| zobsky |
What's the difference between the linkwitz W dipole and the dual driver ripole (apart from driver orientation)?
Thanks
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| chops |
Isn't the ripole somewhat smaller and doesn't it in some way lower the Fs of the driver due to the way it loads the driver?
AFAIK, a dipole doesn't do anything to the Fs and doesn't really load the driver at all. |
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| Rudolf |
The Linkwitz W dipole tries to cancel non-harmonic distortions by running the drivers push-pull. But the construction leads to front and rear air volumes that are very different for both drivers. So symmetry in frequency response is questionable.
The ripole favoures driver symmetry. Usually ripoles load the drivers by minimizing the front cavity. This leads to a lowered fs and transfers the onset of the dipole roll off to lower frequencies too.
In some way the ripole approaches a dipole made of two very short transmission lines while the Linkwitz W is more like a folded OB. |
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| zobsky |
i agree re. the smaller dimensions loading a ripole. I just hadn't ever seen a dual driver ripole before .Before seeing this diagram, I'd always thought a ripole had to be a N-profile, and in order to use multiple drivers in a ripole, each driver would need it's OWN N-profile enclosure.
Chops, off topic, ..doyou still use your U-baffle subs and did you ever try your drivers in a W-profile or ripole enclosure?
Secondly,(Dipole noob alert :att'n: ) can't a W-profile sub work with the driver cones facing each other? Why are the drivers always mounted looking in the same direction ?
Thanks |
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| theAnonymous1 |
| quote: | Originally posted by zobsky
Secondly,(Dipole noob alert :att'n: ) can't a W-profile sub work with the driver cones facing each other? Why are the drivers always mounted looking in the same direction ?
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| quote: | Originally posted by Rudolf
The Linkwitz W dipole tries to cancel non-harmonic distortions by running the drivers push-pull. But the construction leads to front and rear air volumes that are very different for both drivers. So symmetry in frequency response is questionable.
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| y8s |
| quote: | Originally posted by zobsky
i agree re. the smaller dimensions loading a ripole. I just hadn't ever seen a dual driver ripole before .Before seeing this diagram, I'd always thought a ripole had to be a N-profile, and in order to use multiple drivers in a ripole, each driver would need it's OWN N-profile enclosure. |
I think the behavior of the mirrored ripoles would be unchanged with or without a central wall. each driver would see the same pressure wave as it would have with a wall there or not. either it's produced by a second driver (in phase of course) or a reflection of its own output.
so who has done testing on the response of a Linkwitz spooning woofer W compared to a ripole facing woofer W? And how do you design the "lowered Fs" portion of the latter to gain extension?
Matt |
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| zobsky |
| quote: | Originally posted by y8s
so who has done testing on the response of a Linkwitz spooning woofer W compared to a ripole facing woofer W? And how do you design the "lowered Fs" portion of the latter to gain extension?
Matt |
Potentially my investigation for next month, IF I can find 4 acceptable woofers less than $35 shipped. I'd like to get down to an honest 30Hz wiithout excessively loose flabby bass but don't want to resort to low Q drivers + Eq.
Would these work ?
http://www.partsexpress.com/pe/show...tnumber=290-346 |
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| theAnonymous1 |
If you can swing a bit more :$:, these would be a better choice....
http://www.partsexpress.com/pe/psho...FTOKEN=59432710
I have 4 of them waiting to be put in ripoles. I have no way to cut the wood though, so it won't happen anytime soon (it's been over a year so far). |
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| zobsky |
| quote: | Originally posted by theAnonymous1
If you can swing a bit more :$:, these would be a better choice....
http://www.partsexpress.com/pe/psho...FTOKEN=59432710
I have 4 of them waiting to be put in ripoles. I have no way to cut the wood though, so it won't happen anytime soon (it's been over a year so far). |
Okay, .. I picked up 4 of those drivers for ripole (or more likely w baffle use). I'm hoping that the Qts of 0.7 will give me some bass without having to resort to EQ. Let's see what happens next month when the sawdust flies.
I'll be eating out of a can of beans for the rest of this month :) |
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| johninCR |
| With 4 drivers you can easily get the ripole symmetry in a W layout, so you get the ripole benefits along with vibration cancellation and push/pull distortion reduction all in one, not to mention about the smallest cab possible. HINT, the thicker the driver mounting panels the narrower your cab can be....It's kinda counter intuitive, but true as long as you mount the drivers normally in relation to the holes. Also, plan your build to be bolted together, so you can always get to your drivers to remove or change them without destroying the cab. |
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| theAnonymous1 |
| With these drivers there is a small amount of pole piece "chuff" at high excursions. I eliminated this problem by cutting off the dustcaps. If removing the dustcaps is too extreme for you, I suggest at least removing the pole piece screen. |
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| chops |
| quote: | Originally posted by zobsky
Chops, off topic, ..doyou still use your U-baffle subs and did you ever try your drivers in a W-profile or ripole enclosure?
