StigErik, what is the dipole peak of a given driver? Do you need to model it, or can it be derived through using some combination of TS parameters? I am planning some open baffles, and am trying to figure out how the dipole peak variable can be addressed in my design. I understand that we want to crossover at this point or have it outside of the band we are utilizing. Is that correct?
I'm not Stig but I've been playing with dipoles for a while now. The peak is determined by the baffle the driver is on (or the driver itself if no baffle). I usually figure on good dipole response up to the freq dictated by the baffle (or driver) width. A 10" wide baffle works out to 1350hz (speed of sound is 13500 in/sec, so 13500/10=1350). In practice the peak comes out lower than that. This is roughly where the driver begins to "beam" and dispersion narrows considerably compared to below the dipole peak.
The Edge baffle simulator is good for simulating baffles: Tolvan Data
It's desirable to use a dipole driver below the peak if constant directivity is one of the your goals for speaker design. There are many open baffle speakers out there that don't follow this and they make people happy too
The Edge baffle simulator is good for simulating baffles: Tolvan Data
It's desirable to use a dipole driver below the peak if constant directivity is one of the your goals for speaker design. There are many open baffle speakers out there that don't follow this and they make people happy too
I sure resurrected this thread which had intense arguments and posters included Dr. Geddes and JohnK of Nao. No real conclusion at the end..which is unexpected as the dipole bass was "supposed" to win on the measurements too.
There can't be one "real" conclusion. It depends too much on the individual room situation. There are room proportions and listening situations where "monopole" will be the clear winner and others, where "dipole" will be the best solution. We shouldn't think of "monopole against dipole" bass concepts, but simply of distributed point sources with whatever polarities or positions that suite the room best.I sure resurrected this thread which had intense arguments and posters included Dr. Geddes and JohnK of Nao. No real conclusion at the end..which is unexpected as the dipole bass was "supposed" to win on the measurements too.
Best of both worlds...
From my own experiments with dipole and monopole bass, and works of SL and MJK, postings by Dr. Geddes and many others, I guess that it is a combination of both dipole and monopole that provides the most bang for the buck, in every room.
Distributed multiple monopole sources for the lowest frequencies from
10-40hz does not seem to have any drawback compared to dipoles, sound quality wise. However using dipoles in this frequency range needs huge space, equalisation, amplification and resultant expense.
From 40-200 hz, a MJK style H-frame with large high Qtc woofers (like the inexpensive eminence alpha 15), needs no bass equalisation and definitively 'sounds' better to my ears than every monopole I have tried, sealed or ported. Having dipole bass in this range also allows for a seamless transition to a dipole arrangement of drivers for the range above 200Hz.
Higher than 200 Hz a dipole on the thinnest baffle (or no baffle) with a small amount of low end bost, like StigErik seems to be the obvious choice for most.
In huge rooms dipole bass "may" have some benefit as low as 30 hz and in very small rooms, dipoles may loose their radiation benefit a lot higher than 40Hz compared to monopoles.
So at the end, a dipole above 40Hz and monopole multiple subs below 30-40Hz seems to be best of both worlds IMHO.
From my own experiments with dipole and monopole bass, and works of SL and MJK, postings by Dr. Geddes and many others, I guess that it is a combination of both dipole and monopole that provides the most bang for the buck, in every room.
Distributed multiple monopole sources for the lowest frequencies from
10-40hz does not seem to have any drawback compared to dipoles, sound quality wise. However using dipoles in this frequency range needs huge space, equalisation, amplification and resultant expense.
From 40-200 hz, a MJK style H-frame with large high Qtc woofers (like the inexpensive eminence alpha 15), needs no bass equalisation and definitively 'sounds' better to my ears than every monopole I have tried, sealed or ported. Having dipole bass in this range also allows for a seamless transition to a dipole arrangement of drivers for the range above 200Hz.
Higher than 200 Hz a dipole on the thinnest baffle (or no baffle) with a small amount of low end bost, like StigErik seems to be the obvious choice for most.
In huge rooms dipole bass "may" have some benefit as low as 30 hz and in very small rooms, dipoles may loose their radiation benefit a lot higher than 40Hz compared to monopoles.
So at the end, a dipole above 40Hz and monopole multiple subs below 30-40Hz seems to be best of both worlds IMHO.
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That is exactly what I'm saying too.
But you go on with too much thinking in boxes and baffles, imho. If you feed a monopole next to your listening position and another monopole at 3.4 m distance from you with the same sound signal, they will work as a perfect dipole at 50 Hz for you. At another position, distance and frequncy they will act as a cardioid for you.
One could say that the optimal placement of some distributed monopole bass sources in a room provides the best ratio of omnipole, dipole and cardioid behaviour - hopefully leading to the best sound.
That is exactly what I'm saying too.
If you feed a monopole next to your listening position and another monopole at 3.4 m distance from you with the same sound signal, they will work as a perfect dipole at 50 Hz for you. At another position, distance and frequncy they will act as a cardioid for you.
