604's are going to GPA and having New cabinet thoughts.

[cradeldorf]

I'm having transient nodes of thought on a new speaker cabinet design now. I wish I knew a thing about designing them. I kinda have an Idea but I'm not sure if it would be a good idea . I saw something on the web where a guy put an 18" altec into a tapered tube that went down into another larger tube it was called a mass loaded transmission line? each tube was 2 meters tall but he had a stack of other speakers too I was thinking of some kind of deflector above the speaker that would reflect the highs out horizontally since the horn would be pointing skyward. He said the bass was capable of reaching 5 hz. what are your thoughts on this Idea?

[Altec Best]

Bad Idea !!! You really don't want your sound bouncing of things it's called "Reflections" it will sound like an echo chamber, You should stick to a more published design for the 604 ie: 620A,B,Stonehenge III,the Stonehenge has a smaller footprint to so would be a good choice.;)

[cradeldorf]

Bad Idea !!! You really don't want your sound bouncing of things it's called "Reflections" it will sound like an echo chamber, You should stick to a more published design for the 604 ie: 620A,B,Stonehenge III,the Stonehenge has a smaller footprint to so would be a good choice.;)
Thanks Altec Best, I guess what I was thinking was that I would like a large volume cab without it taking up a lot of room and using a sonotube tapped horn setup would kinda help achieve this.
Bass isn't really something that reflects is it, your mainly talking about the horns...right? :confused:

[stereo]

Good evening

I have my 604 8g's in smaller cabnets, bi amped with 225 Mac amps on the high end and an additonal 515 passively crossed over in the same enclosure which makes for very special sound. I also took the 604 to a machine shop and had the altec driver removed (not an easy task) and epoxied a TAD 1" driver in place of the Altec. Very nice and sweet sounding speaker. I agree the smaller enclosure such as 6 cu ft for a single 604 works best. Good luck they are still the best sounding speakers in a small room.

Stereo

[speakerdave]

Going to GPA? Why?

Unless something has happened to damage the woofer cones or burn out the woofer voice coils, there is no reason to send them to GPA. You do not want to jettison good original woofer cone kits in favor of GPA replacements unless there is something seriously wrong; that is, not just because they are old.

If someone has convinced you the woofer magnets should be recharged, that is bogus. According to the best advice we've received here, from Greg Timbers, Alnico magnets with underhung voice coils, such as the 604, are not at risk for being demagnetized by being driven hard because underhung voice coils do not do that.

If someone has convinced you you need new diaphragms for the high frequency horn because they are old it might be true, but you should wait until you hear a problem with the sound. If the speakers have not been driven hard a lot, the the HF diaphragms are probably just fine. The lightweight diaphragms fitted to the 604's are no longer made; if you have them and they work you want to keep using them. Even if you need new diaphragms, you should replace them yourself or find someone to do it for you locally, to avoid shipping. You should minimize shipping, because it is never without risk.

Basically, if your initial description of these speakers is accurate, that they have been carefully used, just use them the way they are; they are perfectly fine.

Finally, if you are going to keep these speakers, use them in the cabinets they came in, at least for a while. The bass frequencies are probably not highly organized in them, but that can wait until you have had time to learn about cabinets and make a good choice. Based on your questions I would say you are almost completely in the dark about how speakers work; you therefore do not want to try anything experimental. The advice you have already received to not try anything outlandish is very good advice. If you can make a simple bass reflex cabinet following Altec's design and do it well enough that it works and looks good that will be a huge project all by itself, but it will have a KNOWN OUTCOME.

[Earl K]

Going to GPA? Why?

Unless something has happened to damage the woofer cones or burn out the woofer voice coils, there is no reason to send them to GPA. You do not want to jettison good original woofer cone kits in favor of GPA replacements unless there is something seriously wrong; that is, not just because they are old.

If someone has convinced you the woofer magnets should be recharged, that is bogus. According to the best advice we've received here, from Greg Timbers, Alnico magnets with underhung voice coils, such as the 604, are not at risk for being demagnetized by being driven hard because underhung voice coils do not do that.

- The OP is simply parrotting the conventional wisdom ( as offered ) from a couple different forums .

- I happen to agree with you that this collective thought process is worth challenging and also worthy of some close scrutiny .

