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Need specs to build a cab around Altec Lansing 421A... Can you help?

Discussion in 'Amps and Cabs [BG]' started by KF2B, Feb 7, 2015.


  1. KF2B

    KF2B

    Jan 28, 2013
    Finland
    Greetings,

    so I´ve got this pristine Altec Lansing 421A driver which needs a cabinet around it.

    For lower SPL TONE Machine with capitals, whaddya recommend..?
     
  2. christw

    christw Get low!

    May 11, 2008
    Dayton OH
    I want to be Tesla (tinkerer at Dayton Amp Co)
    TL606 cab? The '70's B-15's ran TL cabs with Altecs I believe. Where's JimmyM when you need him? :D
     
    topcat2069 likes this.
  3. rigtec

    rigtec

    Jan 30, 2012
    NJ
    Hi KF,

    Ampeg used the 421A a lot in the 70's, the B-25L (L for Lansing) was just one. It was a ported cabinet and 'Claimed' to extend to 40hz. There was also the SBT cab; which may have been a 120w active (Powered) cab w/an Altec Lansing option. The cabs measurements are easy to find online, just cut the inner dimensions in half for one speaker; Here's a photo of one (Best!):

    images?q=tbn:ANd9GcSjTi1pivLAPrBMrWIPg3A-qK-8ilRSXGEEtlucuvZTEA5Y95HEEg.
     
