Altec 604 8G

[jackrinse]

Hi.
Can anyone please tell me if I have a problem?
My situation is that I have a pair of 604 8Gs with Xovers and my 620a cabinets are at the woodwork shop getting fixed up.
The chap I purchased the speakers from had to do a little "fix" on one of the woofers??
When I use my Voltmeter on both tweeters the reading is about 7.2.
When I use the meter on one woofer it is about 7.2
On the woofer that has been fixed it reads 6??:blink:
I really dont know what any of this means so advice would be gratefully received.
Many thanks
Gareth

[jackrinse]

I Cannot listen as I have no cabinets.
Also the woofer does not seem to move in and out silently, there seems to be a rubbing inside?????

[speakerdave]

I Cannot listen as I have no cabinets.
Also the woofer does not seem to move in and out silently, there seems to be a rubbing inside?????

You mean while pushing the cone by hand, or running VLF sine wave through it?

I don't know what the usual range of DCR is for the 604 8G woofer voice coil is, but that 6 ohms seems kind of low. That combined with the other symptom may mean that the voice coil is partially shorted.

What was the repair you mentioned? If it was to fix mechanical damage to the cone, it may be that the cone is now misshapen and is tweaked off center or canted out of the plane it should be in. It may be there is a recone in your future.

[jackrinse]

Hi and thanks for the response.

The "fix" was done as there was a nasty interference noise that would come in when played loud.
The chap who I bought the speakers from is a good guy and very knowledgable but is now out of the country so I am posting here to get some info as I am a little distressed.
He told me that the edge of the cone had colapsed and that he had fixed it??
I did not worry as I had faith in him but when testing last night I noticed these problems.


.
You mean while pushing the cone by hand, or running VLF sine wave through it?

I don't know what the usual range of DCR is for the 604 8G woofer voice coil is, but that 6 ohms seems kind of low. That combined with the other symptom may mean that the voice coil is partially shorted.

What was the repair you mentioned? If it was to fix mechanical damage to the cone, it may be that the cone is now misshapen and is tweaked off center or canted out of the plane it should be in. It may be there is a recone in your future.

[speakerdave]

Still not sure exactly what you mean, but if the surround was pooched up in one spot because of cone sag or the edge of the cone as been displaced by slight but long term asymmetrical pressure (two possibilities which occur to me based on your description) the cone may have been canted so that the voice coil is not positioned correctly and is not traveling exactly axially. I'm not a reconer, but I would think it is very difficult to correct something like that because the clearances in the voice coil gap are so tight. If either of these guesses are what actually happened, the woofer probably should have been reconed, and at the least the "repair" should have been guaranteed, in my opinion, unless you were fully apprised of the situation and of the risk of the fix not lasting, and agreed to take on the risk in exchange for a signficant break on the price. In other words, that driver should have been guaranteed or priced as needing to be reconed except in the uncertain event the "fix" really worked.

[jackrinse]

The speakers were purchased as a working pair with no prior knowledge of problems.
I don't think the seller would have had any clue that there was a problem with them as they were in storage.
I only hope that he can fix it properly for me.

Would the coil being off axis give a reading less than 7.2 when measured?
6.1 for example????

[speakerdave]

Not of itself, but I would guess the resultant rubbing might scrape the insulation off some of the turns and short them together.

I thought you said he told you the edge of the cone had collapsed and he had fixed it.

[jackrinse]

That is what he told me?

TO explain the problem again as I think I may have confused this with my poor description.

Firstly when I push, by hand, the cone of the good driver in and out there is no noise and if I tap the cone there is a good drummy sound.

When I push the cone of the bad speaker there is a sound of rubbing/scraping and when I tap the cone the sound is not so drummy.

Also the multimeter reading are off as described.

[jackrinse]

Also if I push the cone of the bad speaker in and out re positioning my fingers at differing intervals around the circumfrance the noise can increase/decrease.
I think this leans towards things not being on axis or perhaps something somewhere is oval and not round??????

[speakerdave]

Has that speaker been used since seller "fixed" it?

