DIY-project: JBL Kebnekaise S4365

[bubbleboy76]

Does flared ports alter this calculation much?

[Flodstroem]

Flared ports has nothing to do with tunings. They are flared for to be as silent as possible when the air is moving in and out

[bubbleboy76]

In the TS-document for the 1501fe woofer a kind of addon-gasket is shown, and I think the mounting-dimensions includes this.
Anyone who knows the mounting diameter and flange diameter and flange-depth without the "add-on"-gasket? I think I would maybe not use it, but another thin rubber-gasket instead.
I think 1501fe has the same dimensions as the other 1500/1501-variations.
Trying to design box without the woofers...
/Magnus

[JeffW]

The gasket doesn't go over the edge of the mounting flange, so the basket diameter is the true overall diameter.

This is a pair of mine, I can measure the exact OD of the basket if you want to compare against the printed dimensions.

[bubbleboy76]

The gasket doesn't go over the edge of the mounting flange, so the basket diameter is the true overall diameter.

This is a pair of mine, I can measure the exact OD of the basket if you want to compare against the printed dimensions.

Yes please, that would be very helpful. Thanks.
I am a bit confused right now, what is a gasket, and what is not.
on your pics, there is no gasket, right?

[JeffW]

Yes please, that would be very helpful. Thanks.
I am a bit confused right now, what is a gasket, and what is not.
on your pics, there is no gasket, right?

On the older drivers, there was a foam "gasket" that covered the edge of the surround. It would only act as a true gasket if the driver was mounted to the rear of the baffle, it really served no sealing purpose when the driver was mounted to the front. These appear to serve a similar purpose, just a cosmetic device to cover the surround edge as best I can tell, but now make of a harder rubber as opposed to the segmented foam as before..

[Mr. Widget]

Flared ports has nothing to do with tunings. They are flared for to be as silent as possible when the air is moving in and out

Yes, but a flared port does change the tuning frequency. Most box calculators assume a non flared port, if you substitute a flared port, the tuning will change a bit.


Widget

[Flodstroem]

Yes you are right Widget. I read a I think it was a patent or a scientific report from JBL regarding flared ports and whats happened round the openings av the port. There was also som calculations regarding the issue of changes of tunings frequency or calculations for port length
I didnt find the report now but what I remember there was no huge difference. After all if building a speaker from scratch one is forced to check tuning frequency no matter what program was used for the calculations for to get everything to work as intended.........

[grumpy]

for scale of the "issue":

just ran an example that used a 4" dia x 17" long duct and resonance at ~400Hz (40Hz system tuning)
... above was with no flares.

one flare: 16.5", 410Hz resonance, same 40Hz system tuning
two flares: 16.1", 421Hz resonance, same 40Hz system tuning

model doesn't deal with differences in turbulence in regard to "chuffing" noise, but I would expect less
when using flares of a significant radius.

[JeffW]

OD of the basket is right on the 15 1/4" spec, not surprising.

I never paid much attention to the first couple of pages of the transducer info post, but the picture there and cut away are accurate as to the construction.

http://www.audioheritage.org/vbullet...p?33555-1501fe

[bubbleboy76]

Thank you Jeff! So the outer hole inte the baffle needs to be a little little bit larger than 15.25" then, like 15.3" so it is not to tight? Any recommendations on hole OD size?

[bubbleboy76]

for scale of the "issue":

just ran an example that used a 4" dia x 17" long duct and resonance at ~400Hz (40Hz system tuning)
... above was with no flares.

one flare: 16.5", 410Hz resonance, same 40Hz system tuning
two flares: 16.1", 421Hz resonance, same 40Hz system tuning

model doesn't deal with differences in turbulence in regard to "chuffing" noise, but I would expect less
when using flares of a significant radius.

Interesting. Is higher resonant frequency better, in some regard?

Flodstroem, did you see where my theoretical port resonant frequency will be?

[grumpy]

If it moves away from in-band signals or resonant responses for that driver, sure.

The change is pretty marginal though, vs changing port diameter or number of ports.

[Odd]

Troels Gravesens has made some measurements.


Vent flange - does it have an impact on Fb?
http://www.troelsgravesen.dk/vent_tuning.htm

Tuning frequency vs. flanging:
No flange: 34.6 Hz
One end flanged: 33.9 Hz
Both ends flanged: 33.7 Hz.
Well, not much to write home about from this study! From no flange to double flange we lower the vent tuning by 0.9 Hz.

[pos]

I used that calculator, and it gave me accurate results:
http://www.psp-inc.com/tools2.html

It is meant for the flared precision ports sold on parts express, but works just as well for the JET70 ones that can be found in europe