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Multi-Way Conventional loudspeakers with crossovers

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Old 12th July 2007, 09:44 PM   #1501
Salas is offline Salas  Greece
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It may also mean that boxes always contain harm. So boxless is the way to go!
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Old 13th July 2007, 03:57 AM   #1502
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One of the best things about working at Tektronix was the team approach to tackling huge design problems - such as the portable 492-Series Spectrum Analyzer. This was a project that had never been done before: a 40 lb. instrument that was fully self-contained, had an on-screen noise floor of -80 dB with no visible spurii at any frequency from 50 Hz to 1.8 GHz, and maintained this level of performance in the field, in a moving helicopter (it was used in the Falklands War by the UK), outdoors at a radar station in Alaska, and other severe environments.

The whole engineering group was about 50 people in Building 58 at Beaverton, Oregon. That group comprised the digital-storage, microprocessor control, microwave, RF amplification, signal processing, switching power supply, and mechanical-engineering subteams - all of them had to be harmonized, since the artifacts of one aspect of the instrument could spill over into another part.

One of more famous sayings of that group was the immortal phrase: "Once you open a can of worms, you always need a bigger can to put them back". This was literally true - despite the tight space constraints, the solution to this or that problem with low-level noise, unwanted sidebands, or phase noise, always seemed to just a bit bigger, no matter what you did, or what resources you threw at it.

The Tektronix/HP "egoless" style of engineering is almost unknown in commercial audio, where a "big" design team for a given project is two to three engineers, and five marketers. Thus, big egos, especially since audio is so commingled at every stage with marketing - the most famous "designers" in this biz are basically marketers, not designers at all, since the real grunt-work is done by anonymous toilers in the vineyard (who are usually fired after the project is complete).

The combination of corporate secrecy, combined with loss of design-team integrity over the years (high turnover), ensures that nearly the entire history of audio is two steps forward, and one-and-half steps back. Wonderful products are put on the market, the original designers are replaced, the follow-on products lose some of the original magic, and ten years later it's as if the first product had never been done.

At one time, the AES Journal was mostly about advancing the art (back in the Seventies), but the last twenty years of digital compression hasn't been about advancing the art, but concealing degradation and information loss from (most) listeners. The audio equivalent of making better and better synthetic non-dairy creamers and margerines. This has discouraged industry insiders from publishing their advancements - instead we get "White Papers" that are little more than marketing gobbledegook, disguised in pseudo-technical phrases that are just good enough to take in magazine reviewers.

The net result has been that audio designers, whether "real" engineers or not, are more isolated than ever. Most have never worked in a genuine team environment and fall prey to Big HiFi Ego syndrome. That's understandable considering their profound isolation from their peers, and the general self-promoting trends of the industry. When you're the only frog in the pond, it's easy to think you're the biggest one of all. And the ponds are isolated from each other, thanks to corporate Non-Disclosure Agreements (NDAs), the breakdown of the patent system combined with the huge volume of prior art, and a system of marketing/magazine reviewing that replaces real technical content with vague marketing buzzwords.

At least the reviews at Car & Driver and Road & Track tell you how many cylinders the engine has, naturally aspirated, turbo, supercharged, shape of the torque curve and presence of torque steer, front and rear suspension geometry, and the impact of the electronic vehicle-dynamics system on handling. This level of technical discussion is taken for granted in car-enthusiast circles, and forms the customer base for the aftermarket "tuner" industry.

In audio, this level of discussion was still common as late as the Seventies, but the transition of the high-end into a fashion-driven "boutique" industry, combined with the gradual removal of serious technical content from the Big Two review magazines, drove down the technical level of discussion over time. This gradually "dumbed-down" the buying public - which I imagine was the goal all along - but also had a severe negative effect on the design community, since they had lost a common forum. There is no English-language equivalent to "MJ" magazine in Japan, or the Audiocraft magazine of the Fifties. We have the Internet and that's it.

The drawback of the Internet is the signal-to-noise ratio - the well-known "flame" problem - but also a mismatch of audiences. DIY covers a huge range of expertise and interest. Since the AES is no longer seriously focussed on advancing the art (in terms of better sound in the home), and English-language audio-enthusiast magazines have fallen by the wayside, there aren't many places for industry insiders to gather and share stories. At the trade shows, the CEOs and marketers have to be brushed off, and the larger companies have "minders" that keep a close eye on the real designers.

This nice thing about diyAudio is that it isn't. By that I mean the forum isn't limited to do-it-yourself projects - but also covers areas that are the edge of commercial audio practice. This is the part I'm interested in, and always have been. Like most of us who've done this thing commercially, we have no interest at all in following in the footstep of XYZ famous-name manufacturers. Been there, done that, got a closet full of T-shirts with company logos on them.

The much more interesting question is, what isn't out there? There are actually large gaps in the market - in loudspeakers, there's a big gap between high-quality commercial prosound and the best audiophile loudspeakers. Although Tom Danley, Siegfried Linkwitz, JP Kreskovsky, and Dr. Geddes are coming from different design perspectives, they are all working well outside standard commercial practice - and this makes what they're doing interesting to any serious audio designer. I don't expect them to agree, but the disagreements themselves are quite illuminating, and reveal interesting sets of design assumptions.

I view audio as a modern form of artisanship, combining engineering, science, and subjective esthetic choices. Artisans do better when they meet and swap things around, just as the engineering team at Tektronix did better because they were able to meet in the same room and discuss the direction they were going. I don't expect the artisans of audio to combine forces, but I do think get-togethers in forums like this are good for all concerned. Any rough edges we see are little more than the result of the isolation we all feel in the hifi industry, which celebrates big egos and plays down the results of successful collaboration.

