416-8A DCR values

[DarcyL]

So I have a pair of freshly re-coned 416-8A's that I got in a set of speakers, and I decided to re-cap the crossovers. While in there, I thought I'd check the dcr of the woofers. One is 6.9 ohms, which seems right to me, but the other is 5.5 ohms. They seem to sound/play right, with no voice coil rub or anything- Is the 5.5 ohm rating alarming? If the magnet on that woofer needs recharging could that contribute to the low dcr reading? Or should I pretend I didn't test them, and just keep listening?
Thanks,
Darcy

[Earl K]

So I have a pair of freshly re-coned 416-8A's that I got in a set of speakers, and I decided to re-cap the crossovers. While in there, I thought I'd check the dcr of the woofers. One is 6.9 ohms, which seems right to me, but the other is 5.5 ohms. They seem to sound/play right, with no voice coil rub or anything- Is the 5.5 ohm rating alarming? If the magnet on that woofer needs recharging could that contribute to the low dcr reading? Or should I pretend I didn't test them, and just keep listening?
Thanks,
Darcy

Magnet strength has nothing to do with a dcr measurement .

That dcr spread ( of 1.4 ohms ) is alarming if your measurements are actually accurate .

Some causes of dcr inaccuracy can be;

(i) Your measuring technique ( using oxidized test probes for instance ) .

(ii) Meter battery is low.

(iii) ( Another possibility ) is that the re-cones with ( so-called ) Altec parts actually aren't ( Altec parts ).
- Pull the woofers and post pics of any numbers you find on the back of the paper cones.

(iv) Partially shorted voice-coil ( can occur > from over-driving a woofer in an effort to get more bass ).

[DarcyL]

Well, measuring technique is not the problem, and there is a fresh battery in my Fluke DMM- Also If these Altec 416's can be overdriven by a small amp at living room listening levels, maybe they're junk anyway and need to be replaced by something durable-

Darcy

[Earl K]

Hi Darcy,

If your 416's were reconed with the proper GPA parts ( Altec Pro is long since out of business ), they'll have these numbers stamped on the back of the cones .

It's the GPA35400 number that's relevant .

[jimd]

The target DCR of an 8 ohm 416, is 6.5 ohms. Normal deviation ought to be 6.2-6.8 ohms. 5.5 ohms is the usual DCR of a MI speaker, 417-418-421, a lot fo JBL's, Eminences etc. They are actually 7 ohm (real impedance), not 8 ohm drivers. The lower DCR makes the speaker a bit louder, it is, it's drawing more current.

Sounds to me that you have a recone with improper parts, it is going to hurt, well, it depends on the voice coil that's in there. The 416-515-604 8 ohm coil is .2 inches winding depth, the 417-418-421 8 ohm coil is .3 inches deep. The current MWA replacement coil is .28, although it's the right DCR. The longer coil will simply mean your 416 will have less linearity, if it's deeper, you won't know unless you take it apart. If you are real careful, you can get it apart, but you will need to be as good as a professional reconer to do that.

As for the crossover, it will be a little off, if you are real critical you can compensate, if it's BiAmped, it won't matter. GPA uses the LF cone in all it's recones. it's a little better behaved than the original, but a touch heavier. Lots of contingencies here.

Jim

[DarcyL]

The target DCR of an 8 ohm 416, is 6.5 ohms. Normal deviation ought to be 6.2-6.8 ohms. 5.5 ohms is the usual DCR of a MI speaker, 417-418-421, a lot fo JBL's, Eminences etc. They are actually 7 ohm (real impedance), not 8 ohm drivers. The lower DCR makes the speaker a bit louder, it is, it's drawing more current.

Sounds to me that you have a recone with improper parts, it is going to hurt, well, it depends on the voice coil that's in there. The 416-515-604 8 ohm coil is .2 inches winding depth, the 417-418-421 8 ohm coil is .3 inches deep. The current MWA replacement coil is .28, although it's the right DCR. The longer coil will simply mean your 416 will have less linearity, if it's deeper, you won't know unless you take it apart. If you are real careful, you can get it apart, but you will need to be as good as a professional reconer to do that.

As for the crossover, it will be a little off, if you are real critical you can compensate, if it's BiAmped, it won't matter. GPA uses the LF cone in all it's recones. it's a little better behaved than the original, but a touch heavier. Lots of contingencies here.

Jim

Thanks for all of the replies/ info- I'll check out the stamping on the cones next time I open up the cabs. For now I think I'll start saving my pennies to send the pair off to GPA. These were bought from a reputable speaker repair shop in Vancouver, and sold as 'rebuilt with Altec parts', though now I am questioning that-

Darcy

[DarcyL]

Also, the reason I asked about the magnet strength in the first post here, was that the woofer that measures 5.5 R , also has a dent on the magnet cover, leading me to believe it was dropped at some time in it's life- hopefully before the 'rebuild', and not after-

Darcy

[DarcyL]

Ok, one last idea- If I were to put a 1-1.5r non inductive resistor in line right before the woofer, would that help even the output difference out? Or bad idea?

