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Would you consider doing this? Yea or Nay

107.10.56.175

Posted on January 5, 2017 at 21:21:22
Tidycat1
Audiophile

Posts: 311
Location: Brecksville
Joined: June 18, 2013
I have been using two pair of the KEF ls50s,stacked by inverting the top pair and running them at 4 ohms.
My thought was to run two more pairs,in a series-parallel configuration,in a line-source.(4) LS50s per side,giving an 8 ohm load.
The (2) per side has increased the image size and goes reasonably deep (not subwoofer land,but).
Which was my concern when listening to a single pair.
I realize they would need to be aligned properly and a sub would still be necessary to produce the lower octaves.
My question:Why not and what subwoofer system would you suggest.
The Primaluna only has a summed mono output,so I would need to use a powered sub with high level inputs (speaker).
Any thoughts???
Thanks to all who venture an opinion and make suggestions.
Tom:cat

 

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RE: Would you consider doing this? Yea or Nay, posted on January 5, 2017 at 22:17:00
mrdavis842
Audiophile

Posts: 257
Joined: February 22, 2013
Nay for me - Two pairs of KEF LS50 = $3,000; Four pairs = $6,000, I'm sure you can find a pretty decent pair of floor standers for that price and they may not even require a sub and at the same time eliminate all the hassle and wiring, etc.

 

RE: Would you consider doing this? Yea or Nay, posted on January 6, 2017 at 05:38:43
hahax@verizon.net
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Interesting. A friend did that decades ago with Dynaco A25s but he did it putting the speakers horizontally to make 2 line sources, one of woofer/mids and one of tweeters sort of like the Pipedreams speakers many years later which he was one of the designers. This format will produce nicer interference affects between drivers and there is no way to get rid of theses affects, just to minimize them. I'd add that years later he believed that a line source should be much longer than just the four driver arrays to really get all the line source benefits.

But, f course I forgot the KEFs are concentric drivers so the above only is meaningful for conventional speakers. However another of the Pipedreams designers has since designed a line source where the tweeters are directly in front of the main drivers, concentric but not as well integrated as the LS50 and the system works quite well.

 

Nay, posted on January 6, 2017 at 06:02:58
Dave_K
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If you're interested in a line array, try a real one.

In a line array, the spacing between drivers is important. For far-field listening, the center to center spacing should be less than the wavelength of the highest frequency to be reproduced by the drivers. For near-field listening, a better rule of thumb is half the wavelength of the highest frequency. Neither of these conditions can be met by stacking LS50s.

Given the LS50 is 302mm high and 200mm wide, if you stack them top to bottom then the maximum frequency that they operate properly as a near field line array is approximately 570Hz. Or if you turn them on their side, approximately 860Hz. In the far field you can double that. So stacked LS50s in the far field are only going to work like a line array through the bass and lower midrange. In the upper midrange and treble they are going to act like a bunch of point sources producing an interference pattern.

A practical line array for home use will have multiple vertical line sources, preferably three (bass, mid, treble), with different driver spacing for each line source. To meet the vertical spacing requirement in the upper treble requires ribbons or special tweeters that can be stacked edge to edge.

One of the main advantages of a well executed coaxial driver design like the LS50s is the possibility of achieving a nice uniform radiation pattern that falls smoothly off-axis. By doubling up the LS50s, you're already defeating the purpose somewhat. I would expect to hear some small but audible changes in the frequency response as you move up or down out of the horizontal plane where the drivers are equidistant. Also, I would expect the apparent increase in image size you noticed is accompanied by some loss of image focus. I think the downsides are going to become more apparent as you add more. More importantly, the bass extension of four LS50s is the same as one LS50. Increasing the number of speakers increases the max SPL but doesn't give you deeper bass (not without some equalization anyway).

Here is what I would do: If your budget is enough for 4 pairs of LS50s plus a sub, and assuming you like the sound of the LS50s, then consider a pair of KEF Reference 1s instead. They share roughly the same voicing as the LS50s but are better in every respect. Otherwise stick with a single pair of LS50s and add a pair of good subs.

 

Nay as well, posted on January 6, 2017 at 07:10:22
airtime
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the drivers are placed using a formula. It has to do with the frequency of the crossover point and it's actual sound wavelength size.

