No articles on the web that I know of. You cna use a search engine, right 
They can help in heat dissipation, partially due to conduction if the phase plug is metal, but largely due to the open area around the phase plug that acts as a leakage path.
It also prevents problems with resonances between the dustcap and pole piece which can reduce the amplitude of the breakup peak before eventual HF rolloff.
They can help in heat dissipation, partially due to conduction if the phase plug is metal, but largely due to the open area around the phase plug that acts as a leakage path.
It also prevents problems with resonances between the dustcap and pole piece which can reduce the amplitude of the breakup peak before eventual HF rolloff.
Hi.
You could try to download three ZIP- files on this page= http://baseportal.de/cgi-bin/baseportal.pl?htx=/Data/exdreamaudio/download
They contains parts of Earl Geddes' "Acoustik Waveguide Theory"...
The "Phase Plug Theory" was originally invented by Bob Smith, but Geddes' articles are better, because he revised some of the theories, where Smith made mistakes.
Greetings, Benny
You could try to download three ZIP- files on this page= http://baseportal.de/cgi-bin/baseportal.pl?htx=/Data/exdreamaudio/download
They contains parts of Earl Geddes' "Acoustik Waveguide Theory"...
The "Phase Plug Theory" was originally invented by Bob Smith, but Geddes' articles are better, because he revised some of the theories, where Smith made mistakes.
Greetings, Benny
Dave Jones said:
You'd be best to ignore some of the silly marketing material that has been repeated in this thread.
It's not really what the "phase plugs" do, so much as what they don't do.
If you don't have a "phase plug", then you have a dust cap. The dust cap is typically a plastic or paper dome. It will exhibit a major fundamental resonance at some frequency, typically a few kHz or so. This is chosen so that the boost from this resonance fills in the falling response from the main cone. So really, a dust cap acts more like a "whizzer cone" than anything.
If you don't need the (resonance induced) frequency extension of a dust cap, then a driver with a "phase plug" will exhibit an earlier, smoother HF rolloff. These drivers work better with lower XO points.
Re: Re: phase plugs
However, the effective piston area is lowered because the phase plug is static. Usually this is negligible unless the coil former (and hence, the pole piece) is huge.
I'd also like to add that there is NO distortion due to the trapped air under the dust cap (the phase plug replaces it the dust cap).Charles Hansen said:
However, the effective piston area is lowered because the phase plug is static. Usually this is negligible unless the coil former (and hence, the pole piece) is huge.
Yes, Charles, you're right.
But another reason for designing speakers with phase- plugs is, that the acoustic waves aren't producing turbulences, whith make the sound of a speaker a little bit more "elegant".
Those turbulences, whitch typically raise right above the cone (as you can see on Timn8tor's pic) are making the sound quality of small speakers sound "squeezed"...
Greetings, B.
But another reason for designing speakers with phase- plugs is, that the acoustic waves aren't producing turbulences, whith make the sound of a speaker a little bit more "elegant".
Those turbulences, whitch typically raise right above the cone (as you can see on Timn8tor's pic) are making the sound quality of small speakers sound "squeezed"...
Greetings, B.
Charles is correct as far as he goes, but didn't mention the main usage of phase plugs, which is in horn loaded drivers. In fact, this is where they originated.
In a horn the throat is typically smaller than the diaphraghm that it loads, and segments of the wave created by the diaphraghm at its edges have to travel a longer distance to the throat than those that originate at the center of the diaphraghm. Thus they arrive at the throat out of phase with the other wave segments. If they meet the other wave segments at or near 180 degrees out of phase cancellation of the wave occurs and high frequency response can be severely restricted.
A phase plug in the horn throat forces the wave segments originating at the diapraghm center to travel around it on their way to the throat, to arrive there at the same time, and thus in phase, with the segments originating at the diaphraghm edge. As a result high frequency response can be greatly extended.
Phase plugs in woofers that are not horn loaded are in fact extensions of the pole-piece and do not have the same purpose as those in horns. Their primary purpose is to eliminate the acoustic resonance that occurs behind a dust cap, and in some cases to also serve as additonal heat sinking for the magnet structure. They are referred to as phase plugs not so because of any phase correction capabilities but because they look similar to the phase plugs used in horn drivers.
