Understand Freq. Response

Discussion in 'Amps and Cabs [BG]' started by progplayer, Dec 27, 2001.

1. progplayer

Nov 7, 2001
I'm not good at this stuff but want to learn what it all means. When I look at cabs and they list freq response how do i translate this stuff?

Example I was comparing the SWR 2x10 with the Eden 2x10.

SWR = -3db@45hz-15khz
Eden= +/-2db@48hz-14khz

2. throbbinnut

Those numbers you put down are the frequency responses for those 2 cabinets. The "dB" is the decibel and it is used to describe the ratio of 2 sounds levels, voltages, whatever. Usual terms are "-3 dB", which means "sounds a little lower".

So if you had a tone generator and played it through the cabinet, every sound between 45 Hz (low rumble of the E string is 41Hz) and 15,000 Hz (very high pitch, like the highest squeal you can do with your voice) would sound about equal, and once you went below 45 or above 15,000 Hz, the volume of sound put out by the cabinet would decrease, even though the wattage going into the cabinet may still be the same.

The "+/-2 dB" means the sound level will "vary just a little bit, up and down" between 48Hz and 14,000 Hz.

Not a big difference at all between the 2 cabinets, I would think. You can barely here the difference between 2 sound levels that are 2-3 dB apart. And the difference between 45 and 48 Hz and 14K and 15KHz is not much.

The next thing to worry about is the efficiency of the cabinet - how many dB per Watt at 1 meter? The higher the number, the louder the cabinet is for a given amount of power.

Chris

3. progplayer

Nov 7, 2001
hmmmm, some say the eden puts out more bass than the swr...hmmmm

4. geshel

Oct 2, 2001
Seattle
Well, if the Eden has a higher sensetivity rating, then it might appear to put out more low-end. Also, within that +/- curve, which frequencies are + and which are - (even though it's pretty slight) can have an effect on the character of the sound the cabinet produces.

Sensetivity ratings are usually given as dB 1w/1m, which means the sound level in dB measured one meter away from the cabinet when the input is one watt. They don't however say what frequency they use to test this out, which can have an effect. Sometimes they also list it as dB 2.83v/1m which means they use an input of 2.83v instead of 1w - but 2.83 volts into 8 ohms is one watt. It happens to be TWO watts into 4 ohms, so manufacturers sometimes pick the method that yields the highest numbers.

5. progplayer

Nov 7, 2001
dear lord, over my head...hahahahaha. maybe i should have majored in electrical engineering and not law...

6. EString

Nov 20, 2000
Los Altos, CA
Wouldn't a better major be physics?

7. throbbinnut

No. Electrical Engineering is the greatest major..... of all time.

Chris

8. ihixuluSupporting Member

Mar 31, 2000
South Shore MA
Would it be fair to say that freq response ratings only tell you how the cab performs at the extreme low and high frequencies and nothing about its character?

As for sensitivity: If a cab is 99db at 1w/1m does that mean that all frequencies increase in volume equally as more power is added or do the cabs resonances play a greater role as wattage increases?

How come no one puts out a freq response curve for cabs like they do for mics?

while I'm at it, how come Santa didn't bring me an Aggy DB750?

9. Christopher

Apr 28, 2000
New York, NY
I think some do. But I don't know of any off the top of my head.

10. geshel

Oct 2, 2001
Seattle
Actually, in ported cabinets, what tends to happen is that the effects of the port decrease as the power goes up. This is because the wind resistance in the port goes up. So the port resonance isn't as effective and the very low end is diminished. This of course varies with different box/port designs.

Also: Physics is good for understanding this type of stuff, but actually, an EE degree is really the way to go. Once you understand filters and resonant systems, you look at a speaker system in a whole new light. Or, if you want to get into the fluid dynamics and materials involved, mechanical engineering is the way to go.

11. progplayer

Nov 7, 2001
Well I'm having second thoughts with this Eden 2x10XLT. I have it matched up with my Goliath III and it sounds good. Lots of lows BUT at the store I saw they had a JR Goliath III matched with my swr cab that I own. So I went home and got my eden wt-600 and my penta and brought it to the store to try it out.

I hear a difference now and I am starting to feel that the Eden was a mistake..... could it be SWR cabs should be matched??? I don't know...i'm confused.

I'm thinkin I should exchange the Eden for the SWR JR Goliath III....

12. Richard Lindsey

Mar 25, 2000
SF Bay Area
Carvin does. Perhaps unwisely, because the graph makes it clear where their low end response starts to fall off significantly (rather higher than most of us would wish).

BTW, the real point of the +/- 3 dB spec isn't, I think, to fudge power handling figures, because that spec, by itself, says nothing about how much power you can put into a speaker, only how much output you get for a specified input. The real point is to fudge *frequency response* figures. If mfrs had to report a cab's response at +/- 0 dB, you can bet that very few, if any, boxes would be able to boast, say, 40 Hz to 18 kHz response.

13. VicDamone

Jun 25, 2000
What your looking at are the manufacturers spec's achived at the manufacturers facility using thier equipment. I'm sure each manufacturer does thier best to achive an accuret messurment of thier product. Unfortunatly very few tell you what their system is flat to. While this frequency information is nice to have it is still not completely standardized.

If all speaker systems were taken to central calibrated location for meassurment then the frequency response meassurments would be equal but still no where near as important as what your own ears are telling you about the sound/tone you are trying to achive.

That said, how much volume are you willing to give up when you play the lowest notes on your instrument? How much amplifier power do you have? Do you like the tone? These are questions that will be answered when you actualy audition the equipment with the gear you'll be using it with.