Triple 12" OB H-frames

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Early B.

Re: Triple 12" OB H-frames
« Reply #60 on: 19 May 2015, 02:16 pm »
Any room as small or smaller than the typical hotel exhibit room is a small room. They are about 13' by 19'.

Hey -- my room is 13' x 20', so I just made the cut-off! From this point forward, I'm gonna snub my nose at anyone with a small room. :lol:


rollo

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Re: Triple 12" OB H-frames
« Reply #61 on: 19 May 2015, 03:13 pm »
   Danny is there a minimum distance from sidewalls or rear wall required ? If my speakers are 6ft center to center and the subs flanking the speakers and are facing forward what is the minimum distance required for triple OB subs ? Thanks. Speakers are out 5.5 ft from rear wall. Room is 16ftW and 15 ft long.


charles

Danny Richie

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Re: Triple 12" OB H-frames
« Reply #62 on: 19 May 2015, 03:21 pm »
   Danny is there a minimum distance from sidewalls or rear wall required ? If my speakers are 6ft center to center and the subs flanking the speakers and are facing forward what is the minimum distance required for triple OB subs ? Thanks. Speakers are out 5.5 ft from rear wall. Room is 16ftW and 15 ft long.


charles

We recommend at least three feet to the front wall (wall behind the OB drivers). You can actually get them pretty close to the side walls with no issues.

rollo

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Re: Triple 12" OB H-frames
« Reply #63 on: 19 May 2015, 04:05 pm »
  Thanks Danny.


charles

Erpeder

Re: Triple 12" OB H-frames
« Reply #64 on: 19 May 2015, 04:15 pm »
Any room as small or smaller than the typical hotel exhibit room is a small room. They are about 13' by 19'.

Thanks, My room is a small room 15' x 19' and I don't play load, any longer. So I Can use 2 or 3 8" in the U-baffel or use My 12" OB servo woofers in a new U-baffel side placed drivers, wider in the rear than the front, to minimize the ported effect. And then have a smaller Cabinet than My H-baffel, gloser the frontwall.

Danny Richie

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Re: Triple 12" OB H-frames
« Reply #65 on: 19 May 2015, 10:13 pm »
Thanks, My room is a small room 15' x 19' and I don't play load, any longer. So I Can use 2 or 3 8" in the U-baffel or use My 12" OB servo woofers in a new U-baffel side placed drivers, wider in the rear than the front, to minimize the ported effect. And then have a smaller Cabinet than My H-baffel, gloser the frontwall.

I have not tested the 12's in a side loaded U shaped baffle.

rak313

Re: Triple 12" OB H-frames
« Reply #66 on: 19 May 2015, 10:32 pm »
Keep in mind that at 90 degrees off axis there is a null where there is no output. Open baffle designs need to face the listener.

I don't understand.  The cancellation at 90 deg is due to the 2 sources being 180 out of phase and both sources being the same acoustic path distance to the observer.  The tilting of the driver doesn't change that.  Looking at the pic below, if you take the "top half" and place it directly to the left of the "bottom half", you essentially have the "W-Frame" (on its side) from your SW-12-16FR web page here: http://www.gr-research.com/pdf/obsub.pdf 


Danny Richie

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Re: Triple 12" OB H-frames
« Reply #67 on: 19 May 2015, 11:04 pm »
rak313,

What you have drawn will work. However... You still have a large un-braced panel. I used that design with the V-2's but had to double up the wall thickness and line them with No Rez to control wall flexing.



And this was with a conventional woofer that doesn't have near the output of the servo subs.

These also had small Neodymium magnets that allowed them to fit in that way.



The huge motor structure of the servo subs will need a lot more room for mounting them behind each driver.

rak313

Re: Triple 12" OB H-frames
« Reply #68 on: 20 May 2015, 12:24 am »
Very nice looking speakers.  You already had me convinced in previous posts that bracing is very important.   

Captainhemo

Re: Triple 12" OB H-frames
« Reply #69 on: 20 May 2015, 05:42 am »
More progress on the   cabinets

After laminating the bases (2 x1" MDF) , I  laid out  4 mounting screws  as well as the  holes for the   threaded 8mm inserts for the spikes.  Bases were final cut to be 2"  larger than the cabinet on all sides.




Baes were then temporarily installed / test fit  on  the cabinets


Grill frames were cut 41.5" x 15" to leave a .5"  "border"  when in place. Laid out and pre-drilled small pilot holes in  the 8 magnet locations on the  grill frame blanks


With the bases still  dry fited, the grill blanks were clamped in place to  transfer magnet locations to cabinets by lightly spinning the same bit used to drill the grill frames


After removing the blank and base, each cabinet was laid down  and each marked hole was drilled to the proper depth for seating the magnets.  Each  magnets is expoxied into place  and  skim coated with a  bit of filler before  blcok saninding flush.  No need to worry abouot magnet polarity, just be sure to  orientate properly when  you  later istall the magnets in the frames.

