AudioBlog

BlogWorthy - Basic Audio e-book

2011-01-22T19:37:00.000-08:00

Basic Audio By Norman CrowHurst

This online book is actually written in plainspeak !!

DIY OS waveguide

2010-12-28T07:40:00.000-08:00

I thought these posts / articles were "blogworthy" . Enjoy !!

http://www.diyaudio.com/forums/gedlee/122318-diy-waveguide-loudspeaker-kit-153.html

http://www.enjoythemusic.com/diy/1110/oblate_spheroid_waveguides.htm

Push Pull 2A3 tube amplifier complete

2009-06-05T13:55:00.000-07:00

From 2A3 Push Pull Tube Amplifier

After neglecting this project for over a year because of a variety of reasons, I finally got it working over the weekend. I addressed a couple of irritating initial issues namely:

Electrical hum due to a ground loop (shortened the ground return paths)
Mechanical hum in L1 of the LCLC power supply filter (replaced L1 (320 mH / 10 ohm Triad choke with a 10 ohm resistor resulting in an RCLC filter). Since the output stages is push pull, they can excelled common mode noise rejection and aren't bothered by what I simulated to be around 1V PP of hum. The input stage is quitened down by a rather severe RC stage dropping about 50 % of B+ (290V).

I'll add a schematic later on, but the circuit itself is exceedingly simple: Single ended D3A (in triode mode) driving a rathe expensive (and luckily for me, free) Electra-Print SE:PP interstage transformer powering a push pull pair of 2A3 triodes in cathode bias . Output transformers were scavenged from a dead Fisher 800C receiver and I'm estimating output power in the 6W / class A range with some A2 capability (though I could probably get this circuit to run about 15 W class AB with some minor mods + fixed bias).

No global feedback. Some minimal local feedback around the cathodes of the push pull pairs via 30uF capacitors (all I had at that moment). Bias is relatively conservative around -45 V and PK voltage of about 245V,

Power supply capacitors are around 50uF ASC motor run capacitors. Still need to bypass them .

Power transformer is a heavy duty low DCR (< 10 ohm) 240:110V transformer run backwards in step up mode.

Sound: I'll let others decide, but I think it's fair to say that, unlike some of my other "endeavors", this has been a successful high end project.

Calibration File for WM-61AY microphone capsule

2009-05-25T12:33:00.000-07:00

Download the data from http://www.holmacoustics.com/downloads/MicrophoneCalibration/Mic_WM61A.cal

Test Your Hearing

2009-05-03T09:51:00.000-07:00

http://www.digital-recordings.com/hearing-test/www-ht-pro/ht_help_p.html

TangBand Reverse Tapped Pipe

2009-04-06T18:16:00.000-07:00

Or more commonly known as a reverse tapped horn, though that is really an oxymoron. In any case, I built a prototype of this on a lark using a single Tang Band W69-1042J 6"x9" Subwoofer using 1/" MDF (yuck !!). I played around with stuffing and finally left it unstuffed. Despite being unstuffed, the bass is non-resonant ie. non boomy. Note that I did take the time to add side - to side braces (not shown in picture). Well, it isn't going to displace the big horn sub, as I can find the limits of its excursion IF I want to (somewhat above normal listening levels though) but it was a good cheap experiment. Excursion is lower than expected, for the amount of sound it produces, but as I said, I can find it's limits Iif I want. Probably solid to 30 - 35 Hz with output below that. Remember, this is a 6 x 9 87db.w/m 8 ohm driver keeping up with a pair of 95 - 97+ db/w/m speakers (depending on what is currently hooked up) driven by a cheapo 100 W plate amp.

I wonder what would happen if I took off driver access plate and allowed the driver to breathe through more than the small terminus that it's now exposed to . Food for thought ....

Here are the input parameters and theoretical impedance curves.

Lastly, here are the observed impedance curves. Close but the 2nd impedance peak is off, probably due to differences caused buy the (inevitable) folding.

Stephens Trusonic 206-AXA 15" co-axial Crossover, Impedance Measurements, T/S measurements

2008-12-20T20:38:00.000-08:00

The crossover is a relatively simple affair: The woofer runs full range and the tweeter is a 2nd order (in reverse phase) consisting of something about 10 - 12uF cap (can't make out the exact value since it is encased in resin) and a 2mH inductor. I reverse engineered the values by isolating the components and measuring the L and C values using ARTA. Note that the tweeter is nominally 8 ohm in the 1 - 2KHz range

