To expand on GM's post, let's take the lowest figure he posted of 96. Yours are 90. A good woofer will be as loud with 75 watts as yours are with 300. Crap woofers will kill your headroom as the amp is working harder.
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To expand on GM's post, let's take the lowest figure he posted of 96. Yours are 90. A good woofer will be as loud with 75 watts as yours are with 300. Crap woofers will kill your headroom as the amp is working harder.
That, or use four 90 dB speakers at 4x the space, cost in lieu of just one 96 dB speaker.
GM
i had a pair of altec 421-8lf's that measured with the 'woofer tester2' at 104db/watt
At the one meter distance? 104 sounds high for those. In an A7 box the horn should be worth maybe 5 db.Quote:
Originally Posted by valhallax
with the woofer tester one places the woofer in a stand and it measures the parameters. we set up for a gig, they were in a-5 cabs, after several hours of the drummers dm pro trigger rig, the eff was down 6 dbs. those were pre sub days...
ive also rea where early woofers tolerances were so tight, to gain effeciency, that the coils would lock up after getting hot
The old coils were not heatsinked well. If overpowered they go 'out of round' and can rub or lock up.
But the measurement has to be taken SOMEWHERE, ie at some distance from the cone. If you measure a foot from the cone, you will need to knock off 4.5 dB or so. Otherwise you can not communicate with others, and your box designs simulation will be off. TS parameters efficiency is at one watt/one metre, and all box design programs I know of use that standard.Quote:
Originally Posted by valhallax
Doesn't the woofer tester just calculate by using a comparison sweep? It doesn't measure efficiency as far as I know. It makes an educated guess.
the only 'one watt at one meter' physical tests were done with the bf titan 48s i built and ran several woofers through. took awhile setting up the test rig, learned a little tho
The woofer tester I have (DATS), does impedance sweeps, and then calculates t/s params from that. You just connect it straight up to the VC, and it generates the sweep, and measures the drivers response via electrical feedback from the VC. Here's a sample display of a t/s param measure I recently did on an Altec Model 14 woofer:
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You're correct OG, that it does not calculate efficiency, rather you have to supply that in order to get at Vas. Or there are several other methods to get there as well (added mass is a typical one). This particular test kit also has a signal generator, oscilloscope, and L/C/R tester included... very handy. I recommend it.