Members mental-mike Posted September 28, 2009 Author Members Share Posted September 28, 2009 Good question. Mental-Mike -- Fortunately for you, the Pro Rider basket is fairly easily user replaceable. If you could entertain us by snap a few pictures of the spent unit at time of replacement, we can have a little forensic discussion on the actual failure mode of the drivers for the benefit of those here. We'd appreciate it. Based on the narrative it sure sounds like there is both a mechanical and thermal component to the failure Yeah I'll take some photos..taking a trip to get new 18's {only blew the one} but better safe than sorry, we'll replace the other as well. It's kinda funny looking back, we're a cover band..we play 3 one hours sets...3 songs in the 1st is when the guitar player looked at me and that's when I got the "smell" it was that "something ain't right" look guitar player said the 18 was smoking....lol ironically, we play "burning down the house" from the Talking heads...we should have went into that song... Link to comment Share on other sites More sharing options...
Members soul-x Posted September 28, 2009 Members Share Posted September 28, 2009 Nice pic but it also warrants some discussion. This shows excursion for steady-state sine waves and it looks like the excursion goes down from 55Hz to 35Hz. That is because at the port tuning frequency, the cone hardly moves and all the air is movement is in the port. However, that's really only true for sine waves that last a long time. It takes a considerable time for the box and the port to build up the resonance. You will see much higher excursions during the onset of a sinewave. Hence anything with real transients in it (for example a kick drum) will produce significantly higher excursion near the port tuning than this picture would predict. Yup. For sure Originally, my intent was simply to show what the driver can be doing even well above the tuning frequency to another poster. FWIW, I think it's just too much power without either reasonable processing or a careful operator. Link to comment Share on other sites More sharing options...
Members agedhorse Posted September 28, 2009 Members Share Posted September 28, 2009 Nice pic but it also warrants some discussion. This shows excursion for steady-state sine waves and it looks like the excursion goes down from 55Hz to 35Hz. That is because at the port tuning frequency, the cone hardly moves and all the air is movement is in the port. However, that's really only true for sine waves that last a long time. It takes a considerable time for the box and the port to build up the resonance. You will see much higher excursions during the onset of a sinewave. Hence anything with real transients in it (for example a kick drum) will produce significantly higher excursion near the port tuning than this picture would predict. Good information, thanks. While it's easier to focus on steady state, mechanical inerta and momentum can lead to false conclusions and inadvertant propensity for damage. This is especially true in feedback systems with slow feedback response. A speaker cabinet is in some ways similar to this. Link to comment Share on other sites More sharing options...
Members Unalaska Posted September 28, 2009 Members Share Posted September 28, 2009 The EP4000 is nothing more than a rebadged EP2500 amp. Actual specs after looking thru the manual put the 4 ohm rating at around 950 @ 4ohms (can't remember THD or 1K vs 20-20k, that is a BIG difference too!). run these amps in stereo, use a crossover, nuf said. Link to comment Share on other sites More sharing options...
Members agedhorse Posted September 29, 2009 Members Share Posted September 29, 2009 The EP4000 is nothing more than a rebadged EP2500 amp. Actual specs after looking thru the manual put the 4 ohm rating at around 950 @ 4ohms (can't remember THD or 1K vs 20-20k, that is a BIG difference too!). run these amps in stereo, use a crossover, nuf said. Oh good grief, a "specification" upgrade. Well, the race to the bottom continues in the "power" market. Link to comment Share on other sites More sharing options...
Members Mogwix Posted September 29, 2009 Members Share Posted September 29, 2009 The thought behind it was using one channel to run the SP4s and the other to push the sp118s...then he finally went with 1 4000 to run the SP4's left/right and use the other 4000 to push the sp118s....didn't think it would hurt to push it in bridge mono the "theory" behind the thinking was, not having to drive the amp on full, like the old one....figured since it was only running about 1/2 on the level it wouldn't be bad.....guess that theory is out the window now Good grief, at least you're learning! I've seen so many guys smoke their amps and/or their speakers and go the opposite way thinking they need more power. Keep in mind that there's no such thing as underpowering as far as speaker damage goes. Damage from "underpowering" is a result of poor user judgement and unreasonable expectations of what their speaker can do. Damage from overpowering is obvious and just plain silly. It's entirely possible to safely drive a speaker with an amplifier that's much too large for the speaker, it takes an understanding of your system's limits and proper calibration (limiters, crossovers). Don posted specs of the Versarray rig they were running, and I remember a ridiculous amount of amplifier power going into each sub... although Don had the rig properly calibrated to run that kind of power safely, as well as an understanding of the capabilites of the system components and also an understanding of how the entire system works as a whole. Link to comment Share on other sites More sharing options...
Members Unalaska Posted September 29, 2009 Members Share Posted September 29, 2009 about a year ago behringer dump a large amount of EP1500 and EP2500's on the market locally. I ended up buying a couple 1500s very cheap NIB. One has a slightly noisy fan, the specs are in between a 1450 and 850. Both run horns in a triamp amp rack. heavy f--kers Link to comment Share on other sites More sharing options...
