Single woofer, I think it was in an U-frame.
All BMS's woofers have the topmost aluminum shorting ring on the pole piece, it can be used as a phase plug holder. I made (my machinist made) the phase plug's base to fit tightly inside the shorting ring, and after the shorting ring ends, the plug expands to same diameter as the shorting ring's outer diameter so there are no gaps and phase plug is centered automatically. Thermal and electrical coupling is also very good.
The plugs is secured with a M10 bolt through the motor's center hole. Right now I use steel bolts, but aluminum/brass would be better.
An externally hosted image should be here but it was not working when we last tested it.
Sim of Slot Loaded Push-Pull Vented Back Sub
Here is a design for kind of an over-the-top SLPP vented back sub using the monster Faital Pro 18XL1600 drivers (http://www.faitalpro.com/products/files/18XL1600/4/18XL1600_datasheet_4.pdf)with 98 dB efficiency and 12.9mm of xmax. There are two drivers wired in parallel in a push-pull slot in a box with a very large rear facing vent that can be stuffed and damped if desired. The box is approximately 40 in deep x 36 in wide x 22 in tall with a 16 in wide x 20 in tall x 24 in deep slot that feeds a front horn expanding to 30 in wide over 15 in distance. The volume of the box is 470 liters and there is a 7 in x 13 in rear facing port that is 20 in long. The drivers are fed with up to 56 volts to hit xmax through a -24dB/oct HPF set at 21 Hz.
Here is the response at 2.83V and 1 meter on axis:
Some EQ'ing will be needed to flatten the 95 Hz peak characteristic of slot loaded designs.
Here is the cone displacement at 56v to reach 12.9 mm xmax:
Here is the corresponding SPL at xmax:
Here is the impedance:
Here is the velocity in the rear vent and front slot at xmax:
If you enlarge the rear vent, the bass extension drops and you will have to apply EQ to increase the SPL at low frequencies. This driver is perfect for that though with 12.9 mm xmax. It wasn't my intent to use this driver to produce 120+ dB but to have the headroom there so that EQ can be applied if needed.
Here is a design for kind of an over-the-top SLPP vented back sub using the monster Faital Pro 18XL1600 drivers (http://www.faitalpro.com/products/files/18XL1600/4/18XL1600_datasheet_4.pdf)with 98 dB efficiency and 12.9mm of xmax. There are two drivers wired in parallel in a push-pull slot in a box with a very large rear facing vent that can be stuffed and damped if desired. The box is approximately 40 in deep x 36 in wide x 22 in tall with a 16 in wide x 20 in tall x 24 in deep slot that feeds a front horn expanding to 30 in wide over 15 in distance. The volume of the box is 470 liters and there is a 7 in x 13 in rear facing port that is 20 in long. The drivers are fed with up to 56 volts to hit xmax through a -24dB/oct HPF set at 21 Hz.
Here is the response at 2.83V and 1 meter on axis:
Some EQ'ing will be needed to flatten the 95 Hz peak characteristic of slot loaded designs.
Here is the cone displacement at 56v to reach 12.9 mm xmax:
Here is the corresponding SPL at xmax:
Here is the impedance:
Here is the velocity in the rear vent and front slot at xmax:
If you enlarge the rear vent, the bass extension drops and you will have to apply EQ to increase the SPL at low frequencies. This driver is perfect for that though with 12.9 mm xmax. It wasn't my intent to use this driver to produce 120+ dB but to have the headroom there so that EQ can be applied if needed.
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Legis,
I have similar phase plug for woofer which has a section at the bottom to fit in the ventilating hole in pole peice.
It's snug. And I just use a bit screw glue to secure it in place. Zero problem for years.
You can do simliar thing to your plugs and save the bolts.
I have similar phase plug for woofer which has a section at the bottom to fit in the ventilating hole in pole peice.
It's snug. And I just use a bit screw glue to secure it in place. Zero problem for years.
You can do simliar thing to your plugs and save the bolts.
