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[Matt Loretitsch]

Antone:  How do you get the 1/3 wavelength between driver centers for a line array?  I think this is incorrect.  It's 1 wavelength is it not?

There is some high frequency lobing stacking horns together as evidenced in the JBL white paper here:
http://www.jblpro.com/pub/technote/tn_v1n07.pdf

It's nearly impossible to avoid that behavior unless you use ribbons as your high frequency transducer.  That hasn't stopped a lot of manufacturers from using conventional compression drivers on horns (or waveguides as the market speak folk like it).  Heck, the VLA array from jbl doesn't even use a waveguide for the cohesive wavefront...normal horns.

Not starting a war...perhaps I don't have a good grasp of the subject myself.  Once in a great while I'm wrong  
-Matt

[peter.golde]

Speaking of TOPS FOR LABS, there were some interesting results from the latest PSW get together hosted by Evan K, a show which he got to test drive 4 properly powered Lab subs. His (mid level?) 3 way TRX tops suffered blown midrange drivers(horn loaded). I assume from the level of PSW talent on hand, that they were properly powered, limited, and driven.
I would much rather have been driving a pair of DR250's per side. They would have been a much better match for the Labs, and light enough to be pole mounted above the crowds head. I can guarantee they would have sounded better, time smeared mids or not. There are  a lot of variables, mostly room oriented, that have a much more significant impact on the sound. If I can start out with a clean tight low bass and midbass, dynamics that only a horn can reproduce, clear vocals, and smooth top end, that goes a long way in the list of compromises that are present in any speaker design.

[Dave Rickard]

Antone Atmarama Bajor wrote on Sun, 19 November 2006 19:18

10kHz has a wavelength of 1.356"  to say that there is no apparent phasing between the piezo array is preposterous.  It will be worse depending on orientation.  But remember the rule of thumb to speaker arrays keep the spacing less than 1/3wavelength between radiator centers to achieve gain and keep polar pattern reasonable.         This is quite impossible giving the frequencies involved with the dimensions of the piezo tweeters.

Antone,

Line arrays are not in my future, I'm a small-time guy, but I don't understand something here.

Since piezo drivers are  physically smaller than compression drivers with magnets, how can any line array cabinet use compression drivers and avoid this?  Are ribbons the only option?  Do all commercial, professional designs use ribbons?  If not, how have they dealt with this (or haven't they).

I do realize this is a totally different point than Jens "mids" issues.

Dave

[Jens Droessler]

@ Leland Crooks: Of course asking Bill will get me the REAL answers. Like a car salesman tells me the REAL fuel consumption of a car.

@ Antone: That's exactly what I was talking about.

@ Maurice Carr: I heard some DR cabs, they were 290 or 300, I even played around with the EQ. And they sounded EXACTLY how I thought they would (and that is pretty bad). So why should I invest money in building these if they don't satisfy me?

Yeah, you are right. Science is total BS. And things drop to the bottom because god pushes them down. I think BFMs designs are for 'friends of creationism', blindly believing their obviously untrained ears (it's their good right, nothing to say about that) and the sweettalk of BFM, and not for people knowing what happens around them.

Strangely enough, seemingly nobody with the knowledge of acoustics have built them to tell me about the physics backing up your statements (because they know it won't work that way. It's that simple!). Or maybe they built them and simply agree with me after testing them.  I have the science (to be fully sure I recently talked to MANY professional speaker designers about it and they laughed at me for me even thinking I could be wrong about that) AND my listening experience (that is of course subjective) to backup my side of the story. Where's yours? Where are your counterarguments to mine? Saying 'but it DOES sound good' over and over again is no argument, also you can't get me on 'you never heard them', so what's next? Assasination of my character?

[Dave Rickard]

Jens Droessler wrote on Mon, 20 November 2006 10:06

Yeah, you are right. Science is total BS. And things drop to the bottom because god pushes them down. I think BFMs designs are for 'friends of creationism', blindly believing their obviously untrained ears (it's their good right, nothing to say about that) and the sweettalk of BFM, and not for people knowing what happens around them. [snip] so what's next? Assasination of my character?

Speaking of character assasination, you can stop now.

Caution: Philosophy drift ahead!

FWIW, I'm interested in the science behind this discussion, it's important.  

But let's not forget that science, by necessity, gets "updated" when new phenomenon is discovered. Think of the treatment, by the contemporary sciencists, of Louis Pastuer.  It was not the church who ridiculed the idea of microbiology, it was closed-minded scientists and medical professionals who attacked this "obviously untrained creationist".  Then, grudgingly, they began to experiment and understood what just happened to the dominant paradigm.

I believe there are more discoveries to be made in the areas of acoustics and speaker design.  I think we're still in the infancy of audio reproduction and have much to discover.  Also new driver technologies will eventually change how we do all of this, but the laws of physics will remain, if we understand them fully.

