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I decided that after the fun I had with my DIY center channel speaker project, I thought it'd be more fun to design a pair of speakers from scratch. I've been down the 3-way road with my college speaker project, and decided it'd be fun to try a 2.5-way speaker. The general idea behind using a 2.5-way design is to use a tweeter, and 2 midwoofers. I went with a TMM design, where the tweeter is situated on top, and then 2 midwoofers underneath (the photo up above shows what I'm describing). The upper midwoofer is used for handle the bass/midrange up to the crossover frequency with the tweeter, and it runs all the way through its frequency response. The lower midwoofer is used to defeat the baffle step loss that occurs when bass from a speaker radiates all around, in 4pi speace, and it runs between its low end response to somewhere around 500Hz, which is where the baffle step loss starts to dissapate as the rest of the frequency spectrum becomes more directional and radiates in 2pi space - in front of its baffle (front panel). Thus this design is called a 2.5-way design. Conventional TM speakers require the tweeter's output to be shelved down so that the baffle step loss is minimized, but this means the overall speaker efficiency drops by 3dB to 6dB depending on where the speakers are placed in a room. This means adding in some baffle step compensation in the crossover network. Click here for more details on the baffle step diffraction loss and compensation.
I wanted to say "Thanks" to the following folks for all the help and guidance they gave through the process. All were extremely patient with my questions and pushed me to get me to this point.
I decided I wanted a maximum height of 24" for the speakers. This I decided on 10" for the width of the front baffle. This would allow me to use the Peerless HDS439's and apply a 3/4" roundover without much hassle. The depth of the enclosure was totally dependent on the needs for the internal volume for the 2 midwoofers. As it turns out, the depth of the enclosure was 14.25". This was due to tuning the enclosure to around 50Hz with a 2.75" wide port 5" long for internal volume around 1.1 ft^3 because that's what was required by the Peerless HDS439 drivers.
The final box dimensions are 24"x10"x14.25".
You'll notice that my front baffle has the drivers located off the vertical center line. This was determined by using Paul V's Baffle Diffraction Simulation spreadsheet. After playing around with driver placement scenario, I decided on the one I used since it gave me the best results (minimal diffraction reflections for the tweeter). I wound up with the following offsets:
I picked up parts for the crossover, ports, and drivers from both Audio Lab of Georgia, Madisound, and Zalytron. 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 ordered a 3/4" roundover bit, and Jeff was nice enough to let me use his big ol' Porter router that accepts 1/2" shank size. The front baffle has been rounded over on all 4 edges with the 3/4" roundover bit to help with baffle diffraction. Paul V's spreadsheet led me to do the roundover on the front baffle.
Here's the frequency response of the tweeter measured on a LAud setup on the front baffle:
Here's the impedance/phase response of the tweeter measured on a LAud setup o the front baffle:
Here's the frequency response of the midwoofer measured on a LAud setup on the front baffle:
Here's the impedance/phase response of the midwoofer measured on a LAud setup o the front baffle:
Though I have a big subwoofer which I can use to fill in the low end, I still wanted these speakers to play nice and tight bass. With the enclosure tuned to around 50Hz, my F3 was also near there. For 1 meter SPL measurements, that was the case, but with 3 meter SPL measurements, the room gain lowered the F3 to around 40Hz, more than acceptable for speakers of this size. I was pretty surprised by the amount of bass from these speakers.
Initially, to test the overall frequency response of these speakers, I took on-axis measurements from 1m away. I didn't have fancy measurement software and microphones yet. Please bear in mind that I was using a BassZone Test CD from Stryke and a digital Radio Shack SPL meter, which doesn't measure too well above 10KHz, so I ignored SPL readings over 10KHz for now.
This was my current overall response for the speakers (as of 7/22/01 last year):
3 meter frequency response graph
But this was a pretty inexact way of doing things, and in 2001 I bored people to tears with my incremental changes and repeated manual measurements of their effects on the speaker's frequency response. So I'm scrapping all of those graphs, and will be showing up what a good measurement system (LMS) and crossover optimization program can do to speed up the crossover design process.
I met RobC at the 2001 Atlanta DIY speaker meet in the fall, and found out that we lived close by each other. RobC was nice enough to help me out with a revamp of my crossover design. Rob had the LMS measurement system and the LEAP crossover optimization software.
In December, 2001, I stopped by with my speakers, and he took some measurements of the drivers while installed in the speaker baffles, and used the measurements to come up with a preliminary crossover design. Rob noticed a problematic resonance peak at the knee of the break frequency for the tweeter with my other tweeter filter, so he revamped the crossover for me. I built it, and listened to it for a few months.
