Fusion-15 Sentinel Build @ ~50Hz Tune - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 24 Old 11-08-2018, 09:11 PM - Thread Starter
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Fusion-15 Sentinel Build @ ~50Hz Tune

Now that the Sentinels are on close out at DIY Sound Group, this thread may not be as relevant as it used to be, but thought I would document my progress nonetheless.


I was wanting a LCR to produce enough mid-bass where I would hopefully not have to build MBMs. Erich didn't have enough flat packs for 3 kits so I'm going to be building my own boxes.


I'm going to be building boxes ~5.5 cubic feet and tuned to around 50Hz. I'll still be using Erich's sexy CNC cut front baffles, but I'll be building the boxes to 24" deep and have to route out the ports. A big shout out to @mtg90 for all his help with the tune.

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post #2 of 24 Old 11-08-2018, 09:12 PM - Thread Starter
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SketchUp of the cabinet.
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post #3 of 24 Old 11-09-2018, 12:36 PM
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hope this works out . .

OTOH, if you are using BM then in all likelihood you'll end up setting them to "small' https://www.avsforum.com/forum/images/smilies/eek.gif

where audy sets the xo to ? > TBD

Matt was a huge help when I did mine . .

keep us posted and more pics

I really got my attention when the CD weighed more than the 15" driver . .

DIY FAN Denon X4400 , ATI A 2000 for 7.4.6 SCATMOS Sammy 82" 4K/HDR
L/R: Fusion 15 V2 , C: 88 Special , SL/SR: 88 Special(V2) , RL/RR: F-3, TF/TR: Volt 6's TM: SLX, FH: F4Q4
SUBMAXIMUS V2, ,Submaximus V3,LOWARHORNCustom Dual Driver VBSS,2 x 6000DSP

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post #4 of 24 Old 11-09-2018, 01:51 PM - Thread Starter
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Quote:
Originally Posted by asarose247 View Post
I really got my attention when the CD weighed more than the 15" driver . .
I'm with you. When I pulled those little boxes out I could have swore they were filled with lead. Also, those magnets. My tape measure was sticking to the outside of the box.
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post #5 of 24 Old 11-09-2018, 02:28 PM
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Are you going to put those on stands? If not the waveguide will be well below ear level. You could build a taller shallower box and attach the baffle on the front.

5.5 cubes is big for a 50hz tune. It will give you a pretty big bump in that range which I'm assuming is your plan. Mine are only 3 cubes with a 50hz tune and they have a decent bump in the bass range.
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post #6 of 24 Old 11-09-2018, 02:38 PM - Thread Starter
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My stands are going to be my subwoofers. It's likely I may have to have the speakers upside down where the waveguides are on the bottom due to the height of the subs.
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post #7 of 24 Old 11-09-2018, 02:46 PM
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That works. I think you'll be surprised how much bass you can get out of those 15s. Shame that design is fading away. It's not full range but plenty of bass for music.
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post #8 of 24 Old 11-09-2018, 07:10 PM - Thread Starter
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Working on the crossover layout and wiring. I plan on installing a switch to enable/disable the optional HF padding resistor. Any suggestions to better placement or did I get something wrong?

I screwed up on the 4mH coil wiring. Uploaded corrected layout. Anybody else see any other errors?
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post #9 of 24 Old 11-09-2018, 10:23 PM
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I have JTR 215RT’s as my LCR and still use midbass modules. My 215’s have a ton of midbass and can give you the kick in the chest if turned up loud enough. The problem is at lower listening levels -20 to -15 the kick isn’t there because they are too far away from me (16 ft). I can put the midbass modules directly behind me and separately adjust their volume to provide that kick at lower volumes which I can’t do with my 215’s.

You May still need/prefer midbass modules depending on your room SBIR and distance from your speakers and subs.

http://www.mh-audio.nl/CancellationFreq.asp
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post #10 of 24 Old 11-10-2018, 12:19 PM
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Positive HF path from the 5.1uF cap should flow through the 2.2uF and 10 Ohm resistor and out to the HF output / 4.7 and 20 Ohm resistors. Right now you have the 2.2uF and 10Ohm resistor bypassed.

See attached image.
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post #11 of 24 Old 11-11-2018, 09:08 AM - Thread Starter
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Agh. Thanks @mtg90 . I fixed and reuploaded the original.
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post #12 of 24 Old 11-12-2018, 08:11 PM - Thread Starter
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Modeled the bracing. There's no way I can do bracing like Erich's CNC, but I used them as a template to determine where mine should go.