Woofer Impedance Graph

Tweeter + Horn Impedance graph

Compression Tweeter + Multicell Horn



* This data was exported from the Dayton Audio WT3 Woofer Tester
*
* Manufacturer:
* Model:
D     0.0 [mm]
Re    7.30 [Ohms]
Fs    637.20 [Hz]
Zm    7.69 [Ohms]
BL    0.00 [N/A]
Qms   0.031
Qes   0.576
Qts   0.029
Vas   0.000  [liters]
L10k  0.12 [mH]
n0    0.00 [%]
dBSPL   0.00 [1W/1m]
Ms    0.00 [grams]
Cms   0.00 [mm/N]
*
*
Freq            Impedance       Phase
1.029     7.301     -0.160
1.059     7.301     -0.160
1.091     7.301     -0.160
1.122     7.301     -0.160
1.155     7.301     -0.160
1.189     7.301     -0.160
1.224     7.301     -0.160
1.260     7.301     -0.160
1.297     7.301     -0.160
1.335     7.301     -0.185
1.374     7.301     -0.185
1.414     7.301     -0.185
1.456     7.301     -0.185
1.498     7.301     -0.185
1.542     7.301     -0.185
1.587     7.301     -0.185
1.634     7.301     -0.185
1.682     7.301     -0.185
1.731     7.301     -0.185
1.782     7.301     -0.185
1.834     7.301     -0.185
1.888     7.301     -0.185
1.943     7.301     -0.185
2.000     7.302     -0.199
2.059     7.302     -0.199
2.119     7.302     -0.199
2.181     7.302     -0.199
2.245     7.302     -0.199
2.311     7.302     -0.199
2.378     7.302     -0.199
2.448     7.302     -0.199
2.520     7.302     -0.199
2.594     7.302     -0.199
2.670     7.326     -0.012
2.748     7.326     -0.012
2.828     7.326     -0.012
2.911     7.326     -0.012
2.997     7.326     -0.012
3.084     7.326     -0.012
3.175     7.326     -0.012
3.268     7.326     -0.012
3.364     7.315     0.063
3.462     7.315     0.063
3.564     7.315     0.063
3.668     7.315     0.063
3.775     7.315     0.063
3.886     7.315     0.063
4.000     7.312     0.051
4.117     7.312     0.051
4.238     7.312     0.051
4.362     7.312     0.051
4.490     7.312     0.051
4.621     7.312     0.051
4.757     7.300     -0.041
4.896     7.300     -0.041
5.040     7.300     -0.041
5.187     7.300     -0.041
5.339     7.299     -0.019
5.496     7.299     -0.019
5.657     7.299     -0.019
5.823     7.299     -0.019
5.993     7.291     0.050
6.169     7.291     0.050
6.350     7.291     0.050
6.536     7.291     0.050
6.727     7.300     0.223
6.924     7.300     0.223
7.127     7.300     0.223
7.336     7.295     0.195
7.551     7.295     0.195
7.772     7.295     0.195
8.000     7.298     0.189
8.234     7.298     0.189
8.476     7.298     0.189
8.724     7.300     0.177
8.980     7.300     0.177
9.243     7.300     0.177
9.514     7.311     0.186
9.792     7.311     0.186
10.079     7.289     0.227
10.375     7.289     0.227
10.679     7.292     0.236
10.992     7.292     0.236
11.314     7.283     0.287
11.645     7.283     0.287
11.986     7.306     0.283
12.338     7.306     0.283
12.699     7.301     0.293
13.071     7.301     0.293
13.454     7.302     0.279
13.849     7.302     0.279
14.254     7.305     0.233
14.672     7.307     0.215
15.102     7.307     0.215
15.545     7.289     0.252
16.000     7.288     0.275
16.469     7.288     0.275
16.951     7.289     0.342
17.448     7.305     0.345
17.959     7.302     0.354
18.486     7.302     0.354
19.027     7.306     0.326
19.585     7.309     0.258
20.159     7.302     0.235
20.749     7.306     0.248
21.357     7.303     0.264
21.983     7.301     0.288
22.627     7.300     0.305
23.290     7.306     0.363
23.973     7.305     0.378
24.675     7.310     0.376
25.398     7.313     0.345
26.143     7.313     0.380
26.909     7.313     0.370
27.697     7.313     0.349
28.509     7.313     0.358
29.344     7.313     0.386
30.204     7.314     0.411
31.089     7.317     0.456
32.000     7.314     0.474
32.938     7.318     0.499
33.903     7.318     0.513
34.896     7.318     0.514
35.919     7.314     0.538
36.971     7.313     0.530
38.055     7.312     0.567
39.170     7.313     0.596
40.317     7.314     0.599
41.499     7.314     0.606
42.715     7.315     0.593
43.967     7.315     0.610
45.255     7.317     0.619
46.581     7.317     0.646
47.946     7.312     0.664
49.351     7.311     0.690
50.797     7.310     0.714
52.285     7.315     0.732
53.817     7.320     0.754
55.394     7.324     0.792
57.018     7.323     0.803
58.688     7.325     0.815
60.408     7.320     0.822
62.178     7.320     0.851
64.000     7.318     0.875
65.875     7.321     0.900
67.806     7.322     0.899
69.792     7.323     0.918
71.838     7.321     0.940
73.943     7.322     0.984
76.109     7.321     1.034
78.339     7.322     1.092
80.635     7.324     1.127
82.998     7.325     1.147
85.430     7.326     1.157
87.933     7.327     1.189
90.510     7.328     1.207
93.162     7.329     1.229
95.892     7.331     1.259
98.701     7.333     1.316
101.594     7.334     1.372
104.571     7.333     1.410
107.635     7.334     1.417
110.789     7.334     1.432
114.035     7.335     1.461
117.377     7.336     1.517
120.816     7.340     1.571
124.356     7.341     1.633
128.000     7.341     1.676
131.751     7.340     1.710
135.611     7.341     1.755
139.585     7.344     1.793
143.675     7.346     1.852
