[JLM]

Bipole design simply tries to simulate an omni-directional design while doubling the number of drivers which adds efficiency, power handling, cone surface area, and of course the rear wave projection while eliminating baffle step losses.

Lowther drivers are efficient, expensive, highly detailed (too much of a good thing?), are known for having an exaggerated midrange, and historically had quality control issues. 

Audio Nirvana drivers are sold through "Common Sense Audio" that is owned/operated by David D*cks.  He has a colored history (I'm tempted to say more).

Personally I can't get my head around how a whizzer cone really works (unsupported, mechanically crossed over, and the sound waves it produces interacting with the sound waves from the main cone), so I've avoided them.

I'm still amazed how much better DEQ sounds than the baffle step/zobel circuit that my speakers came with.  Part of it probably is a result of having the purest possible connection between amp and drivers.

[Duke]

Neobop, I don't have any experience working with Lowther or Audio Nirvana drivers.  That being said, I'm in favor of doing things that produce a worthwhile net improvement, and if that means active or passive equalization then so be it.  If you have a high output impedance amplifier, a Zobel could act as a gentle contour filter.

JLM, your DEQ approach sounds like it's been very successful.  Nice job!

I understand what you're saying about bipolars being similar to omnis, but in my opinion there can be some important differences.

For the record, my bipolars do not try to simulate an omni.  My bipolars give a more natural direct-to-reverberant energy ratio than an omni does (voices and most instruments aren't truly omnidirectional, but rather have mild directivity).  My bipolars can be positioned and oriented to give a fairly long time delay before the onset of the additional reverberant energy yet can still be placed close to the side walls, so in many rooms they're more practical than an omni.  My bipolars have never been accused of exaggerating image width like omnis do with some program material.  Center image stability for off-centerline listeners is superior to that of an omni with a properly set up controlled-pattern bipole (I can explain why if you'd like). 

Still, if we're putting speakers into broad categories, my bipoles could reasonably be lumped in with omnis and dipoles. 

[Duke]

The production version of my offset bipole speaker using the Tang Band W8-1772 is under construction now, and I expect to receive the cabinets from my woodworker in late January. 

The enclosures will be shaped like the Planetarium Beta main modules, but the finish will be natural oak because I think that looks better with the light yellow of the Tang Band cones and copper of the phase plug.   You can see a picture of the Planetarium Beta main modules here, scroll down to the fourth picture:

http://www.audiocircle.com/index.php?topic=60103.0

Preliminary specs are 94 dB/1 watt, 16 ohms, and -3 dB at about 55 Hz typical in-room.   So they can be used as stand-alone speakers or combined with a sealed Swarm.   I'm trying to keep the price down around the two grand ballpark, but I'll have to see what the actual enclosure cost is before setting the price.

Now -3 dB at 55 Hz doesn't sound very impressive, but there is no baffle-step falloff in the lower midrange/bass region because the wraparound from the rear driver fills in, and therefore the tonal balance will still be quite good.  I could have pushed the bottom end extension down further with a larger enclosure, but the cone excursion would have gone up significantly and one of the things I'm trying to do is strike a good balance between cone excursion and bass extension because cone excursion is the enemy of clarity when it comes to fullrange drivers.  In fact, in this application one of the advantages of the bipolar format is that it allows me to double up on these excursion-sensitive fullrange drivers so we can reach higher sound pressure levels before the nasties set in.

[Berndt]

Duke, any thoughts on the field coil stuff?
happy holidays, BTW!
Regards,Bill

[Duke]

It's been some time since I looked into what's available with a field coil motor.  I'm aware of Fertin and Supravox, and I read recently about a Lowther with a field coil motor.  But I'm not aware of any other current-production field coil drivers aside from custom-made stuff for a few high-end speaker manufacturers.

[Duke]

The single-driver based speaker project has been terminated. 

I recently finished up a pair of bipolar speakers using the Tang Band W8-1772 drivers, which I still think are excellent fullrange drivers even without any equalization.   In my opinion a couple of small notch filters and a contour filter made a worthwhile improvement.  But then when I compared 'em to what I was doing in a two-way format that would come in at a few hundred dollars more, the two-way was superior in timbre, clarity, dynamics, low-level resolution, and it just sounded more like live music.  This caught me by surprise; I fully expected the bipolar fullrange driver project to sound better at low and medium volume levels for a variety of reasons.  Listened to by themselves the fullrange driver speaker sounded pretty good, but in a comparison they were obviously falling short. 

I have some ideas of how to improve the fullrange bipolars, but in the end I think they would still come up short compared to the more conventional speaker, and the changes would increase the system cost.   

So I learned a lesson, and it looks like AudioKinesis speakers will be pretty much following in the footsteps of what has worked for me in the past:  Prosound drivers and attention to radiation patterns.

I will be making a post within the next couple of days introducing the speaker that basically killed off the fullrange driver project.  I'm kind of excited about it.

Duke

[TRADERXFAN]

Duke,
I find this an impressive statement, especially coming from a manufacturer, for a variety of reasons. Kudos. 

Sorry that it wasn't a fruitfull endeavor for you, though.  I can only imagine how much work went into this. I hope this experience bears fruit in some way down the road.

I am looking forward to seeing what you have in the works now though.  I wish you good fortune...


-Tony

[Duke]

Thank you very much, Tony!

I'm cursed with an over-active imagination when it comes to speakers, so yes I have ideas for projects that would use some of the things I learned from the bipolar fullrange project.  In particular, I learned some things about how to make a narrow-band notch filter that apparently doesn't have a sonic downside.   That opens up some possibilities.

In retrospect I really needed to use a much bigger box, as bass extension was inadequate (I had about 2.2 cubic feet shared between the two drivers).   Or I could just use one driver, which would then have plenty of box volume.  But once I go to a single driver I'm building a Bob Brines wannabe system at best, and I'm not going to beat a master at his own game so there's not much point in doing that.

Anyway, I'll introduce the new speaker later tonight.

Duke