[afungi]

Hello...I'm new here, but I've relied on the information at this site for a while now.

I came across these the other day...I'm thinking about purchasing a pair of them...

http://cgi.ebay.com/Tekton-Design-Fostex-4-5-Full-Range-Open-Baffle_W0QQitemZ260292488279QQcmdZViewItem?hash=item260292488279&_trkparms=72%3A1205%7C39%3A1%7C66%3A2%7C65%3A12%7C240%3A1318&_trksid=p3286.c0.m14

I've tried to wrap my brain around how these work for a day now, and the more I think about it, the more it makes sense.

Has anybody purchased these or can anybody give me an idea about them?

Thanks.

[DaveC113]

The 91 dB sensitivity seems low, I thought sensitivity would go up adding a 2nd driver?  It is an interesting design, I can't predict how it'll sound compared to a conventional BR....

[chrisby]

The 91 dB sensitivity seems low, I thought sensitivity would go up adding a 2nd driver?  It is an interesting design, I can't predict how it'll sound compared to a conventional BR....

this one certainly looks different enough that normal rules of thumb probably don't apply

[planet10]

I'll have to think about it a bit more, but my 1st inclination is tht we have an acoustic 2-way system. Front baffle FE126 will have dipole roll-off way up high. Enclosed FE127 (or FE126) will produce below that, and the big magnet of the FE126 is going to block most of the destructive interference from the 2.

Next thing to think about is whether they are wired in phase or in anti-phase.

Seems to me that this eliminates the problems of 2 FRs used FR (and Ed;s over the top Model 3 belies some of those)and introduces a whole bunch more (and potentially much more).

dave

[DaveC113]

I'll have to think about it a bit more, but my 1st inclination is tht we have an acoustic 2-way system. Front baffle FE126 will have dipole roll-off way up high. Enclosed FE127 (or FE126) will produce below that, and the big magnet of the FE126 is going to block most of the destructive interference from the 2.

Next thing to think about is whether they are wired in phase or in anti-phase.

Seems to me that this eliminates the problems of 2 FRs used FR (and Ed;s over the top Model 3 belies some of those)and introduces a whole bunch more (and potentially much more).

dave

They would have to be in phase for the claimed cancellation of the backwave to occur... I also don't believe the cancellation could actually be as complete as they claim. But if it sounds good, it sounds good I guess. No way to know unless you try it with something like this.

I also can't believe they could play at any decent volume without the ob driver's excursion getting too large.... but again thats just theory...

[planet10]

They would have to be in phase for the claimed cancellation of the backwave to occur... I also don't believe the cancellation could actually be as complete as they claim. But if it sounds good, it sounds good I guess. No way to know unless you try it with something like this.

Do these points make sense?

If in phase, the volume in the gap remains the same, which gives much the same result as just an OB, since the impedance of air is so low compared to the driver.

Dipole roll-off up near 1 kHz. Highs from the rear driver are going to smash into the big flat rear of the front magnet & cause total chaos. So up high we only have the front driver.

Really low down ... this is where it gets interesting... if as they claim the output from the rear driver cancels the rear output of the front driver, and the drivers are acting push-push/pull-pull to cancel vibration transmitted to the box.

To achieve push-push/pull-pull, then the front driver moves back, rear driver moves forward ...ie rear driver has to be out-of phase with the front one

Now if the drivers are out of phase we are increasing the range of rarefraction/compression in the gap, so increasing the level of the out-of-phase signal coming from the back of the OB part. Is it sufficient to cancel LF output from the front driver and still leave enuff to have bass? Certainly it would bea situation where LF are 180 degrees out of phase withHF.

Now if the drivers are in phase, the volume of the air in the gap does not change, so, given the low impedance of air, is this not much like an OB? Seems to me with the boxed back driver, at very low frequencies it would dominate and give you some bass....

Weird. Anyone find the patent application?

dave

[chrisby]

there's also a 12" powered sub using the same "patent pending"  technology

anyone game to inquire re the :

" One-time-single use, DIY licenses are available (please inquire)!" ?

[DaveC113]

They would have to be in phase for the claimed cancellation of the backwave to occur... I also don't believe the cancellation could actually be as complete as they claim. But if it sounds good, it sounds good I guess. No way to know unless you try it with something like this.

Do these points make sense?

If in phase, the volume in the gap remains the same, which gives much the same result as just an OB, since the impedance of air is so low compared to the driver.

dave

No.... in phase, the rear cone will move out of the gap (to the back of the speaker) as the front cone moves into it, ideally creating no compression of air, hence no sound. But with the magnet structure in the way, its sure to not work ideally. If the drivers were out of phase they would both move into the gap at the same time, increasing the output of the rear wave through constructive interference.

Think about breaking in a driver, you put them face to face, wired out of phase to get some cancellation. If one of the drivers were turned around backwards, you'd also need to switch the phase of that driver to maintain the cancellation. This strategy doesn't work perfectly, the speakers still make sound, and this is a far more ideal scenario than placing a big magnet structure between the drivers.

