Author Topic: Frequency Response  (Read 2976 times)

Offline rollo

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Frequency Response
« on: September 26, 2017, 10:53:06 AM »
   What frequency response is enough ?? How low to get the bass right and yes how high to get the air and extension. Except for organ music which goes to 16HZ the piano goes to 28HZ.
  When I see speakers that only go down to 45HZ and cost thousands I get a rash.



charles
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Offline dBe

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Re: Frequency Response
« Reply #1 on: September 28, 2017, 10:07:44 AM »
   What frequency response is enough ?? How low to get the bass right and yes how high to get the air and extension. Except for organ music which goes to 16HZ the piano goes to 28HZ.
  When I see speakers that only go down to 45HZ and cost thousands I get a rash.



charles
I'm going to open up a big old can of worms here, I know.  Oh, well.

Music is predominately a midrange event.  Remember the BBC LS3/5A? Lots of energy in the upper bass and a seriously rolled off high end.  Sounded great at low levels even with limited dynamic range.

I read many years ago about the Rule of 400,000 (Martin Collums?).  His premise was for reproduction to sound balanced the LF and HF -3dB points should produce a product of 400,000.

20 X 20,000  =  400,000

40 X 10,000  =  400,000.  And so on.

The HF roll off should be 3dB/octave.

One of the glaring errors in DIY speaker building is a small speaker with limited LF that is flat to 20K.  They make my teeth hurt.  Building a tweeter with terrific HF extension is much easier and cheaper than a woofer capable of 20Hz.  Too many would be speaker designers are very proud of their little speaker that is "flat out to 20K".  I always ask them : "Why?"

It is hard to even get the critical midrange correct.  Notice I didn't say accurate.


Offline AJ Soundfield

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Re: Frequency Response
« Reply #2 on: September 28, 2017, 10:14:04 AM »
Competent amplifiers, electronics etc have "frequency response".
Loudspeakers have frequency responses.
A critical difference
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Offline dBe

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Re: Frequency Response
« Reply #3 on: September 28, 2017, 08:14:06 PM »
Competent amplifiers, electronics etc have "frequency response".
Loudspeakers have frequency responses.
A critical difference
Indeed.

Remember back in the day when JohnK and I would butt heads over speaker design?  JohnK, the "I have simulated so it must be magnificent sounding with all of the conjugate networks flattening responses in a 4th order crossover alignment" and me  "choose drivers with exemplary performance in their passband and minimal slope" guy?

You are so right about the summation of drivers with great frequency response, appropriate power and impulse response.  All of that matters.  I sometimes wonder if would be speaker designers ever leave the computer or the sweet spot.

Things that I have always admired about your speakers is that they sound "right".  Right is hard to describe for me.  Soundfield speakers are always musical all over the room.  Some of your driver choices have been not what I would choose, but that just tells me all that I still don't grok about speaker design. 

I hope that you will take some time to expound on what Charles asked. 

I know a few things that are true for me, in my unique room with my unique biases.  I am sick and tired of detailed presentations that miss the life in the music.  Chest pounding bass is worthless unless it is tuneful, expressive and well integrated into the lower mids.  I find this one of THE challenges in speaker design.  Hard to get in concert without being overblown or, conversely, too taught and fleshless.  Mid driver choices are getting easier with drivers with the sensitivity, Xmax and passband performance 2-3 octaves beyond crossover points to be manageable without strangling networks...

Things are so much better with all of the driver and component choices today.  Even so I have gone to the simplicity of the high sensitivity, coherent, single cone driver with swarm LF augmentation in my old age.  Part of this is because it is easy.  I have only a modicum of energy these days that demands most of it to service my business.  The other reason is the emotive, directly connected quality of a great single cone driver.  They speak to me...

I digressed mightily because we don't communicate often enoug these days.  Alas...

So.  AJ what do you have to say about frequency response and musicality?

 :thumb:

Offline AJ Soundfield

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Re: Frequency Response
« Reply #4 on: September 29, 2017, 07:30:53 AM »
On the bottom end, Charles is referring to extension, i.e. how deep. A simple on axis "frequency response" will give one a pretty good idea there (no, not a "spec", but an actual measurement). If the speaker extends down to 20s, even -6db or so free space/anechoic, it should have pretty deep bass foundation in most rooms. Not talking about SQ per se, just "depth". It will be deep.
OTOH, a simple on axis frequency FR on the top end won't tell much anything, unless there is a large peak or dip. The key to whether it will sound "airy" (other than the room/placement), is the off axis. "Air" comes from having a lot of HF sound power, i.e. very wide dispersion at HF, specifically above 10k or so for we/you old farts. :D
That's part of the frequency response part.
"Musicality"? That can mean anything to anyone. What it most likely means, is "I" like it, it sounds "good".
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Offline dBe

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Re: Frequency Response
« Reply #5 on: September 29, 2017, 09:21:08 AM »
One comment about low frequencies.  Extension without inner detail is just noise to me.  There are quite a few drivers that will go to or below 20 Hz.  The number of drivers and alignments that do so while defining the sublties that reveal string, pitch, and recorded space modal characteristics is much smaller.  Some drivers are great at reproducing LFE, but nuttin' but mud in musical applications.


