Current Trends in multi thousand dollar speakers
Re: transmission line speakers, mechanical & electrical modelling is now available for quarter-wavelength speaker design. Never tried it -- but thanks to a few audiophile engineers it looks like we've taken a large step forward from the trial & error situation of yesteryear. D Dlugos' site has general info on the subject and, of course Martin J King who actually developed the computer-based mechanical modelling. Cheers |
In my opinion, and with 50 years of experience building speakers (mostly by the old fashoned trial and error method) transmission lines are the best boxes, but as sean says are hard to get right. Sealed boxes are almost idiot-proof, and so, in the real world, in most cases will outperform TLs. Furthermore, because of their gradual and well controlled roll-off, electronic equalization is effective. The key to speaker building is "don't screw it up". It's too easy to do that with a TL. |
Phew! Lots of reading.... Glad to see that "Q" was discussed. Balancing enclosure size, driver characteristics, vent frequency and sensitivity is certainly an art. Not having heard the 20T, I would nonetheless find it a bit difficult to believe that Mike Kelly would purposely let a bloated high Q speaker out the door at 23k. Likewise I've learned that JA's cut 'n patch fr curves can be a bit misleading...as are most such attempts at describing response in a real environment. My assumption is that the 20T is for LARGE roms, where the big bass plateau can be appropriate. These ARE big speakers in my book.... I think it may be a bit too easy to criticize vented designs. Certainly if the vent frequency is low, and the driver well-controlled with a very low Fs, in an appropriate nonresonant enclosure, excellent results can be had. I understand the nherent problems, yet had moderate success loading a 3-way (8+5+0.75, vent 32-35Hz) a while ago. The problem wasn't so much the bass response, but other issues higher in frequency (matching driver sensitivities with loose OE specs!). Yet the speaker did have characteristic "vent" sound. Maybe we're all too much used to it, and Sean is partly right.... So it was quite a shock to hear how clean and tight the response is from my now-3yr old Verity Ausio Parsifal Encores, for example (8+5+1). Stunningly fast bass response that matches its incomparably-quick midrange. I asked Pelchat et al at VA how they did it, and mentioned that the Encore was predominantly about getting an extremely "fast" woofer custom spec'ed from Dynaudio, for which they pay a fortune. Sounds it...really hard to believe there's a lagging vent huffing and puffing in this design.... I suspect a low Q keeps things quick and flat, too, as I measure fla response to 30Hz in-room, falling precipitously below that, of course, as is typical of a tuned vent. You should listen to this speaker, Sean, before castigating all vented designs further.... Comments about boom-cha favored response (the old West Coast saddle-curve...aka Bose?) I find intriguing, and can't comment upon whether current designers are influenced by unnatural bass level pop music tastes.... Some posters correlate that flat bass frequency response is somewhat correlated with price. certainly this is only slightly true, vis a vis enclosure size cost. It's really not harder to design a $1k speaker with a reasonably flat and "chosen-Q and vent freq" than a $20k one. Thiele/Small, Q, vent geo, etc., are givens, so Aeriel's $23k speaker doesn't have smoother bass than the $6k Legacy for THAT reason. Hell, my Spendor 3/1p ($1400) have a nice smooth bottom. It's just good design.... There's too much to comment on here later.... Cheers. Ern |
The fact that transmission lines are hard to execute well doesn't mean it can't be done. Indeed, it's being done right now by several manufacturers. And having built more bad transmission lines than you can shake a stick at, even an amateur like myself has learned a few tricks. I've had fairly low-Q sealed enclosures and transmission lines side-by-side using the same drivers (KEF B-110 woofers, Dynaudio D28 tweeter), and even an amateur-built TL was (in the opinion of classmates who participated in informal blind listening tests) considerably more realistic sounding. Regarding "pressure relief" enclosures, yes Sean I was talking about vario-vented (and homemade resistive vented) enclosures. I didn't use the term "aperiodic", as that term can also be correctly applied to a Qtc = .5 sealed box, and I didn't want to confuse things. If excellent power transfer in the bass region (as indicated by a very smooth impedance curve, especially around system resonance) is a high priority, and if the only advantage of the sealed box is extreme ease of design, then why not consider the transmission line, or for that matter its ultra-simple cousin the pressure-relief box? They have much better power transfer - and by implication better linearity - in the bass region than a sealed box does, if indeed the impedance curve is an accurate predictor. Not trying to be confrontational Sean; just tossing my favorite enclosure into the ring against yours.... Cheers, Duke |
Ernie: I am well aware that there are exceptions to the generalizations that i've made. From what i have seen and heard, they do exist. They just aren't commonly found or available due to going against the grain of the marketing hype that currently exists. Dealers don't want to carry products that don't sell and these products don't sell because the average consumer hasn't been educated or know what to listen for or how to listen for it. For this, i blame the audio industry and the press. They are responsible for the "trick bag" that the "high end" audio industry has worked itself into. Due to their marketing games and the profit margins generated from under-designed products, the average consumer can't tell the difference from a "salon" speaker to a Best Buy speaker. That's because they all demonstrate severe forms of non-linearity. The only differences that they can tell is if one is louder than the others and if it produces more bass. I also forgot that they know how to look at the price tag, which has them scratching their heads and asking why they should spend THAT much more without getting measurably superior performance. Duke: Given proper design, a TL will always be larger than a sealed design. To most people, size counts. Regardless of how many advancements have been made in TL design, they are infinitely more difficult to design / build / manufacture than an equivalent sealed design. Since manufacturers and DIYer's are less apt to venture into such waters, i've tried promoting a design concept that is both simple and cost effective to work with and produce while offering excellent sonic performance. As i've mentioned before, i don't consider the simple sealed box to be the ultimate in design. I do consider it to be the best bang for the buck with the least skill and knowledge required. As Mr Dartford stated, the less potential to screw things up ( i.e. the simpler that you keep them ), the more likely you are to achieve a higher percentage of success. Once one has achieved a high level of succcess through following sound ( as in "proper" ) design & engineering practices, refining the basic design and striving for the highest levels of performance enters into the world of diminishing returns. The last few percentile of measurable performance tends to cost more than what it would cost to build another system of similar stature. As such, i would rather see folks get 80% - 90% of the performance out of their systems at a reasonable cost than to see them pay exhorbitant amounts for much reduced performance. The fact that many end up doing the latter rather than the former due to being fooled by advertising and marketing trends makes it harder to recruit civilians and keep this industry strong. It is difficult to justify added ( let alone exhorbitant ) expenses when the ends don't justify the means. As with any type of system or project, should one choose to seek a higher level of performance than covering the basics with good design principles and proper implimentation, they should bring their wallets and valium with them. It is a steep slope that will have one stepping into uncharted territory. That is, as far as most audiophiles and even most "pro's" are concerned. As such, getting past the marketing hype and high prices is only a small portion of why i promote sealed designs as heavily as i do. The fact that they have the potential to perform in both a measurably and sonically superior level compared to 95% of the designs out there while taking up less physical space could only be considered a benefit. Either way, people can buy / build / spend their money on whatever it is they like. As i've said before, there's no sense in catering to someone else's preferences. As i've also said before, those that are interested in achieving optimum results without spending maximum cash need to educate themselves on the subjects. The more that an individual knows, the less likely that someone else ( me included ) is to steer them in the wrong direction. Sean > |