Secondly,(Dipole noob alert :att'n: ) can't a W-profile sub work with the driver cones facing each other? Why are the drivers always mounted looking in the same direction ?
Thanks |
H-baffles actually, and the answer is no unfortunately. They were great, excellent even while they lasted. They were just simply way too large for my room. I wasn't able to postion my main channels where they needed to be for proper imaging and soundstaging.
And no, I never tried them in a W-baffle or ripole. However, once I get the chance (since I still have the drivers), I do plan on building these ripoles. Getting a lower Fs from this design sounds very interesting, and it will be needed since the baffles will be much much smaller than the H-baffles I had.
And it looks like theAnonymous1 answered your last question. ;)
| quote: | Originally posted by theAnonymous1
If you can swing a bit more :$:, these would be a better choice....
http://www.partsexpress.com/pe/psho...FTOKEN=59432710
I have 4 of them waiting to be put in ripoles. I have no way to cut the wood though, so it won't happen anytime soon (it's been over a year so far). |
I agree 100% on this. Eventhough the Goldwood's have a higher Qts, they also have a slightly higher Fs. The higher Qts will allow the bass to possibly be a little floppy, and the higher Fs may not allow them to reach as deep.
The Pyle PPA15 on the other hand has a perfect Qts for dipole/ripole use (0.6 min) which means it's bass will be tighter and cleaner which I can definately vouch for, and the lower Fs of 27Hz will get you lower. Not to mention that in a ripole, that Fs will get even lower (not sure how much lower however) giving you even lower bass reproduction. |
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| zobsky |
| quote: | Originally posted by johninCR
HINT, the thicker the driver mounting panels the narrower your cab can be....It's kinda counter intuitive, but true as long as you mount the drivers normally in relation to the holes. |
John, could you elaborate? I lost you on that. BTW, ..thanks for all the useful info on my last open baffle array build.
| quote: | Originally posted by chops
And no, I never tried them in a W-baffle or ripole. However, once I get the chance (since I still have the drivers), I do plan on building these ripoles. Getting a lower Fs from this design sounds very interesting, and it will be needed since the baffles will be much much smaller than the H-baffles I had.
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Chops, ... I read through your thread. Do these drivers need EQ'ing up on the low end (possibly by the bass boost on a sub amp) ?
Thanks |
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| Daveis |
What's the math for sizing the dual driver ripole?
Do you have to compensate for OB type cancellation with EQ? |
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| johninCR |
| quote: | Originally posted by zobsky
John, could you elaborate? I lost you on that. BTW, ..thanks for all the useful info on my last open baffle array build.
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For a 4 driver Ripole in a W alignment the single pathway will be twice the width of the 2 pathways to the rear. You'll still want the cone to magnet mounting like the Linkwitz W to be able to get the pathways small enough for ripole behavior, in fact as small as possible taking into account cone travel (so it can't hit the other driver's magnet).
This give you 2 driver mounting plates with 2 drivers on each, facing opposite directions. With a very thin piece of wood, the magnets would each stick out almost the full depth of the driver. If the wood was as thick as the driver is deep, then the frame of the driver would be even with the back of the magnet of the other driver. Viewed from the side the structure would be almost twice as thick using the thinner mounting plate.
Essentially, thick mounting plates enable a narrower pathway, which is important for Ripole behavior. Since you're already getting the left and right sides as close together as the drivers permit, narrowing the pathway results in a narrower cab.
This is something I didn't appreciate until I started assembly. I used relatively thin wood and each cab with four 12" drivers was 12" wide by 24" tall. I could have easily knocked 2" off of the width by making those mounting plates each 1" thicker. That would have reduced my central pathway to 3" instead of 4" and the 2 rear pathways 1.5" each instead of 2".
Note that I added 8" with cross bracing to the rear of mine, which adds 16" of rear wave travel distance and some U baffle behavior. This increases extension by more than a full octave or over +6db at the bottom with only a small increase in overall size. Also note that my W/U/Ripole/push-pull/mechanical cancellation subs do require damping in the rear pathway for proper operation. Too bad I went to the trouble using cheapie woofers I already had. At some point I plan to build something similar using eight 6x9's per side, resulting in stable high bass output OB speaker stands in a very compact form. |
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| zobsky |
| quote: | Originally posted by johninCR
For a 4 driver Ripole in a W alignment the single pathway will be twice the width of the 2 pathways to the rear. You'll still want the cone to magnet mounting like the Linkwitz W to be able to get the pathways small enough for ripole behavior, in fact as small as possible taking into account cone travel (so it can't hit the other driver's magnet).
This give you 2 driver mounting plates with 2 drivers on each, facing opposite directions. With a very thin piece of wood, the magnets would each stick out almost the full depth of the driver. If the wood was as thick as the driver is deep, then the frame of the driver would be even with the back of the magnet of the other driver. Viewed from the side the structure would be almost twice as thick using the thinner mounting plate.
Essentially, thick mounting plates enable a narrower pathway, which is important for Ripole behavior. Since you're already getting the left and right sides as close together as the drivers permit, narrowing the pathway results in a narrower cab.
