Hi,
I sim with the same Akabak script Axel uses for himself.
The script has proven to correlate well with real life.
Iirc Axel as well as Mr. Linkwitz use the term folded open Baffle for their constructs.
Efficiency is certainly reduced by acoustic phase cancellation, but used as a singular numeral, without taking the circumstances into the relation doesn't show reallife behaviour.
One should at least state under which conditions the claim may apply, otherwise it's just spilling hot air. 🙄
If You compare the small folded dipoles, it'd be sensible to compare to other principles when built into similarly small sized cabinets and similar amplitude response.
Just to give You an idea: The dimensions of Axel's BMC400 Attac woofer was smaller than the two shipping cartons of the raw drivers.
Apart from the fact that some principles -think of a horn- in such small cabinets would be a ridicule, most other principles required considerably smaller drivers and/or so much electronic equalization to reach a similarly low lower bandwidth limit, that efficiency figures would be comparably and awful.
If ones sizes a ripole up to the same cabinet volume of say a BR instead, the dipole could make use of much more membrane area, typically 3-4 times.
Also real room conditions must be taken into account, as the dipoles loose quite a bit on their dipolar character placed in proximity to a reflecting wall.
All this put together and it shows that the dipoles aren't at all 'awfully' inefficient, but can compare quite well with other principles.
Where the folded dipole is indeed 'inferior' is not efficiency, but effort.
More membrane area means multiple drivers or larger drivers and associated higher building complexity.
jauu
Valvin
I sim with the same Akabak script Axel uses for himself.
The script has proven to correlate well with real life.
Iirc Axel as well as Mr. Linkwitz use the term folded open Baffle for their constructs.
One could also say something like: " The weather is awful". 😛
Efficiency is certainly reduced by acoustic phase cancellation, but used as a singular numeral, without taking the circumstances into the relation doesn't show reallife behaviour.
One should at least state under which conditions the claim may apply, otherwise it's just spilling hot air. 🙄
If You compare the small folded dipoles, it'd be sensible to compare to other principles when built into similarly small sized cabinets and similar amplitude response.
Just to give You an idea: The dimensions of Axel's BMC400 Attac woofer was smaller than the two shipping cartons of the raw drivers.
Apart from the fact that some principles -think of a horn- in such small cabinets would be a ridicule, most other principles required considerably smaller drivers and/or so much electronic equalization to reach a similarly low lower bandwidth limit, that efficiency figures would be comparably and awful.
If ones sizes a ripole up to the same cabinet volume of say a BR instead, the dipole could make use of much more membrane area, typically 3-4 times.
Also real room conditions must be taken into account, as the dipoles loose quite a bit on their dipolar character placed in proximity to a reflecting wall.
All this put together and it shows that the dipoles aren't at all 'awfully' inefficient, but can compare quite well with other principles.
Where the folded dipole is indeed 'inferior' is not efficiency, but effort.
More membrane area means multiple drivers or larger drivers and associated higher building complexity.
jauu
Valvin
Lets talk Ripole awful for a sec...
Bass is there if you stick your head or microphone into the vent.
Little further away on-axis, if you are lucky: Bass might drown
out the port noise. Off axis, port noise (which disperses well to
the sides from the slot) is hearable over the bass (with a deeply
notched figure 8 pattern due to cancellation).
What else is awful: Unloaded drivers flopping beyond linear XMAX.
We can pretend 2nd order cancellation of push pull, but 3rd order
due to excessive excursion gets you. And maybe some of those
harmonics contribute to the port noises I noticed. As the noise I
heard off-axis didn't sound quite like whooshing or wheezing.
Ports are plenty big enough that sort of thing shouldn't happen.
But slot loading! Well, the change of acoustic impedance in the
slot is not really loading into a space with an equal and opposite
suck-out nearby. Might as well put a dead weight of putty on the
cone and call it "loading". If a cone flops uselessly, its not loaded.
Compare Ripole to an ELF sealed box operating below Fs:
-6db per octave vs -12dB per octave equalizations required.
On-axis, sealed box below resonance requires more power.
