waveguides/horns. what's the point?

[mzisserson]

So I have a couple of questions after diddling about the idea of waveguides...

1) What is their true intended purpose? Aside from the obvious where it is to focus the sound in a specific pattern for very large venues, what is the livingroom advantage?

2) Even if you were to cross over a wavguided tweeter at 1.5k eliminating some/all of a room, that means from 300-1.5K (using 300 on the high side of room interaction average) still is not directional and will have reflections arriving at the ear before the direct sound. Doesn't this mean the WG will create an imbalance?

3) Wouldn't that imbalance lie in the power response even of the Fq response is somewhat flat? Beaming?

I am missing something here about their application in the home. I know they are beloved by some, others do not bother. I am having a hard time seeing how they make sence from a scientific standpoint of the whole darn speaker is not loaded down to 200-300Hz...

From the interest in being scientifically sound, If i presue I would like to fully educated. Thanks!


This is coming from a guy who likes involving the room, so this is a new branch on the tree for me.

[depthsounder]

There are a couple of advantages to a waveguide. The first and most obvious is the directivity control. The idea isn't so much constant directivity for all frequencies as it is smoothly varying horizontal directivity through the crossover region. The second is the decrease in distortion due to the "focusing" of the wavefront. That is, for a given SPL within the beam pattern the displacement required is lessened and thus the distortion is lessened.

The smoothly varying or constant beam pattern can be achieved in different ways, for example an omni speaker will have constant directivity by definition. A dipole will have somewhat constant directivity below the dipole frequency.

My personal experiment is blending attributes of a dipole midrange with that of a waveguide tweeter. I don't know how the lack of a backward propagating wave in the treble frequencies will affect the result, but I intend to find out.

-David

[johnnyrichards]

This is coming from a guy who likes involving the room, so this is a new branch on the tree for me.

With my last three designs (Le Singe Sarcophage, Rompicollo, The Ocho) I have done my design work and voicing based on what I presume is a typical placement in a more-or-less average room. If there is anything my main listening area has a lot of, it is "average" attributes.

Enlightening, to say the least.

Makes me wonder what I am going to bring to the next DIY event I attend

How are they going to sound without my TV right there?

[Deward Hastings]

With my last three designs (Le Singe Sarcophage, Rompicollo, The Ocho) I have done my design work and voicing based on what I presume is a typical placement in a more-or-less average room.

One has to . . . and it does raise "issues" regarding how a speaker "translates" from showroom or DIY event to actual use. Rooms matter . . . and speakers need to be "tuned" to them if your goal is anything close to accurate reproduction of a "natural" sound event.

I've just come from back-to-back productions in two very different halls . . . where the difference in "sound" is, if not "night and day", quite substantial. The California Theater (in San Jose) has an exquisite sound, slightly dry but with enough "hall" to satisfy the musicians when set as we do, with a flat shell at the curtain line and the band entirely forward on the apron and (raised) pit elevator (with the "normal" seating used by Symphony Silicon Valley, which seats back behind the curtain on the stage, with a large shell and a few clouds, the sound is pretty bad). First Congregational Church in Berkeley, on the other hand, is very reverberant, especially on stage, which muddies the sound and makes it a difficult venue to play in (singers tend to like it though). It would benefit enormously from even modest "room treatment", expecially around the stage. We rehearse there . . . and the difference even a few shipping pads draped over chairs makes is immediately noticable. Translate that experience to your "average" listening room . . .

[Pete Schumacher ®]

Here's an example of a 2" deep waveguide (perfect for an 8" woofer acoustic offset . . . ) that is 8" in diameter, with an elliptical flare profile.

Blue is the RS28F flush on baffle. Red is with the waveguide, green is 20 degrees off axis. Notice the region that is getting a "boost" in output. Even at 1KHz, there's still an extra 5dB of output. When that is EQ'd back to "flat" on axis, you get a commensurate reduction in distortion for the same SPL as the non-waveguide tweeter. That boost is in the region most demanding on the tweeter, and should allow for greater performance in-band, and lower crossover points.

There's also the more consistent off axis performance to a lower frequency with the waveguide.

[djg]

A while back, a few people at HTguide did a comparison of three Zaph designs, the then new ZDT3.5, a tower version of the BAMTM, and the Zaph waveguide tower speaker. They all really liked the waveguide speaker. I'm sure you could find the thread if you're interested enough to look for it. From memory, glowing descriptions of great off axis response.

