I think you overvalue importance of waveguides shapes. You can choose any waveguide you like, choose whichever is prettier. Jay, as long as waveguide does not resonate, I don't think it's length matters. If waveguide creates additional peaks in tweeters impedance, then there is a problem. Something like this probably is not suitable for a tweeter. PRV Audio WG 14-25 45x45 ABS Waveguide 1-3/8"-18 294-2841
The eliptical guide for the XT25 was recently redone. The eliptical is 8.5 or so wide.
The black line is bare. Its lifting even at 1200.
https://picasaweb.google.com/101632266659473725850/VifaXT25TG30041?noredirect=1#5915426940381052322
cherry waveguides
I found a profile on Zaph Audio website for a 6.5" waveguide and turned a couple yesterday. I made the overall diameter 7" by adding a 1/2" edge to the profile.
Some people think the later XT25 faceplates are glued to the tweeter body. Mine aren't. After removing the 3 screws that attach the faceplate, the separation of the faceplate required carefully inserting a sharp knife at the joint and the plate slowly separates.
Here are 3 pics, one shows the small bevel required to closely fit the face of the XT25. This detail came from Troels' website. I now need to make a couple of wood plates to be located at the back of the tweeter to secure them to the WG.
Test assembly will have to wait until next week.
Peter
I found a profile on Zaph Audio website for a 6.5" waveguide and turned a couple yesterday. I made the overall diameter 7" by adding a 1/2" edge to the profile.
Some people think the later XT25 faceplates are glued to the tweeter body. Mine aren't. After removing the 3 screws that attach the faceplate, the separation of the faceplate required carefully inserting a sharp knife at the joint and the plate slowly separates.
Here are 3 pics, one shows the small bevel required to closely fit the face of the XT25. This detail came from Troels' website. I now need to make a couple of wood plates to be located at the back of the tweeter to secure them to the WG.
Test assembly will have to wait until next week.
Peter
Attachments
Dave Pellegrene's wave guides cover the outside surround ring. He says it improves measurement.
Easy mounting system just uses 3 supplied posts
Tighten down the nuts. I used a silicone sealer to ensure an air tight fit.
Horizontal dispersion is of a 8" wave guide, vertical is as if it was a 5.5" WG. Sitting on the floor and standing on my couch has no fall if in highs. There is no sweet spot in the room. Dispersion even at 60 degrees off axis is near perfect compared to the bare tweeter. Wave guides also time align the driver. If there is a down side to WG's I dont see it. I see no advantage to a round WG. Elliptical allows a closer spacing to the midbass and thus a higher allowable cross freq if you need it. Dave are $35 each and make for a $70 total per tweeter with state of the art performance. They have lower distortion down low with a cap than any bare tweeter, play 10db louder than bare, and cost so little with perfect dispersion anywhere in the room.
The double mag version of the XT25's are lower ditortion, more efficient, and only cost a dollar more.
The wood ones above are beautiful.
Easy mounting system just uses 3 supplied posts
Tighten down the nuts. I used a silicone sealer to ensure an air tight fit.
Horizontal dispersion is of a 8" wave guide, vertical is as if it was a 5.5" WG. Sitting on the floor and standing on my couch has no fall if in highs. There is no sweet spot in the room. Dispersion even at 60 degrees off axis is near perfect compared to the bare tweeter. Wave guides also time align the driver. If there is a down side to WG's I dont see it. I see no advantage to a round WG. Elliptical allows a closer spacing to the midbass and thus a higher allowable cross freq if you need it. Dave are $35 each and make for a $70 total per tweeter with state of the art performance. They have lower distortion down low with a cap than any bare tweeter, play 10db louder than bare, and cost so little with perfect dispersion anywhere in the room.
The double mag version of the XT25's are lower ditortion, more efficient, and only cost a dollar more.
The wood ones above are beautiful.
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I can stand anywhere in my 21 x 21 foot room and there is no change in dispersion. Its the ultimate party speaker that sounds the same everywhere. The cross is at 1600 so the midbass isn't beaming either.
Here is a comparison using the XT25TG30 with a Flat baffle (red) vs 165mm x 115mm waveguide with the throat 1.5" ( fitting around the surround) (blue) vs. 165 x 115 waveguide with a 1" throat ( black ). I wanted to show the difference with a 1" throat vs a throat that fits outside the surround. This doesn't always work. Some tweeters just don't like it. As you can see with the 1" throat the boost goes all the way up to 18kHz. Most tweeters/ waveguides with a 1" throat will only boost about 2-3 dbs up to around 12.5kHz with a 1" throat. I find the XT25 is probably the easiest tweeter to fit to a waveguide. It does well with just about any waveguide.
In fairness the guide that fits around the surround (blue) was not cut down to fit in the baffle properly and overhung the side chamfers so I believe the dip between 5-6kHz is do to that.
The two guides in the graph are about 1.5" deep.
Dave
In fairness the guide that fits around the surround (blue) was not cut down to fit in the baffle properly and overhung the side chamfers so I believe the dip between 5-6kHz is do to that.
The two guides in the graph are about 1.5" deep.
Dave
I'm excited about comparing the XT25 in a flat baffle vs WG.
Personally, I usually sit in a central location when I am listening to an opera, for example and even though impressive, see little benefit of "same sound everywhere in the room", for me.
