Easy (newbie) Watts & Speaker Question
So I got a deal on 2 pairs of Alpine SPX177R component speakers, to be used in the front and rear of my VW Eos.
The specs say they'll take from 75 to 300 watts RMS.
The amp I'm considering is the Alpine PDX-5 which delivers 4 channels at 75 watts RMS, and a 5th at 300 watts RMS (for a subwoofer upgrade in the future).
So each of the component speaks would get 75 watts RMS.
My questions are; With 75 watts being the low end of the speakers needs, will I be disappointed with their output? Is it better to hit a speaker with something in the middle of the Min/Max level?
I await your expert opinions!
TIA!
Lash
(I'm considering the Alpine amp because of the subwoofer upgrade option and 'cuz space is limited in the Eos.
Also please don't turn this into a Soundstage/Rear Fill debate)
So I got a deal on 2 pairs of Alpine SPX177R component speakers, to be used in the front and rear of my VW Eos.
The specs say they'll take from 75 to 300 watts RMS.
The amp I'm considering is the Alpine PDX-5 which delivers 4 channels at 75 watts RMS, and a 5th at 300 watts RMS (for a subwoofer upgrade in the future).
So each of the component speaks would get 75 watts RMS.
My questions are; With 75 watts being the low end of the speakers needs, will I be disappointed with their output? Is it better to hit a speaker with something in the middle of the Min/Max level?
I await your expert opinions!
TIA!
Lash
(I'm considering the Alpine amp because of the subwoofer upgrade option and 'cuz space is limited in the Eos.
Also please don't turn this into a Soundstage/Rear Fill debate)
Power handling means very little.
Whats the sensitivity of the speakers ?
This will tell you how 'loud' they will sound with a given power input.
EG;
Speakers 87db/w/m driven with 1 watt of power will produce 87db.
Speakers with 90db/w/m driven with 1 watt of power will produce 90db.
See if I get this next bit right
90db is double the percieved 'loudness'.
To get the 87db speakers to produce 90db, you will need 4 times the power, so 4 watts.
EDIT, to make your 75 watt amp sound twice as loud, you would need to increase it too 300 watts.
In a nut shell, 75 should be more than enough.........
Whats the sensitivity of the speakers ?
This will tell you how 'loud' they will sound with a given power input.
EG;
Speakers 87db/w/m driven with 1 watt of power will produce 87db.
Speakers with 90db/w/m driven with 1 watt of power will produce 90db.
See if I get this next bit right
90db is double the percieved 'loudness'.
To get the 87db speakers to produce 90db, you will need 4 times the power, so 4 watts.
EDIT, to make your 75 watt amp sound twice as loud, you would need to increase it too 300 watts.
In a nut shell, 75 should be more than enough.........
Re: Easy (newbie) Watts & Speaker Question
75W will be more than adequate for component speakers- should reach screaming levels if the rating of the amp is accurate. If the amp has built-in crossovers, which I suspect it does, high pass the components for around 80-100Hz, so they last longer than 2 years. 75W with bass pumping into them won't work, nor will it sound good. Let the subwoofer do what it does best, and don't expect it from the components.
Okay, to each his own.
75W will be more than adequate for component speakers- should reach screaming levels if the rating of the amp is accurate. If the amp has built-in crossovers, which I suspect it does, high pass the components for around 80-100Hz, so they last longer than 2 years. 75W with bass pumping into them won't work, nor will it sound good. Let the subwoofer do what it does best, and don't expect it from the components.
Lash said:
Okay, to each his own.
MadMutt said:
Hi,
97dB is double the percieved loudness relative to 87dB.
In other words 1 Bel = a doubling of percieved level.
+3dB in level requires double the power, not 4 times.
A 750W amplifier is twice as loud as a 75W amplifier.
A 75W amplifier is twice as loud as a 7.5W amplifier.
No they don't. 75W RMS, 300W peak.
http://www.abt.com/images/products/PDF_Files/spx177r_manual.pdf
87dB/2.83V/1m comes out as 84dB/W/1m.
Xmax for the woofer is 3.5 mm and its power handling is 40W RMS.
So 75W to 100W is probably as high as you can go.
As allways speakers can take very high unclipped peaks so very high
power can be used with care, the downside being any carelessness
can cause damage / expiration of the drivers.
/sreten.Infinite Baffle or free air. You mount them in the rear deck, or you build a baffle sealed to the rear seat back opening and put them in that. Mine blows through the seat no problem, but all I left was the seat and took out the panel in the trunk. I sealed off my rear deck, works well and actually overpowers the 4 door speakers badly on a 5ch 700w amp. I have 4 12s in it. Just seal trunk off from car with some deadening or whatever as best you can, and if you make a baffle you have to mount it sturdy. I figure I need double the drivers for IB but went a little overboard on this one now I have to get my comps working better. Going to swap amps and want to try 2 15s instead, lighter ones, because the subs I have are rather heavy and put out plenty anyway. This way you have no box. For the room my 4 12s take I figure I could make a box for a single 10. With 15s I will have more amp room also, and still my trunk is near empty.
Isobaric is much different and involves a box, though I suppose you could mount one IB but I can't see how it could ever work. The key to IB is more cone area and isobaric is half the cone area. Isobaric is mounting two drivers in tandem, cone to cone, that work together. So basically you have one cone and two voice coils (twice the motor on a sub in essence). IIRC you can use half the box for same tuning, but it takes twice the power to run. So it is mostly for when you must have a tiny box. I hate small boxes and low efficiency so I've never built one.
IB is all about moving air and no box at all (trunk room!), the world behind the driver is its infinitely large box. It must be at least say double what a sealed would be but should be more or open. You can use aperiodic, that is just limiting the air movement behind the sub. Say you put a sheet of batting on a frame and mount it behind the sub, it will tend to slow the air and limit higher excursion. That will kill off some low bass. Over excursion is always the limit in IB as you have no box air to support the cone. However IB tends to roll off on the bottom anyway, so aperiodic is often not that useful for SQ. You can do the same thing by venting a sealed box with a filter of some kind, it lets some air out and loosens the driver up allowing a little more low bass.
IB is all about moving air and no box at all (trunk room!), the world behind the driver is its infinitely large box. It must be at least say double what a sealed would be but should be more or open. You can use aperiodic, that is just limiting the air movement behind the sub. Say you put a sheet of batting on a frame and mount it behind the sub, it will tend to slow the air and limit higher excursion. That will kill off some low bass. Over excursion is always the limit in IB as you have no box air to support the cone. However IB tends to roll off on the bottom anyway, so aperiodic is often not that useful for SQ. You can do the same thing by venting a sealed box with a filter of some kind, it lets some air out and loosens the driver up allowing a little more low bass.
Thanks for all the info jol50,
My car's pretty small, and when the top is open it pretty much fills the trunk.
Being more of a SQ guy I'm not looking for extreme bass, but as it's my favorite frequency range I know I'll need something.
What would be ideal is a small unit that would fit in the ski pass-thru.
My car's pretty small, and when the top is open it pretty much fills the trunk.
Being more of a SQ guy I'm not looking for extreme bass, but as it's my favorite frequency range I know I'll need something.
What would be ideal is a small unit that would fit in the ski pass-thru.
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