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You are right
Never thought multiple monopoles with different phases and delays will be like a combination of dipoles, cardioids..
very similar to the DBA concept actually !!
As per Dr Geddes and Rudolf, you may try to asymmetrically distribute the 4 monopole subs in 4 sides of the room. Or how about the DBA concept as you already have 4 monopole bass units.
I don't have the monopole sub's any longer, so I really cant do that.
I have however four dipole woofer towers that are distributed to some degree - two centered on the front wall, and one on each side wall.
This distribution has virtually no effect on the frequency response in the listening position. The response from the two center woofers is the same as the side woofers, only with slightly less level @ 20 Hz from the side woofers. This lack of difference in response is possibly because they are dipoles, and I expect it would look very different with monopoles. The dipole's frequency response is not affected by the fundamental room modes in the height and width of the room, although the modes are triggered to some degree.
I have had a lot on monopole woofers in my room, and they all required a lot of EQ to obtain a flat response. The dipoles don't.
Subjectively I have no doubt that dipoles sound better in the important bass range from say 40 to 150 Hz. To my ears, and in my room. Purely subjective of course, but I'm not alone with this experience. Other listeners have said that the dipoles produce a totally different type of sound than monopoles, and I agree with that.
That being said - I do have a distributed monopole woofer setup (eight 10") in my home theater that works pretty decent. They can shake the whole room on movie soundtracks, a thing which dipoles simply can't do.
I have however four dipole woofer towers that are distributed to some degree - two centered on the front wall, and one on each side wall.
This distribution has virtually no effect on the frequency response in the listening position. The response from the two center woofers is the same as the side woofers, only with slightly less level @ 20 Hz from the side woofers. This lack of difference in response is possibly because they are dipoles, and I expect it would look very different with monopoles. The dipole's frequency response is not affected by the fundamental room modes in the height and width of the room, although the modes are triggered to some degree.
I have had a lot on monopole woofers in my room, and they all required a lot of EQ to obtain a flat response. The dipoles don't.
Subjectively I have no doubt that dipoles sound better in the important bass range from say 40 to 150 Hz. To my ears, and in my room. Purely subjective of course, but I'm not alone with this experience. Other listeners have said that the dipoles produce a totally different type of sound than monopoles, and I agree with that.
That being said - I do have a distributed monopole woofer setup (eight 10") in my home theater that works pretty decent. They can shake the whole room on movie soundtracks, a thing which dipoles simply can't do.
Thanks for your impressions Erik. Too bad you did away with the sealed subs
Completely agree that dipoles sound very different, which for most folks including me is 'better" than monopoles. More freedom of placement than monopoles is a great advantage too....just aim them at the listening spot and stay far from the wall behind
Dont know yet how to produce bass as clean as a dipole that can also shake the house if needed ??!!
BTW, how would you compare your HT setup with distributed monopoles, if used for music, compared to your dipole setup. Thanks.
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I don't think its really possible to make a dipole that can shake the whole house. I have a ridiculous amount of cone area in my dipole woofers, and they are still unable to really make things rattle, although I can measure 120 dB @ 25 Hz. Dipoles move in air in a different way than monopoles.
The distributed monopole setup in my HT plays fairly clean bass, but the definition and dynamics is not anywhere close to what the dipoles can do.
The distributed monopole setup in my HT plays fairly clean bass, but the definition and dynamics is not anywhere close to what the dipoles can do.
Stig
What you using for high/tweets now i know you are using BG for Dipole...but what is used for the highs...RAALS?
V
Hi Erik, does the RD75 actually go as low as 150 hz flatly in a no baffle loading scheme. are there any comb filtering issues ? How do you feel a line array of 25 3" FR drivers like the inexpensive vifa tc9 co
pare to the RD75
A waveguide/horn is required to correctly mate a 12" midbass to the TPL150H HEIL.
Measured data for the TPL150H (horn) shows usability starting at about 1200Hz.
The polar response of a 12" speaker shows significant narrowing(beaming) starting around 600Hz (13550 in/sec) /(11"diameter*2) and this dispersion pattern approximates about 70-80 degrees at 1200Hz. The TPL150H has an 80 degree horizontal beamwidth and 30 degree vertical beamwidth. If the TPL150H is physically butted right above a 12" speaker with acoustic LR4 1200Hz Xover a smooth controlled directivity polar response is possible.
The woofer cone shape will effect the polar response, so each 12" speaker polars can be slightly different. The horn's extra depth will also closer approach the time delay of the woofer's voice coil.
Not really, but if I remember correctly its about 6 dB down at 150 Hz, measured at 1 meter. There is no comb filter issues with the RD75's own response. Now remember that the LF response of a line source decreases with distance, so at greater distance than 1 meter there will be a slight LF roll-off starting at 6-700 Hz. This can be compensated with EQ, or by using a fairly small baffle.
A line of 3" FR drivers will have severe comb filtering, so I would not even consider doing that.
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