Our schedules never quite meshed until late March of 2002, but I finally brought my speakers back for re-evaluating with the new crossover design in place. I had thought the tweeter was bit too loud, and needed some padding. After listening to the speakers, and then measuring them, my ears proved me correct. Here is one of the graphs showing a pronounced upswing in the tweeter output:
Graph 1 : As you can see I needed around 3dB of padding on the tweeter. We took all of the measurements in his garage. At this particular position, the F3 for the bass shows up to be around 50Hz. Later, next month, the bass response looks worse, but it was because we measured it from a different spot in his garage. The hump from 100Hz to 150Hz is a bit of a room mode in his garage.
A week later, after I make some tweeter padding changes, I take the speakers back to be re-measured at Rob's place.
Graph 2 : Here's a graph of the 2 main crossover region from the combined midwoofer output, and the tweeter output. These graphs are pretty bumpy since they are 1/10 octaved smoothed. Most graphs you see are 1/3 octave smoothed, and smooth they are. I've increased the tweeter padding from -1.5dB to -4.5dB to get the levels in line with the midwoofer output. It appears to be the right amount of padding.
Here is the graph of the frequency response of the final crossover design. It's pretty close
to +/- 2.5dB from 50Hz to 20KHz. The bass response is closer to how it looks like Graph 1.
So that was that in terms of the crossover design/implementation/listening/tweaking process when using some spiffy measurement gear and crossover design software, which definitely speeds up the process.
From that initial design, I made plenty of trial-and error changes to the crossover, but it was just about futile until I got some help from RobC who offered to help nail down a crossover for my speaker project. I'll be forever grateful for the interest he took in this speaker project, and my other 2-way speaker project. This is what Rob came up with using his LEAP software:
This is the final crossover, it's displayed below (last updated 5/20/02):
Hint: For faster navigation, when you click on your first picture link, don't close that 2nd window, but resize this window and position it so you can see both windows concurrently. I've designed it so that you can leave that 2nd (photo) window open, and you can click to your heart's content in this first window, and the images will only show up in that 2nd other window. This should also speed up your visit here. If you want separate windows, then right click of the photo links and select the "open in new window" option.
Here we go:
Day 1 (Saturday 4/28/01)
The raw materials - wood panels:
Photo 1 : Here are the pieces of MDF and plywood stuffed in the back seat of my car.
Photo 2 : At my friend's place, I've lines up all the wood, most of it MDF, with a 2'x2' sheet of plywood and some 2"x2" wood bracing.
Photo 3 : This is my buddy Jeff, who's helping me with cutting up the wood. He sort of looks like a MDF-dust-breathing alien in this shot...
Photo 4 : After lots of sawing and MDF dust, I've got all my wood cut to specifications that I drew up. This will allow to make 2 speakers.
Photo 5 : I test for fit of the panels, roughly, and this give me an idea of how things will be put together.
Photo 6 : I will be using the plywood on the inside of the front baffle so that I can install t-nuts which will allow me to screw in screws without worrying about conventional nuts on the inside. I draw a perimeter around around the plywood before I glue it on, after I've made sure the other panels have enough room (3/4" of clearance on all sides).
Photo 7 : I proceed to squirt the glue on the back of the front panel.
Photo 8 : The plywood is glued in place.
Photo 9 : It doesn't look like it, but I'd got that front panel and the plywood underneath that stack of MDF, and this will apply the weight for a strong glue bond.
Day 2 (Monday 4/30/01)
Photo 10 : Here's a shot of all the miscellaneous parts: screws, t-nuts, paint, primer, glue, weatherstripping, crossover knick-knacks/connectors/etc.
Photo 11 : I draw a center line, and then off that line, I draw in lines for the offset for the tweeter and the midwoofers. The tweeter is 0.75" off the center line, and the midwoofers are 0.5" off the center line.
Photo 12 : I drill in the pilot holes for the centers for the driver cut-out routing. I'll use the circle jig with a router for this operation.
Photo 13 : I knew I'd be installing horizontal bracing inside the box to "wall" off each driver. This shows where the braces should be installed as I use the drivers to block off the sections.
Photo 14 : Here I start routing the recesses of the tweeter. You need to measure the required thickness/depth of the tweeter for the routing, and then do a bit of testing before you start on the front baffle itself.
Photo 15 : Here's both tweeter recesses. I confess to making the first one too wide.