Members tlbonehead Posted September 29, 2009 Members Share Posted September 29, 2009 Oh good grief, a "specification" upgrade. Well, the race to the bottom continues in the "power" market. And they have a lightweight digital switcher now too! Link to comment Share on other sites More sharing options...
Members Taterworks Posted September 29, 2009 Members Share Posted September 29, 2009 If the subwoofer was smoking, overexcursion isn't your issue - it's thermal overload, plain and simple. If you pulled the drivers out and their soft parts were ripped to shreds, or if you've been blowing dust caps off, or tearing cones, then overexcursion is your bastard. Also, you can usually hear overexcursion even if the subs aren't a-poppin' -- their output will begin to sound like, "Ughh, ughh, blughh", as the driver is driven outside its linear range of excursion. Overexcursion usually only becomes a problem when the appropriate lowpass filter is not set. This hasn't been asked yet, but how much compression are you running on things like the bass guitar, kick drum, and left hand of your keyboards? If you're running a mondo-compressed bass guitar that likes to sit on one note for a while, you could be dumping a signal into your subs that's much closer to a sine wave tone (RMS voltage is higher) versus a typical 'music' program (where high-level stimulus is applied for only a fraction of a second). More compression can sound like you're getting more volume, but in a system where the amps are capable of much higher unclipped output than the subs can handle continuously, too much compression on bass instruments can spell death for sub drivers. The rule of thumb wherein speakers are powered with twice their RMS power is only assuming that you're feeding a music-type signal to them, where you need that extra un-clipped dynamic range to avoid amp clipping when big transients come through (like a kick-drum hit). Link to comment Share on other sites More sharing options...
Members agedhorse Posted September 29, 2009 Members Share Posted September 29, 2009 It's entirely possible to safely drive a speaker with an amplifier that's much too large for the speaker, it takes an understanding of your system's limits and proper calibration (limiters, crossovers). Don posted specs of the Versarray rig they were running, and I remember a ridiculous amount of amplifier power going into each sub... although Don had the rig properly calibrated to run that kind of power safely, as well as an understanding of the capabilites of the system components and also an understanding of how the entire system works as a whole. And IIRC, Don had a subwoofer accident too, that damaged a lot of drivers. {censored} CAN happen, even where the system is well set up. I'll bet the (retail) repair cost for that accident exceeds what many club bands have in their PA's too. Link to comment Share on other sites More sharing options...
Members agedhorse Posted September 29, 2009 Members Share Posted September 29, 2009 If the subwoofer was smoking, overexcursion isn't your issue - it's thermal overload, plain and simple. It's not this plain and simple actually. Here's a couple of examples of where this is not true. 1. Overexcursion causes the VC to exit the gap but becomes hung up on the pole piece or return plate edge and sits forward outside of the magnetic gap. The VC now looks like an air core coil (inductor) with a DCR of about 5 ohms. At low frequencies, the DRC dominates and the amp drives the coil (without and conductive cooling) and it smokes. The thermal damage was a direct consiquence of mechanical damage. 2. The driver is driven very hard and mechanically the winding height is not all that long resulting in a relatively short Xmax. The coil spends a lot of time exceeding Xmax and the conductive cooling effect of the pole piece and return plate is no longer very effective. The impedance also decreases due to the VC outside the gap more than it's inside which also increases power delivered to the speaker. Both cause the speaker components to fail thermally even thoughthe primary cause is mechanical in nature. 3. Thermal and mechanical damage often occur together. When disassembling a speaker with thermal damage, close examination often reveals the same telltale symptoms of mechanical damage such as cone edce to surround damage, cone neck damage, spider fiber damage, paper fatigue, surround fatigue, imprinting of the grille in the surround (or rubbing marks in the cone apex) etc. Which acme first doesn't really matter because once you have the mechanical damage, the thermal damage doesn't much matter does it. Link to comment Share on other sites More sharing options...
Members Shaster Posted September 29, 2009 Members Share Posted September 29, 2009 Well, the thought behind it was this....He was under powering the SP4 2-15s and finally blew the amp for that, it gave us yrs of good shows, so he got a "deal" on the euroamps....2 4000's for a few hundred bucks. The thought behind it was using one channel to run the SP4s and the other to push the sp118s...then he finally went with 1 4000 to run the SP4's left/right and use the other 4000 to push the sp118s....didn't think it would hurt to push it in bridge mono the "theory" behind the thinking was, not having to drive the amp on full, like the old one....figured since it was only running about 1/2 on the level it wouldn't be bad.....guess that theory is out the window now Yes, I suppose cheap available power produces excess, the way that cheap available food does. I trust that you now get the concept that those pots on a power amp act more like attenuators, than volume controls. As many have stated, turning your amp controls down to 1/2 doesn't mean that you've cut your amp's power in half - the full power is still there, waiting for some event, planned or not, to cause a mess. Lots of suggestions here on how to avoid the problem in the future, starting with not bridging. Good luck, and I hope you're rocking with two subs again soon. Link to comment Share on other sites More sharing options...
Members spsounds Posted October 2, 2009 Members Share Posted October 2, 2009 the sp118 dosent even handle anything under 50 hertz. Why we moved away from it. Link to comment Share on other sites More sharing options...
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