Altec 416-8b woofers

Hey everyone,

I started to post about these woofers in my other posting for a MLTL design but decided a separate thread devoted to these woofers might be better.

I've four of these woofers and recently tested them with DATS and was quite disappointed. All four woofers tested off from what the specs are suppose to be. Two were pretty bad with the other two not as bad:

fs: qts:
40hz .56
39hz .54
30hz .3
27hz .26

I've a 416-C to test against so I know the DATS is giving me pretty close readings.

Its my thought the magnets need recharged which would explain the high qts but not the high fs.

I spoke with Bill at GPA and I've sent all four in to be reconed and have the magnets recharged. For the benefit of others I'll post the results when I receive them back.

In hind site had I known the Alnico Magnets can become weakend if over driven (what I suspect has happened to these) I might have selected the "C" model over the "B"

At any rate even if I don't end up using these 416-b's I couldn't bring myself to sell them without having them fixed first.

Does anyone have any thoughts on how much power one can safely run on these without fear of weakening the magnetic field strength? More the reason I see for running two per channel vs one. I'll be running mine with a PassLabs XA30.8 which can hit about 150 watts pk. so be about 75 per woofer pk. I do realize amps can do a lot more when driven to clipping but I don't abuse my equipment. I do however like to crank it up a bit every now and then.

Any thoughts appreciated and I'll post the results when I get these back from GPA. That way any others considering the same have access to this info. I suspect there are a whole lot of 416-b's out there with weakened magnetic fields.

Mark

I?m curious to know the answer to this also. I drive my AlNiCo drivers with high power SS amps and don?t want to push them too hard either.

I?m curious which would happen first, mag loss or VC damage. Assuming a normal Altec/GPA VC is being used.

If it was I, and it's not I would've sent Uncle Willy just the two way out of spec 416's so we all could have seen what the difference of a remagging does since you have the test equipment. Remember the value goes down once you don't have the original cones. Plus it will save you some money. If the remagging works get the other two remaged since he'll have all four anyway's.

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I do realize amps can do a lot more when driven to clipping but I don't abuse my equipment.

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I just have to know, are you implying/insinuating that driving an amplifier to clipping is abuse?

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Originally Posted by bowtie427ss

I just have to know, are you implying/insinuating that driving an amplifier to clipping is abuse?

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Would "abuse" be the wrong term? I'm a bit slow are you being sarcastic?

Anyway in home audio I would think so.

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Originally Posted by LOUDER

If it was I, and it's not I would've sent Uncle Willy just the two way out of spec 416's so we all could have seen what the difference of a remagging does since you have the test equipment. Remember the value goes down once you don't have the original cones. Plus it will save you some money. If the remagging works get the other two remaged since he'll have all four anyway's.

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Good idea but I figured I prefer if they all match. I think we should be able to tell when I measure them all once I get them back. I'm a little concerned to find out.

I’m curious how close the woofers test after GPA is done with them.

Re amp clipping: I always drove my pro amps into light clipping doing small shows for the band that I was in. And even at home when I had less efficient speakers. No amp or speaker damage ever occurred. If you drove the amps into heavy clipping I would think the speakers would be damaged first, as your nice sine wave turned into a squarish wave.
The amp should be able to handle a square wave. Hell, I’ve heard you can weld with an Ashly amp. :cool:

Lol, just thinking about it. I used to turn my amps up into clipping and then turn them down slightly.

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Originally Posted by Elitopus1

I?m curious how close the woofers test after GPA is done with them.

Re amp clipping: I always drove my pro amps into light clipping doing small shows for the band that I was in. And even at home when I had less efficient speakers. No amp or speaker damage ever occurred. If you drove the amps into heavy clipping I would think the speakers would be damaged first, as your nice sine wave turned into a squarish wave.
The amp should be able to handle a square wave. ****, I?ve heard you can weld with an Ashly amp. :cool:

Lol, just thinking about it. I used to turn my amps up into clipping and then turn them down slightly.

