the ancient urge to build a dual-woofer three-way

Prime Minister

Site Owner
Staff member
Hmmm.
Could you build me a mid-range box to plonk on top of my speakers for a test? Not a cheap test, but an interesting one!
 
Sorry, I didn't mean to be so abrupt. Just me, the #1 priority is getting believable vocals at realistic levels. Again, just me, lower levels are of less interest because, to me, they sound distant or miniature. I guess it comes under the objective: to sound exactly like the real thing.

I think that the large driver two way is really a work-around for the problems that occur in three ways. Ideally, for midrange reproduction, you'd like a coercive motor, very light moving system and very soft suspension. You don't need excursion. You do need fine resolution around the center of rest. So you'd think that the problem would be easy to solve, but no. It's so darn messy that guys, somewhat sensibly, have pushed forward with the two way idea. And our perceptions do tell us that there's a "rightness" to the two way that often lacks in three ways. So, yeah, big woofer two way, I get it, like it.

So what's so tough about the three way? It's not in obtaining great transducers; there are plenty. The problem is the passive bandpass filter. For a for pole bandpass you'll - at a bare minimum - have this:

View attachment 16303


Without dragging thru all of the details, this circuit is your defeat. And the parts, if you use good ones, are gonna cost more than the transducer. So, yeah, put that mess up against your much simpler two way and you're going to pick the two way.

Most guys have never heard a great midrange driver without a passive bandpass in the way. So, yeah, the preference for two ways is pretty well ingrained and quite understandable.

Back in the day, I worked long and hard to execute first order bandpasses. One C, one L one R. I'd like to think I pulled it off. But you can count on one hand the number of designers who managed to make that topology work. Richard Vandersteen, Jim Theil. That's about it, because it's unbelievably difficult.

Fortunately, and HALLELUJAH, we're moving past this stumbling block and into a world where three ways and four ways can exceed anything that can be done with a two way. That said, yes indeed, two ways can also be better than they've ever been, too.
What percentage of your input power does this network eat. I bet about 2/3 maybe more. Three and four way passives that eat 90 % are not unheard of not to mention that they eliminate any damping.
 

Pat McGinty

Senior Member
Kluge-o-rama! I don't think either of us wants to find out what an asymmetrical pseudo MTM sounds like. Just me, MTMs ALWAYS sound spooky in the vocal range. You'd fuss with the filter for days and finally give up.

I think that if the objective is an extreme performance low level thingamajig - you'd want to start with a size and money budget and clean sheet of paper. That might be interesting and certainly is very do-able, but I have reservations about the demand for such a thing? I mean, my experience over recent years is that that particular crowd is knee-jerk adverse to both dsp and class D.

I'm finding that maaaaaaybe one in twenty mainstream audiophiles can be persuaded......and it's an awful lot of work that I just don't have the patience for. The experience is terribly repetitive. The most fertile ground is actually among the HT dudes. Tell them: "Latest super-zoomy digital technology" and they're raring to go. They do not want yesterday's stuff. I hate to be so pecuniary, but there's only so much time.

In the back of my mind for several years has been an executive desk top system with performance that kinda overlaps with this idea. Tiny output at close range but extra-extra nice. That idea usually puts the LF and electronics in the footwell to keep the mains as tiny as possible. That thingy would need to sell as a niche luxury product - a reward for execs who can flaunt it by playing music while working.
 

Pat McGinty

Senior Member
What percentage of your input power does this network eat. I bet about 2/3 maybe more. Three and four way passives that eat 90 % are not unheard of not to mention that they eliminate any damping.
Yeah, passive bandpass filters fight back against the amp. Resonant circuits. Boing, boing, boing. Decouple the load from the source, destroy the time domain. If you make a two or three pole you're gonna have so much rotation that you're gonna find yourself evaluating inverting the mid. YUCK! BLECH! Death first!

And, yep, since most mids are much more sensitive than the woofer that they must match, you're stuck dumping plenty of juice into heat. 3dB is half. Most of the time you need much more than that. Mmmmm....nice toasty warm resistors....read: long time domain dynamic compression. Ick. Little wonder you prefer two-ways.

Happily, now we can skip down the street while giggling and licking a popsicle, no more passive midrange filters.
 

Prime Minister

Site Owner
Staff member
Kluge-o-rama! I don't think either of us wants to find out what an asymmetrical pseudo MTM sounds like. Just me, MTMs ALWAYS sound spooky in the vocal range. You'd fuss with the filter for days and finally give up.

I think that if the objective is an extreme performance low level thingamajig - you'd want to start with a size and money budget and clean sheet of paper. That might be interesting and certainly is very do-able, but I have reservations about the demand for such a thing? I mean, my experience over recent years is that that particular crowd is knee-jerk adverse to both dsp and class D.

I'm finding that maaaaaaybe one in twenty mainstream audiophiles can be persuaded......and it's an awful lot of work that I just don't have the patience for. The experience is terribly repetitive. The most fertile ground is actually among the HT dudes. Tell them: "Latest super-zoomy digital technology" and they're raring to go. They do not want yesterday's stuff. I hate to be so pecuniary, but there's only so much time.

