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Multi-Way Conventional loudspeakers with crossovers

Line array surrounds or point source?
Line array surrounds or point source?
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Old 4th March 2012, 11:43 PM   #1
mazeroth is offline mazeroth  United States
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Default Line array surrounds or point source?

I love large line array speakers and have built a few over the years. I recently found two designs where small full-range drivers were used to cover the entire audio bandwidth and EQ was applied to mitigate the effects of comb filtering since tweeters were not used:

http://www.humblehomemadehifi.com/do...eline_copy.pdf

The Murphy Corner-Line-Array Home Page

This got me thinking. Line arrays cost a lot of money to build due to the number of woofers and tweeters used. However, with the above designs costs would be significantly less than a conventional line array. This was great timing as I just finished framing my dedicated basement theater and was working out which speakers to use for it. I'm on somewhat of a budget for this project, not wanting to spend more than $3000 on projector, speakers, electronics etc.

After some looking around I found that Madisound has essentially the same driver that John Murphy used on sale dirt-cheap at $9 each in 50+ quantities:

Aurasound NS3-193-8A1 3" Black Cone wide range: Madisound Speaker Store

So what did I do? What any nut would do and purchased 110 of them! I have a computer dedicated to speaker measurements with a calibrated microphone and some great software (LspCAD, SoundEasy, ARTA etc.) and recently built a mini 4 driver array with these drivers to test out my plan. They sound great! For the final system I'm thinking 20 drivers for the LCR and surrounds can be built using 6 drivers. I won't need a ton of dynamic headroom out of the surrounds as the room is small at 17 x 11.5 x 7.5h so 6 drivers in the surrounds should suffice. I will listen to LOUD music down there on occasion so I will blast the 20 driver arrays from time to time. Oh, and the sub will be an IB with a quad of Dayton RSS390HF 15" subs, which I had in a previous IB.

Now that you know my whole life story, here's my problem. I've not had a surround setup yet and didn't read up on placement until recently and from what I'm reading you should have your surrounds a couple of feet above your listening position. If I did this with my mini arrays the lowest driver would be above my ears and therefore, since arrays have very limited vertical dispersion, the high frequencies would be just about gone. If I moved them down some so at least the bottom driver was below my ear then the high frequencies would be just fine. Measuring the mini arrays at 1 meter with the mic just below the bottom woofer after 1khz. the sound drops off pretty fast and is very easy to hear. I do like that arrays have limited vertical dispersion so they interact with the room a lot less than standard point source but I'm thinking this might not be ideal for a surround application.

I'm a DiYer at heart but after looking around for affordable in-wall surrounds on DiY forums they really don't exist under $150/each. Wanting to go crazy in this theater with Audyssey DSX and 9.1 that would be over $900 just for surrounds. I then Googled and found people really like the inexpensive speakers from Monoprice and found these beauties. I can't believe I'm even considering them, but for the price they may be tough to beat. It's nice that I can buy a pair and measure them for linear and nonlinear distortion before committing to buy all 6. Even if linear distortion is off some the receiver I'll purchase will have at least MultEQ XT which will correct for that.

For only $78.59 each when QTY 50+ purchased - 8 Inches Kevlar 3-Way High Power In-Wall Speaker (Pair) - 100W Nominal, 200W Max | 8 Inches In-Wall / In-Ceiling Speakers

Alrighty, I think I've said enough. Any and all input is GREATLY appreciated!
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Old 5th March 2012, 06:35 AM   #2
mdocod is offline mdocod  United States
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Having a dedicated listening room, with, what I assume to be sound absorbing walls and ceiling and floors and such, the combing becomes MORE noticeable because there is nothing reflective to smear the effects of it around. Even if you did aim the lines at the listening position, I fear there would still be very annoying lulls through the high frequency.
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Old 5th March 2012, 09:32 AM   #3
MaVo is offline MaVo  Germany
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You could allways do a quick and dirty test, where you place a cheap single speaker at the surrounds position, one time a few feet above head level, one time level with head. Then decide if the "surround should be above head level" advice is actually necessary for yourself. Taste does matter after all.
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Old 5th March 2012, 12:33 PM   #4
DrDyna is offline DrDyna  United States
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Hm, I thought that the extra 2 channels for 9.1 were not surround channels, but could be used for Z (height) or L and R wides?

