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I made some front speakers (the SunOnes) and some rear speaker (the SunTwos) last year, and was using an older center channel speaker I built to go with my older speakers, so I decided to use the same drivers in my newer speakers in order to build a center channel speaker that was more timber-matched to the current speakers.
I continued using the woofer-(tweeter/midrange)-woofer driver configuration as my last center channel project as this is the best configuration for a speaker laying on its side for use as a center channel when space above the TV is at a premium.
I dub this center channel speaker: The SunCC.
Using the tweeter and midrange I selected, I was able to get the height of the front baffle down to 9", and I settled on 24" for the width of the front baffle, and using the entire enclosure, with the exception of a small space just for the tweeter and midrange, the midwoofers were given a cabinet with internal volume of roughly 1 ft^3, and was ported with a 2.75" wide port 5" long for an enclosure tuning frequency around 45Hz. The final box dimensions are 24"x9"x14.75".
I picked up parts for the crossover, ports, and drivers from Audio Lab of Georgia, Madisound, and Parts Express. I got the MDF, glue, and screws from Home Depot. A friend of mine, Jeff, has a nice workshop with a table saw and helped me make all the MDF panel cuts.
I brought the CC speaker to RobC's place to get some measurements in late June of 2002, and my experimental crossover just needed some minor tweaking, mainly on the tweeter filter (more padding, and more capacitance to get the tweeter to "kick in" earlier. One of these days, RobC will forward the measurement plots to me, and I'll post my original XO attempt, the tweaked XO response, and then his XO design and measurement to get some steeper slopes for the drivers to reduce the bandpass gain. Once I finalize the crossover, I'll post it in this section.
Update: I've been playing around with using 4th order acoustic slopes for the drivers to get less bandpass gain and better integration between drivers. I'll try to post some pics of the change in slopes soon.
Update 9/15/02:
After playing around with Speaker Workshop software, and listening to the effects of the changes with each filter iteration, I came up with this crossover network for the time being. Depending on the TV broadcast source, male vocal can sound a little crotchety, but on DVDs, male vocals sound okay to me. Female vocals also sound fine to me with this crossover.
So here's my latest crossover design.
I'll try to get some FR measurements at DIY 2002 - Atlanta in late October, 2002.
Here are driver measurements mounted in the front baffle, I think they were measured around 2 feet from the mic on RobC's LMS system in his garage:
The tweeter: Morel MDT-30
The midrange: Morel MDM-55
The midwoofers: Peerless HDS439 - please note the baffle step rise starting around 200Hz. Since my I targetting a crossover point around 800Hz, I knew that a filter would be able to flatten that rise and also produce enough roll-off around 800Hz so that I didn't need to add any more baffle step compensation given the relative sensitivity of the midrange (I did need to pad down the tweeter to even out of response).
Here's some shots of my initial filtered responses on the drivers:
The tweeter filter response:
The midrange filter response (not sure where the bump at 2KHz comes from, though):
The midwoofer filter response (I don't have it yet, will post it when I get it) which shows how the filter smooths out the response after 200Hz and gives me the roll-off I needed to crossover around 800Hz:
Here's the frequency response with the midrange wired out of phase with the tweeter and midwoofers - there's a bit of a hump around 2KHz:
Here's the frequency response with the midrange wired in phase with the tweeter and midwoofer - this is to see if the hump around 2KHz goes away, and it does, but introduces minor dips around 1KHz and 4KHz (near the crossover frequencies) as expected, but overall it seems to be a smoother frequency response, around +/-3dB from 50Hz-20KHz. You'll note that the F3 for the enclosure is right around 50Hz which is okay with me.
That is my current frequency response until I try out RobC's XO later.
Here's a shot of the impedance profile - the low is around 4.5 ohms, but it does vary upwards, a side effect of using textbook filter and no XO optimization software:
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Here we go:
Day 1 (6/8/02)
The raw materials:
Photo 1 : Here are the panels that my friend, Jeff, cut for me, I used a lot of scrap MDF from my previous projects.
