Am I hurting my subs?

[SomeGuyInPDX]

System:stock HU, LOC, Audiocontrol EQX, Orion 2350gx running 2-15"L7's in stereo at 4ohms, sealed box, crossed at 80hz.

Symtom: With my trunk open I can turn the volume up to 1/3 volume and the bass is clean and low. If I turn the volume up beyond 1/3 the woofers start to sound distorted(1/3 is still pretty dam loud). BUT! with the trunk closed I can turn it up to well over half volume and it still sounds clean and deep, but I know that at above 1/3 volume, the subs must be distorting like hell inside the trunk. It seems that the trunk is physically filtering out the distortion like a bandpass.

I have noticed over the years the same thing with some car audio subwoofer setups. When sitting in the drivers seat the bass is smooth and deep(sounds great). Then when you open your trunk/hatch your woofers are "farting". But they sound great from the cabin and a block away when the trunk/hatch is closed. When I say farting I dont mean "bottoming out", but they definetly are distorting. This has been most noticeable to me with bandpass enclosures. With the bandpass's if you were to listen to the speaker not being physically crossed over by the box, it is horibily distorted. The enclosure seems to be physically filtering out the distortion. Is this whats happening?_ Or do I have it all wrong?_
I'm trying to find out, if me and others are hurting our subs in this situation.
Thanks Matt

[manuelbauwens]

You are right, your subs are distorting but your trunk/car acts as a second cabin so you get some sort of bandpass enclosure, and it is known that bandpass enclosures can "hide" distortion.
Car subs can handle some abuse, but in the end, with too much distortion, they will burn anyway...
You best check that your system is matched up, that your amp is not too weak for your subs, and that your gains (preamp/amp) are correctly set, eventually you can also play with the highpass filter (subsonic) for your subs.

[Perry Babin]

There are likely several things happening.

There is a bit of low-pass acoustic filtering preventing you from hearing the clipping when you're inside the vehicle.

The SPL is lower with the trunk open so it's easier to hear the distortion. I'm not sure what the threshold is but at about 90dB, the human ear begins to overload (probably different at various frequencies) so it's more difficult to hear distortion at higher SPL (when the trunk is closed). The same affect can be seen by listing for distortion in the vehicle (full range) and leaving it at the level just before you can hear distortion... then walking away from the vehicle. When you get about 10 feet from the vehicle, you will likely hear a lot more distortion than you did when in the vehicle. This may be a form of 'masking' but I'm not sure that they're the same.

The woofers are likely being driven with nearly square wave signals at the highest listening levels. If the woofers are rated for 2x the rated power of the amp, they will likely survive. If they're only rated to handle the rated power of the amp (assuming that the max clean power is very near the rating), the speakers will likely fail if driven at the maximum level for long periods of time.

[AKHeathen]

well, one thing to factor is the loading and tuning of your enclosure and how it relates to your trunk. if it's built and tuned for your car, then it is not going to sound good once that changes, and isa-versa. if it's not built for the trunk, like a house speaker, or something else, it is not going to perform well in the trunk. not quite sure how it's set up, but i do know l-7's well..... well, up to more recent models. i haven't messed with any made in the past few years. however, just which models are they @ s4 coils? how is it set up? are they still 1krms? i know you are just feeding them about 300-350each atm, but they can get loud with little power, however, they do not sound the greatest when set-up for higher output. likely you are hearing more due to the un-developed wave. what generally happens, is you want the wave to develop in the front, however, in the middle of the wave you don't really get the differential, and you ideally want around 10' for it to do so, though there are different factors to work around/with that. this is why you usually get the best response from a 'drop-in" trunk box by firing it at the rear of the trunk, i suppose there are many things that could be effecting what you experience, but i would have to know how it's set up to do more than speculate. also, is that amp stable below 4ohms stereo?

[SomeGuyInPDX]

AK, I pulled my L7 box out the other day, but I am running basically the same thing currently. Drop in sealed box(subzero). 2-15" Kicker C15"s? I think (The oldschool round ones Credence Speakers, Inc.: CS154SV Sealed boxes 1.0 - 2.5 cu ft; Ported boxes 1.5 - 5.0 cu ft) facing backwards. Amp gains are almost wide open.

[AKHeathen]

oh, with the thin concave cones? or the cv series? either are nice. how much cu. are you giving them?

[SomeGuyInPDX]

I think they are the CS154SV concave cones
I believe its around 2.2-2.5cu per sub. sealed
Amp is running in stereo @ 4ohms gains were turned up all the way then backed off a hair. basically wide open

[AKHeathen]

have you tried messing with the gains and such? you may be picking up interference with a low signal from the loc(going by your gain settings) i usually need to disconnect the speaker/sub that the loc is tapping, or install a passive cross-over to keep it from having a feed-back loop with the speaker picking up sound from the sub and sending it back to be played.... those subs are somewhat prone to distortion when stressed, but i'm not sure that is the issue here

[SomeGuyInPDX]

I will disconnect the rear deck speaker that the LOC is connected to and see what happens.