This is something I didn't appreciate until I started assembly. I used relatively thin wood and each cab with four 12" drivers was 12" wide by 24" tall. I could have easily knocked 2" off of the width by making those mounting plates each 1" thicker. That would have reduced my central pathway to 3" instead of 4" and the 2 rear pathways 1.5" each instead of 2".
Note that I added 8" with cross bracing to the rear of mine, which adds 16" of rear wave travel distance and some U baffle behavior. This increases extension by more than a full octave or over +6db at the bottom with only a small increase in overall size. Also note that my W/U/Ripole/push-pull/mechanical cancellation subs do require damping in the rear pathway for proper operation. Too bad I went to the trouble using cheapie woofers I already had. At some point I plan to build something similar using eight 6x9's per side, resulting in stable high bass output OB speaker stands in a very compact form. |
Do you mean like this (see rough figure) aiming to satisfy the following criteria:
1. minimize the center "common" chambers
2. ensure that the sum of the heights top and bottom chambers are equal to the height of the common chamber
3. ensure that the height of the top chamber = the height of the bottom chamber
Why do you prefer magnet to cone orientation vs. cone to cone or magnet to magnet orientation. Is it just for space efficiency?
In your experience, How does ripole bass compare to OB bass, subjectively? |
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| Saturnus |
| quote: | Originally posted by zobsky
Why do you prefer magnet to cone orientation vs. cone to cone or magnet to magnet orientation. Is it just for space efficiency? |
In theory cone-to-magnet orientation cancels out the compression distorion of each driver as the cone moves back and forth. And particularily in OB designs there might be more to gain from this orientation than in closed box where it creates it's own compression distortion. |
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| chops |
| quote: | Originally posted by zobsky
Chops, ... I read through your thread. Do these drivers need EQ'ing up on the low end (possibly by the bass boost on a sub amp) ?
Thanks |
Nope. They were pretty flat to about 16-18Hz on their own. The only bit of EQ I used was to take out a few dB between 90-125Hz where the xover freq was. |
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| johninCR |
| quote: | Originally posted by zobsky
Do you mean like this (see rough figure) aiming to satisfy the following criteria:
1. minimize the center "common" chambers
2. ensure that the sum of the heights top and bottom chambers are equal to the height of the common chamber
3. ensure that the height of the top chamber = the height of the bottom chamber |
All three, though I'm not sure you want to minimize the "common" pathway, since you could make it too small. With my thin mounting plates the thinnest possible was a little big, even with holes in the side panels for the 2 outward magnets to poke through (an added complication and detraction from beauty.
In your drawing the 2 mounting plates are different thicknesses and you definitely don't want that, because everything won't be symmetrical.
| quote: | | Why do you prefer magnet to cone orientation vs. cone to cone or magnet to magnet orientation. Is it just for space efficiency? |
With all 4 in 1 cab, just space efficiency, since 2 cone to cone and 2 magnet to magnet would still be push-pull. With only 4 drivers I'd suggest 2 cabs for maximum flexibility in placement, in which case cone to magnet is required for push-pull. Also, I find stereo into the bottom octave more important with open alignments even if the signal is mono.
| quote: | | In your experience, How does ripole bass compare to OB bass, subjectively? |
Same as a W, but flatter bottom end, just as discussed in the original ripole thread. ie EQ may not be needed.
Note that I believe the folded W's, N's, ripoles sound subjectively different than having the front wave directly radiated from the driver, with the folded types sounding slightly "mushy". Think about it, the sound wave has to be "mushed" out of that pathway. This may be an aural illusion caused by the limited upper end extension of the folded alignments. IMHO folded alignments are only for stealth (hide the drivers), space savings (U's can be smaller for same extension), mechanical vibration cancellation (for W's), prettier push-pull, flattening response (ripoles), and lowering Fs due to the air mass loading of ripoles (and lesser extent W's and N's that aren't ripole). In other words, fold only if EQ isn't an option or the bass cab will also function as the base of the main speaker.
Though a U may have a greater minimum width, given the same depth, in terms of bottom end potential, 1 driver in a U is equal to 2 drivers in a folded dipole. It doubles the rear wave pathway, adding +6db at the bottom (same as adding another driver). The radiation pattern is different, but I don't find a great sonic difference. This is probably because a dipole close to a wall isn't really a dipole anymore. It's a dipole + wall, which can't produce a figure 8. |
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| chops |
I don't know about you guys, but I am totally confused now.
Thicker baffles, smaller air spaces, ripoles that are part ripole, part W-baffle, part U-baffle... I don't know if I'm coming or going! :bawling:
Isn't a ripole pretty much the same thing as an N-baffle (half of a W-baffle), but with the front and rear walls closer to the woofer to build up a little bit of a load on the driver, effectively lowering the Fs some? IOW, isn't a ripole a smaller, narrower, more compact N-baffle dipole? |
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| zobsky |
| quote: | Originally posted by johninCR
With all 4 in 1 cab, just space efficiency, since 2 cone to cone and 2 magnet to magnet would still be push-pull. With only 4 drivers I'd suggest 2 cabs for maximum flexibility in placement, in which case cone to magnet is required for push-pull. Also, I find stereo into the bottom octave more important with open alignments even if the signal is mono.
