Horizontal Onken (Honken?)

[Matty]

Hi all,I have a pair of refurbished Altec 416-8As that I'm building a cabinet for, and I thought I'd try the Onken cabinet design. If I use the Onken box dimensions, port area and port volume would this design work horizontally? I'm going to have a large Le Cléac'h style horn on top of the cabinet, so if I use the original Onken design the horn ends up being too high up for me. I'm hoping the horizontal box will be the best of both worlds. Cabinet plan is attached (I think)

[RMC]

Hi Matty,

Welcome aboard the Lansing Heritage.

Not sure i understand correctly your idea, but the way i see it you'd have a low-boy bass cabinet with a horn on top of the box?

I don't see anything wrong with the principle as long as you stick to the rules of the art, such as proper box proportions, etc. Same for slot vents, Altec has a note about this.

Btw which dimensions are you using, inches, centimeters or other? 23.3, .6, .80 and .95 don't seem to make sense to me. Regards,

Richard

[Matty]

Hi Richard,Thanks for your reply. Dimensions are in cm and a little dot has appeared just before the numbers - the dot shouldn't be there.Yes, basically it'll be a low boy bass cabinet using all of the Onken dimensions but the cabinet is wider than it is tall. The original Onken cabinet is 95cm (H) x 80cm (W) whereas this one would be 80cm (H) x 95cm (W).I'm hoping this will perform the same as the original Onken design, but just wondering if there's anything in this modified design that might cause issues. This is my first speaker build so I'm being extra cautious.

[RMC]

Personnaly i don't see why it wouldn't work horizontally, at least for the bass enclosure, since low frequencies are pretty much omnidirectional up to a point, and the ports having a free air flow path which appears to be the case. A cabinet may have different shapes but the most important is that net box volume and tuning frequency are still respected.

Can't help you with the horn though since i'm not familiar with that one. Good luck with the project.

Richard

[Matty]

Thanks Richard. I was a bit concerned that the space behind the driver is close to a cube shape, I’ve read that having too many sides that are similar dimensions will result in standing waves. The ports are 40.5cm long.The horn is an Azurahorn Horn, made in Australia and it’s currently hooked up to JBL 2420 compression drivers. Sounding really nice.

[RMC]

Matty,

Since you're cloning an existing design the box shape and dimensions are what they are. As you mentioned cube shape and standing waves are usually not desirable. But yours isn't really a cube, at least not a perfect one where all dimensions are the same. Yours vary. (Btw Weems shows a small box that really looks like a small cube at first sight (similar to the well-known Auratone cube). However, the box ratio is 4: 5: 6 so its not a real cube).

Normally, in speaker building you try to avoid a few sins: cube shape, multiples of a dimension (e.g.1x2x4 ft.), also avoiding any dimension that is more than 3 times any other.

Its nice to see someone building his first pair of speakers and having a concern about proper box shape. Doing it right often doesn't cost more than a poorly designed one.

Many people here have difficulty with box sizing and shape (box ratios) but when you know how to work with this its actually pretty simple, no fancy equations or formulas, the most "difficult" step for standard cabs being doing a cubic root (not square root) with a pocket calculator! I've learned this many years back from Alden (mathematician) and D'Appolito. I've never been a "prisoner" of plans or predetermined dimensions since. Actually i wrote a draft procedure (hand written) to do this but haven't had time yet to put it in a presentable format to post. One day...

Richard

[Matty]

Okay thanks for the feedback Richard and it's good to know I haven't broken any of the golden rules of box design.I've changed the box dimensions slightly so it's now 5cm wider and 5cm less in height. Same port area and volume etc. Will post a pic of the final build.

[RMC]

Matty,

When changing the box dimensions from 1rst sketch to the new one you seem to put a foot in trouble...

Your woofer now looks like its perfectly centered in the cab and this tends to promote standing waves in the box!

The previous woofer location appeared off-center height wise which is better. Preferably the woofer should be above exact center or below center. In this case, as i understand your intention with regards to horn location, then the woofer should probably be above center height wise.

Sorry for making you work but i'm only trying to help and keep you out of trouble. Regards,

Richard

[Matty]

Oops! No worries, I can move the woofer up to a maximum of 120mm from the top of the box.

Thanks for your help on this Richard