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Post by dmontella on Mar 14, 2013 18:08:18 GMT -7
I have a dual woofer ib that has worked great for a couple of years. I recently moved the sytem from being mounted in a wall to the ceiling. Ever since doing this when I play bass rich music (ie reggae) the sub pops when volume is at a medium to high level. At low to medium levels it is fine. The noise definitely is coming from a driver and not the cabinet or surrounding structure. Everything is ver solid. Originally I thought that a driver may have blown. Tonight I was playing around with this and noticed that if i put moderate pressure on the cone of either driver the popping noise would stop.
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Post by ThomasW on Mar 14, 2013 19:37:14 GMT -7
I recently moved the sytem from being mounted in a wall to the ceiling. Ever since doing this when I play bass rich music (ie reggae) the sub pops when volume is at a medium to high level. At low to medium levels it is fine. Generally ceiling subs are further away. Ceilings aren't as stiff as walls. And most importantly standard in-studio amp settings for reggae bass guitar have 20 or more dB of bass boost. You need more/bigger woofers |
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Post by shoshaw on Mar 15, 2013 6:43:36 GMT -7
Ceiling locations usually have more open air behind them than walls. Your new install may be "more" infinite than your previous location. You may have less acoustic loading and; therefore, more excursion. Is it possible to loosely block the manifold with a blanket? It might be a good way to see if just a little bit of loading reduces excursion and eliminates the noises.
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Post by FOH on Mar 15, 2013 7:38:49 GMT -7
Generally ceiling subs are further away. Ceilings aren't as stiff as walls. And most importantly standard in-studio amp settings for reggae bass guitar have 20 or more dB of bass boost. You need more/bigger woofers +1 Ceiling locations usually have more open air behind them than walls. Your new install may be "more" infinite than your previous location. You may have less acoustic loading and; therefore, more excursion. Is it possible to loosely block the manifold with a blanket? It might be a good way to see if just a little bit of loading reduces excursion and eliminates the noises. +1 All good advice. I might add, and precisely what the previous contributions alluded to; it's quite likely the aberrant sound you're experiencing is driver bottoming. Every driver design employs varying bottoming characteristics. There's soft bottom designs and hard bottom designs, .. and everything in between. The soft bottom design, whereby the suspension (surround and spider) limits the excursion of the voice coil/former, from ever encountering the back plate. Some designs just don't possess the magnetic characteristics to achieve bottoming. Some employ magnetic "braking",...which counters the VC's movement at the extremes of it's travel. And finally, and seemingly all too common, there's the hard bottom design. This is the approach whereby the Xmax, and Xmech are essentially too close to one another. Each mfr may use different manners in which to define Xmax, but at Xmax or slightly past, the driver hits it mechanical limits, Xmech. When that limit is the VC former slamming into the back plate, it can easily create that exact popping noise you mentioned. It can be startling for sure, and it can easily cause damage if excessive in force, or frequency. By placing your hand on the cone, you're physically limiting the throw,..buffering the issue. Thomas is right, music styles such as Reggae have a spectral heavy LF style. As such, they're very demanding on the playback chain. Likewise, Showshaw is correct in stating the backspace loading your cones "see", may be much more voluminous than the wall loading, hence the ease at which the drivers now seem to hit their limits. Either way, yeah, you need more sub  Best of luck |
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Post by dmontella on Mar 15, 2013 17:08:07 GMT -7
I understand this all sounds strange, but please bear with me. I know just enough to be very dangerous.
Last night I reviewed everthing that changed and I thought that one key variable was that my setup might also be sending more low frequency energy to the amp (new processor/settings) I didn't think I had a clipping issue because the amps output power lights never went that high.
I took a stab at the possibility I had an impedence issue. (2 8 ohm drivers in parallel- 4 ohm load) I checked out a bunch of pro sound forums and reread the specs. My amp (Crown xls 402) is designed to work with 4 and 8 ohm loads. Apparently when you run mono input to a bridged ouput mode the impedence drops to 2 ohms. This would cause its protection circuit to create the popping noise at higher levels. I took the amp out of bridged mode and ran the sub on one channel and the problem is gone. Preliminary listening went great, although I think im going to take a look at rewiring it to use both channels.
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Post by shoshaw on Mar 18, 2013 5:19:00 GMT -7
When you run ANY amp in bridged mode, the output voltage doubles effectively doubling the output current. This looks the same as halving the impedance from the amp's perspective. It also means you're running 4 times the power! For sure, your XLS402 was not designed to drive a 4 ohm load while bridged. In your situation, you could have been overloading your amp or overdriving your speaker. Either way, I'm glad to hear you fixed the issue.
Your amp is rated for 300W into 8 ohms and 450W into 4 ohms. Rewiring to use both channels will give you more power, for sure. If you wire it that way and your ticking noise returns, then you know you were overdriving the speakers.
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