Same as a W, but flatter bottom end, just as discussed in the original ripole thread. ie EQ may not be needed.
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Yes, ... the reason I've bought 4 drivers is to build 2 cabinets, a pair to each. Each cabinet will POSSIBLY (or not) serve as a stand for the main speaker , depending on how they perform at that position (approximately 1m from rear and 0.5 m from side walls) |
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| theAnonymous1 |
Mine will also serve as the bottom portion of my speakers. The top will have a 10" driver fo the midbass/mids and then Heil AMT for the mid/highs.
Man, I really need to find someone local to cut some wood for me. I'm limited to what a jigsaw can do in an apartment.:bawling:
Chops, your not going crazy; a ripole IS just a N/W baffle with restricted openings. |
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| johninCR |
Zobsky,
There's a catch with 2 drivers per cab, and that is how are you going to get equal loading if you do it in a W alignment to get the vibration cancellation too? That's the main reason I went with 4 in each cab, to get everything including the symmetry required for the Ripole concept.
Chops,
Yes, the original ripole is a double driver "N". I give credit where I think it's due by calling mine Ripole hybrids, since I'm trying to take advantage of the restricted pathway to mass load the driver for flatter extension down low. |
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| y8s |
I have 4 of the Stryke AV15 woofers that I originally bought intending to use as the woofer modules for some Linkwitz Phoenix speakers.
I may try to re-build their W baffles into a ripole config.
I googled a bit to find the parameters of a ripole. it found a post by johninCR saying you make the openings 25-30% of the driver's Sd.
Specs on the AV15:
Fs: 19.7 Hz
Qms: 4.71
Qes: .399
Qts: .368
Vas: 228 L
Re: 2.97 ohm
Z: 4 ohm
(dual 2 ohm)
BL: 15.5 Tm
Cms: .25 mm/N
Mms: 260 g
Pe: 500W
1W/1m: 88.5dB
2.83V: 92.5dB
Xmax: 23 mm
Xsus: 30 mm
Sd: 802 sq cm
Vd: 3.8 L |
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| johninCR |
| quote: | Originally posted by y8s
I have 4 of the Stryke AV15 woofers that I originally bought intending to use as the woofer modules for some Linkwitz Phoenix speakers.
I may try to re-build their W baffles into a ripole config.
I googled a bit to find the parameters of a ripole. it found a post by johninCR saying you make the openings 25-30% of the driver's Sd.
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If those are the real deal drivers with the shorting rings, etc, I 'd be hard pressed to bury them inside folded baffles.
Also, the thread you want about ripoles starts with a thread titled "Honey I shrank the dipoles". If I mentioned that ratio, then that's where I got the info. |
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| zobsky |
| quote: | Originally posted by theAnonymous1
Mine will also serve as the bottom portion of my speakers. The top will have a 10" driver fo the midbass/mids and then Heil AMT for the mid/highs.
Man, I really need to find someone local to cut some wood for me. I'm limited to what a jigsaw can do in an apartment.:bawling:
Chops, your not going crazy; a ripole IS just a N/W baffle with restricted openings. |
Can't you get the folks at Home Despot to cut you up some MDF (their saws are usually brutal on plywood)? Most of the pieces should be fairly similar in size. All you'd have to do at that point is make the cutouts using your jigsaw and assemble the unit. |
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| ashok |
For the W shape what is the requirement for air volume ( mass ) behind and in front of the driver. I would guess that the volume in front of and behind the driver should be equal. Additionally the openings should have the same area in front and behind ( per driver ).
Would this make it look like a slot loading on both sides of the driver?
Would the air volume be a multiple of the maximum that the driver can move at Xmax ? Say 3.33 times if the vent area is 33% Sd? Is there any relationship ?
Cheers. |
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| salas |
| Is the sound of a W frame as uncolored as the sound of an H frame? |
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| ashok |
| Since the W frame has a shorter path to the exit, maybe it should have resonances starting at a higher frequency and so be cleaner sounding when used with an appropriate crossover ? |
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| theAnonymous1 |
| quote: | Originally posted by zobsky
Can't you get the folks at Home Despot to cut you up some MDF (their saws are usually brutal on plywood)? Most of the pieces should be fairly similar in size. All you'd have to do at that point is make the cutouts using your jigsaw and assemble the unit. |
These will hopefully be my permanent subs for the foreseeable future, so Home Depot is not an option. I know from past experience that their cuts can be WAY off. I also want to do magnet cutouts on the outside walls with a router which I don't have either.
ashok, Ideally you want equal openings on the front and rear. If your going for a "ripole" this usually isn't possible because of the size of the basket and magnet. You can make cutouts for the magnets, but the basket will probably keep you from getting an opening ~30% of Sd. From what I've seen most people just make the back opening as small as possible and then apply the ~30% Sd rule to the front opening.
