I based my calcs on his dimensions being exterior resulting in 1.99 cubic feet. But I was rushing too so I may have been a bit off. If it's tuned to 26.5 hertz then the sub should not be bottoming out due playing frequencies lower than the tuned frequency.

I also question what crossover point the amp is set too (or if there is a "standard" subsonic filter setting)

 

I agree, it shouldn't be unless he's dropping absolute bottom/playing test tones.

The amp he has does not have a subsonic, which made me question whether his friend's does.

OP, time for more info if you want more helps. We've speculated as much as possible without more to go off of.

Big Mack

 

the port is not round.

i looked for the manual for my amp that we tested the sub with and i couldnt find if it had the subsonic filter or not its a cheap 2 channel 1000watt legacy predator amp. its powering my 2 kicker 12 inch L5s fine for over 2 years now.

i didnt play exact same music in my car, but i played a good hitting song, 1st at a normal volume and then at an obnoxious loud volume. the sub didnt bottom out once and was more or less just as lout as 1 of my kicker L5s.

the length of the port is actually 18" long. sry for the error guys i was tryin to remember the all the #s off the top of my head on the spot when joe told me about this thread lol

either 2day or sometime this weekend im going to hook up joes jl amp to 1 of my kicker L5s to c how it works

thanx a lot for all the help guys. any more info or anything info i missed?

 

Is there one port or two? Your other post indicated 2. This makes a big difference. I suggest measuring the port. Inside dimensions, including length, height, and width. Thickness won't really matter, so don't kill yourself to get that part.

No idea if it does or not without a model number. Surprisingly, some of the cheapest amps I've seen use boards from better quality units, therefore incorporating some of their features.

Get us the correct port info, with number, sizes, and all the good stuff. A model number for the other amp would help, too.

Big Mack

 

there are two ports, should be 5"wide x1" high x18"long. wen i made the ports i did compensate for the thickness of the mdf board. ill conform with joe on the dimensions since he has the box and sub

the amp i have is the Legacy Predator LA768

 

Now that I'm home from work I redid my calcs on the new info and came up with 26 hZ like you did Mack.

I'll rack my brain for answers but as of right now I am a bit stumped. Unless a slot port with only one inch of height is creating port noise? (although I've never heard port noise as "clacking"....only "whistling" or "farting")

 

i posted the amp im using now in my first post Mack.

 

I had the advantage of my computer at my disposal, mang.

I don't think it's port noise or it would be evident at almost any gain setting. I think it may just be the amp is being overdriven with a high level.

Right, that's how I knew it didn't have a subsonic filter . Your friend's Legacy doesn't, either, according to the manual. I'm still not clear how it's not making the noise in his car, but it is in yours. This leads me to think that it could very well be the amp, especially since those ports should be doing the 26.5 Hz that I said before.

What deck are you using? The sensitivity on the amp may not let you go much above 1/4 if it's got a strong preamp output voltage, which means it's not an amp problem at all - you may be overdriving it. This is not hard to do with a vented enclosure, even if it's tuned low (which yours is, in my opinion). It's also very dependent on the source material. If you're playing something that plays very, VERY low, you can still go below the tuning frequency and hear a bottom out. Even if you're playing something that plays a harmonic that is right above the tuning frequency, you have to keep in mind that it's still there, just quieted by the crossover. If you're playing it at 135dB and the crossover is 12dB, that's only going to put it at 123dB at the downpoint, which is definitely audible. In that case, I'd recommend a steeper crossover before the amp if the one in the amp isn't doing it.

Big Mack

 

im running a CarPC, probably going to pickup a 5.1 soundcard.

 

That could certainly overdrive the voltage, since a PC is designed to work with home speakers. I'd be very cautious with it, even with a soundcard. If you can measure the voltage on it, I'd bet it's pretty high and that means your gain should be down quite a bit. Overdriving a sub leads to a very short life, especially a vented one.

Big Mack

 

i regulated the voltage to not pass 12v.

 

Well, considering most decks only put out around 2-4V, that's about 3-6 times higher, so you're overdriving the bejeezus out of the amp if you're feeding it 12V. If you can drop that down to 3 or 4V, your amp and sub would probably be a lot happier, since I'm sure that 12V is way outside of the input range of your amp.

Big Mack

 

i have something where i can set what voltage to set it too, i think its either 6 or 8...gotta double check. but back on the main topic, you think my amp is going bad?

 

No, that's what I'm saying - you're overdriving it, which leads it to bottom out the sub. An amplifier does just that - amplifies the signal it receives. If you send it 12V of signal, it's going to try and amplify 12V of signal, much to the detriment of whatever gets in the way. You need to drop the voltage on the output and test again. I would recommend putting the gain as low as it will go, since 6V will still be driving the bejeezus out of the thing.

Big Mack

 

gotcha, will try that out Mack.