Darcy

[Earl K]

Ok, one last idea- If I were to put a 1-1.5r non inductive resistor in line right before the woofer, would that help even the output difference out? Or bad idea?

Darcy

Why do you ask about this?

You could add the mentioned value of resistor ( personally, for a permanent situation I'd add a minimum of 4 paralleled, 4 ohm 10-watt resistors > to increase the power handling to 40 watts > 20 watt resistors would be safer , if you can find them ).

Adding inline resistance to a woofer does change it's effective "Q" .
- One can typically see the predicted results from within a box tuning program such as WinISD ( as an example ).

[grumpy]

I'd find someone with a "woofertester" setup (and perhaps REW) and see if this is a problem worth addressing. DC resistance indicates some issue is likely (as has already been noted), and at least one woofer may not be at its best, but it may also just be academic if you're enjoying them as-is. Just another thought to consider. Happy listening

[DarcyL]

Well, I finally got around to taking the drivers out, and checked the cones for numbers- The one that tests 6.9R is stamped 21184-8, which I believe is an original Altec cone. The one that measures 5.5R, also has an altec number, but it indicates it is a 421-8a cone, which makes the dcr reading correct for that voice coil. Looking through the vented dust cap, I can see the voice coil former is I believe aluminum, not paper, like the correct 416. The shop that did these left the aluminum dustcap off of the 421 cone, and put the correct vented 416 dustcap on instead. Now, I need help deciding- leave well enough alone, because at least they're original cones, although one is not correct, at least in the voice coil? or, have GPA recone the one with the 421 cone, and keep the one original 416, or get GPA to do both re-cones? any thoughts??
Thanks,
Darcy

[Earl K]

Thanks for the update ( your situation is as JimD suggested ) .

Personally, I wouldn't send your woofers over the border for a recone ( using the newer GPA parts ) .

Original Altec stamped kits ( having the # 21184-x ) have more resale value than the current xxx-35400 types ( from what I've seen ) .

I don't feel it's worth the trans-border shipping expense and risk. ( other opinions may differ )

If you want to buy a pair of GPA recone kits > Bill will sell direct to you ( you can use them now or store them for future consideration ).

I don't think either type of cone kit will address your current problem of disappointing bass response ( these large VAS woofers need a large cabinet volume of over 7.5 cu' & you're currently not providing that > if I remember your system particulars correctly ) .

[DarcyL]

Thanks for the update ( your situation is as JimD suggested ) .

Personally, I wouldn't send your woofers over the border for a recone ( using the newer GPA parts ) .

Original Altec stamped kits ( having the # 21184-x ) have more resale value than the current xxx-35400 types ( from what I've seen ) .

I don't feel it's worth the trans-border shipping expense and risk. ( other opinions may differ )

If you want to buy a pair of GPA recone kits > Bill will sell direct to you ( you can use them now or store them for future consideration ).

I don't think either type of cone kit will address your current problem of disappointing bass response ( these large VAS woofers need a large cabinet volume of over 7.5 cu' & you're currently not providing that > if I remember your system particulars correctly ) .

Thanks for the response, that was kind of what I was leaning towards- trying to order 2 cone kits from GPA, and keep them for later- as far as the bass goes, it's pretty good now, I cut the bottom of the Santiago cabinets out, and set them on top of 1.7 cu. Ft. Riser boxes with a foam gasket between the two. They are solidly built, sealed and lined with polyfill- if my math is correct, that should make7.2 cu. Ft. Total volume. I used the vent calculator on winisd, and at 7.2 cu Ft, with 2, 4" dia x 6" long ports, it should be tuned to 32Hz. Sounds pretty nice.I hope I don't give anyone a heart attack about cutting the cabinets up!

Darcy

[Earl K]

Thanks for the response, that was kind of what I was leaning towards- trying to order 2 cone kits from GPA, and keep them for later- as far as the bass goes, it's pretty good now, I cut the bottom of the Santiago cabinets out, and set them on top of 1.7 cu. Ft. Riser boxes with a foam gasket between the two. They are solidly built, sealed and lined with polyfill- if my math is correct, that should make7.2 cu. Ft. Total volume. I used the vent calculator on winisd, and at 7.2 cu Ft, with 2, 4" dia x 6" long ports, it should be tuned to 32Hz. Sounds pretty nice.I hope I don't give anyone a heart attack about cutting the cabinets up!

Darcy

Ahh OK, > glad things are starting to work out .

Modifying your Santiagos ( so they work for your components ) is certainly not a crime / & sure it beats the pants off of some ( unknown ) hoser sending them to the land-fill .

[DarcyL]

Thanks so much for all the help/info!
Darcy