So I've noticed there's a repeated concept of PA speakers don't need as much power and some non-PA speakers are power hungry. At least I think this is a common theme.
Also in the glossary/sticky, it says what I already know from car audio that headroom is good, and that a chosen amp should output at least 50% more than a speaker RMS. We all know this keeps things cool and prevents clipping etc.
I've noticed a lot of instances where PA speakers with an RMS rating of between lets say 150-250w may only need 100-120w for example to sound good. Not disputing this at all, but here are my questions:

1. Is the reason people seem to be ok pushing less power than 150% of PA speakers RMS, to cut down on precious space and/or number of amps (and cost), and still have good SQ and avoid clipping? I think that is the case but couldn't find where it is said straight out.
2. If someone wasn't concerned with cost or space or number of amps, would it be "better" to employ an amp strategy with proper headroom? Or indifferent? I realize double the wattage is only 3db and that all watts are NOT created equal but maybe this strategy would add to the volume just enough at speed before distortion?

Thanks!

Edit: all this keeping sensitivity and ohms and wiring strategies equal if that makes sense

 

Great question. Thanks for posting it. I look forward to some quality responses on this as I'm about to diip my toes in the PA world.

Zach

 

 

Ill throw this out there, 75w fro an JL XD AMP to a 6.5" PRV 6MR500-NDY PA style speaker is the loudest cleanest 6.5' i have run.

Just my 0.02

 

So great example....that's a 250w RMS speaker. So if you threw 400w at it, and tuned it properly and controlled the gain properly, I doubt it would sound worse...would it be louder and just as clean? (all other things being equal or balanced out)

 

Haze is correct,
the thing you can do is compare some well known pro audio equipment and look at the strategies used there. FG12T75or example, most everyone has heard of a Marshall guitar Amplifier, and most people halve seen a "Marshall Stack" which consists of a head unit(amplifier) and one (1/2 stack) or 2 (full stack) speaker cabinsts, with 4 12inch speakers in each cab. one of the popular OE speakers in these cabs is the Celstion G12T75, speaker, 97 sens,12 inch, 8 or 16 ohm, with a 75 watt rms rating. usually wired series parallel to get 8 ohm, or series to get 16 ohm. the amp has a switch to correct for the proper load. the amp is 100 watt output, the speakers or 75 watt rms so there is a 25% headroom is the equation.this is very common with most "Pro Audio" equipment.
once these are applied to a motorcycle, a lot of this changes due to size, size of amps and power available from the bikes electrical system. these become limiting factors, so the process of trial and error comes in. Most of the pro audio 6.5 speakers sound great with between 75 and 125 watts to them and this is easy to get from a lot of amps.(I have tested several of the popular brands on this)
the larger the speaker gets, sometimes, the more power it likes, sometimes not. and what sounds good to you, might not sound so good to someone else. So testing is required.
the car audio stuff can't really count for bike comparison because cars can run a, ab amps and lots of batteries and have bigger badder charging systems to make it work. motorcycle specific speakers haven't been around for a real long time, and all the tech keeps getting better and better, so go out and have a listen to stuff and don't be afraid to ask questions!!!!
m

 

Great response, I run a Mesa Boogie myself so get the Marshall analogy!

So kind of my question #1 in the original post: is that 75-125 the bare minimum in order to maximize amp channels, save on power supply source from bike, etc? Question #2: How would a controlled 300w from a high quality efficient (class D lets say) JL amp sound if the RMS of that speaker was 200w? Would it sound great, just, "not necessary"?

 

I'm running Mmats 601.4s in my lowers which are rated at 75w RMS and 150w peak according to their website. They get stupid loud with the 140w I am pushing them with. On the other two channels of the same amp with 140w the WDX6 Motos also get crazy loud and they are coaxials.that claim to accept from 150 to 350 watts.

So in this scenario I have one set of coaxials and a set of PA speakers that get very loud very quickly (I had to turn the gains down real low). In looking at the specs they both have very high sensitivity ratings. The Mmats are rated at 95db and the Motos claim 103db.

I guess what I am thinking is that the sensitivity rating is one of the factors that can affect how many watts are really required to get good sound. I couldn't imagine running 350w to those Motos. They were so piercingly loud in the batwing fairing with 140w that I wound up getting a DSP and dropping the mids down a bit. That made them much warmer. In one test scenario several months back I had I had dropped the wattage down by about 25 and they seemed to sound warmer to me. This reminds me of a discussion we had a while back where folks were finding out that over driving speakers made them sound too bright. I guess when pushing speaks to the limit it makes sense that they wouldn't sound a clean.

I would think especially when it comes to 6.5" speakers that a lot of us use we are limited by how much air a diaphragm that small can push. Adding wattage to a 6.5 speaker is not going to make it sound like an 8 ro 10 inch unit.

All of this and $4 will get you a sausage biscuit at Bojangles...

 

Maybe search back a few months. I think it might have been Gypseye that had tested this theory and found that adding wattage after a certain point caused the speakers to sound harsher, especially the highs. I think he said when he backed the wattage down from overkill they sounded warmer.

Another angle to this line of thought is when you amplify a signal you amplify EVERYTHING, meaning the musical signal and the noise that is always present. If you amplify an audio signal more than is necessary you will also amplify the noise more than necessary.

 

Key to remember when dealing with speakers when pushing them to those limits is crossover points,
Bandpassing at hp and lp is essential

adding edit.... the harder you push a speaker/amp combo, the narrower that band gets