Waveguide TMM Posted

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WaveguideTMM-bafflefrontcloseup.jpg


Waveguide TMM

I posted this yesterday. Note: I see a few typos I made which I will update later when I get home.

This is another design that I've posted in the quest to do "something different". It turned out pretty good. I found myself getting emotionally involved with the music I've been playing through them. That's pretty unique for someone as objective as myself.

Enjoy,
John
 
That's a great looking design!

One question: in most of your project descriptions, you address/discuss the feasibility of using a sealed box, but in this writeup you only mention ported alignments. Would this design be a candidate for a sealed alignment with a somewhat less deep cabinet (for greater WAF)?
 
Wodgy said:
One question: in most of your project descriptions, you address/discuss the feasibility of using a sealed box, but in this writeup you only mention ported alignments. Would this design be a candidate for a sealed alignment with a somewhat less deep cabinet (for greater WAF)?

The Seas CA18RNX woofers really need to be vented. In a sealed box, the best F3 is only around 90 Hz. That might be fine if you use a subwoofer, and the sub crossover can be set to 90 hz and configured for assymmetrical slopes. I pretty much don't recommend it though. The CA18RLY would be better sealed in a 14 liter box. That driver can't swap into this design however.


Joules said:
Hey Zaph - Great waveguide work !!
Do you think it wood be posibale to use a waveguide on a mid/woofer to compensate for baffel step rolloff?

A waveguide on the midwoofer is possible, but not practical. The wavelengths are way to long.

Regards,
John
 
Hi John.

One thing I've personally only heard with waveguides is an effect where when you walk around between the speakers, the imaging will stay relatively locked in place. Have you heard this with your design?

I'm taking a casual look at converting the floorstanding size into a stand mount by making the enclosure deeper. Any objections, assuming volumes are maintained? More to the point, any objections to mounting the port on the side of the cabinet, if it comes down to it?

One last thing - any objections to turning the speaker upside down as long as the acoustic center is at ear level?

Thanks!
 
John,

Thanks for sharing that design, especially with the different XO topologies apparently working so well.

Instead of woofers, what would be your opinion about trying a waveguide on a small full ranger to improve the top end? eg I'm about the build the reference enclosure for the FE127 discussed in the full range forum and I was thinking about added a piece of 1" hardwood in front of the driver for a backside of the baffle mounting look. Initially I thought I'd just round over the front edge of the driver cutout, but now I'm thinking I should be more scientific regarding the shape of that taper to make it a beneficial wave guide.
 
ooheadsoo said:
One thing I've personally only heard with waveguides is an effect where when you walk around between the speakers, the imaging will stay relatively locked in place. Have you heard this with your design?

I'm taking a casual look at converting the floorstanding size into a stand mount by making the enclosure deeper. Any objections, assuming volumes are maintained? More to the point, any objections to mounting the port on the side of the cabinet, if it comes down to it?

One last thing - any objections to turning the speaker upside down as long as the acoustic center is at ear level?

Yes, I've noticed that with the imaging. Not necessarilly when walking around, but it really seems to lock in, almost a headphone-like effect.

No worries about the cabinet variations, it should work fin as long as the baffle width stays the same. Upside down would work fine but that would be one weird looking speaker.


johninCR said:
Instead of woofers, what would be your opinion about trying a waveguide on a small full ranger to improve the top end? eg I'm about the build the reference enclosure for the FE127 discussed in the full range forum and I was thinking about added a piece of 1" hardwood in front of the driver for a backside of the baffle mounting look. Initially I thought I'd just round over the front edge of the driver cutout, but now I'm thinking I should be more scientific regarding the shape of that taper to make it a beneficial wave guide.

A 1" waveguide is probably just going to cause a ragged response curve over a small range, no real benefit. In fact, I don't see a benefit on anything other than a tweeter. Woofers by nature already have directivity built in with their large cones.

kevyjo said:
Looks great zaph! I also wanted to say I've read your website and blog and found it very informative and interesting. Forgive me for being off topic, but I'm very curious, what are your opinions about series crossovers? (or maybe I should start another thread).

That's probably best for another thread. The problem is that I would never even both opening or reading that thread. ;D I don't think there's any magic in series crossovers, it's just another way arranging the components.
 
ooheadsoo said:
Thanks for the reply, John.

Do you think there is benefit in extending the directionality of the speaker by crossing the drivers down into the 1khz or below range (with different drivers of course) ala Dr. Geddes's implementation or SP Technology?

Yes, that could be done but it might be hard to get a significant power handling increase out of the MCM horn lens, simply because it is a bit shallow and only 6" diameter. As I built it, I think the increase in power handling below 1500hz is minor.

Or, if you're getting at the idea of adding a waveguide to the woofer, I don't think it's a good idea. The size of the waveguide would be large, and the tweeter would be so far away that there would be severe lobing and the vertical listening axis would be so narrow that even a few inches could create a large null.