Do you have a machinist custom make these? They look really nice and I guess also lowers distortion. You can probably just make the lower part where the voicecoil extends over for a shorting ring and the rest of the cone can be non conductive even (wood or plastic). Copper would work even better.
Yes, custom-made.
Distortion? Not feeling it and can't measure it. LoL.
I didn't even see reduction of inductance in higher frequency when run them on WT3 before and after.
Distortion? Not feeling it and can't measure it. LoL.
I didn't even see reduction of inductance in higher frequency when run them on WT3 before and after.
I did not see it either, the inductance at the coil's resting place is approx. the same regardless of the plug. My theory is that Le(X) got better, the inductance variance got smaller depending on the voice coil's position. Depending on the motor's design, it might also get worse with metallic plugs.
I have phase pluged 8" midwoofers in my dipole line arrays. They have a basic motor design and had the phase plug sitting right on the iron pole piece (attachment method exactly the same as you have with the plugs). I measured quite different Le when the cone was pressed inwards vs. pulled outwards. BMS's woofers do not exhibit same kind of (absolute nor relative) difference in Le depenging on the VC position. I cannot measure reliably anything though, one should have some kind of device that moves the cone precisely the same amount each time inwards or outwards.
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BMS's also have smaller vents in the voice coils perimeter in the back of the motor. The wooden "washer", that hold the plug, seals also them. In dipole they do not matter but in boxed applications they would count as leaks.
Do the plugs come of if you have to take them apart? What are their size and mass? Mine are 2,8kg and 4" x 5,5" / 100mm x 140mm.
I have gotten the idea that DCR of the shorting ring matters the most. Basically the shorting ring/phase plug can be kept shorter (metallic base and wooden tip for ex.) and/or even hollow, but the DCR goes up compared to bigger plug.
Copper or brass plugs would look really nice (and weight a ton)! Maybe some day... 🙂
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Do the plugs come of if you have to take them apart? What are their size and mass? Mine are 2,8kg and 4" x 5,5" / 100mm x 140mm.
I have gotten the idea that DCR of the shorting ring matters the most. Basically the shorting ring/phase plug can be kept shorter (metallic base and wooden tip for ex.) and/or even hollow, but the DCR goes up compared to bigger plug.
Copper or brass plugs would look really nice (and weight a ton)! Maybe some day... 🙂
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My phase plug is 3" O.D. Don't remember other numbers. There should be a drawing somewhere, I can't find it now...
Would it come off when needed? I suppose so. The adhesion of screw glue is not very strong. If it can't be pulled off from the front, I may use a long stuff to push it out from the rear end of pole piece ventilating hole.
Time flys. It's been 5 years and I can't think of any reason to take them apart.
Would it come off when needed? I suppose so. The adhesion of screw glue is not very strong. If it can't be pulled off from the front, I may use a long stuff to push it out from the rear end of pole piece ventilating hole.
Time flys. It's been 5 years and I can't think of any reason to take them apart.
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Although I enjoy discussions of phase plug nirvana do you guys have any comments on the slot loaded sub with big rear vent? Let me know if you want me to run a particular driver for you.
Right now I'm thinking if I go PPSL, it might be closed box, or the bandpass that you posted earlier. I still try to get hold on the bandpass, woofers radiating to the bass reflex port, huh. Something feels quite risky about it. Has anyone heard something like that in real life or are there any commercial produts like that?
There are lots of pro audio subs that use this. My one sample that I built using 5 in drivers sounds very nice. I can imagine how loud it would be at 18 in. It is omni and monopole for sure but sure is smooth and wide bandwidth. My build with six 6.5 in drivers in open baffle SLPP is one of the cleanest sounding subs. Very natural presentation. Needs to be far from walls though.
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How much more sensitive is the bandpass PPSL compared to similar sized closed PPSL? The regular +3dB around tuning freq like in BR's, or greater than that?
