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speaker wattage question

Started by Bob Hoffmann CLC#96, April 11, 2014, 04:09:38 PM

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Bob Hoffmann CLC#96

Guys,
I'm planning on installing a 200 watt radio in my 70 conv. The front speakers I'm looking at are 60 watts each.
The rear speakers are 100 watts each. Is this a compatible situation? Bear in mind I'm limited on choices due to speaker locations & sizes. I'm NOT drilling any holes.
Bob
1968 Eldorado slick top ,white/red interior
2015 Holden Ute HSV Maloo red/black interior.
             
Too much fun is more than you can have.

Eric DeVirgilis CLC# 8621

#1
Hello Bob,

The ratings on the speakers are an approximate nominal rating for maximum suggested amplifier power. Most normal listening requires very little power - perhaps a few watts, most times using only a fraction of a watt, depending on the sensitivity of the speakers.

Using a higher powered amplifier will not result in any harm, so long as you're not abusing the system to the point where the speakers begin distorting from being overdriven.

In any case, you should be fine with the application as you have described.

*FYI: Unlike home entertainment amplifiers, automotive amplifier power ratings are not subject to the FTC power rating requirements of 1974 and as a result, most output "ratings" of automotive amplifiers are grossly overstated and misleading.
A Cadillac Motorcar is a Possession for which there is no Acceptable Substitute

76eldo

Bob

A 200 watt stereo generally means that it will put out 50 watts to each of your 4 speakers at peak volume. If you were looking at a high end home audio system or a PA for use in a band the ratings and what matches what would matter. Here is doesn't.

The unit is capable of making 200 watts, the speakers you are mentioning will handle more than 50 watts each so you are ok.

Brian
Brian Rachlin
Huntingdon Valley, Pa
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado

TJ Hopland

In case you want to know more about amps and speakers:



In general having more amp than the speaker can handle is the way to go.   When an amp hits its maximum output its called clipping.  When an amp clips its no longer putting out a variable signal that makes the speaker move in and out, it sends DC power to the speaker which either makes the speaker push out or in and stick there.   This is VERY bad for the speakers and will destroy them very quickly.   As long as the amp never reaches its max output (clips) the speaker will still get a variable signal and keep moving.   

If you have a 500 watt speaker and a 5 watt amp you could probably clip it for a fairly long period of time and not damage the speaker, most likely the amp would give up first.   Problem with that setup would be that a 500 watt speaker would not likely be very efficient (sensitivity in the specs) meaning that it may take that entire 5 watts to get a decent level out of it so the amp would be working very hard and clipping often which besides shortening the life of things would not sound good because when it clips you are no longer reproducing the sound.   

An inefficient speaker would be anything with a sensitivity rating below about 92 db.   They can play games with that spec too by not telling you how it was measured and at what frequency.  You would usually assume it was rated at full range and 1 watt 1 meter but not always.  If they don't tell you how they can slant it how ever they want.   So a speaker with a 92 rating means that with 1 watt of input power it will make 92 db of sound which is above normal conversation levels.   Where it gets more complicated is the power vs output uses the inverse square law.  Its sort of an exponential  thing so 92db at 1 watt.  To get noticeably louder it would have to go to 95 db and need say 3 watts.  These are not the real numbers, just an example to give you an idea of how it works.   Louder 98 db so 9 watts, 101 may be 35 watts, 104 may be 90 watts, 107 may be 200 watts and so on.  SO this is where the power handling of the speaker becomes important, you want to get 120db rock concert levels from a 88 db sensitivity speaker it better be able to handle a 1000 or more watts and you will need at least that much amp to drive it.   If you had a 101 db speaker you could maybe do it with 50 watts.    This is also where they get you with many amps when they are trying to sell you on a 'better' model.  The standard model has say 20 watts but the premium model has 35 watts.    That small a difference is not going to even be noticeable with most speakers.     

