Frankenstein 18 watt combo

[bob p]

Juan, excellent post on manufacturing techniques.

[J M Fahey]

Thanks

There is still other telltale manufacturing detail which screams ASIA!!!!.

Old school magnet plate manufacturing was making the one furthest from frame in 2 separate pieces, later joined together: a flat but thick (1/4" - 5/16" . 3/8" - up to 1/2" in large subwoofers) disk punched out of a large steel plate which shows the typical "torn metal edge" I described above, plus a center pole piece, a cylindrical solid bar of iron, lathe cut from a long bar .
Sometimes they drill or turn a center hole for "breathing" but it is not essential.

Both parts,backplate and polepiece MUST be firmly joined together,
Typically by turning a "tit" in the polepiece which tightly fits a turned or punched hole in the back plate or sometimes a threaded hole is cut in the polepiece and a bolt fixes it to the backplate, in which case its head should be visible.

This is the way American (North and South, including mine are made) , European, British.

Now some Asian monster manufacturer makes them another way, which saves turning time, fixing, etc. and in theory is better because there are no seams: they heat red hot a ball or indeterminate shape piece of iron until itīs soft as, say, modeling clay or bread dough (which means **very very** hot) and forge it into the desired shape, base disk and center pole are all a single piece.

Although Asians can make them the old way, punching and turning, I bet these single piece backplates must be Ļ**real** cheap, an irresistible price, because everybody there uses them and I am starting to see them in (every day less) American speakers.

here is a hybrid/Mestizo Eminence speaker.

I *guess* Eminence had a ton of frame+frontplate made and unused collecting dust, and they finished them using an undersized ceramic magnet and an asian hot forged backplate + polepiece.

*This* is the "Asian Passport" telltale sign: notice the backplate edge is not straight and torn edges but rounded, ... like when you flatten soft dought with a roller or between your hands.

Here they are side by side (ok, top Asian-bottom American) so itīs easy to compare.



Another telltale difference is that "machined" plates look "rough" , best case they show circular toolmarks made by a lathe cutting tool, while hot stamped plates have a characteristic "satin" "sandblasted" smooth surface.

FWIW Chinese Celestions have these molded plates while British made ones look machined and show some kind of rough "scar" showing has polepiece was mechanically joined to backplate.

I am starting to see Scumback, WGS, Jupiter, a few Eminence and Weber speakers with Asian hot stamped plates, so I suspect they are no longer "Made in America" but "assembled in America" .
At least Eminence says so in the labels or brochures; ...... but the others ....... not so much

EDIT: the Eminence speaker I showed above is a "factory buyout" (reject/seconds? ..... like the bargain Warmoth necks?) being offered for only $10 to $12 each, depending on quantity.
They were sold "by a Large manufacturer".
*Maybe* this salad-of-parts did not perform as expected.
https://www.parts-express.com/eminen...4-ohm--299-402

That said, it looks perfect for low cost experiments, look a the user gallery shown under it, a cool combo housed in a wine box, a "line array Champ"with an original chassis mounted in a 4 speaker column, etc.

At $10 for a finished working Guitar Speaker *I* would buy a few and pair them with simple battery powered amps, or a mini PA with two 4x6" speaker columns, etc. (I bet they do not need horns or tweeters to give reasonable highs, and worst case I can add a Piezo on top)

Oh, my excuses for the thread derailing, the idea was to show some typical physical traits which tell Asian speakers from all others.

[Chuck H]

So... You've done some of this then?

[olddawg]

So... I plugged them into the tube amp. Meh... usable. I compared them to a real Eminence I had in a open back combo. The old USA speaker is more efficient and has more high end.

[J M Fahey]

So... You've done some of this then?

FWIW just yesterday I brought home a needed and very heavy iron part for the new magnetizer Iīm making (my third so far) .
Still a lot of precision turned (and heavy) parts are missing, but after diddling around and procrastinating for a couple years, now I NEED it.

Lost a lot of sales to those newfangled DVD player size (and weight) 250/350/700/900/1000W Class D amps.

Problem is *electronics* was miniaturized ... but speakers were not.

My current 10" stands 120W RMS but kids want a 2 x 10" to stand 250/350/500W or 4 x 10" standing 600/700/900W RMS , today out of reach for me.

But for the new , larger and heavier Ceramic, (I wonīt fall in the Neo trap), I need a double size/power Magnetizer, so .....

So yes, I have tried and done many things, but it is never enough, I must keep up to date or new Technologies (or plain fashion) will crush me.

