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Murphy Corner Line Array

fluid

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I have not heard a Murphy Corner Array but my current speakers are a full range freestanding line array using 25 TC9 drivers per side. There are a few people who have made corner versions using the same or similar drivers.

They need a bucket load of EQ to wrangle them in to shape and a ton of effort to get them to sound right but when you do they sound amazing.
They are so far my preferred speaker of any that I have built or heard across all genres of music that I listen to. They cannot do quite the same as the LX521 that I had before on acoustic and lighter music which for which they were exceptional, but fell apart with hard, heavy and difficult music.

So far they are the best compromise I have found.

IMG20201204130613 small.jpg
 
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Ericglo

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Thanks.
I read some of your thread over at diyaudio.
 

Newman

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Like @fluid says, the big issue is the EQ needed because cones make a terrible line source if you want a flat FR -- not because of the discrete drivers, but because they are high mass constant volume acceleration devices.
 

fluid

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Thanks.
I read some of your thread over at diyaudio.
The thread got long and convoluted so reading it all has become difficult. If there's something specific you would like to know I'll do my best to help.
 

Joecarrow

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Why yes, I've heard a couple of pairs and helped to build them!

One thing that they do quite well is midbass. They skip the speaker boundary interface problem on the front and side walls, and they don't seem to energize vertical room modes much at all or have problematic bounce off of the floor or ceiling. Cruising right through the Schroeder frequency is something that I don't see too many speakers pull off, but I think these do it fairly well.

They do absolutely need a lot of EQ to reach an appropriate frequency response, but in my experience the horizontal directivity is wide enough that the sweet spot isn't overly small despite the ~3" cones.
 

gnarly

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I built a pair using 24 TC9's. They were built very close to Murphy's plans.

In a room corner, the lateral reflections were a problem. I think this could maybe be overcome with fully absorptive walls around the array for several feet, and/or trying to figure out how to get the drivers deeper into the corner.

They also beg for a room with two adjacent unencumbered corners, that gives the right listening triangle and distances.
I don't have such a room, so i pulled them out into rooms freestanding, and didn't bother with seeing if absorptive walls could solve the corner walls reflection problem.

They worked well out in the room. I think single driver type line arrays are naturals at making a wonderful mid-range. Truly glorious mid-range imo.
I think the single driver types suffer from a lack of bass (need more displacement than a bunch of small drivers can provide), and also lack VHF (need smaller drivers, smaller c-2-c, to deliver clearer VHF)
My 24 TC9s build definitely needed a sub. I think some folks add a lot of low end boost, but i found i quickly hit excursion limits given my listening tastes. The high end needed line-array boost of course, but not so much I felt it was a problem....other than missing some sparkle (like from a good CD).

Hope this helped...
 

hollis

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I built some (three pairs) with friends a year or so back. We took the official MCLA and shrunk it down a bit for a room that was quite size-constrained. ND-90 8-ohm drivers in series-parallel adding up to 8ohm, so if we went with the 4ohm version we could easily get a 4ohm array. The hardest part of the build was getting an air tight seal.

Unequalized, the response looks quite poor, but as the original spec calls for +20dB digital eq they can be shaped into any target curve you want. Mind you, at the cost of headroom, but these have headroom for days. Instead of the graphic eq, we went the minidsp route. These pair exceptionally well with the SHD Power. In the third image you can see we used a Linkwitz Transform, then 2x HF shelfs cascaded, then 4-6 parametrics for the worst of room peaks. All of that was topped off with Dirac.

In the last image you can see, I went for full side wall absorption. In a 12x20x8' room I have pushed them hard enough to want subwoofers, but I am planning a new build with more internal volume, ND-91 drivers, a larger amp, and better air seal.
 

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hollis

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Subjective impressions:

Holy crap I have never heard mid-bass to bass this clear. Instrument separation is nuts. "Speed" and "attack" are great. Having no crossovers at all does great things for phase (from a theory standpoint) and I think this leads to a lot of coherency. Comb filtering should be audible only when standing up / sitting down, but I cant say I have ever noticed it.

Soundstage: center is solid when placed on my 12' front wall. Width I am not a great judge of, still learning what I want to expect around that. Height, they do image a touch high according to myself and a few visitor's impressions.

Yoga impressions: damn, I have never heard such good sound quality while I roll around on the floor. HF response is solid everywhere.

