Converting a Danley TH115 to a TH118

R

Rick Powell

Freshman
Jan 15, 2011
80
1
8
Starved Rock, IL
After doing this, it's a lot of work and probably easier just to sell your TH115 and buy a TH118, but it came out OK. The drivers alone (B&C 18SW115-4) are over $1000 for a pair, plus about $60 in assorted hardware, and about 6 hours of work on and off. And the fact that I had access to a master woodworker and the wood shop of my local high school greatly helped the process.

This is a plan of the gasket and fill pieces I used to do the conversion. The fill piece is necessary because without it, the air from the driver isn't completely forced into the tapped horn as needed.
 

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  • TH 115 to 118 conversion gasket.jpg
    TH 115 to 118 conversion gasket.jpg
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Re: Converting a Danley TH115 to a TH118

I used 1/4-20 T-nuts to attach the speakers to the gasket. Wood screws to attach the gasket to the existing speaker plate, and to attach the fill piece to the gasket. Silicone to seal the fill piece so there are no air leaks into the rear chamber from the front side of the speaker.
 

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  • Gasket and fill piece silicone.jpg
    Gasket and fill piece silicone.jpg
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Re: Converting a Danley TH115 to a TH118

You can see that the difference in 15" and 18" chamber size, with the gasket installed, is not that great going into the front chamber of the horn (forward edge of the pic). I have never seen the guts of a TH 118, but all my research indicates that the TH 118 is essentially the same size and horn dimensions as a TH 115 with an extended speaker plate that incurs a little bit into the exit chamber of the horn, just like this one does. I made the gasket with a radius in back (following the outside edge of the 18" speaker) so that it would have minimum blockage of the air volume coming out of the horn exit. Not sure if a "stock" TH 118 does this, or if they simply use a rectangular speaker plate.

FYI, this pic shows the gasket in place before the fill piece was installed. The pic above (with the silicone) was just after I had slipped the fill pieces into place and attached them.
 

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  • Gasket installed.jpg
    Gasket installed.jpg
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Re: Converting a Danley TH115 to a TH118

I haven't tested the finished product yet...however, if I did everything correctly, it should behave just like any other "stock" TH 118 (unless there is some additional "secret sauce" inside a stock TH 118 that I am unaware of). I tried to take out as little of the back brace as necessary to fit the gasket and the driver; it was about 2 1/2" into the brace at the deepest part. I figure the brace in the TH 118 can't be any deeper than the one I was left with anyway, because the 18" has to fit in either case.
 
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Re: Converting a Danley TH115 to a TH118

Took these out for a live event with 8 acts last weekend, and they worked as expected. Slightly more efficient than a TH115, with noticeably more LF extension.
 
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