- Having said that ; there's a real paradox at play here since there's a lot of anecdotal evidence showING that most old Altecs ( alnico magnets ) benefit from a recharge .
- So ( in light of GTs' discourse on the subject ) how come ?

- Take Altec Best ( John ) for instance ; he owns 3 pairs of 416-8Bs . Four of his 6 speakers measure out with low BL figures. And that high percentage seems to be pretty indicative of todays' defacto situation ( Altecs' underhung coils working in alnico assemblies ) .
- The lowish numbers imply/indicate that the magnets are partially discharged ( which is a more likely reason for those low numbers when compared to the other possiblity of Altec using voice-coils with insufficient windings ) .

- Is G.T. wrong ? Unlikely . One possible explanation ( which offers some coherence ) is that Altecs' QC at the time just didn't care about maintaining the correct BL figures .
- Another supporting explanation is that Altecs ( older & somewhat inferior ) magnetic circuit ( welded rolled tubes vs the cast magnetic return circuit ) was never adequate enough to take ( & hold ) a full charge .
- There's some evidence to support this conjecture ( including Panos recharge tribulations which are on record over at Hostboard ) .


FWIW, I agree with your assessment . I don't think its wise a be shipping (2) 30 lb units haphazardly across the country without exploring the very real consequences of "shipping gone wrong" .

<> cheers

[cradeldorf]

Going to GPA? Why?

Unless something has happened to damage the woofer cones or burn out the woofer voice coils, there is no reason to send them to GPA. You do not want to jettison good original woofer cone kits in favor of GPA replacements unless there is something seriously wrong; that is, not just because they are old.

If someone has convinced you the woofer magnets should be recharged, that is bogus. According to the best advice we've received here, from Greg Timbers, Alnico magnets with underhung voice coils, such as the 604, are not at risk for being demagnetized by being driven hard because underhung voice coils do not do that.

If someone has convinced you you need new diaphragms for the high frequency horn because they are old it might be true, but you should wait until you hear a problem with the sound. If the speakers have not been driven hard a lot, the the HF diaphragms are probably just fine. The lightweight diaphragms fitted to the 604's are no longer made; if you have them and they work you want to keep using them. Even if you need new diaphragms, you should replace them yourself or find someone to do it for you locally, to avoid shipping. You should minimize shipping, because it is never without risk.

Basically, if your initial description of these speakers is accurate, that they have been carefully used, just use them the way they are; they are perfectly fine.

Finally, if you are going to keep these speakers, use them in the cabinets they came in, at least for a while. The bass frequencies are probably not highly organized in them, but that can wait until you have had time to learn about cabinets and make a good choice. Based on your questions I would say you are almost completely in the dark about how speakers work; you therefore do not want to try anything experimental. The advice you have already received to not try anything outlandish is very good advice. If you can make a simple bass reflex cabinet following Altec's design and do it well enough that it works and looks good that will be a huge project all by itself, but it will have a KNOWN OUTCOME.Hi Dave, I have one 604 C and one 604 E, The C sounded great the E sounded horrible I switched the C network to the E speaker and it still sounded horrible I'm guessing that the E had a problem. Also I want both speakers to be equal in sound. Jeff Markwart claimed that having the speakers remagnitized made a noticeable difference on the pair he was testing. You are correct I am totally in the dark about speaker design but I read about it at least 3 hours a day because I want to understand....even though I'm thick as a plank when it comes to absorbing information. they are already at UPS cost me 75 bucks to ship them to GPA. I agree I think I'm gonna stick to my 7 cubic foot DBR cabs until I find someone elses design for a 604 cab that I really like.

[cradeldorf]

-
- Is G.T. wrong ? Unlikely . One possible explanation ( which offers some coherence ) is that Altecs' QC at the time just didn't care about maintaining the correct BL figures .
- Another supporting explanation is that Altecs ( older & somewhat inferior ) magnetic circuit ( welded rolled tubes vs the cast magnetic return circuit ) was never adequate enough to take ( & hold ) a full charge .
- There's some evidence to support this conjecture ( including Panos recharge tribulations which are on record over at Hostboard ) .


FWIW, I agree with your assessment . I don't think its wise a be shipping (2) 30 lb units haphazardly across the country without exploring the very real consequences of "shipping gone wrong" .