[jackrinse]

No

I was going to test it today but only after I collect the xovers from a friend who was servicing them for me

[speakerdave]

The low resistance in the voice coil suggests that the woofer has been played enough while rubbing to partially short it out, so trying to adjust the cone so it will not rub (if that's what the "fix" was) is no fix at all. It should have been reconed, and still needs to be reconed, looks like.

[jackrinse]

I think this sounds most likely Dave.

Thanks

Gareth

[speakerdave]

Yeah, I'm sorry to see it turn out that way. Maybe you can get in touch with the guy and come to some kind of settlement.

Meanwhile, I'm not sure what your resources are down under for Altec recone kits, but Great Plains Audio in OK is making parts to factory spec, and they may have a dealer there, or they may be willing to sell a kit you can take to your reconer.

I listened to 604-8G's for a long time, until I got into this JBL blue-faced monitor scene, and I enjoyed them a great deal. I never tried mine with SET tube amps, but I often used moderately powered push pull tube amps. They always were listenable, and the midrange consistently passed the emotion test. And I also found that when powered with 200 watts of McIntosh autoformer solid state they had another thing they did that was a lot of fun.

I think you'll find it worthwhile getting them fixed and enjoying them despite this rough start.

Regards,

David

[Chas]

I am no expert, but based on my experience, it sounds like the voice coil got partially cooked and one, or a few, windings got fused to one another. Sounds like a call to GPA is in order.:(

[scott fitlin]

OR during play, at high enough volume, with a healthy bass note or drum whack, the woofers voice coil jumped the gap, it's audibly noticeable as a popping sound. And the coil usually doesnt sit back at the proper point inside the gap, the rubbing you hear is the voice coil rubbing in the gap. Playing music through this speaker, you will hear noise, and eventually, or maybe soon, it WILL break.

Now Altec woofers had very compliant suspensions, and low mass, underhung, voice coils and when these types of drivers were in heavy use, music recordings were much different. High compliance suspension woofers also didn't always need excessive drive levels to cause them to do this, REALLY DEEP LF, at low to moderate volumes could cause this too.

It needs to be reconed, and IF you really love the sound of these speakers, contact Bill at Great Plains Audio, in Oklahoma City, his prices are reasonable, and his workmanship is excellent.

I grew up on Altec, loved the sound of them, and I also toasted more than my fair share of Altecs, and i'm quite familiar with the popping sound of both excessive LF energy, and excessive drive levels.

Oh, and BTW, the proper DCR reading for this model Altec is the 7.2 value!

[jackrinse]

Thanks for the advice.

I have had a friend with suitable cabinets listening to the drivers for me.
At first he said he could hear no problems so we thought they were playing ok.
I then thought I could hear some slight destortion, but was unsure.
I left the speaker in the cabs and the following day my friend called me over to listen to a certain track.

The destortion was very bad at low levels.

I am waiting now for the seller to return to Australia to help me with the fix.







OR during play, at high enough volume, with a healthy bass note or drum whack, the woofers voice coil jumped the gap, it's audibly noticeable as a popping sound. And the coil usually doesnt sit back at the proper point inside the gap, the rubbing you hear is the voice coil rubbing in the gap. Playing music through this speaker, you will hear noise, and eventually, or maybe soon, it WILL break.

Now Altec woofers had very compliant suspensions, and low mass, underhung, voice coils and when these types of drivers were in heavy use, music recordings were much different. High compliance suspension woofers also didn't always need excessive drive levels to cause them to do this, REALLY DEEP LF, at low to moderate volumes could cause this too.

It needs to be reconed, and IF you really love the sound of these speakers, contact Bill at Great Plains Audio, in Oklahoma City, his prices are reasonable, and his workmanship is excellent.

I grew up on Altec, loved the sound of them, and I also toasted more than my fair share of Altecs, and i'm quite familiar with the popping sound of both excessive LF energy, and excessive drive levels.

Oh, and BTW, the proper DCR reading for this model Altec is the 7.2 value!