I'm sure I saw a thread about the subject on here at some point, but now I can't seem to find it.
So I was thinking, how about doing an open baffle with karlson wings in front of the driver, both to give a bit of loading and to extent the baffle without the extra real estate normally needed, but most importantly to use the lens effect of the wings to get better dispersion on the large drivers normally required to get good bass in OB?
I'm thinking a cab with normal sized sides, top and bottom and a slanted inner baffle, just like the normal karlson.
But with difference of having an inverted karlson slot on the back.
The wings could be adjusted in width/spacing to the Qts of the drives. IE more open with higher Qts drivers.
Any idea of how to adjust that parameter?
I'd think even very high Qts drivers could benefit from the wings. There would be only a bit of loading but the benefit of the lens effect and the "wider" baffle with the broadband resonant wings would be there.
I'm thinking of doing some experiments and play around when I get the a pair of the Monacor SPM units. It's going the be a little while though so in the meantime feel free to chip in with ideas and experiences.
Probably a very good candidate for foam core, eh X? ;-)
So I was thinking, how about doing an open baffle with karlson wings in front of the driver, both to give a bit of loading and to extent the baffle without the extra real estate normally needed, but most importantly to use the lens effect of the wings to get better dispersion on the large drivers normally required to get good bass in OB?
I'm thinking a cab with normal sized sides, top and bottom and a slanted inner baffle, just like the normal karlson.
But with difference of having an inverted karlson slot on the back.
The wings could be adjusted in width/spacing to the Qts of the drives. IE more open with higher Qts drivers.
Any idea of how to adjust that parameter?
I'd think even very high Qts drivers could benefit from the wings. There would be only a bit of loading but the benefit of the lens effect and the "wider" baffle with the broadband resonant wings would be there.
I'm thinking of doing some experiments and play around when I get the a pair of the Monacor SPM units. It's going the be a little while though so in the meantime feel free to chip in with ideas and experiences.
Probably a very good candidate for foam core, eh X? ;-)
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Let me get this straight. A box with a slanted driver open faced on the front and a Karlson aperture on the back for the rear wave? The purpose to provide some non-resonant loading of the driver and improve dispersion from back side. Not sure why you need improved dispersion on the back? It is the front wave that the K aperture lens gives the most impact. This could be modeled in AkAbak easily enough but to first order the effective CSA of the aperture could be used to model the loading on the back of a driver in Hornresp. It is like a slot loaded open baffle with the slot facing backwards.
No no. 🙂 Karlson slot both front and back.
Not much different from a regular karlson only instead of the backboard, an inverted karlson slot (inverted or noninverted doesn't really matter that much. Just the baffle would be acoustically larger this way).
Not much different from a regular karlson only instead of the backboard, an inverted karlson slot (inverted or noninverted doesn't really matter that much. Just the baffle would be acoustically larger this way).
I think it is a good idea. It would be essentially a variant of an H-baffle dipole speaker. The folded lens would make an effectively large baffle with a relatively small footprint. If it provides some loading like other karlson boxes do, excursion could be more controlled than with a conventional OB.
Generally I'd assume you'd want a slightly lower Qts driver for this than would be used for a smaller flat baffle, both because of the larger effective baffle size, and the additional front and rear mass loading.
Freddy made pretty much exactly what you described fairly recently in the cheap speakers contest.
Forsman of Norway has been making something similar with a tube to form the lens for years. Forsman
Snkby's similar DIY K-lens dipoles.
Photos
I've never made one, but if i did it would look like the below picture. This was sort of inspired by the front section of Magnetar's old 'Rosie' klam speaker.
Generally I'd assume you'd want a slightly lower Qts driver for this than would be used for a smaller flat baffle, both because of the larger effective baffle size, and the additional front and rear mass loading.
Freddy made pretty much exactly what you described fairly recently in the cheap speakers contest.
Forsman of Norway has been making something similar with a tube to form the lens for years. Forsman
Snkby's similar DIY K-lens dipoles.
Photos
I've never made one, but if i did it would look like the below picture. This was sort of inspired by the front section of Magnetar's old 'Rosie' klam speaker.
Alpha 15A is the usual suspect, but I'd favour Beta 15A off the bat for the above reasons.
If you apply the same impedance transforms (and phase shifts) front and back,
Its just another glorified ripole. Expect a large leakaround to kill the low end.
Don't expect that qualifies as "loading", except in the leaky un-usable range.
As for dispersion, you still have phase nuls at either side.
Apparently Snkby stuffed the back, so his transforms aren't exactly the same.
I think that step might be crucial to salvage a usable result from this madness.
Its just another glorified ripole. Expect a large leakaround to kill the low end.