Photo 16 : I cut in the hole for the tweeter and its connector leads.
Photo 17 : I test for fit of the tweeter driver. See, it's just a tad too wide. Doh!
Photo 18 : I finish up the other tweeter hole.
That's it for tonight, it's getting too dark for anymore cutting.
Day 3 (Tuesday 5/1/01)
Photo 19 : It's time to start on the holes for the midwoofers. Here I mark off the circles with a compass and measure off and draw in the lines where the tops and bottoms of the midwoofers are truncated. These drivers will also be recessed into the front baffle.
Photo 20 : I route in the tops and bottoms based on the lines I drew on the front baffle. I use the straight edge of my router and clamp a board with a nice straight edge to keep the cut nice and straight. I also make sure the cutting depth is the correct depth to flush mount the midwoofers.
Photo 21 : I finish up all 4 straight lines.
Photo 22 : I then use my circle jig to route out the rest of the circular perimeter for the midwoofers. The inner circles drawn are for the actual hole for the drivers.
Photo 23 : Carefully moving the radius of the circle jig towards the center, I route out the rest of the recessed flange for the drivers. The remaining circle will be the hole for the driver.
Day 4 (Wednesday 5/2/01)
Photo 24 : I finish cutting out the hole for the first midwoofer.
Photo 25 : Test for fit of the midwoofer hole. Looks pretty flush.
Photo 26 : I march on and do the other midwoofer hole for this front baffle.
Photo 27 : Here's the first midwooder hole for the 2nd baffle.
Photo 28 : Here's the 2nd midwoofer hole for the 2nd baffle.
Day 5 (Thursday 5/3/01)
Photo 30 : I sand the recesses as smooth as possible for now.
Photo 29 : Now it's time to work on the horizontal bracing. I draw in circles because the bracing won't wall in the 2 midwoofer chambers, and will allow airflow. I did make a mistake in the circle placement, but it doesn't affect my vertical bracing too much later on.
Photo 31 : I drill in the center pivot holes for the circle jig.
Photo 32 : And the routing fun starts anew. I just go nuts and route out the holes.
Photo 33 : Now I finished with all the holes in these braces (one for each cabinet).
Photo 34 : This is me marking off the horizontal bracing between the tweeter and the upper midwoofer. I plan on using that small panel to totally enclose the tweeter from the rest of the cabinet. You can see the center holes that I've marked off for the big hole that I will route out of this piece of bracing.
Photo 35 : I drill the pivot holes for this bracing.
Photo 36 : After more routing with the circle jig, I cut out the holes for the bracing.
Photo 37 : Next up is the rear panel. I mark off the holes for the terminal cup and the port.
Photo 38 : These are the holes I need to make on the rear panel.
Photo 39 : I drill in the pivot hole for the circle jig.
Photo 40 : Now the port hole has been cut out.
Photo 41 : I test for fit of the hole cut for the port.
Photo 42 : Since the hole for the terminal cup doesn't have to be super-straight, I free-hand the routing for the rectangular hole needed.
Photo 43 : Here's the cut-out for the terminal cup.
Photo 44 : Here's the test for fit of the terminal cup.
Photo 45 : Here's the other rear panel that has the holes cut for the port and terminal cup.
Photo 46 : More testing for fit.
Day 6 (Friday 5/4/01)
Photo 47 : Back to the horizontal bracing - I'll be incorporating 2"x2" wood strips as the vertical brace which will allow me to screw in the rear panel into these wood strips. Here is where I mark off the corners that I need to cut out of the horizontal bracing. As you can see I forgot to allow for the wood strips, so the holes will be cut into for the strips to fit.
Photo 48 : I do the same for the other horizontal bracing, and I did remember, so I won't be cutting into the hole.
Photo 49 : Here's the cut lines.
Photo 50 : I cut out the corner with my router (free-hand).
Photo 51 : I check for fit of the 2"x2"s and the bracing.
Photo 52 : I cut all the bracing and test for fit.
Photo 53 : Here I start drilling holes for the screws for the terminal cup.
Photo 54 : All the screws are tested for fit.
Photo 55 : The other rear panel has the screws drilled and tested for fit.
Photo 56 : Here I start drilling of the screw holes for drivers.
Photo 57 : Test the fit for the screw holes of the midwoofer in its recessed hole on the front baffle.
Photo 58 : I finish drilling in the screw holes for both midwoofers.
Photo 59 : I start on the other front baffle with the driver screw holes.
Photo 60 : I finish up the screw holes for the 2nd front baffle.