I don't get how excursion in the ob driver is controlled, you'd need a hi-pass x-over to keep it from reaching its mechanical limits too quickly.   

[afungi]

I've just purchased a pair of them. The lack of definitive responses only made me more curious so I decided to call Tekton Design. I got with Eric Alexander and asked him a bunch of questions.

After a lengthy discussion with him, I'm completely sold on the concept. Since I got to talk to Eric, I have purchased them without reservation.

FYI, I learned that the drivers are wired in matching polarity (in phase), and the excursion and power handling of the ob driver is controlled by a "transient perfect enclosure with mutual inductance coupling". According to Eric, fidelity and power handling goes through the roof.

I'll report back once I have them in hand.

[planet10]

FYI, I learned that the drivers are wired in matching polarity (in phase), and the excursion and power handling of the ob driver is controlled by a "transient perfect enclosure with mutual inductance coupling". According to Eric, fidelity and power handling goes through the roof.

If that is the case, then the line about push-push/pull-pull is erroneous (and my point list was partly made to illustrate that you couldn't have this with cancellation.

dave

[DaveC113]

I've just purchased a pair of them. The lack of definitive responses only made me more curious so I decided to call Tekton Design. I got with Eric Alexander and asked him a bunch of questions.

After a lengthy discussion with him, I'm completely sold on the concept. Since I got to talk to Eric, I have purchased them without reservation.

FYI, I learned that the drivers are wired in matching polarity (in phase), and the excursion and power handling of the ob driver is controlled by a "transient perfect enclosure with mutual inductance coupling". According to Eric, fidelity and power handling goes through the roof.

I'll report back once I have them in hand.

I'm curious how sensitivity drops as well....

He's also using terms that are usually applied to electronics, not acoustics...

A "transient perfect" enclosure would be one that perfectly reproduces the input signal as a compression wave in the air... not sure how an enclosure manages to do this, its usually applied to x-over design.

And mutual inductance is when the magnetic field from one inductor influences another thats in close proximity:

http://www.mathworks.com/access/helpdesk/help/toolbox/physmod/powersys/index.html?/access/helpdesk/help/toolbox/physmod/powersys/ref/mutualinductance.html&http://www.google.com/search?hl=en&q=mutual+inductance+coupling&btnG=Google+Search&aq=f&oq=

So I guess the drivers are mechanically coupled in the same way inductors can be electrically coupled and the rear cone is controlling the movement of the front cone and vise versa...

I wonder if this is really better than a simple bipole/dipole design with the drivers back to back and both in enclosures?

[mor2bz]

interesting stuff for sure

is there a cap on the ob driver?

[planet10]

I'm curious how sensitivity drops as well....

I'd expect that we can only count on a single drivers efficiency.

Closer inspection shows the driver is FE127e, factory rated at 91 (but my measures of over 100 drivers show a bit under 90)

dave

[chrisby]

hey look,  if painted polka dots can make an improvement (notice I didn't say just "a difference") , why couldn't something else that doesn't immediately make sense, work?

 

[planet10]

why couldn't something else that doesn't immediately make sense, work?

Try it you might like it

dave

[David Weil]

What interesting concepts! The speaker is one, and the DIY license is another one.

I wonder about the patent-worthiness. The combination of a dipole and a monopole is called a unipole. That is not a new invention, though a good one. The same goes for compound mounting of two drivers. So what's new? The fact that nobody combined those two things in one speaker before? Or the fact that both concepts are usually only applied for woofers and subwoofers?

[chrisby]

What interesting concepts! The speaker is one, and the DIY license is another one.

I wonder about the patent-worthiness. The combination of a dipole and a monopole is called a unipole. That is not a new invention, though a good one. The same goes for compound mounting of two drivers. So what's new? The fact that nobody combined those two things in one speaker before? Or the fact that both concepts are usually only applied for woofers and subwoofers?

or the fact that no-one has bothered to document it in such a way that the patent office can conclude something new has been described?

note that the ad reads "pending"

we could postulate all we like about what we think is contained in the patent specs, or squabble about it's "newness", but in the end it's probably irrelevant to any who hears them - and to date I think there's no anecdotal reports.

[afungi]

I've had the speakers running for a while now...they're well on their way to being fully broken in. My initial impressions are that the technology works...the sound is open and airy. Build quality is great and visually, they're cool. They image great as well.

Definitely a thumbs up!

[chrisby]

I've had the speakers running for a while now...they're well on their way to being fully broken in. My initial impressions are that the technology works...the sound is open and airy. Build quality is great and visually, they're cool. They image great as well.

Definitely a thumbs up!

Based on a reasonable amount of experience with the FE127E in a variety of enclosure types, the first thing I'd be curious about is the bass extension and pacing - this is a very small for a sealed enclosure for this particular driver. 

[mcullinan]

I've had the speakers running for a while now...they're well on their way to being fully broken in. My initial impressions are that the technology works...the sound is open and airy. Build quality is great and visually, they're cool. They image great as well.

Definitely a thumbs up!

Which ones did you get. I want to try some single driver speakers. Do you think they make good near field speakers?
Mike