacking high-end AR speakers, such as the LST and 3a, I have on several occasions attempted to stack pairs of AR 8" woofer models (in particular the AR-18), and consistently experienced less than ideal results.   The stereo image and sound field didn't seem plausable as a reproduction of a live event (note my bias as primarily a classical music listener), being somewhat indistinct and unfocused.

Much has been written in these pages about driver interaction and lobing effects within a single speaker. especially with our beloved classics. We're really in uncharted territory when these interactions are increased exponentially as a result of stacking.  In addition to driver interaction, the room, and its accompanying boundary interaction with the speakers themselves plays a large part in whether the stacked approach will yield positive results.

This is not meant to disparage the practice of stacking speakers  - just my own experience and what I believe to be the potential sources of problems.  It's a practice that has to be evaluated on a case by case basis, with the listener being the ultimate arbiter.  

Rich W

[samberger0357]

4 hours ago, Rich W said:

Excellent post.  While stacking seems like a good idea, the interactions it creates amongst various drivers, especially in three-way systems, yields a haphazard and unintentional positive result at best, and a blurring and loss of resolution and timbre at worst. 

While I haven't had any experience in stacking high-end AR speakers, such as the LST and 3a, I have on several occasions attempted to stack pairs of AR 8" woofer models (in particular the AR-18), and consistently experienced less than ideal results.   The stereo image and sound field didn't seem plausable as a reproduction of a live event (note my bias as primarily a classical music listener), being somewhat indistinct and unfocused.

Much has been written in these pages about driver interaction and lobing effects within a single speaker. especially with our beloved classics. We're really in uncharted territory when these interactions are increased exponentially as a result of stacking.  In addition to driver interaction, the room, and its accompanying boundary interaction with the speakers themselves plays a large part in whether the stacked approach will yield positive results.

This is not meant to disparage the practice of stacking speakers  - just my own experience and what I believe to be the potential sources of problems.  It's a practice that has to be evaluated on a case by case basis, with the listener being the ultimate arbiter.  

Rich W

In my situation, if I was experiencing the negative qualities that you did, or the OP describes, I wouldn't do it. As your last sentence summarizes, the listener has to determine if their own experience is positive or not. I know that I've had years of listening to determine what constitutes a positive or negative listening experience. Perhaps one difference in my situation are because my speakers are horizontal? Or as I described in my earlier post that the sonic qualities of each speaker compliment each  other. 

 

6 hours ago, Jeff_C said:

I would wire up two sets of near identical speakers in series. This would give the amp a lot easier load. Two 4 Ohm speakers in series will result in a nominal 8 Ohm load. Has anyone tried this arrangement? You will lose a bit of available power, but if there is plenty there in the first place, the benefit of giving the amp an easier time will outweigh the loss of a bit of power.

'Certainly an option. Using a high power pro amp like the Crown XLS1000 takes away any worry about amp strain for me.

[Rich W]

1 hour ago, samberger0357 said:

In my situation, if I was experiencing the negative qualities that you did, or the OP describes, I wouldn't do it.As your last sentence summarizes, the listener has to determine if their own experience is positive or not. I know that I've had years of listening to determine what constitutes a positive listening experience or not. Perhaps one difference in my situation has because my speakers are horizontal? Or as I described in my earlier post that the sonic qualities of each speaker compliments each  other

I think your horizontal placement is exactly what makes your setup work.  I didn't try that with my AR18s.   Are your woofers lined up vertically, or staggered to left and right? 

[samberger0357]

22 minutes ago, Rich W said:

I think your horizontal placement is exactly what makes your setup work.  I didn't try that with my AR18s.   Are your woofers lined up vertically, or staggered to left and right? 

Could be. When I read about others experience regarding stacking, both positive and negative, I don't think I've read many, if any, that were going horizontal. It's probably not right for a lot of speakers anyway, but the 3's/3a's obviously were designed for this application, just as they were also designed to be stuck into book shelves in tight quarters.

The woofers are lined up vertically. I have them on the inside now. Experimented with them on the outside, but determined through experimentation that tweeters on the outside extended the soundstage, which I prefer. 

 

[AR surround]

I tried stacking a pair of Boston A-40's.   I tried to use the two of them as a center channel speaker.   The comb filtering was really awful, so I dispensed with the idea and went with a single, larger A-60.