LiCelsior

iTrader: (32)

im currently running this amp right now, a PIONEER GMD-8400M (http://www.sonicelectronix.com/item_...GM-D8400M.html) bought this a year ago.

and i just recently purchased this sub, Phoenix Gold RSDC124 (http://www.amazon.com/Phoenix-RSDC12.../ref=de_a_smtd)
here is some more detailed specs on the sub, ftp://public_user:password@www.rodin...r%20manual.pdf

i just had a box made to the SQ spec of 2.5 cu ft but now im getting a knocking sound which i found out was the sub bottoming out. also have the sub wired up in parallel. does this mean that the amp is overpowering the current sub?

thanks in advance, Joe

sam430

iTrader: (10)

No way the amp is overpowering this sub... it's 600wrms rated power (ppl are saying higher than that). Something else is going on here. Drop it in a friends car to eliminate the amp as being the problem. If not the amp, get amazon to get you a replacement.

LiCelsior

iTrader: (32)

i did drop it into another friends car and it didnt bottom out.

mkorsu

Joe. Since you said the box is "SQ spec" @ 2.5 cubic feet, I'm assuming it is a sealed enclosure?

mkorsu

Joe. If you could also post up the following specs on the driver. (My computer at work does not have adobe so I cant view pdf's)

Fs
VAS (in either cubic feet or liters)
QTS

Thanks

sam430

iTrader: (10)

26.4
58.7
0.491

LiCelsior

iTrader: (32)

oh no its not a sealed inclosure Mark, its actually ported...maybe thats the reason?

and the VAS that sam posted is in liters, thanks Sam.

mkorsu

Whats the port size? Diameter and length?

The QTS is on the higher side for a ported enclosure but should still be perfectly fine.

When you said you tested it in someone else's box, what design was that box? Sealed or Ported?

LiCelsior

iTrader: (32)

no no i meant when i tested the sub with the box in my friends car using his amp, it didnt bottom out. but when i put it back on my car it began to bottom out again. ill have my friend chime in with the dimensions.

mkorsu

That pretty much rules out the sub and the enclosure. Sounds like the amp is the culprit. Begin by adjusting the gain and see if that helps. Also make sure the crossover (filter) is set to Low Pass.

Let me know what happens when you try those.

Li Ls4

iTrader: (12)

the box is 20.5x18x14 with two 5x1x11 size ports, i used 3-5 port size charts/calculators to get figure out the correct port lengths for 2 ports and we hooked the sub in the enclosure up to my amp and it worked fine

Li Ls4

iTrader: (12)

i also played around with the gain and such, the gain was only at 1/3 and with the volume normal, not loud at all it would start bottoming out, and if u turn it up the gain couldnt b any higher than 1/4

Big Mack

iTrader: (1)

Did you play the exact same material in your friend's car? Did your friend's amp have a subsonic filter? It sounds (no pun intended) like you are playing the sub below the box's tuning frequency, which will cause it to unload and bottom out. If your amp has no subsonic filter and you are playing it too low, the amp is not defective - it is not designed to do what you need it to do. More info is really needed here before we make the assessment that the amp is bad.

Big Mack

mkorsu

If I'm reading your response correctly..... 5" diameter circle port @ 1" thickness and 11" in length. Your box is tuned to roughly 55 Hertz. You may want to retune the enclosure to a lower frequency.

Mack, do you agree with my calcs on the Fb? I did them quick on a break at work.

Big Mack

iTrader: (1)

According to my numbers, an 11" long port with a 5" diameter in a 2.5 cu ft box is 38 Hz.

I don't think it's a round port, though, and he said there are 2. If they are slot ports, since he gave 3 dimensions, it's tuned to about 26.5 Hz, which should be pretty decent.

I'm still curious as to whether or not there is a subsonic filter in the friend's amp, since his doesn't have one.

Big Mack