The Metronome

[AmadeusMozart]

I did see some remarks on making a jig for the table saw.

Howver you can easier work with a skillsaw: make a jig for it. Find a piece of material that has a straight edge and glue that on a piece of mdf or ply or what ever you have (I like MDF since it makes it nice smooth cut which makes it easy to line up).

Afterwards you run the skillsaw against this glued on guide.

Next time when you need to cut you just put this exact on the edge where you want to cut, clamp and cut away.

See pictures (taken from the web)

[fastbike1]

Lots of folks post these guides as easy methods to make a circular saw jig, and they are. However, there is one caveat that is never mentioned. It is harder to come up with that initial straight edge than people might think.

One cannot count on factory edges from the box store or lumberyard anymore. I suspect that many people start with a board from the store and don't check it.

Originally Posted by AmadeusMozart

I did see some remarks on making a jig for the table saw.

Howver you can easier work with a skillsaw: make a jig for it. Find a piece of material that has a straight edge and glue that on a piece of mdf or ply or what ever you have (I like MDF since it makes it nice smooth cut which makes it easy to line up).

Afterwards you run the skillsaw against this glued on guide.

Next time when you need to cut you just put this exact on the edge where you want to cut, clamp and cut away.

See pictures (taken from the web)

[ghpicard]

Originally Posted by fastbike1

One cannot count on factory edges from the box store or lumberyard anymore. I suspect that many people start with a board from the store and don't check it.

+1

[AmadeusMozart]

Originally Posted by fastbike1

Lots of folks post these guides as easy methods to make a circular saw jig, and they are. However, there is one caveat that is never mentioned. It is harder to come up with that initial straight edge than people might think.

One cannot count on factory edges from the box store or lumberyard anymore. I suspect that many people start with a board from the store and don't check it.

How true. But not impossible to straighten it yourself. Just another skillset that is at risk of being lost by the power tools crowd.

[AmadeusMozart]

Originally Posted by Jim Shearer

I have built Mets withFE108eSigma, F120A, and FE167e. All are very nice and I think you would be pleased with any of them.

That said, the F120A is my favorite--smoothest, best high freq and good enough low freq that I don't feel the need for a subwoofer; however, this driver doesn't sound good with direct coupled SS amps--the high freqs just die; with tubes it makes sweet, sweet music.

The FE108eS has great mids & highs, but the lows are limited enough that I like to use a sub with it.

The FE167e plays louder & sounds bigger with more authoritative bass. It gives up a bit of sound quality in the mids & highs, but is over-all quite pleasing.

I ran MJK MathCAD models of the FF125wk Met using the dimensions for the FE127e. It does work, but can be improved with a little tweaking. AFAIK there is no single, absolute solution for cabinet dimensions--there is always some wiggle room. The dimensions I settled on look OK to me, but someone else may find a slightly better solution.

I decreased the internal volume a bit, increased the length of the port, and increased Zd by 2". Changing Zd resulted in a bit less ripple in the SPL plot, but leaving Zd at 20" works OK--the ripple is then about what it is in the Mets I have built. So you can choose between higher driver placement and a little less ripple in the response.

Plotted response is for enclosure dimensions:
L= 48"
So= 2 x 2"
Sl= 7 x 5"
Zd= 22"
port: D=2", L=3"

I bought the worksheets and downloaded MathCad(15) 30 day trial. After getting myself familiar with the software I did some modelling.

When taking into account the room response then some other figures will show a lesser dip around the 200 - 300 hz range. In that case I came up with the port being 1.5" dia and a length of 1.75" while at the same time relocating the driver to 28" (!!!) from the top. I suspect the floorbounce and otehr room reflections will be responsible for this different behaviour since the graph in an "ideal" environment has hardly changed.

[Corvus corax]

Well, I have cabinets built for my Faital 15 inch macro Metronomes, and they have been once again moved into my tiny listening room. They have been playing for about 4 weeks now, off and on (mostly on), and my Stereolab Tractrix horns arrived about 2 weeks ago, and were promptly attached to the pair of TAD 4002 drivers I've had laying around for a few years. I put a simple first order crossover on the woofers at 150Hz and a first order on the TADs that I settled on at about 1100 Hz. The huge 20 Ohm recommended series resistor for the TAD came in handy- in concert with a parallel 6 Ohm resistor, it brought the levels pretty well in line, but I'm working on my 18 Db high pass filter for the horns this weekend, as there is a dip in the response about 5-600Hz or so that needs to be addressed…

Overall, a really great sounding system for being so thrown together. The bass is more than powerful enough- I simply raised the base of the unfinished cabinet .75 inches from the floor to fiddle the response to my liking- the system signs off about 35Hz or so, but makes up for that with some of the fastest bass I have ever had in MY system. That, and the tremendous power handling makes for a system that can literally break windows with the kettle drum. I'm moving them to a larger room to make sure the system balance is good, then they are going to be finished in copper, and the height adjust mechanisms added to the horns, which are to be mounted on the sides of the cabinets.

I made my own resistors… The commercial units sound markedly inferior to about 14 feet of Nichrome V arranged in a hairpin bundle. The finished crossovers will mount to the back of the cabinets, wired completely with silk wrapped solid silver, which the Radian diaphragm equipped TAD seems to prefer over my commercial offerings. Haven't decided on my final caps- probably something beeswax and copper foil, though. There are a LOT to listen to…

Excuse the room… Getting ready to move things, and, you know, prototyping…

[Steve Cresswell]

Crazy.....
I just love 'em

[Corvus corax]

Whats strange about the whole setup is- the horns currently sound best when they are down low like that. I'm making the height adjustable on the mounts.

[AmadeusMozart]

Originally Posted by Corvus corax

Whats strange about the whole setup is- the horns currently sound best when they are down low like that. I'm making the height adjustable on the mounts.

I did "fudge" the port with Martin King's worksheets and there is a marked difference in reponse when the port is on the front or on the back. SO having it in the bottom is a good location (imho). When the port is on the front then raising the port up from the floor about 10" (from memory) and having the driver slightly below centre has best results when taking room response into account. But it just does not look the part with a port visible.

I am only able to work about an hour a day on them but they are coming along slowly but steadily. Bought some tiles this weekend and painted the edges (they are only glazed on the top).

One design decision I made was to "lean" them back about 5/16" at the top to minimise the risk of the enclosures leaning forwards due to the weight of the driver. Although it does not sound like a lot it is rather noticeable when positioned on the tiled kitchen floor and frankly I like the looks, especially considering that these will be placed close to the wall.

Wife never made remarks on the builds in the past but this time I got favourable feedback. Similarly daughter had complementary remarks on the shape. We'll wait until they are finished and have been run in for final feedback.

[AmadeusMozart]

Completed these yesterday and the drivers (FF125WK) have only a few hours on them but they compare very favourably to some Monitor Audio Studio 12 that I have. Very, very impressed by the results, it is missing out to the MA in the highs but for the rest I prefer the metronomes.

What is the best full range ~~ 5" driver - this design deserves the best driver that can be found.