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Julz's 1850 Horns

Another great job on some 1850 horns. Julz said "Last weekend we used the PD1850 Horns, The Seleniumís and my OHM TRS 218/212 rig with some Vitavox compression horn tops outdoors and it sounded wonderful...sweet, loud with loads of kick". He also has a few comments and tips to share with us. I have also added a few words about his comments.

We had the sheets cut to 600mm wide (for all the interior and back panels) at the timber yard, and 750mm wide for the tops and bottoms. That left us just cutting the lengths and the mitres. There are a couple of cuts that caused a headache, the principle one being the panel at the base of the speaker compartment as the join where it meets the rear panel is at a very small angle and we ended up just using a plane to shave a millimetre or two of the angle rather than saw it. Butting up the access panel holding strips and sealing cured any imperfections!

Rog : What you need to make mitres over 45 degrees is a table saw with a vertical work clamp, also known as a tenanting jig. If you don't have one of these you could make a jig to hold the panel you are cutting up higher at the fence end of the saw. If your saw blade is at 45 degrees and you hold the panel to be cut at 5 degrees to the table, them you will get a 50 degree mitre.

The access panel is only just large enough for the driver to fit through. Let's hope it never needs replacing as the access to the front two bolts is going to be *very* tight!

Rog : It is a tight fit with this driver but I normally design cabinets with small access panels. The 1850 horn should give you at least 20 mm clearance for the driver, this is double the 10 mm clearance I normally allow for access panels. You have to be accurate with your measurements and cutting as accumulated errors can mean that things can get a bit tight around the access panel. You should be able to work to at least a 1 mm tolerance when building cabinets, I always cut and build to a 10th of a mm accuracy.

We decided to not measure and cut the braces from the plan, but to cut them once the panels are in place to ensure an exact fit.

The holes were cut with a router and jig as you suggested...a very good tip indeed...

I concur with your other builder who cautioned about not being able to easily screw and locate things if done in the wrong order, but it is possible...The particular area of concern were the large braces at the bottom of the throat, where they meet the inside panel.

Rog : I'm a bit confused with the last line, I take it you mean the two braces that sit in the mouth and brace the bottom of the cabinet to the last two flare sections.

Everything fitted together well, but we found the use of sash clamps were beneficial in holding the panels in place whilst the glue set. This made assembly slower than we would have liked, but the result was worth it.

Rog : I've never had to use any clamps to hold panels together whilst they dry. I can't see the benefit of using clamps, if you didn't use any screws then clamps would be necessary, but if you use screws I don't see what the clamps would be doing apart form getting in the way.

The joins of the interior panels were sealed with a Evo Stick filler/glue, sanded and will be painted over to ensure a smooth, gap free surface.

Rog : If the join is made correctly in the first place and you used glue to assemble the cabinet why are you gluing the joins again. If it is to fill gaps then 1. there should be no gaps. Use of the correct tools and taking enough time to do a good assembly should result in the cabinet needing no further filling or gluing and 2. if you do need to fill use a good wood filler or better still a 2 pack resin filler. If I had to seal joins later it would mean that I had failed to construct the cabinet well enough for proper use. If I felt the build was going that bad I would start again and take more time to get it right. If you have glued the panel on correctly then the join should be stronger that the wood it's self. Any attempt to break the join should result in the wood around the join snapping before the join breaks, if this does not happen something is wrong.

Julz powers the 1850 horns with a Crown MA 5000 VX and is going to make some MT 122's to go with the bass horns soon. His system should sound really good.

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