Sorry, my net-connection was down for 3 days, but I'm glad you guys had a little party without me. I know, ZM, I hoped GM would chime in...
Thanks for all answers... GM, I've got 32cm for L'vent (corrected length ) But never mind, I will adopt your calculations... and my wife is sending some kisses for smaller box.
I don't have some specific design goals, (to ignorant for this),but to build nice and balanced sounding speakers , at LOW listening levels. A speaker that 'opens up' at realistic levels is definitely Not my goal...
Thanks for all answers... GM, I've got 32cm for L'vent (corrected length ) But never mind, I will adopt your calculations... and my wife is sending some kisses for smaller box.
I don't have some specific design goals, (to ignorant for this),but to build nice and balanced sounding speakers , at LOW listening levels. A speaker that 'opens up' at realistic levels is definitely Not my goal...
Oh yeah, the only 'true' pair of Onkens I built were loaded with Altec 416-8Cs and they 'sang' like a flock of Wild Geese in a feather plucking factory, so had to scrounge up a lot of old socks!
Sure were sexy looking though and their ultimate owner was quite happy with them sans socks XO'd at ~500 Hz to much tweaked 511/802 horns until the wife sold the whole HIFI system in a divorce battle. Sure wish she'd a done me the courtesy of first refusal. Oh well, many folks like their foods, colors 'fat'/'rich', so why not their music also? I make no judgment, but it's not for me (except the food
), so don't make it a habit to suggest such alignments.Anyway, a ~typical measurement, notice the peaking at Fb and broadband peaks/nulls beginning around 190 Hz and extending out beyond 1 kHz if considerable vent damping isn't done:
GM
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re:reflex, I ran 4 ~RJ type 18" = ok on the little 6.4 cu.f.t box w. 103g mms - the 130g 18 sounded better midrange-wise in a Karlson-coupler than in the 8.2 cubic foot RJ - they're not quite RJ if aperture area isn't choked down. Since the vents are in close proximity to the cone, nearfield measurements to the cone are pretty much what happens
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You're welcome!
Thanks, I'd kiss back, but too old n' slow to dodge the slap.
As I eventually noted, your extra length is due to making the vent area larger than desirable. Vd = Sd is the max and frankly, in most cases is way larger than they need to be, so if you want to make the cab smaller than what I simmed, just reduce Vd to ~0.7x Sd which will shorten the vents some more, though you'll lose some of the Onken's 'fat' tone.
GM
I've no personal experience with the driver, only the box loading, so all I can say is that if you prefer an 'accurate' sound and/or have significant room boundary gain, then I imagine you'll need quite a bit of vent damping, otherwise you'll probably like it a lot if it doesn't 'color' the voices too much.
FWIW, women typically have much keener hearing everywhere but down low than men, so within certain loose limits I always let them decide what sounds 'best', especially through the critical mids/lower HF where their maternal instincts rule their hearing. This usually has the side benefit of 'smoothing the path' for loud playback and for future upgrades without having to budget for expensive jewelery, etc..
As the ancient truism goes, 'when mama's happy, everybody's happy and when she's not, nobody else is either'.
GM
Band-pass loading such as the Karlson does, i.e. the driver is loaded with at least a single front and rear chamber to increase its efficiency over a narrower band-width (BW) than sealed or vented does. The trade-off is that it rolls off the driver's mids/HF response above its pass-band, so at least in the case of typical 4th, 6th, etc. BPs, they are unsuitable for 'FR' use.
The Karlson is essentially an 8th order BP, but with a large exponentially tapered slot in front of the driver to try and 'let through' as much of the driver's beaming mids/HF response as practical while still adequately front loading the driver, but me and many others prefer XOing it at around 250-500 Hz depending on the person and using a large wide angle horn for the rest of the BW.
GM
Oh yeah, the only 'true' pair of Onkens I built were loaded with Altec 416-8Cs and they 'sang' like a flock of Wild Geese in a feather plucking factory, so had to scrounge up a lot of old socks!
