DIYSG Franken-Fusion 8 Towers and Center - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 20 Old 08-12-2017, 06:17 AM - Thread Starter
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DIYSG Franken-Fusion 8 Towers and Center

So, I'm a total non-woodworker and started my DIY journey with a set of Volt-6 LX's. They turned out great (thread to come).

I turned my attention to my LCR and, for my situation, I really wanted full towers and a center. WAF dictated 8" max drivers and I settled on the Fusion 8 Alchemy Towers and F8 Center but, the tower needed some modification for my needs.

**rubbing hands**

My Franken-Fusion 8 towers are basically the F8 Tower baffle (pic from the website attached) with:
  • roundovers chopped off
  • port moved up
  • square-edged top and sides added, and
  • bottom section added
...essentially making a shorter, deeper F8 section inside a 40" tower with an integrated stand (see pic).

The last section of the tower is sealed from top section so the cabinet volume of the top section is the same as the full tower spec.

For now, I need some advice... and I'll tell the whole build story below.

Q - how best should I fill in the "stand" portion at the bottom? I know sand would be good, but I think it'll be too heavy. Would foam mattress topper + polyfill be enough?

TIA... more to come!



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post #2 of 20 Old 08-12-2017, 06:17 AM - Thread Starter
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The Story

Like many DIYers, I ended up here with zero woodworking skills after constantly searching for higher bang-for-the-buck for a home theater upgrade.

After tons of research and, since my sub was so capable (Rythmik D15) and my receiver was not, I ended up looking for speakers with:
  • high focus on performance
  • less focus on cabinet prettiness
  • high efficiency
  • more focus above the 80ish Hz crossover point
  • and I was willing go a little bigger if need be.

I ended up really liking Power Sound Audio's speaker line but, they were juuuuuust too big. If they made 8" designs, I probably would have stopped there.

Eventually I came across DIYSG and, after warming up to idea, I sprung for the Volt 6's. So much fun! Great performance. Time for LCR.

We have three little kids so my perfect LCR needed:
  • Grills!! (kids - woofer protection)
  • no exposed ports (kids - no toys in daddy's speaker please)
  • full tower (kids again - lowest topple risk)
  • max 10' width (WAF)
  • matching horizontal center channel (big entertainment unit)
  • LR tower tweeter/HF driver in the top section (WAF: highs at ear height without getting too tall)

The F8 towers were perfect... after a little modification.

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post #3 of 20 Old 08-12-2017, 06:18 AM - Thread Starter
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Flat packs were only available for the F8 Center. They're easy to knock up but you learn about using wood glue.

Flat pack ready to go:




Drilled 3" and 2" holes for the circular terminal up. I'll use a router so the cup will be flush fit.




Glue up process over a couple of days.







Fully done with seams sealed and pilot holes ready for the driver:

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post #4 of 20 Old 08-12-2017, 06:18 AM - Thread Starter
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Reserved - Tower 1

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post #5 of 20 Old 08-12-2017, 06:18 AM - Thread Starter
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Reserved - Tower 2

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post #6 of 20 Old 08-12-2017, 06:29 AM
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Use a couple of gallon size freezer bags filled with dried sand and surround those with stuffing of your choosing.
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post #7 of 20 Old 08-12-2017, 06:53 AM
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Why waste that space? A bigger cab will only help with the low end. I'd cut a big hole in that divider and use all the cab volume.
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post #8 of 20 Old 08-12-2017, 07:01 AM
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Are these being integrated with a sub?
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post #9 of 20 Old 08-12-2017, 07:40 AM - Thread Starter
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Quote:
Originally Posted by Saber008 View Post
Are these being integrated with a sub?
Yup - a servo-controlled 15" that fills my room nicely.

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post #10 of 20 Old 08-12-2017, 08:37 AM - Thread Starter
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Quote:
Originally Posted by Samps View Post
Why waste that space? A bigger cab will only help with the low end. I'd cut a big hole in that divider and use all the cab volume.
@Samps - Thanks for the feedback. I'm working with a proven design and I think the crossover design and port all contemplate a certain cabinet volume. I'm not sure how flexible I could be and I didn't feel comfortable deviating any more than I already have. I'm willing to be proven wrong on the cab size thing and if so, I'd open that last section up.

