Altec 416-8Z Measured T/S Parameters

**gdmoore28** · January 23rd, 2016, 05:54 PM

After searching for a year to find the T/S parameters for my 416-8Zs, and finding none (and having no measuring equipment of my own), I've finally run across an Italian gent who actually measured a pair for his own project. For those who may have been seeking same, here are his findings.

Altec 416-8Z

Fs..................25.098Hz
Vas................735.167 liter
Qts................0.334
Qms...............4.222
Qes................0.363
Le..................0.567mH
L1..................1.042mH
R1..................11.595 ohms
Re..................6.594 ohms

I've seen a number of people suggest that the 416Z has the same parameters as the 416B, but the author of this article notes the following differences:

Model : Xmax Re Fs Vas Qts Qms Qes
(inch) (cm) (ohms) (Hz) (cu. ft.) (litres)
416-8B Altec factory data 0.15 0.381 6.90 25.10 26.47 749.6 0.32 7.05 0.33
416-8Z Measured - - 6.59 25.1 735 0.33 4.22 0.36

(Sorry, could not get the above table to align properly once posted.)

If interested, you can read the whole story here: Audio Garage Gallery

I've no interest in his cabinet design (for obvious reasons), but these figures can be valuable, especially if anybody can verify them.

GeeDeeEmm

GM · January 24th, 2016, 03:52 PM

Thanks! Can't have too many sets of measured specs, though due to a variety of things they can be pretty far off from yours as me, Lynn and others posted about in the last few pages of this thread and if you search it for Altec, a lot of other good info: Beyond the Ariel - diyAudio

Bottom line, if you don't measure yours, then it's a 'crap shoot' as to what you'll wind up with frequency response wise, leaving only stuffing density, empirically tuning the vent [if applicable] by either ear to whatever sounds best overall to you or to the driver's actual Fs [a good plan if coupled to a high output impedance amp].

This is why I recommend/spec an acoustically large cab to ensure there's enough acoustic efficiency unless the specs are so far off as to need re-building or flat out replacing since it's a lot easier to tune, or worst case, reduce internal volume [Vb] as required with scrap materials/whatever that doesn't rattle.

GM

**gdmoore28** · January 24th, 2016, 05:06 PM

100% agreed. We'll be doing the central Arkansas speaker builders meet later this year. I'll see if I can lasso one of those guys to test my 416s for me.

GeeDeeEmm

**Old Guy** · January 24th, 2016, 08:21 PM

If I recall the Altec factory specs were calculated only

**endeeinn** · January 25th, 2016, 11:48 AM

For what its worth I did some measurements of my 416-16Z's that were in my Valencia's (86A's) back in 1980 (the Valencias were at least 5 years old by then). My brother and I each bought a pair of Valencia's at the same time (5 years or so before) and he called Altec to ask what the difference was between the 86A's and 86B's. The person he spoke to at Altec sent him a marked up print of the 86A Valencia that showed how to make the A's into a B by closing up the vent around the 811 and adding 2 3" diameter ports X inches long (i forget how many inches). Having read about T/S and how each speaker needed it's T/S parameters calculated I decided not to take Altec's recommendation at face value but measure my drivers and calculate the lengths myself. I got the method from some vendor's flier on T/S measurement so don't know how well those instructions fare against current methods and those instructions are long gone. It was also the first and last time I tried measuring my own drivers and much had to be hand calculated so math errors could play into it as well. The instructions outlined 2 different methods and I performed them both (no computer aids or programs). These are the results: Fs=27 and 27.5; Vas= 26.110 cu ft; Qts=.2380 to .2550; Qms= 2.09 to 2.209; Qes=.2464 to .2830; Re=10.5 and 11.3. As shown Fs, Vas, and Re were consistent between methods and left and right drivers as those parameters are straight forward but there was variation with calculated Qts, Qms and Qes which forced me to make some decisions as to which numbers to go with in calculating port diameters and length and necessitated different lengths for right and left drivers. After implementing them I felt at the time that bass had firmness, punch and less boom but I realize that I had to feel that way after going through the trouble of determining and parameters and altering the Valencias. As I recall the lenghts of the 3" ports varied from Altec's reccomendation by only and inch or two so I'm not sure what I gained by calculating them myself. Today I'm using A5's so I can't do any rechecking of the parameters but if I did I'd use some of the software/hardware solutions that do all the calculations.

GM · January 25th, 2016, 12:28 PM

Originally Posted by Old Guy

If I recall the Altec factory specs were calculated only

Wouldn't surprise me and if so, would be the most accurate average for the then current versions since they would use the actual design/build specs, i.e. Re, BL, Mms, Cms, etc., that these are composed of.

GM