Underpowering speakers?

[gdew]

I have a pair of JBL 4412s and am currently waiting for a Yamaha P3500s amplifier to arrive in order to power them.

These speakers have an RMS rating of 150 watts and the amp I have bought is rated at 375 watts (at 8 ohms). The problem I have the speakers, but the amp is going to take two or three weeks to come into the country.

In the mean time I thought I would try powering the speakers with an old cheap amp my parents had lying around (A pioneer sx-p520, which is an integrated amp from an all in one system.). I don't know what the rating of this amp is, but the sticker on the back of the speakers that would normally be powered by this amp says max power 40 watts, so I assume the amp isn't very powerful.

Anyway, I hooked it up and the sound is there but it is quite muffled, like a wet towel has been placed over the speakers. I am being careful not to clip the signal, but still I can make the sound quite loud, although the dynamics in the amplitude do seem to be limited. Given my speakers are new and haven't been broken in, my question is this constrained sound a product of the speakers not getting enough power, or something else (like them not being broken in or quality of the amp etc) and can driving speakers without enough power be damaging to the speakers (as long as they don't clip)?

Thanks

[Swerd]

To the best of my knowledge, using a low powered amp with speakers poses no danger to the speakers, as long as you avoid driving the amp into clipping. If the amp is clipping you might damage some speakers. It depends on how ruggedly the speaker drivers were built.

The JBL 4412s (at least those made in the 1970s) had a reputation for efficiency and rugged construction. They could be easily driven by amps under 30 watts and could also handle the power of amps of greater than 150 watts. I don't know if new ones are built to the same standards.

Your description of the sound being quite muffled, like a wet towel has been placed over the speakers. suggests that the problem may be due to something other than the lower power of the old Pioneer amp, or the newness of the speakers. The amp, or your sound source may be malfunctioning. If you are using a CD player, try switching to a different sound source such as FM radio, turntable, tape recorder if any of these are available. After the switch, is the problem still there? It may also be something as simple as a poor connection between the sound source and the amp. Look at the interconnect cables and make sure they are firmly connected. The RCA jacks on the old amp may be tarnished.

If the problem is within the amp, be patient and wait until your new amp arrives. But I doubt if you will damage those speakers.

[gdew]

Ok, thanks. That puts my mind to rest.

By the way, one thing is really confusing me. The amp I am using, it would seem, is about 1/9 the power of the amp I am buying. I chose the amp because its rating was well suited to that of the speakers, but the amp I am using is still producing a lot of sound from the speakers. The fidelity isn't there, but it can still shake the room. Why is this?

How can such a low powered amp driving such high rated speakers?

[Swerd]

How can such a low powered amp drive such high rated speakers?

Don't confuse the power output of an amplifier with the power "rating" of a speaker. Consider the speaker's power rating as the manufacturer's suggested minimum and maximum amplifier power values for the speaker. They are guidelines, not requirements for the speaker.

The minimum value is a reflection of the speaker's efficiency, measured by how loud the speaker is when driven by 1 watt under standard defined conditions. Most speakers deliver about 85 to 92 decibels (db) with 1 watt, where more db is louder. Note that loudness in db is not a linear scale, 3 db more is twice as loud and 3 db less is half as loud. All decent speaker manufacturers provide efficiency values for their products. The fact that your speakers are loud with a low powered amp probably means that they can deliver 90 db or more with 1 watt. As you've noted, that is loud. Typical listening levels are lower, in the 75-85 db range. And they involve continuous power levels of less than 1 watt!

The maximum power value for a speaker is the manufacturer's estimate of the power their speaker can take without getting damaged. One hopes it is a conservative number. It is a reflection of how ruggedly constructed the woofers and tweeters are. When speakers are over driven, usually it is the tweeter that fails first.

When you get your new amp, it should make quite a potent combination with those speakers.

[_Luke1_]

Many years ago I had a similar experience. I was powering a pair of bookshelf speaks with an old Technics receiver rated around 40 wpc x2. Then I got a par of CV AT-12's. A few years later I decided to get into HT and started into upgrading it all with a Denon Pro-logic receiver rated at 70 wpc. I never did get that HT off the ground, but just the upgrade for two channel to the Denon was astounding - the single biggest upgrade I've ever heard.

Even though the CV's were fairly efficient, they sounded so much better with more juice. Based on that, my bet is your new amp will improve things.

[jbangelfish]

And should provide you with whatever you are missing. Is that power rating per channel or total for the amp? If it is per channel, you might need to worry about too much power. I'm a power nut and like to give them what they can take but worry about overdoing it. Speakers can be damaged by underpowering and driving to clipping, or so I've read. I've never done it but I won't argue that it is possible. I believe it would be easier to damage them with too much power but you might damage your eardrums first.
I'm not so sure about every 3db being twice as loud. Twice the power is required for every 3db increase. I've never heard this described as twice as loud. I can't say that this is wrong but I've never heard it explained this way. I did not think that the decibal scale was an exponential one. Seems to me that I read somewhere that 1db was what human perception could discern as a difference in volume. If this is even close to the truth, then 78db would certainly not be twice as loud as 75db, etc. Anyone, feel free to explain this in a way that we can all understand.
One thing is fairly certain. You will like what your new amp does when compared to your old one, provided that you don't have any of the other problems that were mentioned and all wiring is correct.
Bill

[mtrycraft]

Note that loudness in db is not a linear scale, 3 db more is twice as loud and 3 db less is half as loud.

Just a small correction. While a 3dB increase in power is a doubleing in power, you need almost 10 dB spl increase to subjectively evaluate this as twice as loud. So, you need 10 times the power to perceive 2X loudness

[FLZapped]

I have a pair of JBL 4412s and am currently waiting for a Yamaha P3500s amplifier to arrive in order to power them.
.....
Anyway, I hooked it up and the sound is there but it is quite muffled, like a wet towel has been placed over the speakers.

Thanks

Hmmm, the last set of speakers I listened to that sounded like that had the tweeters blown.

Did you just buy these things too????

-Bruce

[skeptic]

Turn the volume down low. Turn the treble control high and the bass low. check that any high cut or hiss filter is off. set the fm tuner between stations with the interchannel muting off if possible or use program mateiral with lots of high frequencies like bells, violins, or a female voice. Put your ear right up to each tweeter. If you can't hear them, the tweeters are blown unless there are fuses protecting them which are blown. If the tweeters are not blown, listen to music with lots of high frequency content. Gradually increase increase the volume. If you hear the tweeters start to distort or crackle, they are damaged. With the bass down, this test does not require much amplifier power. Listen carefully to the mid range speakers as well. Breaking in the speakers or changing amplifiers is not likely to make a major difference in the overall tonal balance of the speaker. Check for tweeter level controls. Sometimes they are behind the grill cloth. Turn them up all the way if you have them and listen again. If you bought these new from a store, be prepared to return them for an exchange. If you bought them used, be preprared to negotiate with the seller for the cost of repair. It is entirely possible that you prefer speakers that are simply brighter sounding than these but from your description, there is the real possibility that something is wrong.

[skeptic]

From the photo on E-bay
http://cgi.ebay.com/ws/eBayISAPI.dll...category=14993
it is clear that the tweeter and midrange controls are behind the grill cloth. sometimes these controls fail and need to be cleaned or replaced for their respective speakers to work.