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post #11 of 20 Old 08-12-2017, 09:24 AM
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I can model it later if you give me the two cab volumes.

I also have custom built fusion 8 towers and fusion dual 8 towers.
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post #12 of 20 Old 08-12-2017, 09:40 AM
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Quote:
Originally Posted by Samps View Post
I can model it later if you give me the two cab volumes.

I also have custom built fusion 8 towers and fusion dual 8 towers.
Samps, would you mind sharing your towers plans and performance?
I've been involved in the DIYSG Magnum 12 thread. I'm looking at a way to get more full range sound on a lower budget without needing external amplification.
This Fusion 8 Tower modification you guys have here might just do the trick.
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post #13 of 20 Old 08-12-2017, 11:04 AM - Thread Starter
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Quote:
Originally Posted by Samps View Post
I can model it later if you give me the two cab volumes.



I also have custom built fusion 8 towers and fusion dual 8 towers.


That's very kind of you: your F8 towers were a part of my early inspirations!

I'll measure them up when I get home.

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post #14 of 20 Old 08-12-2017, 11:04 AM
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My dual 8 towers are very similar to the stock design. Mine are just made of plywood instead of mdf. I did trim the ports shorter to boost up the 80-100hz range at the expense of some extension.

My single 8 towers are similar to the dual 8 towers but with a single 8. This adds a good bit of bass since the cab volume is almost doubled. I also used a 2.5" round port that was trimmed to get the most 80-100 bass.

IMO the fusion 8 kits are tuned too low if you're using an 80hz crossover. Extension down to 50hz isn't very useful if you're going to chop it off at 80. I prefer to tune them higher.

I have some sweeps with the full port tube, the tube removed completely and the tube cut in half. You can clearly see how things change.
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post #15 of 20 Old 08-12-2017, 11:30 AM
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So by increasing the enclosure volume, you get deeper bass extension correct? Any idea how much extra extension and output?
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post #16 of 20 Old 08-12-2017, 12:18 PM
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You really need to model or build and measure to find out. At some point you reach the point of diminishing returns.

The max spl won't go up, but you'll get a flat response to a lower frequency.
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post #17 of 20 Old 08-12-2017, 03:01 PM - Thread Starter
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Ok - here are my measurements (internal dimensions, not excluding bracing)

1 - as is (bottom sealed off)
27" H x 8 3/8" W x 10" D

2 - full internal volume
38.5" H x 8 3/8" W x 10" D

all with the regular kit port.

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post #18 of 20 Old 08-12-2017, 05:40 PM
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NOTE: these models are estimates. I used the specs for the beta-8 from PE assuming they are close to the custom version that diysg uses. Modeled with 100 watts.

Red is the smaller cab, green is larger cab, and blue is the larger cab with the port tube cut in half.






These are the same models with a second order high pass filter at 80hz.





I wouldn't go cutting the port tubes until everything is assembled and tested. You can only get those tubes from diysg, ask me how I know.
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post #19 of 20 Old 08-12-2017, 07:09 PM - Thread Starter
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Quote:
Originally Posted by Samps View Post
NOTE: these models are estimates. I used the specs for the beta-8 from PE assuming they are close to the custom version that diysg uses. Modeled with 100 watts.

Red is the smaller cab, green is larger cab, and blue is the larger cab with the port tube cut in half.
Man this is super interesting. Thanks so much!
The red and greed track so closely above 80 Hz.... even down to say 55 Hz... I wonder if it's worth going off spec. If I'm looking at the right speaker, the Beta-8 is 8 Ohm but the custom ones in the F8's are 16 Ohm. Still, I don't know enough to know if that makes a difference.

I wonder also if @Erich H or @Jeff Bagby would be willing to chime in.

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I wouldn't go cutting the port tubes until everything is assembled and tested. You can only get those tubes from diysg, ask me how I know.
No wonder I couldn't find those things anywhere! That blue line looks like the best option but I don't think I'm willing to cut that tube!

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post #20 of 20 Old 08-12-2017, 07:40 PM
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You could leave everything as is and adjust later if you feel like it. Simple enough to open up the bottom section or cut the port tube.

The differences will be minimal either way. I like to run really hot bass so a little bump around 80hz helps the transition a bit.

These woofers seem to sound better as time goes on. They are really stiff out of the box.
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