<> cheers
Who is G.T. ? and what does BL stand for? see I'm learning. :)

[cradeldorf]

FWIW, I agree with your assessment . I don't think its wise a be shipping (2) 30 lb units haphazardly across the country without exploring the very real consequences of "shipping gone wrong" .

<> cheers
I packed them with a piece of 3/4 plywood across the face and plenty of 1 inch pink foamboard surrounding the whole speaker. plus I got insurance on them not that that is gonna help one of these irreplaceable antiques gets destroyed.

[Altec Best]

I agree the smaller enclosure such as 6 cu ft for a single 604 works best.
One other simple cabinet that I should have mentioned is the 612, (6.5 cu.ft. I think) but needs to be lifted off the floor about a foot or so.My 604-8G's came in a set and they sound really good.But the 604's bass extension does benefit from a larger cab. ie; 620 etc...

Posted By Earl K
Take Altec Best ( John ) for instance ; he owns 3 pairs of 416-8Bs . Four of his 6 speakers measure out with low BL figures.

Agreed ! and was quite disappointing. So I have decided to send in the Weakest pair for re-charge so I will be able to provide some info on sending and recharging old Alnico drivers to GPA.I also agree with trying to save Original cones at all costs as Dave has suggested.My drivers are only going for Magnetic charging ! If they come back significantly stronger then I will send in the second pair for the same.

-
There's some evidence to support this conjecture ( including Panos recharge tribulations which are on record over at Hostboard ) .

This has already been discussed as noted at Altec User board.But one piece of information that is consistently left out is that the Alnico slug in Pano's 416's wouldn't take a charge period after 3 zapping's and was sent to a lab for testing to find out What,Where,WHY ??? And Bill just went ahead and replaced the slug's in his 416's Nothing stays the same WRT speaker Co's as we all know.Unfortunately !! Who knows if we will ever get an answer to that though.



I don't think its wise a be shipping (2) 30 lb units haphazardly across the country without exploring the very real consequences of "shipping gone wrong" .


Sometimes it is a necessary evil.What is essential is the packing !! Can be made (Bulletproof) to a degree to lessen any chance of a mishap from a Careless (UPS) delivery man.I will not use UPS anymore BTW.Strictly Fedex or USPS the last pair of 416's that I received I didn't appreciate the handling from my UPS guy.

I mean if we didn't ship none of us would be able to buy/own any Vintage speakers.

[cradeldorf]

I've noticed that a lot of speakers are up off the floor, and probably for good reason. Unfortunately the cabinets I have now would look like 2 old zenith tv's if I put legs on them. :D

I checked out the 612 I'm confused at some parts of the drawing and the 620 for that matter, in the picture with a slanted board looking thing in it ...are those just braces against the sides or are they a panel that bisect the entire box?

[Ducatista47]

Who is G.T. ? and what does BL stand for? see I'm learning. :)
G.T. is Greg Timbers, chief Engineer and designer at JBL for some years now. He is very, very good at these things; myself and many others here consider him to be at the top of his field. From Greg, posted in these forums:

Here's the Scoop

Ferrite magnets do not demagnitize with time or drive. They are affected by temperature but that is reversible. They will return to normal when they return to room temperature. Ferrite is basically a lousy magnet material for speakers but it is cheap and readily available. JBL has done a ton of things within the magnetic circuit to make the material behave in a more stable manner. At 100 degrees F, a Ferrite motor will be down about 1.5 dB in level which means the midband of the woofer will be lower by that much and there will be increased output around the system resonance. The TS parameters will be completely different - as though the BL was reduced by about 18%.

Alnico magnets, by their nature are easy to demagnitize with drive. They will not change with time and their dependence on temperature is really small - maybe 1% at 100 deg.F. Alnico stability and resistance to back EMF is really good. This is why they make the best sounding magnetic structures. Unfortunatelly, given a big enough pulse of magnetic energy, they will demagnitize by up to 3 dB. The sensitivity to demagging is dependent on the specifics of the magnetic circuit and the length of the coil providing the field. Underhung woofers (LE15 and such) midranges, tweeters and compression drivers do not have sufficient back EMF fields to push the operating point of the structure below the knee. They are essentially stable regardless of input signal. The short gap-long coil speakers are the ones that have a problem. A 2235 can take a hit of up to 3 dB if a big enough hit of current takes place. 1.5 dB to 2 dB is more common. The effect does not get better or worse with time, it solely depends on how much current is driven through the coil. The more current, the more field. Once the field is bigger than a certain number, some amount of demagnitizing occurs. It is perminent (until externally recharged) and will only increase if a larger sustained current hit occurs.