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I think that make sense in terms of Bowtie's remark. Hence some clipping may not be considered abuse. Given you're reply then yes I probably have done the same. I should have worded my remark differently. It may be almost normal to drive an amp to some clipping during dynamic passages. I was thinking more in terms of grossly over driving the amp.

Just remember that ALL Alnico magnets lose magnetism over time, not just from being overdriven. It is also possible that the two that are so far off might not have original factory cones in them. There are a lot of counterfeits out there. Further, all speakers can be negatively affected by heat and humidity, as well.

Also - Some Thiele-Small parameters are derived from mathematical formulae using information acquired during direct measurement of a loudspeaker. In the late 1980s, while working with Mr. Jerry K. Hubbard, then head of Altec Lansing's Acoustic Laboratory, he and I discovered that a few of the original derivations were actually in error. If you were measuring using the original parameters published by Altec, that could explain some of the variances you found.

The Thiele-Small parameters published on the page below have been checked and corrected, where necessary, using the mathematical formulae given to the author by Mr. Hubbard, and include most of the newer models produced by Altec Lansing since the original publication of Technical Letter No. 267B.

Altec Thiele-Small Parameters

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If you drove the amps into heavy clipping I would think the speakers would be damaged first, as your nice sine wave turned into a squarish wave.

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Clipping, in and of itself does not damage speakers. They could really care less about the shape of a waveform.

The only thing that you can input to your speaker wires that will damage your speakers is too much power. The ways you can arrive at this are many, and one certainly includes poorly designed amplifiers that generate large high frequency harmonics when driven to hard clipping. Blame that excessive power on those harmonics for any damage incurred, not the clipped off peak of a waveform.

For those who want to eliminate their clipping paranoia, please see the good folks at Audio Classics for a Powerguard equipped McIntosh and never worry about clipping again.

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Would "abuse" be the wrong term? I'm a bit slow are you being sarcastic?

Anyway in home audio I would think so.

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Mostly just mincing words. We are probably largely in agreement at the end of the day.

But, on the surface i consider occasional clipping less abusive than say letting your $1k+ phono cartridge run off into the dead wax.

In a well sorted system either incident should be able to occur hundreds and hundreds of times with no visible, audible, or otherwise measurable damages.

Thanks much for the reply Todd,

I used the DATS to test them and I have no idea how precise it is. I think is must be close because I have a 416-C which tested almost exactly to specs listed on this green chart.

I'm anxious to test mine once I get them back but after speaking with Bill at GPA I feel confident they'll be good to go. I think it's probably about the best we can do with 40 year old woofers. I'm grateful we have someone out there like him keeping these alive.

One thing I'm unsure of if I need to break them in a little before I test them.

Thanks Bowtie,

Yes perfect sense I agree. I like to crank it up every now and then but at my age nothing like I did back 40 years ago.

I have bad tinnitus which prevents it. I think resulting from my time in the military as well as my first job right after high school in a very noisy welding/metal shop. Around 1974 time frame I can remember safety being big on wareing goggles / face shields but there was little if any emphasis on hearing protection.

Mark

Update - Got my four woofers back but sadly one has voice coil rub. Box looks fine but I know they wouldn't have shipped back to me like that so something must have happened to it in shipping. Kinda turns yer stomach. Oh well I have to ship it back again.

Update again - no voice coil rub after all. They had not clipped one side of the leads which had excess wire hanging over shorting intermittently to the other lead. Caused scratchy sound on DATS test.

I clipped the excess wire from the lead now it works fine. :)

I have all four woofers back and everything looks good. Here is the thing - I can post the DATS results if anyone wants to see but I'm not sure it's meaningful.

I was reading at DIYAUDIO and someone said DATS just measures the impedance curve and then guesses at the TS Parms. It isn't accurate.

I think Todd had kind of hinted this in his prior reply to me here as well.

I'm just going to use them and not worry about it. I'm an old timer and kinda prefer tuning ports the old fashioned way anyway. ie frequency generator measuring the two impedance curves across a resistor & cutting ports to length.

