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Posts by cjwhitehouse

Interesting graph, Craig. It is unusual to see 6th harmonic distortion apparently dominate like that over 2nd/3rd. That would certainly blow any CEA-2010 stepped limits. It would be interesting to know what that sounded like.
I have actually crunched the numbers for all the old measurements (several hundred hours of CPU time on a quad-core machine). However, I have not chosen to publish them yet. The reason for this is that I took some advice offered by Earl to Keith Howard that the GedLee Metric squared correlated better with audibility than the straight GM value as documented in their AES papers. So I computed all the GM values on this basis. Having now done considerable testing on the...
I believe the idea of the standard was to try and get away from manufacturers quoting inflated wattage numbers as a means of conning people into thinking their subs gave the best performance. By encouraging them to use a common standard, it was hoped that there would be more honesty and it would make the decision easier for Joe Public. It would seem that there is little appetite for such honesty in the industry. Which is disappointing, if understandable.The trouble is, it...
I refrained from further argument in that thread because it's Ilkka's thread and I don't like peeing in someone else's pool particularly. However, I thought it might be useful to throw in a few points for discussion and leave it for others to debate. Here's a few more for consideration. Take-up of the standard by manufacturers. Polk Audio, who were involved in the development of the standard, undertook to publish these numbers for any new subs they released. As far...
Oops! AV Talk has never tested a BFD. We have conducted tests on the SMS-1 to confirm a number of things: 1) Bass rolloff with different subsonic filter settings. Ilkka also confirmed this issue and that the BFD had much better bass extension. A software update to the SMS-1 is in production which may well fix the problem. We will have to wait and see. 2) Graph plotting accuracy. It had been claimed that the SMS-1 graphs were a few Hz out, especially at the bottom end. We...
I think you have this back to front. A setting of 1 is minimum servo-feedback, allowing more output at the expense of more distortion, may be preferred for Theater use. Setting 8 is maximum servo-feedback, reducing output and keeping distortion lower as one might choose for music use.
We are getting well off the topic of this thread but anyway... What is perhaps not generally appreciated is that nonlinearity in a system (be it amplifier, transducer or whatever) will give rise to harmonic distortion when presented with a single tone. When presented with two or more tones, that same nonlinearity will give rise to intermodulation distortion. In the case of loudspeakers, the Force Factor, Inductance etc that cause harmonic distortion also cause...
Amplifier slew rate in respect of subwoofer performance! Boy, that is a new one!
Just for the record, we did take the higher sweep. As Ed said, the fuse blew.
The smoothing used is 1/6 octave. If you really want to see what difference it makes, I have loaded up the unsmoothed version of the PB13-Ultra frequency response in 20Hz tune as an additional attachment in the same post as the normal smoothed response. You'll have to click on the attachment to view it. Most of what you see is just background noise rather than giving you more accuracy.
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