xgsjx Posted August 4, 2012 Share Posted August 4, 2012 After reading another post about a chap (AMPEG) who had blown a driver, I thought I'd have a wee read about & came across this... [quote] Some famous US speaker makers (e.g. Bose and JBL) have discovered how to prevent speaker failures and dramatically improve the input power ratings at the same time. Impossible you say? Actually, it is dead easy. All you need to do is fit a low voltage halogen light bulb in series with your woofer - chosen so it has almost no effect at the 1 watt level where efficiency figures (dB per watt) are always measured and quoted but [i]lights up[/i] brightly and limits current flow when the power input is enough to threaten the woofer. This works because the resistance of the filament typically varies by around 1:10 from cold for full brightness, so when hot, the series resistance is high enough to protect the speaker. If higher than rated system power is ever applied, the bulb simply burns out rather than the woofer!!! Using this approach, a 4 inch 20 watt, 2 ohm wide range driver becomes rated at 80 watts in the Bose 101. Similarly, a 6.5 inch, 30 watt, 4 ohm woofer accepts 160 watts of "nominal" input in the JBL Control 5. [[url="http://sound.westhost.com/articles/speaker-failure.html#ref"]3[/url]] Pure genius or a dishonest but cunning dodge? Seems all is fair in a game where reality has been rendered meaningless.[/quote] Anyone know if it works & if so, why don't more cab manufacturers do this? Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted August 4, 2012 Share Posted August 4, 2012 Sounds like BS, the bulds are part of the crossover for tweeter protection, otherwise the same effect happens from the voice coil itself and is called power compression, and is responsible for some failures, where the increasing impedance drops the volume and the volume control is turned up to compensate, making the issue worse.. The 'bose' part is the giveaway. Quote Link to comment Share on other sites More sharing options...
KingBollock Posted August 4, 2012 Share Posted August 4, 2012 When I was a kid I was given a pair of 1x12s, each in it's own ported cab, and each one was huge being about 36x18x18 inches. Anyway, I installed a 12v bulb into each of them so that the ports glowed when playing Bass through them. It didn't make any difference to the sound and nothing died. I didn't really know what I was doing, I just liked pretty lights and messing about with electronics. Quote Link to comment Share on other sites More sharing options...
xgsjx Posted August 4, 2012 Author Share Posted August 4, 2012 Here's a video of the JBL one... http://www.youtube.com/watch?v=OQo_TUhvUzU I was hoping one of them would pop pretty early on! Quote Link to comment Share on other sites More sharing options...
verb Posted August 4, 2012 Share Posted August 4, 2012 In issue 8 of Bass Gear Magazine there is a review of the Acme Sound B-112 cab and it mentions that the builder had previously used light bulbs to protect the driver n tweeter but has now changed to polyswitches? Quote Link to comment Share on other sites More sharing options...
Bill Fitzmaurice Posted August 4, 2012 Share Posted August 4, 2012 [quote name='xgsjx' timestamp='1344118987' post='1760188'] Anyone know if it works & if so, why don't more cab manufacturers do this? [/quote]It does work, on tweeters, and many manufacturers use bulb protection. It does not work with woofers, the current flow being far too high. The only sure protection for woofers is an active limiter. Quote Link to comment Share on other sites More sharing options...
xgsjx Posted August 5, 2012 Author Share Posted August 5, 2012 Cheers. When I first read about it, I was envisioning a 60w bayonette type pearl bulb in the cab to light up the port ala KB stylee! Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.