DrWho

" I am talking about the speed in which a driver can go from rest to excursion and back to rest. " *sigh* That's also called frequency response. Honest.

Perhaps the physics are different over there in Indy?

Speed and frequency response are the same thing. Why can't we just use normal terms? I could be shortsighted here, but you can't talk about mass outside motive force and cone stiffness. High excursion designs exist with high frequency extension and equally stiff diaphragms. And physics dictates that low displacement = no bass. Voicecoil magazine is often publishing exciting Klippel results. The legacy of PWK was engineering driven designs. We don't want a speaker designed for a specific application, or based on some weird philosophy about the limitations of drivers from the past. Nor does it matter what the competition is doing, or what marketing label gets placed on a product. The physics are a constant. Yes, by all means keep the cool marketing stories and emphasis on heritage, but at least be authentic about it. Btw, there's a reason the "evil" consumer stuff focuses on what they do today. Achieving those goals with greater fidelity is what high-fi is all about - not arrogantly dismissing it. Btw, my intentions here are to provide some honest feedback. Not trying to dig anything through the mud. Quite frankly, I've realized the design targets here aren't going to emulate the performance of the K48 in a similar application. I bring it up because it will disappoint a lot of my peers that I think fall into this target market. Not everyone listens to old jazz on vinyl. Klipsch hasn't released it yet so there's still time. The thing is, my peers haven't drunk the Klipsch koolaid...

The closed backs aren't the same thing as false corners. The flare needs to extend beyond the front of the speaker. Not just that rear corner.

Hah! I've heard those already. I really want a 15" 2-way with hypex amps and active xover. I've been hunting this down for many years now - that might be a fun forum search to find my first mention of it. I never thought Klipsch would ever come out with something like the Fifteens, but here they just announced it. No way! The thing is, I want it to be voiced like the ki396. None of this "no bass, SET like, tone" nonsense. Those are words I hear at the local audiophile boutiques when they're trying to overcharge for crap sound. I'm not saying that's the case here, but it's made me want to demo it first. On the topic of mumps....Why isn't this just standard approach on all the horns now? It's not like it costs more to add that shape to the molds. Yes, I'm totally being an annoying audiophile here, hah! This thing is so close to my ideal setup that any shortcoming would be so disappointing. I've wanted something like this so bad I've set out to build my own, but I could never bring myself to shell out for all the tooling costs. Plus, you guys are better at this stuff. This is a product niche that's been seriously lacking, but if it requires a subwoofer then it totally ruins the simplicity story.

You can always add "false walls" to the khorn....or basically build a room corner for them to sit in so that the flare of the bass bin is finished without using your room's corners. And then you can place them anywhere in the room. If you're going to pull the khorn out without the false corner thing, then you should just get the lascala since it sounds better in that configuration. Just make sure you get a potent subwoofer to make up for that bottom 1.5 octaves you're missing. Or just get the Jubilee - getting a passive xover made for you is easy if you don't wanna deal with the active route.

Is this new Jainbaby person an actual engineer at Klipsch, or a sales/marketing dude? Or maybe a manager? I'll just come right out and say that description of the vision for the Fifteens is incredibly disappointing. Like it seriously sucked out all my excitement, and was even insulting. *sigh* And to think I was going to buy these speakers without ever hearing them...I suppose I should thank him for the heads up.

Actually went ahead and did a google search: http://www.diyaudio.com/forums/tubes-valves/243950-vacuum-tube-spice-models.html https://gist.github.com/chanmix51/6947361

Interesting. Do you know if anyone has created any SPICE models for the tubes you're looking to use? That might be a cheaper way to experiment with voltages and whatnot...

A couple thoughts: Different speakers may have different distortion characteristics. The microphone will be contributing some of its own distortion. The preamp will contribute some of its own distortion. Microphones respond to particle velocity and pressure - not just pressure. Room modes can play weird tricks in that regard. Notice how test tones sound very different as you move your head around? Even if the mic stays put - the speakers are in different positions so the location of peaks and nulls from the room modes will be different. This will affect distortion numbers greatly because the distortion products are calculated relative to the fundamental - and the room mode behavior also applies to the distortion frequencies, but it's going to be different because the wavelengths are different. If you're trying to quantify the distortion benefit of the lazy triamping, then you'll really want to be using the same speaker with the same mic and everything at the exact same acoustic SPL. It's more work to do the A/B, but it looks like you're already really diving into this. All that to say, I think there are too many moving variables to draw firm conclusions from what you've presented thus far. That's not to say it isn't real, but it's within the margin of the variables that have been moving around. Now that said - amplifiers definitely create IMD products and they will go away when using a single tone. The IMD products only occur when there is a non-linearity in the system - and the magnitude of the distortion is a function of the relative impedances. A perfectly low output impedance amplifier will drive a perfect sine-wave into a diode. However, if you put a perfect resistor in series with that perfect amplifier, then the diode creates distortion. I can create a quick schematic and simulation to demonstrate the idea if that's not clear. The back EMF from the speakers is working against the output impedance of the amp. When you have two tones going, the "bias point" for the higher tone is modulated by the lower tone. If the output impedance changes with the shift in bias (which it does ever so slightly for transistors), then that is a non-linearity that causes the back EMF to get rectified. I prefer to think of it as the output current modulates, but it's the same principal. This is why I don't like to have any impedance between my amplifiers and drivers. Any non-linearity in the system increases when the output impedance increases. It's just ohm's law at that point. Side note: passive xovers work on the principal of adding series impedance to block frequencies, which is effectively increasing output impedance over certain frequencies - and therefore increasing distortion (even if the xover components are perfect, which they aren't). That's why I don't like passives.