147.885     7.346     1.906
152.219     7.345     1.958
156.679     7.344     1.996
161.270     7.347     2.042
165.995     7.349     2.104
170.860     7.352     2.167
175.866     7.352     2.218
181.019     7.353     2.260
186.324     7.356     2.329
191.783     7.358     2.416
197.403     7.358     2.483
203.187     7.360     2.532
209.141     7.364     2.604
215.269     7.366     2.684
221.577     7.366     2.753
228.070     7.368     2.810
234.753     7.371     2.891
241.632     7.372     2.970
248.712     7.373     3.042
256.000     7.378     3.124
263.501     7.381     3.224
271.223     7.383     3.315
279.170     7.386     3.404
287.350     7.388     3.503
295.770     7.390     3.588
304.437     7.394     3.681
313.358     7.397     3.784
322.540     7.400     3.887
331.991     7.404     3.994
341.719     7.408     4.101
351.732     7.412     4.220
362.039     7.416     4.337
372.647     7.420     4.460
383.567     7.425     4.584
394.806     7.428     4.716
406.375     7.434     4.851
418.282     7.438     4.987
430.539     7.444     5.135
443.155     7.450     5.283
456.140     7.457     5.430
469.506     7.462     5.579
483.264     7.469     5.753
497.424     7.477     5.927
512.000     7.486     6.115
527.003     7.498     6.324
542.445     7.511     6.541
558.340     7.527     6.771
574.701     7.551     7.015
591.541     7.586     7.238
608.874     7.636     7.335
626.715     7.680     7.178
645.080     7.684     6.896
663.982     7.648     6.806
683.438     7.610     7.004
703.464     7.593     7.322
724.077     7.591     7.652
745.294     7.596     7.970
767.133     7.605     8.281
789.612     7.617     8.595
812.749     7.630     8.914
836.565     7.646     9.239
861.078     7.664     9.572
886.309     7.684     9.919
912.280     7.707     10.285
939.012     7.735     10.673
966.527     7.770     11.086
994.849     7.814     11.517
1024.000     7.873     11.947
1054.005     7.956     12.298
1084.890     8.052     12.400
1116.680     8.125     12.220
1149.401     8.146     11.993
1183.081     8.133     11.979
1217.748     8.120     12.194
1253.431     8.118     12.530
1290.159     8.121     12.958
1327.964     8.131     13.507
1366.876     8.161     14.185
1406.929     8.219     14.889
1448.155     8.301     15.559
1490.589     8.401     16.179
1534.266     8.520     16.727
1579.224     8.655     17.201
1625.499     8.812     17.506
1673.129     8.953     17.585
1722.156     9.054     17.756
1772.619     9.169     18.439
1824.561     9.401     19.380
1878.024     9.796     20.026
1933.055     10.346     19.672
1989.697     10.918     17.696
2048.000     11.253     14.151
2108.011     11.141     10.356
2169.780     10.712     8.026
2233.360     10.249     7.522
2298.802     9.952     8.365
2366.162     9.899     9.858
2435.496     10.120     10.992
2506.862     10.497     10.675
2580.318     10.763     8.470
2655.927     10.605     5.629
2733.752     10.150     4.378
2813.857     9.784     4.840
2896.309     9.643     5.537
2981.178     9.579     6.237
3068.533     9.581     7.135
3158.448     9.655     7.497
3250.997     9.663     7.478
3346.259     9.692     7.227
3444.312     9.704     6.465
3545.238     9.574     5.344
3649.121     9.368     5.244
3756.049     9.226     5.963
3866.109     9.129     6.760
3979.395     9.049     7.466
4096.000     8.976     8.238
4216.022     8.926     9.142
4339.561     8.918     10.097
4466.720     8.943     10.892
4597.605     8.974     11.492
4732.325     8.976     11.985
4870.992     8.965     12.628
5013.723     8.972     13.435
5160.637     9.012     14.220
5311.855     9.063     14.914
5467.504     9.114     15.613
5627.714     9.189     16.383
5792.619     9.309     17.013
5962.355     9.434     17.192
6137.066     9.484     17.061
6316.896     9.455     17.114
6501.995     9.416     17.562
6692.518     9.416     18.281
6888.623     9.470     19.055
7090.476     9.571     19.639
7298.242     9.637     19.749
7512.097     9.624     20.057
7732.218     9.602     20.864
7958.790     9.672     21.776
8192.000     9.760     22.425
8432.044     9.830     22.965
8679.122     9.887     23.596
8933.439     9.960     24.349
9195.209     10.065     25.098
9464.649     10.196     25.771
9741.985     10.338     26.055
10027.447     10.412     26.375
10321.273     10.458     26.910
10623.710     10.567     27.646
10935.008     10.683     28.189
11255.428     10.792     28.740
11585.238     10.916     29.335
11924.711     11.056     29.842
12274.132     11.184     30.292
12633.791     11.312     30.782
13003.989     11.458     31.285
13385.035     11.609     31.680
13777.247     11.752     32.035
14180.951     11.884     32.387
14596.485     12.021     32.689
15024.194     12.130     33.065
15464.437     12.236     33.512
15917.579     12.371     34.090
16384.000     12.523     34.584
16864.088     12.674     35.037
17358.243     12.824     35.514
17866.879     12.982     35.980
18390.418     13.145     36.411
18929.299     13.294     36.880
19483.969     13.428     37.363
20054.893     13.420     37.904
20642.546     12.819     38.105

