The Center of the Sun - photos (1 Viewer)

[Patrick Sun]

Greg, thanks, for the link. I read it, and while I would like to do it, I'm a bit hesitant. Here's the lazy man's way: Is there a correction factor I can add in for last 4 values of the high end for
12.9KHz
16.25KHz
20.48KHz
when using the digital version of the RS SPL meter?
BTW, I made some more changes, and am getting pretty close to a "finished" product with the Vifa D27TG45-06 (I know, I've already been chastised for using this one instead of the Vifa D25AG05-06 - I already bought the D27 and might as well have some fun with it before going for the D25), or perhaps just keep my old Philip tweeter and resign the tweeter crossover for it to suit me. The graph from 45Hz to 10KH looks relatively flat +/- 3dB currently.
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[Greg Monfort]

I'm sure there is, but if it's not listed at the site....

WRT tweeter selection, that's such a personal choice that I can't comment beyond the fact that I don't like Vifa period. I prefer horn, ribbon, or electrostatic, but I have a couple of Phillips tweeters in the closet biding their time that are so...right.

GM
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Loud is beautiful, if it's clean

 

[Patrick Sun]

Greg, the only reason to go back to the Philips tweeter is to keep consistent components for all 3 of my front speakers, now that I'm not as worried about its high end performance.
Check out my day of tweaking:
Well, I basically spent today fiddling around with the crossover network to smooth out the response within +/- 3dB. This is not necessarily hard work, but it is time consuming, and lugging my CC speaker back and forth from the testing spot to the dining table can be construed as working out.
Given the deficiencies of my RS SPL meter in the high end of audio spectrum, I'm not going to worry about the frequencies past 12KHz for now. You'd have to be a dog to enjoy those frequencies anyhow.
Due to my concern that my original Philips tweeter was not too good (due to my not realizing the RS SPL meter's usable bandwidth being 40-12KHz), I decided to install another tweeter, the Vifa D27TG45-06, and measure/listen to how it sounded as it was integrated to my CC speaker. I had to drill some more holes through the front panel, and couldn't install T-nuts, so I just used the nuts that came with the original machine screws. That was the easy part.
I spent some time getting a preliminary tweeter high pass crossover design (2nd order with the break frequency at roughly 4650Hz) plus a tentative L-pad (around -3dB to start), bought some resistors, capacitors and inductors to give me a range to play around the crossover with. The midrange and woofer crossover networks had already been tentatively designed.
Here's 7 graphs that summarize my whole day as a process of trial-n-error to get the response smoothed out:

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[David A. Frattaroli]

Pat, if you haven't already, check out ValueWeb.com. That's the host I use for Link Removed
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[Patrick Sun]

David, thanks for the link, but I need more web space that the $20/month plan allows. I need about 400-500MB of space for all my DIY projects and other photo-heavy endeavors, and I'm determined to only pay $20/month or less.
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[Brian Bunge]

Pat,
Weren't you looking for some straight 6" legs to mount on the bottom of your sunosubs? You'd only been able to find angled legs recently, correct? These are tapered but appear to mount completely vertical. I found quite a few today at the Home Depot in Conyers. I only live about 10 miles away, so if you still need them let me know.
Brian
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[Patrick Sun]

Brian, if they are the wide triangular-shaped leg mounts (for under a table top), then they take up too much space on my bottom endcap (I had considered it when I was at Home Depot a few weeks ago myself). If they are the square-shaped straight leg mounts, then yes, I'd be interested!
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[Brian Bunge]

Pat,
Actually, the ones I saw were round. They were maybe 1" in diameter at the top and then tapered down to the bottom. I didn't notice any square ones. Or are you talking about the actual mounting plate that the leg screws into? I didn't really take a look at those, just the legs themselves.
Brian

 

[Patrick Sun]

Brian, oops, I'm talking about the leg mounts (not the legs themselves), which are about 2"x2" square with 4 screw holes to screw into the bottom endcap, and has a center screw hole for the actual legs to screw into. Sorry for the confusion. It seems HD is getting out of the table leg business and selling out their table leg stock.

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[Greg Monfort]

Pat, measuring anywhere but in the final location is counterproductive. You want the CC to mimic the L-R speaker's FR as close as reasonable while sitting atop the TV, not on some floor stand. For sure you also want to use the same tweeter, as it's this BW that primarily gives imaging.
GM
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Loud is beautiful, if it's clean

 

[Patrick Sun]

Greg, I'll re-double my efforts, probably on Thursday as time permits. At least now, I have an idea of what I'm doing, so I should be able to get better results in half the time (if I have the right component values laying around). And I'll pop in the original tweeter as I make a 2nd go at it.
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[Patrick Sun]