Therefore, if you have a qualifying alnico woofer and you have played it loudly you have some damagging. You can have the unit recharged and it will be fine until you play it again. Exceed the critical level and it will start happening. If you never do, it won't ever demag. Most of these designs trace back to the 50's and 60's where 15 - 30 watt tube amps were the rule. They didn't have the current capability to hurt anything. With the advent of big solid state amps, the current levels went up and the problems started to surface.



RE BL, try this non technical quote:

BL is simply the amount of force on the cone you get for a certain current through the voice coil. A higher Bl will make the driver play louder (but not necessarily cleaner) and it will also indirectly lower Qes and Qts.

Bl has to be viewed together with Re since it has the opposite effect. That is why the ratio Bl/sqrt(Re) is sometimes found in datasheets.

If you want to wade through all these terms (I never have), search "Speaker (whatever term)" on Google. Or wait for the knowledgeable many here to respond.

Clark

[speakerdave]

. . . . I have one 604 C and one 604 E . . . . .

I didn't know this. It may have been mentioned to you already somewhere, but they are strictly speaking not a match; although perhaps close enough for many people. If it were me, I would not do anything with them except use them the way they are until I had a match, by swapping or selling and buying. I think the values of the two are approximately equal, but to different submarkets. I have never heard either of these models; all of my extensive listening with the 604 has been with the 8G. Whatever the differences are, it is apparently enough for some to prefer one and some the other.

If the 604E sounds bad something is wrong with it, probably the HF, but you could isolate the problem by disconnecting one section and then the other (keeping the crossover in the circuit) and drive with moderate power.

[cradeldorf]

Just so you know what I'm working with. And I'm driving them with a Marantz 2216 16 watts per channel receiver.

[cradeldorf]

Don't laugh but I'm actually mulling over a modular concrete 612 cabinet.....I love working with concrete. :leaving:

[speakerdave]

What is the problem you are hearing with the E?

[cradeldorf]

What is the problem you are hearing with the E?
It just sounds way more quiet than the C at normal listening volume kinda like something shorted out would sound. at first I thought it was the hi Freq. but when I took the cover off and looked at the diaphragm it looked ok whether it was or not IDK? the wires running to it were fine and when I switched networks it still sounded kinda shorted out or something???

[speakerdave]

It just sounds way more quiet than the C at normal listening volume kinda like something shorted out would sound. at first I thought it was the hi Freq. but when I took the cover off and looked at the diaphragm it looked ok whether it was or not IDK? the wires running to it were fine and when I switched networks it still sounded kinda shorted out or something???

Try changing the position of the HF level control--that is, turn it. See if that changes the sound. If it does not the HF diaphragm is burnt out.

Sound shorted? If the HF is absent the sound will be much less loud, dull and subdued sounding.

If the sound is very faint and "scratchy" that is 1) a bad amp channel, or 2) the wires connected to that channel are in fact shorted together. Continued playing in condition 2 will lead to condition 1.

Did you throw a party to celebrate your new speakers and try to drive them with that amp at disco levels? Small amps overdriven put out more than their rated power in HF and VHF distortion products. That tends to blow tweeters.

Or, you may have found the reason the speakers were sold off cheap by the college. "Old and not worth fixing," someone said. Hah! I know it's hard to believe, but not everyone is as preoccupied with this old stuff as some people I could mention.

[cradeldorf]

Try changing the position of the HF level control--that is, turn it. See if that changes the sound. If it does not the HF diaphragm is burnt out.

Sound shorted? If the HF is absent the sound will be much less loud, dull and subdued sounding.

If the sound is very faint and "scratchy" that is 1) a bad amp channel, or 2) the wires connected to that channel are in fact shorted together. Continued playing in condition 2 will lead to condition 1.