Woofer


* This data was exported from the Dayton Audio WT3 Woofer Tester
*
* Manufacturer:
* Model:
D     317.5 [mm]
Re    9.44 [Ohms]
Fs    43.07 [Hz]
Zm    163.30 [Ohms]
BL    19.56 [N/A]
Qms   7.009
Qes   0.430
Qts   0.405
Vas   186.700  [liters]
L10k  0.89 [mH]
n0    3.31 [%]
dBSPL   97.30 [1W/1m]
Ms    64.39 [grams]
Cms   0.21 [mm/N]
*
*
Freq            Impedance       Phase
1.029     9.475     1.991
1.059     9.475     1.991
1.091     9.475     1.991
1.122     9.475     1.991
1.155     9.475     1.991
1.189     9.475     1.991
1.224     9.475     1.991
1.260     9.475     1.991
1.297     9.475     1.991
1.335     9.471     4.143
1.374     9.471     4.143
1.414     9.471     4.143
1.456     9.471     4.143
1.498     9.471     4.143
1.542     9.471     4.143
1.587     9.471     4.143
1.634     9.471     4.143
1.682     9.471     4.143
1.731     9.471     4.143
1.782     9.471     4.143
1.834     9.471     4.143
1.888     9.471     4.143
1.943     9.471     4.143
2.000     9.480     6.341
2.059     9.480     6.341
2.119     9.480     6.341
2.181     9.480     6.341
2.245     9.480     6.341
2.311     9.480     6.341
2.378     9.480     6.341
2.448     9.480     6.341
2.520     9.480     6.341
2.594     9.480     6.341
2.670     9.544     8.532
2.748     9.544     8.532
2.828     9.544     8.532
2.911     9.544     8.532
2.997     9.544     8.532
3.084     9.544     8.532
3.175     9.544     8.532
3.268     9.544     8.532
3.364     9.607     10.666
3.462     9.607     10.666
3.564     9.607     10.666
3.668     9.607     10.666
3.775     9.607     10.666
3.886     9.607     10.666
4.000     9.687     12.802
4.117     9.687     12.802
4.238     9.687     12.802
4.362     9.687     12.802
4.490     9.687     12.802
4.621     9.687     12.802
4.757     9.783     14.869
4.896     9.783     14.869
5.040     9.783     14.869
5.187     9.783     14.869
5.339     9.910     16.909
5.496     9.910     16.909
5.657     9.910     16.909
5.823     9.910     16.909
5.993     10.063     18.905
6.169     10.063     18.905
6.350     10.063     18.905
6.536     10.063     18.905
6.727     10.235     20.865
6.924     10.235     20.865
7.127     10.235     20.865
7.336     10.400     22.659
7.551     10.400     22.659
7.772     10.400     22.659
8.000     10.561     24.381
8.234     10.561     24.381
8.476     10.561     24.381
8.724     10.726     26.095
8.980     10.726     26.095
9.243     10.726     26.095
9.514     10.890     27.880
9.792     10.890     27.880
10.079     11.053     29.760
10.375     11.053     29.760
10.679     11.268     31.600
10.992     11.268     31.600
11.314     11.524     33.408
11.645     11.524     33.408
11.986     11.827     35.148
12.338     11.827     35.148
12.699     12.136     36.866
13.071     12.136     36.866
13.454     12.472     38.491
13.849     12.472     38.491
14.254     12.834     40.010
14.672     13.204     41.440
15.102     13.204     41.440
15.545     13.585     42.859
16.000     13.994     44.152
16.469     13.994     44.152
16.951     14.421     45.454
17.448     14.867     46.662
17.959     15.313     47.947
18.486     15.313     47.947
19.027     15.800     49.221
19.585     16.602     51.094
20.159     16.907     51.717
20.749     17.521     52.957
21.357     18.182     54.192
21.983     18.899     55.429
22.627     19.681     56.619
23.290     20.532     57.757
23.973     21.450     58.854
24.675     22.452     59.907
25.398     23.533     60.884
26.143     24.716     61.836
26.909     26.006     62.738
27.697     27.426     63.545
28.509     28.975     64.233
29.344     31.643     65.070
30.204     34.579     65.661
31.089     36.765     65.879
32.000     40.563     66.145
32.938     45.020     66.228
33.903     50.690     65.960
34.896     57.536     65.182
35.919     66.381     63.528
36.971     77.140     60.975
38.055     95.419     55.665
39.170     121.311     45.999
40.317     138.398     36.950
41.499     154.019     23.462
42.715     163.042     2.408
43.967     156.276     -18.701
45.255     136.178     -35.750
46.581     110.862     -47.000
47.946     89.861     -53.480
49.351     75.367     -57.249
50.797     65.121     -59.672
52.285     57.383     -61.231
53.817     49.948     -62.200
55.394     43.985     -62.361
57.018     40.177     -61.990
58.688     35.765     -60.921
60.408     32.866     -59.783
62.178     30.399     -58.605
64.000     28.394     -57.415
65.875     26.368     -56.109
67.806     24.688     -55.041
69.792     23.316     -54.278
71.838     22.196     -53.841
73.943     21.259     -53.521
76.109     20.404     -53.147
78.339     19.544     -52.469
80.635     18.918     -51.592
82.998     18.305     -50.280
85.430     17.749     -48.648
87.933     17.228     -46.798
90.510     16.649     -44.610
93.162     16.055     -42.548
95.892     15.394     -40.628
98.701     14.836     -39.219
101.594     14.316     -37.984
104.571     13.884     -36.907
107.635     13.585     -35.947
110.789     13.364     -34.829
114.035     13.205     -33.642
117.377     13.012     -32.181
120.816     12.810     -30.555
124.356     12.580     -28.790
128.000     12.391     -27.291
131.751     12.190     -25.832
135.611     12.004     -24.272
139.585     11.885     -23.018
143.675     11.780     -21.672
147.885     11.700     -20.306
