Grateful Dead Music Forum

A place to talk about the music of the Grateful Dead 

 #122717  by Rick Turner
 Thu Jan 03, 2013 12:22 am

When I worked up a lot of the Wall of Sound speaker cabinet dimensions, I used the cube root of 2 (1.25992105) as the multiplier to determine the ratio of depth to width to height of the cabinets. Take your smallest dimension and multiply it by that, then take that result and multiply it again by that constant. The idea (for better or worse...) was to spread any standing waves out equal distant from one another in the audio spectrum. There are other formulae that some folks use...Golden Mean, etc.

We also used heavy rug padding with horse hair in it to damp internal reflections.

We went with closed boxes because the transient response is better than with bass reflex designs, and the deep low end extension is better way down there, though they start rolling off a bit sooner than the bass reflex. But then when stacked in the tall array, that low end comes off better because it's better directed.

Bear did the design of the big curved arrays.
 #122720  by ugly rumor
 Thu Jan 03, 2013 3:12 am
Does that apply to the bass cabinets, also? I am currently researching a cabinet for a Meyer HMS-15. It currently resides in a Fender mid-'80s "folded horn" cabinet, but that cabinet loses the highs above 150 hz. Thanks.
 #122733  by Rick Turner
 Thu Jan 03, 2013 9:11 am
We used that formula for any sized speaker.

I don't know that driver...I'm assuming it's a 15", and if so, I'd not expect it to be designed for much in the mids or highs. JBL (D-130, etc.) seems to be the only company that really tried to make a 15 with much in the way of mids. There was that two way hi-fi cabinet they made with the D-130 and an 075 bullet tweeter that was all the rage in about 1965. It was crossed over at about 2,400 Hz.
 #122763  by Sparechaynge
 Thu Jan 03, 2013 4:58 pm
Not that I doubt Bear's design, but wouldn't the clusters for the vocals and piano comb-filter like mad?
 #122821  by Rick Turner
 Sat Jan 05, 2013 12:48 am
There was probably some comb filtering, but there were no acceptable alternatives at that point in time. Horns all suffered from throat compression was John Meyer who finally figured out how to deal with that. We preferred the sound of cone drivers all the way up to the top where we used the EV T-350s driven by tube amps...the Mac 350s. The cones of the 12s and 5s were so tightly packed together that they really did tend to act as driver masses.

Bear in mind (pun intended) that we were doing the best we could with what was commercially available at that moment in time, and it was damned good. I've still never heard a system that comes close to what the WOS could do on a good day. The use of line arrays that were based on actual wave length theory really worked. Many modern line arrays ignore that whole thing...stepping down the height of the columns as frequencies go up...and too many are done with nearly full frequency cabinets with mid and high frequency horns in each cabinet. Now that will give you some comb filtration! And you cannot really project good controlled low end without going to at least a 30 foot tall line array. The way most subs are used is utterly wrong; they are effectively point sources splattering low end all over the venue and making everything sound muddled.

All frequencies can be directed if you pay attention to wave lengths and the size of arrays. The idea that lows are inherently non-directional is rubbish. Dispersion from a source is completely wave length dependent...until you get into some of the sonic holography technology, and that's just not practical yet in concert settings.
 #122824  by jenkins
 Sat Jan 05, 2013 7:56 am
Great post Rick, so cool to hear about the WOS from someone who actually had a and in buildinng the whole thing.
I think it's amazingg that you still haven't heard anything better than the wall on a good day, even to this day. That speaks to the quality of the craftsmanship in building all those cabs and puttingtogether the line arrays on site for each shoow and just the overall level of planning and attention to detail that went into the whole thing.
Even listening bback to WOS shows there is a warmth in the sound that was just amazing. Most of the post WOS 70's dead shows still retain some of that warmth but then in about 79-80 it gets lost. I was listening to an 81 show on xm the other day and while it still sounded great it just didn't have that certain warmth to the tone that the 70's showws posesss, particularly the WOS year. To me the 80's shows just sound a little sterile to me, they still ssound greaat but lack that little something that the 70's had in spadess. I barely ever even listen to 80's shows anymore because of that reason. For me, like 90% of my GD listening are the years 73-77
Do you have any theories on why this happened?
Could it be because they stopped using macs and JBL's? just different recording methods? I'm just always perplexed on why they would go to a system that didn't sound quitee as good. Just wondering if you had any opinions on why that might be..