Photo 2 : This is a shot of miscellaneous knick-knacks I needed for the enclosure and the crossover construction.
Day 2 (6/9/2002)
Photo 3 : Here a look of the MDF panel cut to my specifications by a friend of mine with a wood shop that would put Tim "The Tool Man" Taylor to shame.
Front baffle preparation/driver holes creation:
Photo 4 : To get the true diameter of the tweeter, I cut a strip of paper, and wrap it around the tweeter as shown, and then use the length of the strip to determine the circumference of the tweeter, and then use good ol' geometry to find the radius of the hole I needed to route through the front baffle. Circumference = 2 x pi x radius (solve for radius, pi = 3.14159).I needed
Photo 5 : I've already marked a center line for the front baffle, and I use that to plan my hole placement. Here I draw the shape of the square faceplate of the midrange driver on the front baffle.
Photo 6 : I use the same trick of wrapping the midrange with a strip of paper to determine its radius.
Photo 7 : This shows all of the holes that need to be routed out, plus the center pivot holes for the circle jig/router.
Photo 8 : Here's a shot of how the drivers should fit on the front baffle.
Photo 9 : The tools I used to come up with the holes to be cut and recessed.
Photo 10 : I intended on recessing the tweeter and the midrange drivers, so I did a bit of practicing on scrap to get the depth of the recess right.
Photo 11 : Using a 1/8" drill bit, I drill in the pivot holes for the circle jig for all 4 of the holes to be routed.
Photo 12 : To do the tweeter recess, I first do the actual recess, making sure I route out enough depth and wide enough for the flange.
Photo 13 : Then I use the same pivot hole to route out the actual tweeter hole. (If I did the hole first, I'd need a different router bit to do the recess later).
Photo 14 : Here's the obligatory test fit of the tweeter in its new home.
Photo 15 : Then I route out the hole for the midwoofer because I don't need a pivot hole for its square shaped recess.
Photo 16 : I do the test fit for the midrange.
Photo 17 : Using the straight side of my router, and creating a "fence" for it as shown, I am able to route out the square shaped recess for the midrange. It does take some patience to do all 4 sides, but it can be done.
Photo 18 : Here's what the 2 recessed driver holes look like.
Photo 19 : Final test fit of the midrange in its new recessed home.
Photo 20 : The holes for the woofers are then routed as well. I don't plan on recessing the midwoofers, so that was easy.
Photo 21 : A test fit of all of the drivers on the front baffle.
Photo 22 : While I had the router in use, I decided to route out a hole for the port on the rear panel.
Photo 23 : Test for fit of the port hole.
Photo 24 : I use my portable drill press contraption to pop in the screw holes for the drivers.
Photo 25 : All of the screw holes have been made.
Photo 26 : Test for fit, with the screws in the driver screw holes.
Photo 27 : I use t-nuts to hold in the screws, this requires making the holes on the inside of the baffle a bit larger for the t-nut to fit.
Photo 28 : I put glue in stratetic places in between the t-nut and the baffle surface and pound them in. Normally I use 1/4" plywood, but I decided that the glue would be sufficient to keep the t-nuts in place for these drivers.
Photo 29 : All of the t-nuts have been pounded into place, and have glue all around their perimeters.
Enclosure assembly:
Photo 30 : The edges of the side panels are glued into place.
Photo 31 : Then I use clamps and panels to apply pressure in the needed spots for the side panels to be glued to the bottom panel.
Photo 32 : While glue is drying, I pop in the holes for speaker wire to be fed to the drivers in the backwall of the tweeter/midrange compartment which will come together soon enough. I lost count and drilled in 2 extra holes that weren't needed. I taped up those extra holes later.
Photo 33 : I am marking off the necessary piece that needs to be cut from the internal panels. The internal panels are used to create the compartment, and provide bracing for the enclosure, and I'll be creating a rear panel that can be screwed/unscrewed for access to the crossover in the future.
Photo 34 : As the internal panels are put into place, I mark their placement so I know where to apply some glue very soon. See how the compartment for the tweeter/midrange is shaping up?
