SPL and dBs, what can I hear? - Axiom Message Boards

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Hi all,
this is my first time so be gentle. I'm a (very) amatuer audio-nut (with some science background) who'll be buying his first pair of axioms soon (either M3 or M22).

when I look at the frequency response graph, I can obviously see the decrease in response at lower frequencies. But at what level do I stop hearing? Does my hearing cutoff at ~80dB or is it 70dB? I'm trying to get a feeling for the impact of these response curves. Often, it looks like there is very little difference between curves for various speakers, yet people will hear significant differences.

can I use ~80db as a rough cutoff, then look at the lowest frequency each speaker will produce at that level? Is that a reasonable way to compare?

thanks,
blakelock

Actually, 70 and 80db is pretty loud.
The absolute limit of what the human ear can hear depends upon many factors, of which the most important is the ear itself. However, as the rating system goes, they use "zero" as the baseline for sound pressure levels not detectable by the normal human ear.

Can't recall the exact number but longer term exposer to sound over 80 or 85, certainly 90db, can be damaging. It's fine for short bursts like the quick loud scenes in movies. I think 120 is the safe limit for short bursts of loudness.

They basically use the graphs to give you an indication of how well the speaker does at consistently producing all the different frequencies of sound from lows to highs. You can see if a speaker has trouble producing the lower, bass sounds or how it performs with the high notes and midrange. A perfectly healthy, young human ear can hear frequencies from as low 20 Hz up to highs of 20 kHz

I'm sure more detail will follow but basically, a flatter graph tells you that the speaker is good at producing all of the frequencies at very close to the same sound levels. If there is a big dip anywhere, it means that you will not hear that frequency very well from that speaker. An upwards spike is equally bad. This changes how accurately you hear the sound as it's over or under emphasizing certain frequencies.

It is normal for a speaker to start to 'fade' as it hits the bottom end of the lows and up at the extreme highs but by comparing where it starts to take a nose dive, you can compare it to other speakers and see who produces better bass and so on.

Hope that answers your question.

I think he means 70 or 80 Hz. And you can hear much lower than that; that's why we all buy subwoofers. I think human hearing generally goes down to about 20 Hz or so, but you can feel below that.

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.... but you can feel below that.

Yea, so can the drywall seams in the house if you're using a 500/600 series sub.

But what about the 400, I wonder...

Hmmm, I bet he did mean Hz. Luckily my psychic intuition knew that and the answer was still in there. OK that was just luck.

Being newer to this stuff myself, It's easier for me to take a question at face value because I could easily have asked a similar question myself a year ago.

I wonder when my "I'm new here excuse" runs out?"

Mmmm.... about nowish.

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But what about the 400, I wonder...

I forgot about that one Ken, hopefully soon.

actually...i did mean dB! i should've listened to my intuition. i thought 100 dBs seemed pretty loud.

My point was, in general, what would be a good rule-of-thumb cutoff to gauge a speaker's performance based on it's frequency graph? I can certainly see that output levels roll off at low frequency but, for a given frequency, is a 10 dB drop "a lot" or will i still hear reasonable output at that frequency?

for instance, the M3 shows ~74dB output at 40hz (compared to 84-88dB for frequencies higher than 100hz). can i still hear the 40hz or does this much of a drop pretty much make it impossible to hear?

D'oh.

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for instance, the M3 shows ~74dB output at 40hz (compared to 84-88dB for frequencies higher than 100hz). can i still hear the 40hz or does this much of a drop pretty much make it impossible to hear?

Well, that depends. The M3's 74dBC output at 40Hz is measured from 3 feet away with a 1 watt input. At half a watt you'll get 71dB and at a quarter watt you'll get 68dB...at 3 feet! If you are sitting 8 feet away and you are listening to two of them, you may get ~65dB. To know whether this is adequate, you need to know what your ambient SPL is in your room and also how well you hear. If you are younger and have not abused your ears, you should easily be able to hear 40dB at 65dBC.

You should strive to have your music at least 10dB higher than ambient. If you are in an apartment located on the street, you may have an ambient noise level of 70dB so 65dB is no good. My basement which is well isolated still has an ambient noise level of 55 to 60dB (because of the compressor noise from my noisy fridge in the kitchen right up the stairs).

I hope this helps.

Blake, welcome. One point to keep in mind is that the frequency response curves are often measured in an anechoic chamber(rather than a room)which, depending on its size, doesn't give accurate results below about 80-90Hz. So, don't attempt to use those graphs to judge the low bass under 100Hz, since it will vary significantly when in-room reinforcement is present.

As has been mentioned, 80dB is actually a fairly loud level(ordinary conversation is maybe 60-65dB), and is about what I refer to as "comfortably loud". Even quiet rooms at home would have a background noise level of at least 40dB, so music would have to be louder than that to be even audible above the background.

thanks for all the responses/advice. i guess i'll just have to bite (or buy) the bullet and try a pair out in my house. i would love to add a sub to a pair of M3s or M22s but my wife has a strict upper limit of only 2 subs per household so i'm currently maxed out.

I also have a question about room layout and speaker placement but i think i'll start a new thread on it.

later.
blakelock

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So, don't attempt to use those graphs to judge the low bass under 100Hz, since it will vary significantly when in-room reinforcement is present.

True enough. However, I wonder if for comparative shopping purposes, it still might be useful considering that, after purchase, both would end up in the same room and would be effected equally by the surroundings.

For subtle to small differences, the room may create or cancel something in one speaker but not equally to another creating an unfair comparison, methinks. However, for a basic buyer, a major discrepancy in two speakers graphs could still show that one speaker has no chance to do deep base while another is more likely to succeed. For instance, one could probably safely use graphs of say, an m80 verses some bookshelf being pushed in a big box store that simply hasn't got the driver size to go below 100Hz. (It might be a wonderful speaker at it's design levels but was simply engineered to be accompanied by a sub to get lower than that.)

I definitely agree with the point you made but wouldn't want it misinterpreted by a newcomer that the low ends of graphs are not worth looking at although it's a question to see if I'm correct as much as a statement.

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My point was, in general, what would be a good rule-of-thumb cutoff to gauge a speaker's performance based on it's frequency graph? ...for a given frequency, is a 10 dB drop "a lot" or or will i still hear reasonable output at that frequency?

Blake,

The general industry standard for a comparative reference usable (flat) frequency response of speakers is +-3db (at 1 meter-on axis).

Yes, a 10db drop is a lot (usually found on the extreme, top\bottom end responses) and is generally not considered adequate acoustic output of the speaker system. It is there, but due to the higher db output of the total speaker system, it is very hard to hear and perceive. A 3db increase or decrease is where most people can detect an audible change...some are much more sensitive to as little as a 1db change. However, a 10db increase or decrease of acoustical amplitude is usually perceived as twice as loud or twice as soft. Thus, a 10db drop of a speakers end responses is "masked" by the overall higher average output of the system!

As others have stated, in-room responses, especially in the low-mid bass regions, can be reinforced by room boundaries and extend the usable frequency range of what is heard\measured! That can be good, or bad...depends on the quality and tonality of the boundary reinforcement. Electronic equalization can also "extend" the usable response of the system, but most often causes other undesirable auditory effects.

Hope this helps!

Ted