II was also wondering what you think you would do different if you were building the WOS today, what improvements to the system would you use, like maybe foam instead of horse hair rugs iinside the cabs. Also would you still use JBL cabs powered by external macs or would you use the meyer self powered speakers instead?

Also you mention designing the line arrays based on wave lengths, does that mean that in order to get that quality sound out of a system like that do the arrays need to be 30' tall? WOuld it be possible to even build a smaller WOS for a band that plays in larger clubs & small theaters? Can the theories of the WOS be downsized or would something like that only work in stadium settings like the GD were playing back then that are big enough to accomadate ssuch a system.

Thanks for the posting about it and thanks for helpiing build and design the greatest sound system ever used!
 #122843  by zambiland
 Sun Jan 06, 2013 1:24 am
Here's a fun read on line arrays: ... _array.pdf.

I never heard the Wall but I did hear the rig at Oxford Plains in 1988 where there was a stack of Meyer subs one wide and 4 stories tall on either side of the stage (near as I can remember and judging by comparisons to trucks parked right behind them in photos). I have to say that it was the best low end response I've heard out of any system anywhere. It was deep (sounding like it was coming up out of the ground) and quick, with no muddiness. The impact was felt all the way to the back of the racetrack.

I did have a conversation with Dave Rat, sound engineer for the Red Hot Chili Peppers, etc., when he posted some stuff on the net about difference bass cabinet configurations and he dismissed low end line arrays as inefficient and sonically inferior to his cardioid sub arrangements. I've not seen the Peppers live since the Uplift Mojo Party Plan tour, but I can't imagine that it would sound any better than what I heard at Oxford Plains. Perhaps more pummeling, but not as quick, clear and deep.

I have to say that, in general, line arrays as commonly deployed strike me as being the live sound equivalent of mp3s. There might be a lot of reasons to use them, but they have more to do with convenience than sound quality. There are exceptions, of course, but hearing most of them does make me miss old school PAs sometimes.
 #123077  by Rick Turner
 Fri Jan 11, 2013 8:00 pm
Line array dispersion theory is based on the wavelengths produced, and wavelengths are pretty much an absolute on this planet. A rule of thumb...a convenient to just estimate the speed of sound at sea level at 1,200 feet per second. Yes, I know it's a little bit slower, but for in your head math, 1,200 is a decent figure. That being the case, a 40 Hz tone has a wavelength of 30 feet. Ain't no way you're going to change that. So, sure, you can use shorter arrays, but you won't get the same kind of dispersion control in the critical vertical dimension. That's what pumps the low end into the audience and minimizes the splatter on the ceiling and behind which just muddies everything up. It's just math, not myth. No voodoo involved.

One of the problems with many modern line arrays is that they try to use a whole shitload of 3 way cabinets in a stack, and that spreads out the midrange drivers and tweeters. They need to be stacked right one on top of the other, and if you need greater power density that that gives, you need to do the kind of curved front array that Bear designed.

I happen to have a couple of the Bose L-1 small line array systems, and I really like how they sound up close or in a small room. No, they didn't go line array with the woofers, and so they miss out on what that can do, but the midrange and highs sound very nice to me. I still prefer the sound of cones to horns, and you'll find that most high end home and studio monitors do not use horns, particularly in the midrange. Why? Sound quality. The main reason to use horns is their incredible efficiency...not their sweet sound.
 #123135  by mgbills
 Sun Jan 13, 2013 10:59 am
Can you extrapolate just a bit Rick?

