I don't know for sure, that's why I'm asking the experts. But, I have heard a theory that says, that the back woofers are out of phase and make the front woofers see tha baffle as twice the actual size, and the lowers the requirement for eq'ing the low end.
But I don't know if that's a fact.
But I don't know if that's a fact.
I can give you a part of the answer :
"if" the woofers are electrically wired in phase ( i.e. acoustically out of phase, then creating either a compression or a depression in the central cavity), this particular set up has a name :
Linear Quadrupole. It has also absolutely no interest for woofers as the radiation is already omni and as this behaves as a second order high pass that will be added to the dipole roll off. It means that grossly this would be a 4th order 200 Hz high pass.
After this deduction, we can be sure that as said Audiodidakt, they are acoustically in phase. This behaves more like an ordinary dipole, but I dunno if there is some advantage, except of cosmetic or commercial order.
"if" the woofers are electrically wired in phase ( i.e. acoustically out of phase, then creating either a compression or a depression in the central cavity), this particular set up has a name :
Linear Quadrupole. It has also absolutely no interest for woofers as the radiation is already omni and as this behaves as a second order high pass that will be added to the dipole roll off. It means that grossly this would be a 4th order 200 Hz high pass.
After this deduction, we can be sure that as said Audiodidakt, they are acoustically in phase. This behaves more like an ordinary dipole, but I dunno if there is some advantage, except of cosmetic or commercial order.
My guess would be lowered harmonic distortion like described in Linkwitz's W-frame.
You may get better response by using monopoles out of phase like here:
DP_woofer_room
You may get better response by using monopoles out of phase like here:
DP_woofer_room
I would have asked Emerald Physics in the first place, if I had questions about their products
But anyway - if Audiodidakt is right, then "cuibono" featured a comparable alignment in his violet open baffle project. Its supposed merits were discussed in a thread I can't find any longer. It was found that there are no advantages at all compared to a single baffle.
Rudolf
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Emerald Physics don't answer back.
I have two ideas at the moment.
1: Think of a quarter circle. Here I will have 4 woofers in OB, and the Mark Audio fullrange on top (little forward tilted as in Carlsson) -
I will cross over around 200 Hz, depending on the Mark Audio drivers ability to go that low in OB.
2: A cube like the RAAL, Woofers on side and OB opening in front. Mark Audio CHR70 on top (again with a little forward tilt)
I will finish some google sketchup drawings that I will post toonight
I have two ideas at the moment.
1: Think of a quarter circle. Here I will have 4 woofers in OB, and the Mark Audio fullrange on top (little forward tilted as in Carlsson) -
I will cross over around 200 Hz, depending on the Mark Audio drivers ability to go that low in OB.
2: A cube like the RAAL, Woofers on side and OB opening in front. Mark Audio CHR70 on top (again with a little forward tilt)
I will finish some google sketchup drawings that I will post toonight
Member
Joined 2009
Cardioid bass is said to sound better than dipole in enclosed spaces. There's lots of good information on John K's web site. It should be easy to pull off with quad 10"s in an open U-Frame.
As for the Mark Audio unit I would stay away from dispersion lenses unless you have access to sophisticated modelling software and are willing to go through multiple iterations. It should work fine either open or boxed as long as you have good transition of the dispersion pattern at the crossover.
The biggest problem in your implementation is no doubt the room layout. Wide dispersion speakers sound acceptable off-axis but the optimal listening position is in the sweet spot. This is because of the nature of stereo recording, not the matter of delivery. You might find yourself sitting mostly on the floor rather than on the couch. Also wide dispersion speakers benefit from being placed at equal distance to the side walls. You might encounter strange effects if you have a wall on one side and an open door on the other.
As for the Mark Audio unit I would stay away from dispersion lenses unless you have access to sophisticated modelling software and are willing to go through multiple iterations. It should work fine either open or boxed as long as you have good transition of the dispersion pattern at the crossover.
The biggest problem in your implementation is no doubt the room layout. Wide dispersion speakers sound acceptable off-axis but the optimal listening position is in the sweet spot. This is because of the nature of stereo recording, not the matter of delivery. You might find yourself sitting mostly on the floor rather than on the couch. Also wide dispersion speakers benefit from being placed at equal distance to the side walls. You might encounter strange effects if you have a wall on one side and an open door on the other.
Member
Joined 2009
Dipole speakers need at least 3 ft. clearance from any walls or there is a complex psycho-acoustic effect that is a bummer. With just woofers operating below 200 HZ, you could argue that a bit either way.
In the bigger picture though, bass usually gets damaged by room acoustics more than any other frequency. At higher frequencies, room reflections cause cancellations at the frequency where the reflection is delayed by a half wavelength, AND all the integral multiples of that frequency (comb filter effect). But due to the usually huge number of reflections in the room, where in frequency one path creates cancellations, the energy from the other paths largely fills those cancellations in (law of probability). At frequencies below 200HZ, there may only be two or three significant reflections in a typical living room, because of the size of the wavelength (roughly 6 - 45 ft.), so the fill in effect is less likely to be good enough.