What does seem like a real bonus is the reduced distortion and the comments by John Krutke, that his TMMs with WG sounded like a good pair of headphones. So, besides pairing with Vifa 8" woofers, a TMM with 6.5" Peerless Nomex drivers may work well. Lots of opportunities to try out my Minidsp.
Thanks for all the comments, info and advice.
Peter
Personally, I usually sit in a central location when I am listening to an opera, for example and even though impressive, see little benefit of "same sound everywhere in the room", for me.
What does seem like a real bonus is the reduced distortion and the comments by John Krutke, that his TMMs with WG sounded like a good pair of headphones. So, besides pairing with Vifa 8" woofers, a TMM with 6.5" Peerless Nomex drivers may work well. Lots of opportunities to try out my Minidsp.
Thanks for all the comments, info and advice.
Peter
The vertical gap is almost impossible to measure. On almost all tweeters I've worked with it is very critical. Along with the angles on the inside and outside of the throat. Seems almost all tweeters will take a different shape. One angle or distance may work well on axis but not so good off axis and vis versa. I may take over 500 measurements when designing a guide for a particular tweeter to find a compromise that will work on and off axis well. Most of the time I will try to reduce the throat to the size of the dome and if the tweeter doesn't do well I'll start to enlarged it and try different angles to see what works.
The distance from guide to tweeter is an area I've been doing a lot of work with. I'm finding it will have a lot to do with how low and hard you want to push a tweeter. I run my sweeps without protection on the tweeter to get an idea of how close I can get. I can get a much better top end if you don't want to push the tweeter to low. I'm thinking that I may start to look closer at distortion plots and pick a point that I think I can start to roll off the tweeter and work from there. Even how fast you roll off the tweeter will make a difference.
To close the surround will hit at high excursion to far away and the top end will have problems. Finding that middle ground is tough not really knowing how hard I can push a tweeter without damaging it. The gap can change the FR quite a bit by moving the distance by just a half a millimeter. This is also tweeter dependent.
Dave
The distance from guide to tweeter is an area I've been doing a lot of work with. I'm finding it will have a lot to do with how low and hard you want to push a tweeter. I run my sweeps without protection on the tweeter to get an idea of how close I can get. I can get a much better top end if you don't want to push the tweeter to low. I'm thinking that I may start to look closer at distortion plots and pick a point that I think I can start to roll off the tweeter and work from there. Even how fast you roll off the tweeter will make a difference.
To close the surround will hit at high excursion to far away and the top end will have problems. Finding that middle ground is tough not really knowing how hard I can push a tweeter without damaging it. The gap can change the FR quite a bit by moving the distance by just a half a millimeter. This is also tweeter dependent.
Dave
To me, there can't be any compromise on full excursion. As I told you in an e-mail my tweeters touched. Eventually one stopped playing with the WG attached. There was no way to use it without a spacer or it would cause issue with the replacement tweeter. With the spacer the new tweeter measures the same on the top end. I noticed no roll off using a 1/16" spacer to increase that distance. My analyzer is accurate to 1db as set. The XT25-60's Xmax is listed as .4mm and the XT25tg30 that was used to create the WG is .65mm so if it touched with my tweeter, the 30 is going to have more xmax thus it will touch.
The benefit of a WG for me is to be able to cross lower with lower distortion on the XT25 thus it needs more excursion room.
To others reading this please understand that my wave guides were the first two of their type and Dave made these to order. These issues were addressed and not ongoing issues. I'm just casting a vote that a few db up top is not a valid trade off for less excursion IMO. The final result of my project are state of the art highs and I'm ordering another set from Dave. I will just set them up the way I need them.
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I had used XT25 with Monacor WG300 waveguide. It fits perfectly and measured very well. There is no ~12khz dip as with normal dome tweeters due to the phase plug of the ring radiator.
I do have some reservation about the subjective observation of the sound. I thought they do not sound as smooth compared to plain xt25. This is with equalised, flat FR. I guess this is just the nature of having waveguide/horns.
Directivity:
I do have some reservation about the subjective observation of the sound. I thought they do not sound as smooth compared to plain xt25. This is with equalised, flat FR. I guess this is just the nature of having waveguide/horns.
Directivity:
I think I see what's going on. If you remember I was working on a guide for the SS D3004/ 6640-00 when you had ordered yours for the XT25. The guide for the D3004 bolted right up to the XT25 and tested better then the guide I had for it. So that's what I sent you. Looking the D3004 excursion is .2 mm. So I should still be able to use the same guide I'll just have to account for the longer excursion. I haven't sent any more guides out for the XT25 so that's a good thing.
Have you tried Seal n Peel. I use it a lot for drivers and removable panels. Works like silicone but can be peeled off and doesn't have the holding strength.
DAP Seal 'N Peel 10.1-oz. Removable Weatherstrip Caulk-18354 at The Home Depot
Dave
Have you tried Seal n Peel. I use it a lot for drivers and removable panels. Works like silicone but can be peeled off and doesn't have the holding strength.
DAP Seal 'N Peel 10.1-oz. Removable Weatherstrip Caulk-18354 at The Home Depot
Dave
I do have some reservation about the subjective observation of the sound. I thought they do not sound as smooth compared to plain xt25.
Directivity:
Off axis irregularities in dispersion will affect subjective experience. My subjective experience is perfection. I had extensive experience with the XT25 bare. Its better everywhere. This is my WG's result:
Its all smooth transitions. Off axis is stable. My only criticism is that I didnt switch to WG's sooner. Dave nailed it.
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