We can say without a doubt that this test of speaker cables is the most intensive test Alpha Audio has done to date. We have invested a tremendous amount of time and energy in this comparative test. We have also acquired two new, beautiful measuring devices to carry out this test. And all this to determine once and for all if there is a relationship to be made between measuring and listening. Whether we succeeded you can read in this mass test of no less than twelve speaker cables.
We’re starting to build up a serious arsenal of measurement equipment at Alpha Audio: a Prism dScope III, a versatile Rigol digital scope and 60 MHz function generator, and a Sourcetronic LCR meter. Then there are many special adapter plugs, measuring cables, dummy loads, variable resistors and other accessories.
The reason we invest in this is twofold: we want to know if a manufacturer communicates honest specifications and it is very interesting and educational to (try to) make a link between objective measurements and subjective listening tests. Because often we hear differences, but are they measurable? And explainable? And the same applies the other way around: for example, we measure interface jitter, but is it really audible? Establishing those relationships has become almost your author’s mission.
Speaker cables… the test procedure
There is much debate about cables. Do they actually do something positive to your sound? Is it all nonsense? Should you invest in a decent (speaker) cable? Or can you just use coat hangers.
Without a doubt, we hear a difference. But can we prove it in a blind test? To find out, we’re going in completely blind. At least: fellow authors Martijn ten Napel and Yung Lie are going in blind. Your author has measured and sampled all cables and is therefore no longer objective. His only task on the listening day is to change the cables and drink coffee…. ah, well: someone has to do that.
Yung and Martijn both receive a piece of paper on which they write down their findings. We use defined characteristics (detail, timbre, imaging and overall feel of the cable). Just like the switch test. Your author has created a top three cables from the measurements. Yung and Martijn are going to do the same, so that afterwards we can also see if the best measuring cable is also the best sounding cable.
Measurements were taken on a Sourcetronic ST2829A LCR meter (20 Hz – 300 kHz, medium speed sweep at 2.8 Volts). A Rigol digital scope and function generator was also used to send signals through the cables (20 kHz square wave at 2.8 Volts rms). And the Prism dScope III was used as a spectral analyzer and response measurements of the speaker cables.
The Prism dScope has again proven its flexibility. What a fine device that is. With the dScope spectral analyzer you can easily map the effectiveness of the shielding. And the sweep functionality of the Prism flawlessly shows what a cable can do in the chain.
You can find most of the set-ups in the photos. But to explain one thing or another…. The Sourcetronic is largely automated. For all tests except the capacitance measurement, the cable is shorted to our ‘cable panel’. Between each change of one we calibrate the meter again to make sure all measurements are correct. This setup is pretty bulletproof we have noticed. The only important thing is that we place each cable the same way and calibrate in between. Know that the graphs/measurements are logarithmic. That is why there are more bumps an dips to be seen at the beginning of the measurements; the resolution is much greater there.
For the noise test we took a 19V / 3A switch mode adapter and connected it to the 4 Ohm dummy load. This way a constant current flows. The speaker cables are shorted at one end (source) and connected to a 4 Ohm dummy at the other end (speaker). From there, measurement cables also go into the Prism.
Then we placed the adapter close to the cable (equal distances). This way we can test shielding. After all, if the spectral analysis – set to 256K FFT for optimal accuracy – does not change, no noise is picked up. Without fail, this test gave surprising results…. It is important to realize that cables also pick up noise without the adapter next to it. Also, they are not all measured on the same day. So look especially at the difference in noise.
The cable response measurement was done using a Bryston ProPower power amplifier (very stable) and a Teufel Definion 3S monitor speaker (average difficult speaker). We also used a dummy load to see what the differences were in response. The Prism feeds a sweep to the Bryston which sends the signal through the speaker cables. So the cable goes into either the Teufel Definion or the 4 Ohm dummy load. At the same time – either from the speaker or the dummy load – a measurement cable goes into the Prism. That then produces a nice little graph. We have put the data in one overview at the end of the article. Perhaps unnecessarily: measurement cables are kept as short as possible in all cases.