I'm going to be building some speakers for my dorm soon and I've settled on either Mark K's ER18DXT or David Ralph Chameleons. Has anyone built the Chameleons? From what I've read, they outperform the ER18DXT's, albeit with less bass output, and are also a bit cheaper. I'm just surprised that there aren't any documented builds and that they're not a more popular speaker, given their reviews. I'll be pairing them with a sub, so I don't necessarily need the extra bass from the ER18DXT's. Does anyone have any experience with these?
ER18DXT: The Seas ER18DXT ported two way
David Ralph's Chameleons: SB Acoustics 2-Way Title Page
ER18DXT: The Seas ER18DXT ported two way
David Ralph's Chameleons: SB Acoustics 2-Way Title Page
If you look, I think that tweeter is discontinued. The SB25 was phased out.
Later,
Wolf
I will speak with the real David Ralph, he's the accompaniest for the NY Oratorio Society and the NY Choral Society.
Do you think the SB26STC would work as a replacement or should I bag it and just build the ER18DXT? Or can you recommend another design?
Normally drivers don't just drop-in, so I can't say for certain, but probably not.
I haven't heard Mark's ER18DXT, but he does know his stuff.
Shameless plug, but I have quite a few...😉
See my pics below...
Later,
Wolf
I haven't heard Mark's ER18DXT, but he does know his stuff.
Shameless plug, but I have quite a few...😉
See my pics below...
Later,
Wolf
I have not purchased the SB26. I suspect that it might be a close enough drop-in, but the impedance difference could introduce a small dip around the old tweeter Fs. My mod to fix the original midband dip bumps it up a bit.
You can see that the mod, while improving the SPL response, shows up in the impedance as well. The bumps in response due to resonances is minimized at 1.5k and 3.5K.
Using one of the LR4 @2K crossovers will likely show some change, I don't know how much. My guess is that it would not be a big change.
I have not heard Mark's design, but I have no doubt it is a very good one. I'm using the DXT myself in a 3-way quasi-dipole and am very impressed with it. It does have something of its own character. That is probably due to it's partially controlled directivity.
The SB26 would work well, I may buy one for a re-design to ensure that the Fs impedance difference isn't a problem. The sensitivity of the two look to be roughly comparable. I new that the SB25 was to eventually be discontinued before I completed the design. I also suspected that most would not want to undertake the tweeter mod, but doing just another typical 2-way was not appealing, especially with the issues in the original SB25 and the price was excellent .
I wish that I could do a comparative listening test of my PR version against the Mark's design. The perceived response is, I think, better than the modelling shows it should be. It was very well received at a previous DIY meeting.
Dave
Last edited:
Dave, thanks for such a detailed reply. I actually was able to find two SB25's (the last two in stock!) at Solen, though I now have to wait for Canuck Post.
Looking at your pages on crossover design, it seems that you preferred the 2K alternate due to price and that you could modify the tweeter a bit. However, if one is looking more for aesthetics and doesn't want the felt, would the original 2K (at about $20 more) work comparably? I'd rather not have to use the felt and I don't mind spending some extra on crossover parts, but I'll only do so if the response is equal (or very close) to your 2K-alt with tweeter felt.
If you do ever re-design with an SB26, be sure to link it to your page! I think most people view the ER18DXT to be the cream of the crop when it comes to inexpensive DIY MT's, but your design seems to be able to best it in nearly every way except for bass output. For those of us with subwoofers, I think your Chameleons are a more attractive option. It's just a shame that the SB25 was replaced so quickly. Thanks for all your work!
Looking at your pages on crossover design, it seems that you preferred the 2K alternate due to price and that you could modify the tweeter a bit. However, if one is looking more for aesthetics and doesn't want the felt, would the original 2K (at about $20 more) work comparably? I'd rather not have to use the felt and I don't mind spending some extra on crossover parts, but I'll only do so if the response is equal (or very close) to your 2K-alt with tweeter felt.
