DiyMobileAudio.com Car Stereo Forum banner

1 - 20 of 61 Posts

·
Registered
Joined
·
59 Posts
Discussion Starter #1
Is 45w rms enough to drive a 90w rms 84dB speaker properly, not blow my eardrums properly but loud with sq?
 

·
Registered
Joined
·
646 Posts
It's more a question is 45w enough for you and how loud you like it and not the speaker. And be careful not to over drive the amp gain into clipping trying to make the speaker play louder than the 45w the amp can provide.

Since you already own the amp and not the speaker, you could try pairing the highest sensitivity driver you can afford. The higher it is, the louder it will play on 45w. For instance, the 84dB sensitivity speaker can play about 100dB as gijoe mentioned. But if you get one that is 90dB then 45w could play at 106dB.
 

·
Registered
Joined
·
7,372 Posts
45 watts is decent enough. You'd be surprised how much power you aren't using at average listening levels except for peaks and that's in milliseconds. Now if you find yourself riding near the edge of the amp's power and you're beginning to reach clipping more often, a bit more power will help, but just like there's no replacement for displacement, there's no substitute for higher efficiency. A comparative driver that's at least +3db more efficient can make a world of a difference.

Man & Machine... Power Extreme!
 

·
Registered
Joined
·
103 Posts
Bridge the channels and get full power (90 watts) to your speakers.
 

·
Premium Member
Joined
·
3,670 Posts
What formula do you use to calculate this?
1W gives 84 dB if the speaker I suspect 84dB/w :cool:
But that assumes the at 1 meter, which it is probably close to.

45w is about 16dB(w)
So 16+84 =100...

But if you assume that music has a chest factor between 13 and 16dB (x20 and x40 respectively), that means that you get 2 and 1 watts RMS respectively before clipping starts...

So my math says that 45W is comfortably able to get 87 dB(A).
Because 2w is 3 dBW... 84+3 = 87

That is about where I play the Mrs Subaru and it is at 30/35 and comfortable loud... uncomfortable for the boss though.

90dB(A) is also around the OSHA limit for long term session... so it is loud enough.
It will not be super loud, unless it is pushed higher and then clipping an distortion ensue... and if it is a wideband with a passive crossover then cranking up, does the tweeter a bit of smoke.

If the speaker is band limited like a mid range then it is more than enough, and a lot of SPL comes from the woofer and sub.
 

·
Registered
Joined
·
7,372 Posts
Because unless it has been determined that double the power is needed, it is just a waste of amp channels. That's not saying it won't be, but has it been tested yet?

What is the driver and how is it being used?

Man & Machine... Power Extreme!
 

·
Registered
Joined
·
7,844 Posts
What formula do you use to calculate this?
Doubling power yields 3dB more output.

Start with 84dB at 1 watt and go from there.
87db- 2 watt
90dB- 4 watt
93dB- 8 watt
96dB- 16 watt
etc.

Why not ?
It could be a waste of 2 channels of amplification that are needed elsewhere. If there are 2 spare channels, sure, bridge away, but I'm guessing those channels are needed somewhere else. Using the above as an example, bridging the channels will only give 3dB more in ouput, which is not significant.
 

·
Premium Member
Joined
·
8,977 Posts
Headroom for the win.
Buy another amp.
Can you explain why the headroom is necessary?

@bilboaudio if you haven't purchased the Pioneers components yet and already have the 45W/CH amplifier, I would suggest looking at a more efficient component set as @jrwalte stated. The Morel Maximo 6 are around the same price and are more sensitive. Probably about 3dB more sensitive if they were measured using the same standard.

That would take you from the 100dB output that @gijoe provided to 103+dB.
 

·
Premium Member
Joined
·
3,670 Posts
I would be looking at a more efficient speaker, or a larger amplifier, or a DSP or active cross over to allow you to run the lower notes into a dedicated woofer using a larger amplifier.


Can you explain why the headroom is necessary?
...
Mostly because the music will never be at 45W. The RMS rating is 45W, but the transcients of the music mean that peaks will be 45W and the RMS less than 1/20th of the peak.


...
That would take you from the 100dB output that @gijoe provided to 103+dB.
In reality it moves the 87 dB to 90dB if one is staying under the clipping level.
 

·
Registered
Joined
·
59 Posts
Discussion Starter #18 (Edited)
Thanks for all the the pointers, so basically it would probably be okay just not really loud and for more loudness with sq I should get a more efficient set or amp.
The morels were also mentioned on another thread but I really do no want to have to cut the factory wiring or run wire through the door if possible which I would have to with the external xover, I had a look at the wires in my car and it looks like a right nightmare to find the right wire and splice in etc, though I will do some more investigating and ruminate a bit more as I can get them at a reasonable price hmmmm.

Another set I had been contemplating were the Alpine s-s65c which are 88dB 80 rms and get good reviews on crutchfield, it was the frequency response only down to 70 Hz that had put me off when comparing to the Pioneers which state 32Hz.
 

·
Premium Member
Joined
·
3,670 Posts
Just use what you have then, and don't go wild on volume knob.

(No matter what number of watts you put in, if you turn the knob far enough clockwise you can run still out of power. So just resist going too loud.)
 

·
Registered
Joined
·
59 Posts
Discussion Starter #20
Does the speaker compare thing on crutchfield work, the pioneers sound like crap compared to the Alpines?
 
1 - 20 of 61 Posts
Top