Murphy Corner Line Array (MCLA)

[Chris Roemer]

Re: Murphy Corner Line Array (MCLA)

Hi, I am new to this group...

I am intrested in making these also... but I have the same issue as another member, i quote:

"I've had the MCLA's running for 4 days now but my first impressions have not been that great, mainly because of the distance between corners in my room. My corners are 17 ft. apart along my front wall, and my listening position can be 12 ft. max back from the front wall. As a result I'm getting too much separation between the left and right channels.

In the MCLA article, I can't see where John mentions anything about optimum spacing between speakers. I don't have any experience with using equalizers. Would optimum equalization settings minimize this problem?"

In my case I have no choice but to have the speaker further apart than I will be sitting. Will this make this design reduntant? or using could using other features of the equalizer help.

You'll probably get more responses, but most traditionally, the best stereo listening occurs at a distance back that's from about 1x to 2x the speaker separation. In order to use some "corner line arrays", I'd think that they were designed to be used in the corners on the short wall.

chris

[oodesigns]

Re: Murphy Corner Line Array (MCLA)

Thanks Chris

I was just woundering if there where any electronic ways to improve perceived stereo, when sitting close to speakers.

[Chris Roemer]

Re: Murphy Corner Line Array (MCLA)

Thanks Chris

I was just woundering if there where any electronic ways to improve perceived stereo, when sitting close to speakers.

I think on some boomboxes there's a "Wide" switch that must throw (only) the tweeters out of phase to "spread" the sound. It's not right, though.

Chris

[John L. Murphy]

Re: Murphy Corner Line Array (MCLA)

Hi, I am new to this group...

I am intrested in making these also... but I have the same issue as another member, i quote:

"I've had the MCLA's running for 4 days now but my first impressions have not been that great, mainly because of the distance between corners in my room. My corners are 17 ft. apart along my front wall, and my listening position can be 12 ft. max back from the front wall. As a result I'm getting too much separation between the left and right channels.

In the MCLA article, I can't see where John mentions anything about optimum spacing between speakers. I don't have any experience with using equalizers. Would optimum equalization settings minimize this problem?"

In my case I have no choice but to have the speaker further apart than I will be sitting. Will this make this design reduntant? or using could using other features of the equalizer help.

oodesigns,

I'm glad to hear you are interested in building your own MCLAs! Now, regarding your concerns... If stereo loudspeakers are spaced too wide the image will draw to one side very quickly as you move away from the center line making for an unstable image. The wider the speaker’s angle of separation the worse this effect will be. In general the MCLAs seem to provide a wide sweet spot but like any speaker, if they are spaced too far apart the imaging can become unstable.

I have my MCLAs placed across the narrow end of my 11.5 'x 27' room with my listening distance ranging from 5 feet (playing guitar) to 25 feet when listening at the very back of the room. They are consistent sounding all around the room but the sweetest area for listening to stereo recordings is the range from about 8 to 12 feet from the front wall. Because of the 45 degree angle of the enclosure the arrays axis cross at half the separation distance or about 5.75' in my case. A distance of 8' is about the forward limit for critical stereo listening and provides the widest sound stage I would want to hear for any extended time. The traditional "equilateral triangle" listening distance is 10' (.866 x separation distance) for my setup. Listening at 10' is very enjoyable and provides the traditional (60 degrees wide) stereo sound stage. At progressively greater listening distances beyond 10' the sound stage grows narrower but the imaging remains excellent. Even from the back of the room the arrays convey strong imaging with performers locations remaining firmly defined as you move about. If I had to pick a single listening position it would probably be the traditional equilateral triangle geometry at 10'.

The member you quote above, Geo had the arrays 17 feet apart with vaulted ceilings. I could not tell if he was using the Behringer EQ or not. Without the EQ the arrays are muddy sounding and certainly are not very impressive. He said he could listen at a maximum of 12 feet back which is less than the equilateral triangle distance of about 15' (for his setup). I would expect them to sound excellent even if the image was a bit wide. I wonder if a listening distance of 12' placed him right at the rear wall of the room. The vaulted ceiling would definitely not give the infinite line reflections you get when the ceiling is parallel to the floor. My first thought is that this room would likely reduce the low frequency output compared to the same room with ceiling parallel to floor.