    Last edited: Feb 7, 2015
  4. http://www.greatplainsaudio.com/vintage_altec.html

    I recorded these specs with DATS2 on a fresh recone by Great Plains Audio:
    * This data was exported from DATS the Dayton Audio Test System
    *
    * Manufacturer:
    * Model:
    * Piston Diameter = 330.2 mm
    * f(s)= 29.61 Hz
    * R(e)= 6.656 Ohms
    * Z(max)= 190.3 Ohms
    * Q(ms)= 8.079
    * Q(es)= 0.2928
    * Q(ts)= 0.2825
    * V(as)= 82.83 liters (2.925 cubic feet)
    * L(e)= 1.357 mH
    * n(0)= 0.7002 %
    * SPL= 90.55 1W/1m
    * M(ms)= 359.3 grams
    * C(ms)= 0.08 mm/N
    * BL= 38.98
    * K(r)= 0.07764
    * X(r)= 0.5156
    * K(i)= 0.0141
    * X(i)= 0.6689
    *
    *
    Freq Impedance Phase
    1.029 6.767 4.573
    1.059 6.767 4.573
    1.091 6.767 4.573
    1.122 6.767 4.573
    1.155 6.767 4.573
    1.189 6.767 4.573
    1.224 6.767 4.573
    1.260 6.767 4.573
    1.297 6.767 4.573
    1.335 6.762 9.428
    1.374 6.762 9.428
    1.414 6.762 9.428
    1.456 6.762 9.428
    1.498 6.762 9.428
    1.542 6.762 9.428
    1.587 6.762 9.428
    1.634 6.762 9.428
    1.682 6.762 9.428
    1.731 6.762 9.428
    1.782 6.762 9.428
    1.834 6.762 9.428
    1.888 6.762 9.428
    1.943 6.762 9.428
    2.000 6.845 13.845
    2.059 6.845 13.845
    2.119 6.845 13.845
    2.181 6.845 13.845
    2.245 6.845 13.845
    2.311 6.845 13.845
    2.378 6.845 13.845
    2.448 6.845 13.845
    2.520 6.845 13.845
    2.594 6.845 13.845
    2.670 7.043 17.759
    2.748 7.043 17.759
    2.828 7.043 17.759
    2.911 7.043 17.759
    2.997 7.043 17.759
    3.084 7.043 17.759
    3.175 7.043 17.759
    3.268 7.043 17.759
    3.364 7.250 21.682
    3.462 7.250 21.682
    3.564 7.250 21.682
    3.668 7.250 21.682
    3.775 7.250 21.682
    3.886 7.250 21.682
    4.000 7.518 25.518
    4.117 7.518 25.518
    4.238 7.518 25.518
    4.362 7.518 25.518
    4.490 7.518 25.518
    4.621 7.518 25.518
    4.757 7.823 29.238
    4.896 7.823 29.238
    5.040 7.823 29.238
    5.187 7.823 29.238
    5.339 8.208 32.755
    5.496 8.208 32.755
    5.657 8.208 32.755
    5.823 8.208 32.755
    5.993 8.628 35.943
    6.169 8.628 35.943
    6.350 8.628 35.943
    6.536 8.628 35.943
    6.727 9.107 38.807
    6.924 9.107 38.807
    7.127 9.107 38.807
    7.336 9.583 41.371
    7.551 9.583 41.371
    7.772 9.583 41.371
    8.000 10.103 43.753
    8.234 10.103 43.753
    8.476 10.103 43.753
    8.724 10.606 45.904
    8.980 10.606 45.904
    9.243 10.606 45.904
    9.514 11.155 47.977
    9.792 11.155 47.977
    10.079 11.702 49.828
    10.375 11.702 49.828
    10.679 12.320 51.718
    10.992 12.320 51.718
    11.314 12.973 53.402
    11.645 12.973 53.402
    11.986 13.706 55.166
    12.338 13.706 55.166
    12.699 14.506 56.722
    13.071 14.506 56.722
    13.454 15.393 58.321
    13.849 15.393 58.321
    14.254 16.376 59.695
    14.672 17.448 61.078
    15.102 17.448 61.078
    15.545 18.647 62.229
    16.000 19.938 63.325
    16.469 19.938 63.325
    16.951 21.407 64.224
    17.448 22.984 65.010
    17.959 24.791 65.679
    18.486 24.791 65.679
    19.027 26.777 66.157
    19.585 30.393 66.655
    20.159 31.898 66.735
    20.749 34.931 66.791
    21.357 38.427 66.759
    21.983 42.622 66.508
    22.627 47.602 65.978
    23.290 53.629 65.133
    23.973 61.083 63.935
    24.675 70.664 62.145
    25.398 83.040 59.427
    26.143 99.383 55.545
    26.909 121.387 49.582
    27.697 147.416 40.508
    28.509 171.417 27.772
    29.344 188.313 3.456
    30.204 183.133 -21.916
    31.089 165.407 -36.287
    32.000 129.809 -50.861
    32.938 99.099 -59.311
    33.903 80.133 -63.536
    34.896 66.387 -66.045
    35.919 57.260 -67.400
    36.971 50.074 -68.238
    38.055 44.200 -68.653
    39.170 38.844 -68.855
    40.317 36.186 -68.838
    41.499 33.464 -68.788
    42.715 30.443 -68.627
    43.967 28.011 -68.401
    45.255 26.005 -68.097
    46.581 24.340 -67.715
    47.946 22.932 -67.240
    49.351 21.734 -66.670
    50.797 20.695 -66.001
    52.285 19.782 -65.244
    53.817 18.775 -64.188
    55.394 17.867 -63.044
    57.018 17.207 -62.077
    58.688 16.307 -60.606
    60.408 15.617 -59.394
    62.178 14.965 -58.234
    64.000 14.367 -57.159
    65.875 13.706 -56.005
    67.806 13.120 -55.015
    69.792 12.612 -54.172
    71.838 12.185 -53.431
    73.943 11.831 -52.729
    76.109 11.530 -51.939
    78.339 11.247 -50.873
    80.635 11.045 -49.795
    82.998 10.835 -48.414
    85.430 10.623 -46.887
    87.933 10.394 -45.299
    90.510 10.116 -43.543
    93.162 9.829 -41.973
    95.892 9.531 -40.548
    98.701 9.293 -39.513
    101.594 9.079 -38.519
    104.571 8.900 -37.468
    107.635 8.759 -36.290
    110.789 8.616 -34.854
    114.035 8.481 -33.515
    117.377 8.341 -32.200
