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Old 27th December 2013, 03:02 PM   #2091
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You fellas have some mad skills!
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Old 27th December 2013, 03:41 PM   #2092
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Default XPS foam & FC MLTL with PE 6.5 in Polycone driver - Build #1

Starting the next build - my first straight MLTL (aka, monkey coffin) with the wonderful 'Buyout' 6.5 in polycone driver from Parts Express. If you did not get any of these when they were on sale for $4.88, you should have, because they sound great. They are high Qts, but that is perfect for FC projects and they get deeper bass extension in MLTL designs than low Qts drivers. I have measured these in an OB and they are flat from 50 Hz to 2kHz with breakup starting at 3 kHz. They actually sound quite nice on their own but wonderful with a cheap piezo supertweeter - no XO needed.

This design was first optimized for bass extension and flat response first, then modified to fit with available conservation of materials. This is my first project with expanded polystyrene (XPS) foam sheathing insulation from HD. It is 1 in thick - very uniform, strong, and light. Cuts cleanly like butter with a new utility blade. I will use it for the sides and the front, back, tops and bottoms will be dollar store FC. The design ended up at 47 in tall, 8 in wide, 12 in deep with a 2 in x 3.5 in x 3.0 in Long port at 6 in from bottom. The driver is 9 in from the top. This design is predicted to have an average of 90 dB and be able to reach about 30 Hz at -3dB @2.83v at 1m.

For the build, I lined the areas surrounding the driver with open cell foam and added some eggcrate foam at the bottom to prevent reflections. So far I got to the capping operation but ran out of hot melt glue which is needed to tack the sides while the PVA dries. Another trip to the store for hot melt will be needed soon.
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Old 27th December 2013, 05:31 PM   #2093
bcmbob is offline bcmbob  United States
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I think it's time you quit your day job and opened up a chain of walk-in DIY FC speaker stores.
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Old 27th December 2013, 06:05 PM   #2094
xrk971 is online now xrk971  United States
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Default FC Labs

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Originally Posted by bcmbob View Post
I think it's time you quit your day job and opened up a chain of walk-in DIY FC speaker stores.
Bob, thanks and happy holidays!

Yes, and I will call it FC Labs...

The only place you can buy a great sounding full-size speaker that you can pick up with a pinkie finger.
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Old 27th December 2013, 06:07 PM   #2095
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Your wife must be a angel !! Most likely an offspring of Gabriel
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Old 27th December 2013, 06:18 PM   #2096
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Quote:
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Your wife must be a angel !! Most likely an offspring of Gabriel
Yes, she is, and I am a very lucky man!
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Old 27th December 2013, 06:38 PM   #2097
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Brilliant X
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Old 27th December 2013, 07:03 PM   #2098
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Turk182 pointed out that there were some missing family members in the holiday photo. Still missing 4 sets...

Click the image to open in full size.
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Old 27th December 2013, 07:06 PM   #2099
bcmbob is offline bcmbob  United States
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Thought they might have been sent to the orphanage by Ebenezer - but alas .....
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Old 28th December 2013, 04:42 AM   #2100
xrk971 is online now xrk971  United States
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Default XPS foam & FC MLTL with PE 6.5 in Polycone driver - Build #2

After 6 hrs for the PVA to dry, I installed the driver and a piezo tweeter flush mounted. It is a lot more stable standing upright than I thought it would be given that the majority of the weight is the driver up front. It is a big speaker standing nearly 4 ft tall and 10 wide x 12 in deep. Initial listening impressions are good from bass extension (well into circa mid 30 Hz is my guess from listening to it by ear) but a bit lacking in amplitude of the bass - I think I have too much stuffing. I will reduce stuffing in the morning and listen again. The Realistic piezo tweeter seems to be integrating nicely with the woofer though. If I recall, these units are 3 kHz and above - which is a nice crossover with the woofer. Measurements to come after stuffing adjustment.
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