Different approaches to the same effect. The dipole roll-off has to be countered somehow. If you use a low Q driver, you must equalize it electrically. Or you can use a high Q driver and use the resonance peak as an approximate EQ.
Siegfried Linkwitz on his site gives very comprehensive accounts of his (different) approach:
1) theory of dipole roll off, derived mathematically
2) measured response on flat circular baffle with no wings
3) introduction of wings as an engineering compromise to achieve smaller size
4) measured response of winged baffles
5) discussion of probable causes of measured responses different from theory: a- 1/4 wave resonance of winged rear of baffles; b- low pass behaviour of rear of driver; c- for woofers, importantly, 6 dB room gain which he derived empirically.
Sooooo... given these effects, quite possible that the combined effect of "unintentional EQ" through high Q driver resonance peak PLUS 6 dB raised response due to full/half space transition 200 to 100 Hz, will in effect and for some driver/baffle combinations, lead to a quite flat response quite much below the calculated start of rolloff. After all the calculated rolloff assumes flat circular baffle, ideal opposite-phase rear wave, AND its x-axis is acoustical output - not signal input into an unknown Q driver. Using a high Q driver raises acoustical output vs signal input and therefore is what Linkwitz calls "a crude EQ".
Linkwitz approaches the EQ/baffle question differently: he first tries to minimize driver Q, baffle wing resonance and room gain effects through preliminary EQ to get a "clean slate" closer to theory. Ideall what remains after that is the "pure" (more manageable) dipole rolloff transfer functions which he then equalizes.
Both approaches (using Q and baffle as EQ, vs. using electrical EQ on previously "idealized" driver/baffle combination) can lead to good results. I wonder however, whether using a high Q would not lead to muddy, undefined bass - after all you're using an underdamped resonance to get your SPL's rather than defined control by the EQ/amp.
Siegfried Linkwitz on his site gives very comprehensive accounts of his (different) approach:
1) theory of dipole roll off, derived mathematically
2) measured response on flat circular baffle with no wings
3) introduction of wings as an engineering compromise to achieve smaller size
4) measured response of winged baffles
5) discussion of probable causes of measured responses different from theory: a- 1/4 wave resonance of winged rear of baffles; b- low pass behaviour of rear of driver; c- for woofers, importantly, 6 dB room gain which he derived empirically.
Sooooo... given these effects, quite possible that the combined effect of "unintentional EQ" through high Q driver resonance peak PLUS 6 dB raised response due to full/half space transition 200 to 100 Hz, will in effect and for some driver/baffle combinations, lead to a quite flat response quite much below the calculated start of rolloff. After all the calculated rolloff assumes flat circular baffle, ideal opposite-phase rear wave, AND its x-axis is acoustical output - not signal input into an unknown Q driver. Using a high Q driver raises acoustical output vs signal input and therefore is what Linkwitz calls "a crude EQ".
Linkwitz approaches the EQ/baffle question differently: he first tries to minimize driver Q, baffle wing resonance and room gain effects through preliminary EQ to get a "clean slate" closer to theory. Ideall what remains after that is the "pure" (more manageable) dipole rolloff transfer functions which he then equalizes.
Both approaches (using Q and baffle as EQ, vs. using electrical EQ on previously "idealized" driver/baffle combination) can lead to good results. I wonder however, whether using a high Q would not lead to muddy, undefined bass - after all you're using an underdamped resonance to get your SPL's rather than defined control by the EQ/amp.
Konnichiwa,
Well, if you use REALLY HIGH Q Drivers (like the Qt >3 ones Bob Carver used on his "Amazing" Speaker), yes, then this is of concern.
On the other hand Sealed boxes with a Q (Box & Driver) of 0.5 to 1 are quite common and sound pretty good, without boomy bass, so why should it be any different just because we suddenly use a Dipole? In the end, in other (closed/vented/horn) systems the acoustic load behind the driver raises the system Q to something generating a reasonably flat response, for a Dipole we have no rear load, so we need to start with a driver that has a higher Q.
Sayonara
MBK said:
Well, if you use REALLY HIGH Q Drivers (like the Qt >3 ones Bob Carver used on his "Amazing" Speaker), yes, then this is of concern.
On the other hand Sealed boxes with a Q (Box & Driver) of 0.5 to 1 are quite common and sound pretty good, without boomy bass, so why should it be any different just because we suddenly use a Dipole? In the end, in other (closed/vented/horn) systems the acoustic load behind the driver raises the system Q to something generating a reasonably flat response, for a Dipole we have no rear load, so we need to start with a driver that has a higher Q.
Sayonara
I´ve been following this thread and the others containing theories and suggestions about dipoles with much interrest, and i would like to mention my own project. Would perhaps be helpful with a couple of hints to see if im on the right path here. 
I´m stuck between these two options:
1. Orion "clone" using 2 SLS 12" woofers and mangerdriver.
2. Phoenix "clone" with with the SLS woofers in h-frame configuraton and separate manger panels.
I got a paradigm active crossover that will have to due for now. A more suitable filter is planned depending on the outcome of the speakers.