Yes, please.


ALL these type testers use the measured impedance and calculates all but Vas with dead on accurate math, so sure would like to see this post.


That said, there's two DATS, the original [pro] Smith & Larson: woofertester.com and PE's cheap rip-off that they may be referring to accuracy wise, though even it does fine when set up just right, the tide is out, zero noise during measuring, etc., ;) and some say the V2 is much better, though as always YMMV.


Which do you have?


GM

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Originally Posted by GM

Yes, please.


ALL these type testers use the measured impedance and calculates all but Vas with dead on accurate math, so sure would like to see this post.


That said, there's two DATS, the original [pro] Smith & Larson: woofertester.com and PE's cheap rip-off that they may be referring to accuracy wise, though even it does fine when set up just right, the tide is out, zero noise during measuring, etc., ;) and some say the V2 is much better, though as always YMMV.


Which do you have?


GM

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I have the V2 - I'll post the results I do have.

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Attachment 4018Attachment 4019Attachment 4020Attachment 4021

The high FS one these do bother me. One of them is 41 hz

Thanks! Need Vas, but before you do it, please post the instructions as I may want it done differently.

GM

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Originally Posted by GM

Thanks! Need Vas, but before you do it, please post the instructions as I may want it done differently.

GM

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Alright - It'll probably take me a while to get to that as I think I need a test box. I'll have to check for instructions on that too.

I think it's safe to assume the actual VAS will be different from spec as well.

I was thinking of something - My DATS V2 does test a 416-8c that I have right on published specs so maybe it isn't really as far off as someone over at DIYAUDIO suggested.

If accurate then the QTS on these is pretty far off too. The QTS on these almost looks good for aperodic loading although not with that high fs.

I searched around a lot and have not found anyone else posting specs after getting recones or new GPA woofers either.

No, you don't and why I want its instructions.

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Originally Posted by GM

No, you don't and why I want its instructions.

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Oh sorry I missundersood - Copied below:

8) Measure the driver's V as.'10 20Notes:50 100 200 500 1kHz. 2k111111111111111111111111111111111111111111111111 1111V(BJ• 1? [cu7t-609 C" AddedMassMethod1209 M = ?o-- grams? C" Spedied SPL Method-160" SPL .?o-- ?,?;;m;;;Sk 10k 20k(' Specified M(md)M(md) = ?o--gramsMeasured ParametersR(e(. 173913 Ohm,F{s)=�HzQ(ts] = fo.s'13Q[e,J,fo:98,Q(m,)•[4Ts7L(e)•�k,,H(lOkJM[ms] = ?o--gramsV(as)= ?o--[cuitr Test Lead Resislance, L R(tl. � Dh'.":._JFigure 1: A Typical DATS V2 screenOnce you have measured the speaker's free air parameters the "Measure V(as)" button becomes enabled.Select one of the four methods to measure the Vas at the upper right side of the DA TS V2 screen. The fourVas measurement methods are:
1) Test Box Method - requires a suitable test box
2) Added Mass Method - requires you to add a known mass
3) Specified SPL Method - requires the SPL be known
4) Specified MMD Method - requires the MMD be known
Enter the required data and then press the "Measure V(as)" button to start the measurement procedure.

Thanks! Huh! Not seeing any recommendations for how much mass or reduced Fs. Not good unless it tells you it needs more.

Regardless, the pioneers determined that the test box raise Fs at least 50% and more specifically 1.56x while I've often seen write-ups for only 20-25%! With added mass then, Fs ideally needs to drop by 1.56x, so will need to be evenly distributed around the Vc. Hope you have an accurate scale.