In the back of my mind for several years has been an executive desk top system with performance that kinda overlaps with this idea. Tiny output at close range but extra-extra nice. That idea usually puts the LF and electronics in the footwell to keep the mains as tiny as possible. That thingy would need to sell as a niche luxury product - a reward for execs who can flaunt it by playing music while working.
It is an interesting thought. That is, building something full range, apartment and wife friendly, and good for late night listening. The DSP is really a game changer that way. It opens up so many options.
 

Ernie

Activated
This really is a paradigm shift. Basically, throw out everything I ever thought I knew, upon which, coincidentally, I chose my preferred compromises. Now, the design is no compromise. No Compromise. This these threads are a crash course in cutting edge technology and design.

That 7" Illuminator is moving 16g of cone, vs the typical 10" at 40+ grams. Hence your aforementioned reluctance. Without yet hearing your speakers, I'm beginning to see the veil being lifted. Not 'Understanding', but grasping the fundamentals of the what you are doing.

This from a dyed -in-the-wool analogue guy.
 
This is a continuation of post #55. I just edited and went over 10k characters.

Reason #3 for "why digispeakers?"

3. (Really part of 2) The ability to tune sound in the digital domain. Id say DSP currently is >99.7% as good as its ever gonna get with respect to sound quality the vast, vast majority people are capable of hearing. My gut feeling says digital processing technology has advanced a nice amount in the last 5 years. Digitally speaking, the law of diminishing returns has probably started to kick in in last few years for audiophiles who have quite high sound quality standards. Now is the perfect time to use this technology. IMHO it is better, cheaper, and also should (time will tell, but I've got confidence) last much longer than the equivalent analog domain gear.

Maybe deoxit will be a thing of the past someday and superior sound will be the result?

“Not until you pry it out of my cold dead hands”.

Feel free to elaborate, correct, and add to.

Keep on keepin on! :)

Last thing- micro-arcing (though this is with respect to outlets, same idea for interconnect/speaker cable interfaces). Some of the fancy RCA connectors I refer to earlier (high contact pressure at interface to maximize bonding/closeness and thus lower distortion, sphere contact for "outer RCA ring") are from this site, search RCA connectors, Silver Bullet, etc (maybe its not a sphere but rather a pin, dunno, but you get the idea, the outer part is mostly plastic with a small metal contact), they also have next gen WBT, gotta get outta).

 
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Prime Minister

Site Owner
Staff member
This really is a paradigm shift. Basically, throw out everything I ever thought I knew, upon which, coincidentally, I chose my preferred compromises. Now, the design is no compromise. No Compromise. This these threads are a crash course in cutting edge technology and design.

That 7" Illuminator is moving 16g of cone, vs the typical 10" at 40+ grams. Hence your aforementioned reluctance. Without yet hearing your speakers, I'm beginning to see the veil being lifted. Not 'Understanding', but grasping the fundamentals of the what you are doing.

This from a dyed -in-the-wool analogue guy.
Yup, you got it, Ernie.
You need to come up and have a listen to mine sometime.
Your comments on the comparative mass is quite telling. Especially when you add in the factor of the amps being directly coupled to the driver, with no crossover components in the way to screw things up.

It does seem like a pretty exciting speaker, doesn't it?
 

Prime Minister

Site Owner
Staff member
So a 7 inch illuminator, with an AMT tweeter. Interesting concept.
Likely best done as a three way. What woofer would match that? A 9.5" Satori?
 

Ernie

Activated
That 7" Illuminator comment was just putting a name to the one Pat was holding, and proposing in response to your low-volume hypothesis. They have a 'midwoofer', and a woofer, in that 7" size, which is the largest of the Illuminator line-up.
 

Prime Minister

Site Owner
Staff member
That 7" Illuminator comment was just putting a name to the one Pat was holding, and proposing in response to your low-volume hypothesis. They have a 'midwoofer', and a woofer, in that 7" size, which is the largest of the Illuminator line-up.
I still think that would be a very interesting speaker. I'm sure Pat will be along soon to explain to me why I'm wrong. :)
 

Pat McGinty

Senior Member
This really is a paradigm shift. Basically, throw out everything I ever thought I knew, upon which, coincidentally, I chose my preferred compromises. Now, the design is no compromise. No Compromise. This these threads are a crash course in cutting edge technology and design.

That 7" Illuminator is moving 16g of cone, vs the typical 10" at 40+ grams. Hence your aforementioned reluctance. Without yet hearing your speakers, I'm beginning to see the veil being lifted. Not 'Understanding', but grasping the fundamentals of the what you are doing.

This from a dyed -in-the-wool analogue guy.
Thanks for reading and for the kind words. Just me, audio is suddenly more fun than it's ever been.

Indeed. F=MA. That's why the titanium formers and the coming emergence of graphene cones.

