BiPolar disordered
Hi Planet 10,
The bipolar speaks look VERY interesting. They do appear to solve the baffle step response problem, cancel out bad vibes, give a lot of the advantages of open baffle in a small tower.
As you probably know, the subwoofer guys have tried this back to back aproach and like it a lot, BUT the consensus is that it is better to have one of the speakers with the basket sticking out of the box and the other with it in. This doesn't allow the bracing between the magnets, but is reputed to cancel out some distortions because the coils are in different non-linear parts of their travel at any given time. Of course they are wired out of phase so both cones move out at the same time, so many resonances arestill canceled out. The rear speaker basket sticking out the back would actually look cool to me if one of the cast frame drivers were used.
Some of them are quite pretty
I don't know who to believe or whether it is different for the higher frequencies and less excursion of a full range driver, but would be worth an experiment. Of course on higher frequencies the basket being in the way is bad too (I think this is probably the flaw in my scheme- probably how he shows 'em is better) but the high frequencies coming out the back may not be as important.
I also just read a review in Stereophile of the MBL 11B speaker.
Of course it has those special omnidirectional tweeter and super tweeter, but for midrange they have 2 5" midranges.
One faces left and one faces right, Since they don't cover the higher frequencies, they apparently put out a 360 deg pattern.
This makes me think the the Bipolar will do the same.
In my Basszilla instructions, Dick Olsher says one of the advantages of the open baffle is that it puts more midrange into the room, which actually is needed to get a flatter response.
I believe the Bipolar works just like an open baffle in the upper frequencies, so all indications are that this is a great idea!
The open baffle has the advantage of no box resonances though!
Another thought: you might not need the coax tweeter on the rear speaker.
cool idea
Mark
Hi Planet 10,
The bipolar speaks look VERY interesting. They do appear to solve the baffle step response problem, cancel out bad vibes, give a lot of the advantages of open baffle in a small tower.
As you probably know, the subwoofer guys have tried this back to back aproach and like it a lot, BUT the consensus is that it is better to have one of the speakers with the basket sticking out of the box and the other with it in. This doesn't allow the bracing between the magnets, but is reputed to cancel out some distortions because the coils are in different non-linear parts of their travel at any given time. Of course they are wired out of phase so both cones move out at the same time, so many resonances arestill canceled out. The rear speaker basket sticking out the back would actually look cool to me if one of the cast frame drivers were used.
Some of them are quite pretty
I don't know who to believe or whether it is different for the higher frequencies and less excursion of a full range driver, but would be worth an experiment. Of course on higher frequencies the basket being in the way is bad too (I think this is probably the flaw in my scheme- probably how he shows 'em is better) but the high frequencies coming out the back may not be as important.
I also just read a review in Stereophile of the MBL 11B speaker.
Of course it has those special omnidirectional tweeter and super tweeter, but for midrange they have 2 5" midranges.
One faces left and one faces right, Since they don't cover the higher frequencies, they apparently put out a 360 deg pattern.
This makes me think the the Bipolar will do the same.
In my Basszilla instructions, Dick Olsher says one of the advantages of the open baffle is that it puts more midrange into the room, which actually is needed to get a flatter response.
I believe the Bipolar works just like an open baffle in the upper frequencies, so all indications are that this is a great idea!
The open baffle has the advantage of no box resonances though!
Another thought: you might not need the coax tweeter on the rear speaker.
cool idea
Mark
BiPoles
Check outFig 5.2. The bottom trace is a single woofer, the top trace the bi-pole version. If you think about what happens when you hit baffle-step -- the sound is progressively wraping around the cabinet more & more as the frequency goes down. The same is happening with the back driver but facing the other way -- as the output of the front driver starts to fall off, it is exactly filled in by the bafflestep on the back driver.
The compromise is that the speaker has to be out into the room more (not necessarily a bad thing)
An open baffle is without box, a good push-push driver arrangement transmits much, much less energy to the box, making it sound much less boxy.
An example of a push-pull sub.
Push-pull tends to cancel the non-linearities of the coil moving thru the motor assembly. So the more non-linear the driver the more important this is. So drivers that go for quantity instead of quality benefit more from push-pull than from push-push.
A woofer with linear motor, push-pull has no benefit.
Push-pull drivers can take at least some of the advantages of push-push by taking measures to couple the drivers. Use ready rod and bolt the two speakers (& the cabinets) all together at the bolt holes. If the driver has a vent you could sacrifice it and run a rod (non-magnetic) thru those and couple the motors together.
Of course there is always push-push-push-pull. And since it pretty much has to be isobarik to make this work, you have 4 woofers using a box with the same volume you would use for one.
All three give the edge to push-push. And you operate the driver where it is linear.
A bipole. At lower frequencies (ie below baffle-step) a bipole operates like an omni-pole which is what MBL is aiming for.
Again if we reference the TLb you can see this. (baffle step at ~ 650 Hz)
I don't know if i'd put it that way. I dipole has nulls at the side, so it interacts less to the side walls.
Actually it tends toward the opposite. But is is still a good idea. A big part of the benefit of an open-baffle (a dipole) is it takes the box out of the equation... similarily a push-push bi-pole.
what i just said.
You might well not. You can also add a filter to the back driver to roll it off above bafflestep. I have a room that works well with a bi-pole and i like to just run the back FR all the way up.
Their web-site is far to busy, but you might glean some stuff from Mirage.
dave
Variac said:
Check outFig 5.2. The bottom trace is a single woofer, the top trace the bi-pole version. If you think about what happens when you hit baffle-step -- the sound is progressively wraping around the cabinet more & more as the frequency goes down. The same is happening with the back driver but facing the other way -- as the output of the front driver starts to fall off, it is exactly filled in by the bafflestep on the back driver.
The compromise is that the speaker has to be out into the room more (not necessarily a bad thing)
An open baffle is without box, a good push-push driver arrangement transmits much, much less energy to the box, making it sound much less boxy.
An example of a push-pull sub.
Push-pull tends to cancel the non-linearities of the coil moving thru the motor assembly. So the more non-linear the driver the more important this is. So drivers that go for quantity instead of quality benefit more from push-pull than from push-push.
A woofer with linear motor, push-pull has no benefit.
Push-pull drivers can take at least some of the advantages of push-push by taking measures to couple the drivers. Use ready rod and bolt the two speakers (& the cabinets) all together at the bolt holes. If the driver has a vent you could sacrifice it and run a rod (non-magnetic) thru those and couple the motors together.
Of course there is always push-push-push-pull. And since it pretty much has to be isobarik to make this work, you have 4 woofers using a box with the same volume you would use for one.
All three give the edge to push-push. And you operate the driver where it is linear.
A bipole. At lower frequencies (ie below baffle-step) a bipole operates like an omni-pole which is what MBL is aiming for.
Again if we reference the TLb you can see this. (baffle step at ~ 650 Hz)
I don't know if i'd put it that way. I dipole has nulls at the side, so it interacts less to the side walls.
Actually it tends toward the opposite. But is is still a good idea. A big part of the benefit of an open-baffle (a dipole) is it takes the box out of the equation... similarily a push-push bi-pole.
what i just said.
You might well not. You can also add a filter to the back driver to roll it off above bafflestep. I have a room that works well with a bi-pole and i like to just run the back FR all the way up.
Their web-site is far to busy, but you might glean some stuff from Mirage.
dave
JohnR said:
The manufacturers would look at it as... another baffle, another grill-cloth, and one less speaker to show off and worry about people being able to push them in towards a wall. And DIYers often look to the commercial guys for inspiration...
You have to Think Different to get there.
dave
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