Midrange keeps on popping

[pjaneiro]

Hello, quick question for you nice folks, I just finished building nice cabinets with 12" subs 5 1/4 mid ranges and 3" tweeters your regular stuff really, but I had to go with cheaper mids because they were out of my favourite brand, now they seem to "pop" when I play too much bass, they are rated at 700hz and my crossover is set to 700hz with a 12db cut off, it's a sealed crossover system, and I don't feel like ripping it apart, is there an easy way for me to set my mids to 800hz ? I was thinking of adding a capacitor between the crossover and the mid, it would add an extra 6db, but I am unsure of the value…the mid is rated a 8ohm…

Thanks...

[BobEllis]

Is your mid in a separate sub-enclosure so that it cannot see the back wave from the 12"? Is it well sealed, such as where the cable passes through?

Be sure that your crossover midrange section is wired correctly.

Assuming a decent design the first time around, just adding another cap won't do what you want without having other effects. Do you have any way of measuring the speakers?

[pjaneiro]

The mid-range is in the same enclosure, and it's a sealed type mid-range, so it's not getting any pressure from the woofers, i think it's because of the freqency range, it's too close, so i'm back to my idea of getting the mids to start at 800hz instead of 700hz, without having to change the crossovers internally, i was thinking of adding a resistor in series on the positive between the crossover and the speaker, but i do not know the value i should be using....i'm just looking for a quick and dirty fix to solve this issue, i will be replacing the mids with the ones i usually use with are 600hz type

Thanks for all of your suggestions...

[Cal Weldon]

You can add a fixed L-pad but it will reduce the level. You can "notch" out the lower end of the mid but you will lose some signal as you aren't adding anything to the woofer.

As Bob mentioned, it's tough to change the XO properly without going inside.

[pjaneiro]

Well, i tried the resistor, and the effect is gruesome, the woofer and the tweeter play way too loud compared to the mid, so i took apart the crossover, it's a 2nd order linkwitz, using a 22uf and a 3.3uf cap, i don't have an inductance meter so i am unsure about the coils, i was thinking about replacing the 22uf for a 15, hoping it would give me a "ROUGH" 800-900 hz, am i off track here ?

[Cal Weldon]

Did you try an L-pad configuration or did you just wire a resistor in series? If so, that won't do it.

A second order L-R usually has one cap and one coil. Can you draw us a little schematic to help sort this out?

[Curmudgeon]

Could you describe the "pop"? Years ago I heard a system (one of those one year wonders, heavy ad campaign, high markups, short life) that at high levels made a "crack" sort of noise. It had small ferrite cored inductors, and when they saturated they suddenly stopped inducting (nice new word) and your heard a crack sound. Perhaps that's your "pop"?

Also, if it is the mid being overdriven, and perhaps the coil former is hitting the magnet assembly, it would take quite a change in cutoff frequency to fix the problem; more like an octave than a change from 700 to 800 Hz.

What driver did you use?

[pjaneiro]

The pop is really heard at high volumes with bass thumping so hard much your thoracic cage wants to explose, i never had this issue in the past with the other mids, they are both rated at 60 wrms, it really is a pop, i tried the same mid with a different crossover that i build simple 12 db one coil one cap, cutoff at 900hz, no popping here...so i'm stuck at a rutt here, how do i modify this crossover...

[Curmudgeon]

Again, was the crossover made with a ferrite core? Or a steel core? Could you describe the pop more clearly? From the level description, the ferrite core saturation or the coil former bottoming out sound likely.

The 60 watt rating is not very useful. Different manufacturers interpret it differently.

[pjaneiro]

Here's the pcb of the crossover i have marked the value for the caps, hope someone could sort this one out for me

Thanks...
The coils are air inducted ones, they are copper wire wrapped around a plastic tube