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.
Chops, your not going crazy; a ripole IS just a N/W baffle with restricted openings.
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.
Chops, your not going crazy; a ripole IS just a N/W baffle with restricted openings.
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.
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.
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
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
theAnonymous1 said: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.
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.
air mass requirement
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.
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.
zobsky said:
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".
theAnonymous1 said:
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?
chops said:
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.......
An externally hosted image should be here but it was not working when we last tested it.
johninCR said:
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
ashok said:
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.
y8s said:
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
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.
salas said:
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.
chops said:
Yes, if they're the drivers I've heard mention of with copper shorting rings, phase plugs, etc.
johninCR said:
Ahhh, nope.
http://web.archive.org/web/20040125131837/stryke.com/pics/AV15front.jpg
http://web.archive.org/web/20040125124743/stryke.com/pics/AV15back.jpg
http://web.archive.org/web/20031002030843/www.stryke.com/AVseries.html
I'm ok hiding those in W's.
johninCR said:
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.
salas said:
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.
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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