# Onken Bass Cab for Center



## erwinbel (Mar 23, 2010)

I have found info on how to build a Onken Bass Cab for a 15" woofer. Altec 416-8B is the usually used driver. I wonder if I could use the *Eminence Deltalite 2515* (15") instead? I want this for a custom center speaker placed behind a AT screen. Mid-high cab will be a vertical d'Appolito (MTM) with two Troels Gravesen JA8008 (8") mids. All this to stand his own in comparison to the L+R (DTQWT-12 by Troels Gravesen), which each use one of the JA8008 mids plus two Eminence Deltalite 2512 (12"). Woofer surface of one 15" is close to two 12".

The Onken:

_Figure 1 shows a horizontal chest version of the Jensen Bass Ultraflex enclosure (AKA Onken). Assembly procedure is evident from the drawing as is the various panel sizes. The front baffle is shown removable for easy access when the cabinet is built in. The particular shape is not important. What is important is the total interior volume, the duct area and the duct length._








_Table 1 shows several values for the various dimensions of this basic type of enclosure. If one of these do not meet your needs simply choose inside dimensions for height A, width B and depth C so that the total interior volume A x B x C equals 13,300 cu. in. Since the duct height is the cabinet height A, calculate the duct width D so that the total duct area (two ducts) 2 x A x D equals 134 sq. in. The duct length must always be 8". It is not desirable to chose any one dimension greater than three times the smallest dimension; this encourages organ pipe resonance effects that are undesirable. Absorption material on top and bottom is recommended just as described for the corner type Bass Ultraflex. Here then is an enclosure design you can tailor to any need.
_








I want to use these internal dimensions (panels are 1") if the former sizes apply to the Deltalite 2515:
H 450 mm (17.7")
W 1150 mm (45.3")
D 420 mm (16.5")
= 218 liter (13,300 cu. inch)
Port Width = 96 mm (3.8") to get the required surface of 865 cm2
Port Depth = 203 mm 
I want to stay low so it stays just below the screen, while the mid-high cab sits behind the AT screen.

Specs of Deltalite 2515:
http://www.eminence.com/speakers/speaker-detail/?model=DeltaliteII_2515

Specs of Altec 416-8B:
http://images.owneriq.net/download/images/1/15d82097-5a94-426b-83c1-2a8dfe1525ea-000001.png

I could ofcourse just build a normal 119 liter vented box (or even 2) but I think the Onken is cooler to make and it is also more in line with the design of the floorstanders.


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## fbov (Aug 28, 2008)

Maybe I'm missing something, but what's the difference between an "Oaken" and a dual side slot ported box?

If none, then build a normal vented box or two, but use dual side slot ports! Seems to me the simulation would be the same, but with the round-to-slot dimensional conversion, and use of appropriate T/S parameters.

Have fun,
Frank


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## GPM (Jan 14, 2007)

The Onken is a narrowly defined alignment with a very specific layout that just looks like a Jensen Ultraflex, which AFAIK used a different reflex design routine based on the driver's response in a closed cab.

GM


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## GPM (Jan 14, 2007)

erwinbel said:


> I have found info on how to build a Onken Bass Cab for a 15" woofer. I wonder if I could use the *Eminence Deltalite 2515* (15") instead?


Your alignment is quite a bit different than an Onken's n = 6.34, but there's nothing magical about them, so no reason not to construct them for its 'look' to suit your app other than box tuning adjustment is limited to damping one or more vents and/or adding more damping in the cab proper.

GM


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## erwinbel (Mar 23, 2010)

The idea is to make something that is suitable to put behind the AT screen and somehow of a similar philosophy than the main and surround towers. Indeed, I could just do a vented box of the recomended size + port and be done with it, but maybe the sound will be slightly different then the others then? Anyways, Troels Gravesen will be asked to give his approval of anything I come up with, so he can make a crossover for the midcab and the basscab.

Here's the Troels Gravesen designs:
*the DTQWT with 2 Deltalite 2510 (10") for surrounds (I have the kit here, but did not find the time / courage to start the build)








*the DTQWT-12 with 2 Deltalite 2512 (12") for L+R 








These cannot be put behind the screen since the woofers are backfired. Hence the idea for the Onken with 1 2515 (15") or two 2512 (12").

Another design that comes to mind is the Transmission Line, such as PMC uses...


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