Question about the CS Ultra for Ron or Tom? (1 Viewer)

[Dustin B]

I was just curious why you went with three 3" ports instead of a single 5"-6" port?
Is there some advantage to multiple smaller ports over a single larger one?

 

[John Morris]

Possibly, they could use shorter ports and avoid some of the sonic problems inherent in using very long port-enclosure ratios. Then again, I'm no TV... or even a JG for that matter.

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Take Care,
merc

 

[Julian Data]

The more ports you add, the longer each length. The bigger the diameter, the more the length.
The more the ports the lower the airspeed.
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[Dustin B]

Oops, I thought length was solely dependant on the cross sectional area of the ports. So if you take the cross sectional area of three 3" ports, you find out you need a 5.2" port to have the same cross sectional area. In playing with LspCAD some more I found out that the single 5.2" port needs to be several cm longer than the three 3" ports to achieve the same tune. Is space that tight in the CS Ultra that you couldn't use a single larger port, or are there other reasons?
While I'm at it, why have you choosen to stick with 12" drivers in all your subs? Will the SS still be a 12"? Do you ever plan to make a 15" or 18" sub?
Just curious of your opinions since I've delved into the world of DIY subs and still feel like learning more (even though I've already built mine).

 

[Doug_B]

While I'm at it, why have you choosen to stick with 12" drivers in all your subs? Will the SS still be a 12"? Do you ever plan to make a 15" or 18" sub?

From a previous post (< 2 months ago?), I believe it was Ron who stated that there were no plans as of yet for them to produce a sub with a >12" driver. That implies that the SS line will not have a >12" driver. Also, I believe it was a quality issue mentioned. They found the quality required with 12" drivers.
I'm sure Ron or TV can clarify or correct me if I misunderstood.
Doug
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"Today is a good day to die." ...Old Lodge Skins

 

[PeteE]

The SS sub will use the same driver as the Ultra sub, but will be in a larger tube, about the size of the 16-46.
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Link Removed

 

[Jack Gilvey]

I can only guess based on some quick WinISD sims, but I'd assume that they wanted to maximize port area with the available flared ports (3",4",6" as far as I know) and given enclosure length. Going from the one 4" port used in the 20-39 to two of them results in a length which wouldn't fit in the box. One 6" port is even longer. The 3 x 3" ports are already pretty long in approx. 4 cu.ft tuned to 19.5 Hz.
So, I'd conclude that the area provided by three 3" ports is about all that will fit given the required length for 19.5 Hz tuning in 4 cu.ft. They provide about a 70% increase in port cross-sectional area vs. one 4" port, and, according to the numbers TV posted, don't start to compress until very high output.
There was some discussion on driver size a while ago. (Very) basically, a 15" driver would need a much larger enclosure, which is bad for shipping, etc. The 12" driver in the Ultras exceeds the displacement of most 15" drivers, which is all that really counts.

 

[Tom Vodhanel]

>>>I was just curious why you went with three 3" ports instead of a single 5"-6" port?Is there some advantage to multiple smaller ports over a single larger one?>>I can only guess based on some quick WinISD sims, but I'd assume that they wanted to maximize port area with the available flared ports (3",4",6" as far as I know) and given enclosure length. Going from the one 4" port used in the 20-39 to two of them results in a length which wouldn't fit in the box. One 6" port is even longer. The 3 x 3" ports are already pretty long in approx. 4 cu.ft tuned to 19.5 Hz.
So, I'd conclude that the area provided by three 3" ports is about all that will fit given the required length for 19.5 Hz tuning in 4 cu.ft. They provide about a 70% increase in port cross-sectional area vs. one 4" port,

 

[Jack Gilvey]

In the dozens of CS_U proto types,one of the first things I did was to see what 3-3s did vs. 2-4s.If there was a real reason to use 2-4s...we'd have em

I'm picturing a room not unlike the missile room on a "Boomer", the missiles in this case having had their warheads routed with every conceivable combination of port diameters.
Out of curiosity, how long are the ports in the Ultra? I couldn't even get two 4's to fit, but that's probably a WinISD thing, in addition to errors in my estimations.

 

[Ron Stimpson]

Jack,
We could tell you that, but then we'd have to kill you!
;^)
Ron

 

[Jack Gilvey]

Fair enough.

I'll have to wait for TN to get one.