If you have a 5 watt speaker and a 500 watt amp most likely the speaker is going to be very efficient.  Very efficient would be a sensitivity above 100 db.  So at 1 watt the speaker is going to be able to be louder than most people will ever want it so the amp will barely be working.  Sure you could turn it way up and send it more than 5 watts which will kill the speaker so its not an ideal setup if it could accidentally be turned up.   it would sound good till you blew it up though unlike the reversed situation given above.   That is why you would usually more closely match the amp and the speaker and why knowing the sensitivity and how loud you need it to be are all part of the puzzle.   

Many modern amp designs are 'smart' and have clip limiters that sense when the amp is about to clip and will then automatically lower the overall level or perhaps limit the dynamic range (usually reduce bass) to prevent it from actually sending DC to the speaker which also makes the sound less bad during those situations.    Guessing there are a lot of rock bands and car stereos that run most of the time on these limiters.   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Eric DeVirgilis CLC# 8621

Nice to see the CLC boasts a few audiophiles in its ranks.

TJ - Bob's head is going to be dizzy after reading your thesis!  ;) ;D
A Cadillac Motorcar is a Possession for which there is no Acceptable Substitute

76eldo

The bottom line on Bobs question is that it will work.

He's a California guy so it's safe to assume that a Beach Boys cd at moderate volume will sound just fine.  8)

Brian
Brian Rachlin
Huntingdon Valley, Pa
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado

Walter Youshock

These two hobbies seem to go hand-in-hand.  Doug Houston is a another CLC member who is big into vintage audio.

Cadillacs=Summer hobby
Audio=Winter hobby
CLC #11959 (Life)
1957 Coupe deVille
1991 Brougham

Eric DeVirgilis CLC# 8621

...and can be just as expensive as Cadillacs!  :o

How about a show & tell thread for Cadaudiophiles or Audiophilllacs?  ;D
A Cadillac Motorcar is a Possession for which there is no Acceptable Substitute

Walter Youshock

My first tube radio was in the '57.  Been hooked ever since. 

If you take into consideration the era your collectible Cadillac was built, the car was but one aspect of "the good life".  Hi-fi and stereo were just as much products of the '50's and '60s as tailfins, chrome and Magic-Mirror acrylic lacquer...

I have one console to go with the '57 and another waiting to be matched with the '62 Fleetwood I have yet to find...

Both are great hobbies that can bring great satisfaction.  And there is so much work you can do yourself on the cars and audio equipment.  And there is no shortage of advice or help with either pursuit.

And, now back to our regularly scheduled topic...
CLC #11959 (Life)
1957 Coupe deVille
1991 Brougham

Bob Hoffmann CLC#96

Guys,
Thanks to all of you for your great replies.
Bob
1968 Eldorado slick top ,white/red interior
2015 Holden Ute HSV Maloo red/black interior.
             
Too much fun is more than you can have.

txturbo

More importantly....you need to match the ohm rating of the speakers and the radio.
D. Roden
1956 Coupe De Ville PINK
1963 Cadillac Sedan De Ville

TJ Hopland

Short version of the ohm thing....

Amps have a minimum impedance (ohm) rating.   Going lower than that is very hard on the amp.  This can happen if you hook up more than one speaker to the same output or just by wacky combinations of amps and speakers.

Going higher than the minimum rating is not in itself bad but it reduces the maximum output of the amp so you could end up with an overload condition just because of the reduced efficiency.  If you are a little off its fine like say a 4 ohm minimum amp running an 8 ohm speaker but say you have a 24 ohm speaker on an amp that is just rated at 4 and 8 ohms you may have a problem.   

Either way if you stress the amp bad and sometimes unpredictable things could happen to both the amp and speaker. 

Same rules apply to solid state as tubes.   With tubes usually what can be damaged is the output transformers which especially now days is the expensive and hard to reproduce part.   Many commercial tube amps had multiple output taps so you could match the output to the load.   Some solid state amps have a switch but I have never bothered to look and see what it actually does.  Could be something very basic like shunting an internal loading resistor.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason