Hi all , just wondering if anyone has knowledge on this. A stacked set of dipole woofers facing the listener without the front or back blank so that the woofer cones are visible. Closest pic i can find is linked ( I hope.)
Kind of like legacy audio but with 4 or 6 woofers per side.
I have seen them in vertical towers like the sureal sound 5th row speaker, page 85 of the ultime open baffle gallery, but never horizontal.
Kind of like legacy audio but with 4 or 6 woofers per side.
I have seen them in vertical towers like the sureal sound 5th row speaker, page 85 of the ultime open baffle gallery, but never horizontal.
Attachments
You sure it's not an incomplete variation of the same thing you are describing in the vertical array examples? Vertical or horizontal doesn't really matter if it's a subwoofer.
You normally see alternating plates at the front and back between woofers, and a solid top plate matching the bottom plate of your image.
A couple examples of typical stacked arrays:
Alternate drivers 3
Gainphile: Dipole Bass Array
If you're referring to the Legacy Whisper, that one is open to the front, back, and sides. They say they are are trying to control dispersion with that layout.
Project Whisper | An Engineers Perspective | Legacy Audio - Building the World's Finest Audio Systems
"The low frequency drivers operate in phase with each other and combine acoustically as a pair of figure- of-eights, one behind the other. The result: a compound null formed at the sides of the enclosure, which minimizes resonances and room reflections."
You normally see alternating plates at the front and back between woofers, and a solid top plate matching the bottom plate of your image.
A couple examples of typical stacked arrays:
Alternate drivers 3
Gainphile: Dipole Bass Array
If you're referring to the Legacy Whisper, that one is open to the front, back, and sides. They say they are are trying to control dispersion with that layout.
Project Whisper | An Engineers Perspective | Legacy Audio - Building the World's Finest Audio Systems
"The low frequency drivers operate in phase with each other and combine acoustically as a pair of figure- of-eights, one behind the other. The result: a compound null formed at the sides of the enclosure, which minimizes resonances and room reflections."
Thanks for answering mattstat,
The image was from a PE build thread and as you suspected incomplete. The end product was vertical. The image was the only thing i could find similar to i was thinking of building.
I have a massive gap in my knowledge compared to others on this site and was wondering if there was any advantage to this idea of stacking drivers behind each other for lower mid bass reproduction in IB or dipole configuration.
I have 4 18s i was going to clamshell out of phase for lowest frquencys and position where best in room separate to main towers.
This will be my first build and i am planning active 4 way IB but willing to hybrid any part for best result.
My room is quit large 85m2 so im not shy about size of speakers.
Another question is if stacking 10s or 12s in an equal number is beneficial, would different types of drivers behind each other be bad? Eg ae drivers first followed by cheeper mcm.
Different sizes behind each other same or different brand be bad eg 10,12,12,10.?
Would rear firing the last driver in the stack be beneficial?
Please anyone who knows answers to any or all questions feel free to school me.
The image was from a PE build thread and as you suspected incomplete. The end product was vertical. The image was the only thing i could find similar to i was thinking of building.
I have a massive gap in my knowledge compared to others on this site and was wondering if there was any advantage to this idea of stacking drivers behind each other for lower mid bass reproduction in IB or dipole configuration.
I have 4 18s i was going to clamshell out of phase for lowest frquencys and position where best in room separate to main towers.
This will be my first build and i am planning active 4 way IB but willing to hybrid any part for best result.
My room is quit large 85m2 so im not shy about size of speakers.
Another question is if stacking 10s or 12s in an equal number is beneficial, would different types of drivers behind each other be bad? Eg ae drivers first followed by cheeper mcm.
Different sizes behind each other same or different brand be bad eg 10,12,12,10.?
Would rear firing the last driver in the stack be beneficial?
Please anyone who knows answers to any or all questions feel free to school me.
For midbass, you'll need to watch cavity resonances, depending on how far up in frequency you are going and how your baffle is designed. Some info here:
http://www.linkwitzlab.com/frontiers.htm#L
The "spl_max1" spreadsheet on this page is worth messing around with also. It gives you some idea of the volume displacement required to make X output at Y frequency. These are just basic numbers though, not baffle modeling. It's an easy way to see rough numbers.
http://www.linkwitzlab.com/publications.htm
If you don't need extra drivers and a complex baffle to give the SPL you want, I wouldn't use them, especially at higher frequencies. A flat baffle is easiest to implement, but typically gets large for low bass frequencies and the number of drivers required.
In addition to allowing for a compact array, drivers are stacked and driven out of phase to decrease distortion inherent in the driver. If you stack different sizes or different models, you'll lose that benefit.
http://www.linkwitzlab.com/frontiers.htm#L
The "spl_max1" spreadsheet on this page is worth messing around with also. It gives you some idea of the volume displacement required to make X output at Y frequency. These are just basic numbers though, not baffle modeling. It's an easy way to see rough numbers.
http://www.linkwitzlab.com/publications.htm
If you don't need extra drivers and a complex baffle to give the SPL you want, I wouldn't use them, especially at higher frequencies. A flat baffle is easiest to implement, but typically gets large for low bass frequencies and the number of drivers required.
In addition to allowing for a compact array, drivers are stacked and driven out of phase to decrease distortion inherent in the driver. If you stack different sizes or different models, you'll lose that benefit.
Stacked dipole bass
Yes, why not.
At low frequencies, no problem, but the 1/2 & 1/4 wavelength lobing rules stay the same depending on driver vertical spacing.
There is a solution to lobing at higher frequencies and this is to triple stack...not double stack. Attenuate the top and bottom cabinet by 3-6dB each and apply a delay between around .2ms to .6ms to the middle cabinet. 15" drivers with 1.5ft vertical centres (1.5ft baffles) may be used up to a max of around 600Hz with this method.
You have created a constant beamwidth design!
The smaller delay will provide narrower vertical dispersion...so now by adjusting the delay you can control the vertical pattern. Brilliant!!
Yes, why not.
At low frequencies, no problem, but the 1/2 & 1/4 wavelength lobing rules stay the same depending on driver vertical spacing.
There is a solution to lobing at higher frequencies and this is to triple stack...not double stack. Attenuate the top and bottom cabinet by 3-6dB each and apply a delay between around .2ms to .6ms to the middle cabinet. 15" drivers with 1.5ft vertical centres (1.5ft baffles) may be used up to a max of around 600Hz with this method.
You have created a constant beamwidth design!
The smaller delay will provide narrower vertical dispersion...so now by adjusting the delay you can control the vertical pattern. Brilliant!!
Thanks soundright,
Now we are getting some where, would i therefore need separate dsp control over every woofer in horizontal stack to give the appropriate time delay as you suggested?
I was looking at various ohm resistors for shading drivers elsewhere and presume they would work to knock 3 or 6 db in the stack of subs, but is there a passive way to tjme delay?
Also any thoughts on mixing bass driver in the stacked array?
Now we are getting some where, would i therefore need separate dsp control over every woofer in horizontal stack to give the appropriate time delay as you suggested?
I was looking at various ohm resistors for shading drivers elsewhere and presume they would work to knock 3 or 6 db in the stack of subs, but is there a passive way to tjme delay?
Also any thoughts on mixing bass driver in the stacked array?
There are two ways to achieve this. One is dsp, but use it on all channels because you need to keep the latency the same so the small delay to the middle cabinet is relative to the others.
The other method is to offset the middle cabinet drivers so they are physically displaced behind the others. Around 6" will provide an equivalent delay but not adjustable of course. L pad resistors may be used to reduce the output of the other cabinets to provide the -3 to 6dB attenuation...
