Stock crossovers just won't do here
droeses58 said:
The reason I ask, is I'm having a problem with my diy speakers which amount to a dayton reference 8" woofer with a reference dome tweeter [don't have the parts numbers in front of me at the moment] but the woofer is rated to 2000Hz and the tweeters fs are 600Hz
I didn't know squat about crossovers so I just bought there 2 way 2k pre-made crossver and it sounds decent until I turn it up to say about 90db then it starts to break up badly [sounds like crumpling cellophane] and just gets worse the louder I turn it up.
Now, I also built some smaller satellite speakers using the same tweeter and same reference style woofer but smaller 5". I built my own 2k crossovers and don't have the breakup problems that I have with the pre-made crossover and 8" woofer.
It sounds like to me that the tweeter is whats breaking up, but could it be the woofer that I'm hearing? That 2000Hz is just to much for it?
On a side note I would like to incorporate a bsc into the mix and at P.E. they give an example of a 1.0mh inductor and an 8ohm resister is this placed just in the woofer segment before the crossover or is it placed before the "whole" crossover?
Are those the Dayton Reference Series aluminum drivers that you have? The tweeter is the RS28, the 8" is the RS225, and the 5" is the RS125. They are real good drivers.
That tweeter crossed at 2 kHz is probably OK and should not be the source of the noise you hear. The problem you've described sounds to me like it may be caused by using an 8" aluminum driver with a crossover not custom designed for it.
Go to the PE site and look at the sample response graph of the RS225. You'll see it looks fairly smooth up to about 2 kHz, with some real bad break-up noise beginning above 3 kHz and peaking in the 5-10 kHz range. This is typical of many aluminum drivers. Why should that be a problem with a 2 kHz crossover? I'm guessing that you bought a stock PE crossover with a 2nd order slope. Look at the magnitude of the breakup noise peaks. They are as much as 10 dB greater than the smooth response below 2 kHz. You will hear that despite the crossover.
Remember that in sound, one loudness level 3 dB higher than another is twice as loud, 6 dB is 4 times as loud, etc. A 2nd order crossover rolls-off the signal to the woofer gradually at 12 db per octave beginning at 2 kHz. So if the loudness is at about 88 db at 2 kHz, it should be at 76 dB at 4 kHz, 64 dB at 8 kHz, and so on. But if the breakup noise peaks are much higher than the smooth part of the curve below 2 kHz, you will hear it as high frequency noise. You should be able to tame that with a 4th order crossover, with a steeper roll-off slope of 24 dB/octave. If that still isn't good enough, a notch filter can be used to further quiet the worst peaks at 7-10 kHz. Stock crossovers just won't do for the 8" woofer.
If you look at the response graph of the 5" RS125, you'll see why you don't have a similar problem with a 2 kHz crossover. There are large breakup peaks, but the loudest one is well above 10 kHz. What kind of crossovers did you make for them - 2nd order?
If you go to the PE site's Tech Talk discussion board, and ask there if anyone has a 2-way crossover design for the RS225 and the RS28, you should get plenty of useful answers.