In a horn the throat is typically smaller than the diaphraghm that it loads, and segments of the wave created by the diaphraghm at its edges have to travel a longer distance to the throat than those that originate at the center of the diaphraghm. Thus they arrive at the throat out of phase with the other wave segments. If they meet the other wave segments at or near 180 degrees out of phase cancellation of the wave occurs and high frequency response can be severely restricted.
A phase plug in the horn throat forces the wave segments originating at the diapraghm center to travel around it on their way to the throat, to arrive there at the same time, and thus in phase, with the segments originating at the diaphraghm edge. As a result high frequency response can be greatly extended.
Phase plugs in woofers that are not horn loaded are in fact extensions of the pole-piece and do not have the same purpose as those in horns. Their primary purpose is to eliminate the acoustic resonance that occurs behind a dust cap, and in some cases to also serve as additonal heat sinking for the magnet structure. They are referred to as phase plugs not so because of any phase correction capabilities but because they look similar to the phase plugs used in horn drivers.
I agree with most of the thread,
There is a trade off, but a dust cap or dome is not ideal even tho it adds some strength to the cone,
These days floating cones are all the rage, are they better? i honestly dont know! a smooth cone with no dust cap or phase plug looks better and is stronger but the cone attachment adds mass,
A have heard some very good rubber phase plugs that Audax used in there aero gel drivers, i think Seas do there own thing with copper phase plugs to?
I would love to see a large subwoofer with a phase plug or even a bullet cap! that would be something else, the only problem is IMO that phase plus do drop the surface area, but so what!
Look at B&W that use fixed and attached phase plugs, people seem to like the sound, is that any sort of answer?
If i like it, thats all the proof i need, thats my answer.
There is a trade off, but a dust cap or dome is not ideal even tho it adds some strength to the cone,
These days floating cones are all the rage, are they better? i honestly dont know! a smooth cone with no dust cap or phase plug looks better and is stronger but the cone attachment adds mass,
A have heard some very good rubber phase plugs that Audax used in there aero gel drivers, i think Seas do there own thing with copper phase plugs to?
I would love to see a large subwoofer with a phase plug or even a bullet cap! that would be something else, the only problem is IMO that phase plus do drop the surface area, but so what!
Look at B&W that use fixed and attached phase plugs, people seem to like the sound, is that any sort of answer?
If i like it, thats all the proof i need, thats my answer.
Paradise_Ice said:
An externally hosted image should be here but it was not working when we last tested it.
Phase plugs and the magnetic circuit! The Deckware Tweek!
Something that has not been mentioned. The asymetrical magnetic field of the pole piece. There is iron inside the driver and so the field is skewed because the pole piece ends at the top of the top plate (usually), so there is no iron on the outside. Steve Deckert at Deckware has the "Deckware Tweak" to full range drivers. he does a dustcapectomy and uses a suitible sized mechanics SOCKET which is stuck to the pole piece magnetically. It ,of course has a hole in it for the ratchet to engage if used as a wrench . Useing this accomplishes several things . It acts like as a phase plug, it greatly increases cooling in the area but most importantly it restores a lot of symetry to the magnetic flux as there is now iron (the pole piece) on the inside below the VC but NOW also iron (the socket) above the top plate ABOVE the voice coil as well , restoring some magnetic symetry. a much more ballanced arangement. The hole in the socket forms a cavity for resonance (acording to Steve) . Some modern drivers have a SLIGHTLY extended pole piece to accomplish a similar result but not as dramatic a result! We all have a few sockets laying around so give it a try . Works a treat! The "Deckware Tweek" WORKS
Something that has not been mentioned. The asymetrical magnetic field of the pole piece. There is iron inside the driver and so the field is skewed because the pole piece ends at the top of the top plate (usually), so there is no iron on the outside. Steve Deckert at Deckware has the "Deckware Tweak" to full range drivers. he does a dustcapectomy and uses a suitible sized mechanics SOCKET which is stuck to the pole piece magnetically. It ,of course has a hole in it for the ratchet to engage if used as a wrench . Useing this accomplishes several things . It acts like as a phase plug, it greatly increases cooling in the area but most importantly it restores a lot of symetry to the magnetic flux as there is now iron (the pole piece) on the inside below the VC but NOW also iron (the socket) above the top plate ABOVE the voice coil as well , restoring some magnetic symetry. a much more ballanced arangement. The hole in the socket forms a cavity for resonance (acording to Steve) . Some modern drivers have a SLIGHTLY extended pole piece to accomplish a similar result but not as dramatic a result! We all have a few sockets laying around so give it a try . Works a treat! The "Deckware Tweek" WORKS
I thought it had something to do with the higher the frequency the closer to the middle it originates. So by eliminating the center of the cone, the rest of cone can make the high frequencies more predictably. I guess going on the notion of the "mini whizzer cone" theory stated earlier.
