RPM's dropping when the bass hits..

[kdc_619 10+ year member]

I'm not sure if this is the right section so I apologize..

I have a 240 amp mechman alternator and a kinetic 1800 battery as well as the big 3 upgrade. I'm running 2 FI Alphas on a Rockford Fosgate 1200 and 4 door speakers on a Rockford Fosgate 250. At idle the rpms drop (roughly 300 rpms give or take) when the bass hits at high volume. I'm not really sure what's causing this as I tried to take the necessary sets to prevent this with the HO alt and battery ect..

And here I was thinking I had enough juice to add a second RF 1200 so each sub has its own amp.

Any ideas as to what's causing this voltage/rpm drop?

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[wew lad 5,000+ posts]

takes power to make power my man, completely normal due to the draw on the alternator at full output.

raising the idle rpm helps, but honestly the main thing that helped me was adding a bank of caps (and 2nd alt) for smoothing out the current draw. not sure if its the best solution but it is an effective means to stop it

check the voltage at the alternator/battery and then the amp terminals to see if theres a difference and drop in your wiring. i doubt it, but if you have drop let me know

 

[Hertz Mafia]

Rev alt to 2k rpm to get full power. With all my alts I can drop 1000rpm when the bass hits

 

[kdc_619 10+ year member]

I have a follow up question if you don't mind.

I happen to have a spare Kinetic HU 1200 BLU. If I had that added to the system would that help at all? Also, I was talking with my installer (I've never done a multiple battery set up and quite frankly I don't feel like dying today haha) he said I'd need a battery isolater/relay to add the second battery..but from what I've been reading a isolater isn't needed unless you're using your system with the car off?

Ultimately I wanted to add a 2nd RF 1200 but the rpm'so dropping has me wondering if the 2 battery and HO alt. can handle three amps

 

[audiobaun 5,000+ posts]

You should check your grounds and placement for starters..I would think you should have plenty of battery bank and alt power to generate enough for the demand you currently have,and possibly a second amplifier.But most alts/HO alts need to be around 1500-2k rpm to generate decent voltage,and you loose at full tilt.Your going to drop regardless.If at 2k rms and less..usually you can get by with two good agm batteries 140 amp stock alt and big 3 being done in 0 ga with 0 ga supply.Any more and look into more supply for the demand generally.Check your belt as well make sure its tight and not slipping also.

 

[audiobaun 5,000+ posts]

I have a follow up question if you don't mind. I happen to have a spare Kinetic HU 1200 BLU. If I had that added to the system would that help at all? Also, I was talking with my installer (I've never done a multiple battery set up and quite frankly I don't feel like dying today haha) he said I'd need a battery isolater/relay to add the second battery..but from what I've been reading a isolater isn't needed unless you're using your system with the car off?

Ultimately I wanted to add a 2nd RF 1200 but the rpm'so dropping has me wondering if the 2 battery and HO alt. can handle three amps

You can run multiple batteries(up to 6) generally without any issues.A second battery will help. I havent ran an Isolator since early 90s. Id run one on a boat though.In my sig below.. I was running 2-(2500 rms amps on subs and 1-(100x4) and one 200x2 without any real issues with 3 batteries(all same agm batteries) and would drop at a low of 13.2v on a low note and at idle around 14.6v reved up to 13-1500 rpm on the low notes as stated 13.2 on some Decaf tunes

 

[kdc_619 10+ year member]

So would you wire the two batteries in parallel to each other?

 

[audiobaun 5,000+ posts]

So would you wire the two batteries in parallel to each other?

under hood battery+ with an ANL fuse(250-300) to rear battery + to a Fuse block for power to amp/amps ..One run 0ga..Then ground /- to rear 0ga(like frame or drill hole and add a ground point to frame /rear axle location for solid ground point to another Solid Ground block (multi solid block from batt in rear..what I always use/do in most cases

 

[LosIsATool 5,000+ posts]

Turn the gain down and if any boost is on turn it off.

Also triple check all grounds.

 

[kdc_619 10+ year member]

I just spoke with the guy who insstalled my system and he seems dead set on this diode isolator.

https://www.sonicelectronix.com/item_61067_Stinger-S2402.html

Seems like I'm SOL on this one.

 

[adulbrich 5,000+ posts]

I just spoke with the guy who insstalled my system and he seems dead set on this diode isolator.
https://www.sonicelectronix.com/item_61067_Stinger-S2402.html

Seems like I'm SOL on this one.

No, that's a waste of money. Just wire your batteries in parallel with a fuse.

As everyone else has said, it's normal to drop RPM's when your alternator is loaded down.