Does driver selection matter?

[MichaelH]

It seems that today subwoofers achieve best response by equalizing their frequency response.
Expensive subwoofers even include a microphone with an automatic calibration that sweeps the frequency range and adjusts levels such as to get the best in-room response.

Now, if this is true, why does it matter which driver I use?
Of course not all drivers have the capability to reach the same SPL levels, but assuming different drivers have a capability to reach a max of 103 db then the lower frequency range can be equalized? Or cant it? I am assuming an inteligent (DSP) equalizing amplifier can also correct distortion up to certain harmonics.

What sonic differences do we get from a driver beyond frequency response?

 

[lovinthehd]

It's about the capability of the particular driver that determines just how much power/eq you can apply, tho. So, it matters a lot. There's a diy subforum here, too fwiw.

 

[TLS Guy]

It seems that today subwoofers achieve best response by equalizing their frequency response.
Expensive subwoofers even include a microphone with an automatic calibration that sweeps the frequency range and adjusts levels such as to get the best in-room response.

Now, if this is true, why does it matter which driver I use?
Of course not all drivers have the capability to reach the same SPL levels, but assuming different drivers have a capability to reach a max of 103 db then the lower frequency range can be equalized? Or cant it? I am assuming an inteligent (DSP) equalizing amplifier can also correct distortion up to certain harmonics.

What sonic differences do we get from a driver beyond frequency response?

All drivers have different T/S parameters. These parameters determine the box dimensions, and how the driver should be loaded. Diver and box are integral to a successful design. You have to model the driver the program will guide you to the optimum box. You can not correct errors with Eq, in fact that is a really good way to send a driver to the graveyard. Equalizers can NEVER make a bad speaker and or a bad design a good one.

 

[William Lemmerhirt]

The reason modern designer are able to get all that performance with EQ and dsp is 100% because of the driver. Amp and box tech has been mature for a long time. DSP, while better and more convenient than ever, isn’t really new either.
It’s also not as simple as being able to eq frequencies into a driver that it can’t produce. A driver with a high FS, like 40hz isn’t gonna be a candidate for 20hz output. No matter it’s db capabilities. Then there’s damping characteristics, Xmax, power handling etc. and no, you can’t simply dsp distortion out. If by that you mean using a compression scheme to limit output, then yes, to a point you can but what’s the point of that? I recently saw compression sweeps of an sb1000. From 40hz and below, output basically remained the same as volume increased past a certain point. To me that’s useless.
So, really there’s a lot beyond FR of a driver. Almost, forgot. The enclosure has to be carefully selected as well. Basically a subwoofer is a system in and of itself.

 

[MichaelH]

Those are all good answers, but I was trying to understand better the acoustic impact.
Assuming box was properly designed, then would two different drivers that were equalized, sound differently?
In other words - I am not trying to put two different drivers in the same box. Rather two drivers with different parameters, each in a different box and both boxes designed for same Qts. Now apply DSP and equalization to both - will they sound any different?

 

[William Lemmerhirt]

If I follow...
It depends. While you might get two different subs to “sound” the same, they’ll likely have very different FR curves, and definitely different output capabilities. Short version, is your question is too simple.
T/S parameters will decide EVERYTHING. So again, no. You can’t just pick a driver and fix it with EQ.

 

[highfigh]

Those are all good answers, but I was trying to understand better the acoustic impact.
Assuming box was properly designed, then would two different drivers that were equalized, sound differently?
In other words - I am not trying to put two different drivers in the same box. Rather two drivers with different parameters, each in a different box and both boxes designed for same Qts. Now apply DSP and equalization to both - will they sound any different?

Making assumptions rarely works- testing is always needed because we can't look at the specs and see all of the results of reflections, diffraction, absorption, crossover components/circuits, etc.

The physical characteristics of the cone material & shape, suspension and frame all affect the final sound, even in free air.

 

[highfigh]

Trying to eliminate problems with an equalizer is similar to the saying "Never try to teach a pig to sing- it sounds bad and it annoys the pig".

 

[MichaelH]

Making assumptions rarely works- testing is always needed because we can't look at the specs and see all of the results of reflections, diffraction, absorption, crossover components/circuits, etc.

The physical characteristics of the cone material & shape, suspension and frame all affect the final sound, even in free air.

Well, this is exactly my question then: what are the characteristics of this different sound? Can they be measured?
Another way to ask this question would be: would two different speakers sound exactly the same if each one was optimized in their custom box, and then (through DSP) made to have the exact same frequency response.

If they would not sound the same, can we quantify the differences, can we measure them, can we objectively define the sonic variance?

 

[MichaelH]

If I follow...
It depends. While you might get two different subs to “sound” the same, they’ll likely have very different FR curves, and definitely different output capabilities. Short version, is your question is too simple.
T/S parameters will decide EVERYTHING. So again, no. You can’t just pick a driver and fix it with EQ.

