Getting mixed messages on what happens to ohms, watts, when I add speakers.

[scooper77515]

Re: Getting mixed messages on what happens to ohms, watts, when I add speakers.

For what it is worth...we are currently listening to radio at volume level 6 on the float. We hit 10 or 12 while under power. So there is plenty of power left. We are playing way down low.

Been playing it for 4 or 5 hours now with no problems.

 

[mcgyver210]

Re: Getting mixed messages on what happens to ohms, watts, when I add speakers.

Before anyone says it Im still getting used to this concept in not posting on older post & I just realized this is an older post Sorry Ill try to watch dates of post better before posting.

I tried to delete but can't

 

[bruceb58]

Re: Getting mixed messages on what happens to ohms, watts, when I add speakers.

I remember this thread. A ton of wrong info in it.

 

[bruceb58]

Re: Getting mixed messages on what happens to ohms, watts, when I add speakers.

duplicate post

 

[dyna962007]

Re: Getting mixed messages on what happens to ohms, watts, when I add speakers.

Wow guys, I see that many of you are attempting to help this gentleman and thats good but much of the info is incorrect or just not relayed properly due to these short posts that are hard to articulate a point.

Two major issues I see that have not been discussed here and that weigh heavily upon his questions.

1. Many Subs now are DVC or dual voice coil. Depending upon how they are wirred, you can achieve multiple impeadances from the same woofer.

2. All this talk of power amps and speaker and max output, max power, etc etc is very inexact.
We are simply wasting our time talking about amps or speakers if we are not talking strictly in terms of RMS and NOT peak power ratings.
I ASSURE you he does not have a 400 watt per channel amp as advertised.
Perhaps 400 PEAK or 400RMS total divided by 4 = 100watt RMS per channel which by the way would be a very nice amp.

Please provide some updated info about your amp and speakers.
What is the RMS rating into 4 ohms and 2 ohms per channel?
Mike

 

[scooper77515]

Re: Getting mixed messages on what happens to ohms, watts, when I add speakers.

I ASSURE you he does not have a 400 watt per channel amp as advertised.
Perhaps 400 PEAK or 400RMS total divided by 4 = 100watt RMS per channel which by the way would be a very nice amp.

You are correct. I have since blown that amp, not yet knowing what is wrong with it, will take it apart soon to find out what.

But it was not a marine amp, so I replaced with a marine amp that is actually a little bigger (600 watts, or as you called it in previous post, 600 PEAK or 600 RMS). I wired it up better than previous owner. He had it wired through the rca cables, and it was only playing all four speakers from right front channel, and sub through right rear channel.

I wired it with all 8 wires so now have 2 left speakers on left front channel, etc. And sub on 2 rear channels. Sounds MUCH better, and actually has "stereophonic sound"

 

[wire2]

Re: Getting mixed messages on what happens to ohms, watts, when I add speakers.

.... I replaced with a marine amp that is actually a little bigger (600 watts, or as you called it in previous post, 600 PEAK or 600 RMS). ....

They're not the same thing.
Peak is a measurement between the top and bottom of a sine wave, RMS is the actual or effective power. It's a trig calculation of 70.7% of peak.
Just like the AC in a wall plug is 115 volts RMS, but 141 volts peak.

You can't use Ohm's law to accurately calculate speaker power. Speakers are rated in xx watts at 4 or 8 ohms impedance. That's not the same thing as resistance. Impedance takes into account the inductive reactance of the load (voice coil), and the value varies with frequency. The actual ohmic resistance of a large speaker's voice coil is near zero, it's just a length of copper wire.

The bottom line is, speaker impedance should be matched to amp impedance for an efficient power transfer.

One other note, if an amp was actually feeding 600 watts of power to a set of speakers, the amp would draw over 50 amps from the battery. You'd need #6 awg cables to power it.

 

[scooper77515]

Re: Getting mixed messages on what happens to ohms, watts, when I add speakers.

I am not an electrical engineer, and personally don't care much for getting into the argument of what watt is what watt...

My amp says right on the box "Class AB 600W Bridgeable 4-Channel Marine Amplifier"...http://www.bestbuy.com/site/Sony+-+...fier/8246846.p?id=1169512106756&skuId=8246846

As far as I am concerned, it is a 600W amp. Not really sure why I am thinking this, or calling it this, but I will stick to it

Yes, I know it doesn't really push 600W, but if I tell everybody it is a 60W amp, they will think I am a wuss. My stereo ALONE pushes 52W (again, according to the box the stereo came in.)

Here are the actual specs from the amp box...

# 60W RMS (continuous) x 4 @ 4 ohms
# 70W RMS (continuous) x 4 @ 2 ohms
# 60W x 2 RMS + 140W x 1 RMS @ 4 ohms bridged

...which brings me back to the original question about putting 2 4ohm speakers on each of the front 2 channels.

It appears to be working well, and sounds great, so I will continue doing it.

Now, another question...since the original amp appeared to be wired so all 4 front speakers were wired to only the left front channel, could that be what caused to to fail?

 

[bruceb58]

Re: Getting mixed messages on what happens to ohms, watts, when I add speakers.

...which brings me back to the original question about putting 2 4ohm speakers on each of the front 2 channels.

Since you put two 4 ohm speakers in parallel on a channel, you are now driving 2 ohms on that channel which the amp is capable of and you are fine.

Now, another question...since the original amp appeared to be wired so all 4 front speakers were wired to only the left front channel, could that be what caused to to fail?

Possibly. You were then driving the equivalent of 1 ohm.

 

[fishrdan]

Re: Getting mixed messages on what happens to ohms, watts, when I add speakers.

...which brings me back to the original question about putting 2 4ohm speakers on each of the front 2 channels.

Either way you wired them will be fine, wire them in series and they are running at 8 ohms, wire them in parallel and they are running at 2 ohms. 8 ohms cuts the power by 1/2, 2 ohms doubles the power, or something like that as it looks like your amp limits the power while running at 2 ohms.

since the original amp appeared to be wired so all 4 front speakers were wired to only the left front channel, could that be what caused to to fail?

Possibly. You were then driving the equivalent of 1 ohm.

Could have been a 1 ohm load, or a 4 ohm load, or a 16 ohm load, depending on if they were wired parallel, series/parallel or series. But yeah, sounds like the PO did a hack job on the installation so anything is a possibility for blowing the amp.

 

[scooper77515]

Re: Getting mixed messages on what happens to ohms, watts, when I add speakers.

Besides, it was a regular Kicker car amp, not marine-grade. And I know he took the boat to the car wash on the way home and just nailed it with the hi-pressure hose, and there is no way that amp stayed completely dry for 2 summers of that.

Just moved most of our furniture into our new house yesterday. When we get settled in, tearing that amp apart is one of my planned projects. If I can get it to work again, it will fit GREAT in my Maverick car.

As for the wiring, I have the speakers on separate wires directly from the amp. So, I would guess that is "parallel".

Glad I did it right, without even knowing it!

 

[Lyle29464]

Re: Getting mixed messages on what happens to ohms, watts, when I add speakers.

I think I have learned more from this thread than any other in years. Thanks

 

[scooper77515]

Re: Getting mixed messages on what happens to ohms, watts, when I add speakers.

Yes, I agree. Got a lot of back and forth, but it all came out in the wash. Makes much more sense now.