Posted by Jim Griffin [ 12.180.246.118 ] on May 23, 2007 at 20:01:34:

In Reply to: Pinging Griffin (again) posted by topher_m on May 22, 2007 at 20:02:45:

Chris,

First, I did send you an e-mail rely (with attached files) last night which I assume that you received.

I'll be honest with you that I'm a little confused as to what you asking me. I'll try to address what I think you are asking and you let me know if I'm off base.

You asked:

Inevitably within a budget there are tradeoffs - would you prefer

1). a lower xover point to bring below 1 wavelength but get a fairly short tweeter line (say 45 inches)

2). full length tweeter line but this would push xover for ctc to 1 wavelength

My Reply:

Now if we are talking about a tweeter line that consists of ribbon tweeters then you don't have to be concerned about comb lining (ctc spacing) as long as you maintain a relative high active radiating factor (ARF) as explained in the white paper. For ribbon tweeters ARF is the active radiating length area ratioed to the total flange and active lengths. I suggest that you use an ARF of 80% which effectively places the tweeters flange to flange for most available tweeters.

As I explain in my white paper, ribbon tweeters of the kind (the Fountek Neo2.0 or Aurum Cantus G3 are typical of this variety) that I suggest will have minimal vertical radiation overlapping dispersion (see page 14 of the white paper). Essentially, the vertical center to center placement doesn't come into play with ribbon tweeters. The placement between tweeters in the their stack should be flange to flange to maintain the maximum radiation factor.

Typically, a stack of 8 or 9 ribbon tweeters (roughly 7" height for each one so 56 to 63" total length) would be adequate for a near field/far field transition that extends out to at least 15' at 1500 Hz and beyond.

Let me hear if you want more info.

Jim

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