152.219     11.618     -18.982
156.679     11.518     -17.767
161.270     11.408     -16.575
165.995     11.322     -15.158
170.860     11.263     -13.747
175.866     11.199     -12.319
181.019     11.142     -11.107
186.324     11.103     -9.811
191.783     11.085     -8.296
197.403     11.083     -6.929
203.187     11.094     -5.717
209.141     11.118     -4.482
215.269     11.133     -3.342
221.577     11.133     -2.220
228.070     11.135     -0.984
234.753     11.160     0.300
241.632     11.207     1.560
248.712     11.275     2.795
256.000     11.353     3.890
263.501     11.425     4.945
271.223     11.484     6.045
279.170     11.539     7.112
287.350     11.624     8.369
295.770     11.728     9.506
304.437     11.829     10.614
313.358     11.967     11.820
322.540     12.127     12.914
331.991     12.292     13.903
341.719     12.440     14.840
351.732     12.604     16.009
362.039     12.831     17.145
372.647     13.112     18.152
383.567     13.412     18.972
394.806     13.763     19.785
406.375     14.147     20.274
418.282     14.542     20.628
430.539     15.003     20.708
443.155     15.430     20.436
456.140     15.906     20.329
469.506     16.612     19.510
483.264     17.321     16.943
497.424     17.470     12.531
512.000     16.668     8.402
527.003     15.217     7.340
542.445     14.078     9.826
558.340     13.657     13.169
574.701     13.586     16.184
591.541     13.753     18.786
608.874     14.011     20.484
626.715     14.202     21.782
645.080     14.375     23.366
663.982     14.702     25.055
683.438     15.142     26.246
703.464     15.590     26.986
724.077     16.028     27.501
745.294     16.513     27.810
767.133     17.014     27.781
789.612     17.503     27.291
812.749     17.947     26.275
836.565     18.119     24.703
861.078     17.904     23.284
886.309     17.538     23.128
912.280     17.271     23.782
939.012     17.165     24.477
966.527     17.075     25.346
994.849     17.039     26.421
1024.000     17.077     27.514
1054.005     17.161     28.611
1084.890     17.268     29.711
1116.680     17.397     30.861
1149.401     17.558     32.146
1183.081     17.801     33.544
1217.748     18.145     34.942
1253.431     18.611     36.174
1290.159     19.145     37.104
1327.964     19.732     37.704
1366.876     20.300     37.979
1406.929     20.757     37.969
1448.155     21.235     38.095
1490.589     21.630     37.894
1534.266     21.827     37.546
1579.224     21.772     38.095
1625.499     21.972     39.447
1673.129     22.494     40.792
1722.156     23.149     41.727
1772.619     23.861     42.554
1824.561     24.702     43.284
1878.024     25.701     43.814
1933.055     26.946     44.014
1989.697     28.382     43.477
2048.000     29.763     41.950
2108.011     30.816     39.716
2169.780     31.482     37.154
2233.360     31.528     34.353
2298.802     30.879     32.292
2366.162     30.157     31.814
2435.496     29.961     31.599
2506.862     29.518     31.003
2580.318     28.939     31.593
2655.927     28.936     32.575
2733.752     29.031     32.654
2813.857     28.714     33.279
2896.309     28.878     34.584
2981.178     29.339     34.945
3068.533     29.371     35.024
3158.448     29.337     35.893
3250.997     29.544     36.978
3346.259     29.946     37.964
3444.312     30.507     38.767
3545.238     31.003     39.204
3649.121     31.461     39.696
3756.049     32.033     40.275
3866.109     32.624     40.434
3979.395     33.027     40.630
4096.000     33.413     40.947
4216.022     33.812     41.431
4339.561     34.280     41.999
4466.720     34.875     42.589
4597.605     35.557     43.024
4732.325     36.213     43.328
4870.992     36.872     43.627
5013.723     37.551     43.893
5160.637     38.242     44.094
5311.855     38.898     44.243
5467.504     39.537     44.434
5627.714     40.207     44.643
5792.619     40.887     44.811
5962.355     41.538     44.969
6137.066     42.192     45.208
6316.896     42.914     45.463
6501.995     43.684     45.678
6692.518     44.468     45.859
6888.623     45.266     46.021
7090.476     46.077     46.160
7298.242     46.901     46.281
7512.097     47.736     46.389
7732.218     48.584     46.484
7958.790     49.439     46.557
8192.000     50.295     46.625
8432.044     51.163     46.698
8679.122     52.049     46.763
8933.439     52.955     46.820
9195.209     53.874     46.850
9464.649     54.795     46.870
9741.985     55.720     46.876
10027.447     56.648     46.880
10321.273     57.574     46.877
10623.710     58.502     46.877
10935.008     59.422     46.887
11255.428     60.353     46.928
11585.238     61.324     46.983
11924.711     62.327     47.026
12274.132     63.344     47.058
12633.791     64.370     47.090
13003.989     65.416     47.123
13385.035     66.485     47.150
13777.247     67.571     47.166
14180.951     68.669     47.175
14596.485     69.783     47.182
15024.194     70.919     47.191
15464.437     72.074     47.193
15917.579     73.242     47.188
16384.000     74.418     47.171
16864.088     75.590     47.153
17358.243     76.761     47.145
17866.879     77.961     47.152
18390.418     79.200     47.161
18929.299     80.477     47.161
19483.969     81.600     47.096
20054.893     81.747     46.767
20642.546     78.395     44.909