The laws do not change, but our undersatnding and application of them will.  Science doesn't change, but scientists should, at least if they're open-minded enough to question and test new theories.

When it comes to audio, I'm all for "intelligent design"!

Dave

[Mike {AB} Butler]

Dave Rickard wrote on Mon, 20 November 2006 12:49

But let's not forget that science, by necessity, gets "updated" when new phenomenon is discovered. Think of the treatment, by the contemporary sciencists, of Louis Pastuer.  It was not the church who ridiculed the idea of microbiology, it was closed-minded scientists and medical professionals who attacked this "obviously untrained creationist".  Then, grudgingly, they began to experiment and understood what just happened to the dominant paradigm. I believe there are more discoveries to be made in the areas of acoustics and speaker design.  I think we're still in the infancy of audio reproduction and have much to discover.  Also new driver technologies will eventually change how we do all of this, but the laws of physics will remain, if we understand them fully. The laws do not change, but our undersatnding and application of them will.  Science doesn't change, but scientists should, at least if they're open-minded enough to question and test new theories.

Dave,
What you should do is examine the anecdotal evidence - forget about the science and physics. There are several things here that make no sense:
- First, IF BFM is really a top-notch designer, why isn't he currently employed at one of the major players in the box design biz? Nobody wants real talent to go to waste. At the very least, some second-tier vendor should've contracted with him to build something along the lines of what he now has.. they could save a bundle.. and get a higher performance box to boot!
- Next, If his ideas are so noteworthy (especially the duplicate HF drivers in all the full-range designs), how come none of the other major designers are doing this practice? It would be great if we all could replace our ridiculously expensive HF compression drivers with banks of PZT's!
- Last, None of his boxes are really easy builds (you can see this by looking at the cutaways he shows on many). These are time consumptive, prototype-style builds, which while certainly possible to do, make little or no economic sense to a company that's trying to turn a profit in a highly competitive industry (and I stake my reputation as a 30+ year cabinet builder veteran). Look at how many pieces it took to build a Klipschorn.. and how expensive that made the box!
Sure, all the designs work. As another poster put it, WHY haven't renowned designers and reviewers with many years experience built and reviewed these? Why do we only get the word of DIY'ers.. admittedly, some may be very knowledgable.. and not a bolster from the more orthodox designers?
Anyway, just my questions (yet to be answered)..
Regards,

[Jeff Babcock]

Jens,

Please keep your posts to a professional level and let's not get into throwing derogatory comments at BFD builders/users.

Comparing Bill Fitzmaurice to a car salesman... come on.... Bill is extremely well versed, and from what I have seen he is extremely helpful to those building his designs.  He is not out to lead anyone astray for personal gain - if he were, he certainly would not be using his current business model...

As for your "friends of creationism" comparison and religious overtones... I would suggest that comments like that certainly won't make you any friends here on PSW.  Again, please stay to the topic and avoid bashing.

Anyway, back to the subject at hand....

You do have a valid claim in that there are plenty of BF builders who have very litte experience in the pro audio world.  This is a byproduct of the fact that his designs can be built so inexpensively.  You draw a lot of people just looking to save a buck.  They do, and they all seem very happy, regardless of whether or not what they build is something that you or I might be satisfied with... who knows.

Certainly it will take a considerable amount of time for Bill's newer designs such as the DR cabinets to gain momentum and have good a/b comparisons done.  There are some quite favorable reviews slowly coming in.

However, I would never claim that from a purely sonic perspective that Bill's DR cabs are superior to other designs.  Where they really shine is cost, efficiency, weight, SPL output, and arrayability.  They need major processing (so do EAW line array boxes - have you seen their unprocessed curves?!?)  With some extensive processing the DR290/300 that you heard can be a very good box.  EAW NT series good? No.  But for the price of 1 NT cab you could build a massive BFD rig that could cover 5000 people.  Therein lies the appeal.

Another thing on the sonic issue - a lot of people seem insistent on building Bill's designs and not using the recommended drivers.  It is also a complicated build - are you certain there were no errors in the build, air leaks, etc?  Do you know if the cabs you heard were built completely according to Bill's recommendations?  Were the drivers bedded in for the recommended period before testing? Were they run biamped? Did you run RTA/Smaart on them?  My suspicion is that if they really sounded terrible to you then something was seriously wrong.  Certainly your preconceived opinion that they would suck would also skew your listening session (however to be fair the opposite can also be true).

To summarize - the BF designs, while not perfect (nobody's designs are!) are amazing given the miniscule cost to build.
Please, show me a design that performs better (cost, efficiency, spl, weight, arrayability, sonically) without costing significantly more and I'll happily build it.

