Tips and ideas Copyright 2012-19 © Troels Gravesen Answers to some of the most common questions I have LACQUER and OIL GLUING BITUMEN PADS AND FELT REMOVING STUCK DRIVERS MDF and BALTIC BIRCH TERMINAL BLOCKS/CONNECTORS SOLDERING FEET FOR CABINETS SEALING WIRE HOLES MAKING REBATES CABINET DAMPING, GO TO PAGE WIRING, GO TO PAGE PORT DIMENSIONS CHAMFERING DRIVER HOLES SPEAKER PLACEMENT TABS AND SLOTS FOR BRACES MY DAMPING PANELS
For crossover boards, silicone glue may work great, but this is even better and settles faster. Superfix from Casco or Bostic. Except for Scandinavia, I have no idea about the availability of this compound in other countries. It's expensive, around 20-25 US $ for 300 mls, but worth it. It's a non-toxic, doesn't smell, tough to get off your fingers, doesn't take any solvents except alcohol, flexible and easy to cut when hardened (remove crossover components for tweaking).
From Erik, Netherlands: From MB, Spain:
Finally, I’ve done more research about the “Ceys” glue and is a Spanish
product. It’s made in Bigues i Riells (Barcelona). Ceys is a company
that is part of “AC Marca Group”. It’s website is:
http://www.grupoacmarca.com/en
I’ve talked with them (so kind!) and have explained me that they have
subsidiaries in America (Mexico and Chile) and Europe (Portugal, Czech
Republic, Slovakia, Romania and Hungary), so maybe it’s easy to find
this glue in those countries.
The Tereson glue is Henkel product:
From Cole/US, I had these recommendations:
Glue for Bitumen Pads
Glue for cabinets
I use nothing but standard PVA glue
for cabinets. No nails or screws. I guess this is more or less the same all over the world.
"Wood
Glue" is usually PVA based adhesive.
Setting up speakers
It goes without saying that setting up speakers correctly is pivotal
for getting the best from your kit. There are loads of sites
on the web to help you out, and here's one:
http://www.cardas.com/room_setup_main.php
This one fits my room the best. The numbers mean of if you have the
speakers 1 meter from the front wall (the wall behind the speakers) you
have an optimal distance of 1.62 meters to the end walls of the room. If
you have the speakers 0.8 meter from the front wall, then 0.8 x 1.62 =
1.3 meters to the end wall. Download excel file here to find your placement from cells B25-26-27.
MDF AND BALTIC
BIRCH
Above my three preferred materials for cabinet construction, MDF standard, MDF black and Baltic birch. I rarely use anything but 15-16 and 19-20.5 mm thickness. The Baltic birch I use is usually 20.5 mm but it can vary a little. Sometimes I use 15 mm for bracing. Baltic birch may consist of 15 layers for a 20 mm sheet and the density is some 700 kg/m^3. It comes i various qualities, e.g. B/BB, which is what I use:
For most cabinets I use Baltic birch as it gives me the final finish at once without going through the trouble of veneering. See lacquer treatment below.
MAKING A
DRIVER HOLE BIGGER
Driver basket comes with tolerances and I always
advise not to route for drivers before you have them at hand and can
measure the diameter exactly. My new baby, the
JA8008-HMQ,
came in a basket 0.3 mm wider than the old one. This is within
tolerances, but my QUATTRO cabs had a very tight match to the driver and
I could not squeeze the new driver into the rebate and had to increase
radius by 0.2 mm.
TERMINAL BLOCKS/CONNECTORS
To make good connection between cabinets(e.g
Jenzen speakers) we need connectors that can be tightened hard and
represent little metal mass at the same time. I'll claim these
connectors are better and cheaper than anything else you can find and
much better than any banana plug in some dubious socket. Turns out Parts Express have them too: http://www.parts-express.com/nte-25-b100-04-4-pole-solder-lug-type-barrier-terminal-strip--090-856 item 090-856.
I have the question on soldering from time to time and here's what I
use. The Weller WSD81/WSP80 is expensive and much less than this can be
used for making perfect soldering. The soldering iron, WSP80, is 24V/80
watt and I mostly use a B tip for crossovers.
Take care when soldering tweeter terminals. They are usually fragile. Add solder to the wire and next to the terminal, but only for a second or so. Hold the wire to the terminal and heat as little and short as possible to make the two merge.
Gluing
bitumen pads and felt damping
Although bitumen pads may be self-adhesive, they
need to be glued to the panels. Years ago I relied on the sticky sheets,
only to find they would start peeling off a year or two later.
