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Old 7th March 2010, 11:12 PM   #11
kevinkr is offline kevinkr  United States
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Nesha based on GM's comments I think you will be fine as GM is really an authority on the Onken.. (His help was instrumental/indispensable in my successful project.)

Here is another Onken calculator which makes some interesting assumptions and calculates based on driver Vas, QTS, FS here at mh-audio - Onken Note that it returns a slightly different vent length and makes an assumption that port area will be 90% of SD.. (Note you can change N from 5.7 to 6.34 for an Onken alignment in this calculator)

So any way you cut it, it seems like this driver will work in an Onken alignment.
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Last edited by kevinkr; 7th March 2010 at 11:15 PM.
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Old 7th March 2010, 11:55 PM   #12
freddi is offline freddi  United States
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cool - only thing I wonder about in general is real signal power & transient handling of a small area driver in a large vented box. This Onken alignment is > 25% larger than Bill Woods "v-vent" reflex with 80l chamber and 41Hz tuning which was meant for 15" drivers (and driver Vas >150l IIRC) - is small signal simulation all to be considered?
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Old 8th March 2010, 04:27 AM   #13
GM is offline GM  United States
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Thanks for the confidence guys, but I just did the calculation to maybe help Nesha with using the Excel SS. Until we know more about how he arrived at his design and what aspect ratio cab he wants, mine is just an example.

I see now that his vent sizes total somewhat >Sd, explaining why his vents are longer, so I do recommend he reduce them to between 90-100% of Sd which will both shorten them and decrease cab size.

Then there's the cab's aspect ratio. An 8" driver doesn't need much vent area, but being a relatively high Q driver it requires a decent size cab by today's standards, so total vent height/2 equates to a Jensen Low Boy type, i.e. short and wide. If it were me, I'd go for a slender tower to get the driver up near/at ear height and circle the driver with round vent tubes same as Thuras's original BR patent test cab that the Jensen/Onken design is based on.

GM
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Old 8th March 2010, 04:56 AM   #14
GM is offline GM  United States
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Quote:
Originally Posted by freddi View Post
cool - only thing I wonder about in general is real signal power & transient handling of a small area driver in a large vented box. - is small signal simulation all to be considered?
Well, as the motor weakens (rising Qts), it requires an increasingly weaker air mass 'spring' to work against (bigger net Vb), so will have a wider ~flat BW than a lower Qt system. By the same token, an air mass >Vas means the driver's Fs gets dragged down a bit, lowering its effective Qt, so at a glance, small signal simulation is sufficient.

Where one gets into trouble with vented alignments though, especially higher Qt ones is not accounting for any/all series resistance that can turn a nicely damped alignment into an audibly under-damped one. In such a case all one can do is either lower its tuning (not practical with an Onken) or heavily stuff it to suit which may 'suck the life' out of a 'FR' driver.

GM
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Old 8th March 2010, 04:10 PM   #15
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Question, would it be better to seal and stuff a high Qts driver or try to port it given only a 'normal' sized box be used?

Also, some drivers have Qts of nearly 2. I bought a pair of PE Buyouts rated this high and their sound doesn't seem to change much regardless of the box they are in. They sound similar in a small sealed, large sealed or on an ob. Why is that? Is there a 'rule' of some kind when working with drivers with Qts close to 2? I think it's an oddball driver but i enjoy listening to it anyway.

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Old 8th March 2010, 04:43 PM   #16
GM is offline GM  United States
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'Port', as in use a max flat impedance TL to make it as aperiodic as practical to stop its excessive 'ringing', though it won't be very practical due to its extreme size since at a Q = 2, there is no need for an enclosure at all since its mass corner (2*Fs/Qts) will = Fs. At a Qts >2 then, we're into extreme acoustic mass loading of the driver to lower its Fs, so little wonder that different alignments of a typical cab's net Vb or OB size has little/no audible effect on its output.

Some years ago, I described a derived stereo from a mono source by using two 40-1271 'FR' drivers (~2.45 Qts) tied together with long studs and no baffles of any sort and it had no problem being ~flat to below 100 Hz with good enough self protection due to dipole cancellation without any high pass at the SPLs I used it for. A max flat impedance TL would be close to 8 ft^3 though, pretty big for a ~F3 = Fs (83 Hz).

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Old 8th March 2010, 05:12 PM   #17
preiter is offline preiter  United States
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Just being curious here. Can anyone explain why an Onken is different from any other ported box?
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Old 8th March 2010, 06:07 PM   #18
GM is offline GM  United States
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Its industrial chic style. I mean if you use a single large vent = to the same total vent area in a same net Vb placed ~ next to the driver in a similarly braced cab you'd be hard pressed to hear any difference between the two that couldn't be resolved with some fine tuning of the single large vent and why it's what I recommend from a performance POV.

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Old 8th March 2010, 06:28 PM   #19
tinitus is offline tinitus  Europe
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Due to the large port area of an Onken, it seems to me it needs a driver that would normally require a short port in BR
Seems to me its usually drivers that doesnt go very low
And an Onken allignment isnt reallly a sub either
Maybe it can be, I dont know
So far, I have only found relatively low Qts to give proper result, in spread sheet that is
The only Onken I have ever heard and owned was french LeAudiophile small Mahul Onken design, with 10" Focal

Even if Betsy-K is the version with biggest magnet, its still a driver with highish Qts, and relatively short Xmax, and probably best suited low power amps, and low SPL

To me it will be a matter of getting it sound its best, with good "tune" and bass, at low listening level
It does seem like a sensitive driver, and Im still curious about how much low and midbass will follow
Well, I expect it will need be a 2way, and a relative sensitivity around 90db
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Old 8th March 2010, 11:27 PM   #20
GM is offline GM  United States
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Quote:
Originally Posted by tinitus View Post
Due to the large port area of an Onken, it seems to me it needs a driver that would normally require a short port in BR
Seems to me its usually drivers that doesnt go very low
And an Onken allignment isnt reallly a sub either
Maybe it can be, I dont know
Right, it's based on drivers with a low Fs, Qts and high Vas such as the early Lansings, Altecs, etc. from the days of when high efficiency was the prime goal. Combined with the electronics of the day they were strong performers down to the mid 30s, plenty low for the vast majority of the period's source material.

No, it's not a 'sub' and never been touted as such, though there have been a few $$$ drivers that had suitable specs to work as an Onken sub.

Well, FWIW if the series resistance is very low the BetsyK's sim looks good to me if a half space ~T/S max flat alignment is acceptable. Like most 'FR' drivers, I imagine that lack of low distortion excursion will be its Waterloo, not whether or not it's a viable alignment.

GM
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