This would enable you to use an analogue active crossover instead of a digital solution? Make sure of course the amps are seeing a sensible impedance! Top and bottom cabinets could be series/parallel connected to match the sensitivity of the middle cabinet before they are attenuated?
Hope that all makes sense!!
The other method is to offset the middle cabinet drivers so they are physically displaced behind the others. Around 6" will provide an equivalent delay but not adjustable of course. L pad resistors may be used to reduce the output of the other cabinets to provide the -3 to 6dB attenuation...
This would enable you to use an analogue active crossover instead of a digital solution? Make sure of course the amps are seeing a sensible impedance! Top and bottom cabinets could be series/parallel connected to match the sensitivity of the middle cabinet before they are attenuated?
Hope that all makes sense!!
Ok thanks,
so just a few questions if for example i have 5 12" woffers stacked as close as possible so that at max xmas they dont hit dustcap to magnet, on woofer #3 in the stack i place an extra 6" of space between it and woofer #4 i would be giving it a passive time delay?
Would i then go back to minimum spacing #4,#5 ?
Would it be best to put each woofer on a movable stand to be able to adjust their distances on the fly?
so just a few questions if for example i have 5 12" woffers stacked as close as possible so that at max xmas they dont hit dustcap to magnet, on woofer #3 in the stack i place an extra 6" of space between it and woofer #4 i would be giving it a passive time delay?
Would i then go back to minimum spacing #4,#5 ?
Would it be best to put each woofer on a movable stand to be able to adjust their distances on the fly?
I'm a little confused how you are trying to configure these. Sounds a little over complicated!
Firstly, I would use 6 drivers in 3 pairs, in "cabinets" with angled baffles (horizontal)..or one large baffle for all 6. Problem with that is making the baffle non resonant...but baffle size will determine how much eq you need at low frequency. The vertical spacing should be kept to the minimum the drivers and cabinets will allow. For 12" drivers each "cabinet" need only be 14/15" in height which of course will also be the centre to centre driver spacing. Baffle area can be increased by increasing the horizontal dimension but around 28" for 2 x 12 would make sense. Your effective baffle area then will be something in excess of 45" x 28" for a triple stack of angled pairs. The stack will start to roll at 6dB/octave from roughly 125/150 Hz. Of course room loading will effect this as well but you could still be looking at around a maximum of 12dB of boost (at 6dB/octave) at around 30Hz which is why power handling and driver Xmax are so relevant...
At least with an open back/front cabinet you can both angle the two baffles (30deg works well) and offset the baffles on the middle cab a distance behind the top/bottom cabs to provide the small "run time" delay.
With the flat baffle you would have to apply a delay. This would also be the case with 3 identical cabs.
I'm going to use the word..Behringer!! There...I've said it. The Ultracurve has a delay function on one audio output. You could use 2 x Ultracurves, one per channel which would provide both simple to apply eq and accurate adjustable delay. An alternative is any 2 x 3/4 channel dsp lms but the Ultracurve has a simple gui and could be used in an otherwise analogue system just dedicated to the dipole bass stacks as an equaliser and delay.
I have 3 Ultracurves and they have worked faultlessly, in racks, for years. Some may ascribe a slightly thin and untidy hf performance from them on their analogue outputs but this really is not an issue at bass frequencies ...
Hope this helps.
Firstly, I would use 6 drivers in 3 pairs, in "cabinets" with angled baffles (horizontal)..or one large baffle for all 6. Problem with that is making the baffle non resonant...but baffle size will determine how much eq you need at low frequency. The vertical spacing should be kept to the minimum the drivers and cabinets will allow. For 12" drivers each "cabinet" need only be 14/15" in height which of course will also be the centre to centre driver spacing. Baffle area can be increased by increasing the horizontal dimension but around 28" for 2 x 12 would make sense. Your effective baffle area then will be something in excess of 45" x 28" for a triple stack of angled pairs. The stack will start to roll at 6dB/octave from roughly 125/150 Hz. Of course room loading will effect this as well but you could still be looking at around a maximum of 12dB of boost (at 6dB/octave) at around 30Hz which is why power handling and driver Xmax are so relevant...