Off-axis, sealed box could win vs Ripole's figure 8 pattern.
Yet even Ripole's winningest scenario, on-axis: Runs out of
linear XMAX way before the sealed box or any reasonable
amount of equalized power.
I have nothing against open baffles. Add a baffle to Ripole
totally fixes it, if you have space for that sort of thing...
Or load Ripole's back with a corner or wall to make the
impedance and phase shifts dissimilar, you might hear
or feel something. Perhaps horizontally behind the couch,
so near field of the port is directly behind your head, and
the back dissimilarly loaded by the floor.
It seems silly to purposely put yourself into a situation
where positional loading compromises are even necessary.
Ripole compares well with other snake oil and hearsay.
Build you one, I really think you should, everyone should.
If you have any doubts at all, wasted effort will remove them.
I don't mind if you dislike me today for writing the truth.
Only trying to save you some time and money.
Been there, done that...
Bass is there if you stick your head or microphone into the vent.
Little further away on-axis, if you are lucky: Bass might drown
out the port noise. Off axis, port noise (which disperses well to
the sides from the slot) is hearable over the bass (with a deeply
notched figure 8 pattern due to cancellation).
What else is awful: Unloaded drivers flopping beyond linear XMAX.
We can pretend 2nd order cancellation of push pull, but 3rd order
due to excessive excursion gets you. And maybe some of those
harmonics contribute to the port noises I noticed. As the noise I
heard off-axis didn't sound quite like whooshing or wheezing.
Ports are plenty big enough that sort of thing shouldn't happen.
But slot loading! Well, the change of acoustic impedance in the
slot is not really loading into a space with an equal and opposite
suck-out nearby. Might as well put a dead weight of putty on the
cone and call it "loading". If a cone flops uselessly, its not loaded.
Compare Ripole to an ELF sealed box operating below Fs:
-6db per octave vs -12dB per octave equalizations required.
On-axis, sealed box below resonance requires more power.
Off-axis, sealed box could win vs Ripole's figure 8 pattern.
Yet even Ripole's winningest scenario, on-axis: Runs out of
linear XMAX way before the sealed box or any reasonable
amount of equalized power.
I have nothing against open baffles. Add a baffle to Ripole
totally fixes it, if you have space for that sort of thing...
Or load Ripole's back with a corner or wall to make the
impedance and phase shifts dissimilar, you might hear
or feel something. Perhaps horizontally behind the couch,
so near field of the port is directly behind your head, and
the back dissimilarly loaded by the floor.
It seems silly to purposely put yourself into a situation
where positional loading compromises are even necessary.
Ripole compares well with other snake oil and hearsay.
Build you one, I really think you should, everyone should.
If you have any doubts at all, wasted effort will remove them.
I don't mind if you dislike me today for writing the truth.
Only trying to save you some time and money.
Been there, done that...
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Hi kenpeter,
the experience I have had and am having completely contradicts your last post. I'm listening to "Marcus Miller" Live and More, which contains a lot of very deep bass from both drums and bass guitar and from my listening position which is 3.5 meters away from my Ripoles the bass is very deep, clear, plenty load enough with just a few watts and very enjoyable to listen too. Better in quality than my Linn Isobarik's They do not pressurise the room like a large sealed sub but then they have zero boxiness, no port noise or any other artefacts of more conventional loading. This is not some " I made them, so they must be good" effect. They are very, very good considering the cost, the size and the complexity compared to my Linns.
It's a problem with this type of evaluation of a speaker when you have two diametrically opposing subjective viewpoints; who do you believe?
the experience I have had and am having completely contradicts your last post. I'm listening to "Marcus Miller" Live and More, which contains a lot of very deep bass from both drums and bass guitar and from my listening position which is 3.5 meters away from my Ripoles the bass is very deep, clear, plenty load enough with just a few watts and very enjoyable to listen too. Better in quality than my Linn Isobarik's They do not pressurise the room like a large sealed sub but then they have zero boxiness, no port noise or any other artefacts of more conventional loading. This is not some " I made them, so they must be good" effect. They are very, very good considering the cost, the size and the complexity compared to my Linns.
