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What do these specs mean?


Apendecto

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Posted

Showing my ignorance once again...

 

I'm looking at buying a cab and is has these specs:

 

Sensitivity: 100 dB @ 1W1M

Frequency response: -3db @ 61Hz and 5kHz

 

I looks like it puts out 100 dB at one meter with one watt of power and it's frequency response falls off 3 dB at 61 and 5k Hz, but what does that actually mean?

 

Yo.

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Posted

The higher the sensibility the louder at equal power.

-3 dB in sensibility = twice the power required for the same output.

 

Frequency responce is the range of the cab. For a bass cab you're looking at getting as much lows as possible.

They usually measure it at -3 dB because it's a noticeable loss. If you go lower than the bottom number you will still get lows but with dramatic attenuation.

Transformer_InterstageTestFC1.jpg

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Posted

Assuming those specs are accurate (never a given), it also tells you that you have plenty of lows and plenty of highs right in front of the cabinet when feeding the cabinet 1 watt. Unfortunately there are so many things that the numbers don't tell us that in the end it is almost better to completely ignore them and just listen. Wait, did I say almost? I shouldn't have.

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Posted

 

Assuming those specs are accurate (never a given), it also tells you that you have plenty of lows and plenty of highs right in front of the cabinet when feeding the cabinet 1 watt. Unfortunately there are so many things that the numbers don't tell us that in the end it is almost better to completely ignore them and just listen. Wait, did I say almost? I shouldn't have.

 

 

I figured...

 

Thanks.

 

Yo.

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Posted

 

Assuming those specs are accurate (never a given), it also tells you that you have plenty of lows and plenty of highs right in front of the cabinet when feeding the cabinet 1 watt. Unfortunately there are so many things that the numbers don't tell us that in the end it is almost better to completely ignore them and just listen. Wait, did I say almost? I shouldn't have.

 

 

As usual I completely agree with you!

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Posted

How do those number compare to these?

 

100 dB SPL @ 2W1M (-6dB @ 25Hz and 3khz)

 

(Assuming number mean something and I'm just trying to understand what they mean, not what a cab sounds like.)

 

Yo.

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Posted

 

How do those number compare to these?

100 dB SPL @ 2W1M (-6dB @ 25Hz and 3khz)

(Assuming number mean something and I'm just trying to understand what they mean, not what a cab sounds like.)

Yo.

 

 

been trying to understand this...and it seems from the above there are different parameters and benchmarks

i would try to get them all the same...ie

1M and -3dB

just so i can understand as well..

those figures for 2M and -6dB seem to suggest more power/music sound

but the attenuation on the frequency response seems greater than -3dB...so you may not hear those frequencies..

francois summed it up nicely:)

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Posted

 

How do those number compare to these?


100 dB SPL @ 2W1M (-6dB @ 25Hz and 3khz)


(Assuming number mean something and I'm just trying to understand what they mean, not what a cab sounds like.)


Yo.

 

 

That's like apples and oranges.

 

For one, this cab needs twice the power to get 100dB @ 1 meter. (!)

 

25Hz looks nice, but take another look at the graph JA posted - they just point to another spot on the curve to make it look as if it plays lower. Besides, 25Hz isn't exactly... useful. They state -6dB instead of the semi-standard -3 roloff point.

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Posted



Besides, 25Hz isn't exactly... useful.

 

Hey!!

 

:mad:

 

 

;)

 

Robin is right - except for, well....

 

This spec is rolled out often for those hunting for a sub or an augmenting cab.

 

It's just barely useful information as unless you know the shape of the curve you cannot assume any kind of performance specifics.

 

If you look at JazzAd's performance curve graphic you'll notice it shows a -6dB drop off at 10 Hz - but that curve begins at 30 Hz. The decline in response covers an octave and a half. Not so good.

 

You should always be looking at this curve as it pertains to a cabinet as opposed to the driver alone, and watch for where the curve starts its downward slope - or knee - this will tell you where you can expect the most from a cab.

