Don Wilhelm wrote:
"Any radio will show its true audio traits if it is fed into a good wide-range speaker (or amplifiers and speakers)." I strongly agree, but theoretically a speaker with an intentionally limited response (as opposed to a cheap speaker) can to some extent cover up some problems in the radio's audio as revealed by the good wide-range speaker. What I haven't seen mentioned in this discussion is that if you want a good wide-range speaker, e.g. for critical examination of your radio, or for permanent use if the radio has good audio, it is not enough to buy some specific speaker known for good quality. Any given speaker can vary enormously in its response curve depending on how it is placed in relation to walls and other equipment. It is not enough to follow some instruction sheet that came with the speaker. I find that with quality speakers it is necessary to perform some kind of response measurement during installation. This is not as straightforward as it may seem. Even good speakers tend to have response variations with frequency, but if you look at measured response diagrams, they are for anechoic chambers. In practical installations you will encounter all kinds of room resonances that cause bumpiness even with the best speakers. The objective then cannot be flat response, but a flat average response over limited frequency ranges, and balance between those ranges. My favorite way of testing for that is to use a series of warbling test tones, each of which covers a limited range of different frequencies, as produced by an old test CD I have (disques PIERRE VERANY PV 784031 CA 803 "DEMONSTRATIONS TESTS"). On the detection side I use a cheap RS sound level meter. It is not perfect for the highest audible range, but the room resonances happen mostly at the lower frequencies anyway. You get an average reading during the warbling, and this is much faster than measuring at high numbers of individual frequencies. Warning: when you have moved the speakers for the flattest possible response, they are not likely to be where you would like them from a decorator's point of view! 73, Erik K7TV ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