It's a problem with this type of evaluation of a speaker when you have two diametrically opposing subjective viewpoints; who do you believe?
I have to believe what I have personally auditioned just as you do.
This guy needs to visit someone local who's been down this road
and listen for himself. Subjective mileage and tall tales may vary...
This guy needs to visit someone local who's been down this road
and listen for himself. Subjective mileage and tall tales may vary...
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Since he's set on it, I think he needs to build one and report back. It's a pretty easy and inexpensive build. The point of contention, as you've noted, is "performance" compared to the same driver in another alignment .
FWIW, I have a pair of scavenged 15" realistic mach one drivers ( http://www.parts-express.com/replacement-woofer-for-15-realistic-mach-one-8-ohm--290-184 ). If I can find some cheap scrap wood, I'll try and rig up something comparing a ripole to a SLOB, with measurements
FYI, To the original author, this might be helpful
http://www.hifizine.com/2012/12/subwoofer-origami/
http://lautsprechershop.de/pdf/ripol/ridtahler.pdf
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Port noise with a Ripole? Sounds like someone's poor experience has something to do with poor build quality.
I've built a few Ripoles and never had an issue with port noise, only running out of steam a bit early.
I've built a few Ripoles and never had an issue with port noise, only running out of steam a bit early.
Definitely not build quality.
It's been a while but I think the noise he mentioned might have been originating from the vented pole piece with the driver stressed near xmax
I'm going to give this design one more shot
1. The first ripples I built were with a pair of 15" pro drivers - Pyle ppa15 , Qts of 0.7 but low xmax
2. The 2nd was with a single adire shiva 12, plenty of excursion and borderline low qts of about .4
3. Last year, I built a pair of SLOB array with 4 12" drivers which worked well, part from being too big
4. We'll see what happens with these realistic drivers , highish q and moderate excursion. I found a 4x8 piece of blemished particleboard at the hardware store for very cheap so I'll makw some sawdust this weekend and report back
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I got a spare SigmaPro18-A2 you could play with.
If not, I'd like to slap it into a 6th order alignment
with a Paraline fold for the front slot. If it'll play at
least 40 to 400 with full dispersion (and I'm not
yet saying it actually can or will), I'd have use for
that range...
A dipole with slots front and back, stagger tuned
to avoid the problem of summing to cancellation.
---
If we go the ripole route, you know how much beer
this doomed experiment in repeat tomfoolery is
going to cost you??? My price goes up every time...
I've only heard two of your ripole disasters. Had no
idea there had been a third. Now #4. What was the
definition of insanity again???
If not, I'd like to slap it into a 6th order alignment
with a Paraline fold for the front slot. If it'll play at
least 40 to 400 with full dispersion (and I'm not
yet saying it actually can or will), I'd have use for
that range...
A dipole with slots front and back, stagger tuned
to avoid the problem of summing to cancellation.
---
If we go the ripole route, you know how much beer
this doomed experiment in repeat tomfoolery is
going to cost you??? My price goes up every time...
I've only heard two of your ripole disasters. Had no
idea there had been a third. Now #4. What was the
definition of insanity again???
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Hi,
of those who heard a proper designed ripole or the originals no one would say it doesn't work.
There may be some who's listening experience dislikes the 'non-pressured' sound and there may be room situations where a dipole would generally be not prime choice, yes.
But especially classic and natural instrument listeners like the uncoloured, precise and 'fast' sound of the Ripole.
When Ken mentioned flapping diaphragms my assumption became assurance.
Chances are high that he has not listened to a proper designed Ripole yet.
I've been asked many times by guys who wanted to try out the principle in a way like: "I got some drivers lying around. Can I....."
Typically the drivers were not optimal, indeed most were rather unuseable for this application.
People regularly build small folded OBs without following the advices for proper ripoling, be it wrong driver choice, unfortunate choice of dimensions, omittance of the passive EQ-network, etc.
Some succeed still though and some fail.
Those who fail then often rage about low performance.