Speakers vs Tubes - when do they play nice with each other

2008-11-28T22:31:00.000-08:00

It's not as simple as tubes like high impedance speakers and vice versa.

Read this article, ... go catch some sleep and then read it again.
Wait a week.
Repeat
....

http://www.symphonysound.com/articles/tubefriendly.html

BlogWorthy - Crossover Mashup

2008-11-28T22:07:00.000-08:00

Description of various crossover types and their respective advantages / disadvantages/
http://www.audioholics.com/education/loudspeaker-basics/filter-crossover-types-for-loudspeakers

In the same vein, here's a simple walk-through of designing an actual crossover for a 3 way loudspeaker
http://burningass.110mb.com/crossover.php

And lastly, a basic crossover calculator.
http://www.ajdesigner.com/crossover/crossoverfirst.php

Theil and Small Parameters for the AudaxPR170MO

2008-10-26T21:22:00.000-07:00

Also tested with the WT3 while it was in my possession, here are the T/S specs.

* Piston Diameter = 133.3 mm
* f(s)= 97.57 Hz
* R(e)= 6.14 Ohms
* Z(max)= 27.44 Ohms
* Q(ms)= 1.754
* Q(es)= 0.505
* Q(ts)= 0.392
* V(as)= 10.820 liters (0.382 cubic feet)
* L(e)= 0.25 mH
* n(0)= 1.90 %
* SPL= 94.88 1W/1m
* M(ms)= 6.74 grams
* C(ms)= 0.39 mm/N
* BL= 7.08

Theil and Small Parameters for the University C15W woofer (silver frame)

2008-10-26T21:14:00.000-07:00

I recently had access to a Datyon Woofer Tester 3 to test the T/S parameters of this excellent vintage woofer. When I can, I'm also going to post comparative measurements using my ARTA jig. Of note, .. I consider the dual voice coil C15W to be a highly excellent woofer for my Karlson K-15 enclosure. Despite what literature would have one believe, I've sen Karlsons to be picky about what drivers they like (they prefer low mass cones, low Qts drivers). This driver+cabinet enclosure didn't just make the walls shake. It literally moved the whole first floor of place up and down. I don't think it made much bass below 50 Hz, but this is a real 50 Hz, not 50 Hz produced by some "subwoofer" you buy in the big-box store.

What does a Karlson look like? Here's a picture (not mine)

Series Voice Coils

* Piston Diameter = 330.2 mm
* f(s)= 69.98 Hz
* R(e)= 6.63 Ohms
* Z(max)= 74.00 Ohms
* Q(ms)= 3.708
* Q(es)= 0.365
* Q(ts)= 0.332
* V(as)= 91.420 liters (3.228 cubic feet)
* L(e)= 1.41 mH
* n(0)= 8.19 %
* SPL= 101.20 1W/1m
* M(ms)= 58.27 grams
* C(ms)= 0.09 mm/N
* BL= 21.58

Parallel Voice Coils

* Piston Diameter = 330.2 mm
* f(s)= 69.98 Hz
* R(e)= 2.32 Ohms
* Z(max)= 18.89 Ohms
* Q(ms)= 3.965
* Q(es)= 0.554
* Q(ts)= 0.486
* V(as)= 91.420 liters (3.228 cubic feet)
* L(e)= 0.36 mH
* n(0)= 5.39 %
* SPL= 99.42 1W/1m
* M(ms)= 58.27 grams
* C(ms)= 0.09 mm/N
* BL= 10.35

Unlocking Iphone Saga

2008-10-25T01:29:00.000-07:00

Not really audio related in the strictest of senses, but since an iphone is a fairly handy multimedia device, I figured this saga was blogworthy.

In short, I bricked an iphone whyile trying to install the 3rd party App Installer using the excellent program Ziphone. Had to crawl through tonnes of ill described articles and many juvenile youtube "how-to" guides.

I'm linking to the article that worked for me . I also found the following youtube useful to follow along in real time when trying to get the phone into DFU mode (timing is critical)

12b4a amp, version 2

2008-09-07T01:28:00.000-07:00

Looking to see if I could eke out any extra performance out of my 12b4a amp, version 1 , I tried the following
1. Increased cathode bypass resistor on the 12b4a output tubes to 250 uF . No audible change, so no changes there
2. Add film bypass capacitors to the power supply and cathode bypass electrolytic capacitors. Smoother sound, less grain. Definate yes.
3. Add a 0.5 ohm dropper resistor in one leg of the filament secondary to drop the filament voltage from 7V down to 6.3V. Ideally, you would want to use two 0.25 ohm in each leg of the supply, but come on, 0.5 ohm is miniscule compared to the power transformer's DCR. Worked like a charm.
4. Build a IXYS IXCP10M45 CCS and replace the film resistors on the 12AT7. I find that with the CCS

Gain is increased
Transparency is increased
Drive and also treble resolution are increased
The warm "euphonic" sound effect is reduced. To be expected, but I kinda miss it.
The miniscule amount of hum (only heard with ear 1 cm from driver) I had before is pretty much gone (increased PSRR, I guess).

I varied the current from 2mA to 4.5 mA but backed ff to 3.5mA . At this point, plate voltage is abotu 150V. I don't have a lot of B+ to play around with so I'm going to be conservative. At first glance, the higher current seems to give the amp a bit more drive and a "heavier" sound, whereas the lower current results in a "lighter" more airy sound. I'll verify this upon further listening.