At least with an open back/front cabinet you can both angle the two baffles (30deg works well) and offset the baffles on the middle cab a distance behind the top/bottom cabs to provide the small "run time" delay.
With the flat baffle you would have to apply a delay. This would also be the case with 3 identical cabs.
I'm going to use the word..Behringer!! There...I've said it. The Ultracurve has a delay function on one audio output. You could use 2 x Ultracurves, one per channel which would provide both simple to apply eq and accurate adjustable delay. An alternative is any 2 x 3/4 channel dsp lms but the Ultracurve has a simple gui and could be used in an otherwise analogue system just dedicated to the dipole bass stacks as an equaliser and delay.
I have 3 Ultracurves and they have worked faultlessly, in racks, for years. Some may ascribe a slightly thin and untidy hf performance from them on their analogue outputs but this really is not an issue at bass frequencies ...
Hope this helps.
You won't get any bass out of that configuration no matter how many woofers you have.
You have to create a decent acoustical distance between driver front and back radiation so you don't get complete cancellation.
Dave.
Horizontal or vertical makes no difference. The vertical stack in the photo I posted could just as easily be flipped onto its side.
I suggest to start with the basics for understanding this. The simplest form of a force-cancelling dipole woofer is the Linkwitz Phoenix scheme. (Note the 19" distance that separates front and back radiation.)
Dipole Woofer
Dave.
No Bass
Actually, you might! Check out this guys evolution in naked dipole woofers.
Trans-Fi Audio - OB Speakers
Others have had similar results, though I think large speakers, i.e. 15-18" are the norm.
You won't get any bass out of that configuration no matter how many woofers you have.
You have to create a decent acoustical distance between driver front and back radiation so you don't get complete cancellation.
Dave.
Actually, you might! Check out this guys evolution in naked dipole woofers.
Trans-Fi Audio - OB Speakers
Others have had similar results, though I think large speakers, i.e. 15-18" are the norm.
Digicol thanks, i have had discussed that exact system with vic, and have been planning my system for a while now
.
I was hoping to stand on the shoulders of gaints and not have to start from the beginning.
I wanted maximum lower mid bass and was wanting expert help to stack maximum woffers in minimum space as adison suggested.
Anyway i guess i will just grab 4 12" and 4 10" woffers build something that I can move around and stack at diffrent lengths, combinations and try shading and time alignment and rear firing clamshelling, ext, could be fun .
Thanks to trans fi inspiration i have already purchased 4 goldwood 18s for 20 to 80hrtz they will be clamshell out of phase and be separate to main towers.
Targeted frequency for woofers yet to be purchased is 80 to 1000hrtz. Give or take a little.
Had a look at golomb ruler yesterday, and think that could be interesting to incorporate infinite baffle fullrange sparse array to a stack of dipole woofers backed up by 4 18s..
Anyone know how it could work not why they think it wont?
.
I was hoping to stand on the shoulders of gaints and not have to start from the beginning.
I wanted maximum lower mid bass and was wanting expert help to stack maximum woffers in minimum space as adison suggested.
Anyway i guess i will just grab 4 12" and 4 10" woffers build something that I can move around and stack at diffrent lengths, combinations and try shading and time alignment and rear firing clamshelling, ext, could be fun .
Thanks to trans fi inspiration i have already purchased 4 goldwood 18s for 20 to 80hrtz they will be clamshell out of phase and be separate to main towers.
Targeted frequency for woofers yet to be purchased is 80 to 1000hrtz. Give or take a little.
Had a look at golomb ruler yesterday, and think that could be interesting to incorporate infinite baffle fullrange sparse array to a stack of dipole woofers backed up by 4 18s..
Anyone know how it could work not why they think it wont?
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.