Instead they should rather worry about their low spirit.
In short... follow the proper guidelines, choose appropriate drivers and number of drivers, add the fitting passive network and then -and only then- You have a decent basis for evaluation of the principle.
jauu
Calvin
of those who heard a proper designed ripole or the originals no one would say it doesn't work.
There may be some who's listening experience dislikes the 'non-pressured' sound and there may be room situations where a dipole would generally be not prime choice, yes.
But especially classic and natural instrument listeners like the uncoloured, precise and 'fast' sound of the Ripole.
When Ken mentioned flapping diaphragms my assumption became assurance.
Chances are high that he has not listened to a proper designed Ripole yet.
I've been asked many times by guys who wanted to try out the principle in a way like: "I got some drivers lying around. Can I....."
Typically the drivers were not optimal, indeed most were rather unuseable for this application.
People regularly build small folded OBs without following the advices for proper ripoling, be it wrong driver choice, unfortunate choice of dimensions, omittance of the passive EQ-network, etc.
Some succeed still though and some fail.
Those who fail then often rage about low performance.
Instead they should rather worry about their low spirit.
In short... follow the proper guidelines, choose appropriate drivers and number of drivers, add the fitting passive network and then -and only then- You have a decent basis for evaluation of the principle.
jauu
Calvin
I've been thinking about learning AkaBak for a while, and I guess this is a good opportunity to get started. 🙂
I would be very interested in simulating how these drivers perform in a ripole vs a W-frame (and H-frame for that matter). Calvin, are you able to share the ripole script? And if anyone has a W-frame script I can use as a starting point that would be fantastic too (or maybe the ripole script could be used as a starting point seeing as the geometry is similar?) If not, I'll just give it a go and put the script up here for feedback. 🙂
I would be very interested in simulating how these drivers perform in a ripole vs a W-frame (and H-frame for that matter). Calvin, are you able to share the ripole script? And if anyone has a W-frame script I can use as a starting point that would be fantastic too (or maybe the ripole script could be used as a starting point seeing as the geometry is similar?) If not, I'll just give it a go and put the script up here for feedback. 🙂
Hi,
I was given the skript by Axel himself under the premise not to share it wo. his permission.
The behaviour of big W-Frames after Linkwitz and H-Frames is quite similar.
The small W-frames after Ridtahler differ more, due to their greater amount of Fs reduction and typical driver parameters.
Linkwitz makes use of low Fs, low Qts drivers, while Ridtahler suggests drivers with higher Fs and Qts.
Besides smaller build, I like that the drivers in a Ridtahler require less -and under certain conditions even no- bass boost.
A driver with a elevated Qts, closer to the 0.5-0.7 range imho behaves better as is than a ´pushed´ low Qts driver.
There are many modern PA-drivers in the 15" and 18" class that feature a fitting set of Fs and Qts (my rule of thumb 0.35 and 35Hz), long stroke capability and the right type of progressive suspension.
Those allow for Fs reduction of up to 15Hz(!), require only modest wattage and can still be pushed hard without flapping around.
jauu
Calvin
I was given the skript by Axel himself under the premise not to share it wo. his permission.
The behaviour of big W-Frames after Linkwitz and H-Frames is quite similar.
The small W-frames after Ridtahler differ more, due to their greater amount of Fs reduction and typical driver parameters.
Linkwitz makes use of low Fs, low Qts drivers, while Ridtahler suggests drivers with higher Fs and Qts.
Besides smaller build, I like that the drivers in a Ridtahler require less -and under certain conditions even no- bass boost.
A driver with a elevated Qts, closer to the 0.5-0.7 range imho behaves better as is than a ´pushed´ low Qts driver.
There are many modern PA-drivers in the 15" and 18" class that feature a fitting set of Fs and Qts (my rule of thumb 0.35 and 35Hz), long stroke capability and the right type of progressive suspension.