The "volume" of the opening isn't relevant other than you want it as small as you can make it; i.e. just big enough to fit the driver. This helps push the resonance up in frequency. It's the area of the opening that is important.
My front cavity will be 15.5" x 15.5" x 2.5". The back will be roughly 15.5" x 15.5" x 4". |
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| ashok |
| OK , I have an idea that will make both openings equal. Will try it out before talking about it !:D |
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| chops |
| quote: | Originally posted by theAnonymous1
These will hopefully be my permanent subs for the foreseeable future, so Home Depot is not an option. I know from past experience that their cuts can be WAY off. I also want to do magnet cutouts on the outside walls with a router which I don't have either.
ashok, Ideally you want equal openings on the front and rear. If your going for a "ripole" this usually isn't possible because of the size of the basket and magnet. You can make cutouts for the magnets, but the basket will probably keep you from getting an opening ~30% of Sd. From what I've seen most people just make the back opening as small as possible and then apply the ~30% Sd rule to the front opening.
The "volume" of the opening isn't relevant other than you want it as small as you can make it; i.e. just big enough to fit the driver. This helps push the resonance up in frequency. It's the area of the opening that is important.
My front cavity will be 15.5" x 15.5" x 2.5". The back will be roughly 15.5" x 15.5" x 4". |
I was just thinking, if you can't make the rear cavity smaller due to the driver's basket, what if you reduce the size of the opening? IOW, build a small frame that fits inside the rear opening of the ripole to increase the resistance?
Would something like that work, or would it be altering the sound too much in a bad way? |
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| theAnonymous1 |
| quote: | Originally posted by chops
I was just thinking, if you can't make the rear cavity smaller due to the driver's basket, what if you reduce the size of the opening? IOW, build a small frame that fits inside the rear opening of the ripole to increase the resistance?
Would something like that work, or would it be altering the sound too much in a bad way? |
I was thinking of putting triangle shaped pieces of wood the depth of the cavity in the corners opposite the driver. I don't think it would have a negative effect on the sound.
Here is a horrible mspaint sketch.......
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| y8s |
| quote: | Originally posted by johninCR
If those are the real deal drivers with the shorting rings, etc, I 'd be hard pressed to bury them inside folded baffles.
Also, the thread you want about ripoles starts with a thread titled "Honey I shrank the dipoles". If I mentioned that ratio, then that's where I got the info. |
They are the preorder Stryke units... but why would you be hard-pressed to bury them inside the baffles? Too pretty or not well-suited? Size-wise, it's quite unfeasible to make a 30 x 15 H baffle (x2) if you ask my gf and roommate :)
| quote: | Originally posted by ashok
Since the W frame has a shorter path to the exit, maybe it should have resonances starting at a higher frequency and so be cleaner sounding when used with an appropriate crossover ? |
the W frame is generally designed so that "D", the dipole distance, is equal to the H frame "D". I guess it's actually the average D since the outer edge of the driver is closer to the outer edge of the other driver and the inner edge is further. |
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| salas |
| But do they in the end subjectively sound indistinguishably similar? I mean different frames with same ''D''. Has anyone built several types and has the subjective experience? |
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| chops |
| quote: | Originally posted by y8s
They are the preorder Stryke units... but why would you be hard-pressed to bury them inside the baffles? Too pretty or not well-suited? Size-wise, it's quite unfeasible to make a 30 x 15 H baffle (x2) if you ask my gf and roommate :)
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I believe he was referring to the fact that those drivers are too good for being in folded baffles. At least, that's how I understood it. |
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| johninCR |
| quote: | Originally posted by salas
But do they in the end subjectively sound indistinguishably similar? I mean different frames with same ''D''. Has anyone built several types and has the subjective experience? |
I've built all types and then some. They sound different to me as I mentioned in a previous post, and I've settled on direct front radiation only which also excludes H's due to the cavity in front. U-baffles &/or small flat baffles for me. IMHO pure dipole isn't a requirement for great OB sound.
| quote: | Originally posted by chops
I believe he was referring to the fact that those drivers are too good for being in folded baffles. At least, that's how I understood it. |
Yes, if they're the drivers I've heard mention of with copper shorting rings, phase plugs, etc. |
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| salas |
| quote: | Originally posted by johninCR
I've built all types and then some. They sound different to me as I mentioned in a previous post, and I've settled on direct front radiation only which also excludes H's due to the cavity in front. U-baffles &/or small flat baffles for me. IMHO pure dipole isn't a requirement for great OB sound.
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I have built U with felt at the back, flat with side triangular wings, and H. U was deeper and more controlled, with flat slightly more open in the mid bass but shallower. H was slightly 'covered' sounding. So I was persistent in asking for the other configurations since I have never built them, but I could feel they must have a signature. Thanks for sharing your experience.
