not a huge car audio enthusiast but trying to get amped

[twich12 10+ year member]

pun intended... hope you don't mind my lameness..... so down to business!

i got 2 infinity 300w reference series subs (12" but i am still calling them subs) 300w rms and i believe they are 4 ohm speakers, tough to find info on them because they are a bit old and cheap, but i also received a jbl bp300.1 amp which definitely isnt running them even close to 300w! wondering what amp would be recommended for pushing these subs? i dont want an amp that will push each one to 300w but something that well get to about 250w each and i dont want to spend boat loads on it because like i said, im not a huge car audio enthusiast....

other circumstances to consider- pretty sure the amp is overheating because after i use it for about 20 minutes cranked up it shuts off (this is part of the reason i want a new amp that is actively cooled, im willing to MOD the amp and incorporate a fan since i have some soldering and pcb rework experience) oh and i may be coming across a pair of 15 inch speakers, i believe they are also 300w a piece 4 ohm.... should i junk the 12" ones build a new box and use the 15"? (my dad is big into audio and will be switching out his 15" "subs" for real 18" subs for his bands bass guitar)

PS im new and kind of excited about getting into car audio! seems like a logical extension of my love of computers, music, and cars

Click to read more...

 

[whitedragon551 5,000+ posts]

That amp does plenty of power. I have money on your tuning. Tune it properly with a DMM. Make sure the ground and power wire are the same size, bass boost off at the headunit and off at the amp.

You can also use a DMM to tell us what coils the subs have. Do they have one set or two sets of terminals? What do they read on the DMM? That will tell us what you can wire them to for the amp and will tell us what you need to set the gain to on the amp as well.

 

[twich12 10+ year member]

well i assume by DMM your talking about a multimeter? just making sure... i used a cheap-o kit from walmart for the install, i believe the power and ground are both 16 gauge (will double check) they are definitely the same size, just not sure of the size! and i have to go to mass but i will be back on here in about 2-2.5 hours with some DMM numbers, how would i go about tuning it properly with a DMM? each sub has 1 set of terminals on the box, not sure if its any different on the sub itself (came already put together). and are you saying you think the tuning is the reason the amp shuts off after a little? that would be nice that way i dont have to buy a new one... i kind of want new speakers though, i can hear the rather poor sound quality of these, especially after leaving my dads house

deck- pioneer deh-p6000ub

amp- jbl bp300.1

subs- 2x 300w rms infinity reference series

edit: where would you recommend placing the amp? its sitting in my trunk right now tucked up against my back seat (since thats as long as the walmart kit would allow for) and how do you keep the subs from sliding around? i mean its not like they are going from side to side but every month or 2 i have to open the trunk and reposition them... oh and i have an 02 grand prix se

 

[whitedragon551 5,000+ posts]

16 gauge for power and ground no wonder your amp gets hot. You should use atleast 4 gauge and nothing less. Upgrade the power and ground to 4 gauge and in the mean time get me DMM readings on the coils on the subs and I can tell you what to tune your amp to.

 

[hispls 5,000+ posts]

Indeed #16 for power and ground to an amp is pretty dangerous and not helping anything. IMO for a 300W amp #8 wire works, but you can get a #4 wiring kit for pretty short money and always yank it out and use it in your next car. You will want a SOLID ground as close to the amp as possible. Must be in some solid metal and make sure you sand down the paint and have nice shiny metal where it connects to the chasis of the car.

A lot of people just get some cheap L brackets to secure box to the floor of a trunk. I wouldn't reccomend guitar cab speakers for a car unless you really know what you're doing and really know the products you're dealing with. PA speakers are designed with completely different performance goals and are normally impractical for car use. All other things equal going from 12's to 15's would only be a 1db gain, so noticable, but not incredible and to do 15's correctly you need to give up a lot of real estate in the trunk.

You can mount the amp anywhere that's secure, but you'll want some air flow around it. Really there's very few amps these days that use fans and I can't think of more than 3 or 4 amps period that are under 1000W that use fan cooling, considering the efficiency of a car amp (poor) versus the efficiency of any practical sized fan (also pretty poor) your cooling would be minimal IMO. Best to just make sure you don't crowd the amp or say leave a duffle bag on top of it.