[Mayhem13]

A while back, a few people at HTguide did a comparison of three Zaph designs, the then new ZDT3.5, a tower version of the BAMTM, and the Zaph waveguide tower speaker. They all really liked the waveguide speaker. I'm sure you could find the thread if you're interested enough to look for it. From memory, glowing descriptions of great off axis response.

I've built the WG TMM and a TM version as well as other domes in other WG's and i'll give you an analogy. It's like dating a new woman....things are great at first but then after a few months........

As Deward stated earlier, if you can get that XO point down to the midrange where the device shifts from omni to directional, it's much more difficult for the ears to pick up on it. I think localization of sound starts to fall off around 1.3khz and worsens the lower you go. I'm pretty shure Geddes crosses around 800-900 hz and that's a good match for a 12+ inch waveguide but these are compression driver loaded which maximize on a second front of Uber low distortion. They use 1" throats as you know. There's not too many 1" drivers that can play that low (domes are out!) and still extend above 17khz. There's a few 1.4/1.5" compression drivers that can but they are really expensive. ErichH whose a member here is working with a designer and manufacturer and have just accepted delivery of an EXCELLENT Oblate Spheroid 15" wide waveguide (it's a rectangle so easier to center up to a woofer) with a 1" throat whose directivity is amazing to below 1khz. If i were going to give waveguides a try, i'd start there with a B&C DE250 1" CD. It's a recipe for success IF you're gonna like the whole waveguide thing.

Probobly better to ask around and see whose got a pair of Geddes speakers in your zip code and go take a listen. Let your ears be the judge.

[Pete Schumacher ®]

I'm pretty shure Geddes crosses around 800-900 hz and that's a good match for a 12+ inch waveguide but these are compression driver loaded which maximize on a second front of Uber low distortion. They use 1" throats as you know. There's not too many 1" drivers that can play that low (domes are out!) and still extend above 17khz.

When you get to hear the Scan 6600 Air Circ in a 10" diameter, 3" deep waveguide, you realize that a good dome tweeter can sound amazing in the proper waveguide, crossed below 900Hz.

Crossed to the Dipole SEAS W22 Excel makes for a very engaging experience.

[Mayhem13]

When you get to hear the Scan 6600 Air Circ in a 10" diameter, 3" deep waveguide, you realize that a good dome tweeter can sound amazing in the proper waveguide, crossed below 900Hz.

Crossed to the Dipole SEAS W22 Excel makes for a very engaging experience.

You are right Pete, they can sound 'good'......just not very loud from a power handling standpoint.

...but your example brings up an interesting issue. We know what a properly mated WG does to lower HD on the low end of the tweeters response but in this and probobly the case of most domes, there's going to be considerable amounts of 'measurable' HD at and below XO. Are these odd order products audible?....or as i believe the lower in frequency you go, the less audible they become making a dome like the AirCirc usable. I still would't want to push a $240 dome too hard...just sayin.

[Pete Schumacher ®]

You are right Pete, they can sound 'good'......just not very loud from a power handling standpoint.

...but your example brings up an interesting issue. We know what a properly mated WG does to lower HD on the low end of the tweeters response but in this and probobly the case of most domes, there's going to be considerable amounts of 'measurable' HD at and below XO. Are these odd order products audible?....or as i believe the lower in frequency you go, the less audible they become making a dome like the AirCirc usable. I still would't want to push a $240 dome too hard...just sayin.

They're 94dB/2.83V tweeters to begin with. And in those waveguides, even crossing at 875Hz isn't a stretch, due to the massive boost the WG provides. Believe me, they more than keep up with the OB Excel W22, at any volume. Ryan's had 1000W driving the pair, and there's no hint of strain, even at quite high volumes.

Ryan said he measured distortion levels below .5% down to the XO point at better than 90dB output. Keep in mind, that Air Circ isn't your typical dome tweeter. But that WG is a gem, and does wonders to properly load the tweeter dome to keep it under control, allowing quite low XO points.

[dlr]

I'm pretty shure Geddes crosses around 800-900 hz and that's a good match for a 12+ inch waveguide but these are compression driver loaded which maximize on a second front of Uber low distortion. They use 1" throats as you know. There's not too many 1" drivers that can play that low (domes are out!) and still extend above 17khz.