Don't expect that qualifies as "loading", except in the leaky un-usable range.
As for dispersion, you still have phase nuls at either side.
Apparently Snkby stuffed the back, so his transforms aren't exactly the same.
I think that step might be crucial to salvage a usable result from this madness.
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Well yeah, of course it will still be a dipole, with figure 8 response. (side nulls) This is a feature of all open baffle designs. Sure, it would be a close relative of the ripole. I'd expect a bit more BW though, and it would be more suitable for full range drivers.
A simple constant width slot might suffice for most purposes, and it would be easier to sim.
I would not dismiss the additional loading out of hand, as there will be additional constrained air mass on both sides of the driver.
A simple constant width slot might suffice for most purposes, and it would be easier to sim.
I would not dismiss the additional loading out of hand, as there will be additional constrained air mass on both sides of the driver.
I'm not sure I get what you a saying. How is this that much different from a regular karlson or even a regular OB?
Anyway a very quick clarifying sketch on my iPad:
An externally hosted image should be here but it was not working when we last tested it.
I can't see your sketch. Dropbox might not allow hotlinks, not sure.
Here's the recent build I mentioned. Perhaps it's the one you saw.
http://www.diyaudio.com/forums/full-range/256437-quick-cheap-dirty-speaker-challenge-2.html
Here's the recent build I mentioned. Perhaps it's the one you saw.
http://www.diyaudio.com/forums/full-range/256437-quick-cheap-dirty-speaker-challenge-2.html
Oh I see. But I think the idea deserves a bit better materials than shredded crumpled old cardboard. And for some odd reason he punched holes in the baffle. That would surely kill the bass if not the other leaks in the box and the overall flimsiness of the construction.
Sorry about the picture, here it is:
https://drive.google.com/file/d/0B-BwNQN626aZc2gxN0d5WkRoSm8/edit?usp=sharing
Edit: Apparently you can't link to an image directly from googledrive but the link should work.
I'm afraid the super fast sketch has been oversold very much by now. ;-)
Sorry about the picture, here it is:
https://drive.google.com/file/d/0B-BwNQN626aZc2gxN0d5WkRoSm8/edit?usp=sharing
Edit: Apparently you can't link to an image directly from googledrive but the link should work.
I'm afraid the super fast sketch has been oversold very much by now. ;-)
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I was thinking of much the same thing. Basically a Karlson slot on the front, but a common U-baffle for the rear-wave. However the rear-wave will be damped, almost like a boffle, but not with so many felt-curtains. And the baffle will simply be flat, with a slanted Karlson-slot in front of the woofers.
Deon
Deon
The two-slot approach has the advantage of putting the backwave to better use.
You will have better dispersion control. The bass will be narrowed by side cancelation and the higher frequencies will get more dispersion because of the slot.
You won't lose as much of the backwaves HF content as with stuffing or boffle felt. Yet you still keep the quite high frequencies that are affected by the basket attenuated, with the inverted slot.
The double slot also reduces the overall depth of the cap to reach a given low frequency by quite a lot. What's more, the highly irregular and pointed nature of both half-cavities will reduce any cavity resonance to almost nothing. A square back box, if used fullrange, will have some colouration unless stuffed severely.
Ironically a slit or karlson shape lens pressed all the way up to the driver will have more audible cavity resonance, unless stuffed or made of felt to kill any back reflected HF content.
You will have better dispersion control. The bass will be narrowed by side cancelation and the higher frequencies will get more dispersion because of the slot.
You won't lose as much of the backwaves HF content as with stuffing or boffle felt. Yet you still keep the quite high frequencies that are affected by the basket attenuated, with the inverted slot.
The double slot also reduces the overall depth of the cap to reach a given low frequency by quite a lot. What's more, the highly irregular and pointed nature of both half-cavities will reduce any cavity resonance to almost nothing. A square back box, if used fullrange, will have some colouration unless stuffed severely.
Ironically a slit or karlson shape lens pressed all the way up to the driver will have more audible cavity resonance, unless stuffed or made of felt to kill any back reflected HF content.
Ripole by any other disguise does not "reach" a given low frequency.
Unless by reach, you mean "cancel all except the extreme nearfield".
Doesn't matter how well one couples to complete bass cancellation.
If you want to place your head inside, I suppose it would work...
There is no baffle smaller than an entire wall that can fix this.
The front and back bass transforms must not result in cancel phase,
try a 6th order bandpass stagger tuning, then schmear with Karlson.
Maybe you get something. Maybe...
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You seem to have general dislike towards both OB an K couplers, that has very little grounding in reality. Why don't you stop posting in this thread? You don't seem to contribute much in the way of real advice or ideas.
