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Re: First speakers - a little ambitious - curved array [message #60656 is a reply to message #60654]

Sat, 22 August 2009 17:21

Villain3g
Messages: 22
Registered: August 2009

Chancellor

Is this comb filter distortion why metal music sounds a little off? I thought that curving the baffel would counteract that affect. Acoustic guitar and vocal music sound incredible but the high end in metal music gets confusing. Its hard to describe. Maybe having them wired at 4 ohms is overloading the receiver?

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Re: First speakers - a little ambitious - curved array [message #60657 is a reply to message #60656]

Sat, 22 August 2009 22:29

Eric J
Messages: 71
Registered: May 2009

Viscount

Exactly. Heavy metal uses those frequencies, AND REQUIRES THE UPPER HARMONICS. Other music also requires it but you can get along without it if the array has all the other good things.

This is how Jim Griffin describes it:

"Comb lining will dull the highs and will be most noticeable in the lack of air (dull highs) especially as you move off axis. Essentially, the high frequencies are rolled off as the ensemble of the tweeter outputs don't add up but start to cancel. Now the ear is less sensitive in the upper octave (10-20 kHz) you may not observe the full impact of this effect. But if you compare to an array that is properly designed, then there is no comparison as the proper array will yield a more airy (and accurate) sound."

Jim Griffin on Parts Express Tech board on 11-21-06

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Re: First speakers - a little ambitious - curved array [message #60658 is a reply to message #60536]

Sun, 23 August 2009 21:18

Villain3g
Messages: 22
Registered: August 2009

Chancellor

I was just thinking. Can you offset the drivers of a line array in a zipper pattern to get the vertical c to c closer?

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Re: First speakers - a little ambitious - curved array [message #60659 is a reply to message #60658]

Sun, 23 August 2009 22:06

Eric J
Messages: 71
Registered: May 2009

Viscount

Distance is distance.

I thought ab out that but when you get to measuring its usually less. You have to look at the whole picture: the frequency response of your speakers, where you are crossing them, the slope of your crossover(for the overlap and where they fit), and the comb filter distortion for how far apart they have to be.

Like i said, for the system I developed for me I could only use 3/4 inch domes that had the domes literally silk to silk. I would have liked to put my 3.5 inch mids closer together but i also wanted each one to be separated physically completely from the others so that there was no backwave interference, and i wanted to make sure that the backwave for each was completely negligible so that nothing from the back of the speaker was coming back through the front to muddy the midrange sound.

Eric J.

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Re: First speakers - a little ambitious - curved array [message #61168 is a reply to message #60659]

Mon, 12 October 2009 15:28

Villain3g
Messages: 22
Registered: August 2009

Chancellor

Before I go and build the big lines, I wand to modify these. My goal is to stick a Dayton PT2C-8 in the middle of the curved arrays. This will eliminate the combing. Now I need some sort of crossover. I would like to have a separate high-pass for the tweeter and a low-pass for the line. This would allow me to bi-amp. This will also allow me to match the volume of tweeter to the line. I'd like it to be as steep a slope as possible at 5k. A 4th order crossover satisfies that criteria. I found a calculator online at:

http://www.apicsllc.com/apics/Misc/filter2.html#fourth

The values it gave me are not available. How close of a tolerance should there be on the components?

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Re: First speakers - a little ambitious - curved array [message #61251 is a reply to message #61168]

Wed, 21 October 2009 16:27

Villain3g
Messages: 22
Registered: August 2009

Chancellor

Second iteration. Two-way, bi-amped, 24db passive crossover at 5khz, and curved for time alignment.

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Re: First speakers - a little ambitious - curved array [message #61252 is a reply to message #61168]

Thu, 22 October 2009 00:55

selahaudio
Messages: 56
Registered: September 2009

Baron

Villain3g wrote on Mon, 12 October 2009 15:28

Adding the tweeter doesn't eliminate the comb filtering, especially with a 5K crossover point.

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Re: First speakers - a little ambitious - curved array [message #61255 is a reply to message #60536]

Thu, 22 October 2009 12:52

Marlboro
Messages: 403
Registered: May 2009

Illuminati (1st Degree)

Villain3g,

To find where the basic level of comb filter distortion starts, you divide the distance of the speakers in inches from the speed of sound in inches per second. This gives you the frequency where comb filter distortion may start. For example 13560 inches per second/3.5 inches center-to-center = 3874 hz. In this example comb filter distortion will start at 3874hz, and you really can't cross your 3.5 inch center to center midranges much above 3874. If your mid ranges were 5.25 c-to-c, then it would be 13560/5.25= 2582hz, where your cross can't come in higher than 2582.

The center to center distance between your mid ranges can't be any further apart than 2.75 inches to cross at 5000hz. and you would do well to remember that the distance between the highest mid in the lower group and the lowest mid in the higher group is way above that number.

Your planar needs to go on the side of the mid line array. However I've seen a lot of arrays, including Fred's ART array that put a tweeter in the center between the two smaller lines. I don't know what this does.

All this said, I'm not 100% sure how much you can hear comb filter distortion, as long as you sit in one spots and don't move your ears vertically.

Marlboro

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Re: First speakers - a little ambitious - curved array [message #61257 is a reply to message #61255]

Thu, 22 October 2009 15:19

Villain3g
Messages: 22
Registered: August 2009

Chancellor

my 2" peerless fullranges have a ctc of 2.17. Combe filter starts at 6260. I thought having the ribbon take the high freqs at 5k would make the comb effect not noticable. Is it that im crossing too close?

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Re: First speakers - a little ambitious - curved array [message #61261 is a reply to message #61257]

Thu, 22 October 2009 16:53

Marlboro
Messages: 403
Registered: May 2009

Illuminati (1st Degree)

If your c-to-c on the mids is only 2.17 then they will not comb filter at 5000, and the ribbons don't have that kind of problem.

Looks good then.... to me! Don't worry about comments from people who make cryptic statements and don't tell you why.

How low do those little fellows go for a two way? They look sort of like a 2 inch mid range dome. PE makes one of those and they don't go lower than about 400hz

I don't think that the distance between the two portions of the mid range array are an issue but is there wa reason why you didn't make the baffle wider and put the tweeter on the side?

Marlboro

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