Those allow for Fs reduction of up to 15Hz(!), require only modest wattage and can still be pushed hard without flapping around.
jauu
Calvin
Ok, no problem. 🙂
I gave AkaBak a go, a W-frame to start with. Any feedback is appreciated, am I on the right track here? Here's the script as well as SPL and Excursion graphs:
Code:
System 'W18'
Def_Driver 'K1'
dD=39cm |Piston
fs=27.59Hz Mms=196g Qms=4.537
Qes=0.585 Re=6.65ohm Le=1.07mH ExpoLe=0.618
Def_Driver 'K2'
dD=39cm |Piston
fs=27.59Hz Mms=196g Qms=4.537
Qes=0.585 Re=6.65ohm Le=1.07mH ExpoLe=0.618
Driver 'D1' Def='K1' Node=0=1=2=3
Driver 'D2' Def='K2' Node=1=0=4=2
Duct 'Top' Node=3=10
WD=8.9cm HD=48cm Len=48.6cm
Radiator 'TopRear' Def='Top' Node=10
x=0 y=0 z=0 HAngle=180 VAngle=0
Duct 'Mid' Node=2=11
WD=17.3cm HD=48cm Len=48.6cm
Radiator 'MidFront' Def='Mid' Node=11
x=0 y=0 z=0 HAngle=0 VAngle=0
Duct 'Bottom' Node=4=12
WD=14.2cm HD=48cm Len=48.6cm
Radiator 'BottomRear' Def='Bottom' Node=12
x=0 y=0 z=0 HAngle=180 VAngle=0
If memory serves, there were 6 loudspeakers in the last attempt.
Each was low efficiency, big overhang, Qts .6ishy, probably of car
subwoofer origin. Zob might still have the WT3 measurements,
could differ from my recollections.
Problem is that all six were cycling way too far without doing
anything useful, but moving a small quantity of near-field air
in a close loop with no sensible coupling to the rest of the room.
Bass was neither hearable of feelable. Thus we kept turning up
the amp and eq till mechanical limits added irrelevant sounds.
Barely any more efficient than speaker with no baffle whatsoever
and a lump of putty to weigh down Fs without any real loading.
Plus boxiness due to Ripole port interiors obviously being boxes.
It is what it is, and doesn't take a lot of Watts to make it flap to
the point of audible distress while still not making useful bass.
If you throw enough speakers with enough xmax at the problem,
and sit directly on axis, you can pretend that this technique works.
There was nothing wrong with Zob's construction or choice of driver
except that 6 twelve inch subs could not sweep near enough volume
to overcome the poor coupling of this design. Disturbing neighbors
won't be a problem, filling the living room with another large and
largely useless construction project will be.
I'm willing to help Zob make sawdust, but this time there needs to
be a plan B. So that after we measure and laugh at our foolishness
for being suckered into this stupidity again, we can salvage the work
toward something that cooperates with the laws of reality.
Eq was mini-DSP, and amp was a solid state McIntosh (mc2700?).
Each was low efficiency, big overhang, Qts .6ishy, probably of car
subwoofer origin. Zob might still have the WT3 measurements,
could differ from my recollections.
Problem is that all six were cycling way too far without doing
anything useful, but moving a small quantity of near-field air
in a close loop with no sensible coupling to the rest of the room.
Bass was neither hearable of feelable. Thus we kept turning up
the amp and eq till mechanical limits added irrelevant sounds.
Barely any more efficient than speaker with no baffle whatsoever
and a lump of putty to weigh down Fs without any real loading.
Plus boxiness due to Ripole port interiors obviously being boxes.
It is what it is, and doesn't take a lot of Watts to make it flap to
the point of audible distress while still not making useful bass.
If you throw enough speakers with enough xmax at the problem,
and sit directly on axis, you can pretend that this technique works.
There was nothing wrong with Zob's construction or choice of driver
except that 6 twelve inch subs could not sweep near enough volume
to overcome the poor coupling of this design. Disturbing neighbors
won't be a problem, filling the living room with another large and
largely useless construction project will be.
I'm willing to help Zob make sawdust, but this time there needs to
be a plan B. So that after we measure and laugh at our foolishness
for being suckered into this stupidity again, we can salvage the work
toward something that cooperates with the laws of reality.
