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Gerry S

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About Gerry S

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  1. I always felt the "bi-amp" option that ADS offered to consumers was a mistake. There is more opportunity to screw up the sound than to improve it (I once owned a pair of 910's using just the built in passive crossovers). Effective bi-amping requires pretty detailed knowledge of the raw drivers individual performance. It also requires test equipment to set amplifier gain levels, as well as the crossover frequencies and slopes. Pro's use bi-amping in sound reinforcement for increased output capability and reliability, and when the performance space has been defined. With pro use,the cost and complexity of additional amplifiers and electronic crossovers is justified over the long haul. With consumer use, I don't think it's justified, from either a cost or performance point of view. Let's assume the ADS passive crossover was properly designed, and yields what is generally acknowledged to be "good sound". With bi-amping, audible changes to the system should be SUBTLE. The primarily benefit should be less audible distortion as the woofer amplifier "clips" (overloaded) with heavy bass content. The distortion generated with this clipping is produced by the woofer(s) only, where it's mostly inaudible. It's inaudible because woofers naturally rolls off highs, and the passive crossover reduces the highs further. The trouble with bi-amping occurs when any additional filtering created by the electronic crossover upsets the INTENDED "blending" occurring between upper woofer frequencies and midrange lower frequencies. Not to mention any changes in the "radiation pattern" at the crossover frequencies. I'm not saying that bi-amping isn't a valid way of improving sound. I'm saying that in the hands of the average consumer, it's not likely to do so. Gerry S
  2. The T1030 crossover pictured above is a genuine BA part. It is a "quasi-second order" SERIES network between the woofer and midrange. With this type of network, any change in X-O values affect both the woofer AND the midrange SIMULTAINIOUSLY (because the drivers are effectively in series). It is much harder to "voice" because of this inter-dependent relationship. Note that If you disconnect either the midrange or woofer from the crossover, you will get no sound from either! The T930 Series 2 also used this "quasi-second order" configuration. I'm pretty sure the T830 Series 2 also used a quasi-second order network. The midrange and tweeters should be identical for the T930, T930 Series 2, T1000, T1000 Series 2 and T1030. There is NO "Series 2" T1030 (probably because it's hard to "improve" the T1030). Lessons learned from the T1030 development work resulted in the Series Two versions of the T930 and T830.
  3. Gerry S

