The Metronome

Once you go paper, you'll never go back. :D

I gave my cardboard Metronomes to my kids and they want real cabinets built so I did the math on the cutting angles and found, lo and behold, that the dihedral angle, the one where the two sides come together, is 90.18 degrees. In the end, the sloping sides don't matter all that much. I doubt my cuts are accurate enough to get closer to 90 than that anyway. This is for the FE108 Sigma version. I plugged in the numbers for some of the other boxes and none were even 91 degrees. I can attach the calculation spreadsheet if someone wants to use it but I don't have it here at home.

And how do they sound?? I still find mine to be very nice for vocals, but they don't rock. The bass has opened up some as the driver has broken in. Maybe it needs BSC to smooth out the response as there is a definite hole in it somewhere. I'm using drivers where the TS parms are unknown, so I can't even guess where to tune them (if I even knew how.)

In the meantime I've been enjoying my 2 ways.
 
Mine calculates the dihedral angle, the intersection of the 2 sloping planes of the metronome. Given the height of the speakers and small slope of each panel, the dihedral angle is only slightly over 90 degrees. If you cut these square you'd be fine. A once over with a little sandpaper would be all that's needed to correct the difference. It had bothered me when I pictured them in my head that this angle couldn't be completely square but I didn't know by how much. My calculation is based on this webpage:

Dihedral Angle

The Metronome is a pyramid with the top cut off with a rectangular base rather than a square as described.

I'll post it tomorrow.
 
Hi.
I want to build the metronome for my friend. I will use Fostex FE168ESigma. This drivers are very good in my BIB, but his wife don't want so big speakers. How do you think, guys, is there need some BSC network for my project, or this will work fine without it?
 
frugal-phile™
Joined 2001
Paid Member
zacster said:
Once you go paper, you'll never go back. :D

And how do they sound??

Well i don't know about that. I got the pair finished, and frankly they sound not very good... if you grab the cabinet while something is playing they feel like a vibrator. That could go a long ways to explaining the sonics.

As an excerise to get a feel for the shape thay are a success thou.

dave
 
planet10 said:


Well i don't know about that. I got the pair finished, and frankly they sound not very good... if you grab the cabinet while something is playing they feel like a vibrator. That could go a long ways to explaining the sonics.


dave


that could also go a long ways to assuring some WAF -

'honey - the little 3incher is OK, but how about that 8" you promised me? '
 
planet10 said:


Well i don't know about that. I got the pair finished, and frankly they sound not very good... if you grab the cabinet while something is playing they feel like a vibrator. That could go a long ways to explaining the sonics.

As an excerise to get a feel for the shape thay are a success thou.

dave


I've decided that mine aren't very good either for anything below 500hz, even with a sub. I'm still looking to build the real cabinets.
 
planet10 said:


When we get around to real cabs they will probably be for bipole FE127.

dave

I'm still debating in my mind which drivers to build these with. Having never heard any Fostex drivers I don't even know where to begin. I wish I knew more about these ratshack drivers I'm using. The TS parms aren't published anywhere I can find and I suspect they aren't very good anyway.

The FE108 sigmas are twice the price of the 126 and I don't see anybody raving about them, although they seem to be better constructed. But the 126 in a Metronome needs a taller box, which I'm trying to avoid. The alternative box is the Frugalhorn which takes either driver in the same size box. If I'm not satisfied with the Metronome I'd build the Frugal box, or if they are available buy the flat pack. Are they ready for sale???? Are the bigger Fostex drivers better? or worse? Bigger isn't always better.

As for dipoles, I hadn't really considered them. They're for my kids and I don't think they need anything that fancy.

If it matters, I'll be driving these speakers with either a push-pull 6B4G amp, or a Charlize T amp, depending on where they are being used in the house. Both put out 10wpc or so.

And should I buy the raw 126 or 127 or should I get your modded ones? Silly question I'm sure. Since these are for my kids maybe I should just go cheap. But I'm also likely to show them off at the next NY Audio Rave, and they're a critical bunch.

Meanwhile, I'm listening to my Proac clones, which go down to 28hz and can be felt in the room. I'm not expecting that kind of response from the Fostex drivers in any box.
 
frugal-phile™
Joined 2001
Paid Member
zacster said:
Having never heard any Fostex drivers I don't even know where to begin. I wish I knew more about these ratshack drivers I'm using.

