Happy New Year, 2008
Ring in the new year with some more work on the dipole.
Thursday, September 20, 2007
I want to make a pitch for the DIY events that occur around the country around this time. There happen to be two events in Northern California, actually on the same weekend. I've listed them below. Both of these are the weekend of October 20th. I'm going to the ncdiyaudio one. I'm hoping to go to the burning amp (bay area) one, but that's a lot to ask of my wife...
http://www.ncdiyaudio.claub.net/MeetingList.html
Other diy's that should be happening will be in Mass, at DLR's house-
http://www.htguide.com/forum/showthread.php4?t=27366
In Iowa,
http://home.mchsi.com/~iowadiy2007/index.html
There may be ones in Southern California, the Wash DC area, and a Dayton one, but I don't have links to those. (Feel free to send me a link!)
DIY's are a great way to listen to a lot of different drivers and systems, learn some new tips and techniques. The better attended, the more rewarding. So get out there and get to the nearest diy.
I'm going to bring my venerable RS22528A back to the ncdiy meet. Mainly because I don't have anything newer. I may bring my prototype dipole if I've got and emulation file and can play it using SE or lspCAD emulation for the xover. No chance I'd have the xover finished, but I could demo a couple of different emulation files. You'd still have to listen in mono, but you'd get an idea in any case.
Let's all try to get together and make these great events!!
Wednesday, September 19, 2007
I've been working on my dipole. The pix below was rough prototype one. The home page has the current prototype. I used the rough prototype to see if the FR response was at least doable, then I cut the new baffle. The next question that I wanted to answer was, "What kind of distortion and low end performance can I expect out of it? Since I have a sealed box RS22528A with an F3 in the 55-60 range, I can use this as a reference for how much bass to expect out of a set of 4 RS225's. See the graphs below.
Below you'll find an 3 tone signal at 50 Hz, measured at 40". (roughly 1 meter-my 1meter stick broke!!) First, the sealed single RS225 and then below, 4 RS225's in a dipole configuration, two parallel pairs run in series.
Now, the RS dipole at 50 Hz below
Now, below you'll find two similar graphs at 30 Hz, except the RS dipole is driven 4-5 dB higher. Don't ask why, the point remains.
Again, first the RS225 sealed box-NOTE this is 81dB
Now the RS225 4 driver dipole panel at 85dB
I did a number of other tests to come later.
There is enough data to say that, at least to 50 Hz, the dipole panel is lower distortion. At 30 Hz, even, the dipole panel has overall lower distortion, but you can see from the higher third order products, that it's running out of excursion. And, the level is 4 dB higher for the dipole
So you see, four RS225's will get pretty close to full range. The sealed single RS225 has good output, so the panels should too. At least, that's my preliminary evaluation. Now you might be a little puzzled; the dipole doesn't seem to run out of excursion as fast as I would have predicted. Well, more testing to come.
The other interesting point from all the measurements, including unposted ones, is that the second order products, in general are much, much lower, likely due to the lack of a box causing compliance(ie excursion) asymmetry. Very interesting...
Sunday, August 5, 2007-- Wow. Not much new...;)
The complexities of life have taken more of my time. But, some stuff is happening. I'm working on the prototype baffle for my 2.5 way MMTMM dipole. It will have to have active dipole correction, but otherwise will be passive and only need 2 channels. (you'll need access to the pre out-amp line-in. You could do this with most HT units. )
Pix below to prove that I'm not making this all up. OK, so the prototype is 3 beer ugly. But every mother loves their dipole. It's just for prototyping. The better looking but bogus CAD mockup is below. ?By the end of the year...but which year?
Sunday, September 17, 2006--There's a DIY taking place in October. See the www.ncdiyaudio.com home page for all the details. Though I'm not organizing it this year, I'll be there as well. I'll have my RS22528A there. I don't think I'll be able to bring my portable test setup this time. I'm also working on a Peerless ported 2 way in the same 3/4 box. But I doubt it will be ready.