Here's the new schematic:

Update: September 20, 2008 .
I occasionally noticed a little amount of "zzzzz" sound . It turns out there is a little blocking distortion action going on. "Kenpeter" suggested a couple of "fixes".I've tried the first circuit (http://www.diyaudio.com/forums/attachment.php?s=&postid=1607995&stamp=1221201218) The debuging saga is documented at http://www.diyaudio.com/forums/showthread.php?s=&threadid=129577

Here's a link on blocking distortion

Techpreservation - A great schematics resource

2008-07-19T09:46:00.001-07:00

This is a great repository of vintage audio schematics . Hard to believe that the information is free.
http://techpreservation.dyndns.org/schematics/

My line arrays

2008-07-10T16:01:00.000-07:00

For what it's worth, here's a thread detailing a budget open baffle line array build of mine from last year. I used cheap $3.00 foster wide range drivers (sadly no longer widely available) , cheaper Apex Jr tweeters and much cat 5 cable (yes, I'm cheap) crossed over around 5 KHz (lower would've been better, but I didn't want to risk incurring nasty tweeter distortion modes).

http://www.diyaudio.com/forums/showthread.php?s=&threadid=99960

This design (being open baffle) needs a subwoofer below 60 - 80 Hz (I use a Fitzmaurice TableTuba Horn Subwoofer) and the combo plays way better than the amount I spent on it. High efficiency is the way to go.

Impedance is about 6 ohm and efficiency is the mid to upper 90s.

12b4a amplifier

2008-06-18T15:34:00.000-07:00

I was bored, so I built a 12b4a single ended amplifier from my bottomless pit of unused electronics. Bias points for the outputs are roughly similar to Gaby Levinson's project listed at

I have an extra 12AT7 lying around which I used as a driver, resistor loaded. I plan to CCS the plates when I can. Cathode bias is around 1.7 V via a single red LED per channel. I (optional) added a 10 ohm series resistor on each cathode to enable me to verify bias. I'm right around 3 mA per channel, which is below what the LEDs can handle.

Transformers are 5K / 8 ohm transformers from an old SE 6BQ5 console for the outputs and a hefty low DCR (less than 10 ohm) power transformer from a fisher 800C . Rectification is UF4007 SS diodes bypassed by 1000V mica caps (o.1uF, IIRC). For what it's worth 12B4A tubes have a neat inbuilt slow turn on feature, so turn on nasties are minimized. The 12b4a cathodes are at 20V (24 mA).

All other passives were generic off the shelf components from Tanner Electronics, here in Dallas and the chassis is a gutted Intel 2U form factor router that I picked up for $3 at a surplus sale.

I didn't pay too much attention to cosmetics, this being a budget project, but I suppose I'll eventually make an attempt to make this amp more presentable given how good it sounds.

The sound is amazingly good for the 1.5W or so that it puts out. Not too much low bass (I blame the cheap OPTs for this) with an excellent mid bass and mid range. Very liquid sound that just sounds right. Highs are smooth without being excessively rolled off (okay, maybe just a little bit, but definately not in a old-school vintage sound way). I haven't even bothered decoupling the driver and output stages, or bypassing the electrolytics and yet, this amplifier sounds so "RIGHT" . These speakers take the edge right off my fostex full rangers and fill in the mid bass very nicely. Hum is pretty much non - existant even with ear to speaker. I used twin CLC filters, one for each channel to reduce the current load on each choke .

Probably best with speakers of real life sensitivitiy above 95 - 97 dB/W/m. These sound "so - so with your typical "shoe-box" 2 - way monitor. Maybe okay for an office, but definately won't show their full potential unless paired with high efficiency speakers. I'd really like to compare these to a good DHT 45 SET .

Update: September 20, 2008
the story continues at http://zobsky.blogspot.com/2008/09/12b4a-amp-version-2.html

Frequency measurements with ARTA

2008-02-06T11:56:00.000-08:00

Description
Here's a simple electret mic capsule / circuit I use for frequency response measurements, . .basically just a panasonic $2 WM-61A (chosen for its linear response) capsule mounted on one end of a hollowed-out ball-point pen and a 9V battery and a couple of other miscelaneous components hanging off the other. I taped this contraption onto a spare tripod and voila !! . This is fed to the LINE-IN (not MIC) input on my audigy 2 sound card, which has a flat enough response for frequency response measaurements. I use ARTA for actual measurements.

The only downside to this simple circuit is that it can't drive long lengths of cable (mine is a couple of meters long and works just fine).

The circuit

A sample measaurement

A simple loudspeaker measurement jig for ARTA

2008-01-13T16:02:00.000-08:00

Here's a redux of a very useful simple circuit that, when used with the ARTA LIMP software running on a PC, allows you to easily measure loudspeaker impedance curves, RLC values of passive components at various frequencies, and TS parameters of loudspeaker drivers. You should be able to do all this with the FREE demo version of ARTA.

It has saved me from the curse of Speaker Workshop, which is an extremely useful tool, but a real PITA to get going.

This jig is useful for low-power measurements. For higher power measurements, you will need some sort of protection devices on the PC Line-In sockets and also a power amplifier to drive the speaker. Regardless, the circuit above works, and works very well for what it does. I've ran it on a variety of drivers with my Audigy2 sound card and also the crappy on-board sound on my computer and the results obtained compare very favorably with the manufacturers specs and graphs.