Pics of the setup and DMM results will help.

 

[twich12 10+ year member]

quick question, whatr do you want me to measure with my dmm? impedance? operating voltage?

 

[05fronty 5,000+ posts]

read the ohm of those subs. are they the dual voice coil one's?

 

[twich12 10+ year member]

it measures 3.8-3.9 and its 6 gauge not 16 (sorry about that)

edit:also i opened the amp because i thought i heard something moving around and it looks like 2 of the mosfets are not cooled (what was moving was just a little rubber foot that rests between the sheet metal and a couple big caps)

 

[hispls 5,000+ posts]

Do you have two subs? Are they run parallel? That amp is supposed to do max power at 2 ohm.

A lot of amps don't have fins on the FETs, generally speaking if one needed to be heat sinked and wasn't it would smoke pretty fast so I suspect whatever you see in your amp is what is intended.

Pics of said subs/box/amp where they sit in your install.

 

[twich12 10+ year member]

i have 1 amp and 2 subs, pictures will be provided very shortly and i will take a close up of them input/outputs.... i am willing to get a new amp if need be because this one is starting to annoy me and i got it for free

edit: album with some pictures in it... they are hi res so 56k warning http://s776.photobucket.com/albums/yy48/twich12/subs/

 

[hispls 5,000+ posts]

First of all, you lose a lot of output from a trunk. Next that amp being mounted there will block the sound waves trying to travel through to the front, I'd try to move that. Also you may want to play with different locations or aiming of the boxes. Pull the boxes all the way to the rear of the trunk (like a few inches from the back wall) and turn them facing back, get the amp out of the way and I'm sure you'll notice an improvement in output. Each box to a side of the trunk with subs firing towards the sides may do well too and may be a more acceptable layout.

From there you need to decide if that sort of layout is acceptable. For most people 1 or 2 12's and 300W is adequate. You can probably get a 600W amp for

 

[twich12 10+ year member]

well my main problem is that the amp shuts off after i crank it up really loud for about 20 minutes (it didnt do it during the winter so im guessing its overheating, probably doesnt help that its pretty old, the whole setup is atleast 8 years old)

 

[hispls 5,000+ posts]

My theory on that is if you are over-driving the amp to get to a particular level of output basically you need more output. Your solutions are either get the output you like while keep your amp within its limitations or get a bigger amp that will give you what you need without pushing it beyond its limits.

Could be you got the CA bug and will never be happy and always need to upgrade or try new things, in which case, time to get a second job LOL.

 

[Bumpin' Goalie 10+ year member]

well my main problem is that the amp shuts off after i crank it up really loud for about 20 minutes (it didnt do it during the winter so im guessing its overheating, probably doesnt help that its pretty old, the whole setup is atleast 8 years old)

Even older amps shouldn't go into thermal protect mode (overheating) without a fixable cause. I would do a quick google search on how to set gains with a DMM, and reduce all "bass boosts". Also, double check your ground. Make sure it's attached to bare, sanded metal at the very least. And a part of the chassis that is readily connected to the rest of the vehicle's chassis. Poor grounds seem to be common.

Best of luck,

B'G.

 

---------- Post added at 08:59 AM ---------- Previous post was at 08:59 AM ----------

 

My theory on that is if you are over-driving the amp to get to a particular level of output basically you need more output. Your solutions are either get the output you like while keep your amp within its limitations or get a bigger amp that will give you what you need without pushing it beyond its limits.
Could be you got the CA bug and will never be happy and always need to upgrade or try new things, in which case, time to get a second job LOL.

This hold so much truth...I don't even listen anymore, I just analyze...

 

[Bumpin' Goalie 10+ year member]

Also, if you are seeking more output/ a different type of sound, the enclosure will be a crucial variable.

What are your enclosures now? (Cubic feet? ported/sealed? if ported; tuned to?)