This seems to make the most sense to me. Plus there is that phase plug tweeter by Vifa, and that thing is dead flat in its frequency response, one of the best I've ever seen
This seems to make the most sense to me. Plus there is that phase plug tweeter by Vifa, and that thing is dead flat in its frequency response, one of the best I've ever seen
Re: Phase plugs and the magnetic circuit! The Deckware Tweek!
I assume this is why phase plugs are made out of non-magnetic materials.
All reputable manufacturers will have designed for symmetric fields around the air gap. I don't think you're neccessaily getting the mentioned benefits by so crudely altering the flux path without losing something. And I guess you would probably be working with a poor/cheap motor assembly in the first place for it to be of benefit. For example, if you play around with FEMM you will notice how tiny changes can affect the total flux in the air gap, and working for a symmetric field by way of an extended pole piece is one of the tradeoffs. All I'm saying is that adhoc changes to motor without modeling is stabbing in the dark AFAIK.THOR said:Something that has not been mentioned. The asymetrical magnetic field of the pole piece. There is iron inside the driver and so the field is skewed because the pole piece ends at the top of the top plate (usually), so there is no iron on the outside. Steve Deckert at Deckware has the "Deckware Tweak" to full range drivers. he does a dustcapectomy and uses a suitible sized mechanics SOCKET which is stuck to the pole piece magnetically. It ,of course has a hole in it for the ratchet to engage if used as a wrench . Useing this accomplishes several things . It acts like as a phase plug, it greatly increases cooling in the area but most importantly it restores a lot of symetry to the magnetic flux as there is now iron (the pole piece) on the inside below the VC but NOW also iron (the socket) above the top plate ABOVE the voice coil as well , restoring some magnetic symetry. a much more ballanced arangement. The hole in the socket forms a cavity for resonance (acording to Steve) . Some modern drivers have a SLIGHTLY extended pole piece to accomplish a similar result but not as dramatic a result! We all have a few sockets laying around so give it a try . Works a treat! The "Deckware Tweek" WORKS
I assume this is why phase plugs are made out of non-magnetic materials.
stabbing in the dark
Gee, im really sorry to hear that all those speakers designed before computer modeling were all pieces of ****. One of the best speakers of all time, the Tannoy dual concentric , was designed with out modeling software.
YOU state "All reputable manufacturers will have designed for symmetric fields around the air gap."
oh really?Please explain how this is done without symetry in the iron!
"And I guess you would probably be working with a poor/cheap motor assembly in the first place for it to be of benefit. "
Steve works with a top of the line Fostex FR driver and the improvements are easilly heard .
Before you kill any more brain cells with your theretical, modeled assumptions why dont you tear your self away from your putter long enough to actually try this in the real world . its a really simple mod that is reversable! Takes about 10 minutes If you dont like it , just pluck it off the pole piece.
I for 1, am glad there are still people that actually build things and try them out and find what happenes and why, instead of just saying it wont work based on some sim. Right ! Bumble bees cant fly either! Regards
Gee, im really sorry to hear that all those speakers designed before computer modeling were all pieces of ****. One of the best speakers of all time, the Tannoy dual concentric , was designed with out modeling software.
YOU state "All reputable manufacturers will have designed for symmetric fields around the air gap."
oh really?Please explain how this is done without symetry in the iron!
"And I guess you would probably be working with a poor/cheap motor assembly in the first place for it to be of benefit. "
Steve works with a top of the line Fostex FR driver and the improvements are easilly heard .
Before you kill any more brain cells with your theretical, modeled assumptions why dont you tear your self away from your putter long enough to actually try this in the real world . its a really simple mod that is reversable! Takes about 10 minutes
If you dont like it , just pluck it off the pole piece.I for 1, am glad there are still people that actually build things and try them out and find what happenes and why, instead of just saying it wont work based on some sim. Right ! Bumble bees cant fly either!
Regards - Status
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