I build and like some K couplers, particularly K15.
If you K only the front or the back, or stagger the
tuning such that they are not equal phase shifted
and impedance transformed at lowest frequency.
I would be more encouraging.
Believing you can phase shift the front and back
equally and this is somehow better loading than
OB is a disconnect from reality. The problem is it
cannot couple to the room.
I have a dislike of open baffles that are outwardly
too small to work down to the frequency claimed by
fantasy "loading" techniques such as ripole. Big OB's
that can actually block most of the leak-around are
fine. Folding the wood inward isn't going to help much...
Plenty grounded in reality hands-on with Zobsky's
ill-fated attempts to build similar such schemes...
If you K only the front or the back, or stagger the
tuning such that they are not equal phase shifted
and impedance transformed at lowest frequency.
I would be more encouraging.
Believing you can phase shift the front and back
equally and this is somehow better loading than
OB is a disconnect from reality. The problem is it
cannot couple to the room.
I have a dislike of open baffles that are outwardly
too small to work down to the frequency claimed by
fantasy "loading" techniques such as ripole. Big OB's
that can actually block most of the leak-around are
fine. Folding the wood inward isn't going to help much...
Plenty grounded in reality hands-on with Zobsky's
ill-fated attempts to build similar such schemes...
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OB are fine if people understand how they work. Sure, there is plenty of "fantasy" out there, but let's ignore that for now.
A big baffle OB will work pretty well with any mid Q driver with reasonable excursion and otherwise appropriate specs.
A small OB will work fine with a high Q driver, as long as deep extension isn't required. The resonance fills in the roll off.
A small OB will also work fine with a mid Q pro driver if it is understood that there will be a phase cancellation induced rolloff, and an inverse curve low pass filter is applied to counteract it. This is quite feasible if there is sufficient excursion available.
It's the last case that might be the most interesting with a double K slotted OB. As it is known that regular Karlsons control excursion well below their gain BW, it is reasonable to suspect that similar excursion control might occur in a double sided "K-baffle" as well. If so, a Linkwitz transform could be applied even with a moderate excursion pro driver.
A big baffle OB will work pretty well with any mid Q driver with reasonable excursion and otherwise appropriate specs.
A small OB will work fine with a high Q driver, as long as deep extension isn't required. The resonance fills in the roll off.
A small OB will also work fine with a mid Q pro driver if it is understood that there will be a phase cancellation induced rolloff, and an inverse curve low pass filter is applied to counteract it. This is quite feasible if there is sufficient excursion available.
It's the last case that might be the most interesting with a double K slotted OB. As it is known that regular Karlsons control excursion well below their gain BW, it is reasonable to suspect that similar excursion control might occur in a double sided "K-baffle" as well. If so, a Linkwitz transform could be applied even with a moderate excursion pro driver.
Could you give me a link to sit Zobsky's ill-fated attempts? I would be very interested to see that.
Folding the baffle is an old and proven method. It does produce a certain amount of cavity sound however, depending on the depth. That's is where the karlson wings come in. They form a multi resonant chamber so you avoid the box sound.
Different tuning for the front and the back is a given, due to the inverted karlson slot and the different hollows of the divider.
Inverted Karlson on back sounds plausible for stagger tuning.
Certainly a difference acoustic impedance, floor vs open air.
If that's the nature of your plan, might be worth experiment.
As for Zobsky's Ripole, broke and burned it, I think. He might
have been joking about burning it, I'm not sure. I am sure he
built at least two versions and tried to salve the last with a
giant baffle that took up half the room. But there was just
no helping it. Maybe he still has pictures?
Certainly a difference acoustic impedance, floor vs open air.
If that's the nature of your plan, might be worth experiment.
As for Zobsky's Ripole, broke and burned it, I think. He might
have been joking about burning it, I'm not sure. I am sure he
built at least two versions and tried to salve the last with a
giant baffle that took up half the room. But there was just
no helping it. Maybe he still has pictures?
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K15 controls excursion very well with a low Q driver of 15" or less.
K12 too, but not so much. I believe the internal chambers of K15
are very significant and perhaps critical to achieve that effect.
Not sure if its reasonable to attribute that entire effect to the
loading of the wings, as that's all a bipolar Klam would feel....
Closest thing to an OB Klam I played with was a 10" Electrovoice,
open on back, with an 8ft Sono-K-Tube on the front. No baffle.
Strangely, it sounded best with a 1/4 inch gap between the front
seal and the K-Tube, but no bass coupling or control to speak of.
Properly mated to tube, there might or not have been control. I
can only remember that dispersion pattern wasn't as I expected
and it didn't sound natural.
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