Multi-seat impressions: you cant escape the sound, when you walk away the level barely drops off, so the sound seems to follow you and stay with you. The linearray cylinder radiation pattern (vs sphere) is something you really have to hear in person.
 

Newman

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Unfortunately, we get ‘mind blown’ subjective reviews for every type of loudspeaker. I am sure they are all completely genuine, but I don’t know what to tell myself I am learning from them any more.

I did a fair bit of background research on this type of speaker, and visualising how I might might use them to feature in my system, although I have not heard any example systems.

My conclusion at this point is that they have a number of challenges for someone who wants to use them at home: –
  • Lots of EQ needed, so:-
    • high power amps needed and much care with gain structure and avoiding clipping
    • off axis treble will be very unlike the on-axis HF response, since these full-range drivers are a bit beamy
  • +/-90mm full range units beam from about 5 kHz and up, making a 2-way desirable, which would also help with potential Doppler issues with a full-range driver
  • BUT… 2-way solutions
    • get pricey fast
    • laterally have all the horizontal dispersion issues of a 2-way speaker with side-by-side drivers
    • the wide dispersion tweeter is going to be closer to 1 corner wall than the other, causing some lateral reflected sound concerns
  • Needs to touch the floor and ceiling, to avoid creating a truncated line source, with all its issues.
  • Needs a hard-finish floor, to avoid creating a truncated line source, with all its issues.
  • For multichannel listening, we rapidly run into problems with space and cost. How to do a centre channel with a full-height speaker designed for a corner? Are all 4 room corners available? What if you want rear surrounds, or side surrounds, that don’t belong in corners? OTOH if you mix and match line source for the front pair with point source speakers around the room, there will be major integration issues.
  • For any kind of object-oriented music listening, there’s a big problem with integrating with the height channels.
I decided not to pursue it into the flesh, given that I see the music playback world as becoming increasingly multichannel, and I don’t want to go to an awful lot of trouble to create something that will have an increasingly restricted use for me, and that I will need another system for listening to multichannel music or upmixed 2-channel music.

cheers
 
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fluid

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I don't want to evangelise line arrays as they are not ideal for every situation that is for sure. For stereo music listening at 70 to 90dB average levels they are a worthwhile option to consider.

There are a few items in your list that are either not accurate or a very glass half empty way of looking at it.

All practical buildable arrays are truncated in some form. It is almost impossible to build them completely floor to ceiling with a totally reflective surface on floor and ceiling for the infinite array theory to hold true.

Fortunately they only need to be 70% of the ceiling height or 1.8m or taller for enough infinite line traits to emerge in the response. I agree that heavily truncated lines are a bad idea. There is a continuum and getting above the 70% gets you far enough towards an infinite line response. With a tall enough array there is effectively no noticeable floor reflection even outside.

The EQ is inescapable but the requirements can be managed, the gain structure is no issue if using appropriate software. Power will be needed but it doesn't have to be outrageous. 100 to 200W is enough depending on how loud and how much low end boost is used. Listening closer to on axis reduces the need to boost the top end as much which can free up another 3dB or so.

Beaming happens but the directivity index is smooth and climbs steadily, I don't see this as a real drawback.

There are variations such as frequency shading, expanding and fractal arrays that seek to address some of the points mentioned.

They do work well in treated and untreated rooms and you will struggle to find a speaker with a smaller footprint that is truly full range. There's enough knowledge and experience that has been shared to make getting a good result a practical reality for anyone willing to put some time and effort into it. For anyone who wants to buy a speaker and put it in a room and get good result without any real effort then look elsewhere.
 

Newman

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Personally I think the 70% rule is fake. Test: at what frequency?

I didn’t want to mention shading because it only makes a difficult enough project multiple times more difficult, and doing frequency shading without delay shading is pretty half baked.

I agree that the EQ requirements can be managed: all of the issues can be managed, such as your attempts to manage truncation with a near – enough rule, and beaming with ‘not that bad’.

But for me, it all added up to too many compromises heaped upon other compromises, to push ahead with a speaker that, in his original attraction, was all about idealistic appeal.
 

kipman725

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Has anyone built this as a two way? would seem to address a lot of the issues. The bass drivers could be larger and improve LF performance, no doppler, beaming ETC. If brickwall FIR filters are used then issues around the crossover can be kept out of the ears critical bandwidth.
 

hex168

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Personally I think the 70% rule is fake. Test: at what frequency?

