Jump to content

kkantor

Members
  • Posts

    762
  • Joined

  • Last visited

Profile Information

  • Gender
    Male

Recent Profile Visitors

6,039 profile views

kkantor's Achievements

Newbie

Newbie (1/14)

0

Reputation

  1. Z- I don't know where they are at this instant, with all the moving going on... but was there anything in what you gave me that might help David get a matched pair of tweeters? -k
  2. A few comments from the peanut gallery: - First and foremost, this is great stuff. I hope DIY'ers are cherishing this thread. It is very rare that the thought processes and decision trees of a professional speaker designer of Dave's caliber are documented. This is the internet at its best. - The 2K thing looks to me like a crossover problem, rather than a cabinet problem. I'd suspect what you mentioned earlier, about the 1st-order network on the tweeter, conspiring with an agenda to keep the woofer out of beaming or process-variation territory. - Lore around AR was that thermal failure of tweeters was becoming a very serious issue around that time. Amplifier power was skyrocketing, loud music was in, AR was expanding its demographic etc. A great deal of engineering and R&D effort went into mitigating this. - I played around with Holm for an evening and liked it. But, I haven't had the chance to do any serious work with it. Watching this thread, it seems to be an excellent tool, but also showing its roots in automated room correction. Not as much post-processing control as would be ideal. Still, I think the ability to get and display more data, quickly and easily, always wins in a real-world design environment. MatLAB and LabVIEW haven't designed that many speakers... -k
  3. Hellllppp Meeeee..... Somebody Helllppp Meeeeee..... -k
  4. I don't remember seeing this thread, but I totally concur. The original 18 was a great speaker. Its biggest weakness was that the tweeters blew a lot. This problem, no doubt, was compounded by the 18's affordable price, which meant it tended to show up in dorm rooms, etc, driven much harder than originally expected. Also, at this time, amps were starting to get more powerful. Later versions of the 18 were attempts to increase tweeter longevity, at the expense of the elegance of the first iteration. The 18 is also an important product, IMO, because it represented a conceptual shift in AR's general approach to product development. Prior to the 18, AR's product development philosophy was always purely "top down." Flagships were established, then technology and ethos trickled down to low price points in subsequent models. The 18, in contrast, really set the standard by which the 28, 38, 48, etc, were judged. -k www.kenkantor.com www.ztamplifiers.com
  5. No, really, the check is in the mail.... Bret, I just emailed you the tracking number for the box. It actually was shipped on Monday. Fedex ground. -k
  6. Just a quick note... 1- I only got one woofer with this shipment. 2- My site is hosted by Verio and Florida, and has been impacted by the hurricane. As such, people might find access to the data intermittent. I would suggest that Mark move the data over to CSP. -k
  7. Quite some time ago, Tom Tyson entrusted me with an original 12" to test. I have been embarrassingly remiss in finishing that work. Fortunately, an engineer of mine has just delivered a big customer project and, prompted by this recent thread, I today assigned her with completing the task. Within a few days, I should have comprehensive data to review. I'm travelling until I return from the upcoming AES show, but will not drop the ball again. (Or the woofer!) I hope I can provide a few other technical goodies, too, to thank everyone, particularly Tom, for your patience. -k
  8. Used, I'd look for a Beckman 320. They are really flat over the audio band. New, Fluke 80 Series III.
  9. Ideally? A "professional" card that accepts balanced inputs and high voltage levels. I have an older Antex StudI/O card and DAL Card-D that are troopers. A Frontier lightpiped to a Sonorus that is really excellent. Realistically? These days, there are a boatload of affordable pro-sumer cards sold by music stores that are far better than you need, especially since you clearly know enough to build a simple, passive front end that does a bit of signal conditioning. www.musiciansfriend.com is sure to have something on sale. As an affordable, speaker-centric measurement suite, I happen to like www.purebits.com. There are others. Honestly, we use Audio Precision's and HP's when it comes to "real" work, because none of the freeware and cheapware is truely bug-free and fast. In terms of Circuitmaker, you can just plunk in an "ideal" differential amp, and use that for your non-ground signals. Or, you can choose two test points and display A-B, though that might be exclusive to the "pro" version. Ken Kantor www.intelligentaudiosystems.com