Really, why would one chose a short throw 10" when one can get equivalent displacement from a long throw 6 or 7"? All things being equal, one would not. The increased cabinet size, packaging cost and shipping cost is gonna add up and produce pale value. You do know that when the manufacturer's Bill of Materials grows by one dollar the retail grows by five? To me, that set of choices look like an easy kilobuck on the dealer's floor. Crimony, I'm fighting in the other direction. That kinda dough could bump you up two level on tweeters.

And, of course, all things are NOT equal. A 10" driver begins to beam at 1/(10"/12") x 1100 = approx 1320Hz. Smack dab in the pass band. So you will have trouble with polar response, hence power response.

It's hard for me to imagine that, somehow, the special talents of a particular low power amp can make up for what's lost, mechanically. I think this kinda thinking maybe falls into the "colorations I like" category, no?
 

Pat McGinty

Senior Member
I still think that would be a very interesting speaker. I'm sure Pat will be along soon to explain to me why I'm wrong. :)
Ha, ha! There's something wrong will every idea and, if you're a decent engineer you catch it early, unlike this bunch of bozos. Tell me nobody raised his hand and said: "Yes, but have we figured the resonant characteristics?"


Or these guys. The geniuses at Morton Thiokol designed a pressure joint that not only weakened its seal under pressure instead of strengthening it, but relied on the rapid expansion of an temperature sensitive elastomer to counteract their boo-boo. If I showed you the crossection, you'd laugh:



FWIW - that Illuminator in my hand is the 15cm woofer variant. It seems to be an excellent performer with small signals. I'd want to compare it to the Satori before committing. I'm a long time Scan Speak guy but was dumbfounded when I compared the Satori 19 to the Revelator 18 and it wasn't close.

For the small mids, you're down around 6 grams. The only caveat with the Illuminator is that, being underhung, the woofer variants' sensitivities run a bit low. For a driver made as a midrange the coil is shorter - so you see normalish sensitivity from the 12cm:

 

GuyK

Junior Member
Ha, ha! There's something wrong will every idea and, if you're a decent engineer you catch it early, unlike this bunch of bozos. Tell me nobody raised his hand and said: "Yes, but have we figured the resonant characteristics?"

...
At least one person went to prison over this one... an insurance agent pocketed premiums on policies the State of Washington had taken out on the bridge.
 

Prime Minister

Site Owner
Staff member
Ha, ha! There's something wrong will every idea and, if you're a decent engineer you catch it early, unlike this bunch of bozos. Tell me nobody raised his hand and said: "Yes, but have we figured the resonant characteristics?"


Or these guys. The geniuses at Morton Thiokol designed a pressure joint that not only weakened its seal under pressure instead of strengthening it, but relied on the rapid expansion of an temperature sensitive elastomer to counteract their boo-boo. If I showed you the crossection, you'd laugh:



FWIW - that Illuminator in my hand is the 15cm woofer variant. It seems to be an excellent performer with small signals. I'd want to compare it to the Satori before committing. I'm a long time Scan Speak guy but was dumbfounded when I compared the Satori 19 to the Revelator 18 and it wasn't close.

For the small mids, you're down around 6 grams. The only caveat with the Illuminator is that, being underhung, the woofer variants' sensitivities run a bit low. For a driver made as a midrange the coil is shorter - so you see normalish sensitivity from the 12cm:

Sooooo....
Going back to speakers. :)

How do you think this three way we have been discussing, would differ from my current Kites? The AMT would likely be more open sounding, I would think. Not better sounding, because the Satori sounds brilliant, but a different flavour and experience.

Any thoughts?
 

Pat McGinty

Senior Member
Sooooo....
Going back to speakers. :)

How do you think this three way we have been discussing, would differ from my current Kites? The AMT would likely be more open sounding, I would think. Not better sounding, because the Satori sounds brilliant, but a different flavour and experience.

Any thoughts?
Yeah, before we start throwing money at a new three way idea, let's back up a minute.

There are two advantages to going with DSP/local amps that have been driving me forward, the second one is much more compelling than the first:

1) Modest designs like Kite can deliver more performance in a smaller package and at a lower total system cost.

2) The frontier of the possible can be advanced, and by a big measure.

I hadn't even considered a third possibility that the technology could be used to build a better bedroom speaker, probably because I don't do that sort of listening, haven't had a stereo in my home in decades; have never had a reason to "dial in down".

To be sure, Kite's programming aggressively sets out to prove point #1 without much thought, if any, about low level work.

Perhaps the smart thing to do first is to make a program that sounds nice and pretty at 75dB and not care about how it does at high amplitude, maybe even prevent it from playing loudly because it'll likely extend the tweeter's band, making it more vulnerable. You do have four Presets to play with.

I can write the program, email it, and you can try it and see if you like it. This is one of the best things about DSP.

Meanwhile, I'm working on challenge #2. I do have customers who want to go all out.

If we think there is a market for a fully tricked out bedroom speaker we can do that too.
 

Ernie

Activated
My system doesn't live in a bedroom, but I listen at low-ish levels, because the is another house, on the other side of the wall.
 
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