    120.816 8.216 -30.990
    124.356 8.110 -29.746
    128.000 8.037 -28.624
    131.751 7.962 -27.341
    135.611 7.873 -25.779
    139.585 7.795 -24.476
    143.675 7.722 -23.168
    147.885 7.655 -21.922
    152.219 7.596 -20.598
    156.679 7.543 -19.258
    161.270 7.498 -18.035
    165.995 7.446 -16.781
    170.860 7.398 -15.548
    175.866 7.361 -14.221
    181.019 7.341 -13.011
    186.324 7.329 -11.727
    191.783 7.330 -10.308
    197.403 7.349 -9.061
    203.187 7.377 -7.959
    209.141 7.402 -6.765
    215.269 7.431 -5.565
    221.577 7.485 -4.407
    228.070 7.565 -3.354
    234.753 7.648 -2.529
    241.632 7.720 -1.864
    248.712 7.786 -1.248
    256.000 7.840 -0.675
    263.501 7.896 -0.082
    271.223 7.967 0.442
    279.170 8.033 0.704
    287.350 8.075 0.743
    295.770 8.063 0.738
    304.437 8.010 0.931
    313.358 7.938 1.415
    322.540 7.873 2.157
    331.991 7.827 3.091
    341.719 7.805 4.096
    351.732 7.805 5.186
    362.039 7.824 6.175
    372.647 7.851 7.121
    383.567 7.883 8.087
    394.806 7.928 9.086
    406.375 7.993 9.938
    418.282 8.038 10.621
    430.539 8.055 11.459
    443.155 8.094 12.596
    456.140 8.181 13.623
    469.506 8.277 14.451
    483.264 8.363 15.221
    497.424 8.471 16.018
    512.000 8.567 16.504
    527.003 8.615 17.064
    542.445 8.657 18.043
    558.340 8.768 19.180
    574.701 8.926 20.088
    591.541 9.078 20.780
    608.874 9.234 21.453
    626.715 9.412 22.058
    645.080 9.596 22.658
    663.982 9.862 23.130
    683.438 10.162 22.799
    703.464 10.277 21.826
    724.077 10.278 21.491
    745.294 10.308 21.750
    767.133 10.422 21.572
    789.612 10.391 21.272
    812.749 10.316 21.633
    836.565 10.288 22.492
    861.078 10.373 23.457
    886.309 10.512 24.135
    912.280 10.632 24.329
    939.012 10.660 24.604
    966.527 10.685 25.438
    994.849 10.794 26.330
    1024.000 10.950 27.125
    1054.005 11.127 27.799
    1084.890 11.327 28.227
    1116.680 11.477 28.444
    1149.401 11.569 28.877
    1183.081 11.755 29.701
    1217.748 12.019 30.165
    1253.431 12.290 30.413
    1290.159 12.628 29.771
    1327.964 12.659 28.542
    1366.876 12.370 28.349
    1406.929 12.235 29.897
    1448.155 12.362 31.548
    1490.589 12.585 32.995
    1534.266 12.928 34.433
    1579.224 13.531 35.427
    1625.499 14.118 34.884
    1673.129 14.571 33.590
    1722.156 14.655 32.088
    1772.619 14.562 31.278
    1824.561 14.445 31.637
    1878.024 14.543 32.332
    1933.055 14.768 32.659
    1989.697 14.932 32.547
    2048.000 15.003 32.587
    2108.011 15.068 32.994
    2169.780 15.249 33.524
    2233.360 15.451 33.595
    2298.802 15.545 33.738
    2366.162 15.606 34.068
    2435.496 15.755 34.993
    2506.862 16.043 35.525
    2580.318 16.383 35.788
    2655.927 16.629 35.576
    2733.752 16.774 35.481
    2813.857 16.836 35.665
    2896.309 16.993 36.074
    2981.178 17.149 36.405
    3068.533 17.258 36.751
    3158.448 17.380 37.463
    3250.997 17.614 38.385
    3346.259 17.986 39.086
    3444.312 18.392 39.372
    3545.238 18.709 39.360
    3649.121 18.916 39.423
    3756.049 19.086 39.760
    3866.109 19.308 40.369
    3979.395 19.625 41.047
    4096.000 20.028 41.569
    4216.022 20.443 41.897
    4339.561 20.837 42.121
    4466.720 21.214 42.343
    4597.605 21.581 42.615
    4732.325 21.982 43.029
    4870.992 22.505 43.465
    5013.723 23.130 43.643
    5160.637 23.808 43.465
    5311.855 24.443 42.835
    5467.504 24.764 41.776
    5627.714 24.930 41.595
    5792.619 25.397 41.416
    5962.355 25.728 40.144
    6137.066 25.345 39.350
    6316.896 24.981 40.184
    6501.995 25.166 41.483
    6692.518 25.603 42.321
    6888.623 26.076 42.864
    7090.476 26.542 43.191
    7298.242 26.967 43.504
    7512.097 27.401 43.836
    7732.218 27.884 44.189
    7958.790 28.395 44.434
    8192.000 28.892 44.637
    8432.044 29.392 44.859
    8679.122 29.926 45.073
    8933.439 30.478 45.242
    9195.209 31.054 45.381
    9464.649 31.634 45.405
    9741.985 32.151 45.421
    10027.447 32.656 45.533
    10321.273 33.239 45.712
    10623.710 33.881 45.804
    10935.008 34.510 45.771
    11255.428 35.095 45.712
    11585.238 35.663 45.677
    11924.711 36.205 45.657
    12274.132 36.742 45.720
    12633.791 37.331 45.839
    13003.989 37.960 45.924
    13385.035 38.609 46.020
    13777.247 39.299 46.093
    14180.951 39.999 46.129
    14596.485 40.720 46.206
    15024.194 41.542 46.313
    15464.437 42.562 46.301
    15917.579 43.653 45.778
    16384.000 44.311 44.858
    16864.088 44.488 44.321
    17358.243 44.695 44.344
    17866.879 45.200 44.562
    18390.418 45.845 44.634
    18929.299 46.484 44.552
    19483.969 47.018 44.526
    20054.893 48.099 44.816
    20642.546 52.604 45.336
     

