two 18's in different boxes cancellation

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j_darling2007

Copper - Posts: 210

Joined: January 21, 2005

Location: United States

Posted: February 22, 2009 at 6:54 PM / IP Logged

I am designing a subwoofer set for my dj setup (home stuff, I know, but you guys have given me some of the best advice I have gotten)

I have used a Dayton WT3 to measure the parameters of my subs, and want to do a 4th order and 6th order bandpass setup (one for each woofer) The idea is to have the 6th order reach the 20Hz region, while having the 4th order cover from about 30 Hz up. My problem is, will I run into cancelation issues between the woofers? I have atteached the SPL plot of each woofer, and the phase plot. If I can get you more needed information, I can do that.

https://i728.photobucket.com/albums/ww281/jed7w2/Box2.jpg

https://i728.photobucket.com/albums/ww281/jed7w2/Box1.jpg

Thanks for the input,

Jacob

There are 3 kinds of people in the world, those who can count and those who can't

haemphyst

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Joined: January 19, 2003

Location: Michigan, Bouvet Island

Posted: February 22, 2009 at 7:06 PM / IP Logged

At 30Hz, it looks like you will be about 120 degrees off each other. That's a significant shift! My expectation is that (in addition to the HUGE dip at 24-25Hz) you're not going to get very flat response.

Now, that being said, the ear can't really hear that low, anyway, and won't hear it as a hole.

It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

j_darling2007

Copper - Posts: 210

Joined: January 21, 2005

Location: United States

Posted: February 22, 2009 at 7:16 PM / IP Logged

Thanks alot!

I was unsure how to interpret the phase plot. I'm going to play around with the box desgin and see if I can get a better setup. I'll post it when I get it and see what you think, if thats ok.

What's the largest "acceptable" phase difference? I need to know about where to shoot for.

Thanks,

Jacob

There are 3 kinds of people in the world, those who can count and those who can't

haemphyst

Platinum - Posts: 5,054

Joined: January 19, 2003

Location: Michigan, Bouvet Island

Posted: February 22, 2009 at 8:52 PM / IP Logged

Sure, no problem!

There is really no such thing as largest acceptable. Multiples of 180° (or close to it - within 5 to 10°...) are IDEAL, because you can simply reverse the leads and be right back in phase.

It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

j_darling2007

Copper - Posts: 210

Joined: January 21, 2005

Location: United States

Posted: February 22, 2009 at 10:35 PM / IP Logged

Thats what I thought.

No matter what I do with 2 different types of boxes (I even tried two 4th order boxes tuned to a different frequency), there is a very bad phase difference in the 30Hz area (I have not been able to get a phase difference less than about 65 degrees). Is there any way to get around this, or am I just going to have to use identical boxes for these subs?

Has anyone had any first hand experience with something similar to this???

Thanks

Jacob

There are 3 kinds of people in the world, those who can count and those who can't

aznboi3644

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Joined: May 01, 2006

Location: United States

Posted: February 23, 2009 at 2:19 AM / IP Logged

I'd build a tapped horn for DJ'ing....much more efficient. You can have a lot more output. Only thing is that the enclosure is going to be big.

Custom Enclosure Design

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two 18's in different boxes cancellation

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