Photo 35 : I continue to draw lines for the internal panel placement.
Photo 36 : I mark where I'll be routing out holes in the internal panels.
Photo 37 : Once the holes were marked, I used the router, and just free-hand routed out the rectangular pieces to allow air flow inside the enclosure.
Photo 38 : Glue is now applied to the bottom panel.
Photo 39 : The internal panels are placed in to-be-glued positions.
Photo 40 : More glue is applied to the tops of the internal panels, and the side panels. I'm about to glue the top panel to them.
Photo 41 : The top panel is clamped so that the internal and side panels are glues up in their proper positions.
Photo 42 : After the glue has dried, it's time to glue the front panel to rest of the enclosure.
Photo 43 : More clamping so that front panel is glued to the enclosure.
Day 3 (6/10/2002)
Back Panel installation:
Photo 44 : To smooth the panel joints, I use my orbital sander to sand away the excess glue from the seams, and sand smooth the joint transitions from panel to panel.
Photo 45 : I mark the thickness of the rear panel as a guide as I make the bracing fit inside the enclosure.
Photo 46 : Glue is applied to the bracing 2x2's.
Photo 47 : The side braces are glued into place.
Photo 48 : To make the long rear panel bracing pieces to fit, I needed to use some cardboard to shim them tighter. Glue is applied to one of the rear panel bracing pieces.
Photo 49 : And the other piece of glued into place.
Photo 50 : Here's a shot of the rear panel bracing glued into place.
Photo 51 : To make sure it's a tight fit, I clamp the rear panel in place as the glue dries.
Photo 52 : The rear panel was cut so that it would have just a bit of play in either direction, thus the pieces of cardboard used as space holders.
Photo 53 : I pop in more screw holes for the rear panel.
Photo 54 : I needed to continue the screw holes into the rear panel bracing piece because my drill bit didn't go that deep.
Photo 55 : This is my way of creating countersinking holes for the screws: I get a big drill bit, and reverse the drill and press into the screw hole, enough material is gouged out to countersink the screws.
Photo 56 : I caulk the interior from the rear side.
Photo 57 : I caulk the interior from the front side to get all of the seams.
Photo 58 : Wood screws are drilled into the screw holes for the rear panel.
Photo 59 : Weatherstripping is installed around the bracing piece perimeter.
Photo 60 : Finally the rear panel in screwed in, extra pressure is needed to compress the weatherstripping.
Photo 61 : To help in compressing the weatherstripping, a bag of sand is placed on the rear panel.
Driver installation:
Photo 62 : The enclosure is now ready to have the drivers installed.
Photo 63 : I crimp some female spade connectors on the wires for the tweeter and midrange.
Photo 64 : This shows how the wires are fed through the holes in the compartment for the tweeter and midrange (the extra holes were taped up later).
Photo 65 : This shows how the midwoofers will be hooked while inside the enclosure for a parallel type of connection. The drivers have dual spades to make this an easy possibility.
Photo 66 : The drivers are now screwed into the enclosure - front view.
Photo 67 : The center channel speakers is taking shape - the corner view showing its depth.
Day 4 (6/13/2002)
The crossover:
Photo 68 : Temporarily the wires from the crossover are being fed through the port hole.
Photo 69 : Here's a show of the speaker with the crossover outside the enclosure for easier tweaking.
Photo 70 : A close-up look at the crossover, one panel will reside in its own side behind each midwoofer.
Day 5 (6/20/2002)
Photo 71 : After getting the enclosure made, I was able to schedule some time with my friend, Jeff, and his big 1/4" Porter router and table so that I could apply a 3/4" roundover on all sides of the front baffle.
Photo 72 : Here's one last look at the enclosure with the 3/4" roundover.
That's it for now.
I finally put a finish on the speakers:
Here's a webpage that details the process to get this look for the speakers.
 My home theater web page was a featured home theater for October 1999! |
Thanks for stopping by! Now go watch some DVDs and listen to some music!