[teluan]

Help...I am confused. My subwoofer the David 303 D-Box makes a sharp popping sound every time I listen/watch the THX metal sphere splash screen explode. Movies like the latest Star Wars Trilogy have this THX splash screen as well as many others like Aliens and others that I just can not remember right now All of them cause my sub to make a very load POP sound. The only other place this occurs is in Star Wars Episode II, when the Queen Amidalia silver ship flies over in the opening scenes.


Anyways, this pop occurs at almost every volume level other than REALY quite. I can really crank the sub while watching the movie with no pops...just this logo and the one spot in Episode II.


Any ideas what would be causing this? Could it be a complex frequent that only THX certified subs can handle?

 

[thebland]

I had 4 THX subs in my last system...they would bottom out and stress on a regular basis when stressed at high levels. I had to go non-THX to get the output I needed!

 

[kgveteran]

This has become more common than not. That intro is sub bass on steroids. Your subwoofer cone has reached its max output and is clipping.It sounds like a mechanical clip which means the cone goes out too far and slams back into the back plate of the motor structure. I think you will see more designs use multiple drivers and multiple amps to avoid this in the future.

 

[Paul Scarpelli]

Quote:

Originally posted by thebland I had 4 THX subs in my last system...they would bottom out and stress on a regular basis when stressed at high levels. I had to go non-THX to get the output I needed!

If my memory serves me correctly, you had JBL LE14H 14" drivers in ported enclosures...either Fosgate Audionics or Citation, right? They had a resonant frequency of around 38 Hz, and as good as they sounded, they would "unload" below that frequency and sound like ass. (Technical term...) Any low frrequency at a moderate level would cause them to make distressed sounds.


They were nothing compared to your current setup. Have you detached a retina yet?

 

[Lord_Magnepan]

Well i agree with you all But my last 2 THX subs had no problem handling the splash screen ;-)


But it looks like you need another subwoofer.

 

[thebland]

Quote:

Originally posted by Paul Scarpelli If my memory serves me correctly, you had JBL LE14H 14" drivers in ported enclosures...either Fosgate Audionics or Citation, right? They had a resonant frequency of around 38 Hz, and as good as they sounded, they would "unload" below that frequency and sound like ass. (Technical term...) Any low frrequency at a moderate level would cause them to make distressed sounds. They were nothing compared to your current setup. Have you detached a retina yet?

Good memory, Paul. I had 4 of the Citations and they were easy to stress.


My retina is still attached, and fortunately, so is my room!

 

[teluan]

kgveteran notion that the cone has reached it maximum excursion and is hitting the back of the magnate seemed to match with the popping sound I am hearing so I did a little experimenting.


My sub, like many home theatre models is a ported enclosure. By temporality blocking the port, I was able to in effect create a sealed enclosure. This of course added further "air pressure" resistance to the cone especially when the cone is farthest from its neutral position. This added pressure prevented the cone from traveling too far back and hitting the magnet. The only down side is volume is reduced by doing this as free air cones are not designed for this additional pressure.


I can live with the pop as it only occurs in 2 places as described in my original post and the sub really rocks my home theater room and entire house without any noticeable distortion 99.999% of the time.


Long term I may replace the cone with a similarly matched car 12" sub that has a long excursion cone. Car subs "seem" to be a lot tougher and ready to be pumped hard when compared to home subs at the same price point ($300 home sub is okay, a $300 car sub with amp will break the sound barrier). Any one tried this? Any comments?


I had 2 subs back in the mid 90s in my CRX that had a 2 1/2" excursion and really moved that far when cranked. So much so that on a cold Canadian winter night (-35) they shattered my back hatch windshield. ƒº If I can break on of my home windows in a similar way¡KI will be smiling ear to ear (and our $200 to $300 for a new window).