Greg, here's one last graph of the CC's response on top of the RPTV with the Vifa D27. I could live with this response. I measure from 1m away and 3m away (about how far I would sit from the CC speaker normally).
Graph 8 - I must be in a weird null at directly 1m away from the CC where I'm taking my SPL readings, the low end response if better from 3m than 1m, if you factor the loss in dBs as the square of the distance in increased.
Now, I'll go back to my old Philips tweeter and see if things get better or worse.
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[Patrick Sun]

Update: While going back to my old Philips tweeter, it is taking a lot of padding to get a decent SPL on the mid to high end. I picked up some more resistors for new L-pads today, as well as some more inductors and caps to play around. I also picked up a Vifa D25AG-05 tweeter to see how it sounds (I've been advised that it's a bit smoother than the D27TG-45).
I'm thinking about going back to putting the woofers in parallel to compensate for the dropoff in bass that you see in this latest graph with the CC speaker now in place over the TV, amazing how free space measurements can vary when compared to 1/2 space measurements for bass response.
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[Patrick Sun]

Day 9 (3/8/01)
Now I embark on getting my original tweeter, the Philips AD11600, integrated into the CC speaker to match my main speakers (I'll be re-doing their crossovers as soon as I'm done with fixing the response with the Philips tweeter).
I use a starting point from the previous design with the Vifa tweeter.
Graph 9 : It's obvious that the Philips tweeter has a higher sensitivity (I'm guessing around 94dB/1W/1m) and can see the high end hump from it.
Graph 10 : I put in a L-pad that lowers the tweeter output by almost 8.5dB using resistors of common values (I needed 5 ohms//5 ohm L-pad combo, but had to settle for 5.1 ohm//5.1 ohm combo since I had to series a 1.1 ohm with a 4 ohm resistor to get close to 5 ohms. This definitely helped get rid of the high end hump, but it's pretty rocky, so I try to get the crossover slopes to line up better.
The next couple of graphs show me going the wrong way on smoothing out the response.
Graph 11 : I revert back to a 1st order midrange lowpass, and it creates more ups-and-downs. This wasn't a good thing.
Graph 12 : Keeping the 1st order midrange lowpass, I move the woofer and midrange crossover point near 700Hz to try and close of the valleys. Well this just raised the high end on a gradual, but upward sloping response.
At this point, I decide I'm not getting anywhere going down this road, so I revert back to my design from Graph 10.
Graph 13 : I ripped out all the components from the design in Graph 11 and get back to the design in Graph 10. I was able to obtain actual 5 ohm resistors, so the high response is smoothed out just a tad more than in Graph 10, though it now has that hump around 800-2000Hz, so that's what I try to smooth out next.
Graph 14 : Well, I tried moving the midrange lowpass frequency to almost 800Hz, so that produce a nice fat dip from 250-800Hz.
Graph 15 : So, I go in the opposite direction and move the midrange lowpass frequency further lower to 400Hz. Now, it's a little rocky, but within +/- 3dB throughout the audio spectrum of concern, so this is where I decide to stop the design process.
I plop the CC speaker on top of the TV and proceed to take measurements.
Graph 16 : Again, the low end frequency response suffers with the CC speaker on top of the TV, but I'm not concerned as most of that gets filled in when I run the CC speaker as a "SMALL" speaker, and let my subwoofer do most of the heavy lifting. The 1m response is also within +/- 3dB throughout the audio spectrum of concern, as well as the 3m response, though the room gives the high bass region a little hump from 200-500Hz, but I can live with this. The high end response rolls off as expected due to the RS SPL meter.
So, at this point, I'll do some listening with the Philips tweeter in place and evaluate it qualitatively.
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[Patrick Sun]

Day 10 (3/11/01)
Okay, so I listened to my CC speaker, and I found it a little dull, so looking back at graph 16, I noticed my high response was dying quickly after 8KHz at my seated position nearly 3 meters away, so I decided to work getting more high end output at 3m away.
Graph 17 : I change the L-pad which gives me -8.4dB of attenuation, and used the original -3.75dB L-pad. This gave back my high end, but it was little too bright.
Graph 18 : To bump the high end down, I went with a L-pad which gives me -6dB of attentuation. This was getting me close. I notice a slight trough in my midrange, so I will raise the midrange next.
Graph 19 : I changed up midrange L-pad, just leaving a 1 ohm resistor in series with the lowpass network. I raised the midrange output by 1dB from 2KHz-4KHz. Now the midrange and the high end are more on axis with their SPL output.
I think now I'm done with the Philips tweeter in the CC speaker. Unless I want to do something about the baffle diffraction that reduces my bass output on the low end (worst case is by 6dB). I may leave it alone unless the male vocals are too thin. If I go with a parallel woofer connection, I could gain back the loss from the baffle diffraction, maybe I'll try that when I have some more time.
Next, if I can make the Vifa D25AG05 tweeter fit into the tweeter hole (and mounting screw holes) easily, I'll see use the Vifa D27 crossover design as a starting point, and get the response smoothed out and see if I like how it sounds compared to the other 2 tweeters.
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[Charlie G]

Pat, have you thought about doing a pseudo 3.5-way setup? Klipsch uses them on thier centers.
You put a high-pass filter on ONE of the LF woofers, so it only comes up to about 300hz, and the other one also plays this section, and all the way up to the crossover. I guess something about the fact that only one woofer has to blend with the midrange now improves the sound.
Anyway, my RC-3 center is a 2.5 and it works great.