Also ordered the walnut veneer.
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post #13 of 24 Old 11-15-2018, 06:36 PM - Thread Starter
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Walnut veneer has arrived.
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post #14 of 24 Old 11-25-2018, 02:48 PM - Thread Starter
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MDF all cut. Crossovers are done.




I'm going to do some testing on flush mounting the HF padding resistor switch so it doesn't stick out the back.
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post #15 of 24 Old 11-26-2018, 02:49 PM - Thread Starter
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As far as the switch goes for the HF padding resistor, I had originally been thinking about mounting it to a plate then accessing it through a hole. What are the thoughts on just drilling a hole in the terminal cup and mounting it there? The recessed cup looks to have more room above the terminals than the regular cups but there's not a technical drawing for me to know how much room there is. There is a comment that indicated somebody put a combo Speakon jack in the same cup, so there should be enough room for a microswitch.

https://www.parts-express.com/gold-b...l-cup--260-311
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post #16 of 24 Old 11-26-2018, 03:04 PM
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Quote:
Originally Posted by Witchboard View Post
As far as the switch goes for the HF padding resistor, I had originally been thinking about mounting it to a plate then accessing it through a hole. What are the thoughts on just drilling a hole in the terminal cup and mounting it there? The recessed cup looks to have more room above the terminals than the regular cups but there's not a technical drawing for me to know how much room there is. There is a comment that indicated somebody put a combo Speakon jack in the same cup, so there should be enough room for a microswitch.

https://www.parts-express.com/gold-b...l-cup--260-311
At 4-1/8" OD you'll have lots of room for a switch above the posts. I use 2-7/8" OD cups and could fit a small switch in them easily.

If using banana plugs however, those may get in your way. How much so would depend on how often you switch the padding on/off I suppose.
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post #17 of 24 Old 11-27-2018, 08:25 PM - Thread Starter
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The toggle for the switch is only 3/8" long so there should be enough room. I went ahead and ordered the recessed cups. We'll see how they work out.
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post #18 of 24 Old 12-07-2018, 06:53 PM - Thread Starter
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Boxes cut and glued.


Working on the double bezel. Marking the center of the circle to cut out with the router for the woofer.


I think the larger cup was definitely overkill for the switch, but there will be more than plenty of room.


It's getting cold so likely work will slow down as my garage is not heated.
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post #19 of 24 Old 12-08-2018, 04:57 PM - Thread Starter
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Quick jig for the woofer cut out in the bezel.


Dry fitting both bezels.


First bezel glued in place.
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post #20 of 24 Old 06-08-2019, 02:09 PM - Thread Starter
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Rain is slowing down where I can move the car out of the garage and work on these a little.

Drilled and installed the microswitch in the terminal cup. This cup is way bigger than I needed, but I already bought them, so we'll make them work.



Used gasket tape on the back to seal the microswitch.



Gluing the second bezel in place.



This particular box was 1/16" shy on the bottom, so used PL to fill the gap. Gave it 30 minutes to set to where it turns into a clay consistency then scraped it off clean with the box. Will still have to do some filling.

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post #21 of 24 Old 07-08-2019, 07:51 PM - Thread Starter
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Got some more work done on these. Dang bearing came off my flush trim bit and cut into the side. Glad I wasn't doing something like trimming veneer.



Yay Bondo!



All the prep work for the wood is finished.



Foam installed. They are now ready for veneer. May be able to get that done this weekend. Fingers crossed.

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post #22 of 24 Old 07-09-2019, 12:02 AM
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Quote:
Originally Posted by Witchboard View Post

Working on the double bezel. Marking the center of the circle to cut out with the router for the woofer.

Bisecting chords to find the center. Someone did well in geometry.
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post #23 of 24 Old 07-11-2019, 03:29 PM
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Got some more work done on these. Dang bearing came off my flush trim bit and cut into the side. Glad I wasn't doing something like trimming veneer.



Yay Bondo!



All the prep work for the wood is finished.



Foam installed. They are now ready for veneer. May be able to get that done this weekend. Fingers crossed.

Nice recover from the flush trimming mishap. Looks like you're close to testing them out. They always sound better after they break in a bit. Looking forward to the walnut veneer!
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post #24 of 24 Old 07-12-2019, 07:51 AM - Thread Starter
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Me too, but unfortunately it won't be this weekend as I had hoped. The earliest I'll be able to work on these again is the end of the month.
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