Geo, can you tell us more? Did you EQ the system using the Behringer EQ? Of the three settings I give (flat, Sm Rm-X and X curve) which did you try?

Getting back to oodesigns questions...you said that you not sit as far back as the speakers are separated. That might be OK. For equilateral triangle listening geometry you only need to sit at a distance of .866 x separation, that is, a bit less than the separation distance. So your setup might be just fine. What are the actual distances for your room?

Regards,

John

[John L. Murphy]

Re: Murphy Corner Line Array (MCLA)

Hi John,

Just curious if you've had the chance to experiment with sound absorbing materials on the walls adjacent to the line arrays to see what impact it might have on imaging, tonal balance, and a sense of depth.

Having experimented a fair amount myself with line arrays, I agree wholeheartedly with some of your earlier observations about the actual percentages of direct/reflected sound in point source configurations versus line source. Given the comments I've read in various places, I think this aspect of line arrays is one of the most overlooked - concentrating the source of excitation in one place in most real environments produces greater contrast in both reflection time and intensity - often making reflected energy more noticeable.

auracle,

No, actually I have not experimented with absorbers in the room at all. The room is fairly live but with a pleasing sound that I actually allow to leak into my acoustic guitar and vocal recording tracks. So I have not felt a need to tame any reflections up to this point.

Regards,

John

[John L. Murphy]

Re: Murphy Corner Line Array (MCLA)

I think on some boomboxes there's a "Wide" switch that must throw (only) the tweeters out of phase to "spread" the sound. It's not right, though.

Chris

In this case oodesigns might need a "narrow" switch to try to compensate for the wide placement. It occurs to me that a partial blend to mono might help but even that would not help the case of a centered vocal which is sucked to the side too rapidly as you move off axis of too widely spaced speakers.

It actually sounds like oodesigns has just adequate separation to achieve an equilateral triangle listening setup. That should not be too wide.

Thanks for the comments Chris.

Regards,

John

[oodesigns]

Re: Murphy Corner Line Array (MCLA)

Hi, John

thanks for the information I will be anaylizing it more carefully.

My room is pretty small about 360cm * 270cm - I based in the uk where the rooms are not big!.

One thought I had off the top of my head was to angle the speakers at greater than 45 degrees towards the center of where I will be (standing or sitting) .

The way I thought was to base the cabinet on a pipe which can be rotated, or would the completly destroy the whole concept.

plus as I am sooo close to the speakers would it be helpful to phase correct each driver based on my location, this would occur a cost of a electronics per speaker (ie active time alignment - with a small amp per speaker - this might be a bit nuts but then a system with 25 drivers per unit is quite over the top any way).

[John L. Murphy]

Re: Murphy Corner Line Array (MCLA)

Hi, John

thanks for the information I will be anaylizing it more carefully.

My room is pretty small about 360cm * 270cm - I based in the uk where the rooms are not big!.

One thought I had off the top of my head was to angle the speakers at greater than 45 degrees towards the center of where I will be (standing or sitting) .

The way I thought was to base the cabinet on a pipe which can be rotated, or would the completly destroy the whole concept.

plus as I am sooo close to the speakers would it be helpful to phase correct each driver based on my location, this would occur a cost of a electronics per speaker (ie active time alignment - with a small amp per speaker - this might be a bit nuts but then a system with 25 drivers per unit is quite over the top any way).

It sounds like nice intimate setup for listening to music!

You would want to place the arrays in the narrow corners of the room 270 cm apart. For my 45 degree enclosure the axis of the two enclosures would cross at 135 cm from the front wall. The equilateral triangle setup would place you back (.866 x 270 =) 234 cm from the front wall. Your room would seem to be a good candidate for the MCLA.

There is no reason not to experiment with the angle of the enclosure in the corner. Basing the enclosure on a pipe makes sense. Note that you may well end up with a different enclosure volume per driver which would affect the required corrective EQ.