Offline rollo

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Re: Frequency Response
« Reply #6 on: September 29, 2017, 11:08:24 AM »
   There is no question I would rather own a speaker that is linear within .2db from say 30 HZ to 20KHZ than a speaker that goes down to 20HZ @-6db.
   Boomy, bloated, noise is not what I desire. Accurate bass with proper tonality and harmonics. If a piano goes to 28HZ then I would like the -3db point to be 25HZ. For occasional organ music a -3db point at 20HZ is good enough for me.
   I agree most of the notes heard are in the midrange however we cannot just eliminate low frequencies as it is the foundation. It is expensive and difficult to achieve 20HZ to 20KHZ in a speaker for reasonable money. If I just listened to chamber music or acoustic guitar wonderful. With rock or organ music ya need the bass.
   I prefer a single driver or two way design. Single driver must to augmented by a sub or subs. Two ways as well just a tad easier to accomplish.
   I would say that a speaker that is flat from 28HZ to 18K would suffice.


charles
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Offline P.I.

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Re: Frequency Response
« Reply #7 on: September 29, 2017, 11:26:28 AM »
   There is no question I would rather own a speaker that is linear within .2db from say 30 HZ to 20KHZ than a speaker that goes down to 20HZ @-6db.
   Boomy, bloated, noise is not what I desire. Accurate bass with proper tonality and harmonics. If a piano goes to 28HZ then I would like the -3db point to be 25HZ. For occasional organ music a -3db point at 20HZ is good enough for me.
   I agree most of the notes heard are in the midrange however we cannot just eliminate low frequencies as it is the foundation. It is expensive and difficult to achieve 20HZ to 20KHZ in a speaker for reasonable money. If I just listened to chamber music or acoustic guitar wonderful. With rock or organ music ya need the bass.
   I prefer a single driver or two way design. Single driver must to augmented by a sub or subs. Two ways as well just a tad easier to accomplish.
   I would say that a speaker that is flat from 28HZ to 18K would suffice.


charles
One thing that we have to remember is that "most" rooms have a dimension determined gain response that needs to be taken into consideration.  This is one place where dipoles excel.  Their room gain response is way easier to control vs the linear pressurization response of a monopole.

Yeah, I like deep, tuneful, articulate bass as much if not more than most people.  I admit it.  I'm a bass junkie...
"A man with an experience is never at the mercy of a man with an argument." - Hilmar von Campe

Offline HAL

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Re: Frequency Response
« Reply #8 on: September 29, 2017, 01:27:28 PM »
Nothing wrong with that. 

Real bass and drums have tremendous output power to try and reproduce correctly.   

Offline Folsom

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Re: Frequency Response
« Reply #9 on: September 29, 2017, 01:41:12 PM »
In room responses are not that impressive when measured. Usually getting them close means everything sounds wrong. I think trying to eliminate nodes and any dominate frequency ranges is the best goal. If you have dominate bass you can't concentrate on anything but it, if you have lots of nodes the music sounds empty in different ranges. The music may not be entirely flat, but it'll sound right.

Offline rollo

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Re: Frequency Response
« Reply #10 on: September 30, 2017, 06:32:55 AM »
  So then to actually get 20 HZ bass in a room it appears the room is as important as the speaker. Do we require a 40ft. long room ? Does the Cardas Golden Ratio take care of bass nodes to achieve low bass ?
  The room dimension will either enforce or defeat low bass output. So in order to really get true 20hz extension the room must be larger.
  Question then. How large ???


charles
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Offline Folsom

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Re: Frequency Response
« Reply #11 on: September 30, 2017, 11:19:38 AM »
Take a look at the swam subwoofer technique. Instead of using bass traps and experimenting with positioning for a long time, Duke figured how to eliminate the problem by working around the room's issues. Instead of trying to equalize the pattern from one or two radiating sources, he just made more sources so the summed signal makes the difference. Other people use differently aligned phases at the rear of the room, subwoofers, to help. Neither of which require a 40ft room.

You're right that the waves are very long, but you don't have to "hear" a complete wave to get the gist. The problem is when say 40hz sounds good but 20hz is -16db at the listening position, but if you move the sub to get 20hz up, then maybe 40hz will be down. Questions come up like, ok am I reinforcing other frequencies or is something sucking one down? You can treat the whole room to stop reinforcement, with lots of bass traps, for example, then turn the volume up.

To me it seems like an annoying game if your ultimate goal is simply to be flat down to 20hz. That's why using multiple subs is an easier way to get your objective.

But it's not just bass. For example, windows that are light glass can make direct reflections from the tweeter range appear more forward/irritating. The midrange/bass really does best having a lot of distance from anything, or being reinforced with being against a wall and tuned for it - you can fake the distance with treatment.