  10. You nailed the problem on the head. Accurately modelling speakers at the listening position is a substantial technical challenge. Even without the room, it only became practical fairly recently. Add in the room and driver radiation patterns and cabinet effects, and it is state-of-the-art. That's why speaker designers still have jobs. Such as they are.... There are software packages that do pretty well, and most big speaker companies have their own creations, but I doubt a circuit simulation could do it. It's really a wave problem, and lumped parameters don't illuminate much. What simulators are for is taking the trial and error out of crossover network design, in terms of achieving a previously defined response. But what you want to feed to the drivers is another matter. This, I will opine (perhaps controversially), is why the very best speakers rarely are done with active crossovers. Knowledge and DSP are changing that, but it is still a valid observation of the past. Years ago, when I was doing R&D at International Jensen, we wrote a free-space acoustical modeller (no room, but driver and cabinet geometry) that we subsequently released into the public domain. I will try to locate a copy and post it here. Ken Kantor www.intelligentaudiosystems.com PS- Meter? How much do you want to spend? EBay is overflowing with superb meters for not so much money. I purchased two HP3400a voltmeters for about $40 each. Not a multimeter, but not long ago a gold standard in audio testing. Most of the used bench multimeters from HP, Keithly and Fluke are total bargains. What kind of soundcard do you use?
  11. Screwing around is a very educational way to learn about speakers, I think. Not everyone would pick a 3a as their test bed... but, hey, it's only a speaker. Trial and error has its limits, though, and I would recommend a few things that might help you gradually turn the experience into knowledge. 1- Keep looking for a freeware modelling program, or keep trying Circuitmaker. I got the "pro" version working on an XP Pro machine without incident. 2- $100 bucks worth of test generator and voltmeter might prove a revelation. Details when/if your are seriously considering. There are many alternatives for doing measurements with a soundcard, too. 3- A copy "The Loudspeaker Cookbook," an elementary explanation of how speakers work that can be digested with or without math. Other than that, midranges are tricky to design good crossovers for, since the circuits used for the LP and HP sections interact. And because the driver impedance changes so much over the operating band. And because of the range of wavelengths involved. And the sensitivity of the ear. Etc. Not a task I would wish on even an inexperienced pro. Not sure what your goals are yet, so I can't say much else in specific. Think about using reactive components for your shunt elements, perhaps in series with lower value resistors. -k
  12. Thanks! Easy question first: yes, turning the pots does alter the crossover point. However, the whole idea of there being a crossover "point" is quite an abstraction. The notion grew out of simplified spec sheets, and customers used to idealized response curves (smoothed, made in test chambers, made up totally, etc.) In the real world, there is a crossover "region." Every location in space has a somewhat different crossover "point." Hmmm... I guess this really wasn't the easy question, after all. Onward. I don't think I can be of much help about the 3a woofer model, at least immediately. It is highly possible that it exists in my collection, or I can get it from a friend. Unfortunately, stuff that old is buried in boxes and boxes of dead storage, and isn't practically accessible until it turns during a random search. It isn't terribly hard for me to derive a new model, once I dig up an appropriate woofer. But, you can count on that being after the Consumer Electronics Show in January! (Unless I really an even worse case of procrastination than even this.) Additionally, the AR 12" woofer parameters changed a great deal over the course of the product's life. There are an infinite number of combinations of parameters that can yield the same effective bass response. Do you know the age of yours? Lastly, do you have any electronics tools available for making basic measurements on your woofer? A test generator and decent voltmeter come to mind. Ken Kantor www.intelligentaudiosystems.com
  13. If you try to design crossovers on the premise that speaker drivers are ANYTHING like resistors, you are doomed. The whole concept of "4 ohm" or "8 ohm" speakers is anachronistic. You know those boxes they sell at Radio Shack that say things like "1000 Hz, 8 ohm crossover?" Actual measurements turn out to be 200 Hz, or 3000 Hz, or a strange bump that isn't even a true rolloff. Or whatever. Speaker drivers are complex loads,("complex" in the mathematical sense). One must do the kind of simulations you are attempting using comprehensive electrical models, or specialized crossover software that takes into account the exact woofer or tweeter you are working with. If you want to mess around with this kind of thing, I would recommend going to www.circuitmaker.com and downloading the free student version. Try several of their circuit examples, and spend a few days learning your way around the program. Once you know how to simulate basic filters and response curves, I can give you some advice about how to model actual speaker designs. -ken
×
×
  • Create New...