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Dmax
01-16-2006, 11:27 AM
I dont quite understand what speaker manufacturers are saying when they write the frequency response of a speaker followed by this ( - 3dB) , what does this mean?

GMichael
01-16-2006, 11:28 AM
I dont quite understand what speaker manufacturers are saying when they write the frequency response of a speaker followed by this ( - 3dB) , what does this mean?

What they are saying is that, if the volume doesn't dip more than 3db then they are counting it. If a speaker dips from say 90 db to 87 db at 50htz then they say the speaker goes down to 50htz -3db.

Dmax
01-16-2006, 11:47 AM
What they are saying is that, if the volume doesn't dip more than 3db then they are counting it. If a speaker dips from say 90 db to 87 db at 50htz then they say the speaker goes down to 50htz -3db.Now I see, Thanx :)

bfalls
01-16-2006, 12:08 PM
As you've probably heard on this forum a 3db increase in volume requires twice the power. Thus, in electronics -3db is known as the "half power point". It had been general practice for manufacturers to give frequency response for their speakers at these points. Some speaker manufacturers may give response with a +/- 2db, or 1db range to show their speakers are more accurate with better tolerances and a flatter response. Other manufacturers provide their response with higher tolerances, such as Bose with +/- 10db, to hide poor accuracy or roller-coaster like frequency response. Although a smooth full-range response may provide a glimpse into the speaker's accuracy, there are many other factors (impedance, power-handling, resonance, dispersion, etc...) which combine to make a truly great speaker.

Dmax
01-16-2006, 12:23 PM
As you've probably heard on this forum a 3db increase in volume requires twice the power. Thus, in electronics -3db is known as the "half power point". It had been general practice for manufacturers to give frequency response for their speakers at these points. Some speaker manufacturers may give response with a +/- 2db, or 1db range to show their speakers are more accurate with better tolerances and a flatter response. Other manufacturers provide their response with higher tolerances, such as Bose with +/- 10db, to hide poor accuracy or roller-coaster like frequency response. Although a smooth full-range response may provide a glimpse into the speaker's accuracy, there are many other factors (impedance, power-handling, resonance, dispersion, etc...) which combine to make a truly great speaker.Cool ! :D

audio_dude
01-17-2006, 10:08 AM
Ya, I once went to a specialty audio store and asked the clerk there: "i'm looking for a floorstanding speaker less than $700 with a frequency responce of 30-20 000htz, he looked at me wierd for a second and said: 'I'll go a step better and get you a speaker that goes to 20 htz!' "I said ok, and he led me to a room with a ton of speakers, he showed me some VERY small floorstanding speakers that were right in the corner up against a wall. then I put a CD that plays a sound wave from 20- 20000htz, at the stard I couldn't hear a thing, then at 30 htz, it was all buzzy and afull, it was fine to about 150 htz, then it dipped UP and Down all over the place, in some places, the sound just stopped! so I walked out.

kexodusc
01-17-2006, 10:25 AM
Good answers so far.

I tend not to worry too much about the frequency response of speakers. 1 dB is the reported smallest variance in volume humans can detect with consistency. Many can't however (and I believe I'm one of them). So +/- 3 dB is very good.
More important here is the shape of the curve. That is, if a certain range of frequencies was -3db, then the next adjacent range was +3 dB, well now you've got a 6 dB variance. This will really determine the tonal characteristics of the speaker.

Be careful when looking at bass extension (or LFE extension). Typically, manufacturers use a rather loose DIN 45 500 standard. What this means is they make an assumption that the average room provides room gain of approx 10 dB (which is in between in between 9 and 12 dB, and is a nice round figure, but probably a bit generous more often than not), and further add a -3 dB to come up with a -3 dB "typical in room" response. This is pretty bogus. That means the lowest range reported could be as much as 13 dB lower than the average. Whoop-dee-crap.
The low number reported in the +/- 3 dB figure is more reliable for determining which speaker will appear to have more bass.

bfalls
01-17-2006, 11:01 AM
The readings are probably taken with the sub in the middle of the room. Depending on the style (front panel, or floor output) the sub's output can increase 6db or more by placing against a wall or in a corner. Also depends on listening position and standing waves. If you're sitting in a null the bass can be much less than when sitting in a peak.