So the question is a bit different. It is not if I can "fix" it. The question is, assuming I can get both their frequency responses to match exactly - would they sound the same?

 

[MichaelH]

I believe I found the answer to my question.
In short - two speakers made to have the exact same frequency response will sound differently.
Can it be measured? some parameters can - albeit complicated, and some can't.
One thing is sure- we are not getting all the data from the driver manufacturers.

The excellent in-depth article I found that describes all the nuances can be found here:
https://www.soundonsound.com/sound-advice/understanding-speaker-specifications?page=1
Page 2 is where it gets really interesting with the different distortions. There is also a small section at the end explaining the impact on subwoofers.

... which brings me to my conclusion that designing the ultimate subwoofer is impractical because it will require trial and error with multiple drivers and different box designs.

 

[William Lemmerhirt]

So the question is a bit different. It is not if I can "fix" it. The question is, assuming I can get both their frequency responses to match exactly - would they sound the same?

I’m gonna say no. But it kinda depends too...
There’s more to it than FR. Driver control, damping, spl capabilities, content etc.
So, what makes each theoretical driver different from each other? That will tell you what you’d need to make the FR the same. And if you did get the FR the same, they might sound the same, but depending on the TS parameters one might sound bloaty and gross, while the other could be nice n tight. Depends on the electrical attributes of the driver, and amp.(assuming the cab is optimized)
So I guess in short, no. FR alone won’t make them sound the same. While two different drivers in two different boxes COULD possibly SOUND the same, it would be by accident if you only based it on FR.

 

[TLS Guy]

So the question is a bit different. It is not if I can "fix" it. The question is, assuming I can get both their frequency responses to match exactly - would they sound the same?

You will not be able to get their frequency responses to be the same. For one thing if a driver has an Fs of 32 Hz and the other 18 Hz, then the 32 Hz Fs driver will never play to 20 Hz no matter how much Eq you use, the 18 Hz driver might well. It is totally impossible to Eq a driver to sound like another, this is for lots of reasons, Fs, maximum cone excursion, points of cone breakup leading to resonance and issues of stored energy. There is a lot more than just the same frequency response to getting two speakers to sound the same. As I have said here many times, it is perfectly possible to make a speaker with a perfect frequency response, that would be totally unusable as a speaker and sound like nothing on Earth.

You are asking a question that you could only ask if you have not the first idea of speaker technology.

Speaker design has to follow this process.

1). A clear and precise statement of your aim, purpose and usage of your design.

2). Very careful driver selection

3). Accurate box design and modelling, which includes the optimal box for that driver. This includes whether, sealed, ported, or ABR is appropriate for the driver you select. Consideration can also be given to TL and horn and occasionally infinite baffle.

4). Careful cabinet plans to minimize unwanted panel resonance.

5). Careful testing and listening.

You do it in THAT ORDER

One thing you never do is take a box and try and select a driver. I can not stress enough that does not work. There is only one way to do this, and your method is well wide of the mark for producing a sub that would in any way be an acceptable performer.

That is just the way it is. Wishing another way, is just that, wishful thinking.

Every engineered product and device, has its own discipline of design and engineering parameters. I have just given you a brief outline of the discipline of box design for speakers. There is no such thing speaker selection for a box. I think that your approach is commonly known as ass backwards!

 

[MichaelH]

You will not be able to get their frequency responses to be the same. For one thing if a driver has an Fs of 32 Hz and the other 18 Hz, then the 32 Hz Fs driver will never play to 20 Hz no matter how much Eq you use, the 18 Hz driver might well. It is totally impossible to Eq a driver to sound like another, this is for lots of reasons, Fs, maximum cone excursion, points of cone breakup leading to resonance and issues of stored energy. There is a lot more than just the same frequency response to getting two speakers to sound the same. As I have said here many times, it is perfectly possible to make a speaker with a perfect frequency response, that would be totally unusable as a speaker and sound like nothing on Earth.

You are asking a question that you could only ask if you have not the first idea of speaker technology.

Speaker design has to follow this process.

1). A clear and precise statement of your aim, purpose and usage of your design.

2). Very careful driver selection

3). Accurate box design and modelling, which includes the optimal box for that driver. This includes whether, sealed, ported, or ABR is appropriate for the driver you select. Consideration can also be given to TL and horn and occasionally infinite baffle.

4). Careful cabinet plans to minimize unwanted panel resonance.

5). Careful testing and listening.

You do it in THAT ORDER

One thing you never do is take a box and try and select a driver. I can not stress enough that does not work. There is only one way to do this, and your method is well wide of the mark for producing a sub that would in any way be an acceptable performer.

That is just the way it is. Wishing another way, is just that, wishful thinking.

Every engineered product and device, has its own discipline of design and engineering parameters. I have just given you a brief outline of the discipline of box design for speakers. There is no such thing speaker selection for a box. I think that your approach is commonly known as ass backwards!

