The Center of the Sun - photos

**John Holmes** · 23 February 2001, 02:33 Friday

Patrick,
You never fail to amaze me with your attention to detail. Looking good. I feel like I'm waiting for my own to be done.

"I came here, to chew bubble gum and kickass. And I'm all out of bubble gum!!!" My DVD's

**Andrew Pratt** · 23 February 2001, 11:43 Friday

Pat you never cease to amaze me with your photo documentation of your projects...

**Patrick Sun** · 25 February 2001, 19:57 Sunday

Andrew, wait until you see my crossover networks. It is a thing of beauty (though it was quite time intensive).

Well, folks, The Center of The Sun (COTS) is operational! I worked about 5-6 hours today to get it done. I finalized all the wiring of the crossover and the connections to all the drivers. I'm still waiting on the final version of a 20uF polypropylene capacitor, but I'm using 2 10uF electrolytic caps just to get the sucker working. Hopefully I'll get the final cap in the mail tomorrow via UPS. I made my ports, and installed them, as well as screwing in all the drivers (20 screws! Ack!) by hand (can never be too careful not to puncture a hole in the drivers).

Currently, I have it playing as the left front speakers, and I'm pretty darn impressed at how close it sounds to my right front speakers. It's eerie. It doesn't sounds like my current center channel speaker, which has always been a little boxy sounding to me.

I could run 2 of these COTS as mains and most people wouldn't be able to tell them apart from my other mains. In fact, it wouldn't take much to convert this design to tower speakers at all either.

I'm also surprised I got all my wiring and soldering done correctly on the first shot.

I have the 2 woofer drivers hooked up in series, and used the crossover design for that particular configuration. It doesn't seem to have an adverse affect on the overall sound quality. I'll try to run some measurement of the 300-600Hz range to see if I have a dip there, but I'll do this later after I'm take a well deserves break for the rest of the day.

BTW, this COTS is truly a heavy beast! I'm going to have to install another wire shelf to help out in the weight department because I think my RPTV would not withstand so much weight on top of it well. I'm guessing it weighs around 30-45 pounds with all the drivers, crossover components, and MDF in it.

I'll try to have some photos up when I finalize the crossover with that 1 last capacitor.

PatCave; HT Pix;Gear;DIY Projects;DVDs; LDs

**EMT** · 26 February 2001, 07:06 Monday

Pat,

Sounds like you are making excellent progress. As always, your photo documentary and narrative on the design and construction are an interesting and informative look at the process of building a speaker. Thanks for sharing it with us.

So, any comments on how you will finish the COTS? Paint? Veneer?

Ellen

**Patrick Sun** · 27 February 2001, 00:58 Tuesday

Ellen, I'm not quite sure what I'll do for the final finish of the CC speaker. Probably veneer, but I need to investigate and do some experimenting just so I know what I'm doing when I start the veneering process. I don't think I'll paint it (MDF and paint don't mix, even if I primer it). Any ideas for me?

Day 5 (2/22/01)

Photo 73 : I test for fit on my bracing, and determine I need to sand down the inner walls just a bit, so that's why the sander is there.

Photo 74 : The long brace needed a bit routed off (like Lincoln logs), and I applied glue on the required surfaces.

Photo 75 : The glue is also applied to where the bracing will be attached. I use a pen to draw a pair of lines where the brace should be aligned.

Photo 76 : Clamps are placed to squeeze the bracing's glue for a tight bond.

Photo 77 : The cabinet is flipped over, and I apply glue for the other long bracing piece.

Photo 78 : Again, clamps are used to squeeze the bracing for a tight bond.

Photo 79 : More glue, more bracing, this time, it's the piece that goes along the side of the cabinet.

Photo 80 : Using the clamp, and the short piece, I position the side bracing between the 2 lines I previously drew for final placement (not shown). This is to ensure the fit of the "T" style bracing I'm using.

Photo 81 : I glue the other side bracing.

Photo 82 : This gives a better picture of the placement of the side brace (I also glue the bracing's bottom which butts into the inside front panel).