For thosing thinking of a "small" waveguide on a woofer, consider that one these has to be substantially larger than the radiating surface to even be useful at all. Otherwise it just causes a large peak and dip in response.

John
 
You could try making some sort of weird custom waveguide that houses both a mid and a tweeter. Go to http://www.genelec.com/products/1038b/images/b_1038b.jpg to see what I mean. The midrange driver doesn't look like it's that much further away from the tweeter in Zaph's 2 way design. Obviously if you had seperate waveguides for the mid and tweeter individually things would be different.
 
very nice project john, it's been a long time since i wanted to design a speaker with waveguide, as some of my most beloved studio monitors do have waveguides.

parts express do sell bigger waveguides, up to 12"

As long as we are talking about directivity what do you think would be the effect of doing a 2 way with 6" or 8" waveguide and 8" woofer ?

or lets be crazy, assuming i find a woofer that's having a well extended response, a system with a 10" woofer with a 8" or 10" waveguide (actively crossed over so i can use slopes as steep as 48 db / octave)
 
Depth Charge said:
You could try making some sort of weird custom waveguide that houses both a mid and a tweeter. Go to http://www.genelec.com/products/1038b/images/b_1038b.jpg to see what I mean.

Those would be great. I have no doubt that the Genelec monitors sound incredible. I've heard good things about them. I can't see myself trying to build a mulit-driver waveguide anythime soon. I can barely hack up the plastic from MCM, much less do some custom forming.


Nemophyle said:
very nice project john, it's been a long time since i wanted to design a speaker with waveguide, as some of my most beloved studio monitors do have waveguides.

parts express do sell bigger waveguides, up to 12"

As long as we are talking about directivity what do you think would be the effect of doing a 2 way with 6" or 8" waveguide and 8" woofer ?

or lets be crazy, assuming i find a woofer that's having a well extended response, a system with a 10" woofer with a 8" or 10" waveguide (actively crossed over so i can use slopes as steep as 48 db / octave)

I was completely unaware that Parts Express sells waveguides. Digging around there, I see the 8", 10" and 12" . Just looking at them, I have a slight concern about their shape - mainly the edges around the outside. I believe there should be a smooth transition from the waveguide to the baffle or an irregular diffraction response could result. I'm just guessing though, I think I'll buy one to check out. They're cheap. Depending on how well the response curve looks, one of those could make a nice combo with a 8 or 10" driver.
 
i'm gonna buy a couple of 8" and a couple of 10" , and measure them with a silk dome... anyway i think that the edges could be rounded with some patience if it is better for the sound.

i was planning of using this very nice 10" driver with a tweeter ==>
A.T.S French drivers
look at the HG 25

they use a sandwich ceramic/paper/ceramic with an elastic compound inbetween.


what do you think is better ? 8" or 10 " waveguide for this application ?
 
Nemophyle said:
As long as we are talking about directivity what do you think would be the effect of doing a 2 way with 6" or 8" waveguide and 8" woofer ?

or lets be crazy, assuming i find a woofer that's having a well extended response, a system with a 10" woofer with a 8" or 10" waveguide (actively crossed over so i can use slopes as steep as 48 db / octave) [/B]

Ahhh... Nemophyle beats me to it.. ;-)

I was thinking the same thoughts... being that I have a pair of RS225's sitting here waiting for some kind of project...

Wondering how much lower one might be able to usefully use a tweeter with the waveguide loading. That too, has gotten touched upon in this thread, but any further thoughts on that John? I know there is only so much Xmax to deal with on a particular tweeter, and as one goes lower in frequency it's easier to use it up... How can we figure out how low can we go before distortion or power handling starts to become a problem?

I've done some preliminary first CSD's (new SE user here) on the RS225's, and it looks like the big energy storage is around 1.4-1.6Khz, assuming I'm doing things right. So, a serious challange to do a 2 way, for most tweeters. But... if you could cross lower than that, well, the possibilites open up..

I'm also paitently waiting to hear more info on how a certain RS28-RS225 project turned out.

The SP Technologies site was interesting... and got me wondering if they are using some kind of custom spec tweeter, or are they thru the wonders of proper horn loading, getting something more standard to be usefully crossed over at the 750Hz (or 900) that they quote?

If you could get a 27TDFC to cross that low, it should be a great match with the RS225 or other large woofers..
 
hey jonpike

there is a project with RS225-RS28 that turned out quite well : RS225+RS28

I personnally wanted to use a 10". It's something you almost never see,at least in the non-pro drivers world, because of too much directivity issues.But then the waveguide would really help resolve theses issues for what i did understand

the use of a 10" aluminium cone is pretty excluded because of breakups too much too early. except maybe this one that maybe very interresting with a steep slope (24 db at 1500 + notch around 2000 or 48db at 1700)
alcone AC10HE

but the A.T.S woofer i previously linked seems to have at the same time a very rigid and very well damped cone that may be perfect for what i want to do.

but it would require a big waveguide
 
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