Do you have a way to change the electrical signal without moving the speakers, and the mic? And do you have a way to guarantee exactly matched gains? Distortion is tricky because it's never flat versus amplitude. There's a lot of setup involved to exactly match things. There's also going to be a lot of variation between speakers. Does REW have a way to sweep distortion versus input signal? Seeing the curve helps account for minor gain differences.

Oh, and how are the drivers wired inside? Are you just removing the binding posts?

What are the active xover frequencies you're using right now for the lazy approach?

Could you put together a diagram showing the difference between A and B? Is the improvement from "fool's biamping" with an active xover operating outside the passive xover? (don't be offended by the term...at least I think it's an accepted term for using multiple amps with passive xovers instead of active xovers)

That doesn't explain why humans jump at any opportunity to understand even the most primitive types of life outside our planet....why would you expect anything else from other more intelligent forms of life? Or are you saying it's not intelligent to look for primitive types of life - I could agree with that sentiment.

I am so immensely grateful to have a few mentors similar to what you had with Paul. However, they are always encouraging me to stand on their shoulders and improve on their years of experience. They even let me argue with them and learn things the hard way. Granted, they're nowhere near as awesome as PWK. He (Paul) was off the charts brilliant and way ahead of his time. I'm still amazed at the beauty of his engineering. Maybe it's different being mentored by someone with an unobtainable gifting? Btw, I think many here realize your own gifting too....who was it that pushed Paul onto Tractrix? Ya sure, it took a team to present it in his language, but that initial spark of imagination certainly shouldn't be ignored. Not saying that gives you or anyone privilege to "rip apart" Paul's designs, but I think you probably understand best the method behind the madness. I think it's testament to Paul's foresight that his Heritage speakers still sound so good today. I could understand preserving the original designs. Does that mean there couldn't be new products inspired by a Roy standing on Paul's shoulders? I like the way you voice speakers - which makes me more excited about the Forte III. Although that Fifteens system is exactly what I've been dreaming of for several years now...so I'll probably buy one of those once life starts to settle down a bit.

I'm confused by this - and not at all being judgmental either. Why would Paul being such an open-minded person have an emotional attachment to outdated design philosophies? Isn't every engineer (including Paul) elated at the thought of getting a second chance on an old design, and incorporating all of life's experiences into the next version? Wouldn't it be honoring of Paul and his engineering brilliance to incorporate as much experience as possible into every design? I'm often told I'm still young and don't understand nostalgia yet, but isn't there a deeper nostalgia in understanding the process and philosophy behind an object, rather than the object itself? I get the impression that if PWK was building a speaker today, that it'd look a lot like the skunkworks Jubilee that Roy put together. Would PWK be building something else? Btw, I'm super excited about the Forte III. I finally have a new speaker from Klipsch that I can recommend without apology. The Forte II is definitely in my top 3 favorites from Klipsch. I'm sure the Forte III is gonna move up into that list. Where will they be on sale? And where can I send people to go demo them?

And Hypex amplifiers....super cool.

I just noticed they did make a 2-way called "The Fifteens" - now that's way super cool. Any discussion about their pricing? Interesting that the Forte got the mumps but not the fifteens?

Ya, I'm surprised and even disappointed it's not a 2-way. If there's a fancy custom phase plug, then maybe there's an aftermarket mod to drop that tweeter and make it 2-way. Yep, already talking about changing it and it's not even shipping yet I would seriously buy a pair though if the 2-way was as simple as disconnecting the tweeter and adding a little processing to that "MF" unit.

Since when did "no fun" become a valid reason not to do something? News shouldn't be mixed up with entertainment.... Btw, I agree about C-Span....that was a breath of fresh air when I discovered it.