I didn’t want to mention shading because it only makes a difficult enough project multiple times more difficult, and doing frequency shading without delay shading is pretty half baked.

I agree that the EQ requirements can be managed: all of the issues can be managed, such as your attempts to manage truncation with a near – enough rule, and beaming with ‘not that bad’.

But for me, it all added up to too many compromises heaped upon other compromises, to push ahead with a speaker that, in his original attraction, was all about idealistic appeal.
This Jim Griffin paper holds up pretty well for required line length vs. frequency:
https://audioroundtable.com/misc/nflawp.pdf
 
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gnarly

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Has anyone built this as a two way? would seem to address a lot of the issues. The bass drivers could be larger and improve LF performance, no doppler, beaming ETC. If brickwall FIR filters are used then issues around the crossover can be kept out of the ears critical bandwidth.

Yep. I think lot's of folks have, both DIY and commercial.
The ole Infinity IRS-V is an example, albeit it used a separate bass tower/line.

If i ever get the line-array bug again, it's what i'll do. But i'm convinced it would need to be a 3-way to for what i'd like to achieve.
A line of ribbons or <1" domes for VHF/ higher end of HF. A line of smaller cones or planars for upper bass to lower end of HF, and a line of larger cones for bass and sub.


Shifting gears, to talk about overall suitability....
I think a near floor-to ceiling line array of either single small drivers (or a 2way line etc), needs to be heard before passing any judgement.
Ime, they can do some rather remarkable things, in terms of smoothing out floor bounce, and maintaining even sounding coverage both horizontal and vertical. In-room vertical is unmatched by any design i've tried, other than a CBT (also a line array).

For me, they deliver a very nice two-channel sound, subject to the constraints i previously mentioned.
I also believe they would make ideal front and rear speakers for 5.1 home-theatre, allowing more seats to have great even surround coverage.
(I'd put a synergy in as the center channel, with the right H-V pattern to hit all seats.)

My 2c......The two types of speakers i believe have the most in-home promise, are synergies and line-arrays, in that order.
None of the problems i've read about line-arrays seem to be all that much, given their patterning ability indoors.
 

ppataki

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This might be a dummy question but what about sound stage depth when using these line arrays in the front corners?
Will there be any depth at all? I am asking as based on my experience the further away the speakers are from the front wall the deeper the stage will be and these speakers are anything but away from the wall
Thank you
 

BenB

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This might be a dummy question but what about sound stage depth when using these line arrays in the front corners?
Will there be any depth at all? I am asking as based on my experience the further away the speakers are from the front wall the deeper the stage will be and these speakers are anything but away from the wall
Thank you

If there's no depth in the source, on-wall speakers wont add depth the way floor standers do. If there's depth in the source, it wont be confused by the front wall reflection, and will be perceived as more natural.
 
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Ericglo

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Thanks!

I have read all of the responses, but I have been so tired that I haven't been able to digest it all.

I realize that there are issues with the driver Murphy used and high frequencies. I believe that is why Don Keele originally used the very small tweeters in the CBT36 that Rick Craig said were inadequate. In the Epique CBT, Don went with a single driver and seemingly had good results. I heard the Epique once at Cedia and thought it was impressive for what it did.

I thought about making an attempt, but with a different driver. I know Dennis used the Tectonic 46 with great success. Erin tested the 35 a couple of years ago. It could maybe be an alternative although having trouble filling in the bottom end.
https://www.parts-express.com/Tecto...MIgp7Uj8v18QIVAsGGCh3UKwRDEAQYAiABEgL12_D_BwE

https://www.erinsaudiocorner.com/driveunits/tectonic-elements-tebm35c10-4-miniature-bmr-driver/
 

Newman

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I realize that there are issues with the driver Murphy used and high frequencies.
Quite right, but as Roger Russell would have said, paraphrased, “nothing to see here, I see line source speakers that break all the rules and sound juuuuust fannnnnntastic.” Which takes me right back to the first line of my first comment: we get ‘mind blown’ subjective reviews for every type of loudspeaker.

Either you stick to the ideals, and go for it, or start clattering your way down tin can alley with compromises that ‘sound fine’. I’ve seen all the same claims about horn speakers, how they can be compromised every which way and still be the best thing since sliced bread. Eventually, you realise you are dealing with fans.

cheers
 
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