Orca marketed an Onken in the mid 90s designed by Joe Dappolito using Focal Audiom drivers it was sold as the Maximus kit in the Uk by Falcon.The ports are at the bottom of the enclosure in this design just the cabinet wall thickness from the ground(1.5 inches).Any body else on the forum build one of these?
JoshK said:
Everything is in the paper "Simple formulas and graphs for design of vented loudspeaker systems":
http://pagesperso-orange.fr/francis.audio2/Audiophile26_dec82.pdf
So it's Snyder actually. Pretty old stuff. Like Onken cabinet.
Mounting the 414 driver
Gentlemen,
I am making plans for building a 2-way with a 414 crossed over to a 802 driver in a 32 horn. I haven't decided yet whether to build a BR or Onken for the 414.
My question concerns the mounting of the 414. Most pix show it mounted on the back side of the front panel. Wouldn't it be better to mount it on the front and have it recessed so there is a smooth transition from the 414 frame to the front panel of the cabinet?
Thanks.
Dave
Gentlemen,
I am making plans for building a 2-way with a 414 crossed over to a 802 driver in a 32 horn. I haven't decided yet whether to build a BR or Onken for the 414.
My question concerns the mounting of the 414. Most pix show it mounted on the back side of the front panel. Wouldn't it be better to mount it on the front and have it recessed so there is a smooth transition from the 414 frame to the front panel of the cabinet?
Thanks.
Dave
Greets!
The older drivers have frames designed for only rear mounting, though with either careful woodworking or a thick neoprene gasket it can be front mounted and recessed if a thick enough baffle is used. The later frames can be mounted either way. Note that these ribbed frames can be fairly easily cracked when mounted this way if the mounting screws are over- and/or unevenly tightened.
Since compression horns 'throw' all but their lowest frequency output away from the baffle, there's little baffle interaction beyond the woofer's, so basically at the WLs involved, recessing it isn't the big deal it is with small point source drivers on narrow baffles. Really, the wider the baffle, the less potential problem this can be, with ~30" being the point of diminishing returns in most near/at rear wall apps.
FWIW, back when I had keen hearing, I experimented and couldn't hear any difference with >12" drivers, even very wide BW ones, so for me it's just a cosmetic thing. Note that if it's the sonics you're concerned about, the eigenmodes (standing waves) across the inside of the mounting gasket can be audible in some cases, especially when rear mounted where there's typically a double cavity, so a phase plug in lieu of a dust cap (DC) can be a worthwhile tweak when done right along with rounding over the baffle cutout at ~45 deg. in such situations. Unfortunately, drivers with vented DCs must have the phase plug suspended in front of it.
GM
The older drivers have frames designed for only rear mounting, though with either careful woodworking or a thick neoprene gasket it can be front mounted and recessed if a thick enough baffle is used. The later frames can be mounted either way. Note that these ribbed frames can be fairly easily cracked when mounted this way if the mounting screws are over- and/or unevenly tightened.
Since compression horns 'throw' all but their lowest frequency output away from the baffle, there's little baffle interaction beyond the woofer's, so basically at the WLs involved, recessing it isn't the big deal it is with small point source drivers on narrow baffles. Really, the wider the baffle, the less potential problem this can be, with ~30" being the point of diminishing returns in most near/at rear wall apps.
FWIW, back when I had keen hearing, I experimented and couldn't hear any difference with >12" drivers, even very wide BW ones, so for me it's just a cosmetic thing. Note that if it's the sonics you're concerned about, the eigenmodes (standing waves) across the inside of the mounting gasket can be audible in some cases, especially when rear mounted where there's typically a double cavity, so a phase plug in lieu of a dust cap (DC) can be a worthwhile tweak when done right along with rounding over the baffle cutout at ~45 deg. in such situations. Unfortunately, drivers with vented DCs must have the phase plug suspended in front of it.
GM
Ah Mr GM , while you're on the thread ..
I've wondered a lot lately about how people design those Front-horn + BR combinations as per Altec , for instance I read Christian Rintelen's article on the 'Blue Thunder' system for a 15" , in SP magazine a few years ago . There wasn't much info on the detail-design when it came to the crunch .
For one thing it would seem to me the combination would be very much more efficient above eg. 150Hz where the horn starts to load , giving a sort of low-bass/upper-bass mismatch .
Any thoughts ?
MJ
I've wondered a lot lately about how people design those Front-horn + BR combinations as per Altec , for instance I read Christian Rintelen's article on the 'Blue Thunder' system for a 15" , in SP magazine a few years ago . There wasn't much info on the detail-design when it came to the crunch .
