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I see most of the subs designed here are tuned below 20hz. Whats the purpose for tuning below audible frequencies?
 

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I see most of the subs designed here are tuned below 20hz. Whats the purpose for tuning below audible frequencies?
Movies have bass down to 10 Hz at times. You feel it more than hear it. Also gets any phase delay issues below any possible audiable range.
 

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There's a lot of movies that have content way below 10Hz, even. And like Bob said, you get most of the tuning issues out of the obvious ranges. It does put a bit of strain on the driver and amp, so LLT configurations (Large Low Tuned) need some design decisions to accomodate that. Read up on the 'LLT explained' thread for a thorough explanation of the concept.
 

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Also with todays modern long throw drivers you won't use the full displacement that the driver is capable of unless you tune low. If you tune a driver with 27mm xmax to 25 or 30hz it will take thousands of watts to use all of that excursion that the driver has.
 

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In a word, tuning low shifts port anomalies to the inaudible area.
 

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I am very much not a fan of tuning as low as possible, but I think I'm in the minority on that.

It all comes down to the specific constraints for the particular application and understanding the compromises that must be made.
 

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It all comes down to the specific constraints for the particular application and understanding the compromises that must be made.
Exactly. You don't just tune any old driver with a random amp powering it, as low as you can. If you want to tune low you design the system to reach that goal or you optimise for what you have to work with.
 

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Ricci said:
Also with todays modern long throw drivers you won't use the full displacement that the driver is capable of unless you tune low. If you tune a driver with 27mm xmax to 25 or 30hz it will take thousands of watts to use all of that excursion that the driver has.
Correct, excursion ends up going to waste, as one isn't likely to need 130db peaks. Shift some displacement down low to gain more balanced capability.
 

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Increasing excursion guarantees an increase in distortion.
Having extra excursion available is not a bad thing either.

I might argue that there is nothing inherent to maximizing the excursion of a driver that results in the most optimal sound quality.
 

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Increasing excursion guarantees an increase in distortion.
Having extra excursion available is not a bad thing either.

I might argue that there is nothing inherent to maximizing the excursion of a driver that results in the most optimal sound quality.
I agree totally.

Like I said before it depends on what your goals are and what you have to work with. You will need a certain amount of displacement from your drivers to reach your goals regardless of how much xmax is left over or not. You seem to be assuming that the system will be driven to the ragged edge a lot. This is not the case. I just prefer to have both the amp and driver limit at about the same time, so that it is very obvious when the limit has been reached and you get the maximum use out of the driver and amp involved, in both extension and peak output across a broad bass bandwidth. If things are being pushed more than 70% capacity regularly it's time to get more headroom anyway. :T

If solid response down to 25 or 30hz is all that is required I would stick with good pro audio drivers and not even mess with inefficient long excursion designs because it isn't needed for that.
 

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You seem to be assuming that the system will be driven to the ragged edge a lot.
Isn't that what you're doing when making sure the excursion and amp limit at the same time? ;) :p

Just some thoughts to throw out there....
-Flat after room gain sounds unnatural. The ideal target is probably closer to ignoring room gain, but not ignoring boundary gain.

-The shape of the corner frequency affects the perceived quality of the system.

-Tuning below the Fs of the driver can underdamp the system.

-Big cabinets are generally good for a million reasons, but can result in boundary cancellation issues at higher frequencies due to limitations on speaker placement (the box has gotta go somewhere in the room).

I don't think any of those improve the sound quality too much, but tend to be common side effects of tuning super low...

To me, the lowness of the tuning is relative to the driver being used. You could be tuning "super low" at 40Hz if the driver isn't suited for it. The actual bandwidth is kind irrelevant as the same acoustic principals apply to all frequencies.

We're probably on the same page...I just wanted to communicate that it's more than just the large signal behavior.
 

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Isn't that what you're doing when making sure the excursion and amp limit at the same time? ;) :p
Why? Are you assuming the system should be running up to its limits?
Just some thoughts to throw out there....
-Flat after room gain sounds unnatural. The ideal target is probably closer to ignoring room gain, but not ignoring boundary gain.

-The shape of the corner frequency affects the perceived quality of the system.

-Tuning below the Fs of the driver can underdamp the system.

-Big cabinets are generally good for a million reasons, but can result in boundary cancellation issues at higher frequencies due to limitations on speaker placement (the box has gotta go somewhere in the room).

I don't think any of those improve the sound quality too much, but tend to be common side effects of tuning super low...
To me these are quite negligible side effects compared to the huge benefits you obtain from a well designed (big) enclosure. Also a sub is not used to reproduce higher than necessary frequencies...
 

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Isn't that what you're doing when making sure the excursion and amp limit at the same time? ;) :p

No. I thought I addressed the reasons for this in the above post. :dontknow: the majority of the time you'll be at 25% or less. No one should be running things at the point of being in amplifier clipping or heavy distortion that's just silly. But in the event that you do want to crank things or there is a very large peak in the signal you can assume that even if your driver does not meet it's linear xmax spec (where THD should be less than 10%) It should atleast safely operate there without danger of being damaged. If your amp runs into clipping right at about this level it ensures that your driver does not get overdriven, things start to sound noticeably bad (hey turn it down) and it allows you to get maximum displacement from the driver and power from the amplifier so that neither is limiting each other prematurely. This gives you maximum bandwidth uniformity in the bass for your set-up.

Just some thoughts to throw out there....
-Flat after room gain sounds unnatural. The ideal target is probably closer to ignoring room gain, but not ignoring boundary gain.

I would argue that to most people real true bass extension sounds unnatural anyway because, they've never heard it. I'm not quite sure what you mean exactly in your comment though. Do you mean a flat in room response or a flat response prior to being subjected to room gain which will boost up the low end (IE house curve)? Can you give a further explanation?

-The shape of the corner frequency affects the perceived quality of the system.

Can you clarify this some more? I believe that I'm thinking of something else than what you mean.

-Tuning below the Fs of the driver can underdamp the system.

Sure. I look at it like this though. If the resonant portion of this system is taking the vast majority of the workload below the drivers FS and loading the driver so that it is not working very much at that point this should mitigate this effect to an extent, should it not?

-Big cabinets are generally good for a million reasons, but can result in boundary cancellation issues at higher frequencies due to limitations on speaker placement (the box has gotta go somewhere in the room).

This could come into play but it's not the cabinets fault, it would be up to you to make sure that this isn't an issue in your placement.


I don't think any of those improve the sound quality too much, but tend to be common side effects of tuning super low...

To me, the lowness of the tuning is relative to the driver being used. You could be tuning "super low" at 40Hz if the driver isn't suited for it. The actual bandwidth is kind irrelevant as the same acoustic principals apply to all frequencies.

I agree.

We're probably on the same page...I just wanted to communicate that it's more than just the large signal behavior.
I don't think that anyone is saying that tuning really low is a free lunch. There are some issues and tradeoffs made as with any design really. It can be done right though and it can produce a good sounding system.
 
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