General Forum - 4th order bandpass.

4th order bandpass.

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Category: General
Forum Name: General Forum
Forum Description: Open Discussion / Questions
URL: https://forum.speakerplans.com/forum_posts.asp?TID=104824
Printed Date: 16 April 2024 at 3:31pm
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Topic: 4th order bandpass.

Posted By: FOO
Subject: 4th order bandpass.
Date Posted: 10 February 2020 at 9:27pm

I was on a install saturday, putting in new subs and amps.

Owner wanted smaller boxes as the old ones took up precious space.

So i did.

Now i got a old set of Martin M152i 4th order bandpass subs sitting here.

Loaded with two Beyma 15G400.

And after some fidling around with them, i kind of like the Sound they make.

Fine LF response and very tight kick.

So i came to think... What if one took two modern drivers.. 18, 15 or 12 inch, and mounted them in a 4th order box made to go low and loud. Would it end up too large and clumsy?

Replies:

Posted By: colint
Date Posted: 11 February 2020 at 5:39am

The M152i is a third order bandpass box, best to stick to the proper drivers as bandpass boxes tend to be very hard on drivers and unless the drivers are the same parameters they won't last too long.

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Never criticise another man until you've walked a mile in his shoes. Once you have, call him what you like, you're a mile away and you've got his shoes!

Posted By: FOO
Date Posted: 11 February 2020 at 7:03am

I know they state 3th order, but from what i can understand, 3th order is a sealed back chamber, and vented front chamber with two ports with different tunings.

Mach 152i does have two ports. But they are the same size. So that would make it a 4th order ?

But i will not put other drivers in it. I would find some drivers suited for this type of enclosure and design a new one around them. Just to see how good it could get with modern drivers.

Posted By: Chris Grimshaw
Date Posted: 11 February 2020 at 8:53am

4th order is sealed back, vented front.

6th order has both chambers vented. Parallel means both ports fire to the outside world, while series has one chamber venting into the other, which then goes to the outside world.

8th order takes a series 6th order bandpass, and passes the result through another ported chamber. You don't see those much, and with good reason - it's a big, complex box. You get more output from simply using better drivers.

FWIW, I made a 4th order bandpass recently when the customer wanted to use some particular 18" drivers that had a Qts of about 0.5. That's too high for a sensible ported box (most alignments were peaky, except for a very big box tuned very low, which in turn had very little power handling before the drivers bottomed out), so I went BP4 and did a couple of other neat things with the design to get force cancellation (ie, the cabinet didn't walk around) and direct venting of the magnets.

The results were pretty decent, especially given the mediocre (IMO) drivers. BP4 has the other advantage that it's difficult to bottom the drivers out as it's a sealed back chamber - very-low-frequency signals wouldn't be an issue. Combined with the forced air flow, it was a tough box to kill.

Chris

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Quality sound from Sheffield
www.grimshawaudio.com

Posted By: FOO
Date Posted: 11 February 2020 at 9:32am

So for what its Worth, it could be a fun project to make a project out of it and see what i end up with 🙂

The hunt starts for low Fs/High Qts drivers 🙂