Photo 61 : I start lining up the tweeter driver holes, using the ruler and the bottom tweeter holes.
Photo 62 : More drilling and I have my screw holes for the tweeter.
Photo 63 : Now it's time to install the t-nuts. I start by drilling a slightly larger hole on the backside so the t-nut can fit into the hole, and then I apply some glue for additional holding power.
Photo 64 : Once I pop in the t-nuts, I hammer them into the plywood. This is why the plywood layer is used. MDF doesn't provide enough strength to hold the spikes of the t-nuts in place.
Photo 65 : Just for overkill, I put ever more glue over the t-nuts once they are hammered into the plywood.
Photo 66 : Here's a bit of my inexperience showing. I made the hole for my 1st tweeter hole too large, so one of my screw holes are too close to the edge, so I routed out from scrap a piece of MDF which was glued to the edge. This provides just an extra bit of stability (I hope).
Photo 67 : Here's the backside look at the repair attempt with the t-nut in place.
Photo 68 : A few more whacks with a hammer and the t-nuts are installed for the tweeter on the other front baffle.
Photo 69 : Next the midwoofer holes on the inside are widen up a tad for the t-nuts for one front baffle.
Photo 70 : Bam! Bam! Bam! More t-nuts are hammered into place.
Photo 71 : More glue is applied to the t-nuts.
Photo 72 : This is the other front baffle after the holes have been enlarged a tad, and the glue is applied to the outside of the holes.
Photo 73 : Some more t-nuts are hammered into the plywood.
Photo 74 : After hammering the t-nuts into the plywood, more glue is applied to them.
As you can see, it's getting dark again, so that's it for now.
Day 7 (Tuesday 5/8/01)
Today is the day to finally start glueing up the panels into a box.
Photo 75 : Here's a shot of how the internal bracing will look/fit inside the box.
Photo 76 : I use the front baffle to draw the lines I will need to line up the horizontal bracing inside the box.
Photo 77 : This is the back plate for the tweeter enclosure. I've drilled a hole for the driver wire, and have outlines the corners that I will need to cut for the 2"x2" wood strip/bracing to fit through.
Photo 78 : Here are both back panels with the corners cut out of them.
Photo 79 : I start to glue the tweeter back panel to the horizontal bracing between the tweeter and upper midwoofer.
Photo 80 : Here's a shot of both braces glued up.
Photo 81 : I test for fit of the bracing.
Photo 82 : I start the glueing process with applying glue on one side panel.
Photo 83 : This is the other side panel. I need to do both of them at the same time so I can swiftly fit the panels together before the glue dries.
Photo 84 : For the 1st side panel, I glue the bracing to it. This gets a little nerve-wracking because if you screw this up, it's back to Home Depot for more MDF.
Photo 85 : Then I place the other side panel in place, and rush to get the clamps on the panels. This step would be easier if you had another pair of hands to help out. You have to smooth out the edge placement for all joints to insure the panels will glue together in the correct position/alignment. Remember to measure the diagonals and make sure they are the same, this means the joints are nice and perpendicular.
I allow this to dry overnight.
Day 8 (Thursday 5/10/01)
Photo 86 : As you can see in the background, the 1st box has been glued and dried. I then start on the 2nd box. I do things a little differently after a night's sleep. I pencil in the bracing position on the side panels.
Photo 87 : After pencilling the bracing position on the side panel, I apply glue where it's needed.
Photo 88 : Here's the 2nd side panel all glued up.
Photo 89 : Another look at the panels being glued together before the other side panel is glued into place.
Photo 90 : I quickly get the panels into place and clamped tight. I give the entire next day for the glue to dry after I make sure all the joints are smooth and perpendicular.
Photo 91 : Now it's time to do some caulking of the enclosure.
Photo 92 : If you're observant, you'll noticed that 2 real days have passed. Yesterday I went to my buddy's place to use his router table and his big router that handles 1/2" shank size bits (mine only does 1/4" shank size bits). Once we ran some test MDF pieces to set the cutting depth and the fence, it was pretty easy to run the edges of the front baffles through the 3/4" radius roundover bit on the router table in a nice straight line. Here's a close-up shot of the newly rounded over front baffles.
Photo 93 : Then I apply glue on the front edge of the enclosure. This will be where the front baffle is glued onto the rest of the enclosure.
Photo 94 : Finally I place the front baffle into place, the glue oozes out (is wiped up soon enough).
Photo 95 : I wipe off the excess glue with a moist towel.
Photo 96 : To make sure the front baffle is glued on tight, I plop a piece of MDF scrap and a bag of sand on top of it.