If you do ever re-design with an SB26, be sure to link it to your page! I think most people view the ER18DXT to be the cream of the crop when it comes to inexpensive DIY MT's, but your design seems to be able to best it in nearly every way except for bass output. For those of us with subwoofers, I think your Chameleons are a more attractive option. It's just a shame that the SB25 was replaced so quickly. Thanks for all your work!
Last edited:
The felt isn't absolutely necessary, but there will be a different response on any given axis. The difference with/without isn't as big as one might think, largely because the system power response (combination of all axes integrated) isn't affected much, especially for the two small pieces I added (not shown) to make the small triangle. The most import piece is the one between drivers, but the system power response is still not dependent on much on this, either. The change is primarily in the polar response.
The absolute audibility of felt such as this is a continuing debate, most folks just don't like the aesthetics.
That's the only reason I would do it, I'm completely satisfied with the current, modded SB25. I haven't seen good measurements of the newer SB26 to feel sure that it doesn't still have some of the characteristics of the original SB25. It should be just a more refined version, maybe with better manufacturing tolerances.
Without a sub, it would be a hard to beat Mark's design. I'd still like to be able to listen to them side by side, especially in the PR setup. With a sub and without the need for deep bass, mine is a good alternative. I've used it that way. It can integrate with one really well.
Dave
So it it something that is completely necessary? Or is it something that I can get around. I really don't like the look of the felt, but if the added performance is enough that I could actually hear it, then I might consider it. Also, is the felt only required with one of the crossovers, or with all of them? You alluded that it was only necessary with the less expensive of the two LR4@2k crossovers, but maybe I just read this wrong.
It's not absolutely necessary. It was used when I designed all of the crossovers, but it plays a small part. The difference in perceived response is subtle, but it is there. Designs made without it almost always look good on the design axis since many times the off-axis is not considered and the polar response is seldom shown as well. I have found it to make design much easier. Without it, any particular axis will show all of the diffraction that changes on other axes. The optimization should not be done to try to minimize the diffraction on the design axis (except for the step), due to how it changes off-axis, because of the influence on the power response.
A system such as Mark's is a different in that the DXT is a bit directional and has a reduced diffraction signature due to that. You can see this in the off-axis measurements that Mark shows. That said, I use the DXT on my current 3-way and found it surprising that some felt was still needed. Different baffle, no small roundover, centered driver. Each situation is different. But the effects are subtle.
Dave
Ok I think I understand now. I like that, because it means I can use the cheaper 2k crossover. I'll see if I can actually notice a difference w/(o) the felt,but I probably won't since Im coming from some junky Logitech speakers. Thanks for the awesome work you've done to build these. Do you have any more pictures of them? Im curious as to what your little felt triangles look like.
Also, at what point would you crossover to a sub? Im planning on building a smallish sealed sub with a 12 that should go to about 20hz. I was going to xo at 80Hz like many do. Will this work or would you recommend another frequency?
Also, at what point would you crossover to a sub? Im planning on building a smallish sealed sub with a 12 that should go to about 20hz. I was going to xo at 80Hz like many do. Will this work or would you recommend another frequency?
No more pictures at the moment. As far as a sub, I was using a full-range 10" Peerless closed box with an active lowpass, a Dahlquist DQ-LP1. It's been quite some time, but I believe I set it around 60-80Hz. It's a staggered-pole 3rd order variable lowpass. Iwould think that 80Hz for a standard fixed crossover will be close. You can't really say without having measurements of the driver itself.
Mine was the PR configuration, if you going closed box, go no lower than 80. Since this is also in the area of room modes, consider experimenting a bit. Even placement of the sub (and the mains) in the room will change what you hear, so 80 is really a ball-park figure.
Dave
Thats not true - dont spread false informations.
SB Acoustics changed model numbers a while ago and this causes "myths" like that.
The tweeter is known under following names:
1) SB 25 STC-C4 (packaged as pairs / old model name)
2) SB26STC-C000-4 (new model name / TSP all almost identical within tolerance / Single driver package)
SB Acoustics tweaked the new SB26 slightly but only in production quality - its still the "Old SB25" in new "SB26 clothes". So many experienced Speaker builders in germany claim.
