Does Phase Matter?

[Mjr7531]

I've almost decided on my next project, I want to go with the dayton tweeter and the NSB.
I'm crossing at 6k and I'm not sure what network to use, I understand the differences between say a 2nd degree and a 4th degree, but how big of a difference does the phase change make?
Also, Do you have to cross an octave above the Fs or the frequency response of the tweeter, lastly, what good reading on crossovers so I don't have to ask small questions such as these?
Thanks,
Matt

[SY]

If you don't have it already, get a copy of Dickason's Loudspeaker Design Cookbook.

Re your specific question, the audibility of phase shifts in this range and of this magnitude is questionable. Sloppy polar patterns and deviations in frequency response, OTOH, are unquestionably audible. The 4th order makes for a cleaner polar pattern, less sensitivity to driver offset, and better power handling. Make sure, though, that you understand the difference between a 4th order electrical and 4th order acoustic response!

[chipco3434]

FYI

I just built some speakers using the NSB's and the Dayton tweeter. Four NSB's and a neo in a MMTMM sealed .87^3 ft box. The crossover was 2nd order at 4800 Hz. I installed a switch in the proto crossover board for phase reversal for testing.

I couldn't hear difference and neither could several test subjects.

[Mjr7531]

Thanks guys, I think I'll go with 2nd order this time and experiment later, every penny saved counts

[kelticwizard]

Originally posted by chipco3434
FYI

....MMTMM sealed .87^3 ft box. The crossover was 2nd order at 4800 Hz. I installed a switch in the proto crossover board for phase reversal for testing.

I couldn't hear difference and neither could several test subjects.

Does that mean:

A) You reversed the phase of the signal going to your woofers/tweeter combo as a unit, leaving the phase relationship between the woofers and tweeters intact?

or

B) You reversed the phase of the woofers in respect to the tweeters?

[chipco3434]

The answer is.....

B

[jamesj]

Then I don't think you have a true even order crossover, which should yield a deep null when the correct polarity is reversed.

James

[chipco3434]

It looks like a textbook 2nd order to me. Coil & cap to woofer, cap & coil to tweeter. Cross is 4800.

I'm all ears and willing to learn.

[BobEllis]

The null when the tweeter phase is wrong is deepest when the drivers are phase aligned. This implies that if they are not aligned the notch will not be so deep. if far enough off there won't be an audible difference.

Somebody was kind enough to post an excel file a while back called something like "driver offset response calculation." a search ought to turn it up. Whoever did it did it at work and didn't change the author info so I don't know who to credit

at 4800 hz, 2nd order bessel, you'd only get a low Q 5 db dip around 4KHz if the drivers' acoustic centers are 1 cm out of alignment.

[Ron E]

Originally posted by chipco3434
It looks like a textbook 2nd order to me. Coil & cap to woofer, cap & coil to tweeter. Cross is 4800.

The crossover is a combination of the inherent acoustic slopes of the drivers plus the electrical slope of the circuit used. A 2nd order electrical crossover will typically be 3rd or 4th order with most drivers, unless they are very wide range and have large overlaps in response. Lack of a reverse null means you may have a situation where the main lobe is not pointing at the design axis, or you may have an odd order or nonstandard crossover topology. Failure to detect a reverse null does not mean that one doesn't exist. A reverse null can actually be quite subtle, depending on how narrow it is..

Phase is important, but it is not some magical/mystical word. I will say that the design of a crossover without measurements is possible, but not very likely to be successfull in an objective sense; although you may be quite happy with the results.