You should still only have 4 surround channels, SB, SR, SBR and SBL. I'd recommend buying (or building) bipole surround speakers such as these:

https://sites.google.com/site/undefi...bipolewhatwhen
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Old 5th March 2012, 04:46 PM   #5
Speedskater is offline Speedskater  United States
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The real first question is:
Are you thinking of a older diffuse surround sound system?
or
A modern multi-channel discrete sound system?
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Old 5th March 2012, 05:42 PM   #6
mazeroth is offline mazeroth  United States
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mdocod, I see what you're saying. I will say that the mini array I built sounds great to my ears even without EQ. Measuring it the response really doesn't begin to fall off until 12 khz, which surprised me, and the falloff was gradual. This theater will not be for the ultimate in SQ but for high dynamics and wow factor. I have a 2-channel system for critical listening. The front of the room will likely have a layer of 2" to 4" OC 703 behind a false wall where the screen will be mounted. Around the room I will have wall treatments that will act as sound absorbers and to hide the surrounds.

MaVo, I thought about doing that but figured it would be difficult to achieve a true sense of how the whole system would sound. It would be much easier to decide if I had a full surround setup that I could listen to at ear level and then, say, 2 ft. above ear level. I could easily place a speaker at 5-6 ft up a wall but I have a good idea of how that will sound; like a speaker placed high. For envelopment, I'd need more channels and I only have 2 bookshelf speakers to play with.

DyDyna, Yes, I will be using wides for the 9.1 setup. I can not use bipolar speakers as these must be in-walls but thanks for the suggestion. I know Paul personally and he does design some great, budget speakers.

Speedskater, I am talking about a modern, multi-channel discrete system.

I don't have a ton of money but like going over the top. That's what got me into building speakers. I like rock and heavy metal and wanted monster speakers about 10 years ago and saw a pair of line arrays on the net. I was hooked. I can't just build something that isn't over the top!

6 foot tall mains - check
9 channels of audio - check
Four 15" subs in IB - check
110" screen 1080p - check
Wife that thinks I'm crazy - check

Thanks for all the input so far. I really appreciate it!
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Old 5th March 2012, 05:55 PM   #7
Speedskater is offline Speedskater  United States
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For a modern, multi-channel discrete system, I'd chose rather directional loudspeakers. The older diffuse surround sound systems often used dipoles to spread the surround sound around, so that you could not locate the source.
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Old 5th March 2012, 06:47 PM   #8
mazeroth is offline mazeroth  United States
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Quote:
Originally Posted by Speedskater View Post
For a modern, multi-channel discrete system, I'd chose rather directional loudspeakers. The older diffuse surround sound systems often used dipoles to spread the surround sound around, so that you could not locate the source.
My thoughts exactly, which is kind of why I wanted to go with the arrays as they would be extremely directional.
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Old 6th March 2012, 03:19 AM   #9
mdocod is offline mdocod  United States
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The arrays will have vertical dispersion control, but the horizontal dispersion will vary from very wide to very narrow and full of lulls through the listening range. Personal opinion is that the wide variation in dispersion control and combing issues are a net loss over a traditional attempt at achieving something that behaves more like a point source. My personal opinion is that, the ideal "home brew" theater speakers would be relatively uncomplicated 2-ways utilizing a medium to wide dispersion compression horns crossed to 6-10" size pro-sound mid-bass drivers. Horn dispersion and woofer size would be matched to have similar dispersion at x-over, and those characteristics would be chosen based on the size of the room and distance the speakers are from the listener.

How were you planning on orienting that center channel 20-woofer array? Sideways?
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Old 6th March 2012, 11:33 AM   #10
flg is offline flg  United States
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Horizontal dispersion for the line will be the same as an individual driver. Vertical dispersion is where the line shows some good characteristics and those nasty lobes, nulls, etc.
However, Much reading will turn up reviews of many line projects where the loobing is not noticeable???
Here's one more; Roger Russell, McIntosh Lab., Scripto and Norma Pencils and leads
Here you can find much info on coloumn speakers, the IDS system, and alot more. We actually have Roger's succsesor at Mac on this forum occaisionally
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