Screws for
mounting drivers
First of all: Threaded inserts and T-nuts: I
hate them! They do nothing good a standard wood screw cannot do. Do not think a speaker driver is a something meant to go into orbit. Fasten screws properly but don't overdo. I sold a 12" JBL driver to a guy complaining the voice coil was scraping. It turned out he'd fastened the driver so tight with T-nuts that he had bent the driver gasket! At some diy forum I read a posting from a guy claiming significantly improved sound from replacing his iron screws with brass screws. I suggest some proper therapy too!
REMOVING STUCK DRIVERS
Sometimes it can be a real pain removing a driver from its cabinet, maybe due to lacquer or tight routing and the simple solution is making treads in one the mounting holes in the basket. For 8" drivers usually 6 mm threads work. For 4-5" drivers maybe 5 mm. Measure hole diameter and use the the nearest size. Insert a screw and lift the driver with a plier resting on a piece of wood. Simple as that.
Router: Dewalt DW621 The great thing about the Dewalt DW621 is that
is has rotating suction at the top!
The guide can be bought from Jantzen Audio and also on eBay (Germany): http://stores.ebay.de/weyher-holztechnik As can be seen from the pics, the guide was modified as the pin (4 mm screw) is too large and un-handy for precision routing. I shortened the alu bar and inserted a 2 mm hard steel pin (concrete nail). The large handle on top was also omitted as this prevents routing very small holes.
Routing for driver rebate
TABS
AND SLOTS FOR BRACES
Faceting panels and fillets
I hope the images above and below are self-explanatory in how panels and fillets can be faceted. Obviously the same thing can be done with a planer and sandpaper but I admit you'll be less exhausted using a table saw. Faceting a whole front panel takes the rig seen on photos. I made this from some MDF leftovers. Faceting a fillet (final image) is easier as you don't need more than the standard table saw rip fence. Make sure you count ten fingers when you're done as you can't use the blade cover guard. Always make test cuts before doing your final panels to make sure all adjustments are done.
For small panels I sometimes use a rig attached to the sliding table.
Above the easy parts, the tricky parts I do by hand, view SP44 front panel. Here are the photos:
Cutting 45 deg for cabinets
Had the question on how to make these sharp 45 deg cuts: Cut from the
left side of the blade. Usually tilts towards your right.
How to make your DIY table saw:
The DTQWT front inner panel - may be useful in other places.
CHAMFERING DRIVER HOLES
The amount of energy coming from the rear of the driver is
exactly the same as coming from the front!
Read here
Normally I don not chamfer drivers holes once we're into 8" drivers, at
least not for 20 mm panels. For 40 mm panels I would.
Lacquer, paint
and oil
For finishing the Baltic birch panels I use synthetic lacquer applied with a roller. Semi-gloss 25-50 is used. Usually two coatings will do with in between sanding (grade 180). I sometimes add the 1st coat before the final cutting. This reduce edge ripping as the outer veneer of Baltic birch is rather thin, unfortunately. For cutting small object from Baltic birch without ripping edges I use a 4-6 mm MDF panel below the Baltic birch. Sometimes painters tape is enough to avoid edge ripping. PAINT
OIL
I mostly use mineral oil for the black MDF front panels. This product is for hardwood kitchen tables. It takes two coatings. For every application excessive oil must be wiped off before drying.
Flanging straight vents
made from ABS plastic: The pics below are
hopefully self-explanatory.
Solder tag
strips: This is a question I've had many times: Where do you get the solder tag strips used for the crossovers?
GASKETS
FOR MOUNTING DRIVERS I never use gaskets for mounting drivers, but if for some reason your driver rebates aren't nice and smooth, you may need to add a gasket between the frame and cabinet. Cut suitable circles from thin polyurethane foam, the kind of thing we get every time we buy a new electronic gadget, glassware, or whatever we buy these days, even fruit from China, I've seen.
I hate spikes and I honestly don't think they do
much good, if any.
SEALING WIRE HOLES
I've had this question several times lately: How do you keep e.g. small midrange cabinets tight when you have to drill a hole for the wires? Easy, drill an e.g. 8 mm holes, pull the wires and fill the hole with e.g. silicone glue.
I read somewhere cotton towels were excellent for
making damping panels, so I bought twelve 70 x 140 cm heavy towels at
the local JYSK. For the frame I use standard 37 x 57 mm lath wood and
cut them on my table saw to the profile seen on the drawing.
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Preparing
for the adjustable feet. The bolt is fastened with epoxy glue. Fill a
syringe with epoxy and inject around nut.
