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Hi all! I thought some of you might enjoy a look at my latest creation, a monster surround back speaker, combining left and right into one enclosure. I don't have an official name for this beast yet. Before I go into the gory pictures, I'll give a brief summation of the design choices made.
As usual, cost was a major concern, as was the desire to make use of numerous components already on hand. These included woofers, tweeters (same as in my other five speakers), and crossover components - essentially everything but the wood and miscellaneous hardware. So, any design had to make the most of these parts. Unfortunately, the woofers have a rather high Qts, requiring a rather large box, and I'm using two woofers per side to match the high efficiency tweeter, making the box even larger. These were surplus woofers that I got from MCM electronics about 11 years ago - the original drivers from my Emerald Towers. They're a very nice cast frame poly cone rubber surround, with a quite smooth response. The tweeters are the shielded soft dome 1" units from ApexJr, which are very nice, especially at only $15 a pair! Crossover components are a mish-mash of all high quality stuff collected from past projects. I chose a vented box despite the high Qts, because I had previously used these same woofers in a similar sized vented box with good results. And, I always like more power handling, lower distortion, and significantly higher maximum output.
This speaker is probably serious overkill for surround back duty, but I didn't have any tiny woofers on hand to use. The box alone weighs 38 pounds, and when all the drivers and crossovers are added, it's pushing 60. :yikes: And yes, it is being hung on the wall. It's a good thing my wife is strong. In hindsight, two separate boxes would have been a lot easier to maneuver, but oh well. :duh: I don't want to think about how heavy this would have been if I had used MDF instead of plywood! :hide:
Here's the basic shell including the back, top, bottom, and center divider. The bottom is the shortest side:
Test fitting of the baffle and sides just to make it feel more like a speaker:
Here are the end caps, made from pine stair treads 1" thick. On the back side, you can see the bolts which I've secured to wooden discs screwed and glued to the caps. I screwed up my first cut, resulting in one cap being about an inch too short. I had to cut a matching piece and glue it on later. :doh:
Here are my two vent assemblies. Each side has two 1.5" vents. 2" didn't quite seem like enough, but 3" would have needed an elbow and seemed like serious overkill, given that my tower speakers use a single 3" with almost twice the total displacement, run full range, and don't have any vent noise. These will be filtered at 40Hz or 60Hz depending upon my findings. The tubes are epoxied to the solid oak trim rings:
Winter came early to Washington, but that doesn't stop a true speaker builder! Here's the baffle showing placement of the vent assemblies:
Side panels screwed and glued into place, glue blocks added to front side, binding posts and wiring to crossovers installed. Note the holes in the side panels, which match up to the discs on the end caps:
Here are the crossovers. This is a third order electrical on the tweeter, first order electrical on the woofer. Approximate crossover point is 2800Hz, about as low as I comfortably felt going with this tweeter, and the same as my other five speakers:
Here's the baffle attached. It's held by a full tube of construction adhesive on all the glue blocks and around the entire perimeter of the panel, as well as screws into all the glue blocks running from the bottom to top panels. It's solid!
Here are the end caps with a whole bunch of wood filler to smooth them out and fill the gaps. Yes, the speaker isn't pretty underneath, but it doesn't matter, as the entire box will be covered with fabric and the end caps. It just has to be solid and leak free, which it is.
Here's a shot of the crossovers peeking in through the holes in the side panels:
Here's how the end caps are held on. Two 1/4" thick custom wood washers fit over the nut and bolt on the end cap, which are then secured with a fender washer and wing nut. This was done because I wanted no visible fasteners on the end caps, and I also wanted to be able to remove them easily for refinishing or replacement.
That's it for now! You'll have to wait until tomorrow to see pictures of everything fully assembled. It's in the car now so that I can take it to work for testing tomorrow, and I'm not hauling it out at 1:00 AM for pictures. Although I can lift 60 pounds, it's a very awkward load to carry very far.
As usual, cost was a major concern, as was the desire to make use of numerous components already on hand. These included woofers, tweeters (same as in my other five speakers), and crossover components - essentially everything but the wood and miscellaneous hardware. So, any design had to make the most of these parts. Unfortunately, the woofers have a rather high Qts, requiring a rather large box, and I'm using two woofers per side to match the high efficiency tweeter, making the box even larger. These were surplus woofers that I got from MCM electronics about 11 years ago - the original drivers from my Emerald Towers. They're a very nice cast frame poly cone rubber surround, with a quite smooth response. The tweeters are the shielded soft dome 1" units from ApexJr, which are very nice, especially at only $15 a pair! Crossover components are a mish-mash of all high quality stuff collected from past projects. I chose a vented box despite the high Qts, because I had previously used these same woofers in a similar sized vented box with good results. And, I always like more power handling, lower distortion, and significantly higher maximum output.
This speaker is probably serious overkill for surround back duty, but I didn't have any tiny woofers on hand to use. The box alone weighs 38 pounds, and when all the drivers and crossovers are added, it's pushing 60. :yikes: And yes, it is being hung on the wall. It's a good thing my wife is strong. In hindsight, two separate boxes would have been a lot easier to maneuver, but oh well. :duh: I don't want to think about how heavy this would have been if I had used MDF instead of plywood! :hide:
Here's the basic shell including the back, top, bottom, and center divider. The bottom is the shortest side:

Test fitting of the baffle and sides just to make it feel more like a speaker:

Here are the end caps, made from pine stair treads 1" thick. On the back side, you can see the bolts which I've secured to wooden discs screwed and glued to the caps. I screwed up my first cut, resulting in one cap being about an inch too short. I had to cut a matching piece and glue it on later. :doh:



Here are my two vent assemblies. Each side has two 1.5" vents. 2" didn't quite seem like enough, but 3" would have needed an elbow and seemed like serious overkill, given that my tower speakers use a single 3" with almost twice the total displacement, run full range, and don't have any vent noise. These will be filtered at 40Hz or 60Hz depending upon my findings. The tubes are epoxied to the solid oak trim rings:


Winter came early to Washington, but that doesn't stop a true speaker builder! Here's the baffle showing placement of the vent assemblies:

Side panels screwed and glued into place, glue blocks added to front side, binding posts and wiring to crossovers installed. Note the holes in the side panels, which match up to the discs on the end caps:






Here are the crossovers. This is a third order electrical on the tweeter, first order electrical on the woofer. Approximate crossover point is 2800Hz, about as low as I comfortably felt going with this tweeter, and the same as my other five speakers:





Here's the baffle attached. It's held by a full tube of construction adhesive on all the glue blocks and around the entire perimeter of the panel, as well as screws into all the glue blocks running from the bottom to top panels. It's solid!

Here are the end caps with a whole bunch of wood filler to smooth them out and fill the gaps. Yes, the speaker isn't pretty underneath, but it doesn't matter, as the entire box will be covered with fabric and the end caps. It just has to be solid and leak free, which it is.


Here's a shot of the crossovers peeking in through the holes in the side panels:


Here's how the end caps are held on. Two 1/4" thick custom wood washers fit over the nut and bolt on the end cap, which are then secured with a fender washer and wing nut. This was done because I wanted no visible fasteners on the end caps, and I also wanted to be able to remove them easily for refinishing or replacement.

That's it for now! You'll have to wait until tomorrow to see pictures of everything fully assembled. It's in the car now so that I can take it to work for testing tomorrow, and I'm not hauling it out at 1:00 AM for pictures. Although I can lift 60 pounds, it's a very awkward load to carry very far.