:wave: |
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| johninCR |
| quote: | Originally posted by salas
I have built U with felt at the back, flat with side triangular wings, and H. U was deeper and more controlled, with flat slightly more open in the mid bass but shallower. H was slightly 'covered' sounding. So I was persistent in asking for the other configurations since I have never built them, but I could feel they must have a signature. Thanks for sharing your experience.
:wave: |
Salas,
U-baffles require more damping than just felt for them to function properly. This is something not generally understood. Without adequate damping the air in the cavity will behave as a lumped mass. This not only creates a resonance, but it also makes the cavity terminus effectively the source for the rear wave giving you only half the extra travel distance for it. IOW you give up an octave, 6db, at the bottom. This is the case for a perfect U, ie driver mounted on the end of a short pipe. As you get away from this shape toward a more open back, the lumped mass behavior fades until there is no resonance and damping isn't necessary for proper low end performance. Note that this all occurs below 1/4 wavelength of the pipe and sonics above that frequency are a different animal.
H baffles exhibit the same behavior if you look at the front and rear waves separately, but when they are uniform front and back the resonance is far less audible because the front and rear components cancel each other out to a large extent. If you have an H baffle used purely for subwoofer frequencies with cavities not much larger than the driver, then you can stuff the rear cavity and pick up 1/2 octave of extension with a small change in the dispersion pattern. You could also stuff the back and cut the front off for the same extension in a smaller size.
Lastly, you should note that the difference in dispersion pattern between U's and dipoles (H's and others) can work to your advantage or disadvantage in your room. In my room, I find that U's sound better if the placement is to be near the front wall, but with placement near the side walls and out away from the front wall, I like dipoles better. It seems to be directly related to the dispersion pattern and how the rear wave reflections occur in your room.
Once you obtain adequate extension and output, and get things matched to your room, then from an SQ point of view boxed bass becomes a joke in comparison to open alignments, so it's worth the effort. Once you hear good OB bass, bass from boxes sounds like jumbled mush due to a far greater amount of reflections as a percentage of what you hear.
I think that's enough for today from the OB bass pulpit.
John |
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| salas |
| Thanks. So a good U frame better be 50-100% stuffed? What is the most successful stuffing strategy? Please refer in detail when you feel like it. |
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| zobsky |
Here's 1 of my 2 pairs on a scrap MDF board .
I'll use this (admittedly not optimal) dipole setup as a basis to compare my ripoles. I should probably flip the mdf board so that the drivers are closer to the floor. Luckily, the drivers I got had the push/Clip type binding posts so re-configuring drivers should be easy.
Initial impressions, .. not as deep or efficient as the tuba horn in the background, ....though this setup is nowhere optimal. However, the bass is punchy and does extend down to the high 30s at least.
The bass is strong and even sounding, .. no major peaks to worry about, ... probably because it nukes the room modes that have been bothering me. Also, the bass is not floppy or woolly sounding. Running a frequency sweep at the listening position, I see that it's moderately even with a sharp null around 65 Hz, which is not an audible problem. I suspect this is placement related.
More to come
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| chops |
| quote: | Originally posted by zobsky
Initial impressions, .. not as deep or efficient as the tuba horn in the background, ....though this setup is nowhere optimal. However, the bass is punchy and does extend down to the high 30s at least.
The bass is strong and even sounding, .. no major peaks to worry about, ... probably because it nukes the room modes that have been bothering me. Also, the bass is not floppy or woolly sounding. Running a frequency sweep at the listening position, I see that it's moderately even with a sharp null around 65 Hz, which is not an audible problem. I suspect this is placement related.
More to come
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If that baffle was twice the size, you would get considerably better bass extension.
Mine were also very smooth throughout the entire range up to 125Hz where they were crossed over. The only thing I had to do was use a bit of EQ to lower the output around the xover freq just a little.
The 65Hz null you have is mostly due to your room more than just placement. If it's a sharp roll-off, that's what would be known as a "suck-out". I'm not sure if there's anything that can be done about that other than heavy room treatments. Trying to EQ it won't do anything but overdrive the signal and drivers, and very little if any to improve it. |
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| zobsky |
| quote: | Originally posted by chops
If that baffle was twice the size, you would get considerably better bass extension.
Mine were also very smooth throughout the entire range up to 125Hz where they were crossed over. The only thing I had to do was use a bit of EQ to lower the output around the xover freq just a little.
The 65Hz null you have is mostly due to your room more than just placement. If it's a sharp roll-off, that's what would be known as a "suck-out". I'm not sure if there's anything that can be done about that other than heavy room treatments. Trying to EQ it won't do anything but overdrive the signal and drivers, and very little if any to improve it. |
I agree about the larger baffle = better bass. I just used that 2 x 4 board for evaluation because it was $0.50 scrap at home depot.
The null I talk about isn't bothersome, so I'm not going to dwell upon it any more for now. We'll see how things work out when I start building the ripoles. |
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| y8s |
| quote: | Originally posted by zobsky
I agree about the larger baffle = better bass. I just used that 2 x 4 board for evaluation because it was $0.50 scrap at home depot.
