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Old 4th September 2007, 05:39 AM   #1841
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No Xmax listed, dunno about that one. The Qts of the 8-ohm driver looks appealing, and they certainly look like candidates for the bass portion of the array, either in pairs next to the floor or a delta-trio array.
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Old 4th September 2007, 06:06 AM   #1842
BudP is offline BudP  United States
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Lynn,

Perry says he has shipped me a pair of FR 8 Hemp cone drivers for treatment. I have treated a pair of FR 4.5 drivers with very positive results. I am eying a pair of Audax 6.5" PR 17HR70 midrange drivers, capable of 99 dB sensitivity, I just drug out of my stash, from back in 92 I believe, maybe even earlier than that. Mille N said they were the best midrange drivers he had heard, period. You will be able to audition the Lowther PM6A in a month or so. I suspect we will be narrowing down on a "best" for you driver and it may be "best" for everyone too.

Will depend upon just how good I have to get, to match Alexsander's ribbons. Romy says "perfect" so certainly, the full on process, both sides and Soongsc's intermediate pattern, on both sides of the FR 8 from Hemp. I am quite sure the Lowther PM6A's are already a match and the DX4 might be more than a match, dunno. Should be fun to find out.

Bud
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Old 4th September 2007, 07:10 AM   #1843
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Hi Lynn and Bud,

I agree with Lynn in that ordinary bipolar caps are horrible, however there are at least one decent bipolar out there; it is the Wicon brand. The company closed years ago but quite a lot of their caps are in circulation. They come in two versions - smooth surface fiol and acid treated surface foil.
Wicon was a competitor to Jensen Capacitors and I have been told that their production methods and tools were essentially the same.

Bud, I'm looking forward to hearing about your results with the FR 8 Hemp. My own FR 6.5 have been EnABL'd except for the Micro Gloss coating. Still waiting for the Microscale shipment to arrive. I suspect the whizzer cone is getting the most benefit from the EnABL treatment.

Cheers
Kris from the land of Peerless
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Old 4th September 2007, 11:35 AM   #1844
SunRa is offline SunRa  Romania
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Hello Mr. Olson,

Quote:
and possibly 4 kHz for the 8NMB420 - the data looks kind of sketchy for that driver.
I see you are considering 8" drivers after all. Even the Lowther PM6A seems an option as Mr. Purvine indicates. How low are you going to cross these drivers. It's an option to let them roll of naturaly?

Quote:
The lowpass and highpass filters will probably be low-Q 2nd-order filters, since I've used them before for quasi-time-aligned speakers, and they work pretty well if you accept a small amount of ripple in the crossover region.
Are you going to try a transient perfect crossover for the mid-high section? And if yes, what is your strategy? I think I am not the only one who hopes for a general article about crossovers. The amount of informations on your site is great but more related to Ariel's specific cross-over.