Day 9 (Friday 5/11/01)
Photo 97 : I take the opportunity to caulk the inner seams of the 4 panels now that they are glued together.
Photo 98 : I use my orbital sander to smooth the outer seams.
Photo 99 : Now it's time to glue the front baffle to the 2nd enclosure. I apply the glue to the edges.
Photo 100 : Once I position the front baffle where I want it, I've wiped up the glue that's oozed out of the seams. I apply pressure to ensure the baffle stays glued where I want it glued.
Photo 101 : Next is the scrap MDF and bag of sand to keep the pressure on the front baffle as the glue dries.
Photo 102 : I then caulk the other inner seams that meet the front baffle with the rest of the 1st enclosure.
Photo 103 : Now it's time to install the the 2"x2" bracing along the inside perimeter of the enclosure. I start with some blocks that run horizontal in the corners. I use a combination of glue and caulk.
Photo 104 : Here's another view of the bracing being glued into place.
Photo 105 : The vertical rear brace (used to provide the rear panel screws to screw into) is now being prepped to be put into place. I have a bit of a gap that I need to deal with on the corner braces, so I use caulk to build up a bit of thickness.
Photo 106 : I put the vertical rear brace into its slot with plenty of glue on the right surfaces.
Photo 107 : This is the upper horizontal braces that will be slotted into the tweeter compartment, again plenty of glue is used.
Photo 108 : The bracing is now in place, the gap will be covered with caulk.
Photo 109 : The other vertical rear bracing is prepped for placement. Note the abundance of caulk on the horizontal bracing.
Photo 110 : And now that rear bracing has been glued into place. Once the caulk dries, it should provide enough gap coverage for the bracing to stay in place.
Photo 111 : Now it's time to make sure the rear panel will fit, and it does.
Photo 112 : To provide some more bracing wood so I can screw in screws down the vertical center line, I put in some more horizontal bracing, and then an upper vertical brace.
Photo 113 : Once the horizontal brace is glued in place, I can then glue in the upper vertical brace.
Photo 114 : The center line horizontal bottom brace needs to be long enough to run the length of the depth of the enclosure minus a little bit. I use some scrap MDF for this piece of bracing.
Photo 115 : Then the other bottom brace is glued into place too.
Photo 116 : I test for rear panel fit once more with all the bracing pieces in place.
Day 10 (Saturday 5/12/01)
Photo 117 : A glimpse of things to come, the enclosure is coming along quite nicely.
Photo 118 : On to the 2nd enclosure and its bracing. You can skip the next 8 photos if you'd like.
Photo 119 : More caulking of the front baffle seams.
Photo 120 : Again I glue in the horizontal bracings into the corners.
Photo 121 : This shows the upper horizontal bracing being glued into place.
Photo 122 : Remember that I had a bit of problem with the bracing blocks being a bit too short? I used some piece of cardboard as shims to raise the height to the correct height, so I don't need to caulk heavily anymore.
Photo 123 : Here's the vertical rear brace getting all glued up.
Photo 124 : Here's the other vertical rear brace getting the glue treatment.
Photo 125 : After gluing in the center braces on the top and bottom, I get ready to glue in the center braces.
Photo 126 : Now all the bracing blocks have been glued into place for the 2nd enclosure.
Photo 127 : I test for fit of the rear panel on the 2nd enclosure.
Photo 128 : To provide a seal for the rear panel once I screw it in, I will be adding a layer of highly compressible 3/4" wide weatherstripping around the bracing perimeter.
Photo 129 : Here's a shot of all the weatherstripping (has an adhesive back which makes sticking it to the bracing very easy).
Photo 130 : I put the rear panel on and then the MDF panel and a bag of sand to compress the weatherstripping as much as possible before I screw in the wood screws.
Photo 131 : I do the weatherstripping for the 2nd enclosure.
Photo 132 : Holes for the wood screws through the rear panel need to be drilled. I start with a drill bit that's as thick as the screws inner diameter.
Photo 133 : Here's a few screws that will be screwed into place soon enough.
Day 11 (Sunday 5/13/01)
Photo 134 : Now all of the screw holes have been drilled and the screws are screwed into the rear panel. I did forget about the center screws on the top and bottom. Oops.
Photo 135 : On the 2nd enclosure, it gets the sand bag treatment to compress the weatherstripping.
Photo 136 : I start drilling more screw holes into the 2nd enclosure.