You're right about the Fc, my memory was bad. Took a while to find a post at diyAudio that discussed it.

It also looks like he tends to match the waveguide throat diameter to the diameter of the woofer with which it is paired.

dlr

[Mayhem13]

A while back, a few people at HTguide did a comparison of three Zaph designs, the then new ZDT3.5, a tower version of the BAMTM, and the Zaph waveguide tower speaker. They all really liked the waveguide speaker. I'm sure you could find the thread if you're interested enough to look for it. From memory, glowing descriptions of great off axis response.

On the horizontal yes.....but the vertical not so much.

[Mayhem13]

So I have a couple of questions after diddling about the idea of waveguides...

This is coming from a guy who likes involving the room, so this is a new branch on the tree for me.

And this is exactly what a properly designed WG doesn't do.

Beaming is often used as a negative and when desired, it's described as Directivity. It's a matter or personal preferance or 'taste' so to speak.

IMO of the WG systems i've heard, those that cross 1k and lower are the ones that get it right. It's not CD to 300, but it's close enough. That requires a BIG guide to accomplish as you already know.

[mzisserson]

With my last three designs (Le Singe Sarcophage, Rompicollo, The Ocho) I have done my design work and voicing based on what I presume is a typical placement in a more-or-less average room. If there is anything my main listening area has a lot of, it is "average" attributes.

Enlightening, to say the least.

Makes me wonder what I am going to bring to the next DIY event I attend

How are they going to sound without my TV right there?

Exactly why I design the way I do, too.

And this is exactly what a properly designed WG doesn't do.

Beaming is often used as a negative and when desired, it's described as Directivity. It's a matter or personal preferance or 'taste' so to speak.

IMO of the WG systems i've heard, those that cross 1k and lower are the ones that get it right. It's not CD to 300, but it's close enough. That requires a BIG guide to accomplish as you already know.

300 would be a giant horn... 1K and lower, so you would need quite the robost mid-tweeter-ish thing. No?

[dlr]

Exactly why I design the way I do, too.



300 would be a giant horn... 1K and lower, so you would need quite the robost mid-tweeter-ish thing. No?

IIRC, Geddes OS waveguides have a diameter roughly that of a 12" woofer and are crossed at about 300Hz. But those are also designed with a listening axis of 22.5 degrees with on-axis intersecting well in front of the listener. This is tominimize room interaction above 300Hz, not sure how much the floor is an issue, since you can't get away from that so easily. He also claims that it provides a wider "sweet spot", due to changes in SPL of the L-R sides when moving laterally. It makes sense, but I've never heard them.

They use compression drivers for the waveguide, of course. He uses a dynamic driver below that, so there is no directional control below 300Hz.

dlr

[Deward Hastings]

1) What is their true intended purpose?

Properly done a waveguide can broaden the pattern at high frequencies (where the driver would otherwise "beam", and narrow it at low frequencies, to better match the onset of beaming from the driver below it. The necessary size of the "guide" brings on other problems, though, like center-to-center issues causing lobing on the vertical axis.

2) Even if you were to cross over a wavguided tweeter at 1.5k eliminating some/all of a room, that means from 300-1.5K (using 300 on the high side of room interaction average) still is not directional and will have reflections arriving at the ear before the direct sound. Doesn't this mean the WG will create an imbalance?

While it's pretty unlikely that you'd ever get reflections before the direct sound you can get reflections that interfere in several different ways. It is always an issue in small untreated rooms. Fortunately our ear/mind can compensate for a lot of the reflection issues. But the nearly unavoidable shift from "omni" to directional that with most speakers happens somewhere in the lower mid-to-midrange is always audible . . . it's just so common that it's become an generally accepted part of "reproduced" sound. Waveguides don't help with that.

3) Wouldn't that imbalance lie in the power response even of the Fq response is somewhat flat?

Yes. And there are only two small-enough-to-be-practical patterns that address that issue. A common half-way step is to go for a more uniform horizontal polar pattern (usually at the expense of the vertical) . . . but the vertical pattern does matter in a small room, and the shift, whether it occurs at the m/t crossover or at "baffle step", is simply wrong.