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Multi-Way Conventional loudspeakers with crossovers

My first wave guide speaker....lots of pics
My first wave guide speaker....lots of pics
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Old 26th August 2013, 04:09 PM   #41
Greebster is offline Greebster  United States
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Originally Posted by Juhazi View Post
Many people want to get backward radiation to as higf Fq as possible, but I'm not so sure about it being wise. I for example have windows right behind the speaker, and they are like mirrors at high Fq - too much reflections???
Heavy drapes would help breakup and absorb these glass reflections.

I can see you asking Aino to open / close while you listen
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Old 26th August 2013, 04:22 PM   #42
badman is offline badman  United States
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There's definitely a good reason to have the rear wave as closely matched to the front (tonally) as possible- but the transfer function as perceived by the listener is what needs to be matched, not necessarily the rearward radiation. If you have a highly reflective surface behind the speakers, then you'd want to either damp it or adjust the rearward output to avoid having a bright reflected tonal balance.

I have a rather cool setup in which my living room (which houses the big rig and is more of a mancave than anything else) joins to the kitchen and dining spaces with only one section of wall, and open doorways etc. The speakers are directed so as to fire the rearwave into those back spaces- so I get sound wherever I am, but the rear reflections are well delayed. For me, since I listen passively from behind regularly, it's critical that the rear lobes match the front reasonably well (or at least are properly balanced).
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Old 26th August 2013, 04:56 PM   #43
Dave Pellegrene is offline Dave Pellegrene  United States
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Originally Posted by Juhazi View Post
OMG!!! Those David Pellegrine's amt+double wg measurements are from heaven on a sunny day! This makes me really hungry!
Click the image to open in full size.

David's woofer is in a frame that is far form ideal as a dipole. It should be relatively easy to find the right diameter for a nudie mid to xo around 2kHz LR4 and end up with consistent directivity.
Click the image to open in full size.

Many people want to get backward radiation to as higf Fq as possible, but I'm not so sure about it being wise. I for example have windows right behind the speaker, and they are like mirrors at high Fq - too much reflections???
I can't take full credit for this design. I built these for a client and he had everything speced out for me other then we started with the Morel Cat378. I reported back to him that they just where not getting the job done with this design. He then sent me the AMT2560 to try. I was shocked on how well it did in the waveguide. I had the speakers set up 6' from the front wall with a damping panel on the wall directly behind each speaker, 4' from the side walls and toed in just in front of my listening position. That is where I found them to sound best. I also tried them in my living room which is 25' x 25' with 11' ceilings, hardwood floors on half the floor and a wall of glass on one side. I found them a bit bright especially at higher volumes. I have no daming in this room. Tried but the wife said NO!
This is actually a 2.1 system with a dipole sub. Here is a build thread if anyone is interested.
Open Back Speaker Build

Dave
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Old 26th August 2013, 05:11 PM   #44
badman is offline badman  United States
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Hi Dave:

The periodic ripple you see at the bottom of the w/g range may be related to 2 things- the baffles are not properly rounded/beveled, so you're getting some edge diffraction (though it's significantly lower in level thanks to the directivity) and also the final transition on your w/g has a harder edge- particularly in the verticals. Some (teased so it's loose) felt around the perimeter of the edge at the mouth would likely be a very worthwhile tweak to suppress some of the ripple.
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Old 26th August 2013, 05:28 PM   #45
Greebster is offline Greebster  United States
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My biggest hurdle with waveguides is using them in an MTM setup. No possible way to get the spacing correct, well unless you block off part of the M's when doing so.

She would not want me to build another set. What it looks like isn't the problem, but she'd freak if I'd pulled a Cal Weldon on her! (We've been down that road before

Sad too as I have a couple dozen different designs in my head ATM.

Dave, you should try out the Dayton Audio AMT2-4 ( similar to Airborne rt4001) or the Mini8-4 (airborne rt 20021) with a waveguide. Should be a winning combination. Far less $ than others = good price performance ratio would make them popular IMHO.
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Old 26th August 2013, 05:44 PM   #46
badman is offline badman  United States
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Greebster, some have done a pretty good job of limiting CTC spacing with waveguides- often that means routing the midwoof cutouts with the waveguide already mounted, and removing some of the plastic, so the flange doesn't get in the way as much.

That's what was done on some (presumed) DDS waveguides in these custom JBL-based systems:

Click the image to open in full size.