The double 18" PPSL is not really that impressive IMO, a TH in that volume class can easily get you into the 130's with a single high quality 18" or 21". The TH is really just a folded up FLH dipole anyway, it's probably one of the reasons why people identify them as having such good sound.
To be sure, I agree that the TH in a good single 18 in driver will be the most sensitive speaker. You are right in that it is using both sides of the cone as a radiator but its output comes out of one port so it is monopole in practice. TH's really do sound good because of lower distortion because they are so efficient, they don't require much cone movement so HD is kept low. Plus, I think the transient response is cleaner, and group delay can be lower than similarly tuned reflex. I wonder of two TH's back to back with one wired out of phase will give you a super sensitive dipole sub? Hmm... easy to simulate, although the cabinet is now kind of huge as it is doubled in volume and depth.
Well, to my eyes, TH is more like a narrow BLH with the driver at the mouth and no compression chamber.
TBH, I have no first hand experience with TH, just fiddling a bit in hornresp. In various sims, I don't see a clear advantage on TH, compared with other types of horns (or cabinets). A good all round performing TH is still very large. Make it smaller or in other compromises, it's too easily getting a ragged response or limited extension, or both. Maybe OK for pure sub with steep xover, though.
Cost no object, a proper bass FLH is still my king in overall performance. It's the best I've heard. And I've seen others with the same opinion. Here is one of the examples.
OTOH, does it have to be the 'king'? In domestic use, in fact, ultimate SPL capability is really useless. It's like having a hypercar, but never stepping out of the crowded city. A total waste aside, the wrong operating range is all we got most of the time. Eventually, bragging right is not equal to listening pleasure. (I assume it's the common goal of this audio hobby.)
And, the cost (including material and labor) for building a proper bass horn is easily offset by multiple drivers and cheap amp power nowadays. Not to mention precious real estate (floor area, that is).
For Legis' project, I still recommend OB bass for a start. With the capability of those monster woofers, it's really more than enough in domestic use. (It's not for PA, is it?)
And, for listening pleasure, I lost count how many people get in the OB and no return.
Of course, there're also quite a few people stuck with horns.
I've experienced both, now I'm with OB and no regret.
TBH, I have no first hand experience with TH, just fiddling a bit in hornresp. In various sims, I don't see a clear advantage on TH, compared with other types of horns (or cabinets). A good all round performing TH is still very large. Make it smaller or in other compromises, it's too easily getting a ragged response or limited extension, or both. Maybe OK for pure sub with steep xover, though.
Cost no object, a proper bass FLH is still my king in overall performance. It's the best I've heard. And I've seen others with the same opinion. Here is one of the examples.
OTOH, does it have to be the 'king'? In domestic use, in fact, ultimate SPL capability is really useless. It's like having a hypercar, but never stepping out of the crowded city. A total waste aside, the wrong operating range is all we got most of the time. Eventually, bragging right is not equal to listening pleasure. (I assume it's the common goal of this audio hobby.)
And, the cost (including material and labor) for building a proper bass horn is easily offset by multiple drivers and cheap amp power nowadays. Not to mention precious real estate (floor area, that is).
For Legis' project, I still recommend OB bass for a start. With the capability of those monster woofers, it's really more than enough in domestic use. (It's not for PA, is it?)
And, for listening pleasure, I lost count how many people get in the OB and no return.
Of course, there're also quite a few people stuck with horns.
I've experienced both, now I'm with OB and no regret.
Oh, BTW, for such a big project, I think the following threads are very good references, too.
http://www.diyaudio.com/forums/multi-way/252290-altec-vott-a7-using-cad-cnc.html
http://www.diyaudio.com/forums/multi-way/217298-square-pegs-14.html
http://www.diyaudio.com/forums/multi-way/254468-pse-144-horn-discussions.html
A new center channel for the Octagon - AVS Forum
(can't help but thinking, it seems possible to merge the MB OB horn in this project and the HF section by 'square pegs'.... )
😀
It's always a dilemma between 'the eagerness of building something' & 'making a best choice'. And this is why I envy xrk971 so much. He's been experimenting all kinds of concepts, also keeps building and enjoying new things in no time.
