Sloped baffle

Lewinskih01
....What would be premium brands sound-wise?....

Well not sure how many of these brands are still accessible to the public but.....Scanspeak makes some very good drivers, another excellent brand for woofers is Audax & Peerless, yet another brand for mids & tweeters is Morel & Eton. I'm sure that there are many others.

BTW, I never thought about drivers not being time-coherent..... I thought time misalignment was between/among drivers.

yes, you are right - drivers in & of themselves are not time-coherent. Drivers are linear (wide frequency range of operation) well above the frequency at which you cross them over. Using such drivers greatly helps to manuf time-coherent speakers because the driver itself does not come into play, it's just the electrical x-over (or in your case the electronic x-over since you will be using DSP).
yes, you are correct - time misalignment is between/among drivers.

But you made me remember about Meridian's approach. I will look into it. I believe they deliver a digital signal to the speaker and then convert it to analog inside the amp. I'll check if they have processors that deliver multiple analog channels,

:-) that's the point of these forums. Yes, you are correct - they do deliver a digital signal to their speaker & convert it to analog inside the speaker box. Pretty complicated stuff w.r.t. all the signal processing they do. How long has Meridian in business? I would say some 40 years. How many people own & appreciate Meridian speakers? I personally don't know any. Doesn't mean that there aren't any/many. Also check into Emerald Physics' methodology.
Just a thing to be aware that you are putting all your trust into that DSP software & the handles it gives you to vary x-overs & slopes, etc. I hope that you like the exact flexibility that is given to you & that you are not saying "I wish this software had this other XYZ flexibility".
The DSP signal processing is touching your music signal in a very fundamental way in that the entire music signal has to go thru the DSP before you can hear it. Same deal with the passive x-over. But the difference is that you change the quality of the cap or the inductor or the hook-up wire & you can change the sound to your liking. It appears that it's not that simple with the DSP software - you cant go in there & change the code. Or, maybe I'm not thinking of this correctly?
So, if I'm envisioning this correctly - computer digital out runs into the DSP software which breaks the audio signal into highs, mids, bass. You get 3 digital streams now. You feed these 3 streams into 3 identical DACs or 1 Pro quality DAC able to output 3 analog streams (one box would be better as everything sits in 1 chassis & has a better chance of being matched to the other analog stream). Then 3 analog streams into 3 power amps - you need to match these very well too: same input sensitivity, same gain, same sort of clipping algorithm, same dynamic headroom extension, same power output capability, same current source/sink capability.
There are a lot of variables to contend with. That's why I wrote earlier that it's a huge undertaking. You'll have to become very savvy with DSP (which is discrete-time) & analog signal processing (which is continuous-time).
There aren't many people who make speakers using this technique - Meridian, Linkwitz DIY, Emerald Physics that I can think of. maybe this is the wave of the future???

@Nrenter ... you make a fair point. My non-techie surmise that the "non-linearity" you described is the reason why manufacturers use multiple drivers. I suspect that in making design trade-offs, the characteristics of the particular driver are chosen to optimize performance within the chosen pass-band.

Sorry to be tooting Paradigm's figurative horn again, but from a non-techie's perspective the drivers used in their Signature line might address some of the nonlinear concerns you mentioned. The tweeter uses an ultra low mass and hard beryllium dome. The motor uses neodymium magnets rated at 20,000 gauss at the voice coil gap .... (btw, is that a lot??). Plus ferro-fluid for cooling and low distortion.

Similarly, the mid driver uses an extremely light and strong cobolt/aluminum cone. The motor uses neodymium magnets rated at 15,000 gauss at the voice coil gap. Plus ferro-fluid for cooling and low distortion.

And that's enough tooting for Paradigm. I don't work for them and they certainly don't pay me.

But another manufacturer who seems to put a lot of thought and effort into their drivers is Magico. Been doing a lot of reading about their S speaker line. Build quality seems superb. And there are many other fine manufacturers who put their heart and soul into what they design and build.

@Bombaywalla -- got a Q. Do most drivers remain linear through their selected pass-band with respect to time delay. In other words, when pulse testing a speaker, is it just the X-over that causes the tweeter to respond first, followed by the midrange, and then the woofer?

Regardless of the answer, if a manufacturer chooses to use a high order X-over for design considerations, is there anyway to compensate for the time delay phase distortion through the pass-bands of the drivers? Or is that analogous to unscrambling an egg. That is the damage is done ... no fixing it with more passives.

Not sure if this hit the point, but I own a self powered Paradigm subwoofer. The sub permits adjustments for loudness and frequency cut-off. But of relevance here, the sub permits phase alignment adjustments and I assure you ... it makes a big difference. Suck-out or no suck-out at the X-over point (35 Hz).

Cheers,

Bruce

07-06-14: Bifwynne
......The tweeter uses an ultra low mass.....
......Similarly, the mid driver uses an extremely light and strong cobolt/aluminum cone.....

