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amp/subs problem...

Old 08-07-2002, 08:11 PM
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nando11211
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Hello...

I have an MTX Thunder 152 sub hooked up to two Kenwood Tornado KFC-2505 subs in a sealed box, which is a little bigger than specs.

Problems:
1.) The amp runs very hot. I have it hooked up by parallel.
2.) The subs seem to distort, almost sounds like its farting, and I'm not even playing it that loud. Its like they sound like they are going to blow, and they vibrate a lot.

I also have a Pioneer P4000 deck and Infiniti speakers for the front. I have one Kenwood amp going to the inside speakers. The MTX goes to the subs. I want everything to be even, I don't want the inside to overpower the subs and vice versa. Another problem that I have is that the controls on the deck affect both the subs and the inside speakers, so if I don't want bass inside, I turn the low level down and it also turns the subs bass level down.

SPECS:
Thunder 152 Amplifier

--------------------------------------------------------------------------------
RMS Power measured at 12.5 Volts DC:
37.5 Watts x 2 into a 4 Ohm load with less than 0.05% Thd+N
75 Watts x 2 into a 2 Ohm load with less than 0.1% Thd+N
150 Watts bridged into a 4 Ohm load with less than 0.1% Thd+N

Dynamic Power (IHF-202 Standard) measured at 14.4 Volts DC
90 Watts x 2 into a 4 Ohm load
165 Watts x 2 into a 2 Ohm load
325 Watts bridged into a 4 Ohm load

Signal to Noise Ratio:
110dB A-Weighted

Damping Factor:
>200

Frequency Response:
20Hz-20kHz ± 0.25dB

Maximum Input:
8Vrms

Thunder EQ:
Variable Bass Boost (0-18dB) centered at 40Hz

Crossover:
Variable 40Hz to 200Hz, 12dB/octave high pass,
24dB/octave low pass with mono output

Dimensions:
8” x 9” x 2” (20.3cm x 22.8cm x 5cm)
9-1/4” x 9” x 2” (23.5cm x 22.8cm x 5 cm) Including IsoFeet™

SUBS:
Subwoofer Specifications

Size: 10 inch
Rec. Sealed Box Dims: 1.00 cu.ft.
Rec. Ported Box Dims: 1.10 cu.ft.
Free Air Usage: not recommended
Sensitivity: 91 dB
Frequency Response: 28-800 Hz
Recommended RMS Power: 150W
Peak Power Handling: 500W
Impedance: 4 ohms



I currently have this setup on my deck:
Low: -6
Mid: -4
High: +5
Loud: Mid

What should I do to fix these problems? Please help. Thanks.
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Old 08-07-2002, 08:35 PM
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Ok well first of all, i think u mentioned it wrong in the beginning. It's a MTX Thunder 152 AMP, not sub correct? Well it should be.

To answer the first problem: "1.) The amp runs very hot. I have it hooked up by parallel. " Don't worry about it. Amps will get hot to extremely hot. It's because you're drawing a lot of wattage from it and to put it in terms that's easier to understand. Does your tv get hot when left on? Just look at it like that. Like most amps, your amp has a "automatic" shut off when it reaches a specific core temp. When that does happen, it doesn't necessary mean that it blew, it just needs time to cool down. And with that in mind, it means that u need more flow of air to cool it down so u have to relocate it.

To answer the second problem: "2.) The subs seem to distort, almost sounds like its farting, and I'm not even playing it that loud. Its like they sound like they are going to blow, and they vibrate a lot. " From what the specs show, your subs should handle what your amp pushes. I mean your subs at RMS is 150W at 4 ohms. So when you bridge them u're running it at 2 ohms. From what your amp specs reads it says 75W x2 at the 2 ohms load. So from that I would have to say that your amp is too weak to power the subs but it doesn't mean anything. In other words i'm trying to say that you're running everything in "Safe mode".

You say that your subs are making a farting noise. I'd have to suspect it being blown. Even tho everything's safe, there could've been a tear or something in the sub. I would also have to look into the enclosure. Someone recently posted that they've been hearing a farting noise lately and concluded that it was the enclosure.