Photo 137 : To countersink the hole, I use a wide drill bit, and run it in reverse, this scrapes off just enough to countersink the wood screw into the rear panel.
Photo 138 : Finally it's time to install the drivers and the crossover network. My cat, Fred, is happy to see the new speaker enclosure.
Photo 139 : With all that bracing, I go ahead and caulk the new seams.
Photo 140 : I screw in the terminal cup to the rear panel.
Photo 141 : I pop in the port (but I don't completely put in flush with the rear panel because I'm waiting until I've painted the rear panel.
Photo 142 : Here's a shot of both crossover networks (this is the original design, and it has since undergone quite a few changes since this shot).
Photo 143 : A close-up of my rag-tag crossover implementation.
Photo 144 : I put the crossover into the enclosure. I have to tilt the board to get it in.
Photo 145 : I start crimping connectors for the driver connections.
Photo 146 : The tweeter is now connected to the crossover network.
Photo 147 : This is the connector for the upper midrange.
Photo 148 : The upper midwoofer is now connected to the crossover network.
Photo 149 : I screw in the drivers, be careful, and don't let the screwdriver slip and puncture a hole in the driver cone.
Photo 150 : This is the connector for the lower midwoofer.
Photo 151 : The reason the enclosure is now on its backside is because I had a couple of t-nuts that weren't entirely perpendicular, so I had to wide the screw hole, and in this position it was easier to screw in the driver.
Photo 152 : As you can see my cat, Pooh, is excited to see all the drivers screwed into the front baffle and now the speaker is starting to look like a real speaker.
Photo 153 : Pooh is so impressed, he's standing guard over the new speaker.
Photo 154 : I screw in the rear panel with the wood screws.
Photo 155 : I start on the 2nd enclosure by screwing in the terminal cup and popping in the port into the rear panel.
Photo 156 : Again, the crossover network is put into place, and the driver connectors are now in place.
Photo 157 : The tweeter is connected and screwed into the baffle.
Photo 158 : The upper midwoofer is connected and screwed into the baffle. Fred is really cheering me on at this point in time.
Photo 159 : The lower midwoofer is connected to the crossover network.
Photo 160 : The lower midwoofer is screwed into the baffle.
Photo 161 : Here's a shot of the 2nd speaker with all its drivers in place.
Photo 162 : Now it's time to screw in the rear panel to the rest of the enclosure.
Photo 163 : With the help of a power screwdriver, the wood screws are screwed into rear panel.
Yay! I'm preliminarily done! Once I finalize the crossover, I'll be veneering the sides, and painting the front baffle, and rear panel in the near future.
Here's a shot of the speakers set up temporily in my home theater.
Update 6/28/01 While not a super DIY disaster, I had to re-locate the port hole on the rear panel of my SunOne speakers. I had a massive brain-fart and put the port directly behind one of the drivers, and that's a big No-No!
So, here are the pix for the relocation of the port hole on the rear panel of the SunOnes:
Photo 164 : I use the original port hole to trace out the diameter I will need for the replacement MDF plugs.
Photo 165 : Here's one of the plugs routed out by my trusty router and circle jig.
Photo 166 : This is the test fit of the MDF plug into the original port hole. Pretty darn close fit!
Photo 167 : After careful measuring of where the port hole needed to be in relation to the compartment behind tweeter, I draw the required hole needed for the new port location on the rear panel, and drill in the require pivot hole for the circle jig. This is very important to get right.
Photo 168 : This is the plywood panel I'll be using to seal out the hole, and the glued areas for it. This will insure no airleaks through the old port hole.
Photo 169 : Just a bit of weight placed on the glued plywood to cover up the hole while the glue dries.
Photo 170 : More glue in the old port hole is applied now that the plywood's glue is dry.
Photo 171 : The MDF plug is now glued in place.
Photo 172 : To fill in the minor gaps between the plugs and the rest of the rear panel, I slap on some wood filler.
Photo 173 : Once the wood filler dries, I use the orbital power sander to smooth out the surface.
Photo 174 : After some power sanding, you can barely feel any difference in the surface where the plugs mate with the panel. It's now pretty smooth. Once I put on a few coats of primer and sand it, I doubt anyone would ever be able to tell there was a hole there in the first place.
Photo 175 : Here's a shot of the inside part of the rear panel with the glued plywood panels in place.
Photo 176 : I test out the fit for the ports in the new holes in this shot.
Photo 177 : My cats inspect my handywork. My careful placement of that new port hole pays off as the rear panels now fits perfectly on the backside of the speakers.
I finally put a finish on the speakers:
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