Bifwynne, do you see what's happening here in the Paradigm drivers?? they are being made light-weight, rigid. Which other driver by the very physics of is light-weight? An electro-static panel driver. You make it rigid by putting a stator around it (like Martin Logan & SoundLab). You'll find that the ESL drivers are linear (flat freq response) over a very wide freq range & that really helps make ESL time-coherent speakers. Not all of them but many of them. The cone drivers are all aspiring to become like ESL drivers - light-weight, rigid.
The hope is that the drivers are out of the pix when the signal gets crossed-over.

@Bombaywalla -- got a Q. Do most drivers remain linear through their selected pass-band with respect to time delay. In other words, when pulse testing a speaker, is it just the X-over that causes the tweeter to respond first, followed by the midrange, and then the woofer?

Bifwynne, the x-over is electrical & the drivers are mechanical (the spring & weight analog that was in one of Roy Johnson's papers that Almarg pointed all of us to in a post w-a-y earlier). So, there is some phase delay thru the electrical x-over as the signal gets low-passed, band-passed & high-passed but there are delays thru the drivers themselves as well. The fastest to respond is the tweeter. More delay thru the mid & the most delay thru the woofer driver. Every driver is flat over a certain freq range before it rolls off. How wide that freq range is depends on the driver was made by the manufacturer.

is there anyway to compensate for the time delay phase distortion through the pass-bands of the drivers? Or is that analogous to unscrambling an egg. That is the damage is done ... no fixing it with more passives.

no, I believe that there is no way to fix this - once the transducer has converted the electrical signal to sound pressure it has already imparted its signature onto the sound pressure wave. The damage is done - I cant grab the air in the room & push it back onto the driver to give it one more go-around nor can I take that air in the room & convert back to an electrical signal & push it back into the amplifier for another go-around. Impossible to do. Your analogy of unscrambling an egg is a good one.

Not sure if this hit the point, but I own a self powered Paradigm subwoofer. The sub permits adjustments for loudness and frequency cut-off. But of relevance here, the sub permits phase alignment adjustments and I assure you ... it makes a big difference. Suck-out or no suck-out at the X-over point (35 Hz).

Bingo!! So, you have experienced some effects of phase alignment & seen the dramatic effect of it. You've been holding out on us, Bifwynne! LOL!! :-) OK, so you now know just how important phase is to the bass response. Imagine doing this over the entire audio band? You are now trending towards a time-coherent speaker....
You see something like this in speaker time-domain response measurements in Stereophile & SoundStage where the woofer is in phase or out-of-phase with the tweeter. you can see the suck-out in the impedance & phase curves.

For individual drivers, cone woofers have voice coils and are inductive. So, yes, they do have phase shift as frequencies increase. Some are more inductive than others. Even dome tweeters have some degree of phase shift.

A first order, parallel low pass is an inductor coil with phase shift, typically 90 degrees in the pass band and more beyond. They're cumulative and that's called acoustic slope. In a 2-way, there's also baffle step compensation, which inolves a bigger inductor well into the pass band, causing even more phase shift, maybe another 90 degrees more or less. And that's just first order. Add another 90 degrees for every order over that. Basics 101.

In the next class, we'll discuss capacitors, high pass filters, zobels, notch and contour filters, all involving various degrees of phase shift. Then, on to impedance phase and reactance. Your homework is expected and there will be a test.

@Ngjockey ... let me try to unpack what you just wrote. Let's assume we have a single dynamic cone speaker with a pass band of 35Hz to 20K Hz. Let's forget about high frequency beaming and cone breakup. Just assume this hypothetical speaker has a flat frequency response within its pass band, as measure on axis. Obviously no X-over needed here.

Now ... like all dynamic drivers, we have a voice coil, a spider, magnets, and so forth. Let's focus on your comment about the voice coil being inherently inductive. Makes sense. After all, we have a wire coil moving in a magnetic field, producing voltage and its own magnetic field. The faster it moves, presumably, the more voltage and back inductive reactance to the input signal.

Now, if a complex signal was fed into the speaker, would there be phase shifting with respect to the higher frequencies as compared to the low order fundamentals? To be more specific, say the signal was composed of a 100 Hz fundamental, plus "n" number of harmonics into the high treble. I assume this complex signal could be visually reproduced on an oscilloscope.

If the driver's output was compared to the input signal, would there be some sort of harmonic difference between input and output signals? Would the speaker's lack of inherent phase coherence be the cause of this distortion? Would this phase nonlinearity be caused by the inductance resulting from the voice coil moving in the speaker motor's magnetic field??

Let's assume the answers to my questions are -- yes?? Is there a frequency range where a speaker is phase coherent, or does phase nonlinearity increase as a function of frequency ... period??

If the answers to all of these questions are -- yes, then it seems to me using 1st order X-overs and sloped baffles is at best a rough justice engineering response to a problem that is inherent with dynamic speakers that use voice coils.

So ... where do we go from here?? Magneplaners, ESLs??

Cheers.

P.S. Bombaywalla and Al, feel free to chime in. I think I'm getting tangled up in my shoe-laces.