    Attached Files:

    Last edited: Feb 7, 2015
    Stumbo, NoBlackTShirts and xk49w like this.
  5. DukeLeJeune

    DukeLeJeune rational romantic mystic cynical idealist Supporting Member Commercial User

    Nov 24, 2008
    Princeton, Texas
    Owner & designer, AudioKinesis; Auth. mfg, Big E (Home Audio only)
    That SPL figure looks low to me for an 421-A in good condition. I would have expected something up around 98 dB (Altec measured SPL at 4 feet instead of 1 meter, used a conservative yardstick, and claimed 97 dB for the 421A).

    Your Vas also looks way low... those old Altec woofers had a huge (by modern standards) Vas, as the resulting high efficiency (and requisite large box size) is how they got good SPL from the modest power amplification of the day.

    My armchair guess is that the Vas figure should be in the 350 to 400 liter range, and I think your other measured parameters look reasonable.

    I don't think you're going to get a strong first overtone of low-B out of that woofer. Anyway here is one possible design, fartout threshold may be modest:

    Four cubic feet net internal volume tuned to about 60 Hz by two 5" diameter holes cut in 3/4" plywood (no actual port tube needed - the port length is .75 inches, with both ends flush). Use a golden ratio for the internal cabinet dimensions, brace it well, and start out with no damping material. You can add a little mattress topper later if needed, but use no more than needed to get the tone you want.

