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Old 16th July 2011, 06:59 PM   #1
7V is offline 7V  United Kingdom
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Default Orientation of bass drivers

I'm building a couple of bass speakers using 12" Goodmans drivers from the old Magnum K speakers.

Each cabinet will use 2 pairs of the bass drivers, each pair connected 'Isobabaricly' front to front and then the 2 Isobaric couples connected together in a metal frame to cancel each other's vibrations. That way, I'll get double the cone area in a box not much bigger than the original Magnum. The drive units are inexpensive.

Anyway, the speakrs were originally used in the normal vertical configuration and I'm planning on using them horizontally. Do you think this will cause problems with sagging cones, etc.?

Thanks
Steve
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Old 16th July 2011, 07:35 PM   #2
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Quote:
Originally Posted by 7V View Post
I'm building a couple of bass speakers using 12" Goodmans drivers from the old Magnum K speakers.

Each cabinet will use 2 pairs of the bass drivers, each pair connected 'Isobabaricly' front to front and then the 2 Isobaric couples connected together in a metal frame to cancel each other's vibrations. That way, I'll get double the cone area in a box not much bigger than the original Magnum. The drive units are inexpensive.

Anyway, the speakrs were originally used in the normal vertical configuration and I'm planning on using them horizontally. Do you think this will cause problems with sagging cones, etc.?

Thanks
Steve
Some cones are "saggers" when used horizontally, others seem to have no problems.
It would be a good idea to do some testing to see how your cones perform horizontally compared to vertically before committing to a design that requires horizontal loading.

Also, check for vent and spider noises, some speakers make a lot of wheezing sounds off the back that are not heard in normal operation.

This post showed that the Audio Concepts DV-12 was a "sagger":

subwoofer testing orientation: Part II
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Old 16th July 2011, 07:44 PM   #3
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I can't say how those particular drivers would respond, but I've been using a pair of peerless 850122 6.5" drivers face up in a sealed box for about 8 years now and haven't had sagging problems. When I put them together I made a referance mark on the inside of the routed-out area where they're mounted so I could keep track of it. I haven't seen any sagging, and don't expect any after that much time.

Mike
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Old 16th July 2011, 08:15 PM   #4
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The bigger the woofer, the heavier the cone, the more the sag, almost regardless of spider strength. I know there are formulas out there but I always think that if it is a HiFi unit don't do it unless it's 8" or less but if it's a PA type driver it might be ok due to the lightweight cone and stiff suspension. Just a practical non-technical way of looking at it.

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Old 16th July 2011, 09:05 PM   #5
sreten is offline sreten  United Kingdom
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Hi,

Why don't you put each isobaric pair in the left and right of the subwoofer ?

Cannot see any point at all for a top / bottom arrangement. FWIW also
cannot see much point in the metal frame, L/R or F/B mounting will give
you overall force cancellation via the box, which is essentially rigid /
somewhat elastic at any sensible subwoofer frequencies.

rgds, sreten.

Given what happens to drivers over the years, its best to mark the vertical
orientation, and then mount them all rotated through 180 degrees, it works.
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Last edited by sreten; 16th July 2011 at 09:16 PM.
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Old 16th July 2011, 10:22 PM   #6
7V is offline 7V  United Kingdom
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I have tried vertical mounting with 6.5"/8" drivers (depending on where you measure them) without any problems. These drivers are larger though.

Quote:
Originally Posted by sreten View Post
Why don't you put each isobaric pair in the left and right of the subwoofer ?
It's a question of the overall shape of the speakers. I'd rather have a taller enclosure than a longer squatter one.

Quote:
Cannot see any point at all for a top / bottom arrangement. FWIW also
cannot see much point in the metal frame, L/R or F/B mounting will give
you overall force cancellation via the box, which is essentially rigid /
somewhat elastic at any sensible subwoofer frequencies.
Interesting point that I'm going to have to think about some more.

It's actually not much hassle to do the frame. I know that the metal frame will provide 'immediate' cancellation because of the rigidity and the acoustic coupling through the frame. I'm planning to mount the frame in the enclosures (top and bottom) via neoprine gaskets, which aren't so immediate and are more decoupled. However, I will give more thought to whether it's necessary or beneficial.

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Steve
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Old 16th July 2011, 11:13 PM   #7
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steve ? is nonsuch in business ?
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Old 16th July 2011, 11:45 PM   #8
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I've got five freakin speakers in my house with saggy spiders.
Three of them are subwoofers.
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Old 17th July 2011, 12:43 AM   #9
7V is offline 7V  United Kingdom
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Quote:
Originally Posted by norman bates View Post
steve ? is nonsuch in business ?
Seventh Veil Limited is no more, sadly. I'm building for myself now.
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Old 17th July 2011, 10:17 AM   #10
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I'm sure we'd love your yapping over on the full range section here, or the fullrangedriver.com forum.

I'd never have subs facing up or down.

Norman
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