There is the phenomenon of reinforcement of sound when the crossover frequency wavelength equals the space between the drivers on the baffle, (center-to-center), and also the issue of negative reinforcement when they are half a wavelength apart on the baffle. There is also the matter of lobing when the drivers are more than a wavelength apart.

So by stacking you can not maintain those driver center to center distances. And will end up with lobbing or just crap.

Those speakers are designed quite well but not designed for that use. I never found any magic in array speakers. but I do find a good monitor/sub setup is hard to beat.

 

RE: Ney..., posted on January 6, 2017 at 08:04:07
BigguyinATL
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A coaxial speaker like the LS50's is designed to have a reasonably smooth off axis response as a function of frequency. Stacking negates that benefit.

If your goal is a broader image - use the second pair behind and outboard of your main pair of speakers...

Bare in mind I have dabled in stacked speakers back in the day... I help a guy do Stacked and inverted Dahlquist DQ10's in 1982... looked a bit daunting - wish I still had the picture. And in 1978 I set up a pair of stacked Advents - again inverted in our retail store (StereoTown DesMoines West and it actually resulted in several sales, including a stacked (4 pair) of Cerwin Vega 15 inch speakers to a Disco south of DesMoines (driven by 4 Citation 16 Power Amplifiers!).




"The hardest thing of all is to find a black cat in a dark room, especially if there is no cat" - Confucius

 

RE: Ney..., posted on January 6, 2017 at 08:31:42
mkuller
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...I had DQ-10s and modified them back in the early 1980s (TAS published an article I wrote about it).

A friend had stacked DQ-10s on a special frame and after hearing mine, he decided to sell one of the pair and have me help him do the mods.

The stacked pair provided a big sound but it wasn't very focused.

 

RE: Ney..., posted on January 6, 2017 at 09:23:11
hahax@verizon.net
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I noted the same thing on HP's idea of double Advents back in the mid 70s, more focus with just a single pair.

 

RE: Ney..., posted on January 6, 2017 at 10:20:28
airtime
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It's the break down of coherence. the distance between a driver is a measure of the frequency rolloff of the two drivers.

So a full coaxial speaker would have to have both cones within something like 4" of each other. Otherwise lobbing starts to occur.

Aaaahhhh, I remember that stacked Advent years.

 

RE: Nay as well, posted on January 6, 2017 at 12:20:53
hahax@verizon.net
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The closely bunched drivers of the Pipedreams and Scaena speakers(related designs) worked quite well. But the designers told me the line source had to be quite long, preferably more than just a couple of feet.

When the Pipedreams were first designed the expectation was decreased distortion and improved dynamics. But imaging was expected to be the main price. It turned out not to be true. The Pipedreams imaged stupendously. They were even good to the right of the right speaker(and similarly to the left, of course).

 

Nay, posted on January 6, 2017 at 12:21:16
E-Stat
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The (2) per side has increased the image size

I was quite disappointed when I heard KEF Blades. Their image size was likewise shrunken or profoundly distant, too from my perspective even if they were full range.

If you want line source performance, you'll need to get a line source! How about some six foot tall Maggies?

 

What is your objective? nt, posted on January 6, 2017 at 13:32:51
Inmate51
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Joined: July 6, 2005

 

RE: Would you consider doing this? Yea or Nay, posted on January 6, 2017 at 17:57:55
russ69
Audiophile

Posts: 922
Joined: December 13, 2009
I'm a LS-50 owner. It makes no sense to double up speakers when for the same money you can buy a better loudspeaker. The LS-50 weak point is the tweeter or lack of tweeter response. I've played with adding super tweeters to the system and it made the LS-50 into a real performer. Without some kind of tweeter improvement you are fighting a loosing battle.

 

One pair of LS50s, posted on January 6, 2017 at 18:39:04
G Squared
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A Rythmic F12 or F15 sub (depending on room size) and a line level high pass filter to roll off the low frequency signal to the amp driving the KEFs. Relieving them of deep bass duty and getting a servo sub with a built in parametric EQ will likely give you a full range sound.

 

RE: One pair of LS50s, posted on January 6, 2017 at 21:20:15
Tidycat1
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E-stat,
Did you notice the same effect when listening to the Reference 3 or 5?
If adding drivers to increase image size/height isn't a solution,then the approach of adding an out-board tweeter would fall into the "should have selected a different speaker to start with"
I suppose what I am suggesting might fall into the solutions for extending the Quad ESL 57.
You can add Hartleys or Tympani bass panels and/or Deccas /RTRs,but in the end you are trying to blend many different drivers and hope they blend properly.(Loved my 57/Tympani 3 bass panels).
Had anyone gone from KEFs uni-Q over to a Quad of any kind (2805,2905,2912)?
Tom:cat

 

RE: One pair of LS50s, posted on January 7, 2017 at 07:09:09
E-Stat
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Sorry, never heard the Reference 3 or 5.