Oh well, at least Life is NOT boring

[Enzo]

What is the neo trap? On the face of it, they appear to make smaller lighter magnets making the same field strength. What are the downsides?

[olddawg]

Had a little time to work on this. Pulled the perfectly working 100 watt DSP chassis and threw it on the junk pile with the others. I cut, planed and painted a piece of 1" thick pine to fill the hole from the old chassis in front. I was even able to use the old chassis mounting holes in front, the old washers, and some black wood screws to mount it. It's a perfectly usable 2x12" 4 or 16 ohm cab now. But... I'm going to make the cutout in the top back for this 20 watt VHT 2 x EL84 amp that hangs from 2 bolts. The existing holes will go away with the cutout and I'll reuse the old washers with new, thicker black bolts to hang the chassis. I like repurposing stuff off CL like this. There are even inserts for casters on the bottom of this cab.

[olddawg]

I'll cut the tolex with a sharp box cutter and try to peel back enough to glue back down over the edges of the cut. I've done it before with a heat gun. If that doesn't work.. I'll paint the exposed edge black and then run a strip of black Gorilla tape around it. I could actually still make this a 36 watt if I wanted too. I have a 36 watt chassis with the correct transformers and the front panel is exactly the same.

[olddawg]

So I (almost) finished this beast. It plays and plays well... but it's a loud f@@ker for 20 watts. I have a $12 100watt L Pad on order to mount on the back panel when I put it on. I just cut the control opening with a saber saw and a 1x1 as a fence and a half inch hole drilled at each corner... then painted the exposed wood inside edge with black spray paint. Not perfect but from 5' away no one notices. Not a bad project for $150 worth of Craig's List stuff... A little on the heavy side but it does have TWO 12".

[olddawg]

Ready to put the back panel on and a little flat black paint. 100 watt L Pad installed to take the edge off. Works great if you don't crush it. Not bad for a throw together. A little heavy... but it does have two 12" and the tube chassis is heavier than the old SS chassis. Very usable. Takes pedals well. I may make the attenuator foot switchable in the future.

[olddawg]

Done for now. I didn't bother with a back panel extension speaker jack or a line out jack (although there is a voltage divider type line out on the chassis with an rca jack). Figure if I put in a footswitchable relay for the attenuator I'll do it then. And maybe a whisper fan. May even use it at my gig tomorrow. Oh.. and I used my luggage scale on the handle. 56lbs. Argh. But my V22 is 43lbs and only has one speaker. I guess it isn't awful since a Fender Twin Reverb is 72lbs, lol. Still a bit weighty for this old fart.

[olddawg]

So I brought this to our rehearsal space for my other band member to play through since he was using an awful sounding (to me anyway) Acoustic (new Chinese) combo that happened to be there. Other than the lack of having a reverb he was blown away. It really liked his EMGs. Had the attenuator set at more than half and it didn’t even get warm for those considering using one.

[olddawg]

Yeah ... this guy uses a JCM 2000 half stack with a rack Marshall Pre amp (go figure?) and some sort of high end rack processor with a bunch of programmable stomp pads on stage. Surprised him that going straight into a junk parts combo amp with no name speakers sounded just as good if not better at club volumes. I told him it was "optimized" for EMGs .

[J M Fahey]

What is the neo trap? On the face of it, they appear to make smaller lighter magnets making the same field strength. What are the downsides?

Yes, the more strength in smaller size/weight promise is true

Problem (for us) is this:

1) speaker voice coils by themselves can not stand more than 15/20W ... period.
Easy to check if you connect a spare voice coil, sitting alone on the bench, to some power supply or a couple car batteries in series.
It will smoke and crack.

Yet they handle, say, 150W RMS in a speaker.

Amazing fact is, all that heat is transmitted to magnetic circuit, which then dissipates it into surrounding air.

You can easily notice that a ceramic + big iron disks weighing a few pounds is able to absorb WAY more heat than a puny "stack of dimes" sized NEO magnet, measured in ounces.

A second problem is that all magnets have a so called "Curie temperature", beyond which it fully demagnetizes ... forever.

Alnico is beyond 450C , Ceramic 600/700 C , while NEO: pltry 100 something C.

So they have the triple threat of being low mass so they heat up quick, small surface so they dissipate heat poorly, (noticed most have finned heat sinks attached?) and will easily self demagnetize.

In my book, a ticking time bomb ... plus nowadays they are still more expensive.

And they are notoriously hard to magnetize, standard magnetizers such as my own canīt, they require a very high intensity current pulse (thousands of Amperes) , very brief.

[bob p]

thanks for posting that. great information that i had not thought about.