Quote:
Holding a modest B.Sc. in Psychology, it's been entertaining looking at all the fruitless and frankly, absurd theories that have come and gone about consciousness. When I started my studies in 1968, the Behaviourists ruled the roost, and they (led by their guru, B.F. Skinner) had the audacity to claim that consciousness didn't exist at all!!! Well, growing up a partial Buddhist, that claim was too ridiculous to be considered, and it was satisfying to see the Behaviourists lose their hold over the profession by the mid-Seventies, to be replaced by the Transpersonal Therapy group.
Quote:
The neurologists had their try with the equally ludicrous "Telephone Switchboard" theory in the late Sixties through the Seventies, and when digital telephone exchanges became ho-hum technology, switched to a computer metaphor, despite the obvious and massive parallelism of physical neurological structures, and the complete absence of any kind of programming language. They then tried the "Hologram" metaphor, until you think for a moment and realize it describes exactly nothing and predicts nothing, it just sounds cool and has lasers in it. Yes, memory appears to be distributed through many structures in the brain - but it doesn't mean it has anything to do with wavefronts or the types of coherent structures seen in a hologram.
Quote:
Now the fashion seems to be computer-operating-system based models of "Theory of Mind", that there are many small sub-minds all co-operating together, and somehow this magically transforms into what we experience day-to-day as consciousness. Uh-huh, yeah right, and the evidence for this is ... ? Like the discredited theories of Freud, where we've never found any evidence whatsoever for Id, Ego, and Superego, there's not much evidence that consciousness is something like a modern computer operating system - and why should there be any correspondence?
For some more armchair philosophy: you may consider this from an ephistemic poit of view. These may well be just paradigmatic sequences in our cultural history, speaking in terms of Kuhn's theory of scientific revolutions. To get even more philosphical, this may be even what Hegel's intuition called Zeitgeist... of course with more profound consequences. What I am trying to tell is that this pattern we can see in our history of ideas may let us know something about the way we are relate to what we call reality; not just accidental fashion or trend.
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Old 4th September 2007, 02:41 PM   #1845
Salas is offline Salas  Greece
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Quote:
Originally posted by Lynn Olson
The electrical lowpass filter will also acoustically delay the 8 or 12-inch driver a little bit - good question how much, but an inch isn't unreasonable. One thing I know for sure the RAAL ribbon isn't going to be on the same plane as the front of the driver - it'll be some distance behind that.
When you will be fully able (I wish you full health sooner than expected), and you will be in the alignment phase, after having slopes determined, you can always pinpoint the offset by subtracting excess phase from 2 different mic distances.
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Old 4th September 2007, 08:25 PM   #1846
ScottG is offline ScottG  United States
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The DiVinci review is up:

http://www.6moons.com/audioreviews/davinci/davinci.html

A few things "jump out at me" here:

1. While the speakers have plenty of "magic" - the real system "magic" is with the amplifiers. This is no doubt do to the use of DHT drivers and an independent power supply for each stage of the amp. (..frankly the use of a non DHT tube for the input/preamp is sub-par IMO for such an expensive design, I do however think that the use of 2 transformers for the parallel output stage is pretty "trick".)

2. There are still room interaction problems with the dipole. (..I've been saying this for a while now despite the pervading myth that dipoles react less to the room.) I suspect though that he is having even more problems with the wide-band driver being driven full-range with no doubt the resonance region not only having its typical "slow" sound (lack of dampening), but also being boosted by the amplifier's drive into a higher impedance load. In fact the additional excursion presented to the smaller driver this way will also decrease the apparent "speed" of the driver's presentation.

3. Tonally this speaker is better than most (i.e. harmonics and decay character.. Not freq. linearity). Low mass drivers with low mass and low resistance surrounds.. coupled with an electromagnetic motor. Also note the coupling interface - rigid and massive metallic rings (likely brass), joined to a lossier material (wood). This could be further improved by sand loading/dampening the baffle's edges. The rigid interface of the brass ring usually improves low level detail and focus.

4. It lacks some image focus. Large diameter drivers at higher freq.s with plenty of boundary reinforcement from the driver's diaphragm and the baffle.

5. The bass has plenty of "speed", but it lacks a more dynamic character. The lack of "dynamics" is a compression feature in the midbass that box speakers have (..particularly closed box with smaller enclosures and high force drives). The positive virtue of bass "speed" is largely derived from relatively low mass drivers that are a LOT more efficient than an average driver.

Anyway.. just my thoughts on a system far more interesting than your "run-of-the-mill" commercial products. Seriously flawed.. but perhaps providing more of whats important. It also has some positive design elements that could be incorporated into the design here.
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Old 4th September 2007, 08:37 PM   #1847
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Quote:
OK, You Asked For It
'Nuff off-topic stuff, here's a little bit of data - three drivers, rather crudely normalized in Photoshop (the 8NMB420 graphic was pretty bad to start with). I tried to get the 1 kHz and 20 kHz frequency markers and 10 dB markers to align with each other, so the curves would be roughly comparable.
Lynn,

Being the detail oriented, analytical type - with lots of tools in my 'bag of tricks' - I have the following results to show:

Click the image to open in full size.

The efficiency of the Tone Tubby is a bit of a guess based on the published efficiency (2.83-V SPL = 98.3 dB, 1-W SPL = 97.3 dB). The 18sound the data is presented as-reported on their data sheets.

