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Box tuning for Altec 604-D

currituckco

currituckco

Super Member
Hi all...

I inherited (read: bought) this Altec 604-D project from judgeschreber. He had two different projects (some big cabinets with a 3-way design, and the pair of Altecs) that he had decided to combine by putting the Altecs into the cabinets, which would require some modification of the baffles.

The baffles have numerous small holes that were apparently tuned to about 60hz. The Altecs have an Fs of about 50...not quite close enough it seems. Plus for stability's sake (Is wood glue strong enough to support those heavy Altecs? I don't want to find out), I think I want to just make new baffles altogether.

I'm new to all this, so I was wondering if someone could help me design the baffle. How high do I put the Altec? Where and how big of a port? What shape?

Anyway, judgeschreber measured the altecs and came up with these numbers:
DCR= 9.0
fS= 49.684
QMS= 5.878
QES= 0.219
QTS= 0.212
RES= 250.083
LE= 0.300
n = 0.517

He also estimated the box volume as 4.8 cubic feet.

Here's his thread about the cabinets:
http://audiokarma.org/forums/showthread.php?t=116686&page=2

And his thread about the Altecs:
http://www.audiokarma.org/forums/showthread.php?t=118158&highlight=604-d&page=2

And a pic of the cabs:

attachment.php


Thanks for any help.
 
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What's the Vas, and Xmax?

*EDIT* I'm gonna guess and say that the box might be a little on the small side if you want any decent low end performance.
 
Probably true, but these are what I got for now, and nothing bigger than these is on its way in, so I'd like to make some DIY work of these now with the possible future upgrade if I'm not happy with the low end (I could also always recone these with E cones too, which is supposed to improve low end.)
 
bowtie427ss said:
What are your long term plans for the 604's and what are your space limitations if building boxes is a possibility?
Click to expand...

Well, it all depends on housing situations. I hope one day to be able to build behemoth speaker cabs as my heart desires, but that is I'd say 2-5 years off, pending things like buying a house, getting married, moving to california, you know, little things like that. For now building giant cabs isn't really an option. So is the consensus that the Altecs are not going to sound good in these cabinets? Should I not bother? If I don't bother, it just means the Altecs will sit in a pile for probably 5 years before I sell them.

Either way I'm going to try them in these cabs. If they sound like **** they sound like ****. If that's the case, maybe then I'll look at the nightmare of trying to build new ones.
 
I'm actually skeptical of the 4.8 cubic feet measurement...if those in that link are 20 cu. ft, there's NO WAY those things are more than 4 times as big as the freaking WASHING MACHINES that I have sitting in my living room. Lemme scare up a measuring tape and see what I can calculate...
 
New baffle, driver near the top so the horn's up near ear level (it's beamy in the HF,) tunable port(s) near the bottom.

"D" T/S parameters are not available, and I certainly question the measured Fs, above, as all the others are down around 30 Hz.

Tune the boxes empirically using sinusoidal, a resistor, and a voltmeter.

[OH, and some port plugs and a calculator.... :yes: ]
 
Yikes, you just said like 8 things I didn't understand! How do I tune the boxes using sinusoidal (I don't know what that means) and a resistor/voltmeter?

The calculator is like the only thing I have. How would I make new measurements of the Fs? I believe judgeschreber used a program called fuzzmeasure on a mac...I too have a mac but noticed said program costs $150. Yikes!

Are T/S measurements available for "B" of "C"? I believe they might pretty similar, no? I know "E" would be different because of the different cone...

So this won't be easy no matter what. Who said life was easy? Easy is buying bose speakers and an ipod. Screw easy!
 
Sinusoidal = sine waves of varying frequencies. The signal generator may be your computer with software to do it, most likely downloadable for free online, or even a CD with sinusoidal test tones closely spaced in the low frequencies. I've also seen those downloadable as WAV files online.

One setup is shown here:

http://sound.westhost.com/lr-passive.htm#6.0

A similar is shown in Dickason Loudspeaker Design Cookbook.

I explained this in another thread here a couple of months ago.

To tune the box, you measure the driver impedance at various frequencies in the region of interest. From those readings, you can calculate the tuning.

Another option is Woofer Tester 3 from Parts Express.