Some folks say Vas measurement can be pretty far off and have little impact on cab design, which is true, but Vas is just about everywhere in the other specs, so can be used to check the others and frankly not sure of some of them since Bill did [2] pair of 414B last year and Jeff's measurements showed all were basically identical, so surprised these are so far off by Altec standards, at least up to '75: Thiele Small parameters equations - How each one affects the others

GM

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Originally Posted by GM

Thanks! Huh! Not seeing any recommendations for how much mass or reduced Fs. Not good unless it tells you it needs more.

Regardless, the pioneers determined that the test box raise Fs at least 50% and more specifically 1.56x while I've often seen write-ups for only 20-25%! With added mass then, Fs ideally needs to drop by 1.56x, so will need to be evenly distributed around the Vc. Hope you have an accurate scale.

Some folks say Vas measurement can be pretty far off and have little impact on cab design, which is true, but Vas is just about everywhere in the other specs, so can be used to check the others and frankly not sure of some of them since Bill did [2] pair of 414B last year and Jeff's measurements showed all were basically identical, so surprised these are so far off by Altec standards, at least up to '75: Thiele Small parameters equations - How each one affects the others

GM

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Okay thanks - I'm working a string of 12 hour shifts but will try playing with this again on a day off maybe end of next week. I'll check the manual better too make sure I'm didn't miss part of it.

Mark

I found further directions to measure VAS (two sections in the manual) I'll play with this some more soon as I can. I'll reinstall DATS software and make sure everything is setup properly and remeasure everything.

Measure V(as) by the Selected Method

Before any measurements are made this command is disabled (grayed out). After making a free air measurement this command becomes enabled and can be used to measure the V(as) of a driver by any of four methods. The V(as) test method is selected at the Parameters Bar at the right side of the main window. You can also Measure V(as) by clicking the same named button at the Impedance Bar at the left side of the main window. The four methods are: Test Box, Added Mass Specified SPL and Specified M(md).

• Test Box: This method is probably the most widely used and trusted. For this method you will need a test speaker enclosure of suitable size for the driver being tested
• Added Mass: Although the added mass method can employ added mass in the simple form of coins added to the cone it is best to make sure the added mass actually adheres to the cone so that it moves with the cone at all times. If the mass "decouples" as the cone moves then accuracy will be compromised. Use an added mass that will shift the F(s) lower by about 25-50%. An added mass equal to the driver's Mms is just about right. DATS will warn you if the shift in the measured F(s) is not within the above recommended range.

Items commonly used for added mass include: coins, modeling clay, carpenters putty, rope caulk and tape rolls. In general you should measure the weight of the added mass accurate to 1/10th of a gram. In a pinch, US coins can provide an easy source of standard weights. One US nickel ($.05) weighs 5.0 grams.

• Specified SPL: This is a simple V(as) method as it requires no test box or added masses. It is also probably the least accurate as it depends strongly on the accuracy of the SPL you specify.
• Specified M(md): This is another simple V(as) method. It requires that you know the actual moving mass of the driver. This method is especially suitable for use by driver manufacturers where the driver's components are readily available for weighing. It is also a good method for comparing similar drivers.

Each of the four methods of measuring V(as) requires that you enter the Piston Diameter of the driver. The piston diameter is the effective diameter of the acoustic piston formed by the speaker. The piston diameter is measured as the diameter of the speaker cone and normally includes about half of the surround on each side of the cone. For example, a nominal 8 inch woofer would probably have an actual piston diameter in the range from about 6.25 to 6.5 inches.

Seems like the added mass method would be the easiest to do at home. Using nickels or other coins because of the consistent weight values seems tempting, but how does one attach nickels to the cone so they don?t decouple?
Clay seems like it would stick just enough, and there are inexpensive scales available that go down to .01 grams.

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Originally Posted by Elitopus1

Seems like the added mass method would be the easiest to do at home. Using nickels or other coins because of the consistent weight values seems tempting, but how does one attach nickels to the cone so they don?t decouple?
Clay seems like it would stick just enough, and there are inexpensive scales available that go down to .01 grams.

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I've used painters tape as opposed to masking tape, it's more easily removed. Tear a short piece and roll it into a loop with the adhesive facing out. Stick the nickel to one side and the other side to the speaker. Comes off easily.