  • Members
Posted

 

How do those number compare to these?


100 dB SPL @ 2W1M (-6dB @ 25Hz and 3khz)


(Assuming number mean something and I'm just trying to understand what they mean, not what a cab sounds like.)


Yo.

 

 

 

It's not hard to normalize those numbers to the typical specs (1W/1M, -3dB). Doing the conversion, this cabinet would produce 97dB 1W/1M and the -3dB points would be about 28Hz and 3.375kHz (assuming a vented cabinet). Supposing that these specs were accurate, this cabinet would be slightly quieter for the same input power but it would have considerably more bottom end and a slightly rolled off top end as compared to the other cab you mentioned. Of course, this is only really valid on axis and in the environment where the testing was done and at low power. The low end response numbers would be quite different for a cab tested in an anechoic chamber as opposed to the same cab measured in a typical room. (free space as opposed to 1/2 space loading). These tests don't take harmonic distortion or polar patterns into account as Kindness alluded to earlier. These factors are really important in how a cab sounds in the real world.

 

The standard measurement technique used by pro audio manufacturers and endorsed by the AES is measurement at 1W/1M, anechoic, with the -3dB points quoted. They use -3dB because it's the standard break point in filter theory. It's basically the point where the response begins to take on its ultimate rolloff slope and happens to be the 1/2-power point as well.

 

Bass cabinet manufacturers have a tendency to use whatever specs make their products look more desirable as opposed to adhering to a standard. It's {censored}ing bull{censored} if you ask me. Specs can be quite useful but unless there's a standardized way to arrive at them, they're largely useless.

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Posted

Hey!!


:mad:


;)

Robin is right - except for, well....


This spec is rolled out often for those hunting for a sub or an augmenting cab.


It's just barely useful information as unless you know the shape of the curve you cannot assume any kind of performance specifics.


If you look at JazzAd's performance curve graphic you'll notice it shows a -6dB drop off at 10 Hz - but that curve begins at 30 Hz. The decline in response covers an octave and a half. Not so good.


You should always be looking at this curve as it pertains to a cabinet as opposed to the driver alone, and watch for where the curve starts its downward slope - or knee - this will tell you where you can expect the most from a cab.

 

You can actually interpolate (extrapolate?) the rolloff curve of the cabinet from the -3dB points or any other points to a reasonably accurate degree assuming you know whether the cabinet is sealed or vented. If you're a nerd like me, that is....:D

 

But overall, you're totally right. Manufacturers use all kinds of trumped up specs to try sell stuff..

 

Have you made any progress on the project we talked about last spring?

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Posted

 

... they're largely useless.

 

 

I've been trying to figure these out for a while, thought I'd ask here and came to the same conclusion you gave me.

 

So it's a selling point to make the cab look good on paper?

 

Yo.

  • Moderators
Posted

 

I've been trying to figure these out for a while, thought I'd ask here and came to the same conclusion you gave me.


So it's a selling point to make the cab look good on paper?


Yo.

 

 

It basically is a marketing tool and in today's market you are damned if you do and damned if you don't. There is no consistency or standardization in measurements and the most relevant information is often omitted, but if you don't publish "measurements" people react more adversely than they do to worthless measurements.

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Posted

Manufacturers use all kinds of trumped up specs to try sell stuff..


Have you made any progress on the project we talked about last spring?

 

It'd be awesome to hold bass cab manufacturers to the standard SR guys use - far more realistic info there.

 

Indeed I have - balanced jazz pups are in my hot little hand, wound to 100 ohms. Only concern I have is whether there is enough current generated to push a decent signal out of a 12:1 transformer to use as a Hi Z signal.

 

I have the option of taking each pup up to 200 ohms if there isn't enough juice in 100.

 

I need to get a bass done to mount these little babies in..... :rolleyes::D

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