*****

Box modeling uses the T/S parameters to prescribe a tuning according to the variables you enter. Download free WinISD to see how that works. The earliest 604 in the database is "E". Others may be available from other sources. GPA should at least be able to tell you the Fs of "D".

I'm suggesting you avoid all of that, unless you can come up with the correct T/S parameters. Just build the box with variable tuning, and measure the result(s). That means you're going to have to set up to measure, learn how to do it, and what it means.

Buy the book and read up.... :yes:
 
GPA = Great Plains Audio.

If they have the T/S parameters, see if you can get them for posting here.

"D" was the highest volume sold version, right?

If so, I can't believe nobody knows poo about them.... :dunno:
 
No I think the D was actually a rarer version because it coincided with the 605. I found a description last night, let's see if i can pull it up...

Here:
http://recforums.prosoundweb.com/index.php/m/34789/0/
Altec 604D (looked just like 604C)
HF horn: 90h40v
X-over: 1600 Hz
Power: 35 watts, 50 peak
Impedance: 16 ohms
Weight: 40 lb.
Magnet: Alnico
Response: 30Hz - 22kHz
Free Air Resonance:
Frame: green hammer-tone
Cone: all paper cone
comment: 604D was in the 1957 catalog and was not superceded by the 605 until 1959
after that 604Ds were built one-off for special customers i.e. recording studios

Model 604D
Free air resonance: no greater than 40 Hz
Cone: paper w/ viscous compliance damping and annular spider

and here:

http://www.ominous-valve.com/altec.html
604D Late 50s/Early 60s Not many made, 605 was primary. N-1500 xover, 8/16 ohms

These are of course not gospel from on high, but given the dearth of info on these guys I'm inclined to believe that not many were made. However nowhere I've looked has anyone been able to describe any difference between a "C" and a "D". Anyone?

I'm emailing GPA (I figured it out right before seeing you'd already responded) to see if they have the T/S of the D (or C?)

On another note, how might these work in 620 cabinets? Or if I was to build from scratch, would a copy of the 620s be good? They seem to be about 9 ft^3...or what about the 606 corner cabinet?
 
New baffle, driver near the top so the horn's up near ear level (it's beamy in the HF,) tunable port(s) near the bottom.
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Fully agree here.

It sounds like the best option for you would be to work with what you have for now, consider focusing on the crossover and a good solid baffle putting the driver at optimum height.

When the opportunity comes along in the future, you can then decide the best box option to exploit the best LFE from them.

With 604's the midrange "magic" and superior point source imaging are going to far outweigh the LF shortcomings. Midrange will likely improve marginally in a bigger box, but what the 604 does best, it can do in nearly any size box.

A good dividing network, and positioning such that you're listening within a few degrees of "on axis" are probably the two most important criteria. Once you experience them in the aforementioned state, they'll likely be with you for the rest of your listening days.
 
"D" was the highest volume sold version, right?

If so, I can't believe nobody knows poo about them....
Click to expand...
I think our own Dave Wojo probably knows more about these than the rest of us put together.:yes:

I seem to remember something about differences in dampers, but i just don't have enough info to comment intelligently or conclusively.

For whatever reason 604D seems the least favored of all the duplexes, but it's built on the same frame and motor structure as the bulk of 604's and can be rebuilt as a 604E or 604-8G(early style with annular phase plug).

The 605 is the one that's really "different", it has smaller/shorter magnets and motors which give it the advantage of having the closest phase relationship between the HF and LF at the cost of a few db sensitivity.
 
bowtie427ss said:
For whatever reason 604D seems the least favored of all the duplexes, but it's built on the same frame and motor structure as the bulk of 604's and can be rebuilt as a 604E or 604-8G(early style with annular phase plug).

The 605 is the one that's really "different", it has smaller/shorter magnets and motors which give it the advantage of having the closest phase relationship between the HF and LF at the cost of a few db sensitivity.
Click to expand...

