H91 to H92 Horn Swap - The Build

[toddalin]

The build

When installed the drivers sit just under 1-1/2” behind the cabinet. I decided that rather than buy an expensive hole saw/bit, this could easily be cut out with the saber saw. With a 6” square hole, I could easily mount the horn/driver from the rear, though this was easier through the woofer hole. The rear “warts" were previously constructed of a 1-1/2” x 1-1/2” frame with a 6” ID and a backing of high-density 5/16” shelf board. A layer of acoustic padding was spray-adhesived to the back. When complete, the driver actually pushes into this padding tensioning the back/driver/horn/baffleboard.

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Concrete_Rocks/index_002.jpg

Additionally, the three H92 horns (LCR) were each previously treated to an 11 oz can of liquid spray-on rubber to dampen resonances.

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Concrete_Rocks/H92_The_Build013.jpg

Note the difference side-by-side.

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Concrete_Rocks/H92_The_Build002.jpg


Note the unmolested LE175. I found the other wax seal in the cabinet and pushed it back in-place.

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Concrete_Rocks/H92_The_Build009.jpg

To more easily locate the warts onto the cabinets and deal with the measurements for the cut, a template was made of stiff “folder paper.” This was sized to the warts. Once the outer template frame was made, the completed and drilled wart was placed on it and the holes located on the template. In this manner, once the square hole is cut in the cabinet, I can simply lay the template on, center it, and locate the screw holes in the cabinet. If I were to just to try to lay the wart on the cabinet, I would not be able to tell if it was centered to mark the holes.

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Concrete_Rocks/H92_The_Build003.jpg

The rear of the cabinet was taped over so that the saw would not scratch up the paint. The center of the hole is to be 11-7/8” from the top and centered side-to-side. Using the square inner portion of the template, I drew two lines across the diagonals to locate the center. After locating the exact spot on the cabinet, I put a small nail in the center of the square template and tapped it in place. I was then able to spin the square around this hub to best get it straight with the top and sides. After this was accomplished, I drew out the square on the tape for cutting.

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Concrete_Rocks/H92_The_Build004.jpg

No turning back now!

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Concrete_Rocks/H92_The_Build005.jpg

And the deed is done.

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Concrete_Rocks/H92_The_Build006.jpg

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Concrete_Rocks/H92_The_Build007.jpg


To be continued.

[toddalin]

After cleaning up the mess, the horn was ready for mounting. Having removed the woofer, it was a simple matter to rest the driver on the cutout while locating the flange on the baffleboard. Note the extra thickness of insulation in teh cabinet previously suggested by some Lansing Heritage members in an effort to reduce the woofer response dip.

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Concrete_Rocks/H92_The_Build001.jpg

In trying to mount the horn assembly to the baffleboard, the proper screws will drive you crazy trying to find the holes. But I found that if you take a 3” long ¼-20 screw, you can push it through a hole and easily locate this on the horn flange within the cabinet, well behind the baffleboard, where you can see it. Once this screw is started, it is a simple matter to locate the flange, place the other three, and remove and replace this one. This will also keep you from scratching up the finish on the horn flange (though it doesn’t show when mounted). I actually installed the horn a few (several) times this way trying to find which way the bell best centered in the hole. It is not perfectly round.

This shows the clearance around the driver wit hthe wart off.

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Concrete_Rocks/H92_The_Build010.jpg

And the back as it now looks.

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Concrete_Rocks/H92_The_Build011.jpg

The crossover was removed and extension wires soldered so that out of the cabinet testing can be performed. Testing is to be performed next time Linda goes to Yoga. For some reason, she doesn’t care for pink noise.

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Concrete_Rocks/H92_The_Build012.jpg

[timc]

For some reason, she doesn’t care for pink noise.





I thought all girls loved pink. :p



-Tim

[John]

I thought all girls loved pink. :p
-Tim

:scold:

[Fangio]

Two questions, if you don't mind

- did you consider to care for the horns inner surface also, i.e. smoothen it to a certain degree, as in brass instruments like a trumpet or sax? Often a desirable treatment IMO, some of those horns come with a pretty rough paint surface there

- does the cutout diameter allow for an optional LE85/2420 mounting later on?

[toddalin]

Two questions, if you don't mind

- did you consider to care for the horns inner surface also, i.e. smoothen it to a certain degree, as in brass instruments like a trumpet or sax? Often a desirable treatment IMO, some of those horns come with a pretty rough paint surface there

- does the cutout diameter allow for an optional LE85/2420 mounting later on?

1. Yes, I used sand paper and an emery board to smooth out major casting bumps and flaws. (I noted this on the forum before and I think most thought this was overkill.) I also filed away the small "lip" at the bell (you can feel it if you run your finger around the inside of the bell) and mount for a smoother transition (as I noted, like port-matching a high performance engine). Afterwards, I repainted the insides with several coats for a smoother finish.

2. Yes, I always try to plan ahead. The cutout was selected at 6" square so that an LE85 would indeed fit. There could be some file "beveling" of the top inside and bottom outside of the cutout required to accomodate the angle (<~1/8"), but the frame was purposely made thick (1-1/2") so would easily cover these small areas to be beveled.