For one thing it would seem to me the combination would be very much more efficient above eg. 150Hz where the horn starts to load , giving a sort of low-bass/upper-bass mismatch .
Any thoughts ?
MJ
It's simple enough, taken to it's logical extreme you make the rear chamber Vb large enough and tuned high enough that the port's output extends the horn's LF response, so if the horn's F12 is 80 Hz, then you want a +12 dB tuning peak at 80 Hz with a filter Q of whatever the horn's roll off slope is. It's just a crude way to ~reactance annul a too short/small horn.
The A7 was designed at a time when high output impedance plus variable DF (adj. bass boost) ruled, so the speaker's response tracked the driver's impedance, ergo the BR's second tuning peak was used to extend the horn's gain BW and bass boost used to fine tune it. The high output impedance also smoothed/extended the two horn speaker system.
In today's vanishingly low output impedance 'world' though, CD horn EQ is required on both to achieve a similarly flat response over the same BW, eating up most of its efficiency. IIRC it drops the A7 to ~96 dB/W/m/2pi space.
Anyway, HornResp can now sim these, though unfortunately not driven by a high output impedance amp.
GM
The A7 was designed at a time when high output impedance plus variable DF (adj. bass boost) ruled, so the speaker's response tracked the driver's impedance, ergo the BR's second tuning peak was used to extend the horn's gain BW and bass boost used to fine tune it. The high output impedance also smoothed/extended the two horn speaker system.
In today's vanishingly low output impedance 'world' though, CD horn EQ is required on both to achieve a similarly flat response over the same BW, eating up most of its efficiency. IIRC it drops the A7 to ~96 dB/W/m/2pi space.
Anyway, HornResp can now sim these, though unfortunately not driven by a high output impedance amp.
GM
GM said:
Many thanks for the explanation, GM. I always wondered how the short basshorn in the A7 was supposed to work - it boosts the mids (obviously), but I couldn't see how it did anything below 160 Hz or so. The reduced rear chamber volume behind the bass driver and the high Z source impedance (I think it was called "unity coupling") would make a big difference to warm up the sound. Not the smoothest response, but this was decades before Thiele/Small analysis.
A bit off topic, but I can't resist asking - what's your take on the merits and demerits of paired 414's vs a single 416 for Onken-like duties (with an 800 Hz crossover to the mid/high horn)? I've got a friend in the Northwest who is contemplating an Onken variant and is curious about just this question. The paired 414's has the charm of higher efficiency and following in the footsteps of the 9844 studio monitor.
Lynn Olson said:
Okay, I'll jump in now . . . I'm Lynn's friend from the Northwest. I am planning a speaker project that has its roots in Lynn's Beyond the Ariel thread. The idea is to use the AH-425's with GPA 288-16H's on top, but use some type of BR approach (Onken or otherwise) below, rather than OB.
Lynn first suggested a 414/Petit Onken, and I have looked at some other ideas as well, such as a 416 (or 515?) in a 612 or 620, or perhaps a ~6 cu ft cabinet with paired 414's. I can't accommodate anything wider than the Petit Onken. I've been reading everything I can find about these things...lots of opinions out there, without question.
Might a Petit Onken with paired 414's be worth trying?
BTW, my AH-425's arrived just today. Martin does beautiful work!
Gary Dahl
Gary,
Good to see you joining the discussion. I've waded through most of the "Beyond the Ariel" thread but it's hard to digest all of that at one time.
Wouldn't a single 414 offer better potential for a smooth, coherent blend to the horn, as compared to a 515, 416 or pair of 414's?
I recently had the opportunity to hear a single 414 in a 3.2 cu ft BR based on the 614 design, and the bass extension was pretty good. I think it will be sufficient for my needs without any sub. And I definitely like the idea of a smaller cabinet than would be required for the 15" drivers or a pair of 414's.
Dave
Good to see you joining the discussion. I've waded through most of the "Beyond the Ariel" thread but it's hard to digest all of that at one time.
Wouldn't a single 414 offer better potential for a smooth, coherent blend to the horn, as compared to a 515, 416 or pair of 414's?
I recently had the opportunity to hear a single 414 in a 3.2 cu ft BR based on the 614 design, and the bass extension was pretty good. I think it will be sufficient for my needs without any sub. And I definitely like the idea of a smaller cabinet than would be required for the 15" drivers or a pair of 414's.
Dave
what about a 2.5 way design, with a low tuning frequency ("banana" response curve) using one of the two 414 as an helper woofer for the low frequency, with a 6db/oct LP filter around 100 or 150Hz ?
This is what JBL did in its 4435, and the recently in the Everest II.