Eq was mini-DSP, and amp was a solid state McIntosh (mc2700?).
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Sorry, MC2100. Couldn't quite pull the memory from my fog.
And to be clear, no actual putty was used. Just saying that
in the example I experienced that day: Circulating port and
nearfield air masses acted to little more farfield effect than
a similar dead weight. Fs was reduced, but not in a way that
presented a loading advantage...
And to be clear, no actual putty was used. Just saying that
in the example I experienced that day: Circulating port and
nearfield air masses acted to little more farfield effect than
a similar dead weight. Fs was reduced, but not in a way that
presented a loading advantage...
Last edited:
Particleboard has been sacrificed at the alter of "r-insanity" and a ripole has been produced.
A free air test with my 15" woofers resulted in too much motor noise and not much to show for it. I have some 8 ohm 12" subwoofers that fared much better in this test and also have a q of .5xx and an Fs on the mid to higher 20 Hz so I decided to build for them instead. Somewhat similar to the jazzman ripole mentioned earlier to this thread . 15" square with about 3" high x 13.5" wide rear openings (2). Since I don't expect my zalytron 1201pl woofers to have more than 5mm xmax, I chose a front chamber opening between 1/3 to 1/4 of (Sd x 2), fortituously ending up with 3" x 13.5"too.
Here is the contraption, untrimmed and pending test.
A free air test with my 15" woofers resulted in too much motor noise and not much to show for it. I have some 8 ohm 12" subwoofers that fared much better in this test and also have a q of .5xx and an Fs on the mid to higher 20 Hz so I decided to build for them instead. Somewhat similar to the jazzman ripole mentioned earlier to this thread . 15" square with about 3" high x 13.5" wide rear openings (2). Since I don't expect my zalytron 1201pl woofers to have more than 5mm xmax, I chose a front chamber opening between 1/3 to 1/4 of (Sd x 2), fortituously ending up with 3" x 13.5"too.
Here is the contraption, untrimmed and pending test.
Attachments
Hi,
linaudio, the script contains 3 different Wd values.
Based on the 48x13cm port size for all three ports, the TSPs You gave and the sim data I gave earlier here are the diagrams:
Rem: Data for electrically parallel connected drivers
Pic1) amplitude plot at 2.83V @1m, wo filter (black) and with suggested filter (blue)
Pic2) Impedance plot wo (black) and with filter (blue)
Pic3) Membrane axcursion over frequency w. filter @2,83V (black) and 20V (blue)
Pic4) schematic of filter ciruit.
Pic5) amplitude response plots for 2.83V@1m w. filter(black) and 20V @1m w. filter (blue)
jauu
Calvin
notice the general similarity of the curves of the sim and Face´s measurement.
So much about a thing that doesn´t work, yeah 😉
linaudio, the script contains 3 different Wd values.
Based on the 48x13cm port size for all three ports, the TSPs You gave and the sim data I gave earlier here are the diagrams:
Rem: Data for electrically parallel connected drivers
Pic1) amplitude plot at 2.83V @1m, wo filter (black) and with suggested filter (blue)
Pic2) Impedance plot wo (black) and with filter (blue)
Pic3) Membrane axcursion over frequency w. filter @2,83V (black) and 20V (blue)
Pic4) schematic of filter ciruit.
Pic5) amplitude response plots for 2.83V@1m w. filter(black) and 20V @1m w. filter (blue)
jauu
Calvin
notice the general similarity of the curves of the sim and Face´s measurement.
So much about a thing that doesn´t work, yeah 😉
Attachments
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Yes, my script was an attempt at a W-frame, not a ripole. Basically Linkwitz' original W-frame scaled up to fit the 18" drivers (but I have eperimented a bit more, and I don't think my attempt was quite right...).
However, looking at your plots (thanks!) I'm tempted to just go ahead and build the ripole, it looks really promising in my eyes. I might try, with a bit of careful planning, to cut the parts so that I can try out both W-frame and ripole, I'm curious to compare both listening impressions and measurements. Thanks again! 🙂
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