Unlimited budget?  In that case, forget DR cabs, go buy a V-DOSC rig and live happily ever after.  They'll be glad to take your money.

Cheers
Jeff

[Maurice Carr]

Jens Droessler wrote on Mon, 20 November 2006 11:06

@ Maurice Carr: I heard some DR cabs, they were 290 or 300, I even played around with the EQ. And they sounded EXACTLY how I thought they would (and that is pretty bad).

mmmmm....some DR cabs????....there's quite a difference between a DR290 and a DR300. Any scientific approach would have necessitated knowing what it was you were testing and if they were that bad, you would have remembered exactly which on it was. Sounds like porkies to me to be frank because those ( other than the designer ) who have built them correctly and compared them to other more "professional equipment" in live situations would completely disagree with you.  

Jens Droessler wrote on Mon, 20 November 2006 11:06

Yeah, you are right. Science is total BS.

Read my post a bit more carefully please, I never said that. You were the one who brought the bulls**t up in the first place.

Jens Droessler wrote on Mon, 20 November 2006 11:06

...backup my side of the story. Where's yours? ..Saying 'but it DOES sound good' over and over again is no argument,

35 years in the music industry - as a musician. I did not use the rider 'but' - you're quoting statements once again that I did not use. They do sound better, period, no ifs or buts there. Go onto to the BFD forum and find out for yourself how many professional sound guys are building and using this equipment because it sounds better and does the job more efficiently. Why would so many pros be wasting their time building and investing in equipment that sucked?

Jens Droessler wrote on Mon, 20 November 2006 11:06

Assasination of my character?

I don't need to - you seem to be taking care of that yourself.

[Jeff Babcock]

Mike {AB} Butler wrote on Mon, 20 November 2006 13:39

Dave, What you should do is examine the anecdotal evidence - forget about the science and physics. There are several things here that make no sense: - First, IF BFM is really a top-notch designer, why isn't he currently employed at one of the major players in the box design biz? Nobody wants real talent to go to waste. At the very least, some second-tier vendor should've contracted with him to build something along the lines of what he now has.. they could save a bundle.. and get a higher performance box to boot! - Next, If his ideas are so noteworthy (especially the duplicate HF drivers in all the full-range designs), how come none of the other major designers are doing this practice? It would be great if we all could replace our ridiculously expensive HF compression drivers with banks of PZT's! - Last, None of his boxes are really easy builds (you can see this by looking at the cutaways he shows on many). These are time consumptive, prototype-style builds, which while certainly possible to do, make little or no economic sense to a company that's trying to turn a profit in a highly competitive industry (and I stake my reputation as a 30+ year cabinet builder veteran). Look at how many pieces it took to build a Klipschorn.. and how expensive that made the box! Sure, all the designs work. As another poster put it, WHY haven't renowned designers and reviewers with many years experience built and reviewed these? Why do we only get the word of DIY'ers.. admittedly, some may be very knowledgable.. and not a bolster from the more orthodox designers? Anyway, just my questions (yet to be answered).. Regards,

Hi Mike,
I'll take a stab at your questions:

1) There could be many reasons why Bill isn't employed with one of the major loudspeaker manufacturers
-he lives in New Hampshire, not exactly a hotbed of manufacturers
-he is already employed as a sound consultant (his designs are not his bread and butter so to speak, plus he doesn't charge very much to buy the design anyway)

2)Why are other manufacturers not doing this?  Esp w/PZT's?
-I think you pretty much already answered your own question - because it is too time consuming to build, and repairs would also be WAY more difficult than on traditional designs.  As well it has significantly different crossover requirements thus in a standard front load box the LF speaker would have an even more difficult job keeping up with the high end output levels.

3)None of the boxes are easy builds
-Very true, they don't make sense for a manufacturer to build unless they want to price them more expensively, and really only reputable companies can get away wich charging big $$.  Actually EAW, JBL and others do have horn-loaded designs in some of their top cabs.  They are very expensive, but they still must fill a niche or they wouldn't build them.

4) Why haven't renowned designers built/tested these?
- DR cabs are a fairly recent design
- renowned designers probably have better things to do with their time - they don't likely have budget limitations so will pursue more expensive options.
- there are lots of ways to build horn-loaded boxes, they've been around for a long time - designers probably each have their own ideas of what works best.  What real incentive would there be for them to build Bill's designs?

Cheers
Jeff

[Matt Loretitsch]

Jens:  Do you have a reference material I can read about the folded horn midrange issues?  I'd like to learn more about where you are coming from in your argument.

There are a lot of beginners building these boxes...some of us regularly do pro audio though.  I can't comment on his tops since I don't have any.  I have my own conventional design.  I do however enjoy the sub designs.

-Matt