just got 604-8H off eBay- how check voice coils?

[kipduff]

Got these H's and put them in my open baffles- represented as original cones with recently replaced HF diaphrams from GPA. Ser #s 05947 and 04954. Left speaker lower db output, slight wiff of burning electrical, not sounding as good. Right speaker AWESOME. I believe I can hear scuffing when I move the left speaker cone by hand. Re both at 6.9 Ohms. Tried moving the cones while reading Ohms- but current generation made that impossible. Both cones have part number (?) "239792" on their back sides in smudgy white paint. Surrounds have 4 ridges and sticky, shiny black dope. Cones have little dimples all over.

Want to get more definite diagnosis- looking for way to test. I have nice signal generator, Fluke 192 digital scope meter, and other equipment. Do a lot of DIY, career mechanic, high end remote control aircraft, build vacuum tube stereo equip from kits. I am well aware that sending the speaker(s) to GPA is an excellent option- and I may well wind up doing that. I'm so glad GPA is there. However, I am considering possibly doing the cone myself (if needed) for several reasons- among them is that I enjoy projects like this, learning, and it would expedite. Replacement options: of course GPA- also original if obtainable/reasonable. Also saw other options (Simply Speakers). I'm bumming because I tink I prefer the H's to my K's- and I wish I didn't have to mess with a good thing. Plan to build 612 or 620 Baltic birch cabinets for these.

[mah]

Check Ohms from each terminal to frame(bare metal) with the cone at the rubbing position. It should read 'infinity'. If you get a reading less than 6.9 ohms or less with the cone stationary, the VC is shorting to frame.

Others here may be able to tell you how to remove the cone, without damaging it, so you can repair/replace the voice-coil.

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Edit(post 15 minute time limit): Firstly, contact seller to negotiate return or partial refund to cover repair costs.

[Phil-G]

any chance the cone or magnet shifted during shipping? on the other hand if the voice coil has over heated a professional diagnosis by GPA would go a long way.

[Elitopus1]

The magnet might need to be recharged also. GPA can do that for free if they recone it. Or they can recharge the magnet without disturbing the existing cone

[Old Guy]

The burning smell is probably a giveaway along with the "scuffing". Overheated voice coils often go out of round, so they rub. The rubbing consumes energy and reduces the volume.

Dr. Mike thinks it needs a trip to GPA. Personally would send both in to make them match, and maybe get a magnet recharge while there.

If you want to learn speaker reconing practice on some cheap speakers. Messing up Altec cones is expensive.

[kipduff]

[QUOTE=mah;1975029]Check Ohms from each terminal to frame(bare metal) with the cone at the rubbing position. It should read 'infinity'. If you get a reading less than 6.9 ohms or less with the cone stationary, the VC is shorting to frame

I think you mean if I get reading less than infinity. Great idea- will do when I get home from work.

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The burning smell is probably a giveaway along with the "scuffing". Overheated voice coils often go out of round, so they rub. The rubbing consumes energy and reduces the volume.

Makes sense.....

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If you want to learn speaker reconing practice on some cheap speakers. Messing up Altec cones is expensive.

How much are cones approximately?

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Anybody have a rough idea what his job would cost? At GPA.

[bowtie427ss]

How much are cones approximately?

A little over a C-note(each), installed, plus shipping.

GPA re-cone service includes cleaning the gap and checking the alignment as well as re-gaussing if needed.

I strongly agree with Old Guy's sentiments about doing both to keep them "matched".

Keep all receipts as provenance, and the expense will pay you back at sale time.

[kipduff]

[QUOTE=bowtie427ss;1975048]A little over a C-note(each), installed, plus shipping.

GPA re-cone service includes cleaning the gap and checking the alignment as well as re-gaussing if needed.

That's not expensive at all.....

[Elitopus1]

Gpa's services are a great deal, considering what is included.

Shipping ends up being almost just as expensive. For me its right around 40$ to ship one driver, one way to GPA. And that doesn't include packing materials