The way it works is the PC line-out powers the driver under test via a series resistor of known value. The line-in connections act as voltage probes fore and aft of this resistor, allowing the software to determine impedance variation with frequency. There are some fancy jigs out there, but this one works well and costs literally nothing to build . If you're cheap / lazy like me, you can forego the switch and merely disconnect the driver when calibrating the jig (do this everytime you re-connect it). This is probably a better / cheaper idea as the contact resistance of a typical cheap switch can vary between 0.5 - 3 ohm, .. fairly significant when you consider that the typical driver has a nominal impedance of 4 - 8 ohm .

Also, I'd suggest disconnecting the jig when not using it, .. probably not the best idea to leave a loopback into the sound card long term.

You will need
1. 3 RCA sockets
2. One single pole switch, or whatever you have lying around that works. Try to ensure that it doesn't have too high a contact resistance.
3. One calibration resistor, . the exact value is not too important, as long as you know what it is. I used a 14.7 ohm resistor made up of multiple larger equal valued resistors in parallel to reduce the effects of resistor to resistor variation.
4. One pair of binding posts.
5. One plastic enclosure to build this contraption into.
6. Two stereo-RCA to mini plug cables a.k.a "I POD" cables

Note: sound card settings
Here's how my sound card is set up, as viewed from Windows Mixer . Your input and output settings may vary, depending on your specific hardware but try to note / check the following:

The important thing to ensure is that you select the correct Line-In input in the Recording panel.
Also, you may / may not need to mute the Line in on the Playback panel, as well as the Microphone in.
My Audigy 2 has a bunch of options and I had to experiment a bit initially trying the various inputs (some looped-back internally bypassing the calibration resistor:(.
If you have an Audigy type card, be sure to check the "record without monitoring option" . See picture below.
If you get a channel imbalance of 0.0 dB when calibrating, you probably have an internal loopback.
Once you get ARTA working, you may consider muting un-needed inputs / outputs .
Watch out that you aren't too close to sources of electrical interference (such as CPU fans) as you can pick up spurious 120 Hz interference on impedance graphs.

You will want to read the ARTA / LIMP manual for a full description of the procedure but it really isn't too tough. Basically
1. Connect the cables between the PC and the jig, the jig and the driver under test and set the switch to OFF . If you haven't built in a switch, just make sure the driver is disconnected from the jig.
2. Calibrate the jig (configure the value of the calibration resistor, set the correct reference channel, set the appropriate input and output devices on your sound card, and adjust the levels so you don't clip the input). When calibrated, the jig should indicate a SMALL difference in channel levels (say 0.1 dB or so). If you have a large imbalance (greater than 2 - 3 dB), something is not connected correctly. If you have no imbalance, the output is being looped-back to the input within the sound card . Check for the correct input and output settings on your sound card.
3. Set the switch to ON
4. Press the red record button and within seconds, you should have an impedance curve.

Here's an example (different specimen than the one used for T/S parameters further down this post):

Wasn't that easy?

5. Now, if you want to go further and determine the TS parameters, navigate to the Analyze / Loudspeaker parameters - Added mass method . Enter the DC resistance and the Membrane diameter (the diameter of the driver cone +1/3 of the surround thickness) and calculate the TS parameters. This will calculate most of the important stuff.

6. Now close this window, go back to the graphs and navigate to Overlay / Set as overlay. This establishes a baseline for the Vas calculation.

7. Add mass to the cone. The cheapest and easiest way I've found to this is to secure one or more pennies to the cone with small pieces of weather-stripping (light, easily removable and damp the coins). A U.S. penny's mass is 2.5 grams (on earth, at least). Here are the weights for some other US coins.

8. Now, run an impedance sweep again. You should see the resonant frequency peak shift lower. You want to see a decrease of about 10 or more percent. If not, you haven't added enough mass.

9. Stop the measurement and then navigate back to the Loudspeaker parameters - Added mass method window. Enter the total mass you had to add to the cone and re-calculate. If done correctly, you should see the Vas and a bunch of other parameters show up.

Here's an example of what I get for a cheap foster wideband woofer

Thiele-Small parameters:

Fs = 82.89 Hz
Re = 7.80 ohms[dc]
Le = 1115.28 uH
L2 = 437.31 uH
R2 = 12.76 ohms
Qt = 1.17
Qes = 1.47
Qms = 5.81
Mms = 4.89 grams
Rms = 0.438236 kg/s
Cms = 0.000754 m/N
Vas = 7.86 liters
Sd= 86.18 cm^2
Bl = 3.679200 Tm
ETA = 0.29 %
Lp(2.83V/1m) = 86.89 dB

Added Mass Method:
Added mass = 2.50 grams
Diameter= 10.48 cm

Compare this with the manufacturer's specs, not a perfect match but not bad, considering manufacturing variations, and the fact that I wasn't paying too much attention when testing this.

Foster 2422 264 00504
Paper cone, cloth surround wide band woofer.

8 ohm
87.3dB
Fs 80.7Hz
Vas 10 liters
Qms 4.267
Qes 1.375
Qts 1.040
BL 3.57
Cms 808.7 uM/N
Mms 4.81g
Re 7.2 ohm
Krm 1.155
Kxm 6.832
Erm 0.818
Exm 0.716
Sd 0.0094 sqM
Le 0.57mH @ 1kHz

Enjoy