Photo 83 : Here's a shot of both bracings being clamped for a good couple of hours (or more). You can also see all the glue I apply to the inner walls and the long pieces of bracing. Go nuts with the glue!

Photo 84 : This is a close-up of the clamping and how the "T" style bracing is being utilized. At this point, I haven't glued that short piece of bracing yet.

Photo 85 : I just remembered to drill holes through each inner wall so I can feed the woofer drivers' wires to their terminals. As you can see it's a tight fit with the power drill. I recommend drilling the holes earlier than this, before installing them into the box.

Photo 86 : I test for proper hole size by feeding a piece of wire through the hole I just drilled, this is the second wall. I needed 2 passes to get the hole oblong enough to fit the speaker wire through it.

Photo 87 : Finally the top little piece of bracing is ready to be glued to the side bracing to form the "T".

Photo 88 : There's lots of surfaces to apply glue for these little short pieces of bracing.

Photo 89 : More clamping is involved in getting the tight bond from just glueing the bracing to the cabinet's inner walls.

Photo 90 : I quickly get both little pieces of bracing glued into place and clamped. I give the glue of the bracing the entire next day for the glue to dry.

Day 6 (2/23/01)

Photo 91 : It's now time to caulk the inner seams of the cabinet with all the bracing in place.

Photo 92 : As you can see, I've caulked the backside of the cabinet inner seams.

Photo 93 : Finally, all the inner seams are caulked.

I wait an hour for the caulk to dry. While it's drying, I start on the crossover network. This takes forever and a day to do. There's lots of places where you just have to be patient, and do all the little things to get it wired up correctly.

Photo 94 : I originally wanted to put my tweeter and midrange crossover components on 1 board, and the woofer on another board, but it just wasn't going to happen, I ran out of real estate on the board for both the tweeter and midrange, so I put the midrange on one board and the tweeter and woofer on the other board. This part took a while since I was playing around with the best way to lay everything out, so to get to this point, I must have spent 1-2 hour mucking around. There is one capacitor missing (I used an electrolytic cap in the upcoming photos just to get the crossover running while I waited for the polypropylene cap to arrive).

Photo 95 : I mark the holes for the terminals (black with screws on them) and drill them. I got the terminals and the other terminal mounts at Radio Shack.

Photo 96 : More drilling of holes for the components on this board. I do the same with the other board, of course.

Photo 97 : Here is what the boards look like with most every component tie-wrapped to the board. The terminals are attached with little machine screws and nuts (bought at Home Depot).

Photo 98 : Here's a shot of me screwing around...actually getting the components connected to one another based on the crossover I cobbled together. This board is the midrange crossover. It's always a good idea to keep your inductors oriented 90 degrees from one another.

Photo 99 : Just a shot of most of the bits and pieces I used, like male and female spade connectors, and the ring terminal connectors (I spent the next day getting all my inputs terminated with the ring connectors for a nice clean fit, it was a tedious, and yet, therapeutic exercise. I use the insulated female spade connectors when I knew it was going to be used to connect to a driver (to avoid shorting out the connection). The crimper is a godsend. Can't do good connections without it. At this point, it's around 3 a.m. and I'm tired, so I go to sleep.

Day 7 (2/25/01)

Had a wedding to go to on Saturday, and just didn't feel like working on this project, so I took the day off. Now's it's Sunday.

Photo 100 : Doesn't my cat look so impressed with me? I bring in the cabinet, and the drivers because it's time to put it all together!

Photo 101 : These are wires for the woofer drivers. For the connections to the crossover network, I crimp on the insulated female spade connectors to avoid short circuits (If you're cheap, just wrap them up with electrical tape, red for the positive lead, black for the negative lead). I always wrap the negative lead wire with black electrical tape to avoid confusion later. The female spades that will be connected to the woofer driver is not insulated because they will be a couple of inches apart when connected to the driver.