About the bass being affected when changing the HU outputs. It's gonna happen. Because you hooked ur amp to the HU, it's like everythings running in parelle. One thing get affected, everything gets affected. Having a HU that has sub outputs will change that. Even having a EQ for the inside spkrs can change it.

Well i'm getting tired. Someone please write!
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Old 08-07-2002, 08:35 PM
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if the subs are SVC, one voice coil, you are giving the amp too big of a load. thats why is it getting hot.

you really need a bigger amp, or just run 1 sub right now and bridge the amp. this is if the sub is indeed SVC.

and the subs really has to be in the right box, or they will sound like crap. MAYBE this is the reason to why they are sounding so bad. how much bigger than specs are you talking about?
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Old 08-07-2002, 09:34 PM
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Well if you got a Honda Civic (97 or around there) 4 door, imagine half of the trunk being taken away because of the box, that's how big it is. I'll measure it tomorrow (can't go outside cause its pouring) then I'll post it here. The thing about the enclosure is that its like two boxes in one, there is plywood seperating one speaker from the other, and I know most boxes is just one panel.

Like from inside I can't hear that farting noise, barely sometimes. But when I open my truck and have the subs in front of me I hear it. Its like they are going to pop out of the enclosure.

??????????????

Please help, but thanks for the help so far.
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Old 08-07-2002, 10:16 PM
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thats normal. same thing happened with my JL w3s. they sound fine with the trunk closed, but when the trunk lid was open, they sound crappy.

i THINK this is due to the enclosure that the trunk creates. bass from a sub is moving air, when the air is contained inside a cabin, i guess it sounds good. when it is exposed to infinite space, like when the trunk is open, all the air is escaping. am i making sense.

and having that divider is normal, and actually better than 2 woofers sharing the same space.
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Old 08-08-2002, 02:56 AM
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igo4bmx
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Originally posted by WiLL

and having that divider is normal, and actually better than 2 woofers sharing the same space.
why would sharing air space be reccomended? IMO having two subs share air space is bad, because they don't both exactly play at the same time. there is some millisecond differences, having them play in the same chamber would create a turbulance, when one woofer which plays first it canproduce enough pressure inside the box to disturb the other one from play properly
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Old 08-08-2002, 03:54 AM
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box measurements:

32" wide
12" high
16" deep


I never realized that all this was normal, I'm kinda new to all this and hooked it all up myself, which is why I'm kinda paranoid as to what if something is wrong.

But now that you see my system hookup, where should I upgrade or improve, I remember someone saying that I should get a bigger amp to push my subs.
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Old 08-08-2002, 05:33 AM
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if its 'farting' an easy way to see if your enclosures are air tight is to push the sub in.. literally. carefully push it in and see how it bounces back. if it bounches back quickly, your enclosure is not air tight, if it bounches back slowly (like 1-2 seconds) your enclosure is air tight. now the only other options would be that your box is too small... and the air is hitting the back OR your subs are blown/defective/something wrong

if there is a leak, your sub will be throwing too far hence, farting, blowing, or sounding like crap. cuz the outside air is equalizing the inside air when it hits

I'm not sure about this but i noticed amps never post bridged on a 2 ohm load. are you on a 2 ohm load bridged? cuz that could be out of spec of the amp
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Old 08-08-2002, 07:09 AM
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Originally posted by igo4bmx


why would sharing air space be reccomended? IMO having two subs share air space is bad, because they don't both exactly play at the same time. there is some millisecond differences, having them play in the same chamber would create a turbulance, when one woofer which plays first it canproduce enough pressure inside the box to disturb the other one from play properly
read my post over.:p


nando11211: with those specs, and assuming its .75" wood, you have about 1.4-1.5cu ft of space for each. so the box is IMO just too big.

and im the one who said your amp is too small.:D
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Old 08-08-2002, 11:43 AM
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Originally posted by derf
I'm not sure about this but i noticed amps never post bridged on a 2 ohm load. are you on a 2 ohm load bridged? cuz that could be out of spec of the amp

Yep there are quite a few of amp that run at 2 ohm load bridged. Why did you think that was odd? anywhos...that's not the point. There's not a whole lot you can do nando11211. Actually where did you buy your enclosure? If you made it yourself then maybe there's the prob. But i'm sure you didn't. Just take the subs out and examine them. Test them without the enclosure and see if the noise still persist.
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