Sunday, July 9, 2006--Added results for the Accuton C44, Dayton RS52, Morel MDT55, and the Scan Speak 12M4631G
Saturday, June 24, 2006--Added results for the Scan Speak AirCirc 6600 tweeter and Peerless HDS 810921 1" tweeter.
Saturday, March 10, 2006--My field trip to Tymphany.
Monday, February 13, 2006-- You probably know this, but here's a link to the XG18 tests. Also, in case you haven't had enough, here's more RS28A testing data.
Wednesday, January 18, 2006--For what it's worth. I tested a Seas 27TBFC/G at 109 and 112 dB at 1k and 2k, and the graphs are shown below.
I did this because it often comes up that either my levels are too high, or too low. Well, there actually are differences at different levels. I can't print and post every level I test. Suffice to say that the Seas does very well. The TDFC also does very well. I didn't post/save these, but the results were similar. Very few drivers can tolerate this three tone stimuli at 1k or 2k this well. The bar is set pretty high with these drivers. It could be beat, I suppose, by a driver with better second order products. Perhaps the MDT33, though those drivers have other issues. See David Ralph's comments. Too bad, because there appears to be much potential.
I've also got some tests of the Vifa XG18 coming up. A bit different from Zaph's, though not markedly so.
Monday, January 9,2006--A quick testing of another RS28A pair.
Sunday, December 11, 2005--Finally, it's finished. Sort of. Part 2 of the RS22528A project is here. I will add more curves over time if I do interesting measurements, but it's more or less complete. Use the link below or go to the projects page.
Saturday, November 26, 2005--Finally, it's here. Part 1 of the RS22528A project.
Wednesday, November 23, 2005--Just a tease on the RS225/RS28A two way. I have run multiple FR curves, on and off axis, have polar response plots, as well as distortion plots.
I think that it will shed significant light on:
1-the low end and midrange performance of the RS225
2-the ability to crossover low and the distortion characteristics of the RS28A
3-the off axis response of this particular crossover topology including listening window, average and polar plots
3-comparisons are made to two similar sealed box two ways, the Usher listed on my site, and an undocumented SS8545/9500 two way.
I will try to have part one ready by the end of Thanksgiving weekend, and part two, with pair matching measurements and listening evaluations, done by the end of the year. I'm still listening in mono because, well, the second crossover is still in little pieces...
Wednesday, November 16, 2005--Added another update on the RS225/RS28A sealed box project. Again, check out the projects page. This is probably the last update until I actually get the entire project competed along with a complete set of FR, off axis, and distortion curves.
Saturday, November 12, 2005--Added test data on the RS125 compared to the RS150.
Monday, November 7, 2005--Added test data on the Morel MDT33 and Supreme 110. It's a bit limited, but I think you'll find it interesting nonetheless.
September 4, 2005--An update on the RS225/RS28A sealed box project. You can find it in the projects page.
Sunday, August 28, 2005--Added test data on an OEM tweeter, not generally available to the DIY'er. It's a Logic (VIfa) XT25. It's a small faceplate, neo version of the standard XT25. Unfortunately, it's performance is undistinguished. You can find the results here. As usual, it's not listed anywhere else. I really should update the rest of my site.
Sunday, August 21, 2005--Added test data on the Peerless HDS exclusive series 7" woofer. Again, until I update the rest of my site, you can only find the link here.
Sunday, July 31, 2005--Added test data on the Seas 27TBFC/G. For now, you can only find the link from here.
Sunday, July 10, 2005--Added a primer on linear distortion. I think it sums up my understanding well. That doesn't mean everything is exactly correct. I took quite alot of liberties to try to make it conceptually understandable to everyone, and I'm not a systems engineer or a mathematician whose interest is in all things Fourier. If you find an error or poor explanation, please email me and let's discuss it.
Friday, July 1, 2005--I've updated my site. I'm still trying to keep it very simple, but it was starting to get a bit unmanageable. This site should be easily viewable with 1024 or 1280. If you're still using 800 or smaller, get a new graphics card and monitor. You can get a 17 or 19 inch LCD monitor that will do 1280 for well under $300, even close to $200 if you look hard.