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Old 26th June 2011, 05:50 AM   #1
Frosteh is offline Frosteh  United States
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Default David Ralph Chameleons

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
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Old 28th June 2011, 12:42 AM   #2
Frosteh is offline Frosteh  United States
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Anyone?
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Old 28th June 2011, 01:47 AM   #3
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Originally Posted by Frosteh View Post
Anyone?
If you look, I think that tweeter is discontinued. The SB25 was phased out.

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Wolf
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Old 28th June 2011, 01:49 AM   #4
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I will speak with the real David Ralph, he's the accompaniest for the NY Oratorio Society and the NY Choral Society.
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Old 28th June 2011, 05:05 AM   #5
Frosteh is offline Frosteh  United States
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Originally Posted by wolf_teeth View Post
If you look, I think that tweeter is discontinued. The SB25 was phased out.

Later,
Wolf
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?
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Old 28th June 2011, 06:15 AM   #6
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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
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Old 29th June 2011, 01:13 PM   #7
dlr is offline dlr  United States
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I will speak with the real David Ralph, he's the accompaniest for the NY Oratorio Society and the NY Choral Society.
Must be a different David Ralph.

Dave
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Old 29th June 2011, 01:35 PM   #8
dlr is offline dlr  United States
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Originally Posted by Frosteh View Post
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?
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.

Click the image to open in full size.

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 by dlr; 29th June 2011 at 01:56 PM.
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Old 29th June 2011, 04:10 PM   #9
Frosteh is offline Frosteh  United States
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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!

Last edited by Frosteh; 29th June 2011 at 04:22 PM.
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Old 29th June 2011, 07:22 PM   #10
dlr is offline dlr  United States
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Originally Posted by Frosteh View 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.
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.

Quote:
If you do ever re-design with an SB26, be sure to link it to your page!
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.

Quote:
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!
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
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