Regards // Mattias S
I´m stuck between these two options:
1. Orion "clone" using 2 SLS 12" woofers and mangerdriver.
2. Phoenix "clone" with with the SLS woofers in h-frame configuraton and separate manger panels.
I got a paradigm active crossover that will have to due for now. A more suitable filter is planned depending on the outcome of the speakers.
Regards // Mattias S
I would try the Mangers in a sealed box with plenty of damping that starts 5-10 cm away from them first. I am perfectly happy with this.
I am not sure it makes sense to have a high frequency dipole, the response just gets too irregular. Besides, the Mangers are not really all that open to the back side, so whatever gets emitted to that side should better not escape.
Regards,
Eric
I am not sure it makes sense to have a high frequency dipole, the response just gets too irregular. Besides, the Mangers are not really all that open to the back side, so whatever gets emitted to that side should better not escape.
Regards,
Eric
Manger make a dipole, and this thread may or may not help.
http://www.madisound.com/cgi-bin/discuss.cgi?read=259901
http://www.madisound.com/cgi-bin/discuss.cgi?read=259901
Guys, Looking for suggestions
I would like to build a dipole w/o equalization and give these guys a shot. I can't afford $300 drivers but could afford $200-$300 for the entire project.
Obviously the drivers would need to be High QT >.5 and I would like to get down to at least 300Hz. I can build a basic crossover, so I guess I am looking for suggestions on what drivers easily available in the US would make a descent speaker.
Thanks...Lee
I would like to build a dipole w/o equalization and give these guys a shot. I can't afford $300 drivers but could afford $200-$300 for the entire project.
Obviously the drivers would need to be High QT >.5 and I would like to get down to at least 300Hz. I can build a basic crossover, so I guess I am looking for suggestions on what drivers easily available in the US would make a descent speaker.
Thanks...Lee
bass
"Apparently, nobody can say why I get such excellent bass response out of my dipoles. Could it be that none of you know?!" --chops
Stop whining (
) and enjoy your music
I have got a pair of el-cheapo highish Q woofers in open waffle - does not go too low, and are not too loud but quality is un-beatable by any box (that I have heard). When I have got some time again
I am going to try better drivers and baffle construction...
"Apparently, nobody can say why I get such excellent bass response out of my dipoles. Could it be that none of you know?!" --chops
Stop whining (
) and enjoy your music I have got a pair of el-cheapo highish Q woofers in open waffle - does not go too low, and are not too loud but quality is un-beatable by any box (that I have heard). When I have got some time again
I am going to try better drivers and baffle construction...Re: Guys, Looking for suggestions
I can't speak as to their subjective quality, but Peerless does seem to have some appropriate woofer/mids, specifically their nomex coned 820378...
Similarly, the Morel MW166, is a nice driver, but twice as expensive.
You can see both at
http://www.madisound.com/
Dunno if you meant that 300hz, or if you meant 30hz(good luck!),
but 300hz is about where the midrange dipoles come in on my Alon IVs, which I dearly love.
Lee,king30 said:
I can't speak as to their subjective quality, but Peerless does seem to have some appropriate woofer/mids, specifically their nomex coned 820378...
Similarly, the Morel MW166, is a nice driver, but twice as expensive.
You can see both at
http://www.madisound.com/
Dunno if you meant that 300hz, or if you meant 30hz(good luck!),
but 300hz is about where the midrange dipoles come in on my Alon IVs, which I dearly love.
. I meant down to at least 50hz.I´ve tried both open and sealed enlosures for my mangers. Both options work quite well.
If i chose a sealed box i wonder what problems might surface combining a monopole for the higher frequenzies with a dipole lower end.
Example of dipole/monopole design: http://www.klubben.net/donald_north_audio.htm
PS. Found a commersial dipole design using mangerdrivers: http://home.loopme.com/tonart/sites/tonart/go.cfm?id=8022&type=text&lang=no&path=6330i6336i8022
Regards // Mattias S
Lee,
Another driver that might meet your needs is the 831510 8" 'Classic' woofer @$29ea and a Qts of .82, at the same madisound.com website. Lower Fs, 37hz, and lower efficiency. I've not used it, but from its response graph, it might require a 3 way implementation....
And lastly, Peerless of India has their S16-NG-08 -
http://www.peerlessaudio.com/products/drivers/classic/main3.asp?pname=5
which looks ideal (GR research sources some of their dirvers OEM from them), but I've no idea where to obtain in the States, or what this specific driver actually sounds like...
Another driver that might meet your needs is the 831510 8" 'Classic' woofer @$29ea and a Qts of .82, at the same madisound.com website. Lower Fs, 37hz, and lower efficiency. I've not used it, but from its response graph, it might require a 3 way implementation....
And lastly, Peerless of India has their S16-NG-08 -
http://www.peerlessaudio.com/products/drivers/classic/main3.asp?pname=5
which looks ideal (GR research sources some of their dirvers OEM from them), but I've no idea where to obtain in the States, or what this specific driver actually sounds like...
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