Photo 102 : A shot of me crimping these nifty ring terminal connectors. They allow be to really neaten up the crossover on the input terminals where I have make those little bitty jumpers for provide the positive and negative terminals for 3 sets of drivers (seen on the left side of the board). I had to solder 3 inductors in series to get 8 mH of inductance (FYI). And there's the electrolytic caps I am using temporarily until I get my poly cap (needed two 10 uF caps parallelled to get a 20uF cap) for the woofer crossover.

Photo 103 : Here's a close-up view of both crossover board slipped into their new home.

Photo 104 : Here's a wide view of the backside of the speaker with the crossover installed. I measured it just right to fit 2 levels of crossover components.

Photo 105 : I install the midrange driver, and then connect the wires for the tweeter. My other kitty is fascinated by the whole process.

Photo 106 : Next up is one of the woofer drivers, notice I don't need the insulated female spade connectors.

Photo 107 : Make sure you take your time screwing in the driver screws. I use my other hand to shield the head of the screwdriver from the cone, lest it slip and puncture it. This is where using T-nuts really pays off. I think I used 10-24 1.5" machine screws for the woofers and midrange. Again, kitty is mesmerized by the process.

Photo 108 : What can I say, kitty (Fred) just can't wait for me to finish up so I can play with him.

Photo 109 : The tweeter screws are 8-32 1.5" machine screws IIRC. I use the corresponding T-nuts for the tweeter driver.

Photo 110 : And here is the midrange. This is laborious since I dare not use a power drill.

Photo 111 : The other woofer's wires are connected to the driver.

Photo 112 : Finally, all the drivers have been screwed into all the front panel.

Photo 113 : Here's my testing which wood screw I want to use for attaching the back panel to the cabinet. This one is a #6 wood screw. I test for depth as well as "unscrewability" in case I need to get back inside the cabinet later.

Photo 114 : I test a #8 wood screw, and this is the one I decide to use. It was harder to strip its phillips head, so that was part of my rationale to use it over the #6 wood screw.

Photo 115 : I mark where the bracing is the strongest, so I can intersect some lines to get the screw hole placements in a moment.

Photo 116 : Just thought that it was really tough to get the back panel off if I can't push a hammer through the woofer hole (which I had been doing before I screwed in all the drivers to the front panel). I drill 2 holes, and loop some speaker wire through the holes (with 2 knots for added strength/support when I pull on it later).

Photo 117 : This is what the back panel will have hanging out of it for the interim (I'm thinking about putting in a "handle" later). But it works, and you never see it once I put it in its place in the HT.

Photo 118 : I connect the crossover leads to the terminal leads of the back panel. I use a long piece of speaker wire for flexibility when I take off the back panel and don't want to disconnect it from the crossover.

Photo 119 : This is foam weatherstripping which I'll apply the bracing to produce a good seal mainly for the woofer enclosures.

Photo 120 : I apply the weatherstripping all around the bracing. Yes, I forget to put it on the inner walls, but I'll be back inside once I finalize my woofer crossover components, so I'll fix that at a later time.

Photo 121 : It's finally time to close up the cabinet.

Photo 122 : Remember those marks I made? Now I use them to make the intersections which give me the holes to drill for the wood screws.

Photo 123 : I use an 1/8" bit to make the pilot holes for the wood screws.

Photo 124 : To countersink the wood screws, I use a thicker bit to drill a depth of 1/8" or so. The masking tape is used for the depth marker.

Photo 125 : The screws are screwed into the bracing nice and evenly. I confess, I forgot to include additional depth for the foam weatherstripping, so the back panel is not completely flush with the rest of the cabinet. I will remedy this by routing out a perimeter 1/16" deep, 1.75" wide, on the inside back panel. I got the medium compressible weatherstripping. Doh!

Photo 126 : The last thing to do is create the ports for each woofer. I need roughly 7" long ports 2" wide. I found these 2" wide, 4" long ports, so I bought 4 of them with the intention of sawing off 2 of the ports to use to extend the other 2 ports. I love my PVC pipe saw, just handy for this application. I wound up having to saw it off around to get the 3" of length for each pipe add-on.