I think the big german distributor Intertechnik had a similar comment on there website back in 2009.
The tweeter is very good....a real bang for the buck.....Vifa XT25 is gone for me because SB Acoustics tweeters does the same without the "cons" of the Vifa.
cheers
Alan
Last edited:
I've seen measurements of new SB26. It is an improvement, but there is enough difference between "old" and "new" that I could not make an unqualified recommendation to it being a drop-in replacement. I modified the original SB25 to improve it myself, but although it's better, that version also has a slight difference with new SB26.
The fact that the new version has a new part number says to me that it has enough of a difference that they felt it necessary to distinguish it, so I would not call it spreading false information. Differences exist.
With the new version, I think that the SB26 is a better deal than it was before.
Dave
It looks like the SB26 may indeed be an entirely different driver. See post 42 at this thread.
Last edited:
Hi,
in that thread - the guy claims "The SB25 was a SEAS tweeter that SBA bought from them. The SB26 is an in-house design"
Really? A company located in Wisconsin (USA), which produces in indonesia and with lead designers from europe bought a Seas tweeter design (company in norway with dependances in USA etc) and sold it under their own name? I Remember that they claimed that all speakers are "SB own designs". Mmmh....bad Public relation...come on SB acoustics!
I dont know it later SB decided that the first "renaming" needs a follow up refresh of the Design. I know that 2008/2009 it was only a renaming with slight modifications. SB Acoustics seems not to "exchange" such informations with customers because in 2009 it was rumored as replacement.
If you look at the SB acoustics website - you will see that they are a lot of news and events mentiondes which are from 2010 🙂
cheers
Alan
in that thread - the guy claims "The SB25 was a SEAS tweeter that SBA bought from them. The SB26 is an in-house design"
Really? A company located in Wisconsin (USA), which produces in indonesia and with lead designers from europe bought a Seas tweeter design (company in norway with dependances in USA etc) and sold it under their own name? I Remember that they claimed that all speakers are "SB own designs". Mmmh....bad Public relation...come on SB acoustics!
I dont know it later SB decided that the first "renaming" needs a follow up refresh of the Design. I know that 2008/2009 it was only a renaming with slight modifications. SB Acoustics seems not to "exchange" such informations with customers because in 2009 it was rumored as replacement.
If you look at the SB acoustics website - you will see that they are a lot of news and events mentiondes which are from 2010 🙂
cheers
Alan
Last edited:
Hello,
why do you have confidence?
A friend of mine contacted the german DIY speaker Udo Woehlgemüth, who worked for SEAS on the NoFerro 950 and 650. He said that he cant understand what that "old" design has to do with SEAS?
He thinks that you (and jeff) know things which even the SB Acoustics guys don´t know but...hey....let confidence in Jeff guide your way.
The SB26 is a nice tweeter and sounds really good.
Have a nice week.
regards
alan
why do you have confidence?
A friend of mine contacted the german DIY speaker Udo Woehlgemüth, who worked for SEAS on the NoFerro 950 and 650. He said that he cant understand what that "old" design has to do with SEAS?
He thinks that you (and jeff) know things which even the SB Acoustics guys don´t know but...hey....let confidence in Jeff guide your way.
The SB26 is a nice tweeter and sounds really good.
Have a nice week.
regards
alan
I know Jeff and his many contributions to the DIY community. He's worked with the drivers as well and has contacts in the industry.
Here's a kit design by him: Mandolin Kit.
As stated, they apparently contracted the SB25 through SEAS until they could do the fabrication themselves. When I was designing my system, I was aware that the SB25 was going to be made obsolete. What I was told was proven true. That's partly why I did the design to include modding the SB25, it was scheduled for replacement.
What your friend thinks does not provide any actual insight. Companies frequently contract production. If you have something definitive from SB, that would be informative.
I'm sure of that also.
Dave
- Status
- Not open for further replies.