The frames will have to be finished off later, need to get the cabinets off for painting by the weekend.

Bases were removed ,  a 3/4" roundover  applied, sanded , then  glued/screwed into place  for the final time




Prep will continue tomorrow

jay
« Last Edit: 21 May 2015, 02:44 pm by Captainhemo »

PDR

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Re: Triple 12" OB H-frames
« Reply #70 on: 21 May 2015, 07:01 pm »
Really nice work Jay, going to look amazing..... :thumb:

Captainhemo

Re: Triple 12" OB H-frames
« Reply #71 on: 22 May 2015, 01:20 am »
Really nice work Jay, going to look amazing..... :thumb:

Thanks Perry  !   Pretty much done, one final sanding,  a quick coat of bed liner on the bottom of the bases and they're out the door  (tomorrow afternoon or Sat am) to get painted
Will post a couple more pics before they go out


jay

Ron

Re: Triple 12" OB H-frames
« Reply #72 on: 23 May 2015, 01:29 pm »
  The cabinet construction look great Jay. Nice job !   :thumb:  Anxious to see a picture of them after they have been painted.

Captainhemo

Re: Triple 12" OB H-frames
« Reply #73 on: 24 May 2015, 02:23 am »
Thanks Ron,  we dropped them off for paint this am, not  sure of a time frame.

Here are a couple more pics before   they   went out

Sprayed the bases with   truckbed liner, I like using it as it's pretty durable.   Insertes were threaded in for the final time and  threw the spiks in just   because 


Dealing with seams....  just never seems to end.  You think you've got it beat then   you find a bit more.  I went out this am to give the cabinets a final wipe down and ended up spending a bit more time sanding.    This is how the seams looked going out the door


One final pic  all  wiped down and ready to go


More pics when they get back !

jay

mlundy57

Re: Triple 12" OB H-frames
« Reply #74 on: 24 May 2015, 02:26 am »
I know what you mean Jay, seams are a royal pain.  Looking good though.  What type of paint job are they getting. It doesn't sound like your usual?

Mike

Captainhemo

Re: Triple 12" OB H-frames
« Reply #75 on: 24 May 2015, 02:35 am »
Mike,
We took the cabinets to a local automotive painter for a base caot/clear coat. They'll first hit the cabinets with a   coat of primer/sealer, give them a quick once over,  and   then  paint away.
My buddies wife got to pick the color , looking forward to seeing the results   !!

jay
« Last Edit: 24 May 2015, 06:16 am by Captainhemo »

Captainhemo

Re: Triple 12" OB H-frames
« Reply #76 on: 25 May 2015, 04:31 am »
Spent a bit of time in the garage this afternoon and got back to work on those grill frames.

Continued on with these by  first rounding  each of the four corners and then putting a 3/8" roundover on the front edge


After  a bit of light sanding,  the frame with it's basic  shape


Next I cut out a 13" circle at each end of the frame. 


To cut out the middle section, I use a long  piece of 1/2" MDF as a guide. Line it up with the edge of the cutouts and  secure in place  by either clamping or using  a couple small screws throug  the pilot hoes  for the mangets.  Then  just  use a flush trim bit   to make a clean cut between the  two cutouts.  Repeat for the other side




Once the cabinets are back from paint, each magnet can be orientated correctly to it's mate in the cabinet and epoxied into place in the  grill frame,  After that, a dab of filler  for each pilot hole will  make them disappear

HAL

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Re: Triple 12" OB H-frames
« Reply #77 on: 25 May 2015, 12:55 pm »
jay,
I am thinking about having the local autobody folks finish my 12" H-Frame modules.  Talked to them awhile back and they only use water based finish systems.  Everyone thinks it is fine for finishing the MDF. 

The other idea is a Minwax sealer/stain system.

Watching how yours go to help with the decision. 

Captainhemo

Re: Triple 12" OB H-frames
« Reply #78 on: 25 May 2015, 02:40 pm »
Hey Rich
I think the  water based  system should work fine ,  at this point I sure hope it does !   I don't know if this  really matters much  but I pre-soak/coat  the  ends or open grain  if you will  with a water/glue mix so that the MDF would get sealed up.  I do that before the final  sandings  and it really seems to help make those end cuts more like the  finished sides.

The painter wanted to use his own primer/sealer which makes it tough for  prep I find.  I like to be able to   put something  on the cabinet to help show any problems.   They're in the painters hands now so we'll see, hopefully fairly soon  but I don't have a time frame. 

Will let you  know  how it goes and if  there are any issues with the  water bases automotive finish

jay

HAL

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Re: Triple 12" OB H-frames
« Reply #79 on: 25 May 2015, 03:08 pm »
jay,
Sounds like the same thing I was told.

Will be watching.   :D

Rich