Columaire by Atlas Sound speakers not working

[Terry]

I just got a set of these for free.  Two small columns with 5  times 5" speakers.  I'd like to ad them to my band in a box set up but I don't get a sound out of them.  Not a peep.  They say model c-46 16 0hms  20 watts.  They were in a church and someone had stuck a little transformer on to....I don't know why. 

Can anybody help?

[tubesornothing]

First grab a meter and measure the resistance and the input jack.  Ignore the transformer (for now). Should be around 12-13 ohms for those babies.  If its infinity, then pop off the cover and measure each speaker individually.  Post your results.

[Frankenamp]

The transformer is most likely because there was a 70 or 25 volt line to the speakers. The Atlas columns are a primitive attempt at a line array, and not very effective. A line of six or nine NSB drivers will be much better. The Atlas are better than nothing, but not much. What is the spacing frame to frame? Check the individual drivers and see what the DC resistance is (nominal resistance will be approx 1.414 times DCR).

[Terry]

Thanks guys I got them working. 

Frankenamp....perhaps you had a run in with an Atlas sound column before you were 5, forgot about it and yet the trauma is playing out to this very day

...in any case, they'll do for my rear TV speakers and nicely at that.

[Frankenamp]

Ummm... no run-in's with Atlas products- they were still popular PA products when I was a pup. The dream PA speaker at the time was a pair of Altec VOTT's. When I was 5 I did have a run-in of sorts at the county fair- I wanted a monkey-on-a-stick and either my behaviour or parental budgetary constraints did not warrant the acqusition. I reacted like a three year old with a full-on tantrum and threw my disappointed-spoiled-brat-self backwards ... right into a fire hydrant. Specifically, the nice sharp square valve stem- made a nice impression in the back of my misbehavin' skull :o Lernt me watch where I threw them tantrums ;D

They should be fine for that purpose, I'm not knocking Atlas, it's just that the principal of line arrays have been around for a long time (even has a section in Beranake's 'Acoustics' if I remember right) modern designs handle comb filtering effects better now. Hell, I remember the old Acoustic columns of 6x9's in a quasi-horn loaded design that were popular as vocal reenforcement (so the singer could be heard over the stacks of Marshalls & Hiwatts.

[Terry]

What your talking about actually does sound very interesting, but in order for me to understand it, I'd need it a little in layman's terms if that were possible.

[Frankenamp]

Comb filtering works a lot like it's namesake- the comb. With lower frequencies it's called the Power Alley (one tooth). The rule for subs is this: closer than three feet between each one or further than 30 feet. It has to do with the wavelength of each tone. In the middle of the "alley" the phase of the two frequencies is additive (they work together) to each side the frequencies work against each other and the it sounds softer. (So, if you go to a gig and the subs are clustered to one side or in the middle- it's a clue that the sound guy knows his stuff.) Moving up the scale, driver placement is even more critical. When drivers are sharing the same frequencies, they need to be mounted within a wavelength of the highest frequency to eliminate the combing effect. I have a line of 27  3/8" dome tweeters that are crossed at about 5kHz. the center to center is about 1.5" which is about 9,000 Hz so the cones are effectively coupled up to 9kHz. above 9K, you get some combing... you can year it as a fluctuation in volume as you play a tone and do some deep knee bends- you don't hear much if your ears stay on the same height relative to the line. It sounds a little wierd with steady tones, but not as noticeable playing most music. It would be much more pronounced if the tweeters were not as close. Mounting a line of horns mouth to mouth is better, because you can get effectively zero center to center spacing because the whole mouth of the horn radiates.

Note: this works only if the line is vertically arrayed- lining up mids or tweeters horizontally is a recipe for disaster. (this is why those "cluster arrays" sound like *expletive deleted*)