    Since you will have a fair amount of midrange energy emerging from these large shallow ports, you might want to take that into account when you choose their locations. I would be tempted to put one on either side of the box, to get some midrange energy going off to the sides. Maybe put one port higher than the centerline of the magnet, and one lower, to get a little bit of chimney effect cooling... those older Altecs had only modest thermal power handling.
     
    TomB likes this.
  6. It was DATS2 software and hardware ($99) so I don't know how accurate. No acoustic measurement and I don't think I plugged in Xlim. It is an A reconed with an A-H8 kit fresh out of the shipping box.
     
  7. DukeLeJeune

    DukeLeJeune rational romantic mystic cynical idealist Supporting Member Commercial User

    Nov 24, 2008
    Princeton, Texas
    Owner & designer, AudioKinesis; Auth. mfg, Big E (Home Audio only)
    I think there may be a problem with the moving mass figure. It looks high... 359 grams is way up there. You might want to double-check whatever your source is for that figure.
     
  8. I used the additive method, the scale is new, but no guarantee of accuracy. I should check for program updates. Calculations are made by the program during a frequency sweep.

    Thank you for the close attention Duke!
     
  9. DukeLeJeune

    DukeLeJeune rational romantic mystic cynical idealist Supporting Member Commercial User

    Nov 24, 2008
    Princeton, Texas
    Owner & designer, AudioKinesis; Auth. mfg, Big E (Home Audio only)
    I think that, for whatever reason, your system is including the added mass as part of the cone's moving mass. Check to be sure you've entered the right data into the right box. If you have, then I think there's a bug in the program.

    You are quite welcome... I've learned from experience to question my own data, as I'm highly dependent on good data, and also highly capable of making mistakes!
     
    Last edited: Feb 7, 2015
    TomB and B-string like this.
  10. I had a pair of 421 8H II s.
    I remember they did like a big box, had great sensitivity and seemed to go pretty low.

    Duke, I too am very good at making mistakes.
    I should be.
    I've had LOTS of practice.
     
  11. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Another vote for the EV TL606.

    The Ampeg B-15S was a good sounding cabinet. It was thiele based and the 421A was offered in it. Here are its specs. As was mentioned, it was used in other Ampeg cabinets.
     
    70spbase likes this.
  12. So I re-ran the Altec today. Not sure if I had the driver unobstructed during the add mass VAS test, this time it was without any obstruction.

    * This data was exported from the Dayton Audio Test System: DATS
    *
    * Manufacturer: Altec Lansing
    * Model: 421A-8H
    D 330.2 [mm]
    Re 6.643 [Ohms]
    Fs 30.28 [Hz]
    Zm 177.1 [Ohms]
    BL 17.8 [N/A]
    Qms 7.586
    Qes 0.2956
    Qts 0.2845
    Vas 383.9 [liters]
    L10k 0.5107 [mH]
    n0 3.438 [%]
    dBSPL 97.46 [1W/1m]
    Ms 74.11 [grams]
    Cms 0.373 [mm/N]

    I didn't copy and paste the impedance points but will if anyone is interested.
     
  13. DukeLeJeune

    DukeLeJeune rational romantic mystic cynical idealist Supporting Member Commercial User

    Nov 24, 2008
    Princeton, Texas
    Owner & designer, AudioKinesis; Auth. mfg, Big E (Home Audio only)
    The data all looks reasonable to me. Thanks for taking the time!
     