I'm going to build a high-efficiency dipole, but don't expect a how-to manual. What you're going to see are measurements and comments about what I heard, starting with this and that driver used in a full-range mode on a reasonably large dipole baffle. Considering the huge size of this thread, it would be probably be wise to start a new one once I start publishing hard data.

In terms of sawdust, really, the more active readers already have plenty to go on right now. You gotta measure, guys, and please use something better than that awful 1/3 octave junk - what's useful to me and many others is an unsmoothed FFT, a good impulse response over 5 milliseconds (please absorb the floor reflection), and a CSD plot. Putting the baffle on a lazy susan, marking off 7.5 or 10 degrees per tick, and making a series of measurements is good too.

In terms of getting started, it seems like the minimum is a 8" widerange driver, a single 12" driver at floor level, and either a ribbon or compression-driver+waveguide for the HF. Rather than getting lost in building horns, just buy a good one, and save yourself a lot of trouble. Dr. Geddes is selling his state-of-the-art WG at a very reasonable price, and you get XT1086 for not much at all.

But I would personally start with the wideband driver, and pick one that measures and sounds good - that driver will have a strong effect on the sonic character of the entire system. If it has a lot of HF breakup and harshness, you are committed to a high-slope crossover, and a very awkward and unpleasant system-integration with the HF driver. A driver that sound agreeable over most the audio range is going to a lot easier to integrate into the rest of the system, no matter what set of choices you make.
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Old 13th July 2007, 08:47 AM   #1503
Pano is offline Pano  United States
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Thanks Lynn, a good starting point and a pretty easy one.

Sort of back to the Lucasz Fikus speaker concept. Cover the midrage as well as you can, then fill in the top and bottom.
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Old 13th July 2007, 04:43 PM   #1504
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I agree Pano. Your address for Lucasz Fikus doesn't work...can you redo?

Ray
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Old 13th July 2007, 06:59 PM   #1505
dmason is offline dmason  United States
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FYI, there will be very soon, a Hemp wideband whizzerless 8, designed out to ~9KHz. I believe this will be worth exploring, for smaller scale systems.

Andy Lankester of www.capilanohornspeakers.com has just received the first run of a custom order 15" designed specifically for OB bass. He also has his own bass amp with LP filtering, etc. He sent me FR plot of the driver, and it looks to be the best I have seen yet; very impressive. I am excited about both these drivers coming on the scene. The pricepoints are $118 for the HempTone 8, and $200 for the Capilano 15.
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Old 13th July 2007, 08:46 PM   #1506
Pano is offline Pano  United States
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Quote:
Originally posted by Ray Collins
Your address for Lucasz Fikus doesn't work...can you redo?
Ooops. Sorry, too many http in the address.

Here it is. http://www.lampizator.eu/NIRVANA/nirvana.html

Basically - Lucasz is saying start with the best midrange driver you can, "If midrange is wrong, nothing else matters." He likes vintage 8" Alnico wideband in OB, with a ribbon on top.

Similar to what's been discussed here.
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Old 13th July 2007, 11:23 PM   #1507
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Thanks Pano...

Ray
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Old 14th July 2007, 11:14 PM   #1508
mige0 is offline mige0  Austria
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Default round over close to the speaker

Hi

Quote:
If I udnerstand the question correctly (and I am not sure that I do) that shpe would be a large sphere. It has a flat surface at the source and curves away at the most gradual rate

Earl, thanks for explanation but your patent seems to give me the answer already.
In case of a flat baffle ( BLUE contour) there is NO benefit of any round over at the speaker like there is for any other - less than 180 degree - angle ( RED contour for exampel).

Click the image to open in full size.


This surprises me hence my question I would have thought that there is something better than just to mount the speaker flat to the baffle if NO wave guide is desired.

This also seems to imply that the OS curve becomes less beneficial at very wide wave guides, no ?


###############



Quote:
. The best approach, if one wants to use a direct radiator, is to use a phase plug to better couple the diaphragm to permissable contours (like OS).
......
Our SP line will have a 1" dome (dirt cheap!) coupled to a phase plug and waveguide for a semi-direct radiator waveguide assembly
1.) What is the distinction here between a " semi-direct radiator " and a "real" compression driver assembly ? Isn't it that both have less aperture than the diaphragm area?
2.) what do you mean with a " permissible contour " - are there any other contours ( than OS ) of minimal diffraction?


Click the image to open in full size.

(Pic taken from your patent US 7.095.868. B2)

Greetings
Michael
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Old 15th July 2007, 01:10 AM   #1509
terry j is offline terry j  Australia
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Quote:
Originally posted by Lynn Olson


The combination of corporate secrecy, combined with loss of design-team integrity over the years (high turnover), ensures that nearly the entire history of audio is two steps forward, and one-and-half steps back. Wonderful products are put on the market, the original designers are replaced, the follow-on products lose some of the original magic, and ten years later it's as if the first product had never been done.

The drawback of the Internet is the signal-to-noise ratio - - but also a mismatch of audiences. DIY covers a huge range of expertise and interest.


You must have a lot of time on your hands Lynn, but I'm not complaining as I find your posts entertaining as well as informative.

Talking of the design group above......what is our next project after 'after the ariels' ha ha. Don't mind me, I definitely fall into the internet mismatch of audiences, meaning I don't understand much of this at all!!

Given the way design this has developed and grown, and the means by which it has done so, AND keeping with the greek theme for names, perhaps it should be called Diyana?

I'll let those with more knowledge than I explain what Diana did or didn't do, and I'll probably be corrected and find out she is Roman or something ha ha.
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Old 15th July 2007, 04:39 AM   #1510
lazenna is offline lazenna  Australia
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dmason when will we find out more on these Capilano drivers.I'm looking to buy some now in either 15"or18" drivers for an OB that I want to build.
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