Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Cabinets-Speakers => Topic started by: blindopher on April 01, 2014, 08:39:05 am
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Hi,
several noob Q's:
1. i'm going to screw the speaker marshall-style from the inside and into the baffle, no T-nuts. I'm noticing:
a. cone material partially covering basket holes - do I just punch through?
b. the basket holes are rather wide. What screws are recommended, and will the speaker eventually have to be manually aligned, since the screws i'll use will probabaly be thinner than the holes in the basket? Or not?
thanx!
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1. i'm going to screw the speaker marshall-style from the inside and into the baffle, no T-nuts.
What are you using? Wood screws?
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yes, i'm planning to use wood screws and screw from the inside of the cab throu basket hole into baffle which is 18mm (3/4") birch ply.
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That wouldn't be my preferred method...T nuts w/machine screws would be better. I take it the grill cloth is already on?
If you have to use wood screws, I would instead use sheet metal screws which are straight-sided---NOT tapered...#10 or #12. With washers..and the washers could be problematical as they could be too big in diameter to fit on the flat part of the spider. Maybe some nylon washers would be a nice touch. Predrill the wood, CAREFULLY controlling depth, and...I would take care selecting the hole size...practice on a piece of scrap.....and carefully measure and select the proper length of the screws. I'd consider filing or grinding off the point of the screws, as well. That way, you get more thread-bite and less chance of poke through. When you measure and select the length of your screws, if you are planning to file/grind the points off, remember the screws can be a tad less than 1/8" longer than you want since you'll be cutting them down slightly. PHILLIPS of course!! (or TORX or star.....anything but flat-blade) So your screwdriver won't slip off and pop the cone.
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yes, i'm planning to use wood screws ...
Agree with Eleventeen: I would strongly suggest machine screws, with T-nuts from the front of the baffleboard.
You might get away with wood screws once, but I suspect the holes will strip out quickly if you ever remove the screws. You'd also have some careful work to do drilling pilot holes. They would have to be small enough to get a firm grip, but large enough to allow screwing in without cracking the baffleboard.
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Is the hole in the baffle big enough in diameter to clear the edge of the speaker cone ?......
X2 on the sheet metal screws, if you don't use the T nuts...
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You know what? All is not lost in the T-nut department.
I am going to assume the grill cloth is on..... otherwise we would not be having this conversation.
If you were to position the amp grill cloth down, mark your speaker holes, then take the screw-on metal top of a jar.....or a piece of 3/8" plywood scrap maybe 3" x 3"...ROUND Off THE CORNERS. The jar top is perfect. (You round off the corners of the plywood so that if your drill happens you go too far, the spinning piece of plywood doesn't rip the heck out of your grill cloth.)
If you can control the depth of your drilling with reasonable accuracy...either with one of those screw-on collars or with some tape VERY carefully applied to the drill bit and you eyeball it......
You insert the jar-top on the front side of the baffle board, in one place, under one of your intended thru-holes. Open side towards the baffle board. The grill cloth should be able to stretch just that little bit. Drill your hole, be super careful as the drill penetrates the down side. Pull the jar-top. With luck, you should be able to sneak a T-nut thru the speaker opening, under the grill cloth, and get it into the hole you just drilled. Make sense?
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thanx to all for the good advise!
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I concur 100% with the T-nut recommendation. I have never seen a case where wood or sheet metal screws won't eventually fail. Having built dozens of cabinets I can attest to the simple facts. A strong baffle, well braced, properly vented box according to T/S numbers, quality speaker(s) preferably mounted out side the baffle (except when it will just not work), a T-nut in every hole, flats and locks where applicable, every fastener properly tensioned like when torquing lug nuts, a good seal around the edge of the speaker, no cabinet rattles, good wiring soldered to the terminals and premium terminals on the jack plate. I prefer banana jack, 5-way HD units in parallel with Speakons and 1/4" Switchcraft for redundancy. Anyone can plug anything into my cabinets including bare wire. I always label the terminal plate with the data on the speakers in the cabinet (i.e. EVM-15 X 2, net impedance 4 ohms) and when practical I provide a way either with a switch or separate terminals for each unit to bi-amp, bi-wire or select only one driver. When I use two drivers in a cabinet they are always isolated from each other if the cabinet has a sealed back. All wood joints are glued and screwed, all interior walls covered with carpet or fiberglass insulation, all ports cut to proper T/S characteristics to move the resonance point down. Each cabinet is carpeted outside with metal or plastic corners, solid, strong handles and casters on the large models. While my cabs are probably heavier than most they hold together under severe abuse and never rattle. I have seen cabinets I made 20, 30 even 40 years ago still in use. I have repaired a few with damaged drivers but that has always been from an amp that was over driven. Clipping kills speakers, not power. Jim