Basic understanding (which is all I possess) would allow one to envision ...let's say an 18' bass driver pulsing at stage level. The waveform would project like a 3 dimensional serious of hemisphere's toward the audience. In you're example the wavelength, which to my understanding is the distance between one peak & one trough is 30'. Why the verticality of the array?

Is it:
a) to create a clearer sound pattern and increased listening acuity for a bowl-shaped arena, or
b) Is it to allow the complete waveform to develop as it leaves the stage. Something to the affect of not shaving off the peaks with a stage, or other physical interference.

Or, is it something much grander. I admit that I play mostly to my shop, and have only been at it 7 years on a serious level.

 #123148  by Rick Turner
 Sun Jan 13, 2013 5:18 pm
The idea is to not (as closely as possible) create spherical sound wave front, but rather a cylindrical wave front. The surface area of a sphere (and thus SPL decreases) increases as the cube of the distance. For a sphere, it's the square of the distance. Hence the sound pressure level drops off much quicker with a point source. The other issue is that a spherical sound wave is going everywhere...back walls, side walls, ceiling, etc...and that creates a lot of reflected sound which just adds to aural confusion. With a properly aimed line array, you are directing much more of the sound just at the audience, and the "critical distance"...the distance at which reflected sound overtakes direct extended way better. A theoretically ideal sound system would hit ONLY the audience with sound, nothing would be reflected off of walls or ceilings. That's virtually impossible with today's systems, but we can get closer to the ideal, and that was one of the most important things about the WOS. It was largely successful, though a nightmare to set up and tear down. Sonically, the biggest problem was that as originally conceived, there were no monitor speakers. In practice it turned out that the guys were too far apart on stage, and the mix just didn't work for them as they mostly heard their own columns of instrument speakers. Revamped with in-ear monitors, it would work great today. The speaker columns could be redesigned with four or more loudspeakers per box, and then they could be snapped together to become their own scaffolding. There would be no attempt at hand carrying would be a forklift derby only. Power amps could be built into the boxes, and there could be digital front ends that would allow phase array aiming of each line array. We took the technology as far as we could at the time. Now there are a lot more good choices for drivers, amps, and packaging. The basic principles remain the same because they're based in the physics of sound and wave lengths.

If you haven't had a chance to try one of the Bose L1 systems, it's worth a try just to see how feedback-resistant they are with live mics. It will give you a small taste of some of what the WOS could do.
 #123179  by TI4-1009
 Mon Jan 14, 2013 6:57 am
I remember going to shows in the early 70's and one of the problems was that if didn't want to stand on the floor and you sat off to the sides, the mix was skewed- if you were on "the Jerry side" you heard more Jerry, if you were on "the Phil side" you heard more Phil. The sound may have been "purer", but the mix was tricky. You had to move around to find the sound you liked. It seemed like as they improved the blend that effect went away?
 #123589  by tigerstrat
 Sun Jan 20, 2013 11:27 pm
Did Jerry & Bob's open-back cabs follow the same formula?
 #123627  by tapestry
 Mon Jan 21, 2013 5:38 pm
tigerstrat wrote:Did Jerry & Bob's open-back cabs follow the same formula?
I was just about to ask the same question....I have a HT style cab and the back is about 1/4 open, a rounded rectangle slit in the back...I love how warm my cab sounds.
 #123643  by jenkins
 Mon Jan 21, 2013 10:22 pm
I find it very interesting that you mention the Bose systems.
The first thing I thought when I saw them, and their potential for band use, was 'wouldn't that be like a mini WOS?'
So you're saying that, in a way, they would be like a mini WOS?

Either way, thanks a lot for the posts. GREAT reads, some of it's a little over my head and i'm doing my damnndest to truly understand it, but it's some really interesting info and greatly appreciated.

Just another reason this forum kicks so much ass, we actually got one of the gguys who built & designed the WOS posting here about the WOS? WTH? unbeliveable, and totally awesome.
THanks rick!!