amp cutting out

[tyrefryer]

i have tried doing a search on this but none of the solutions seem to suit for my case.

The problem is the amp will run for about 5 seconds then when a bass note comes it cuts off and then comes on after a few soconds..i have tried a number of solutions:
1. checked earth - i thort this was the problem cos the protection light from one of the amps i tried kept coming on, i put the earth cable everywhere but i think its ok.
2. changed amps - i tried a tiny 200W amp and it made the sub make a clicking sound but the amp didnt turn off just no music, i tried putting a small sub with this amp and it went fine. the other amp i tried was a 4channel 800W which was working previously but would cut out a fair bit when the amp got hot i think. amp connected now is a Alpine MRV F340 which has only like 300W rms i think. this one makes sound until i turn the gain up any lil bit then it stops. the sound it makes is very very quiet. and the Sub is a dual voice coil sony explode which is 400W rms 1400 peak.

iv connected the sub in parallel and series with the coils...same problem, the alpine amp was already hoooked up to a 400W rms 1200peak SVC sub b4 and it was fine.

At the moment i have the coils in series and they are rated at 4ohms per coil and i have bridged 2 channels on the amp. when i pulled the sub out it was wired with
amp +ve --> coil 1 +ve
coil 1 +ve --> coil 2 +ve
coil 1 -ve --> coil 2 -ve
coil 2 -ve --> amp -ve
i dont understand how that works tho

I got 8 guage wire and i know its not the headunit cos i hooked up a smaller amp and sub and it went fine.

IS this a problem of the amp not having enuf power for the sub. i dont see why it runs the other single coil sub which is equal almost.

Also i dont think its the sub thats faulty cos it was working b4 most of the time and the amp doesnt light up red at all with the sub off only when i connect the sub and turn the gain up anything over 1/10th maybe. and only when its on full or LP filter mode cos thats when a bas note kills it even tho i cant hear much b4 bass comes.

sorry for the length, its kinda late and iv tried putting as much info as i can, i dont know whats wrong.

[.]

My advice to you will be that your amps are not two ohm stable which is how the coil is wired up. You will need to change the coils so that they are wired in series and not parallel.

Try putting the + from one amp to + on one coil and the negative from the amp to the - of coil 2. Then run a short piece of speaker wire between the - of coil 1 and the + of coil 2. Unfortunatly this means the amp won't put much power into the subwoofer but it may be your only option short of either (a) getting a bigger amp to run the sub only that is 2ohm stable or (b) getting a second sub exactly the same as the one you have now but then both subs would be heavily underpowered.

[.]

oh wait..I just read you already tried putting the coils in series and no luck eh? Well, I'm wondering if you speaker cables are heavily pinched somewhere and are shorting against each other. This will cause an amp to go into protect mode.

[buddaboy1990]

hmmm..... it sounds like the auto cut off is playin up. With 1 of my old amps it had an auto cut off that if the amp peaks it cuts off so it doesnt fry the amp and that did the same thing u r describing. It turned out 2 b a dry link inside the amp. U probly havent but hav u taken the case off the amp and looked at the circut board 4 any dry links.


PS if u take the case off remember 2 disconnect the power or u will get a shock

[.]

bear in mind bb1990 that he has tried two amps....both having similar results.

[tyrefryer]

i might try using some speaker wire straight from amp to sub then as its hard to check the wire at the point that it goes thru the box...the more things i can eliminate the closer i will get to fixing this problem.

"." do you think my amp should run the sub if it seeing 8ohms, i realise that would be low power but surely that shouldnt cause it to keep turning off

i was using u DMM to measure certain point and the negative on the amp measures from zero and the voltage climbs slowly to 0.25v then the amp cuts out and voltage goes to zero. (i think it was the voltage i checked as i did a current reading and it did the same thing, increased slowly then amp dies.

[.]

yes, your amp will run it at 8ohms...just not much output as you are already aware. There is no point checking the output of the amp...we already know what that is....nadda.


Check continuity on your current speaker wires also with it set to continuity put on terminal on a speaker wire and then another on your ground wire...if it beeps on either ground wire....your introuble and need to replace the speakerwires and find where it's being pinched to earth and make sure it doesn't happen again.

[tyrefryer]

"." you are a legend, it was very hard to work out where the problem was exactly but yes the speaker wires were shorting at the connection terminal on my sub box which is at the back so i didnt think of checking it b4.

How to you give rep points cos that deserves them.

2 other questions.
1. my old amp fried itself from me mucking around so much so the one i got on now is less powerful so iv had to do a parralel connection. it says in the manual it can run 2ohm off one channel but only 4ohms if bridged.
I have it running 2ohms bridged at the moment but if i really crank it it stops for a second then goes again.
Can i run one coil off one bridge and the other coil off the other 2 channels bridged (4 channel amp). i read it can be done but u have to keep the gains exactly equal and all that.

2. My sub box fits in my boot nicely at the moment but as a result its proberly oversized. i opened a sub box yday and it had the pillow filling wool in the box, what was the pupose of that, can that be a way to lower the box volume? or is there any other way to reduce the area. only way i can think of is putting a piece of mdf inside the box to trap a smaller volume around the sub.

But thanks heaps for helping me solve the major problem i been having, at least now i can hear my bass!

[garfa]

possibly think about Speakon connector as this will negate all problems of a terminal plate and is the best connector i have used in a long time.

[.]

Answers...
1, Your amp is cutting out due to "Clipping" otherwise known as disortion. It's cutting out to save itself and your speaker. Yes, you can bridge two channels for coil and the other two for the other coil...and yes, your gains have to be exact...but there is one more catch...the signal to both amps need to be EXACTLY the same. you need a bunch of rca splitters and joiners. First you must join your left and right signal into one single rca plug....then split it out of that into four.

2, "pillow filling" also known as Dacron is their to actually INCREASE the size of the box by turning the enclosure into a "Infinite Baffle" the woofer then requires more power then normal but you get the effects of using a bigger enclosure. Your best bet here is to rebuild the box. You could MDF in it to "shrink" the enclosure down but reality is...just rebuild the box.....or, you could add a vent to the box if it really is oversized but then you would have to calculate how big of a vent and if you can get it in there.

Speakon connectors are good if you are in the habit of removing the enclosure from the car or if you want to be able to move it and you are running high power. Voltage drop across this quick disconnect is virtually nil.