Jump to content

Cinema F-20 build thread


CECAA850

Recommended Posts

  • 3 months later...

Carl,

Would you recommend MDF over Ply? I do like the idea of no end grains to cover up.

Also, I have a Kreg Jig. Would you recommend doing the pocket hole method again? From my other projects, they make some pretty serious joints.

How did you clean up the squeeze out of the PL? Sand it off?

Edited by Beechnut
Link to comment
Share on other sites

The only reasons to use pocket screws is to avoid exposed screws and making blind joints where you can't get to the back side.  When I built this one, I was learning the Kreg Jig and wanted to see if I could build a box with no exposed screws.  I've learned something different on each and every build.  First, If you're building to tight tolerances, I wouldn't use the Kreg.  No matter how many different ways I've tried it, it's extremely hard to put your board exactly where you want it.  The design of the system pulls your wood off line slightly as you tighten it, even with drilling pilot holes.  The wet glue acts as a lubricant and helps the wood slide off line as you tighten it.  The most accurate method is to draw your sub out, clamp the top and bottom plates together and drill both plates at once.  It's easy to pull the screws and bondo the holes.  I just started my next build and that's the method I'm using. 

 

If you're concerned about end grain showing through, you can use MDF or bondo and sand the end grains.

 

By far the easiest way I've found to clean up PL is to wait exactly one hour after application and scrape it off with a putty knife.  Any sooner and it's messy along with not having swollen completely.  If you wait much longer, it cures hard as a rock and is a real PITA to get off.  It sands at a different rate as your stock so be careful as it's much harder than MDF or birch.

 

Lastly (even though you didn't ask) don't pre cut your panels.  Draw everything out and measure every panel as you go.

Edited by CECAA850
  • Like 1
Link to comment
Share on other sites

Great tip on the PL. And I'll take the advise on NOT pre-cutting the panels.

 

Did you end up doing bracing? Lilmike says he wasn't to worried about it since it was a house speaker (not a PA system) and he used 13 ply plywood.

 

I'd think MDF would more rigid and structurally sound...and less likely to need bracing than ply. Am I off base on that?

 

Don't really desire any wood grain look, (like staining the ply) So I guess material doesn't matter on finish if I'm just going to bondo everything for a smooth foundation.

Link to comment
Share on other sites

IMO 3/4 inch plywood will not need bracing in this build. This is one heavy box.

I used pocket screws in my two builds and remember fondly the pieces sliding around. As much as I love pocket screws for their ease, it requires extra hands when combined with PL.

Edited by tromprof
Link to comment
Share on other sites

With my Cornscala build from a couple of years ago, I used pocket screws and dry fit everything with the screws first.

Once I was happy with the way things were going together, I dis-assemble and then re-assembled using PL.

I didn't find enough slipping to matter.

Mind you I built all the exterior joints "proud" by about 1 mm and then trimmed with the router after and sanded.

Link to comment
Share on other sites

Mind you I built all the exterior joints "proud" by about 1 mm and then trimmed with the router after and sanded.

 

That's the biggest time saving point (that I forgot to mention) yet.  I run about 1/16" over on my top and bottom panels.  The mouth trimming can be handled a couple different ways but it's not too bad.  You wouldn't have that issue with a box like a Cornwall.

Link to comment
Share on other sites

I finished my extra wide F20. I decided to go with 24 inches, in total is 25.5 inches with the sides on. This thing is pretty amazing. Its not painted or finished yet.

Amazing sound? I can't imagine you are impressed with the size, since you own an 1802.

Link to comment
Share on other sites

  • 1 year later...
On ‎8‎/‎27‎/‎2014 at 8:47 PM, mustang guy said:

I see where the lilmike thread is recomending the Stereo Integrity HT-15. $145.

 

Here are the specs: 

 

22.5mm Xmax (one-way linear)

43mm Xmech (one-way)

8" diameter Nomex spider

Sewn on leads

Large speaker terminals

Cast basket

2.5" diameter voice coil

Spiral cut CZA alloy former

Dual 4 Ohm

600 watts RMS power handling

High roll rubber surround

Inner magnet diameter shorting ring

Blank dust cap

 

15" D2
Re: 3.7 Ohms
Fs: 18.5 Hz
Qes: 0.37
Qms: 6.3
Qts: 0.35
Le: 3.5 mH
Sd: 80445 mm^2
Vas: 220 l
BL: 18.9
Mms: 309 g
Cms: 239
Sensitivity (1W/1M): 87.4 dB
Xmax: 22.5mm
 
Recommended enclosures: 15"
Sealed = 3 ft^3
Ported = 5 ft^3 tuned to 22 Hz
Cutout: 14.0"
OD: 15.5"
Mounting depth: 8"
Mounting flange to top of surround: 1.5"
Displacement: 0.19 ft^3

 

 


Adding for research.  Apparently these can't be found or I am not looking in the right place. 

 

I will have to check over at the AVS forum. Anybody know if there is a more preferred woofer to use in the F20 these days? 

 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...