Photo 127 : Both of the chopped down ports. They get chopped down where their fins disappear.

Photo 128 : I use black electrical tape for the adhesive on the inside and outside of the port.

Photo 129 : Here's the total new length for the port.

Photo 130 : Ta-da! Once the ports have been inserted and hammered into the port holes, the center channel speakers is finally operational.

Photo 131 : Here's a shot from the left corner.

Photo 132 : And here's a shot from the right corner (sorry, proud papa operating the camera!)

Photo 133 : Since I can't connect the CC speaker up to my current setup (have to re-arrange everything to fit this speaker over the RPTV), so just for fun, I listened to it as the left speaker just to see if I had gotten my connection all wired up correctly. Amazingly enough, I got my crossover hooked up right on the 1st try. Oh yeah, next to it is my Giant Pickle Sub.

Photo 134 : A gag shot of the CC speaker incorporated into the HT setup.

Photo 135 : Here's what my HT setup looked like before I moved everything around to accomodate this new CC speaker.

Photo 136 : This is how my HT setup looks after I moved my HT gear around. I had to relegate my Harman Kardon PA5800 5-channel amp into the closet behind the subwoofer where my subwoofer amp also resides (but that's okay, I rarely need to "see" it anyway).

Photo 137 : Here is how my current HT looks like with the new CC speaker in place. I'm tempted to forego the veneering as the front panel's color is a close match with my mains, and it's not like I'm impressing anyone with my stuff anyway.

Day 8 (2/26/01)

Well, I have just a bit of testing to do to finalize my woofer driver crossover. I did some measurements of the CC speaker with the woofers connected in series. I'll post the graph as soon as I can get the numbers all graphed out.

But, from a cursory glance at the numbers, I can tell that I will need to connect the drivers in parallel to get a 4-6dB increase in the SPL output from 400Hz and down to even out the output from the rest of the drivers.

I calibrated my new CC speaker with the rest of my system, and I needed to bumped up the center channel speaker output by +2dBs on my receiver. I'm thinking when I go with a paralleled woofer load, I won't have to boost the center channel output much at all.

Stay tuned for the rest of the story.

PatCave; HT Pix;Gear;DIY Projects;DVDs; LDs

**EMT** · 27 February 2001, 06:12 Tuesday

Pick up a copy of Mike Burton's Veneering: A Foundation Course at your local book joint. Should give you all of the info you need to do a good veneer job.

**Bing Fung** · 27 February 2001, 09:56 Tuesday

Once again you have put on a clinic PL@!

Excellent Job

Bing

**Patrick Sun** · 27 February 2001, 12:10 Tuesday

Ellen, thanks for the book tip.

Bing, thanks for the kudos. I don't even know if I could do projects without documenting them. It must be some O-C thing I got in my blood.

Here's a graph of the CC's frequency response with the woofers connected in series.

I can't really explain the dip near 100Hz. If I wanted to keep the woofer in series configuration, I am thinking about either taming the tweeter with a different set of current divider resistors. But I think the better thing to do (to make up for the 1/2 space baffle of the CC) is to change the midrange current divider to mimic the tweeter's current divider to gain some more dBs from 450Hz-5000Hz. But this would leave me with a little less SPL on the woofer end relative to the midrange/tweeter. But, depending on how much I gain when I parallel the woofer, I'll see how much I want to change the L-pads on the tweeter and midrange crossover.

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**Patrick Sun** · 28 February 2001, 01:11 Wednesday

Just to clarify the graphs, here's the graph with measurements taken at 1m.

Here's the previous night's graph with measurements taken at 2m.

They basically show the same thing.

Believe it or not, but that tweeter is really attenuated already about -4dB (down 60% from non-L-pad value), so what I'm going to do is take out midrange L-pad to boost the midrange by around 3dB. In the original crossover plans from 10 years ago, there was no L-Pad for the midrange crossover. So I'm going backwards here.