If adding drivers to increase image size/height isn't a solution...

I think true multi-driver line arrays like the Scaena provide a very realistic perspective. As observed earlier, one must have lots of drivers put very closely together to achieve that effect.

You can add Hartleys or Tympani bass panels and/or Deccas /RTRs,but in the end you are trying to blend many different drivers and hope they blend properly.

That is always the challenge. As a coherency freak, my preference is for truly full range electrostats. Or, at least in the case of the Acoustats in the HT, one that delivers all but the bottom two octaves.

 

RE: Nay or Yeah ......., posted on January 8, 2017 at 06:21:06
A.Wayne
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There's a KEF dealer somewhere really PO with you guys about now ..... :)

 

RE: Nay, posted on January 8, 2017 at 08:41:36
hahax@verizon.net
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Be careful in judging the blades. I heard them in a living room set up done by KEF people and they were good. But my friend(who designed the original Scaenas) moved them a couple of feet and without fine tuning they were an order of magnitude better, both coloration wise and image wise. There were a few sets of suddenly bigger eyes in the listeners. My friend said he could live with the Blades(he was using large Pipedreams).

 

RE: Nay, posted on January 8, 2017 at 11:17:50
E-Stat
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I heard them in a living room set up done by KEF people and they were good. But my friend(who designed the original Scaenas) moved them a couple of feet and without fine tuning they were an order of magnitude better, both coloration wise and image wise.

Precise as they may be, a point source using a 5" driver will never have a realistically sized image to these ears.

It sounds as though I am sitting in the lobby or looking through the wrong end of binoculars.

Edit: Your story does not convey much confidence in the ability of the KEF people either. :)

 

RE: Nay, posted on January 8, 2017 at 20:35:25
hahax@verizon.net
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I suspect you and I have different ideas of what we want in a sound stage. I find large planars to produce too large an image especially on individual sources which would explain why I liked the Blades and you don't.

 

RE: Nay, posted on January 9, 2017 at 06:44:41
E-Stat
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I find large planars to produce too large an image...

We definitely have a different perspective of sound stage!

I've never heard any speaker - planar or otherwise - that creates an apparent image larger than that of a full symphony.

 

Nay, posted on January 12, 2017 at 20:04:45
thump
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NO.
i AM considering buying a pair of LS50s some day when i start building another home system and IMMEDIATELY plugging their distortion holes, i mean ports, because there just isn't an AFFORDABLE pair of quality acoustic suspension speakers priced lower.

NHT superzeros are really great sounding as long as you sub them and don't care a lot cowbells etc. sounding soft. their much more expensive classic 3 siblings are MOSTLY amazing sounding except for a slight unforgivable aluminum driver resonance signature and everything else under $1000 has lousy thin cabinets like role kayaks or the otherwise amazing sounding energy RC10s that have great drivers, but make you chose between unforgivable port resonances or cabinet resonances if you plug 'em. the KEFs have extra beefy cabinets AND "class A" drivers.

as to stacking them? NO you might get a bigger soundstage, but you totally defeat their "point source" purpose with two tweeters as well as possibly induce comb filtering effects.

if i had $3,000 to lay down on a pair of speakers, i'd probably get ATC SCM19s instead

 

RE: Nay, posted on January 18, 2017 at 14:29:46
Tidycat1
Audiophile

Posts: 311
Location: Brecksville
Joined: June 18, 2013
Thanks to all who chimed in.
Had been torn between a couple of bigger systems.Investigating Magicos,Wilson and Sonus Faber.Watched a dozen or so Youtube videos.
Then the Wyred4sound video.They were switching between the LS-50 and SF Elipsa.
Must have been a sign from above.
Spoke with Kevin/Upscale ,who had sold me the PL and Kiseki.Had a reasonably priced Elipsa.
Did some further investigation and decided to try the Elipsa SE in graphite lacquer.
Would expect that they will be delivered next week.
And the saga continues.
Tom:cat

 

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