All New Metronomes.

[Irene Idler]

Once I get the new ones built and voiced, Dave and yourself are welcome to pop over for a comparison session.
Should be sorted early in the new year

We'll definitely take you up on that, and bring the OTL amp again. Might as well give it a good workout before it's replaced by Dave's latest project!

[pre65]

Steve, I have a pair of Fostex Fe167e drivers, and have found a 5ft (60") Metronome design to suit on this web site.

http://p10hifi.net/FH/images/metronome-207m-v1.gif


How does your design for a 6" driver version differ from that ?


Has anyone any comments on an FE167e Metronome ?

[Cressy Snr]

Steve, I have a pair of Fostex Fe167e drivers, and have found a 5ft (60") Metronome design to suit on this web site.

http://p10hifi.net/FH/images/metronome-207m-v1.gif


How does your design for a 6" driver version differ from that ?

The driver I am using has a Fs of 100Hz, whilst the FE167e has an Fs of 51Hz, therefore to tune below resonance, the cab for the FE167 needs to be taller. That cab linked to is in theory slightly too large but as Scott will tell you, it's close enough for jazz and US users who have built the FE167e Met report great sound.

The cab linked to is suitable for:
FE167e, FE207e and FF225WK. The 3" port air mass is adjusted to suit each driver by varying its length (FE167e requires a 3"port, 2" long.)

The cab will also work with the Pioneer B20FU20-51FW if the port diameter is increased to 4" x 2"

This thread http://www.diyaudio.com/forums/full-ran ... onome.html on DIYAudio has been going for ten years now, and is still quite active. Plenty of pics of other people's efforts.

And here's a company that has been building Metronomes in the USA, since 2009.
http://rhythmicraft.com/metronome.html
They also do a sub to complement the design
http://rhythmicraft.com/ava.html

[Scottmoose]

Tables of dimensions for Mets I quickly worked up that are lurking in their section of the Frugal-horn site: http://www.frugal-horn.com/metronome-table.html As far as I know, there have been at least a couple built with the old 167.

[pre65]

Thanks Scott,

That table confused me for a while as the brown dimensions are back to front, but I assume the "preferred" numbers are the way to go ?

[Scottmoose]

Should be. It's been a while since I did these, so I'm going by fallible memory, but Dave won't have listed it like that without reason.

[Cressy Snr]

A nice pair of Monacor, air core inductors are on their way from eBay. I have the caps for the crossovers already, So the speakers may be built over the Christmas break, if I can make enough time.
Having tested the bass/mid drivers earlier in our Ant's Mets, I know what to expect and it's gonna be good.

Not as daft as I look when it comes to speakers y' know

[Cressy Snr]

Inductors arrived yesterday from ebay seller Willy's hi-fi; nice set of 150W, air-core jobbies by Monacor.
Around eight quid apiece, so not cheap for what is a coil of wire around a bobbin, but power handling is what I went for in this particular design.

[pre65]

the speakers may be built over the Christmas break, if I can make enough time.

Have you started yet ?

When I come up the A1 later today I hope to hear a saw buzzing.

[Toppsy]

Inductors arrived yesterday from ebay seller Willy's hi-fi; nice set of 150W, air-core jobbies by Monacor.
Around eight quid apiece, so not cheap for what is a coil of wire around a bobbin, but power handling is what I went for in this particular design.

Steve,
Those Monacor inductors are simply wound around the plastic core and then held together with tape. The tape is the only thing keeping the windings tight and in place. I used to use them in my builds until I found that with time the heating of the coils with the current passing through them can cause the glue on the tape to fail and then the whole inductor becomes loose. This will affect performance but if buried in the speaker you may not be aware of this issue happening. Same reason I have stopped using Falcon air-core inductors. I only use both now for breadboard lash-ups when fine tuning the XO to the speakers. I have also found they can be up to 10% tolerance. At least with the Falcon Acoustics ones you can specify a tolerance value and Gerry will wind them to that tolerance value. I now only use Jantzen air-cores. These have tolerance of 3%. During the manufacturing process they are baked into a highly stable self supporting structure. The enamelled copper wire used is solderable and possesses a self-bonding topcoat, which bonds to the neighbouring wire.

[Cressy Snr]

Thanks Colin.
I'll bear that in mind for the future. Last thing you want is the crossover deteriorating faster than it would normally.
A bit of very careful drilling at the edge of the bobbin at 12, 3, 6 and 9 o'clock and the judicious application of some small
cable ties, might come in handy with these inductors then.

[Scottmoose]

It's not about them deteriorating Steve. The loose windings under the tape can vibrate as a matter of course, which is the last thing you want, especially if you're going to be putting them into a fairly unfriendly environment (i.e. a speaker enclosure). Some people dip inductors into a pot of varnish (or melted wax) to try to seal them into a solid block & reduce some of the effects -even if they're already fused together via xyz method. Solen, ERSE, North Creek (latter now closed down) & others all have the laminations fused, plus cable-ties. The named ones tend to specialise in heavy-gauge windings, so it's a sensible move on their part to add some structural strength.

One related thought: don't forget the DCR of the inductor affects the behavior of both the filter and acoustic load.

[Cressy Snr]

Cheers Scott,
Only this afternoon, me and our Ant were talking about potting crossover inductors. Ought to be a no-brainer really, but you don't often see it in your average production boxes.

[Nick]

Cheers Scott,
Only this afternoon, me and our Ant were talking about potting crossover inductors. Ought to be a no-brainer really, but you don't often see it in your average production boxes.

Dont forget the limit it will place on dissipation if they are potted.

[Paul Barker]

They put sand in transformer potting compound so the heat disperses. it would help but not aleviate overheating fully.