I have a MP3 and noticed that my 4 8s were actualy hitting the resanent frequency of the trunk, they were pointed backwards and I when the floor was in the resonance was around 80 HZ, with the floor out it dropped to about 65/70 hz. I had a few IASCA guys check it out and all were completly stumped. My only conclusion, 2 bulk packs of dynamat extream was actualy to much!
System resonance
- Thread starter 1sty
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PhyschoMP3
Member
what does that mean I dunno stereo talk
MP5s Make Ready
Member
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- 2002 Red Protege 5
I'm thinking it means that it's making a whole lot of unwanted rattling of the trunk.
MP5s Make Ready said:
Not at all. In fact their was no rattling, It wasn't any metal that was resonating it was the air in the trunk, creating a low almost constant tone. the subs in now way created the tone they just put the air into resonance. It was weird as hell.
I am curious...what kind of setup were you using with the 4- 8's? Were you using sealed or ported boxes. Also what were the woofers that you were using (brand and series). T
his is an extremely common problem with a block formation of sealed boxed that actually prohibits resonant bass from escaping the limited trunk space. In effect what happens is your subs produce the bass..which in turn moves air particles around aka resonant vibration. When you have too much resonant vibration in a small enclosed environment the vibrations dont have time to cool off or dwindle away before the bass hits again. In laymans terms your 4- 8's were setup in a way that wont let the bass(resonant vibration) escape from its environment quickly enough, and you had a buildup of resonance causing a constant muffled tone.
At least thats the case if you had your 8s set up in a block formation =-p. Give me more input and id love to help.
his is an extremely common problem with a block formation of sealed boxed that actually prohibits resonant bass from escaping the limited trunk space. In effect what happens is your subs produce the bass..which in turn moves air particles around aka resonant vibration. When you have too much resonant vibration in a small enclosed environment the vibrations dont have time to cool off or dwindle away before the bass hits again. In laymans terms your 4- 8's were setup in a way that wont let the bass(resonant vibration) escape from its environment quickly enough, and you had a buildup of resonance causing a constant muffled tone.
At least thats the case if you had your 8s set up in a block formation =-p. Give me more input and id love to help.
Cool input man.
To be detailed. I had 4 JL audio 8W3s dual 2 ohm subs wired for 4 ohm total load. They were being run off an Xtant X1001. The box was one large chamber. air space was .33 cubic ft per sub. They face directly backwards and the slanted back of the box was up agianst the back seats. I have a 2 " false floor it that it sat on. in the car the problem wasn't comletly noticable other than the fact that the subs seamed boomy. With the trunk open the resonance was clearly audable and once the box was removed from the car the low resonace was gone.
We tried moving the crossovers from anywhere between 50 and 150 hz with no luck. I also have an audiocontrol EQs that we tried to tune it out with but with no luck. I could understant the resonance if it was only with thte trunk closed but with it wide open it baffles me.
Whats a block formation?
To be detailed. I had 4 JL audio 8W3s dual 2 ohm subs wired for 4 ohm total load. They were being run off an Xtant X1001. The box was one large chamber. air space was .33 cubic ft per sub. They face directly backwards and the slanted back of the box was up agianst the back seats. I have a 2 " false floor it that it sat on. in the car the problem wasn't comletly noticable other than the fact that the subs seamed boomy. With the trunk open the resonance was clearly audable and once the box was removed from the car the low resonace was gone.
We tried moving the crossovers from anywhere between 50 and 150 hz with no luck. I also have an audiocontrol EQs that we tried to tune it out with but with no luck. I could understant the resonance if it was only with thte trunk closed but with it wide open it baffles me.
Whats a block formation?
To be detailed, I have a 200 amp alternator runniing 1/0 back to the battery, an Optima yellow top, then the 1/0 continues down the left side to a distrobution post, then 1/0 continues to 2 1 farad Monster cable capacitors. After the caps 1/0 goes directly to the X1001 amplifier which is less than 1 ft away from the caps. Signal wise the 3 RCAs, Stinger run in the middle of the right side of the car all the way back until they get to a audiocontrol EQS then the RCAs go to the X1001 and the X604. The box for the 8s was only 35" wide total but was perfectly sized internaly, .332 cubic ft per sub but it is one large open chamber instead of individual chambers for each sub.
interesting, i'll draw up a diagram of the wiring. I have actualy rewired the box from 1 to 4 ohms. Also I always test polarity of the subs and the impedance of a box before install. I havent swapped amps but if you remove the subs from the car or face them foward the problem goes away.