If there is any interest, I can go a little further and create data files which can be imported into simulation software.

I Hope you'll be mobile enough to make it to the RMAF,

Edward
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Old 4th September 2007, 09:55 PM   #1848
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Nice curves!!! Curious how you imported them - scanned, then imported into a scientific data-analysis package that somehow removed the extraneous graph lines?

It isn't hard to see what the crossover needs to do to match a tweeter in coming at 1.6 kHz. First, compensate for the up-slope starting around 1 kHz, then smooth the corner region around the 2~4 kHz peaks.

As for choice of drivers, the downside of the Lowther solution is a genuine requirement for a high-pass filter somewhere around 200~300 Hz, and a stoic acceptance of diminished dynamic range (compared to prosound or horns). Whether the Xmax (both directions) is 1mm or 3mm, that ain't very much - midrange territory, not what I'd call midbass, which implies some degree of bass capability. So the Lowther, at the very best, is going to be a midrange driver. The fact that I am no fan of whizzers reduces the usable range even more - the Lowther I'd be most interested in would be the custom Alnico version with no whizzer & EnABL treatment. As mentioned earlier, no interest in Fostex or Eminence drivers, sorry. Heard (and measured) them, not for me.

Dunno about the EnABL'ed Hemp Acoustics 8-incher. Don't like whizzers and the crude mechanical crossover, diaphragm shading, and enclosed cavity between the whizzer and main cone - acoustically, this is just ugly. It seems especially unnatural to mate something as coarse-sounding as a whizzer cone - the worst kind of tweeter in existence - with the ultra-low mass and air-damping of a ribbon. Fish and fowl, as it were.

Alexander of RAAL is the one that's mentioned what he feels is the natural 1.5 kHz limit of ribbons- due to issues of ribbon mass vs air-load mass, he feels this limit obtains regardless of the physical size of the ribbon, whether it's a few inches high or six feet high. As the driver designer, I defer to his experience, and don't plan to use the ribbon outside of its optimum region. Similarly, with horns, it's best not to get too greedy and expect more bandwidth than they can deliver - a decade from top to bottom is about it. I'm no genius when it comes to horns, but I do know that asking too much LF extension from them is asking for lots of coloration, a ragged impedance curve, and much more IM distortion.

So the real question, whether a horn/WG or ribbon HF is chosen, is what direct-radiator sounds best up to 1.6 kHz? That's what remains to be seen. The choice of a horn/WG relaxes the crossover to maybe 1~1.2 kHz, but that leaves the choice of midbass driver pretty much the same. (Yes, I know a really big mid-horn could go all the way down to 300~500 Hz, but that's another speaker design, one with with several time-aligned horns covering different parts of the spectrum, and not really a dipole at all.)
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Old 4th September 2007, 09:56 PM   #1849
Salas is offline Salas  Greece
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Quote:
Originally posted by Lynn Olson
Nice curves!!! Curious how you imported them - scanned, then imported into a scientific data-analysis package that somehow removed the extraneous graph lines?

Used a curve tracer probably. Here Lynn. Read about SPLTrace.
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Old 4th September 2007, 10:38 PM   #1850
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Quote:
Originally posted by Lynn Olson
Nice curves!!! Curious how you imported them - scanned, then imported into a scientific data-analysis package that somehow removed the extraneous graph lines?
The basic tool-chain summary to genrate these curves:

From the 18sound .pdf's on their website, I took screen captures and saved them. Then I used a (java) program called DataThief to (almost) automatically convert the curves in the charts to x-y data and exported them to .txt files. Then I pulled the text files into Word and tuned-up the formatting and saved. Then I imported the text files into Excel to get all the numerical formatting consistant and saved out in .prn format. I changed the extension to .FRD and then imported them into Speaker Workshop. In Speaker Workshop I scaled your data to match the published efficiency and then created chart to compare all three curves. Then I took a screen shot of the chart, saved it and posted it on the internet to link to the post.... All in days work

As I mentioned before, I am about 80% the way to data files which could be imported into simulation software. If there is interest, I can finish up the manipulation / conversion process to create the necessary files.

Edward
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