Upfacing Woofer Design

[Morgan]

Hi everyone,

I am designing a unique pair of speakers that will have an enclosure
with the woofer mounted on the top facing upwards and no other
speakers in the case. This is similar to a subwoofer design except
that the speaker will be facing upwards. Any ideas onto what value of
Q I should shoot for in this enclosure. Also any tips about building
this system would be greatly appreciated as I know it is not all that
conventional. Thanks in advance.

-Morgan Linton
Carnegie Mellon University

[Kevin McMurtrie]

In article >,
(Morgan) wrote:

>Hi everyone,
>
>I am designing a unique pair of speakers that will have an enclosure
>with the woofer mounted on the top facing upwards and no other
>speakers in the case. This is similar to a subwoofer design except
>that the speaker will be facing upwards. Any ideas onto what value of
>Q I should shoot for in this enclosure. Also any tips about building
>this system would be greatly appreciated as I know it is not all that
>conventional. Thanks in advance.
>
>-Morgan Linton
>Carnegie Mellon University

Any number of speaker cabinet calculators still apply to the enclosure
and port attributes.

The speaker direction changes the phase of the floor vibrations. It's
probably not a big deal on anything but a slow and heavy subwoofer. Try
it.

[Don Pearce]

On 3 Aug 2003 21:55:33 -0700, (Morgan) wrote:

>Hi everyone,
>
>I am designing a unique pair of speakers that will have an enclosure
>with the woofer mounted on the top facing upwards and no other
>speakers in the case. This is similar to a subwoofer design except
>that the speaker will be facing upwards. Any ideas onto what value of
>Q I should shoot for in this enclosure. Also any tips about building
>this system would be greatly appreciated as I know it is not all that
>conventional. Thanks in advance.
>
>-Morgan Linton
>Carnegie Mellon University

The one thing I would say is this - don't build a subwoofer with
upward-facing speakers. No matter how good a grill cloth you have,
stuff will always get in and lie on the cone. The result is a serious
amount of buzzing. OK, you can always vacuum clean the speaker every
time you use it, but that would really be a bit of a bore. So stick
with designs that allow dust and grit to fall off the cone, not just
sit there ready to rock and roll..

d

_____________________________

http://www.pearce.uk.com

[Nousaine]

Don Pearce wrote

>On 3 Aug 2003 21:55:33 -0700, (Morgan) wrote:
>
>>Hi everyone,
>>
>>I am designing a unique pair of speakers that will have an enclosure
>>with the woofer mounted on the top facing upwards and no other
>>speakers in the case. This is similar to a subwoofer design except
>>that the speaker will be facing upwards. Any ideas onto what value of
>>Q I should shoot for in this enclosure. Also any tips about building
>>this system would be greatly appreciated as I know it is not all that
>>conventional. Thanks in advance.
>>
>>-Morgan Linton
>>Carnegie Mellon University
>
>The one thing I would say is this - don't build a subwoofer with
>upward-facing speakers. No matter how good a grill cloth you have,
>stuff will always get in and lie on the cone. The result is a serious
>amount of buzzing. OK, you can always vacuum clean the speaker every
>time you use it, but that would really be a bit of a bore. So stick
>with designs that allow dust and grit to fall off the cone, not just
>sit there ready to rock and roll..
>
>d
>
>_____________________________
>
>http://www.pearce.uk.com

I used an up-facing 18-inch subwoofer sucessfully for well over a dozen years
with no problems other than suspension sag that eventually took it out of
service. There apparently wasn't enough dust-settle to cause problems as I
never once dusted the cone.

[Richard D Pierce]

In article >,
Kevin McMurtrie > wrote:
>The speaker direction changes the phase of the floor vibrations.

No, it doesn't. The acoustical coupling to the floor far exceeds
that of any mechanical coupling, and the phase of that coupling
is dependent upon the distance between the woofer and the floor,
but at the frequencies of interests, the wavelengths are very
long anyway. Beyond that, it is influenced FAR more by resonant
modes in the floor and such.

>It's probably not a big deal on anything but a slow and heavy
>subwoofer.

And we find the "slow and heavy" argument also works against
the notion of mechancial coupling ins several ways. First, as a
pretty reliable general rule, "heavy" equates to "large
diameter" suggesting the pressure coupling is more significant
as well (indeed, the moving mass of cones is roughly
proportional to their radiating area over some fairly narrow
limits" Secondly, since the mechanical coupling is simply
conservation of linear momentum at work, "slow" means less
momentum means less mechanical coupling.

>Try it.

I think there are factors that others have pointed out that migt
recommend against the approach, such as sagging and the like.

So what about an enclosure with TWO woofers, each on opposite
sides, once facing up, one facing down. The speaker sits on a
small plinth. Once a month, you pick the enclosure up, spin it
around and place it down. The top woofer ends up on the bottom,
the bottom suddenly finds itself on the top, and the dagging
issue is solved.

Or, horrors!, in the process of flipping it over, you accidently
stop halfway. Sagging solved! :-)

--
| Dick Pierce |
| Professional Audio Development |
| 1-781/826-4953 Voice and FAX |
| |

[GregS]

In article >, (Morgan) wrote:
>Hi everyone,
>
>I am designing a unique pair of speakers that will have an enclosure
>with the woofer mounted on the top facing upwards and no other
>speakers in the case. This is similar to a subwoofer design except
>that the speaker will be facing upwards. Any ideas onto what value of
>Q I should shoot for in this enclosure. Also any tips about building

I guess Q can have other effects. If the mechanical Q of the driver is too high,
it may sag more than a driver with a lower Q. This may or may not be true depending of the
construction.

greg

[Richard D Pierce]

In article >,
GregS > wrote:
>In article >,
(Morgan) wrote:
>>Hi everyone,
>>
>>I am designing a unique pair of speakers that will have an enclosure
>>with the woofer mounted on the top facing upwards and no other
>>speakers in the case. This is similar to a subwoofer design except
>>that the speaker will be facing upwards. Any ideas onto what value of
>>Q I should shoot for in this enclosure. Also any tips about building
>
>I guess Q can have other effects. If the mechanical Q of the driver is too high,
>it may sag more than a driver with a lower Q. This may or may not be
>true depending of the
>construction.

The mechanical Q is a measure of the fristional losses in the
suspension. As such, it's difficult to imagine a causal linkage
between Qm and how much something will sag. That's a function of
the mechanical compliance and the moving mass of the driver.
Now, over a period of time, there may be some cold-flow effects
resulting in the driver taking on a permanet "set."

But I suspect what correlations MIGHT exist between Qm and
sagging are coincidental rather than causal.
--
| Dick Pierce |
| Professional Audio Development |
| 1-781/826-4953 Voice and FAX |
| |