Youthman....you really need to read this thread: http://www.avsforum.com/forum/155-diy-speakers-subs/837744-double-bass-array-dba-modern-bass-concept.html DBA is the way you wanna go. Your room is almost perfect for it - and with an IB arrangement you'll get some serious flexibility with the manifold openings. One thing about IB subs....if at all possible, make sure your drivers are mounted horizontally. This removes the effects of gravity from affecting the resting position of the voice coil in the gap of the motor. Also, you can have the basket side of the driver facing outward. If you have one driver mounted normally and sideways in a manifold, then you can have the other driver mounted with its magnet in front of the other driver so that they're dual opposed. This arrangement will cancel a lot of distortion products. It would also allow you to mount your manifolded array closer to the DBA ideal (I think). Btw, the other half of the DBA concept is to have a matching array on the rear wall - which is set up to "catch" the front wave and cancel it out. This just adds to your total displacement capability of your system. One other concept - "IB" is really just a large sealed cabinet and should be designed like every other sealed design. What I mean by this is that sometimes a slightly smaller rear volume will actually net you more output and lower distortion. You also need to deal with the standing waves that resonate behind the IB. These waves make their way through the diaphragms of your drivers - even if everything else is perfectly sealed up. This could be as simple as a ton of sound absorbing material behind the IB. You'll also want to avoid resonances that are in phase from both chambers (the room and the rear chamber) from totally unloading the driver. Lots of arguments to controlling the rear volume of the IB - and the thing is it doesn't affect your LF corner by much at all. If you're really concerned, then a little EQ down low can easily compensate. Good luck finding a processor that will do it though.

Depends on the amplifier output impedance Several of them flea powered amplifiers are matching output impedance to the source impedance (or at least they think they are). This is of course obfuscating your point, which isn't intentional. Good amplifiers are constant voltage sources and that's the assumption throughout the entire audio path. For some reason some audiophile brands decide the constant voltage encoding no longer applies. Of course those are the same guys complaining about swamping resistors that flatten their frequency response. You could always go to reactive components to flatten the impedance response - and then theoretically there's no real power loss. That might require unobtanium parts though. I've not bothered running the numbers because those passive parts are too non-linear for my taste. I like that clean clinical sound

Did PWK ever design amplifiers? There is nothing in the science of amplifier distortion that says higher power necessitates higher distortion. Yes, distortion increases near the limit of the amplifier, but every amplifier has a sweet spot at a different power level - you simply design the amp for the application. In fact - if we were to go in any direction - I would say increasing the voltage swing requirements of the amplifier is of great benefit to the amplifier designer - especially if we're talking active crossovers. All of these ideas need to be analyzed from a system perspective. I've grown to dislike these articles from PWK because it's intentionally obtuse to make a very narrow point. And that narrowness demonstrates a totally wrong way to think about system performance. I know PWK had a better understanding, but you guys use these articles within the narrow perspectives that were presented - and that leads to incredibly unnecessary conclusions. Btw, it's the dumping of energy in Class A amplifiers that makes them such low distortion. The same principals totally apply in other areas of electronics - especially in situations where nonlinearities are present. Speakers and microphones are the two most nonlinear systems in audio that we can't avoid... The electronics side of things is very straightforward. All that to say, there are a lot of amplifiers that are sensitive to the load impedance. There are also a lot of amplifiers that are not very sensitive at all. Some have power headroom - some don't. Just because your favorite amp can't drive a swamping resistor load doesn't mean there isn't sonic benefit to having a flatter load impedance. Likewise, flattening the load impedance doesn't necessarily change the sound in any appreciable way either. These are systems. Looking for rules of thumb to justify your decisions is just odd. Don't be odd. It's bad for the hobby. Oh, and stop wearing sweatpants too. The only way to experience the true plushness of a comfortable chair is to enjoy it in the nude...... Edit - I'm looking at this from a perspective that you pick the speakers first, then you find the amplifier that mates with your listening habits and nuances of your speaker. You don't start with the amplifier selection. It's worth mentioning though that the ideal amplifier is likely different for a passive xover versus an active xover setup.

A lot of the newer stuff is putting all those woofers in parallel, which means the AC impedance is dipping pretty low at some frequencies. So with a 2.83V measurement signal, you're often getting a lot more than 1W into the speaker. Some people conduct true 1W measurements (based on the minimum impedance), which in turn lowers the voltage used in the test and therefore reduces the SPL measured for a "1W/1m" test. Klipsch has been pretty good about specifying a 2.83V source signal. To complicate all this further, using a broadband signal (like pink noise) means the energy is spread equally across frequency - which means the impedance dips at the lower frequencies aren't affecting the total sound energy very much. Due to the higher impedance at higher frequencies, a 1W broadband signal could yield an even higher total SPL rating than just a straight up 2.83V signal. This kind of testing would be really hard to control though, but I bring it up just to highlight that higher frequencies dominate the total sound energy of a system (by factor of the square root of frequency). It's also worth noting that measuring SPL at 1m isn't a very good test because you're in the nearfield behavior of the speaker at that point - which will skew results even further. A 10W/10m test yields the same number as 1W/1m for a truly spherical source. This has become a somewhat newer "standard" for measuring sensitivity. It's probably better to say that's a more common trend. Very large line array PA systems would be another animal entirely and should probably be measured even further away 100W/100m? I've see a rule of thumb for 10x the acoustic size of the speakers (so if your speakers are 1m tall, then measure 10m away). Getting back to the real world - what exactly are people doing with this data? The only thing I use sensitivity numbers for is to help with amplifier selection.