That way you only have one woofer crossing to the horn, you gain a real in phase +6dB boost in the bass, and you also have much more freedom for choosing the second woofer's location on the baffle.
This is what JBL did in its 4435, and the recently in the Everest II.
That way you only have one woofer crossing to the horn, you gain a real in phase +6dB boost in the bass, and you also have much more freedom for choosing the second woofer's location on the baffle.
Salectric said:
Hi Dave,
It very well might. But I have read some very favorable comments about 416's and dual 414's, and have an open mind. It's hard to get an idea of the relative merits of these ideas without having a chance to hear them for myself, and I'm not sure that my wife would be to pleased if I decided to try them all.
I do have some experience with 416's, but they were in 828 cabinets. At that time, I was using 311-60 horns with 802 drivers (with adaptors). Sounded quite good...wish I still had that huge room!
pos said:
A very interesting idea. Do you think this would work in an Onken enclosure, or would it be better to go with a conventional BR?
Thanks for the welcome and the suggestions!
Gary Dahl
Gary,
I recall someone in Lynn Olson's thread speculating that a pair of woofers would be better in separate cabinets. For instance, one could be in a smaller sealed cabinet and the other in a conventional BR or Onken. The purpose would be to avoid interaction between the two drivers.
pos,
I thought of the 2.5 idea since that seems to work successfully in a number of commercial designs. In my case, I decided not to go in that direction because I will be using a low power SET amp and I don't want to add any additional loading in the bass. Plus, the extra cabinet size required.
Dave
I recall someone in Lynn Olson's thread speculating that a pair of woofers would be better in separate cabinets. For instance, one could be in a smaller sealed cabinet and the other in a conventional BR or Onken. The purpose would be to avoid interaction between the two drivers.
pos,
I thought of the 2.5 idea since that seems to work successfully in a number of commercial designs. In my case, I decided not to go in that direction because I will be using a low power SET amp and I don't want to add any additional loading in the bass. Plus, the extra cabinet size required.
Dave
I have made some simulations using winisd, and for the 414-8C and 414-8E (414-8G looks very differenet) a 80L box tuned around 30Hz looks like a good candidate for a 2.5 system. That would require a total of 160L for the two woofers.
I don't know how that would translate to an onken box but I suppose the vents can be calulated much the same way?
For comparison, in the JBL 4435 each 2234H was tuned to 26Hz in a separated 140L box.
I don't know how that would translate to an onken box but I suppose the vents can be calulated much the same way?
For comparison, in the JBL 4435 each 2234H was tuned to 26Hz in a separated 140L box.
Lynn Olson said:
Hey Lynn, long time no 'speak'!
You're welcome!
Yeah, the old matching impedance/DF=1 ideal for max power conversion. Elegant engineering, but takes either really large horns like the pioneers of audio used or max flat impedance TLs to make it work well down low.
I have a different take on the impact of T/S in that the pioneers of audio used the various values of T/S (mass, compliance, resonant ckts., etc.) plus wave equations to arrive at technically ideal alignments, etc., while T/S condensed/packaged this 'black art' into a relatively simple design routine that allowed all the 'wannabe' speaker designers who didn't/won't/can't learn all the underlying physics.
Anyway, the Onken in its n = 6.34 alignment is just a big vent reflex, so has minor peaking at Fb with some vent pipe harmonics comb filtering with the driver's output that some find euphonic, ergo it will work fine with any driver's specs that doesn't make the vents too long and even then you can damp them to quell any excessive mids' coloration.
AFA choosing between dual 414s Vs a single 416, this is mostly about personal preference Vs XO point/slope and how closely you want to match the horn's polar response on/off axis through the XO's BW.
At 800 Hz, a 414 is theoretically beaming at ~125 deg whereas the 416 is at ~96 deg with tandem 414s at 57 deg horizontally and tandem 416s ~43 deg, so without a polar response of the horn we're back to whether a 414 sounds better than a 416 through the XO BW and whether dual vertically oriented or tandem 414s sound overall better than a single 416.
Personally, having had dual vertically oriented 515s with various horn designs for just shy of 40 yrs now and compared them to many other drivers, layouts, I've always preferred XO points/slopes that ~matched polar responses as much as practical to get as wide a 'sweet spot' as practical and the only thing I would do differently WRT a non-horn alignment with my system is to orient the 515s in tandem to better match a 511 or similar radial horn through my preferred 500 Hz XO point and minimize the driver's vertical spacing. I still get irritated when some musical passages climb up/down the way too far apart acoustic centers when I can't sit far enough away for them to appear as a single source. This is a problem with 811/dual vertical 414s also.
