wohnzimmer heimkino bilder
hi there this is marius from hamburg (germany). before i can use the prize i won in the german magazine hobby hifi, which i mentioned in the previous video, i want to examine what this stuff is capable of. therefor in the next video i'm going to measure the thiele small parameters. in the video after that
i'm going to simulate an enclosure with ajhorn using those parameters. hobby hifi also calculated these parameters in my last video i already showed those pages. i now only received a similar but not the exact same driver which hobby hifi tested. that's why there is the possibility
that parameters differ because of tolerances at production. it may also happen that my results differ because i use a different measuring technique. hobby hifi measures the old school way, manually using a sine generator and a multimeter. i use a pc and the software limp
of the packet arta made by the croatian professor of electrical engineering doctor ivo mateljan. the necessary cable for measuring i built following the instructions in the german magazine hobby hifi no. 5/2009. in this video here i show the preparation. before i can measure
i let the driver burn in for 24 hours. the display on the left shows the overall voltage. here i had the idea to switch to the frequency counter. the range is set to kilohertz, so it shows 15 hertz. there is a constant discussion among some experts if this is really necessary. i myself definitely noticed
slight differences in parameters of drivers before and after burn-in. this seems fully reasonable to me. elastic parts become softer after some time. that's why also parameters become â€œsofterâ€. the german company visaton did some research (only available in german) about the effects of that topic
and came to the conclusion that the differences are very small. they were about one decibel. for the reason that my driver does not feel lonely in my basement i connected it together with a subwoofer driver of a colleague and a low-cost woofer.
i admit this is a strange team. after the measurement comes the decision if the enclosure i already developed using the parameters hobby hifi appraised can stay as it is or has to be changed. the candidates of this test:
the img stage line sp10/250pro, a pa woofer with a nominal diameter of 10â€ (25 centimeters), current price in germany 130 euros, the dyh-810 of conrad electronic which i bought back then for 8 euros, current price about 11 euros, also available at pollin electronic for 10 euros;
nominal diameter of 8â€ (20 centimeters) and the hifonics zeus hz 12, a car subwoofer, with a nominal diameter of 12â€ (30 centimeters) which i borrowed from my colleague. this driver is obsolete by now but i found out it cost about 250 euros in germany back in 2003.
my colleague asked me: â€œi have a 12" woofer lying around that i want to use in my garage. what would be the best size of an enclosure for it?â€ â€œthat depends on its parameters.â€ â€œi dunno. doesn't have to be fancy. i just want a nice boom box.â€ â€œjust bring it over.
i'll measure the parameters. otherwise it won't be worth it.â€ so there still is the question: why the low-cost driver? the production and parameter tolerances must be huge. it might be hard to find two which are nearly the same. indeed i own two of those and i measured them about two years ago.
the tolerances were big. the weights of the membranes seem to differ 25%, i.e. 19.7 and 25 grams. but i am interested if the parameters changed over time. i want to use them as passive radiators for the subwoofer i am going to build with the woofer of img stage line â€“
that's at least the plan. then the exact parameters of this cheap vibrating card boards are not so important. to reach the wanted tuning frequency i anyway need to find out the right amount of mass to add thought several rounds of measuring. here you can see the test setup
in my basement. driven by a subwoofer amp of up to 400 watts by reckhorn and a dvd player playing a cd with a 60 minute long sine at 15 hertz in a loop. i connected my multimeter to measure the voltage at each driver. hifonics and conrad are
connected in serial. together they are connected in parallel to img stage line. i did not film when i measured the current which was 0.74 amperes in total. those of you who are familiar with the calculation of instantaneous power p(t)â =â u(t)â·i(t)
can now figure out that my amplifier might even be bored, but it is already warm enough that i don't want to touch it for a longer time. but i don' t think it is already warm enough to roast an egg. why can't we see the motion of the cone correctly the whole time?
here a short lecture in applied electrical engineering: the video is recorded at 30 fps, the cone swings at 15 hertz. due to inaccuracies in timing the camera does not capture the the exact same position of the cone in every frame. so we see here what is called a beat.
to be exact we see the alias effect because i did not meet the nyquist-shannon sampling theorem. i used a sampling frequency which is exactly twice the signal frequency. for a better video capture i should have used a lower frequency for burn-in.
these three fellas are now wobbling in my basement for 24 hours. a mere 24 hours later i am going to measure them with a stepped sine. but that's another story in my next video. bye then & have a nice day! epilogue: the final joke
how do you recognize a cheap driver? comparison with the more expensive ones. their frames also have resonances but they quickly fade. here again the difference. those resonances add to your music. do we want that? but if it doesn't work anymore
it can start a second career as a dinner bell.