Did you throw a party to celebrate your new speakers and try to drive them with that amp at disco levels? Small amps overdriven put out more than their rated power in HF and VHF distortion products. That tends to blow tweeters.

Or, you may have found the reason the speakers were sold off cheap by the college. "Old and not worth fixing," someone said. Hah! I know it's hard to believe, but not everyone is as preoccupied with this old stuff as some people I could mention.

I did turn the attenuator both ways and could hear a total difference when I did so it was doing something but turned way down where the highs are the brightest still sounded way lower quality and brightness from the "C" I have. Nope no disco partys I'm pretty sure I noticed it early on when I first got them and was powering them with a Optimus receiver. I just want a good close as could be matched pair of great sounding speakers after all who do I have to impress??? I live alone and I need a fun hobby.

[speakerdave]

Check your connection at the amp. It sounds like you might have a strand or two of one of the wires shorted over to the other connector/terminal. As I recall those receivers have screw terminals with no dividers.

[cradeldorf]

Check your connection at the amp. It sounds like you might have a strand or two of one of the wires shorted over to the other connector/terminal. As I recall those receivers have screw terminals with no dividers.
I'll check it but probably won't let you know if they were....I'll be too busy kicking myself in the ass. :blink: BTW They are spring loaded connectors.

[speakerdave]

. . . . BTW They are spring loaded connectors.

Oh, that's right. That makes it much less likely.

To eliminate the amp channel as the problem connect the E to the other channel using the wire you have going to the C.

If that sounds the same, then the problem is in the speaker, since you say you already tried the C crossover on the E.

[speakerdave]

I'll check it but probably won't let you know if they were....I'll be too busy kicking myself . . . .

You can just say, "Problem resolved with a little trouble shooting."

[cradeldorf]

Oh, that's right. That makes it much less likely.

To eliminate the amp channel as the problem connect the E to the other channel using the wire you have going to the C.

If that sounds the same, then the problem is in the speaker, since you say you already tried the C crossover on the E. I would try that if they weren't already on their way to Oklahoma. Besides I'm pretty sure I did that when they were hooked up to the optimus it didn't help. :o:

[cradeldorf]

You can just say, "Problem resolved with a little trouble shooting."
I'll keep that in mind...I got a feeling I'll be saying that a lot.

[Altec Best]

I would try that if they weren't already on their way to Oklahoma. Besides I'm pretty sure I did that when they were hooked up to the optimus it didn't help. :o:

I don't know if you told them to change the cones or not but if you did. I would call Bill and ask him to leave the cones if they can be fixed without having to remove them.Especially on the C variant as they don't make those cones anymore.And is worth a lot more with Original cones!:)

[cradeldorf]

I don't know if you told them to change the cones or not but if you did. I would call Bill and ask him to leave the cones if they can be fixed without having to remove them.Especially on the C variant as they don't make those cones anymore.And is worth a lot more with Original cones!:) Actually what I said was could you make them like new again..... I don't have long distance on my phone although I did use somebody else's phone today to contact them because I wasnt getting a response to my emails. Personally I want them to sound the best that they can, I really could care less about their value because to me they're priceless I'll never part with them. Hopefully when Bill see's them he'll use good judgment in only doing what they need done. : )

[junker]

So what was the outcome? I hate it when there is a good discussion with no conclusion or take-ways? Where the 604's re-coned and re-magnetized by Bill? And how did they turn out? Did you do anything about new cabinets? Thanks.

[Wagner]

So what was the outcome? I hate it when there is a good discussion with no conclusion or take-ways? Where the 604's re-coned and re-magnetized by Bill? And how did they turn out? Did you do anything about new cabinets? Thanks.
You and me both, BUT the thread is 5 years old and the OP hasn't been here in 3, so.............try a PM, you may get lucky

Just hope the guy's alright or hasn't expired; that's happening to me more and more often as of late, a lot more than I care for

[junker]

Yeah... maybe worth a shot. At any rate I post my impressions after having my 614A serviced by Bill @ GPA. One had a rubbing voice coil so both are getting replaced and magnetized.

Next project is hopefully his 604E alnico drivers is large cabinets (250-300L) that I think I'll port according to the Altec volume to port size graphs. Should be a nice project after I have these 16 ohm Flamencos finished. Thanks!