understanding subwoofers and their amps

**Song0330** · 04-14-2005, 05:11 AM

Alright, can't find too much info about dual-subwoofer setups and installation. Crutchfield has some info, but not everything I wanted to know.

Here's the deal: Let's say I have a mono class d amp putting out 500 watts rms @ 4 ohms. Now, pretend I have 2x 400 watt rns subwoofers. Will the amp supply 500 watts rms to each sub, or will it only supply 250 watts rms to each sub?

Also, are subwoofers also susceptible to being underpowered (clipping?) and overpowered as regular speakers are? Depending on my subwoofers, I may get an amp that is between 150 watts under to 150 watts over, and I want to make sure they don't break.

**sdashiki** · 04-14-2005, 12:21 PM

if the subs are 8ohm and not 4ohm they will I believe see 500watts each.

At 4ohms bridged subs would only be a 2ohm load, unstable on your amp.

400 RMS is kinda high unless you spent $$$ on them but anyway... with a mono amp you get what it says 500watts. now im not 100% sure but bridging the 2 speakers by taking the +/- from one sub and just putting another wire from it to the next subs +/- you will halve the ohm load but keep the wattage load.

I think. I mean i run 100watts into 2 75-125watt RMS subs bridged and they still pound so its not running at 50w or they wouldnt even make a sound.

**sdashiki** · 04-14-2005, 12:23 PM

And of course, YES they are susceptible to under/over powering.

UNDER, they wont make any noise pretty much.

OVER you cant truly hear with the human ear to well, but a GOOD ear can hear clipping. Set the gain on your amp accordingly, or get an oscilloscope to see the waveform clip and adjust that way.

MAKE SURE you know the OHMs of your subs and the TRUE RMS of them, not the MAX but the RMS. And power to the RMS and not OVER the max.

**sansoo24** · 04-14-2005, 07:31 PM

First off look at the stickie at the top of this forun "technical websites." It will help out a lot.

Next > You need to find out what ohms the speakers are and what the true RMS power rating is. Next figure out if you want to wire the subs in parallel or series. YOu also need to know if the subs are single or dual voice coil.

With your pruposed setup if the subs are 4ohm SVC and the amp is 500x1 @ 4ohms then each sub only gets 250 watts. But if the subs are Dual voice coil (DVC) and wired in parallel the amp has to be stable at 2 ohms. Then theoretically you will get 1000x1 @ 2ohms and get 500 watts to each sub. And if the subs really do have an RMS of 400 then giving each of them 500 watts is a great setup. I beleive it is better so slightly over power a sub than it is to under power and try to make up for it by turning up the gain to high.

As far as tuning the subs. Turn your gain down all the way on the amp and turn up your head unit to the highest level you will ever want to listen to it with a CD that has a lot of BASS in it. Preferably a high quality bass CD. THen slowly turn up the gain on the amp until you hear distortion and turn it down slightly until you dont hear it anymore.

hope this helps out.

**Song0330** · 04-17-2005, 04:35 AM

Ah, I think I'm starting to understand it now. Kinda.

Okay, so here's the current situation. I went ahead and got myself a deal on a single Xtant X1244 subwoofer. It's a 12" dual-voice coil 500wRMS and 2000wPeak (dual 4 ohms).

Now, according to the SoundDomain subwoofer wiring guide, wiring both voice coils in parallel (as recommend) will produce a 2 ohm load.

If I understand correctly, that means I should be shopping around for a subwoofer amp whose specs state that it puts out 500wattsRMS @ 2 ohms (and/or 250wattsRMS @ 4 ohms), yes?

**WhiteRabbit** · 04-17-2005, 09:56 PM

500 at 2 ohms. if its only rated at 250 watts at 4 ohms, it may or may not be 2 ohm stable. but if its rated for 500 rms, you know what you are getting.

**Adam432823** · 04-21-2005, 05:10 PM

Originally Posted by Song0330

If I understand correctly, that means I should be shopping around for a subwoofer amp whose specs state that it puts out 500wattsRMS @ 2 ohms (and/or 250wattsRMS @ 4 ohms), yes?

Close... you nailed it with 500watts X 1 @ 2 ohms. The specs for the 4ohm load don't matter since you aren't running 4 ohm. You can't assume that all amps double their output when you halve the impedance. It doesn't happen too often actually.

**WhiteRabbit** · 04-21-2005, 05:55 PM

certainly not in the realm of entry level budget amplifiers

Thread: understanding subwoofers and their amps

LinkBack

Thread Tools

Search Thread

Display

understanding subwoofers and their amps

Bookmarks

Bookmarks

Posting Permissions