 

[Patrick Sun]

Charlie, interesting idea, but the way my crossover points work in my design, the woofers get crossover around 450Hz, so that's a pretty narrow back of operation for one of the woofers if I cross it over at 300Hz and then 450Hz. Now I could see how this would work if the woofer was getting crossed over at 300Hz and then around 2000Hz (most typical 2-ways cross over around 2200Hz).
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[Patrick Sun]

Day 11 (3/15/01)
So I'm not done with the Philips tweeter. Here are my final final final graphs/crossover networks for this tweeter. I have graphed the response for the center channel speaker operating in the Small and Large speaker mode, this will be important when I wire up the woofers in parallel later on.
Graph 20 : I rip out the L-pad on the midrange crossover, and change the midrange's 2nd order high pass into a 1st order high pass by taking out the capacitor. This doesn't produce good high end results (but it was expected, thought I wanted to see what would happen when I took out the midrange L-pad).
Graph 21 : I change the midrange high pass back to a 2nd order to smooth out the high end. The low to midrange looks a little too humpy now without the pad resistor.
Graph 22 : I put back the 1 ohm resistor pad in the midrange to smooth out the low to midrange. This is about as much as I can do unless I totally redesign the crossover. So I'm calling this my final crossover for when the woofers are connected in series, even though my low end response is lacking.
Now, I wire up the woofers in parallel to get some low end back (up to 6dB if I'm lucky).
Graph 23 : Using my last crossover as a starting point, I connect up the woofers in parallel, and swap out the woofer crossover components. Using a low pass crossover point of 400Hz for the woofer, I get this big hump/spike around 400Hz, so I decide to fiddle with the high pass of the midrange to smooth out the response in the 300-700Hz range. If you'll notice, my low end has dramatically come back to life since I gained woofer output with each woofer connected in parallel. It causes a drain on the amp, but I should be okay.
Graph 24 : I change the midrange's high pass crossover point from 460Hz to 640Hz to spread out the hump. It appears I was successful in taming that 400Hz peak, and notice when the speaker is set to Small, the response is relatively flat +/-3dB from 80Hz to 12KHz (I'm discounting the upper high end due to my RS SPL meter's high end deficiency). I can live with this crossover setup with the Small speaker setting for the center channel. So I'll give this setup some listening time and see if it's a keeper.
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[Patrick Sun]

Day 12 (3/17/01)
Minor confession: I've been using an 11 year old midrange that I salvaged a couple of years ago, so I decided last week to order a younger one (same vintage as my main speakers). I got the new driver yesterday (thanks, Madisound !) Here is a graph showing slight improvement in the upper midrange after replacing the old midrange driver. Now all the drivers are pretty much "new".
Graph 25 : I got a little smoother response from 800Hz-4000Hz with the new midrange. This graph also shows the difference between using an amp capable of a 4 ohm load (my HK PA5800) vs. an amp that limits the power (my Sony DB930 receiver), the difference is basically 3 dB across the board. I've included my raw numbers (yellow) for the HK response, it's got a decent response from 80Hz to 10KHz before my RS SPL meter dies on me.
I've thought about putting in a Zobel across the woofers (would need a 5ohm/18uF Zobel) but I don't think it would clean up the woofer impedance too much at the 400Hz range. If I have the parts, I may try it any how (I think I have to use a 20uF cap though - all I have in that range).
Today I listened to a lot of mono-music (mainly the left channel of many CDs in the large speaker mode with no sub hooked up) just to listen for the vocals and whether or not that sounded right to me. I noticed I have a slight dip at the woofer crossover point near 500Hz, but I've found that I can EQ it by giving a 1 dB or 2 dB bump at 500Hz on my receiver. It gives back the manliness to male vocals, and they now don't sound thin at all. Female vocal were tamed a bit. When I listen to the CC speaker with normal TV programming in Dolby Pro-Logic and DVDs in DD/dts, the vocals sound right to me now. Sometimes I will have to fiddle with the Pad of the CC speaker on the receiver because I need to fix my crossovers in my main speakers (pull up the midrange, pad down the tweeters). Overall, it's getting to a point where I'm almost ready to try the other Vifa tweeter and then veneer the box.
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