http://www.diyaudio.com/forums/multi-way/252290-altec-vott-a7-using-cad-cnc.html
http://www.diyaudio.com/forums/multi-way/217298-square-pegs-14.html
http://www.diyaudio.com/forums/multi-way/254468-pse-144-horn-discussions.html
A new center channel for the Octagon - AVS Forum
(can't help but thinking, it seems possible to merge the MB OB horn in this project and the HF section by 'square pegs'.... )
😀
It's always a dilemma between 'the eagerness of building something' & 'making a best choice'. And this is why I envy xrk971 so much. He's been experimenting all kinds of concepts, also keeps building and enjoying new things in no time.
I haven't decided anything yet, but I had OB bass for last 3 years. I might want to try something else for a change. Fully horn-loaded setup is tempting.
How about something-like-this PP-TH? Tried to quickly simulate it with hornresp and 20-100Hz is possible, but I did not get the response to smoothen out yet. Adding second driver smoothens the output but I'm not sure where exactly the hornresp puts the second woofer in the horn. Should I use the the space in the middle of the drivers (there is an angle in the picture) as the L12 with 2 drivers?
By the way those are the size limits if someone get's a better PP-TH idea.
How about something-like-this PP-TH? Tried to quickly simulate it with hornresp and 20-100Hz is possible, but I did not get the response to smoothen out yet. Adding second driver smoothens the output but I'm not sure where exactly the hornresp puts the second woofer in the horn. Should I use the the space in the middle of the drivers (there is an angle in the picture) as the L12 with 2 drivers?
By the way those are the size limits if someone get's a better PP-TH idea.
An externally hosted image should be here but it was not working when we last tested it.
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Oh, so you've been in OB camp. Do a quick search and found your name among threads of current drive, T-bass.. etc. Do you use them?
If you had experienced T-bass or high impedance drive, then you should try slot-loaded. It brings quite a significant improvement in punch and weight. Subjective, yes, but I'm quite sure it's there.
Horn, very charming, I admit. And the iron law applies here -- bigger is better. See this:
http://www.diyaudio.com/forums/multi-way/125349-3way-horn.html
It's about 150 x 120 x 80 cm overall, I guess you can handle the size. If you're interested, I'll find you the folding.
If you had experienced T-bass or high impedance drive, then you should try slot-loaded. It brings quite a significant improvement in punch and weight. Subjective, yes, but I'm quite sure it's there.
Horn, very charming, I admit. And the iron law applies here -- bigger is better. See this:
http://www.diyaudio.com/forums/multi-way/125349-3way-horn.html
It's about 150 x 120 x 80 cm overall, I guess you can handle the size. If you're interested, I'll find you the folding.
CLS,
I love your 3 way horn design. That beast must be heard to be appreciated. 🙂 you have been playing with this stuff for a long time and it's cool when people ask you to design an over the top concept. It looks like it is in a photography studio. The problem with Hoffman's Iron Law and BIG horns is that any guy lucky enough to have one in his home is either single or a divorce is imminent😀
X
P.S., in keeping with the spirit of the title of this thread I will now design a no holds barred dipole TH with dual 18 in drivers. The box size is not a constraint here but I want to see if I can get a dipole bass pattern rather than omni as seems to happen with many traditional designs unless they are a flat panel OB.
I love your 3 way horn design. That beast must be heard to be appreciated. 🙂 you have been playing with this stuff for a long time and it's cool when people ask you to design an over the top concept. It looks like it is in a photography studio. The problem with Hoffman's Iron Law and BIG horns is that any guy lucky enough to have one in his home is either single or a divorce is imminent😀
X
P.S., in keeping with the spirit of the title of this thread I will now design a no holds barred dipole TH with dual 18 in drivers. The box size is not a constraint here but I want to see if I can get a dipole bass pattern rather than omni as seems to happen with many traditional designs unless they are a flat panel OB.
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