I did a quick measure of one of my main speaker, and here's the graph of the main speaker at 1m. Sonuvagun, it looks sort of like the midrange trough from the center channel speaker measurements. The woofer is definitely on par with the tweeter output though. I had always thought the male vocals were a little thin on my speakers, now I know why. Looks like time to overhaul the main crossovers as well and rip out the L-pad on the midrange crossover. And since I have the new caps from Madisound, I can put those into the networks.

I'll do some more soldering tomorrow, and connect the woofers in parallel, put in the other woofer crossover components (I'll be using a 2mH inductor and a 80uF cap, so I can get rid of the DCR from the 8mH induction from the series woofer crossover). I'm hoping the parallelled woofers will boost that low end enough to be on the same sensitivity as the tweeter/midrange. We'll see. I may be brave and take out the midrange l-pad at the same time, then take my measurements and report back.

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**Patrick Sun** · 05 March 2001, 14:08 Monday

Okay, I made some changes to the L-Pads of my midrange and tweeter crossovers, but something happened to my low end response. If anyone can offer some ideas, I'd be grateful. You can refer to an earlier graphs which shows the low end response of the 2 woofer hooked up in series with one another.

Now, I've hooked up the woofers in parallel, which should give my a 6dB bump, but instead, it depressed the hell out of the low end response under 112Hz. Check out these 2 graphs:

Graph A : Woofers in parallel, Bypass Cap paralleled with the tweeter series L-Pad resistor.

I included this 2uF Bypass Cap to smooth out a 12KHz hump, but it just wrecked my tweeter response, especially with that dip around 4KHz, so I took it out. Here's the result:

Graph B : Woofers in parallel, NO Bypass Cap paralleled with the tweeter series L-Pad resistor.

To me, it looks better on the mid-to-top end (anything after 12KHz is pretty hurting), staying relatively flat witin +/- 3dB.

So my lowering of the L-Pad for the mirange raised its output by 1.5dB, and my raising of the tweeter L-Pad dropped it by 2dB for a more smoother response from 112Hz-12Khz.

But what has happened to my low end response with the woofer parallelled? My new woofer crossover is a 2mH inductor and a 80uF capacitor, crossover frequency is about 400Hz using a Butterworth. I used 3.5 ohms for the nominal impedance of the parallelled woofers. Should I have used 4 ohms? Either way, it doesn't really explain what happened. I'm temped to go back to my woofers in series setup.

Any ideas?

(Update on why the bass was missing)

Okay, y'all can call me a doofus head. Last night's graph with all the bass missing was due to one thing: the Center Channel speaker was set to SMALL! That's why there was such lower output in the bass region.

Here's 2 graphs:

Graph C : Woofers are connected in series, and I took measurements for both amp sections (the HK PA5800, and my Sony DB930 receiver). The HK seems to be a little stouter and smoother. I took the opportunity to set the woofer crossover frequency at 500Hz by lowering the inductance from 8mH to 5mH. That got rid of a big dip around 400Hz on previous woofer crossovers attempts.

Graph D : Woofers are connected in parallel. Again, I'm showing you the frequency response with the 2 amp sections. The bass sort of overwhelms the midrange/tweeter due to the gain in effiency of the 2 parallelled woofers. Again, you can see that the HK can provide more juice to the speaker, almost a 3dB difference across the board compared to the Sony, which is probably only putting out enough to handle an 8ohm load, though the parallelled woofers present a 3.5-4 ohm load to the amp.

I'm not too crazy about the dip/hump/dip around 2KHz to 4KHz. Weird. I was wondering if I mess with the midrange's low pass 1st order inductor crossover (3600Hz) and extending it a little bit more, to around 4200Hz, using a 0.58mH inductor (current value is 0.68mH).

{Next update)

I have decided to dub this center channel speaker project: The Money Pit!

I got my bonus yesterday, so I have some spare cash to throw at this project. So I decided to upgrade that current tweeter because it really does have a poor response up high, so I decided to go with a Vifa D27TG45-06.

I did a few more calculations for the initial new crossover, go the component values (plus some extras to move the break frequencies around). A quick visit to the audio shop, and I have more pieces for more audio engineering fun.