So in a long winded way, if you sonically accept a ~1 WL tandem woofer spacing at the high end of a ~800 Hz XO off axis, then a 9844 style cab with an XO tailored to work better off axis than the original would be hard to beat and if width and/or its rather weird 'look' if made into a floor stander isn't a problem, then the Onken style cab is as good a reflex choice as any.
GM
David McBean said:
Hi GM,
Try setting Rg to a non-zero value.
Kind regards,
David
Greets!
This will mimic VC heating and the effect of passive XO components, ergo the effective Qts increase that I've ~given up trying to get folks to take into account when doing a box design, but won't show the impedance tracking of a tube amp: http://www.geocities.com/dmitrynizh/LoadingTubeSE.htm
GM
GM said:
Greets!
Horn details?
Why such a large driver for an 800 Hz XO point?
Hmm, tandem 414s won't fit in the Petite's width even without the vents.
If you're planning to drive them with a high output impedance amp, then I vote for a 515B Onken.
GM
I'm the guilty party here, so I might as well answer. Neither Gary, John Atwood, nor I have warmed up to the sound of small-format compression drivers, but we both like the relaxed and effortless sound of the large-format mids. We've also fiddled and had good results with supertweeters, so the HF rolloff and beaming of large-format is not an issue. What has been an issue is the sound of the horns themselves - Gary is a classical musician and former eXemplar owner - he liked the bass, the highs not so much. Same here.
There's a four-way wrangle between the proponents of conicals (Bill Woods, Jonathan Weiss), OS waveguide (Dr. Geddes), LeCleac'h, and the Altec and JBL traditionalists. I'm not going there - there's models, simulations, measurements, and subjective experiences to support each camp. The argument over horn profiles will probably continue forever.
I've liked the sound of the LeCleac'h horns I've heard here in Colorado, and contacted Martin Seddon in Australia about commissioning a special version optimized for the 288. The AH425 is designed from the latest LeCleac'h spreadsheet that uses the internal flare of the compression driver (8 degrees for the 288) as a starting point for the horn expansion.
The size (and LF cutoff) is limited by the largest size that would fit in an AusPost box - sounds stupid, I know, but the difference between AusPost and FedEx/UPS is the difference between US$90 shipping for two horns and US$600 shipping for two horns. Since a pair of AH425's are quite reasonably priced at about US$500~600 (depending on exchange rate), yes, that makes a difference. Just a little bigger has the practical effect of doubling the price. I'm OK with Martin or Bill Woods getting paid for the great work they do, but the idea of half the cost going to FedEx or UPS box-smashers is less appealing. (AusPost did a great job, by the way - they travelled all the way from Perth to Colorado and arrived in perfect condition. I wish all my Internet purchases arrived in such good shape.)
I use the feeble rationalization that Newell and Holland (page 108) recommend a horn no longer than 12 inches to minimize coloration. This is a pitiful ex-post-facto justification of the AusPost size limit, but I'm sticking with it.
Bjorn Kolbrek has kindly done extensive BEM modeling of the various size and T ratios that I was suggesting to Martin in the early phases of the project. We reached a consensus around a 425 Hz cutoff, a T ratio of 0.707, and the aforementioned internal 8-degree flare of the 288 compression driver. Bjorn's data shows flat acoustical impedance and group delay down to 550 Hz, so a 800-900 Hz crossover should be extremely conservative, considering the midband headroom of large-format drivers. The modeling also shows nothing like constant directivity, with beaming similar to 3" or so direct-radiator.
Once again, I take refuge in Newell and Holland, with a quote from Page 112 (emphasis in second paragraph added):
Ahem. I'm hardly working on the level of Dr. Holland, but I'm willing to borrow the discoveries of others if it suits my goals, which in this case was the smoothest possible acoustical impedance across the working range. The graph from Bjorn Kolbrek shows an intermediate stage of the AH425 design, comparing the acoustical impedance of two LeCleac'h versions - the darker lines are for a T = 0.707 (as used in the production version), and the thinner lines are for an alternative T = 1.34 (closer to a conical expansion). Both are for 425 Hz horns with the Altec 288 8-degree internal flare included.
The red line shows the percentage of acoustic energy reflected from the horn back into the compression driver, and the black line shows the percentage of acoustic energy that makes it from the compression driver into the outside world. This is akin to the SWR of an antenna - obviously, energy that is reflected from the antenna back into the transmitter doesn't do any good, and the same applies to the diaphragm of the compression driver.
The red line is especially significant at higher frequencies - even though the percentage of reflected energy is pretty small at 10% or less, that's 20 dB down - and energy that's reflected back to the diaphragm is likely to end up being re-reflected back into the horn again after bouncing off the diaphragm and rear chamber.
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