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Old 26th August 2013, 08:35 PM   #47
Dave Pellegrene is offline Dave Pellegrene  United States
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Originally Posted by badman View Post
Hi Dave:

The periodic ripple you see at the bottom of the w/g range may be related to 2 things- the baffles are not properly rounded/beveled, so you're getting some edge diffraction (though it's significantly lower in level thanks to the directivity) and also the final transition on your w/g has a harder edge- particularly in the verticals. Some (teased so it's loose) felt around the perimeter of the edge at the mouth would likely be a very worthwhile tweak to suppress some of the ripple.
I agree the baffle edges are to sharp. Especially on the rear guide. Before we went to the rear waveguide the wings where not notched out. The cabinet finish was done so that was really the only way I could fit the guide without getting into the finish.

On the vertical are you saying something like RAAL does but with thinner felt?

I've done a little bit of testing with the baffle edges to see what I could come up with that was simple to do and seams to work well. This is a guide I'm working on for myself that wraps around the mid. The baffle edges are 30 degrees plus a 60 degree cut where it meets the cabinet. Then the edges are sanded to a slight round over. This is done with a 3/4" baffle with 2" strips glued around the edges to make it a total of 1-1/2" thick. This seems to work well for diffraction and is pretty simple to do on a table saw.

SpinMonster
This started as an RS150/ XT25TG30 combo for the top of a three way. I ended up switching out to the ER18 and the LD25X. Although twice the money IMO i think well worth it.
I don't believe the LD25X is available with the removable face plate any more which you need for these guides.

Click the image to open in full size.



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Old 26th August 2013, 08:45 PM   #48
tinitus is offline tinitus  Europe
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My first wave guide speaker....lots of pics
if it's a pyramid design with 'slanted' baffle, that is cool

any sidewiev pics ?
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Old 26th August 2013, 09:01 PM   #49
badman is offline badman  United States
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Originally Posted by Dave Pellegrene View Post
I agree the baffle edges are to sharp. Especially on the rear guide. Before we went to the rear waveguide the wings where not notched out. The cabinet finish was done so that was really the only way I could fit the guide without getting into the finish.

On the vertical are you saying something like RAAL does but with thinner felt?
Yes, though I'd use it all the way around- your waveguides terminate in an angle rather than a fully flat (or rounded/rolled back) surface. While they're better in this respect than many horn/waveguides, there are several that do this better- the SEOS, the OSWGs from both geddes and the DDS variant, the QSC, etc. Of course, you're optimizing for certain factors, which I get- it has to fit, after all, and your polar performance is nothing if not impressive.

Foam or felt allows you to mitigate any diffraction over that lip while still retaining the same flange size. Basically you want to approximate a forward continuation of the profile, with whichever lossy material you use, so it doesn't screw up what's already good, but acts more like a larger roundover. Pic is the JBL Progressive Transition horn/waveguide as used in the Econowave project, with shaped foam extending the profile and killing the hard edge.

The shaped waveguide you show is pretty awesome way of incorporating it into the baffle. Heck of a job! Don't mind the fugly "test mule" style build, or the pine needles on the carpet- the foam is the key!

Click the image to open in full size.

Foaming At The Mouth Article By Jeff Poth
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Last edited by badman; 26th August 2013 at 09:26 PM.
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Old 26th August 2013, 09:05 PM   #50
Greebster is offline Greebster  United States
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Quote:
Originally Posted by badman View Post
Greebster, some have done a pretty good job of limiting CTC spacing with waveguides- often that means routing the midwoof cutouts with the waveguide already mounted, and removing some of the plastic, so the flange doesn't get in the way as much.

That's what was done on some (presumed) DDS waveguides in these custom JBL-based systems:

Click the image to open in full size.

Full Size Image
Depends on where it's crossovered at. If we can dig much deeper this issue is lessened altho remains. I've done trimming of the flanges on both midrange, midbasses and waveguides, then using clay/felt/foam to fix, but one can only go so far once we get up higher. Simply not enough room. You are correct the problem is the edge diffraction when doing so, this energy is reflected back down the throat akin to back EMF, a high vSWR in antennas. Dr. Geddes solution using reticulated foam really works in this regard. Have done testing using the same about an eon ago with the same type he uses is the same as what I had been using for speaker grills as early as the late '70's. The high vector diffusion of such is quite practical in reducing this effect.

Another means to reduce this effect is rounding the waveguide flange like JMLC and Azura horns use. Albeit making them larger causing greater issue with CtC spacing. Personally think if this were a normal two or three way the sharp edge can be rounded over with a oval or ring of foam, sculpted felt etc. Clay helps to fill voids. Tapering off near the closest driver.

If it weren't for pottery clay deforming while in the kiln I'd whip out dozens. Bone dry greenware is bloody fragile so only works for the person that made it. Can think of several types of glaze that would make them look stunning if the shape could be maintained within tolerance.

Here's an idea, back dampen a commissioned Dale Chihuly blown glass horn. He's a true master artist
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