(Next update)

I'm wondering is my RS SPL meter just isn't up to snuff in the 13KHz and up region. I've tried 2 different tweeters now (Philips and Vifa), and they both show the same dropoff curve for those 3 datapoints (12.9Khz, 16.25KHz, 20.48KHz)

I will do a better job of selecting on volume level and sticking to it (that's 2 on my volume dial). This past week, I admit to being a little haphazard in my volume level (it's been close to the same, but not always the same, maybe +/- 3dB).

I have this hump in the 5Khz to 10KHz region, so I'm going to modify the midrange's 1st order lowpass filter into a 2nd order lowpass filter to get more break in it at a slightly higher break frequency (1st order break was around 3500Hz, but I think I'll break the 2nd order at 4300, this should smooth out a 6dB hump in the 5KHz-10KHz range. This just means putting a 2uF cap in parallel with my inductor. I may have to change the polarity of my midrange when I do this change.

(Next update)

GregM have me this link on modding my RS SPL meter.

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.

(Last main update for now)

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:

Graph 1 : This is what my starting point is after I install my first "guess" for the tweeter crossover. As you can see, it's pretty rocky, and the high end is just too high. You can ignore the low end on this graph, I've since figured out why it was measuring so low, I had placed the CC speaker over the TV, and it was inhibiting decent results of my measurements. Placing the CC speaker on a make-shift stand around 18" tall helped the next set of graphs on the low end frequency response.

Graph 2 : Thinking that my midrange's 1st order crossover wasn't providing enough slope to kill off the hump from 5000Hz to 8000Hz, I decided to install a 2nd order low pass midrange crossover. I was able to just parallel a 2uF capacitor with my original .68mH inductor to get the new 2nd order crossover. The break frequency is 4300Hz for this crossover. Well, as you can see, that just stiffened up the hump. Please ignore the low end response for this graph as well.

Graph 3 : So, I thought maybe I needed to pad down the tweeter response, so I swapped out the L-pad resistors (-3.52dB of attenuation) for another set which gave me -8.24dB of attenuation. As you can see, it didn't really help. Notice now that my CC speaker is on the make-shift stand, its low response got a lot healthier.

Graph 4 : The next thing I did was to push the tweeter high pass break frequency out from 4650Hz to around 6800Hz with a 2nd order Bessel crossover. I was constrained by what components (L's, C's, and R's) I had on hand, and this is a low Q (~0.5) crossover, so the break is more gradual than most normal crossovers (like a Butterworth/Q~.63 or Chebychev/Q~.7) I though this to be a good thing given what I had on hand. As you can see, pushing the tweeter break frequency out to 6800Hz got rid of the hump. This means the midrange is doing a little extra work from 4000Hz to 6500Hz, but it should be able to handle it. The tweeter gets to slack off until 6000Hz or so (a guess on my part). But as you can tell, the rest of the tweeter response falls off fast, so this isn't quite desirable either.

Graph 5 : Since I needed to boost the high frequencies, I decide to de-install the L-pad resistors that gave my -8.24dB of attenuation. Then I re-install the L-pad resistors that gave me my original -3.52dB of attenuation from my initial design. As you can see, this worked out pretty well. I'm not too concerned about the low end because I'll be running this CC speaker as a SMALL speaker, so the low end output isn't a major concern.

Graph 6 : Not convinced that I need the midrange 2nd order low pass crossover, I decide to see what happens when I take out the capacitor on the midrange low pass crossover that makes it a 2nd order LP crossover with a break frequency around 4300Hz. With only the inductor in place, the LP crossover is now a 1st order with break frequency around 3500Hz. As you can see, my 5000Hz-8000Hz hump comes roaring back and creates a tumultuous and mountainous response curve once again.

Graph 7 : Knowing that I need that midrange LP 2nd order crossover to keep my frequency response smoother, I re-install the capacitor and decide that this will be my final crossover design for these speaker components.