Attachment 4022....Attachment 4023....Attachment 4024....Attachment 4025

I think the DATS on these is accurate because of the fact that I have an original (not reconed) 416-8C that tests almost right on published specs. I'm not sure why so much variance going on here. Actually maybe not so much variance but not on par with published specs. I guess recones essentially half Altec half GPA. I see why many like to keep the original cones. I wish I could afford a new pair of GPA 416-B's just to compare. Price on those is out of reach for most of us on a budget.

I?m kind of surprised the specs on those drivers are different like they are. I would think that being done all in a row, with recone kits from the same batch would make very similar specs when tested. But maybe variations in the motors themselves account for some of that?

Do you know how close the woofers are in production dates to each other?

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Originally Posted by Elitopus1

I?m kind of surprised the specs on those drivers are different like they are. I would think that being done all in a row, with recone kits from the same batch would make very similar specs when tested. But maybe variations in the motors themselves account for some of that?

Do you know how close the woofers are in production dates to each other?

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Well I boxed them back up again until I'm ready to use them so I can't look for serial numbers right now. I should have thought of that I guess.

However I don't think so. They were not obtained together but in two separate pairs. The frames look new condition and look like late model b versions. The cones had blemishes which was one of the reason I wanted them reconed. Once I get them installed I wanted them looking like new. That and for sure I wanted the magnets recharged.

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but how does one attach nickels to the cone so they don?t decouple?

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One uses small neodymium magnets in pairs with one of each pair on either side of the cone.

They won't de-couple, there's no tape to create a compliance between the mass and cone, and there's no sticky stuff to pull up pulp fibers or leave sticky residue on your pristine cones.

Yes, that's a good way and used slot car magnets [or bits n' pieces of] for small drivers, but woofers take enough weight to lower Fs by 1.56x that between this and the ideal of having the weight centered on the Vc that I used various size deep bottom plastic mugs to place over the DC and pour sand in till I got the desired lower Fs.

Curious though, recently just got some of the little Nd mags and they're so powerful even compared to the AlNiCo 5 that seems like it would be easy to damage the diaphragm surface just trying to pry them apart?

GM

For added mass I used (search ebay) "25 Pcs Super Strong N35 Neodymium 6 x 2 mm Disc Magnets " and a steel ring from a $5 Walmart tribet (3 concentric rings, easily pulled apart into individual rings). Then you have multiple rings, appropriate for various sized drivers.

The tribet ring goes on the front, magnets on the back to hold it 'centered'. Magnets allow you to adjust the centering... but beware that if you break the magnetism the little disc magnets will find a home wherever they can in any little crevice (or get stuck to the back of the surround goop). So count how many you start with and make sure you end with the same number. :-) Keep some tweezers or a hemostat handy to pluck them out of tight spaces if need be.

Well I believe the latest specs I posted above are pretty accurate due to a comparison to a 416-8c I have tested and the specs almost match published specs.

I'm disappointed with the high FS especially one measuring 40hz. That could still work fine if I decided to use it with subwoofers below 50hz or so but I originally had my heart set on MLTL cabinets. However I'm unsure if the QTS of .5 on one woofer isn't to far off for MLTL design too. Seems better suited to sealed or aperiodic loading.

I don't regret having the four woofers reconed because as mentioned the cones all had blemishes and such due to age. I wanted them to look new which they do now.

I'm not in any hurry to complete this design as this is suppose to be a retirement project for me. My plan was to collect everything needed but actually do the build around spring of next year when I retire and have extra free time on my hands. (still a year away)

Hence I'm just going to think on this design a lot between now and then. Another problem I'd mentioned in my MLTL thread is I'm not sure where the put the horns because of the cabinets needing to be so tall in order to use two 416's per channel.

Lots to plan and think about. Thanks to everyone who has replied to all of my threads here. I've learned a lot already and appreciate everyone's suggestions / ideas!

Mark