Kornwall Killer Konstriction Kwestion

[Tom Mobley]

Ouch, that's bad.

But really, I've never seen any discussion about the rather nasty mis-match between the size

of the port (cross-sectional area of the space beneath the shelf) and the much smaller area of the port opening. On my '75s, the floor of the port is almost an inch below the bottom of the port opening in the motorboard. Also, the bottom of the shelf is about 1/4' above the top of the opening. Kind of like the opposite of the flared ports currently in favor.

So is it:

1) a secret technological advance by PWK?

2) an unfortunate by-product of the build method?

3) maybe PWK was not comfortable with how thin the bottom of the motorboard would be if the port opening was lowered?

4) just a missed detail?

5) covered under the dismissive "little yellow button" theory?

BTW, for the picky among you, please sub in the term "baffle" for "motorboard" wherever you see fit.

[chops]

Yeah, it's the same way on my '79s as well. I'm sure it's probably the same on all CWs. I'll go with your #4.

Honestly, considering the size of the port and how little the K33 actually moves, I highly doubt flared ports would be needed, but I do think the stock tunung freq might be a little skewed due to the opening being smaller than the actual port itself.

[3dzapper]

"1) a secret technological advance by PWK?"

Considering:

A; The design was developed " seat of the pants"

B; Prior to Thiel and Small's thesis

C; Uses a stock light weight driver optomized for sealed box/horn use,

That has to be the answer.

Rick

[chops]

"1) a secret technological advance by PWK?"

That has to be the answer.

Rick

Yes, but what does any of that have to do with the port being larger than the opening?

Even with the new CW III, the port and opening is still the same way. With port technology advancements over the years, you would think that Klipsch (not necessarily PWK, but the company in general) would have revised the port opening on the motoboard to acomidate the port itself.

As Tom mentioned in his post, the CWs port is essentially a reversed flared port.

[Daddy Dee]

Maybe this is one of those things Mr. Paul considered, but found that doing it different, didn't make a dime's worth of difference.

[JJkizak]

PWK probably kept changing the opening to get the performance he wanted. Air flow, frequency, chamber volume, port opening position, port size all work together. If you matched the port probably something detrimental will happen. It's not like a performance engine which uses the same criteria but where the majority of the formula is air flow restriction. But then again who knows. But you would think that the entire port system would be shaped like an exponential horn. AH HA! Maybe that's how the K-horn was created.

JJK

[jwc]

Tom. The way I sort of look at it is like this. That shelf port is on the bottom of the cabinet. I think it would be better to eliminate that "lip" of 3/4 strip on the bottom of the port opening. Much like if you built the motorboard and made it 4" shorter. Then the port opening would be "wide open" w/o resistance of flow. However, it might not be as sturdy.

Yes, I too think this is the opposite of a flared port.

You are building dbb's right? Are you puting the ports on the sides?

jc

[boom3]

If you have fast enough air flow and a narrow slot opening, you can get a reed effect at a given frequency. With the Cornwall, the air flow is so low a Mach number and the vent opening so large this is not an issue. In the early days of T/S'd "bass reflexes" we were impressed by the jets of air coming out of the ports as the woofers throbbed to heavy metal. We now know that's bad thing...a crude rule of thumb is, if you can feel air coming out of the port the port is probably too small. I can barely feel any air coming out of my Cornwall ports, except at very high volumes/low frequencies. I really doubt any turbulence created by this "mismatch" between the vent opening and the inner tunnel makes any difference.

[jwc]

Tom. I bet you can get by with removing this portion on side ports. I think you would still have good stability. I thought of this later after the build BUT my intention was to port it EXACTLY like the Cornwall but split.

jc

[chops]

You are building dbb's right? Are you puting the ports on the sides?

jc

Who is this question directed to?

And as a side note, I'm not really too concerned about the CW port design. In fact, it really doesn't bother me at all, especially since my CWs are crossed over at 50Hz, I doubt the port if even effecting the sound at all.

I was just curious as to why that lip on the port was there for all these years. []

[Tom Mobley]

Hi Guys

Just got back to the computer after being on the run all day. Thanks for your replies.

jwc, yes, I'm building DBB Cornwalls. I'm eliminating that lip. The floor of the box will be the floor of the port, essentially, I'm lowering the port opening to match the floor. I'm also making the opening the same size as the port. I just don't like that deal with the big lips.

chops,

>> Who is this question directed to? me, most likely.