Linkwitz feels that OB dipole woofers sound better because they stimulate room modes less, due to their directivity. While that may be true enough in some rooms, especially larger rooms, I take a different approach. I put long throw 12 inch drivers in closed boxes, slightly overdamped, and then force them to be flat to 20HZ at the listening position using active electronic EQ. That's the starting point. That can give you great bass in a few locations in the room, but not very good everywhere. The effect of room boundary reflections is complex, and different for each room. By having multiple woofer cubes in various locations, it's like you're adding more room reflections, that can fill in the cancellation effects of a single woofer or two. I'd like to have two on the floor not too far from the above 200HZ "satalite speakers", and one or two more up high or just off to the side (whatever's practical), such that they will have a room acoustics interaction that is significantly different than the first two woofers have. Some people call these additional woofers "flanking woofers". It's all about working with the acoustics of the room.
The thing about OB dipole woofers is that they get physically huge if you want to have them go down to 20HZ (and you do). You need a huge amount of cone area and power. the Linkwitz Orion speaker is superb sounding to my ear in the midrange and treble. The bass not so much. There's not much energy below about 50HZ. He's got plenty of power, but only two 10 inch drivers per side. One 10 inch per side in a closed box, near a wall and floor would probably give better bass in most rooms, in my opinion. Above 200HZ, I'm actually a big fan of OB dipoles, and have designed and built some real nice ones.
In the bigger picture though, bass usually gets damaged by room acoustics more than any other frequency. At higher frequencies, room reflections cause cancellations at the frequency where the reflection is delayed by a half wavelength, AND all the integral multiples of that frequency (comb filter effect). But due to the usually huge number of reflections in the room, where in frequency one path creates cancellations, the energy from the other paths largely fills those cancellations in (law of probability). At frequencies below 200HZ, there may only be two or three significant reflections in a typical living room, because of the size of the wavelength (roughly 6 - 45 ft.), so the fill in effect is less likely to be good enough.
Linkwitz feels that OB dipole woofers sound better because they stimulate room modes less, due to their directivity. While that may be true enough in some rooms, especially larger rooms, I take a different approach. I put long throw 12 inch drivers in closed boxes, slightly overdamped, and then force them to be flat to 20HZ at the listening position using active electronic EQ. That's the starting point. That can give you great bass in a few locations in the room, but not very good everywhere. The effect of room boundary reflections is complex, and different for each room. By having multiple woofer cubes in various locations, it's like you're adding more room reflections, that can fill in the cancellation effects of a single woofer or two. I'd like to have two on the floor not too far from the above 200HZ "satalite speakers", and one or two more up high or just off to the side (whatever's practical), such that they will have a room acoustics interaction that is significantly different than the first two woofers have. Some people call these additional woofers "flanking woofers". It's all about working with the acoustics of the room.
The thing about OB dipole woofers is that they get physically huge if you want to have them go down to 20HZ (and you do). You need a huge amount of cone area and power. the Linkwitz Orion speaker is superb sounding to my ear in the midrange and treble. The bass not so much. There's not much energy below about 50HZ. He's got plenty of power, but only two 10 inch drivers per side. One 10 inch per side in a closed box, near a wall and floor would probably give better bass in most rooms, in my opinion. Above 200HZ, I'm actually a big fan of OB dipoles, and have designed and built some real nice ones.
Not really. I'm not a fan of having both music and TV on same speakers. Sometimes the kids are watching TV and I listen to music at the same time.
My stereo is a media center, and TC is also connected to a mediacenter. I have tried to combine, buts its not for me.
The woofer I'd try next would be two 12 inch Peerless XLS on opposite sides of a cube shaped cabinet, with a divider inside, slightly over-damped (cab internal volume slightly less than theory says is right), wired so both cones push out at the same time. This way, any shaking of the cabinet at low frequencies will mechanically cancel out, and less energy lost. I'd then use active EQ to force it to be flat to 20 HZ at the listening position (typically that would mean about 15dB boost at 20 HZ relative to 100HZ, and I wouldn't take woofers above 100HZ. I'd use an active crossover with a 4 pole cutoff rate to split it away from the "satalites" (higher frequency speakers).
I have been playing with my current speakers. Up-firing sub and 4" Tang bands. I have taken the TB's off the wall and laying on top of the subs, pointing directly to the ceiling, and right up against the back wall. It's actually not that different, it's not that you think this is a whole new concept. BUT, the sound is way more uniform in the room, and I haven't noticed any lack of dynamic or slam from maybee 500 Hz and up. Lower frequencies seem to lack som punch, but I hope I can get this area to work better with the new build.
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