Anyone know about Sunn 215B Beta 2x15 bass cab?

[RosaLee Jake]

Hiya,

We've got one of these 215Bs.  Does anybody know where (if at all) foam to adjust the acoustic properties of these cabs is supposed to go?  I looks like one piece at the far sides of each "port", and that is it.

Thankya, RL & J

[Tom Loizeaux]

Tell me more about this "foam " you're refering to. Sunn did use a thin layer of foam on the inside rear wall to dampen interior reflections. It was not perticularly effictive.
Give more detail and I'll try to help you.

Tom

[Anonymous]

Hiya Tom,

Judging from examining this box closely, there appears to be only two places where there are staples indicating 'glass or foam was once there (and later removed).  These are at one side of each "port".  There are no staple or glue marks inside the cabinet so I don't think there was foam in the enclosure itself, just the ports.  Does this seem right?

Speaking of which can you or anybody explain the physics of how this box works?  It seems to me that the enclosure volume is fairly small and the equivalent port size is huge -- maybe I'm incorrect here, but it seems like the port should be smaller.  Is there something about how the port is layed out in the box that makes it superior to another arrangement?

Thanks for the help Tom,
RL and J

[sunn]

This was emailed to me for some weird reason:

Can you send me a photo (or drawing) of this Sunn cabinet? There are a
number of designs that Sunn used over the years.
Port size IS critical in the proper tuning of the cabinet. Sunn often used
an angled baffle as part of he port. The actual post size is more related to
the smallest part of the port. If there are tubes, then one would have to
guess that the length and diameter of the port(s) was carefully calculated.
Not that it couldn't be improved, but I suspect the ports are reasonably
close to correct.
"Foam" or acoustic padding (fiberglass) can be applied to all side of the
cabinet interior. To an extent, the more padding the smoother the sound as
reflections and standing waves are tamed. Many companies claim that it is
most critical to dampen three sides, so that no 2 bare sides face eachother.

Hope this helps.

Tom
Chesapeake Musical Equipment

[Anonymous]

Hiya Tom,

Here's a pic of the cab:

http://www.geocities.com/ozzyaxe/sunn.gif">http://www.geocities.com/ozzyaxe/sunn.gif

http://www.geocities.com/ozzyaxe/sunn.gif">

If you are not familiar with this model, this is actually one huge continuous port that tapers out by way of the angled baffle.  At the smallest part of the port, the dimensions are approx. 37" tall by about 2.25" wide (or about 83" sq.).   The port length is approx. 14" or so, with about a 4.5 - 5" mouth at the face of the cabinet.  Not knowing much about speaker box design, I still thought this was interesting because 83" sq. for the smallest port area equals a circular port size of over 26" in diameter!  The actual box is pretty small too, volume wise.  Do you know what the rationale behind such a design is?  This doesn't immediately strike me as relating directly to a standard bass reflex design.

Thankya for your help

RL and J

[sunn]

Yet another message from Tom that got mailed to me

Thanks for the e-mail and photo.
    I have 3 of these 2-15 Sunn cabinets, but mine are the older ones
without the top trim, etc. Mine do have the angled port along one side as
yours does.
    I was a little frustrated that these cabinets would not take my speakers
down to the low E. I tried JBL E140s, and then EVM 15Bs which sounded
better, but they still tapered off too early. I got a frequency sweep
generator and found that these cabinets were tuned to around 60 Hz. I did
some experimemting with reducing the size of the port. I wound up making
some wedge shaped devices that I mounted inside the ports to bring down the
cabinet tuning to 42-45 Hz. I get a better controlled mid-bass, deeper low
end but with a very slight loss in effiency.
    So yes, these cabinets can be improved by reducing the port size. This
is a little tricky, but if you want to experiment, you will be able to
improve the low end!

Hope this helps.

Tom
Chesapeake Musical Equipment

[Anonymous]

Tom!

Thanks for the help, I've already started to play around with the port size.

Thankya again,

RL and J