    ADS L730 Mods

    As a loudspeaker designer (retired), I wouldn't do "mods" for ADS loudspeakers. As is, they are well built and well designed. Unless you possess the technical knowhow, as well as access to necessary test equipment, ANY change you make will most likely just ALTER system performance; NOT "improve" it. These are loudspeaker SYSTEMS, where each driver is meant to work with their associated drivers, and in that particular enclosure. If you change/substitute just ONE driver (woofer, midrange, tweeter), you've essentially changed the whole system (probably for the worst). Even if a driver swap is miraculously "successful", you would have to do the same for both speaker systems to get reasonably matched "stereo performance". I believe that "modifying" any loudspeaker system for personal preference can be fun. But if the mods are made to a "classic", that product is no longer a classic.
  4. Honestly, I can't remember. If I had to guess, the newer version had the terminals on the back. Here's how I would test/distinguish them just by LISTENING TO THEM (preferably using pink noise). Keep in mind that crossovers determine the "radiation pattern" where the various drivers "meet", aka "crossover". With the original, smoothest response between the midrange and tweeter is pretty much "on axis" of the midrange/tweeter drivers. When listening "sitting down" or "low" to the floor, response is uniform. However, as you stand up, the sound balance can change noticeably, perhaps by seeming perhaps "duller". That's due to a "dip" in in the response (at/near crossover) as you move up from the speaker axis. The newer version minimizes this "lobe"; not much tonal change between listening "sitting down" and "standing". Listening evaluations can be performed using just ONE speaker (instead of a stereo pair). I prefer "pink noise" as a source, since it's repeatable and continuous. Lacking that, music with mid/high frequency content should reveal differences. Listen in the "near field" (about 2 meters away) so that the drivers "integrate" fully, but before the room alters what you hear. Listening to "a stereo pair", the newer version should have a more "focused" central image with a mono source (pink noise or a vocalist). That "focus" is also better maintained as you "stand up". Again, the differences are most noticeable when listening in the "near field". .
  5. The AR 3 and 3A used potentiometers (level controls) mounted in the back of the cabinet. If your speaker has them, it may be the cause of your problems. Over time, they oxidize and become intermittent. Test them by rotating the controls while playing music with high frequency content. If problematic, you might replace them or clean them with a solvent.
  6. Thanks for the compliment, Dan. Ironically, I've never owned my proudest design ....LOL.
  7. Using sine waves in a "live" enviroment (vs anechoic) AND in two positions makes your results more a function of your test environment than the speakers under test. I'd bet you'd get MUCH better correlation/matching if you repeated the test using one location and the same amplifier channel (amplifiers can have different frequency responses between channels). I'd also suggest using 1/3 or 1/2 octave filtered pink noise (as opposed to sine waves). The "narrower" the pink noise, the more accurate the results at/near the crossover frequencies. Readily available on test-cds. As far as "imaging" is concerned, Allison acoustics never placed much importance on this quality. Instead, the priority was very broad dispersion at all frequencies. To get good "imaging", dispersion has to be tightly controlled, to get some degree of "beaming". "Intentional beaming" minimizes interference from nearby objects/boundaries, but also limits where one can sit to get the desired results. Allison loudspeakers emphasize uniform "power response" in the "far field". Speakers that image well (Snells) are meant to be listened to in the "near-field".
  8. Please refer to: Boston T1000 vs T1030 Started by morkys, Mar 16 2009 10:01 AM The driver alignment difference alone would make replicating the T1030 "sound" on the T1000 difficult (if not impossible) in the "near field". The T1000 and T1030 use identical drivers and enclosure volumes, but the crossovers are NOT interchangeable. That's because the two systems have different physical driver alignments, requiring a different approach to crossover design. As far as specifics, the T1000 crossover uses three "parallel" networks (one each for the woofer, midrange and tweeter section). The T1030 uses a "quasi-second series" network between the woofer and midrange sections, a parallel network on the tweeter. The crossover frequencies and slopes are also different, resulting in different "near" and "far-field" responses. As far as replacing caps, I don't think it's necessary. It could actually be detrimental to system performance and reliability (because of changes to the crossover frequencies). I would not operate both systems in the same room because of likely acoustical interference between the two. Also, each system has an impedance of 4 ohms at low frequencies; operating both systems at once (from the same amp) would tax the amp.
  9. I've never been a big fan of bridging amplifiers. You do get more power, but at possible expense of higher distortion. A bridged amp is less tolerable of very low impedance loads; higher current requirements can limit what's "useable power" before audible distortion sets in. In real world applications, the center channel loudspeaker is usually mostly dialog, and band-limited (no bass)...not all that demanding. Which is why the center channel speaker can be smaller than the main channels. The surround channels are rarely "on", and also usually band-limited . It's a rare movie where ALL channels are driven to "max" simultaneously. That's why those "auxiliary channels" can be smaller in output and still perform adequately. It's been a while since I compared amps but remembered Adcom as a "good value" offering high instantaneous power briefly, while Bryston has high continuous power throughout the entire range, and at low impedances. The Bryston approach seems like a "no-compromise" approach, using "stiff" (heavier/costlier) power supplies. 200 watts seems a lot more powerful than 60 watts, but acoustically not THAT great...about 5-6 db?
  10. All seem very viable. Option two sounds ideal , if only because all amp channels are literally identical, and in phase with each other. And, there is sufficient power to drive everything even under "demanding" conditions. In "home theater mode", the center channel is virtually "on" all the time, so a "large" speaker/amp configuration makes sense from a "clean acoustics" perspective. The T830 center-channel option is a good compromise between using a "small" speaker (which can distort at loud levels), and a third 1030 (which is overkill, IMO) ! In stereo mode, the 1030's do all the work, as they should. Bi-amping and subwoofer use is "optional"; audibly beneficial only under demanding circumstances. Bi-amping isn't "necessary" if you don't hear distortion at the playback levels you are comfortable with. Normal -sized/conventionally configured amps are adequate for most program material. Virtually all "normal" listening is usually in the milli-watts/channel range, so even 60watts/ channel is a lot. Those "peaks" is where those extra watts come in handy. The use of a dedicated powered sub crossed over @ 80 Hz makes bi-amping less "necessary". Adding bi-amping and subwoofers to a system that's "good" to start with is like adding turbocharging to a car under "performance conditions". In normal use, you don't need it. When needed, it's operation should be seamless (unnoticeable).
  11. Regarding T 830: no change in drivers, just crossovers.
  12. To the best of my knowledge, there was/is just one version of the T1030. The different "labeling" may reflect a marketing decision. To elaborate, it is "4 ohms" at low frequencies (the power hungry frequencies), but a "nominal" 8 ohms over the rest of the range. Many (most?) speakers have this characteristic. If you look at a "impedance curve" of just about ANY given loudspeaker, it varies with frequency...not just a "single number".
  13. The meter reads "open" because the signal being fed into the speakers is "dc" (or close to it). With the straps removed, the midrange/tweeter section has capacitors in the crossover to PREVENT low frequencies from reaching the drivers (or they will be easily fried). So, at LOW FREQUENCIES, it is "open". If you were to feed a musical signal, you will hear music (without bass)...obviously NOT "open". The "nominal" impedance is 8 ohms (most of the frequency range), the "lowest" is 4 ohms in the bass section (the power hungry frequencies). "Bi-amping" permits using two "low-power" amps as opposed to a single humongous one before audible distortion sets in. When the woofer amp channel "clips" (runs out of power), any high-order/high frequency distortion generated by the clipped amp STAYS in the bass drivers, which by their very nature has trouble reproducing this distortion. If these same distortions were generated by a single amplifier, you would clearly hear them through the midrange/tweeter drivers...very unpleasant-sounding (and potentially dangerous to the midrange and tweeter)! I personally would use a powered sub (I use a HSU product) to reproduce the power-hungry very low frequencies (80-100 hz) instead of bi-amping.
  14. I did the crossover design for the T1000 series 2 AND the T1030. (The original T1000 was done by BA co-founder Andy Kotsatos). On much music material, there is not a DRAMATIC difference between the original T1000 and the Series 2. That's because it's hard to dramatically "improve" on a product that's very good to begin with. The drivers for both Original and Series Two are virtually the same (if not identical). The crossover frequencies are NOT "identical", but close (I don't know/remember the specific frequencies). Still, there is enough of a difference as to be audible on lots of pop/rock material (MY preferred genre) to warrant the new model designation Series 2. The T1030 is a VERY different sounding speaker, especially in the "near field". They will "image" better with recordings that have a significant left/center/right channel mix-down (pop/rock/vocals). This assumes you are willing to take pains to position the speakers properly, then listen in the "near field". The 1030 crossover has a different topology compared to the T1000 because of it's different driver configuration (tweeter BELOW the midrange). It can also handle more "instantaneous peak" power before distorting (especially on high level "bass whacks"). Because of the different driver configuration between the T1000 (Series1 and 2) and the 1030, you cannot/should not swap crossovers.
  15. The movie "The Conjuring" shows (a glimpse) of what I think to be a vintage AR (2ax or 5) in a old house. It appears about half-way into the film. The movie is pretty good too (especially for a horror flic).
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