Some of the RS drivers were very good value... with the exception of the 1354, you won't find any that aren't bettered overall by a Fostex.

The FE108 sigmas are twice the price of the 126 and I don't see anybody raving about them, although they seem to be better constructed. Are the bigger Fostex drivers better? or worse? Bigger isn't always better.

The 108 is quite a bit solider build. A stock 126 will do better in the bass and is more extended on the top. The 108 wins in the mids and doesn't have the rough edges a sock 126 does.

The bigger drivers are more efficient, go lower and because they move more air can be more dynamic. They give up top end, smoothness, and midrange finese to do it. I personally think the 126 & 127 are the sweet spot and if i need more, i think bipole.

But the 126 in a Metronome needs a taller box, which I'm trying to avoid. The alternative box is the Frugalhorn which takes either driver in the same size box. If I'm not satisfied with the Metronome I'd build the Frugal box, or if they are available buy the flat pack. Are they ready for sale????

It is only 8" taller.

If you want short then build Mileva (originally conceived as a folded Metronome). It would need to be tweaked somewhat for FE126. FE127 is better suited.

As for dipoles, I hadn't really considered them. They're for my kids and I don't think they need anything that fancy.

Bipoles, not dipoles. These give bigger sound. No need for any BSC. And double the cone area with no combing.

If it matters, I'll be driving these speakers with either a push-pull 6B4G amp, or a Charlize T amp, depending on where they are being used in the house.

Yummm... both should be good, but if i was picking one to take home i'd take the 6BG4. For the kids on the other hand, the Charlize might be more practical.

And should I buy the raw 126 or 127 or should I get your modded ones? Silly question I'm sure.

Me biased? Of course i think you should buy mine :) I think everyone should (just not all at once please).

Joking aside, the modifications decidely take the rough edges off the drivers, and almost completely close the gap where the FE108 has an edge over stock FE12x drivers.

Meanwhile, I'm listening to my Proac clones, which go down to 28hz and can be felt in the room. I'm not expecting that kind of response from the Fostex drivers in any box.

The little Fostexs won't produce that kind of bass, but i wouldn't be surprised if you find they do some things that your Proac clones don't (be warned, you might start thinking small FR with bass augmentaion :)). The larger ones (in a big enuff box) will challenge the clones in the bass.

dave
 
Compared to the cost of amps that his post suggests he already has operating (or on a work in progress list), the price of drivers isn't that great .


I'd say build at least 2 different designs - starting with the Mileva. It's a vastly simpler build than any of the horns, "Spawn" family or Metronomes (i.e, it's all right angled cuts, with the exception of the angled internal panel - and even that could be faked)

While she doesn't deliver the last little bit of performance from the driver such as Ron Clark's A126 (which is highly tuned to a specific driver - just ask Ron about that :angel: ), Mileva is very easy to love.

She sounds great (better for me on tubes than Class A S/S), has a stealthy / high WAF form factor that all of the noted "higher" performance designs lack, and models as more tolerant to driver selection. Mine were built with FE127.

As to which driver, at the risk of shameless promotion :cannotbe: * the value added in terms of performance improvements of Planet10 treated drivers is well worth the price.


I recently installed a NIB pair of FF125K in Frugel Horns for initial assessment / break-in; it only took 10 seconds to remember how painful the first 200hrs or so can be. Fine tuning the CC and experimentation with driver treatment to follow.

*disclaimer - I've been working closely with Dave for a number of years as a second pair of ears and hands, and have had many opportunities to experience the development process of both driver selection/modifications, and enclosure design / fine tuning.
 
Hey guys, thanks for the detailed replies. I'll probably order something in the next few days, and I'm leaning towards your treated 126 as it seems to be the best of both.

I'll try the larger Metronome box, although the extra 8" puts it a little over the top in WAF, but I'll suffer. I suffer anyway. :eek: I've got all the angles calculated for the metronomes, and I'm going to have the panels cut for me based on the plans. I hadn't seen the Mileva plans. There are way too many options to look at.

The 6B4G amp is staying in the living room, the Charlize is for the kids.

I'll report back when I get them built, but don't hold your breath.

BTW, the closest I've been to Victoria is Saltspring Island, and that was just beautiful.
 
Canadian Speakers

Dave, I have been looking for some drivers to use in the Metro's. yesturday I came across these being sold. They are from Canada, but the guy selling them had no info on them so I thought I would try someone on DIY.
 

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