Hmm, I haven't noticed that - are you sure it's just not that there are fewer of them so fewer people have/discuss them? I honestly have no idea, I'm fairly new to this hobby and have no sense of what's out there, how frequently stuff turns up, etc...I much more versed in that way in psychedelic records from the 60s-70s ;) But from what I've read the "D"s are almost identical to the "C"s, and that the 605's were the ones much maligned at least at the time they came out. People now, including some here on AK, certainly enjoy their 605s. I also have read that 605's don't like being in cabinets designed for 604's, which may have been what people did with them in the early 60s when they came out. This is all completely uneducated speculation based on reading possibly slightly more educated speculation on the web, so please don't take any of my hearsay as gospel.

As for crossovers, I have all (or at least most) of the components for the Jeff Markwart 604 crossovers with the mid-eq...those came with the sale of the project, which was a bonus incentive for me to take the plunge.

So how would I go about making a tunable port? Do you guys have any links? Perhaps it will have some info in the books I just ordered, but until those arrive I'll keep pawing in the dark and asking you nice folks questions!

Thanks so much for the help/info!
 
Hmm, I haven't noticed that - are you sure it's just not that there are fewer of them so fewer people have/discuss them?
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My statement is the product of a combination of parroting what others(altec user's board) have said and final prices realized on ebay.

The majority of my 604 listening has been on model 17's which are 604-8G in the 620 cabinet, my listening hours on those are well into the thousands even tho they've been gone for some time now. I've also heard 604B's and 605A's, tho not enough time spent with either to comment beyond simply saying look to the later models for superior low end performance. It appears according to the replacement parts list that the 604D was the last of the 604's to use the old style HF diaphragm, i "think" the newer style phragms have better HF extension due to thinner phragm material or ligher coil, or possibly a combination of both................... but don't quote me on that.

Lots of info here:

http://alteclansingunofficial.nlenet.net/

One thing that's going to also be relevant is what you plan to drive them with in regard to tubes or solid state.
 
Free air resonance no greater than 40 Hz. My hunch was right about that part.

eMail doesn't typically get a response at GPA. You're going to have to call.

Tuneable ports: PE sells adjustable port tubes. They also sell multi-piece assembleable flared type; you'd adjust the tuning using different length center sections.

Me, I'd just be using ABS pipe from Home Depot, and swapping in different lengths as desired.

Another option I like is multi-porting, like a manifold, with 2 - 4 ducts appropriately sized. Then, you can close one or more of the ducts with plumbers' test plugs to try different tunings at will, or close them all for closed box.

Understand that there is no "right" tuning for any particular driver/box combination, rather merely optimum tunings for various performance objectives. There are, however, good and bad tunings from a listening perspective, for sure.... :yes:
 
Although not building a new baffle as you originally ask would be nessesary,if your future i.e.5years is open/pending.Just get a nice equaliser and do your best until you settle down for a while...then giv'er

cheers
 
bowtie427ss said:
One thing that's going to also be relevant is what you plan to drive them with in regard to tubes or solid state.
Click to expand...

Tubes. I have some Curcio modded Dynaco MKIV's (EL34, 40wpc) and a Pilot 245A (EL84, 17wpc). I'm also thinking of building some 6v6 monoblocks out of some Philco console amps I got along with the Altecs.

Zilch - I look into those tunable port options. Thanks for the recommendations.
 
Tubes. I have some Curcio modded Dynaco MKIV's (EL34, 40wpc) and a Pilot 245A (EL84, 17wpc). I'm also thinking of building some 6v6 monoblocks out of some Philco console amps I got along with the Altecs.
Click to expand...
You're going to be very pleased.:yes:

It's said that the earlier 604's are better mated to tubes because of their stiffer compliance/mechanical damping, but we have members here running late model 604's on flea power with nothing but satisfaction, your ears will determine what works best for you, and that you have several amplifier choices to pick from is all the better.

I lived with 604-8G's on a modded ST70 for several months, can't think of a complaint other than i wish the ST70 had been one of a bridged pair, this is what led me to a bigger room and A7's. But, that's all about my personal listening and musical preference. I have 6550 monoblocks in mind for my next 604's, but i'm a bit tempted to bi-amp with big solid state on the LF and smaller tubes on the HF. I've been living with a Behringer DCX in system for the last couple months and it takes bi-amping to a new level and for me it puts a different perspective on bi-amping 604's.

I know where i want to be, i just need to map out my route to get there.
 
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