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Modeling Fi subwoofers vs website reccomendation


reker13

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New to Fi subwoofers and have lots of questions.  Are the enclosure reccomendations on the website accurate?  They seem very generic for example, it reccomends a 3-4 cuft ported box tuned to 33hz for each of the:  

Alpha v2 15"
SSD 15"
SSD Neo 15"

However, modeling these subs in WinISD Pro ported on popular Quasi-Butterworth design each show big differences in the enclosure needed:  (this is what winisd reccomends)

Alpha v2 15" - 7.8 cuft tuned 28hz
SSD 15" - 1.57 cuft tuned to 37hz
SSD Neo 15" - 5.58 cuft tuned to 29hz

 
The standard SSD 15" shocked me needing such a small ported box.  Group delay looks better than a 12" alpha in that small of a box.  
 
How much should i rely on the fi website reccomendations vs a subwoofer modeling program like Winisd?  Can the SSD 15" really work in such a small ported design?  Each subwoofer line shows they need drastically different enclosure sizes ported or sealed and not just for the 15" size.
 
Any answers or insight would be much appreciated thx!
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The problem with the recommended ported alignments given by WinISD is they are geared towards getting the best flat frequency response in a open area.  When you put a sub in a vehicle the cabin gain is going to change the frequency response significantly, so WinISD's recommendations become pretty irrelevant.  Fi's box recommendations aren't so much about achieving a particular frequency response, but are more about what size box is going to be safe for the amount of power that sub is designed to handle.  

As far as group delay goes, it debated how important that attribute is.  Many think it completely inaudible at subwoofer frequencies, no matter what it is.  Other like to keep it below 30 ms.  My thoughts are its something I like to be aware of, but I don't worry about it too much, especially below 40 Hz.  

 

"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."

Builds:

U7qkMTL.jpg  LgPgE9w.jpg  Od2G3u1.jpg  xMyLoO1.jpg  9pAlXUK.jpg

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sub and enclosure combinations are trade offs. recommended enclosure specifications are just that a recommendation based on whatever they are willing to trade off. when I build enclosures for people, i've gotten down what I'm willing to trade off and what I don't care about. majority of people that listen to my boxes love them while very few don't. when I first started building boxes for people, I'd build to what they wanted and what info they gave me. I had a lot of dissatisfied people. once I learned more about how things are related I started building boxes with certain customer guidelines instead of what they were telling me. Even after you "learned" how things are related there's still trade offs in every build that are unique to the build that make you sacrifice. I don't use manufacturer's specifications as fact but more as a guideline. the main reason you want to use it as a guideline is b/c the manufacturer is not going to give a recommendation of an enclosure that's going to sound like crap but a recommendation of an enclosure that will sound decent on a large swath of music and for the recommended power they rate their speaker. 

if nothing changes, nothing changes

You don't know what you don't know, till you don't know

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Thanks for the responses.  Let's look at sealed.  Fi reccomends 1.5 - 2.5 cuft for these woofers sealed.  So here's the FSC and QTC of each driver in 2 cuft:

Alpha v2 15" - 60hz - .824 QTC
SSD 15" - 52hz - .554 QTC
SSD Neo 15" - 56hz - .749 QTC

Big difference between the Alpha and SSD series.  I only use winisd to compare drivers understanding the model is open air although you can add a per octave curve to mimic cabin gain in vehicle.  QTC is the best theoretical metric i know of to measure sound quality of a particular enclosure without actually listening.  Personally, i prefer a low QTC sound of .7 or so and lower.  Everything above that point starts to sound boomy to my ears and above 1.0 sounds like a one note wonder IMO. ? 

So, despite the 3-4 cuft for ported reccomendation from FI, would the standard SSD 15" not sound musical in a much smaller 2cuft net enclosure ported to 33hz?  My model says it would but have no experience with these drivers to say for sure?

 

 

 

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1 hour ago, reker13 said:

Thanks for the responses.  Let's look at sealed.  Fi reccomends 1.5 - 2.5 cuft for these woofers sealed.  So here's the FSC and QTC of each driver in 2 cuft:

Alpha v2 15" - 60hz - .824 QTC
SSD 15" - 52hz - .554 QTC
SSD Neo 15" - 56hz - .749 QTC

Big difference between the Alpha and SSD series.  I only use winisd to compare drivers understanding the model is open air although you can add a per octave curve to mimic cabin gain in vehicle.  QTC is the best theoretical metric i know of to measure sound quality of a particular enclosure without actually listening.  Personally, i prefer a low QTC sound of .7 or so and lower.  Everything above that point starts to sound boomy to my ears and above 1.0 sounds like a one note wonder IMO. 1f601.png 

So, despite the 3-4 cuft for ported reccomendation from FI, would the standard SSD 15" not sound musical in a much smaller 2cuft net enclosure ported to 33hz?  My model says it would but have no experience with these drivers to say for sure?

While lower QTC values may get you a flatter frequency response with less "boomyness" they are also less efficient, which is something you need to keep in mind as well, depending on how you want to use your system.  Using your example above, the SSD 15" in a 2 cu ft sealed box is going to take 2.5 times as much input power to have the same level of output at 60 Hz as the Alpha 15" in a 2 cu ft sealed box does.  More power often results in higher total harmonic distortion (THD), which is also very important to sound quality and is something you can't model in WinISD.

You asked if a SSD 15" will sound more "musical" in a 2 cu ft ported enclosure tuned to 33 Hz.  Just what is "musical" is very subjective.  If by "musical" you mean flatter response, than yes, a 2 cu ft box will give flatter response than a larger box would, assuming the same tuning frequency.  It will also be less efficient, and depending on how much power you are running, with smaller boxes you can have difficulties getting the tuning you want while having a port that is large enough to prevent port noise and be efficient, without being so long that is becomes impractical or has pipe resonance issues.  

My personal preference is for ported boxes that are on the smaller end of the spectrum, for the same reasons you listed.  There is a limit though, and its important to remember that peaks in output can usually be easily fixed with EQ, but the lower efficiency of a smaller box you are just stuck with.  My opinion is that a 2.0 cu ft ported box is going to be too small for Fi's 15" drivers.

"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."

Builds:

U7qkMTL.jpg  LgPgE9w.jpg  Od2G3u1.jpg  xMyLoO1.jpg  9pAlXUK.jpg

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