    AstroSonic and B-string like this.
  14. 70spbase

    70spbase Fender/Ampeg for over 30 years!Portaflex #449 Supporting Member

    Nov 30, 2011
    Las Vegas

    Ampeg loved the Altec 421A and the 418B. Here's a shot of the "SBT" cabinet with the 421A. Same dimensions as the BT140 and an inch deeper than a BT25... 42x24x15. The speakers have a "sound" that is very tone happy and mated to the ampeg eq perfectly. They are very happy in a B15S cab as well, as they're breathers. Also I just picked up a V-6B cab for my head and I'm thinking about replacing the original Eminence speakers with a pair of 421 TYPE BASS MUSICAL INSTRUMENT SPEAKERS. I just spoke with Bill at Great Plains to pay for my recone (nicest guy ever) he used to work at Altec when these were first built. He informed me of many details and a little bit of trivia. The 421A was rated for a bit lower power than it really handles. They (on paper) were rated at 100 watts 97db ...but they can handle 150 in a properly tuned cab. Single 15" in a box 26"x24"x15" with proper batting made of plywood with bracing and at least one 4" port or the shelf the width of the cab should get you down to 35-40HZ. p.s. Remember 150 watts max 8ohms
     

    Attached Files:

  15. rigtec

    rigtec

    Jan 30, 2012
    NJ
    Sometimes... I would give anything to go back to the days when I moved one of these (I was 16) back-n-forth to gigs and then... back up to my bedroom for safe keeping, lol! They too utilized the Altec Lansing 421-A drivers. Rated at 240W rms, this cabinet kicked some royal booty. I was using the 120W Ampeg BT-25 (transistor) head with it; I only wish that I could have afforded the SVT head at the same time that I had the V4B cab!
    V4B-folded-horn.
    The picture on the right shows the V4B cab opened up and reveals the EV SRO on top, and an EVM in the bottom deck. They were rated for 150W RMS.

    The V4B pictured below was (imho) "King-of-the-stage" back in 1973-76; and only rivaled by the Acoustic 371/301!
    v-4b.
    I only sold it cuz the band was starting to complain about hoisting the 225lb beast up/down the stairs every week-end.

    I bought the SUNN 118BH (Below) and eventually did get an Ampeg SVT Head to go on top... "A real monster!"
    index.php?action=dlattach;topic=6660.

    Enjoy the memories folks, rigtec!
     
    Last edited: Feb 11, 2015
    spankdaplank and Giorgetto like this.
  16. BTW the original 421A used aluminum voice coil wire and was conservatively rated at 100 watts. The "H" as in 8H, 16H used copper voice coil wire and upped the power handling another 50 watts.
     
  17. rigtec

    rigtec

    Jan 30, 2012
    NJ
    Has anyone else here ever used one of these in a 'full range stack' (no x-over) back in the seventies? I don't know who made the Mid/bass horn box that I had (wasn't AL), but it had the same physical dimensions and looked like this below:

    altec-lansing-816-399930. 269935d1405180080-utforming-horn-altec-515-8-lf-altec-816a.

    Mine was armed w/ a 400W "Cetec Gauss 4580":
    19558777. 101_2241.

    And then I used the 18 inch 'Gauss 8842' in the 'SUNN 118BH' Bass Horn pictured above.
    Gauss_18_Speakers_2.042810.1_026.

    Back then, you weren't considered a REAL musician unless you had 'at least' one 'Herniated disc' or a torn 'Medial Meniscus' from moving your amp on week-ends. wtf.

    "Ahhh....Those were the days" Rgds!
     
  18. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Heh, we played through all kinds of fun S/M devices back then. I had a 421-8H loaded Eliminator knockoff cab similar to this:

    [​IMG]

    ...which was big fun to get in an out of a Volvo 122 sedan's trunk. That cab, a B-15, and an EBO, or later, a cheap upright: sonic nirvana --NOT! I later had decent results with a 421A in a TL606 though.
     
  19. rigtec

    rigtec

    Jan 30, 2012
    NJ
    Hahaha, "Nice"!

    That one brings to mind the Cerwin Vega B-48 or 'Sensurround EarthQuake' subwoofer folded horns.
     
  20. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    A B-48 cab with the front-firing 12 in it lived in a local music store for a few years, ca. mid-70s. The shop owner was a drummer, and his kit was in the front window. I jammed with him a few times, with the C-V cab pretty much all the way in the back of the long, narrow store. He had one of the Vega amps too, and I got the feeling that the placement of the drums and bass rig was no mistake. [​IMG]
     

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