Woooah - I do not know how you got to the conclusions you got.
1. I never said take a box and fit a speaker to it
2. The example you gave does not apply.
3. I did not ask how to build a subwoofer

In short, I was trying to understand "IF" you would be able to get two different drivers to have the exact same FR, assuming each in optimized box of its own and DSP methods to equalize and eliminate harmonic distortions, "THEN"
a) would they sound the same?
b) if not, then how would you quantify the differences, and more importantly, how will they manifest themselves sonically.

I pretty much found the answer I was looking for in the article I quoted. "Only pretty much" because no one addressed the sonic perspective.

 

[lovinthehd]

What is the practical application of your question, tho? What are you trying to do?

 

[TLS Guy]

Woooah - I do not know how you got to the conclusions you got.
1. I never said take a box and fit a speaker to it
2. The example you gave does not apply.
3. I did not ask how to build a subwoofer

In short, I was trying to understand "IF" you would be able to get two different drivers to have the exact same FR, assuming each in optimized box of its own and DSP methods to equalize and eliminate harmonic distortions, "THEN"
a) would they sound the same?
b) if not, then how would you quantify the differences, and more importantly, how will they manifest themselves sonically.

I pretty much found the answer I was looking for in the article I quoted. "Only pretty much" because no one addressed the sonic perspective.

Sorry I did not understand you question correctly. I thought you were asking that you could put any driver in any given box and Eq it.

Now I understand the answer is still no. Only sealed boxes can be equalized. Ported designs just decouple from the box if you apply Eq. You can not drive a speaker below fs however you equalize it. Also you you can only equalize any driver within its excursion limits.

 

[MichaelH]

What is the practical application of your question, tho? What are you trying to do?

I remember reading about a subwoofer that had a feedback system such that it would correct itself such that the waveform of the sound produced would equal the waveform at its input. I can't remember which brand it was but the promise was the purest sound. It got me thinking. If it has such an accurate capability, why does it matter which driver is being used? Granted, not every driver, but I am sure it could do the same with many drivers.

And then it became a theoretical exercise. Woofers are mechanical and mechanical devices are not perfectly linear. The air pressure in the box will never be equal to the air pressure outside the box. The subwoofer will not have the same harmonic distortions at 80 SPL and at 105 SPL. The perfect subwoofer will not sound the same in different rooms - different sizes, shapes and damping, not to talk about architectural stability of frames, furniture and even walls. So, why make the perfect subwoofer? Instead, take a driver with characteristics that can be very well modeled, and put it in a box with an electronic circuit that will make it play perfectly anywhere. Heck add some buttons but not for crossover or phase- these will be adjusted automatically. Add buttons to change the warmth of the sound or the tightness of the bass based on personal preferences.
Purely theoretical exercise...

 

[lovinthehd]

I remember reading about a subwoofer that had a feedback system such that it would correct itself such that the waveform of the sound produced would equal the waveform at its input. I can't remember which brand it was but the promise was the purest sound. It got me thinking. If it has such an accurate capability, why does it matter which driver is being used? Granted, not every driver, but I am sure it could do the same with many drivers.

And then it became a theoretical exercise. Woofers are mechanical and mechanical devices are not perfectly linear. The air pressure in the box will never be equal to the air pressure outside the box. The subwoofer will not have the same harmonic distortions at 80 SPL and at 105 SPL. The perfect subwoofer will not sound the same in different rooms - different sizes, shapes and damping, not to talk about architectural stability of frames, furniture and even walls. So, why make the perfect subwoofer? Instead, take a driver with characteristics that can be very well modeled, and put it in a box with an electronic circuit that will make it play perfectly. Heck add some buttons but not for crossover or phase- these will be adjusted automatically. Add buttons to change the warmth of the sound or the tightness of the bass.
Purely theoretical exercise...

Sounds like a servo sub system. They haven't proved themselves to be particularly the ideal solution afaik. The science of t/s parameters and box design can easily be demonstrated thru various programs dedicated to such. All you can do really is aim for best performance desired/as goal in various parameters....

 

[highfigh]

Well, this is exactly my question then: what are the characteristics of this different sound? Can they be measured?
Another way to ask this question would be: would two different speakers sound exactly the same if each one was optimized in their custom box, and then (through DSP) made to have the exact same frequency response.

If they would not sound the same, can we quantify the differences, can we measure them, can we objectively define the sonic variance?

Lots of factors cause the sound to change and many can be measured. Ribbed cones sound different from smooth cones, curved sound different from pure cones, materials change the sound, etc. Stiffness, resonance in the cone's material, mass and other variables affect it.

On an absolute level, if 'exactly the same' is used as a way of conveying 'without any difference', that's very difficult to pull off. If it means 'having very minute variations', it's safe to use that word but when it comes to a subjective test, our hearing isn't good enough- we can decide that they sound close enough, though.