Oh well, many folks like their foods, colors 'fat'/'rich', so why not their music also? I make no judgment, but it's not for me (except the food
Anyway, a ~typical measurement, notice the peaking at Fb and broadband peaks/nulls beginning around 190 Hz and extending out beyond 1 kHz if considerable vent damping isn't done:
GM
I can confirm the last comment on peak/nulls and vent damping from measurements (in the port mouths) and tweaking on my large Onken boxes. I settled on a certain amount of in cabinet damping and came to the conclusion that the remaining garbage I was measuring in the ports apparently isn't (that?) audible - at least in so far as detracting noticeably from the performance, so I never really addressed it. I cross over at 800Hz to a JBL mid-range horn. The overall system response in room is pretty flat actually. Last time I checked better than +/-2dB from 100Hz - 10kHz.
As GM knows I'm still very happy with the Onkens. The original Thura patent is quite interesting and I have actually heard a bass bin built using this approach - sounded very good too.
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I tried to recalculate GM's onken into Thuras box with 12 ports,this morning, and I took Vvent=5,222l and divided it by 12 ( my math English is even worst),keeping L' =22,9cm, I come to vent diameter of 5cm. That means front baffle width of at least 40cm, and WAF suddenly exponentially falling ...
Actually there's thirteen (13) vents in Thuras's speaker and as I noted, you don't need the Onken's Vd = Sd vents. Indeed, considering the BetsyK's high Qes, the higher resistance of many small vents is theoretically a plus, making for a unique looking ~Fonken alignment, but I'm down to repeating myself, so will shut-up.
Good luck with whatever you wind up with and looking forward to a review!
GM
Indeed, considering the BetsyK's high Qes, the higher resistance of many small vents is theoretically a plus, making for a unique looking ~Fonken alignment, but I'm down to repeating myself, so will shut-up. Good luck with whatever you wind up with and looking forward to a review!
GM
Yeah, damp down the the pipe's fundamental and so goes its harmonics, so while you can hear noise at the end of the pipe, it has little impedance matching radiation, so is pretty quiet once you move back a meter or so and probably why 4 ft (USA) until fairly recently/1 m most everywhere else became the minimum standard measuring distance.
That said, I still prefer Olson's? simple snap switch 'click' test (or use an impulse response if available) to critically damp vented systems rather than 'brute forcing' it via cab stuffing.
GM
hey GM - what's a good way to make the click tester?
G.A. Briggs oscillograms
G.A. Briggs oscillograms
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Agreed, I went to the next level and end loaded some wide BW paper cone tweeters of days gone by in a folded TL loading (tube-in-tube), so with the insides all painted matte black, at a glance it looked like the tweeter was floating in a larger cylinder, especially since the cabs were shot with '68 Corvette Polar White, probably the whitest/brightest gloss white ever available to the general public.
Kinda weird to hear a nominally 1.5 kHz tweeter play with solid output all the way down to its ~500 Hz Fs. Never got around to doing an Onken variant though, large enough cardboard tubes were considerably more expensive at the time than marine grade plywood.
GM
Well, mine's just a single pole double trow (S.P.D.T.) flip 'snap' switch from a wrecked '59 A-H 'bugeye' Sprite's dash taped to a 1.5 V 'C' battery holder with some alligator leads and if your amp has enough output impedance to audibly affect the system Q, then ideally you want a resistor of the same value in series to account for it. Me, I just have a cheap RS 25 ohm pot in series and use a meter to set it. These type switches are still available most everywhere car or electrical stuff is sold last time I noticed.
Replace the toggle handle with a black Bakelite one and replace the solder tabs with tiny screw threaded tabs and it would look like mine: SPDT Flatted Metal Lever Toggle Switch - RadioShack.com
GM
Replace the toggle handle with a black Bakelite one and replace the solder tabs with tiny screw threaded tabs and it would look like mine: SPDT Flatted Metal Lever Toggle Switch - RadioShack.com
GM
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