The null I talk about isn't bothersome, so I'm not going to dwell upon it any more for now. We'll see how things work out when I start building the ripoles. |
just remember the "D" on that 50 cent baffle is not the same as the "D" you'd use for the ripole. they may not compare very well. The D on your flat baffle is the average radius of the baffle. On the ripole it's the depth from front to back. |
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| tomtom |
| quote: | Originally posted by johninCR
Once you obtain adequate extension and output, and get things matched to your room, then from an SQ point of view boxed bass becomes a joke in comparison to open alignments, so it's worth the effort. Once you hear good OB bass, bass from boxes sounds like jumbled mush due to a far greater amount of reflections as a percentage of what you hear.
I think that's enough for today from the OB bass pulpit.
John |
Hi sorry for little OT
from what i see you know what you talking about. I have question about driver for OB sub /i mean from Thiele small POV/- i read too match different opinions about QTS /lets say 15''/ somebody say 1+ /martin king/ somebody the less the better
- totally different directions.
So where is good point to start - get the good drivers and than just attenuate baffle enclosure to match room and taste
Thank you very very much
Tomas |
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| zobsky |
| quote: | Originally posted by y8s
just remember the "D" on that 50 cent baffle is not the same as the "D" you'd use for the ripole. they may not compare very well. The D on your flat baffle is the average radius of the baffle. On the ripole it's the depth from front to back. |
Agreed, I knew that from the start. The dipole baffle is nowhere near optimal but it's purpose is more as a standard to compare the tonality and sound character of different alignments. |
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| theAnonymous1 |
Zobsky, you have no idea how jealous I am you will have your PPA15 ripoles done before me.:bawling:
I've been sitting on these drivers so long it's making me crazy!
Oh well, I'm sure you will post some info that will come in handy when I get around to building mine. |
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| y8s |
| quote: | Originally posted by zobsky
Agreed, I knew that from the start. The dipole baffle is nowhere near optimal but it's purpose is more as a standard to compare the tonality and sound character of different alignments. |
OK just checking ;) |
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| zobsky |
| quote: | Originally posted by theAnonymous1
Oh well, I'm sure you will post some info that will come in handy when I get around to building mine. |
Hopefully, my ripoles won't end up as a big flop and others can benefit by my experiment. I feel your pain about being limited by an apartment. Been there, done that.
In any case, my construction thread is here (not much there , YET)
http://www.diyaudio.com/forums/show...576#post1308576 |
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| Rudolf |
| quote: | Originally posted by tomtom
I have question about driver for OB sub /i mean from Thiele small POV/- i read too match different opinions about QTS /lets say 15''/ somebody say 1+ /martin king/ somebody the less the better
- totally different directions. |
In OBs there is no "one size fits all".
If you look closer you might find a system behind the different opinions: Real open (and small) baffles are a big shortcut for bass energy. To regain bass, you need a high Qts - or some heavy electronic equalisation which is expensive to achieve with passive components.
If you use some kind of frame (U, W, H) bass response is less attenuated. Especially in a ripole the combination of acoustic mass loading and passive filter will result in a bass response that doesn´t need help from the driver Qts. |
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| Calvin |
Hi,
"Especially in a ripole the combination of acoustic mass loading and passive filter will result in a bass response that doesnīt need help from the driver Qts."
That is simply not true. Even Ripoles canīt defy the laws of physics.
Higher Q always means more output at the Fs. In a ripole it means less, or even no lowbass-equing with a very high Qt-driver.
jauu
Calvin |
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| ashok |
I was planning on taking measurements on some variations of a dipole sub . Would there be any preferable specific distance to use ( front baffle from rear wall ) that would help to compare the results with what others have done?
I was thinking of using 3 feet (?). |
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| Rudolf |
Since nobody else seems to care :( :
I would recommend to take measurements in the opening plane(s) of the manifold. These will not show the dipole roll-off, but the 6dB roll-off is predictable. And it is the only measurement in a room that will be sufficiently free from room effects.
Next is a measuring distance of 1 m - preferably gated to exclude first reflections from font and side walls. It would be advisable to place the sub in the middle of the room for this.
You could take measurements at your listening position. They will not be really comparable to measurements in other rooms, but you could see how "flat" you manage to get compared to others.
There is really no sense in measuring with a specific distance to front or side walls. Individual room width and depth will have too much influence already with such configuration to make it comparable to other rooms. |
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| ashok |
Thank you Rudolf. Yes your suggestions are right. I'll put up some measurements and pictures as soon as I have them.
I can't get the dipole sub off my mind and so I have to get them tested soon !
I had tested a dipole planar last year and it sounded great. It's been in storage for various reasons and will be brought out again sometime soon. I've just started on an 8inch driver and 1 inch dome OB . Hope to get it working soon.
