Speakers and frequency response? - AVS | Home Theater Discussions And Reviews
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post #1 of 8 Old 05-14-2003, 02:28 PM - Thread Starter
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After reading another forum comparing speakers (one being called laid back another being called warm and so on)Some on asked about frequency response.My ? is if one were to compare 2 different speakers with different drivers(metal vs soft)Different crossovers even box design,and both measured the exact same +/- 0db from top to bottom would they sound the same.?Dumb question but I had to ask..:rolleyes:
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post #2 of 8 Old 05-14-2003, 03:07 PM
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No.

1. While the speakers' measured on-axis response could be the same, the dispersion pattern/off-axis measurements, total power output, and how they interact with the room could be very different. For example, dipoles have no sound output to their sides and achieve a 4.8dB better direct to reverberant field ratio than box speakers. This is very relevant in your living room (measurements are made in anechoic chambers), where you're hearing both direct and reflected sound.

2. Distortion may be different, both in quantity and spectrum.

3. Maximum output capability may be very different. While you can achieve flat response down past 40Hz with 6" drivers, they'll bottom at reasonable volume levels which will force a higher sub-woofer cross-over frequency. One speaker may also run into power compression before the other, where double the power produces less than 3dB more SPL.

4. The phase shifts between the drivers may be different.

5. The drivers in one may ring or take longer to decay than in the other.

6. Measurement smoothing may mean that one speaker has peaks or nulls that are audible but don't show up in the graphs.
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post #3 of 8 Old 05-14-2003, 08:42 PM
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If you assume that the magnitude plot AND the phase plot both make up the frequency response, then the frequency response is very important in making up the character of the sound you would hear.

Drew mentions several key aspects for speakers that provide you more information about the speaker than just the freq response, although his points 4, 5, and 6 are not valid if you consider both magnitude and phase plots.

So, just to put another spin on things, if you listen to two speakers which have identical measured frequency responses (both phase and magnitude, although you almost never see the phase plot), measured by the same reference equipment under identical conditions, compared to each other in the exact same position of the same room, with the listener at a constant position, with both driven within their "comfort zone" power-wise with capable electronics, they would sound the same.

But Drew's points 1, 2, and 3 point out some other things that you might be looking for as a shopper, as well as impedance and sensitivity.
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post #4 of 8 Old 05-15-2003, 04:41 AM
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There is more to "sound" than "frequency".

Otherwise, a cello play a certain note would sound just like a trombone playing that same note. After all, it's the same frequency. Aretha Franklin singing a middle C would sound just like Tom Waits singing that same note. I kind of have a feeling that most people would be able to discern those two.

"SAM" is a buzz word with audio folks, and it applies to speakers, as well. It means "Specs Are Meaningless". There is very little in a spec sheet that will tell you how a speaker sounds. You can learn from its specs if it will be compatible with a given amp, and you can learn how deep the bass goes. A flatter freq resp usually points to better sound, but the exceptions to this rule are many. "SAM".

Case in point, I remember 20 some odd years ago, when I was looking for my first "real" pair of speakers, there was a British company called Rogers that had a box speaker (I can't remember its name, but it seems it had an L, R, 3, and an S - maybe an A). Even though it had atrocious "specs" (seemingly no bottom end, seemingly no top end), reviewers unaminously praised its sound. I never got to hear one, so I can't verify if their rave reviews were justified. But this wasn't just one or two reviewers. It was pretty much across the board (back in the day when there was a wide assortment of audio rags).

Many factors play into a speaker's quality: How a speaker handles transients; how it presents attack/decay; how it responds to sudden dynamic bursts; how it keeps different instruments distinct (as opposed to muddying them up); how it allows itself to disappear; etc. You'll also hear some folks speak of soundstaging and imaging.

Well, you get the picture - I'm just wasting bandwidth at this point.

Kevin
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post #5 of 8 Old 05-15-2003, 08:09 AM - Thread Starter
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""SAM" is a buzz word with audio folks, and it applies to speakers, as well. It means "Specs Are Meaningless"."

I think Floyd Toole has done blind testing where people prefered a flatter FR.(I'll try to dig that up and post it)
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post #6 of 8 Old 05-15-2003, 02:30 PM
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Kevin, I have to partially disagree with you, but add a caveat.

My response above was a theoretical response - if two speakers really do have EXACTLY the same frequency response (phase AND magnitude over the entire frequency range), they should "sound" the same. A middle C on a trombone will have a different frequency response than the same note on a cello. The primary frequency will be the same, but it's all the harmonics which make up the voice, and those will indeed be different.

Likewise, transient responses are also dictated by the transfer function of the speaker, which would be identical between two speakers having the same frequency response.

What is difficult is interpretting frequency response measurements. "Bright" speakers often have peaks in the 2-10kHz range. Laid back speakers are actually fairly flat, and might even fall off at higher frequencies. Phase response is important too, but rarely published. And then you have the issue of how the freq response graphs were determined in the first place.

Specs are somewhat meaningless. But I still stand behind my "theoretical" answer to what seemed like a theoretical question.
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post #7 of 8 Old 05-15-2003, 04:44 PM
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I would say, specs are meaningful for speaker comparisons, IF AND ONLY IF they are measured under the identical conditions/qualifications and by identical methods for all speakers in question (that is exactly what Floyd Toole did). Unlike solidstate amplifiers that usually show a ruler-flat response, no speaker has an even remotely flat frequency response. If a speaker exhibits a frequency response within +/- 3dB over its entire range, that speaker would be regarded as having a "respectably flat" response. And yet, +/- 3dB alterations are hugely audible changes. Add to this the off-axis responses mentioned above, which are even more wildly varied...

But more importantly, do not pay too much attention to the "design decisions" by various brands -- such as, metal vs. polymer vs. silk domes, ported vs. sealed cabinets, the number and configurations of drivers, etc. Some brands make a big deal out of their "unique" designs and technologies for marketing purposes. But after all, loudspeaker technologies are very well matured and nothing is truly new today. There are as many outstanding speakers as mediocre ones in each one of these design categories. Pay attention only to the "results" -- which is, of course, their sound quality.
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post #8 of 8 Old 05-15-2003, 04:58 PM
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Quote:
There is more to "sound" than "frequency".

Otherwise, a cello play a certain note would sound just like a trombone playing that same note. After all, it's the same frequency. Aretha Franklin singing a middle C would sound just like Tom Waits singing that same note. I kind of have a feeling that most people would be able to discern those two.
First sentence is correct. But the rest is nonsense. In fact, the sonority differences you described in the examples above can be fully explained by the differences in the frequency spectrum of the tone/voice. On top of that, the transient frequency spectra of the "attacks" are hugely different among these instruments.
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