Ok with that said, there is minimal chance of it actually being the internal wiring of the subs/enclosure. Im going to ask just a few more questions.
Does the hum begin as soon as power is applied to the subs? If not how soon after power is applied?
Did this problem occur before the 2 shhets of dynomat extreme were added?
How close is the amp mounted to the voice coils when the enclosure is facing the erear? To the front?
The nature of the last question is to gauge wether your problem could possibly be caused through electromagnetic intetrference, while although is very rare....sounds like a possibility in this case. Especially with the minimal amount of room you are working with.
Does the hum begin as soon as power is applied to the subs? If not how soon after power is applied?
Did this problem occur before the 2 shhets of dynomat extreme were added?
How close is the amp mounted to the voice coils when the enclosure is facing the erear? To the front?
The nature of the last question is to gauge wether your problem could possibly be caused through electromagnetic intetrference, while although is very rare....sounds like a possibility in this case. Especially with the minimal amount of room you are working with.
The resonance occurs whent eh subs are turned up loud enough but its like the hit is gone and is somewhat replaced by the consistant tone.
I never had tried the system without the dynamat installed, and its 2 bulk packs of extreme not 2 sheets.
The amp is mounted under the left side of the box and the 4 channel under the right side. The box is in relativly the same position in relation to the amps rather it is facing forward or backwards.
I never had tried the system without the dynamat installed, and its 2 bulk packs of extreme not 2 sheets.
The amp is mounted under the left side of the box and the 4 channel under the right side. The box is in relativly the same position in relation to the amps rather it is facing forward or backwards.
That's not wiring, that's acoustics.
I know exactly what you're describing. I had a similar problem when I was younger. You go from a solid "thump thump" to a constant bass drone with more muddled thumps inside it. Imagine a lake. when you throw a rock into the middle of a calm lake, you can watch each ripple roll out. Try picking out one wave after a day of powerboating, jet skiing, and waves bouncing off the shore back out into the lake. It's just a rolling mass, impossible to distinguish. Your car cab is doing the same thing as the lake shore.
Do your seats fold down? if so, fold one down, the drone should disappear. If they dont, do a test with the trunk cracked. Permanent fix? Drop from 4 8's to 2 10's or a 12. Or just go for less damn power, you crazy guy!!!!!!
You're already creating four separate waves with the four speakers, plus the bouncing. Dynamat insulates both ways. Not only does it keep engine and road noise out, but keeps sound in, meaning even more of it bounces back.
Also, the more sound retained, the more the waves contact each other, creating harmonics for more and more base (root) frequencies. The more harmonics you create (musical notes), the more likely you are to hit a resonant frequency for some material in your car.
One reason why sub boxes are ported is to give the waves an "out" that could affect sound quality.
Seems like there's already some experts here (I aint one), so you're in good hands.
I know exactly what you're describing. I had a similar problem when I was younger. You go from a solid "thump thump" to a constant bass drone with more muddled thumps inside it. Imagine a lake. when you throw a rock into the middle of a calm lake, you can watch each ripple roll out. Try picking out one wave after a day of powerboating, jet skiing, and waves bouncing off the shore back out into the lake. It's just a rolling mass, impossible to distinguish. Your car cab is doing the same thing as the lake shore.
Do your seats fold down? if so, fold one down, the drone should disappear. If they dont, do a test with the trunk cracked. Permanent fix? Drop from 4 8's to 2 10's or a 12. Or just go for less damn power, you crazy guy!!!!!!
You're already creating four separate waves with the four speakers, plus the bouncing. Dynamat insulates both ways. Not only does it keep engine and road noise out, but keeps sound in, meaning even more of it bounces back.
Also, the more sound retained, the more the waves contact each other, creating harmonics for more and more base (root) frequencies. The more harmonics you create (musical notes), the more likely you are to hit a resonant frequency for some material in your car.
One reason why sub boxes are ported is to give the waves an "out" that could affect sound quality.
Seems like there's already some experts here (I aint one), so you're in good hands.
blynzoo said:
Hey sounds good to me, I appriciate anyones help. I have pretty much made up my mind to stop using the 8s since they are way over powered and run 3 eclipse aluminum 10s since they have always impressed me and the new JLs W6v2s are just to damned expesive. The 10's If I use them, I actualy have my 2 BA pro 12s back in right now, will be in a spare tire well box facing up which seemed to be OK when I originaly had the 8s like that. THen ofcoarse I am a little deranged so if I can fit them I will use 4 10" eclipse's.
Thanks Man
slowyellowp5
Member
Blynzoo: Part Time Electronics Master, Full Time Philosopher.