For a similar pipe enclosure design see Darren Kuzma's line array project using a 4 inch pvc pipe as the enclosure:

http://www.partsexpress.com/projects.../Kuze3201.html

Considering the reflected images of the arrays in the floor and ceiling I don't think it is desirable to apply delay to any of the drivers. I actually tried the experiment of delaying the signal to drivers in my MLA8/16 arrays back in the 1980s. I never found a delay configuration I liked better than the un-delayed array. For example, if you attempted to focus the array at the listening position each reflection of the array would be miss-focused and spoil the whole plan. Likewise with amplitude tapering the array; each reflection would also be tapered messing up the whole tapering arrangement.

Let us know how your project progresses.

Regards,

John

[oodesigns]

Re: Murphy Corner Line Array (MCLA)

Thanks John for the information

One Question about the "Behringer Ultra-Curve Pro DEQ2496." my better half would like to know if the rack mounts can be taken off as she thinks they do not look good, if not I will have to look for a small 1 unit high case.

[John L. Murphy]

Re: Murphy Corner Line Array (MCLA)

Thanks John for the information

One Question about the "Behringer Ultra-Curve Pro DEQ2496." my better half would like to know if the rack mounts can be taken off as she thinks they do not look good, if not I will have to look for a small 1 unit high case.

I checked my unit and the rack mount ears are part of the chassis...so no, they are not removable (unless you want to look inside the chassis).

Regards,

John

[bekeys88]

Re: MCLA use pro-audio (PA application)

Another post referenced the suitability of using these for a small club PA (for vocals & keyboard). I'm looking to try & duplicate what Bose has done with their L1 system. This design looks like it should do it. Question: Since portability is an issue, what would be the minimum # of driver's I could get away with and still get the line array effect (I'm looking to try and get equal volume levels regardless of where one stands in the room.... or at least thats what Bose is claiming the L1 does). In my case, the cabinets would be stacked (using the minimum speaker concept) for bigger venues (and at the small venues the "extra" columns might be used as monitors on their side in the front of the stage.
Thanks....... great info by the way.........

[Ray Tremblay]

Re: Murphy Corner Line Array (MCLA)

Has anyone built one of these yet? Pics?

[John L. Murphy]

Re: MCLA use pro-audio (PA application)

Another post referenced the suitability of using these for a small club PA (for vocals & keyboard). I'm looking to try & duplicate what Bose has done with their L1 system. This design looks like it should do it. Question: Since portability is an issue, what would be the minimum # of driver's I could get away with and still get the line array effect (I'm looking to try and get equal volume levels regardless of where one stands in the room.... or at least thats what Bose is claiming the L1 does). In my case, the cabinets would be stacked (using the minimum speaker concept) for bigger venues (and at the small venues the "extra" columns might be used as monitors on their side in the front of the stage.
Thanks....... great info by the way.........

Hello bekeys88,

As a permanent installation in a small club with parallel ceiling and narrow wall at the front I think they would do quite well. The higher the SPL required the higher you would want to set the -3 dB corner. The sound coverage about the room would likely be very even without blasting the folks in front.

As a portable system you may not be able to place them in the corners as you would like. Also, for a performing artist, the room-of-the-night may not even have its ceiling parallel to the floor. I expect there would be a lot of variation in the bass output from room to room for starters. You would want some flexibility in voicing. The MCLA EQ would be no more than a starting point.

In order to get the "infinite" line array effect of the MCLA you would need enough drivers to cover about 90% of the floor to ceiling distance. I would keep the drivers tightly spaced. Stacking multiple smaller arrays would be the best way to keep it portable and adaptable to each room.

Regards,

John

[John L. Murphy]

Re: Murphy Corner Line Array (MCLA)

Has anyone built one of these yet? Pics?

Hi Ray,

So far, besides my own initial prototype pair, only one other person (Geo) has confirmed that they have built them. He gave us a preliminary report but we never got a follow up report or details of the setup.

I anticipate building a second pair to use as my home theater front mains but I'm hoping to find a source to fabricate the enclosures...so I don't have to cut all those 3" holes again.

I have construction photos which I have not yet posted but I suspect you want to see pretty finished product photos. My prototypes would not win any beauty contest because they are simply wrapped in black grill cloth. I'll think about it...

Regards,

John

[Ron_E]

Re: Murphy Corner Line Array (MCLA)

Can I assume a MCLA would work as a sub-woofer? I'm thinking about putting eight 8" woofers in the front corners of my listening room.

Ron