Granted, there's some pockets of lowness in the 125Hz-500Hz range, it's something I can live with. I'm afraid that if I re-do my L-pad for the midrange anymore (or rip it out altogether - it's only providing -1.5dB of attenuation as it is anyhow), I'll screw with my high end tweeter response. The same goes with the 4000Hz range, it's a bit low, but not terribly so. I may reverse back the midrange polarity connection since I went to the 2nd order LP crossover, to see if it gives me back a little more SPLs in the midrange.

You'll notice that on graphs 4-6, there are 2 set of measurements, one is from my HK PA5800 amp, and the other is from my Sony DB930 receiver. I can't explain why the Sony's SPL output track the HK well on one graph, but then lags by 2-4dB on the other 2 graphs. It may have been things moving around since I had to lug the speaker to and from the measuring spot after each change to the crossover network. Also, the overall volume level would go up and down a few dB from different measurement sessions. I tried keeping the receiver's volume level the same, but I'm guessing there were minute variation of the actual placement and some room interaction was going on. But at least the general shape of the curves were consistent.

I'm so glad I borrowed the company cordless power drill to screw and unscrew the back panel off and on.

Next up: After that I document the crossover network for the Vifa tweeter, I'll go back to my original Philip tweeter, and see how far I need to push my tweeter's break frequency to smooth out the frequency response with the Philips tweeter in place. The fun never ends.

Think how much quicker I'd be done if I had some speaker modelling software!

PatCave; HT Pix;Gear;DIY Projects;DVDs; LDs

**JonMarsh** · 07 March 2001, 11:46 Wednesday

Pat,

Great work on your project, tons of detail and documentation! You make me look like a slacker and n'er do well, as far as documentation. Even since I've gotten the digital camera's, I sill find it hard to get out of the habit of being a little "stingy" with the "film".

Your chosen driver configuration is pretty much what I think the "ideal" is for center channel; I've got a similar speaker in the works for my system, but I've got an extra woodstyle cabinet around I'm going to brace and convert for that project.

Note, regarding your connection and response issues: when you connect the drivers in series, versus connecting them in parallel, there's a huge difference in the electrodamping on each driver, and it affects the Qtc and the whole low frequency alignment. Normally for a project like this, I would measure all the drivers in the cabinet before working on the crossover. Tyically you'll have to have some baffle step compensation in the crossover, rolling the response slightly above 250 to about 600-700, or until your crossover to the mid. The overall shelf effect will be on the order of 3 dB, but it may have to be tweaked a little, depending on cabinet size and shape. This is where the measurements in the cabinet are helpful. Obviously, changing the configuration of your LF drivers requires a whole new crossover design.

Keep up the great work, and thanks for taking the time and trouble to share with the forum members.

Regards,

Jon

Earth First!
_______________________________
We'll screw up the other planets later....

**Patrick Sun** · 07 March 2001, 15:22 Wednesday

John, thanks for the kind words. 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.

(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** · 08 March 2001, 20:57 Thursday

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** · 11 March 2001, 22:53 Sunday

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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**Patrick Sun** · 16 March 2001, 01:21 Friday

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** · 17 March 2001, 14:38 Saturday

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.

PatCave; HT Pix;Gear;DIY Projects;DVDs; LDs

**bigg** · 22 September 2009, 07:26 Tuesday

Anyone know of any source for the Vifa M18WO-09-08 woofers?

**stgdz** · 22 September 2009, 09:28 Tuesday

holy 8 year bump

**TacoD** · 22 September 2009, 13:58 Tuesday

I am impressed that all links I clicked (two) are still working

.

**seattle_ice** · 22 September 2009, 19:34 Tuesday

All the links still work even after 8 years, and I haven't seen a M18 woofer in a while. The closest I know of is the PL.

**Dave Bullet** · 22 September 2009, 21:43 Tuesday

Must be close to winning the "oldest thread dredge" guiness world record!

**Patrick Sun** · 23 September 2009, 19:42 Wednesday

Holy smokes!

The Center of the Sun - photos

The Center of the Sun - photos

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