4367 Cabinet

[sebackman]

Dear all,

I'm looking for the the cabinet data and port dimensions for the 4367. We have excellent data for the M2 and even CAD files out there, but I have not seen such data for the 4367.

I'm planning to build a pair but flirting a bit with the old L300 design (slanting front and glass top), albeit 2 way.

I will be using either 2430/D2, 2451SL or 2451Be. It will be fun to test them on the 4367 WG as I have not had that before. The M2 WG's I'm reasonable familiar with in different setups and do prefer the 4" driver on them.

-And of course BSS DSP active, but that will be a later story

Any input welcome.

Kind regards
//Rob

[Odd]

TR01853_JBL_Synthesis_4367_White_Paper_New_LR.pdf

[jmpsmash]

My mom has a pair in Hongkong. If no one else has gotten to it, I can ask her to measure the port dimensions. The white paper did say 4" and the drawing and text also shows dual flare. Seems like a regular port tube and not something fancy like the M2.

Which woofer do you plan to use?

[jmpsmash]

My mom has a pair in Hongkong. If no one else has gotten to it, I can ask her to measure the port dimensions. The white paper did say 4" and the drawing and text also shows dual flare. Seems like a regular port tube and not something fancy like the M2.

Which woofer do you plan to use?

Dual port with flares on both ends. The straight middle part of the port is 3". Total length including flare is 5". The outer diameter of the flare is 5"

Parts express supplier uses the straight middle part as the size. The 4367 port would be called as a 3" port instead of 4" port.

[sebackman]

Thank you for the info ODD and jmpsmash

Great info.

Can you please measure how long the non flared piece in the middle is. From the cut away it looks like the ports are made of 3 pieces, two flares and a straight piece in the middle.

Can you also, at your convenience, please make external measurements on the cabinets and port positions so I can put dimensions on Odd's drawing.

I have CAD data on the M2 ports and maybe these are the same (or similar)

Kind regards and thank you
//Rob

[Mr. Widget]

Can you please measure how long the non flared piece in the middle is. From the cut away it looks like the ports are made of 3 pieces, two flares and a straight piece in the middle.

Can you also, at your convenience, please make external measurements on the cabinets and port positions so I can put dimensions on Odd's drawing.

I have CAD data on the M2 ports and maybe these are the same (or similar)

Has anyone heard port chuffing in a classic 43XX or a 44XX or in a DIY system not using undersized ports?

I understand the purpose of flared ports, but other than improving the aesthetics of the port, and giving the manufacturer a clean finished solution that is easier to build in a manufacturing setting than cutting a tube squarely and cleanly finishing it as was required in those vintage systems, I am not convinced that we as DIYers need to follow their lead.

I bring this up because it is difficult to model the port tuning when using flared ports. You can measure, trim, measure, and repeat until you hit the target frequency, but this seems like an unnecessary hassle if performance alone is the goal. On the other hand if the aesthetics of a flared port is appealing to you, then I guess you have your work cut out for you.


Widget

[jmpsmash]

Thank you for the info ODD and jmpsmash

Great info.

Can you please measure how long the non flared piece in the middle is. From the cut away it looks like the ports are made of 3 pieces, two flares and a straight piece in the middle.

Can you also, at your convenience, please make external measurements on the cabinets and port positions so I can put dimensions on Odd's drawing.

I have CAD data on the M2 ports and maybe these are the same (or similar)

Kind regards and thank you
//Rob

Rob, you can find external dimension of the cabinet in the white paper linked to above. The white paper also describe in detail how thick the walls are (1 5/8" for the front baffle, 1" others) so it will be straight forward to deduce the gross volume.

The port has a straight middle section, which is not the same as the M2 which has a concave middle section. I doubt the port will be identical as the box volume and the 15" woofers are different.

The 4367 port seems to be something like this:

https://www.parts-express.com/Precis...be-Kit-268-350

The 4367 white paper also has the impedance plot, while in really poor resolution, the port tuning frequency looks to be around 32Hz.

The measurement of the straight port tube I already described in my previous post. I will try to get you the other measurements.

[RMC]

I generally tend to agree with Widget (post # 6) but for different reasons, and it seems to me that sebackman is somewhat condemned to replicate JBL's flared ports in the present case, based on Odd's sketch in post # 2.

I don't use flared ports, not because i don't believe in their benefit when properly designed, but simply because i have doubts about the science, if any, behind most flared tubes sold on the market for cheap. Their specs, other than dimensions, are rarely given, such as the Normalized Flare rate (NFR) value. Then its probably more a trial and error type of thing, or marketing.

That software or calculators are available on the Web for flared vents doesn't change anything in my view. Who wrote these, what are their credentials, what is the science (often obscure at best) supporting this stuff? We simply don't know, it may be good, bad, so so, who knows... Too much is unexplained and unproven about those things.

You think low-cost China, who manufactures most of the ports, flared or not, calculates all that stuff for proper, nevermind optimal, results??

In sebackman's case, replicating the original vents would possibly guarantee properly ENGINEERED flared vents. The use of conventional ports might not be as effective in that context, cab depth could become an issue or the use of an elbow might lead to a space problem.

The most advanced vent study and associated experiments that i know of is still the one from A. Salvatti, D. Button and A. Devantier, Maximizing Performance from Loudspeaker Ports, JAES, Jan/Feb, 2002, P.22. All together 62 pages long! Three seasoned Harman Engineers having quite a go at this, and leaving no stone unturned. I don't have time to retype what's on the pics so consider this as my retyping of that text.

Although, i don't recommend getting the long article from the AES ($) since its pretty heavy material, written by Engineers mostly for Engineers. However the real flared port science is there, no doubt. File size is too large to post, plus the AES holds the copyright on it. Therefore will only post the summary (which is public domain) and limit my quote to two paragraphs. The phrase "The tapered port ..." explains why i think JBL chose this type of vent here. The longer "end correction" being the reason why tapered ports behave as if they were longer.

Richard

[Anti K]

In physics it's pretty simple. Differentiating time.

When certain volume of air comes out from tube (at 1/2 sycle talking about speaker), then molecules of THAT amount of air have speed.
We can lower the speed - if amout of air stays same - icreasing diameter of tube.
(and it's quadric equatation!)

near the edges of tube:
- 'Neighrbouhood' molecules, outside of box, 'stand still'.
- Exhausted air molecules have speed and they tear together the standing molecules (at the region of edges of tube). It causes friction. Friction generates sound...

Its all about speed of molecules.

Now, while flared end, the speed of air molecules at the end of tube decreases - while tube diameter increases. And friction should be lower.
Simple as that.

In practice I rebuilt Soviet driver own time as low as 15Hz FS, made them move lower than 20Hz with generator.
(btw causes symhtoms as seasicness)
Only thing I heard was tube turbulence. Flared or no-flared.

What I have read - and it's understandable, there are different frictions between different materials (substances).
And plastiv (PE, PVC etc) are not the best materials for speaker's invewrter tube.
But metal is.
So, going deep it's total madness...


RMC could be right, if take some cheap plastic thing, we can only observe it aesthetically...
Which is basically same MrWidged sayd.

I see what works DIY, is bigger tube (less air speed) ... and bigger diameter makes tube same time longer.
Here was a topic in this forum, person built next to Everests pair of 2x18'' (4 psc total) SUBs, and stated same - did long tubes because *I don't like the hum of short tubes*
Or, take totally original flared parts (and we don't know the resources behind the research of these, M2 special shape for example)