External ports?

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purplepeople

purplepeople

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Joined 2003
#1
I am curious... does anyone have pictures of an enclosure with an external port? Yes... I know that a TL could be described as a tuned port for a box of zero volume, so let's just leave that out, ok? Whatever shape the speaker took would definitely fall into the classic "look" of audiophile equipment.

🙂ensen.
 
#2
I would say the Onken enclosure probably qualifies as an enclosure with external ports.

Interesting thought. The Onken is by the Jensen company. A fellow named Novak was an engineer at Jensen. In the mid-fifties, Novak published a paper essentially outlining the correct way to build a bass reflex speaker. It was not as detailed as the Thiele and Small papers, but it gave the reader pretty much everything he needs to build a proper bass reflex. In other words, Novak's paper was a like a summary of Thiele and Small's later work, only he published it years before they published their papers!

Before Novak, everyone was pretty much shooting in the dark about the bass reflex design. Thiele and Small had much greater effect in the popularizing of the ported design, but Novak laid out what you needed to know.

Well, the Jensen company claims that the Onken design gives superior performance to a normal bass reflex. I don't know when the Onken design was created, but if the same company which essentially figured out the bass reflex design claims an advantage for the Onken over the normal bass reflex, it does give some credence to the idea that the Onken is something special. I guess it depends on when the Onken was created-before or after their engineer, Novak, figured out the bass reflex design.
http://www.studiomaudio.com/onken.html
 

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#5
If you are looking to build these, it seems to me that you can modify the design of the Onkens ever-so-slightly to emphasize the separateness of the ports. Would make construction somewhat more complex, though. Hard to imagine that it would affect anything sound-wise.
 

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#6
Thanks.

These are very interesting, kelticwizard. The slotted ports appear to predict the current line-up of Genelec studio monitors. Maybe there is a common thread between the two.

Also, if you were to flatten out the internal surface area, the result would resemble a very short transmission line. The overall "taper" seems to be similar as the ports area is quite a bit larger than your modern tube port.

There is no indication what kind of driver was ideal for the various sizes of enclosure and port. I am guessing that all this was before Thiele and Small so the measurements must have been a generalization for various drivers available in that age.

🙂ensen
 
#7
purplepeople said:

There is no indication what kind of driver was ideal for the various sizes of enclosure and port. I am guessing that all this was before Thiele and Small so the measurements must have been a generalization for various drivers available in that age.
🙂ensen
Click to expand...

Actually, what I am trying to say in post #2 is that Jensen had all the Thiele Small stuff figured out in the mid fifties. Their engineer, Robert Novak, published a paper in the mid fifities that laid bare the relationship between Vas, Vb, Fs, and Qts. From this, one could build a reflex box that conformed to Thiele Small principles. I forget if Novak's article went into such things as the proper diameter of the vent to avoid port noise. It was just a couple of pages that dealt with the bass reflex. But those couple of pages gave you everything you needed to know about the proper size box and box tuning for a bass reflex with a driver of a given Qts. He had charts that showed the response for drivers with different Qts and box sizes.

Thiele and Small's articles were much more thorough and elaborate. But Novak had the whole thing nailed years before they did. I can scan and Email the article for you if you wish. Novak-almost forgotten and deserving of much more appreciation. 🙂

Sorry for going on like that. I just like people who do good work to get recognition.

originally posted by purplepeople
Also, if you were to flatten out the internal surface area, the result would resemble a very short transmission line. The overall "taper" seems to be similar as the ports area is quite a bit larger than your modern tube port.
Click to expand...

Interesting point. I noticed the size of the ports too. All the more intriguing because, if these Onkens came out in the mid fifities or later, then we know Jensen had the later-to-be-known-as-Thiele-Small principles already, thanks to their engineer, Robert Novak. So, if Jensen is still claiming an improvement over the regular bass reflex, then maybe this Onken thing really does add something over the regular bass reflex.

By the way, there is an XLS program for Onkens I saw on the internet. Do you want the link?
 
#8
"If you can't hide it make a feature of it."

purplepeople said:
I am curious... does anyone have pictures of an enclosure with an external port?
Click to expand...
When you say "external port", I was imagining a box with the cylindrical tube poking out for all to see. You could really go to town with this concept, e.g. make the box roughly the shape of an old fashioned ocean liner with the port as the smoke stack. 😎
 
#10
Anthropomorphic abberations.

If you did a boat version like I suggested you would be better off sticking the vent tube out from the =left= side. :nod:
**************
Now for something that re-defines the outer limits of goofiness:
How about a speaker box that has a large woofer at the bottom centre and and pair of smaller speakers at each upper corner. These upper speakers should have shiny or some other way conspicuous centre dustcaps so that they look like a pair of eyes , the woofer a large mouth. Now for the piece de resistance - have the port sticking out in the centre like a silly-looking nose. I'd be willing to bet that nobody has ever done *that* before. :clown:
 
#13
I'm very interested in building one of these things, although I know nothing about them. I've designed and built only closed boxes and ported boxes. I want to build a transmission line but would also like to do something else. So I'm going to investigate this furthur. If anyone has any design info for this thing, pass it along.

Pete
 
#16
Ashok:

The article that I was going to send Purplepeople was by Jensen engineer Robert Novak, where he shows that he know all the Thiele Small stuff before the publication of their famous papers. It has nothing to do with Onken enclures. However, I will send it to you anywa, if you want. Let me know.

The xls program does not appear on the search engine like it did the other day. Looking for Onken designs for purplepeople, I came upon a Google listing for an XLS program. However, when I look into my google archives, I cannot find the same listing.

Happily, Remy has found what I am sure is the same Onken XLS program. I mean, how many can possibly have been written? 🙂
 
#18
Purplepeople:

Hold on. Might not be done yet.

There is a fellow on this forum who has invented a system that uses an external port in a reflex/transmission line system. I will Email him and see if he wants to introduce it in this discussion.
 
#19
#20
kelticwizard said:
Purplepeople:

Hold on. Might not be done yet.

There is a fellow on this forum who has invented a system that uses an external port in a reflex/transmission line system. I will Email him and see if he wants to introduce it in this discussion.
Click to expand...

Yes, I designed a speaker in 1990 which was based on the DALINE principle. This is where you add a line to a box. I used four full-range drivers with no crossover and used the line to extend and 'deepen' the bass (reduce 2nd harmonics).

With my design (Seventh Veil - System IV) the stand was used as the transmission line. It was built of rectangular section steel tube and is in three sections (the sound goes down the back, up the middle and down the front where it emerges from the bottom of the stand). I took out a patent on this, calling it the 'StandLine' but anyone is welcome to use this concept for a DIY project (if they're crazy enough).

The link is: Decoupled Anti-Resonant Line from Seventh Veil (circa 1990).

I'm happy to answer any questions you may have.

Things have been hectic lately as I've just finished launching my new system at the High End Show in Frankfurt. I'll post a full report later, if anyone out there is interested.

Good luck
Steve
 
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