Cheers,
Ashok. |
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| crazybastard |
| I've been thinking about a ripole design for a long time. The very compact nature of the enclosure is appealing to my curring project. I have a pair of Tempest 15" woofer that I plan to load into a ripole W enclosure. I was reading their website again...seems there is a substantial loss of output with these enclosures. Their woofer has a sensitivity of 88db/watt, but in a ripole that drops down to 80!! Am I not reading something correctly? |
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| zobsky |
| quote: | Originally posted by jimluu
I've been thinking about a ripole design for a long time. The very compact nature of the enclosure is appealing to my curring project. I have a pair of Tempest 15" woofer that I plan to load into a ripole W enclosure. I was reading their website again...seems there is a substantial loss of output with these enclosures. Their woofer has a sensitivity of 88db/watt, but in a ripole that drops down to 80!! Am I not reading something correctly? |
Yes,
you will have a fair bit of efficiency drop with a ripole. Do let us know how it turns out if you build one. I ended up building a pair of W-U stuffed hybrids (awaiting power amp, .. old amp died just as I finished the enclosures) , as my drivers didn't work very well in a ripole (too high Qts of 0.7, .. your tempests should be better suited) , . bass went moderately low but no slam, and too low efficiency to keep up with the arrays.
The W-U are good to an honest 30 - 35 Hz, .. .though I still need the horn sub for home theater style bass-slam. |
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| chops |
| quote: | Originally posted by zobsky
Yes,
you will have a fair bit of efficiency drop with a ripole. Do let us know how it turns out if you build one. I ended up building a pair of W-U stuffed hybrids (awaiting power amp, .. old amp died just as I finished the enclosures) , as my drivers didn't work very well in a ripole (too high Qts of 0.7, .. your tempests should be better suited) , . bass went moderately low but no slam, and too low efficiency to keep up with the arrays.
The W-U are good to an honest 30 - 35 Hz, .. .though I still need the horn sub for home theater style bass-slam. |
Hey Zobsky, have you tried your hybrids near the side walls/corners of the room at all, or just in the middle of the room as in the picture above?
The reason I ask is because my original dipole subs using the PPA15's produced some serious bass right along side the side walls and about 3 feet out from the front wall. Then again, my H baffles were considerably larger than your W-U hybrids.
I see you get honest output down to about 30Hz or so, but how do they sound overall? And how high do you have them crossed over?
BTW, I don't know if you noticed, but I built some more huge OB's for myself again. Here's the link to my thread...
http://www.diyaudio.com/forums/show...threadid=111318 |
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| zobsky |
| quote: | Originally posted by chops
Hey Zobsky, have you tried your hybrids near the side walls/corners of the room at all, or just in the middle of the room as in the picture above?
The reason I ask is because my original dipole subs using the PPA15's produced some serious bass right along side the side walls and about 3 feet out from the front wall. Then again, my H baffles were considerably larger than your W-U hybrids.
I see you get honest output down to about 30Hz or so, but how do they sound overall? And how high do you have them crossed over?
BTW, I don't know if you noticed, but I built some more huge OB's for myself again. Here's the link to my thread...
http://www.diyaudio.com/forums/show...threadid=111318 |
Hi,
I've tried varying the position a little but not to much, as the corners aren't free and one side wall is flanked by a door and the other by a large mirror, so I don't have too many placement option . Off topic, but FWIW, I couldn't hear any improvement when using a linkwitz (cone to magnet) mounting pattern, . so that's why I used a symmetric mounting pattern.
I hesitate to give a full review because this is still a work in progress and my power amp is dead (waiting for a replacement) but in any case, .....
These were actively crossed over between 80 and 100 Hz (either 2nd order or 4th order, depending on which crossover I used). I'm not happy with them crossed too much higher higher (breakup / resonant sound) The baffles are stuffed with polyfill. They sound good within their passpand (punchy and clean) though I get the feeling that there's still a little bit of resonance even below that (not sure if it's the room or the sub - most subs I've had in this room have that issue). I still want to brace a wall or two in the rear. Their intended application will be mid-bass cabinets ie. 100-120 Hz to 40 Hz (my arrays roll off naturally below 100 Hz anyway) . A horn sub will provide the goods below that. Once again, this is a work in progress.
Good job on the new monster OBs. If only I had more rooms at home, I'd be churning out more projects. |
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| kjgarrison |
Noob alert!!
I was reading this thread but it looks like it fizzled out.
I was reading here because an idea for a project I've been looking at was called a 'ripole'. It looks a lot like the W design mentioned here.
But with differences. I'm working on an IB project. If the restrictions of the openings' CSA's discussed in this thread are all taken away leaving wide open forward and rearward flow, and if the rearward flow is attached to another room, an attic, or a basement, would this be an IB, a ripole, or a ripole IB?
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| Calvin |
Hi,
itīd be an IB.
jauu
Calvin |
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| ashok |
| Wouldn't the enclosure still affect the Fs due to the air mass / slot loading etc. ? and not just be like a driver on a very large flat baffle. |
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| Rudolf |
AM,
may be Calvin found these aspects too complicating for a self declared noob. ;)
But of course the cavities will mass-load the driver and lead to the usual quarter-wave resonance peaks. |
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