[Never_Enough]

Is it ok to put 400 RMS to a sub rated for 250 RMS?

[david in germany]

A 100w sub can handle a 1000w amp if tuned properly and not driven to hard. Also take into consideration, not every 400w amps will produce 400w cleanly. Depending on the amp, it could be rated at 400w and only produce 100w.
What amp and what sub are you planning on running?

[Never_Enough]

Originally Posted by david in germany

A 100w sub can handle a 1000w amp if tuned properly and not driven to hard. Also take into consideration, not every 400w amps will produce 400w cleanly. Depending on the amp, it could be rated at 400w and only produce 100w.
What amp and what sub are you planning on running?

Arc Audio XDi-805 amp & Rockford Fosgate R2D4-10 sub.

[kaigoss69]

Originally Posted by BoostedRide

Arc Audio XDi-805 amp & Rockford Fosgate R2D4-10 sub.

You can definitely smoke the voice coil or cause mechanical damage through over-excursion. If you have a trained ear, you can probably hear when the sub starts getting stressed, otherwise I would recommend using the JL Audio gain setting method.

[sparkymarky]

Originally Posted by kaigoss69

You can definitely smoke the voice coil or cause mechanical damage through over-excursion. If you have a trained ear, you can probably hear when the sub starts getting stressed, otherwise I would recommend using the JL Audio gain setting method.

Exactly, use the jl audio gain setting method with a multi meter and you can then use the amps Gain dial knob as a power limiter - i.e decide what max power you want to send to the sub (so 250rmw or a little more, say 300wrms), use the formula to work out what voltage that will be on your multi meter and turn the amps gain knob until that voltage is read. This way you will never send the sub power over and above that which you have decided is the max you want it to receive.

Dont forget to crossover correctly too, low pass and if possible high pass/subsonic filter, (effectively band passing), so not to damage sub by trying to mak eit reproduce frequencies it cannot handle.

[kaigoss69]

Originally Posted by sparkymarky

This way you will never send the sub power over and above that which you have decided is the max you want it to receive.

Right, but only if the input signal is no stronger than it was during the gain setting procedure. The input signal strength changes with different input devices, recording volumes of the source materials, bass boost, and of course the volume setting of the HU itself.

To be on the safe side, I would:

1. Find out which input device (CD or AUX) produces the most volume and use that device during gain setting

2. Have the HU volume at max undistorted output. This seems pretty difficult but it isn't. In L7 head units, the max undistorted volume is about 50 clicks of the volume knob (turn knob all the way to the right (when no music is playing) to the 55 click max (turn knob a few times to be sure you have reached max) and then back off 5 clicks to 50. In Hifi or base, I think the max undistorted volume is lower, but I don't know exactly how much. To be safe, I think you could use 35 clicks.

3. Set the bass boost and EQ for bass at the zero positions, and the aux volume wherever you like, and never change any of those settings!!!

The JL audio method asks you to use 0 db test tones and in combination with the above, this ensures that during normal listening you will never exceed the input signal strength/voltage that was used for gain setting.

[Rialas]

I can't use the gain limiter in my case?

I'm trying to understand how to set these levels also.

As above, I believe you have to set the input sensitivity depending on the maximum output you're going to push to the woofer amp.

I bought the jl audio remote volume control which by-passes the output volume on the amp. So the only option for preventing damage to the woofers for me is from the input trim.

Quote from their website.

"When the RBC-1 is connected to the above amplifiers, the on-board "Boost" control of the amplifier is defeated and the RBC-1 becomes the active controller.
The RBC-1 kit includes the rotary control with a black ABS knob, mounting hardware and one 18 ft. (5.5 m) cable.
A satin-finish aluminum knob can be purchased separately."

[Rialas]

As I have the optional remote, this how I'm going to have to do it.

Turn my optional sub remote to full.
Turn the woofer output on the headunit to full.
Turn the headunit volume to LOUD.

Slowly turn up the trim on the sub amp to balance between subs and doors before distortion.

The Greek way lol. What's a voltmeter?

[david in germany]

If you are worried about it, wire the sub in a series and give the amp an 8 ohm load. I would estimate that amp will do about 180w at 8 ohm.

[taibanl]

Strictly speaking, no. Your 250 W rated to sub cannot handle 400 W RMS. However, just because your amp is rated for that doesn't mean that is what you are pushing.

You would have to be pushing a 0dB signal at the amps rated power to see 400 W at the sub.

You can limit the gains or limit the music you play and you'll likely be fine.

[Never_Enough]

Thanks for all the replies.

[bmw325i]

Imo if you blow it then its time for an upgrade. At least that's how my first few subs worked out .