2nd ported box build

[Buck 5,000+ posts]

Im calculating 2.28ft3@41.35Hz. Keep in mind that Fs is not directly related to cutoff or tuning frequencies. The reason being, when loaded, this Fs changes based on the acoustical restrictions and abilities of the box at that point. You can make a speaker with an Fs of 60Hz, play a 30Hz tune in the right box with authority. But, now the question is, what tuning do YOU want to use? Most on here will say, "41Hz is too high" because that is what they are used to, and depending on their preferences, that is correct. but this is what the sub likes the best is what I am showing you. This is the dual 4 ohm driver with the Fs of 31Hz.

But say you want to tune it to the low 30s, then I come up with 3.37ft3@33Hz, as an average of 30-35Hz for sake of argument. Port characteristics change with each change in tuning as well, but most do not account for that so I will leave that part alone for now.

//content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

Calculated based on what response? (Out of curiosity)

 

[Moble Enclosurs 10+ year member]

I'm glad to know that I wasn't that far off on the size of box but wouldn't have thought about tuning in the low 40's. It difently should give me the SPL needed to fill the bus. Thank you for taking the time to crunch the numbers.
One question, how low below the tuned frequincie do you think we can go before audible distortion will be a factor? Most music will be dance/ hip hop with some rap thrown in I'm sure. Just don't want to tune to high and have the speaker drop out in the lower range.

well, distortion can be from power or mechanical. So, as long as you do not overpower it, it will be fine. But in the sense of mechanical, this is also in a sense, partially power controlled, but what you mean is "before mechanical limitations are met" I believe. That would have to be calculated on how many volts of power you can run through the subs before limitations are figured. It could hold all through the spectrum, it could drop right below 40hz.....depends on the design.

So, I cannot answer that without doing a design. But in a conventional be, for instance, it could start to reach xmax around the mid 30s or low 30s. Again...depends. Tuning should not be used to control group delay, phase, or xmax nor distortion. Tuning should be used only for proper response range operation. The other factors should be controlled by physical means and some electrical means...not by tuning frequencies.

 

[Moble Enclosurs 10+ year member]

Calculated based on what response? (Out of curiosity)

well wouldn't you like to know...lol j/k. No seriously though, the specs ARE the response in this case. Because they were calculated on physical and acoustical limitations to control the subwoofer at it best operating capabilities. It has nothing to do with personal preference in the specs you pointed out. It is a way to configure proper response from the sub and box only, and is only based on a bass reflex idea as of now.

Each design will have its own specs and that is even true for compression, though a lot of people believe that is solely based on VAS figures. Though this is one factor that is parallel in calculations, it is not the only determining one.

Map the specs out on a program and see what it shows. Idk what it would come up with yet because not everything has been calculated for as of this time. So, even those recommendations that I mention can be changes for personal preference.

The The thing about my recommendations that people need to understand is that these are for response calculations only as of now. Tweaks can be made to fit your lifestyle of musical choice any way you choose. Nothing says you cannot tune these to say, 26Hz and not be fine with that. But for what I figure, it is the best starting point of optimum operation of the subs of choice in whatever box I calculate for. Too many variables exist that make these recommendations solid for everyone. But I can guarantee that efficiency is going to be increased, and musicality will be amount its best in any of my figures, regardless of how low you personally want to go.

When I design, I use these calculation I have come up with as either a definite, depending on how it matches your taste and limits, or I change it a bit to better the transience of the response for a more natural output. There are likely always going to be minor changes in any design to customize it to your liking because, as we all know very well at this point, everyone's will be slightly different as a majority.

 

[shake this 10+ year member]

That diffently clears up a few things for me. Once I get them built, I'll post back up and let everyone know what I thought of the overall performance.

 

[Buck 5,000+ posts]

well wouldn't you like to know...lol j/k. No seriously though, the specs ARE the response in this case. Because they were calculated on physical and acoustical limitations to control the subwoofer at it best operating capabilities. It has nothing to do with personal preference in the specs you pointed out. It is a way to configure proper response from the sub and box only, and is only based on a bass reflex idea as of now. Each design will have its own specs and that is even true for compression, though a lot of people believe that is solely based on VAS figures. Though this is one factor that is parallel in calculations, it is not the only determining one.

Map the specs out on a program and see what it shows. Idk what it would come up with yet because not everything has been calculated for as of this time. So, even those recommendations that I mention can be changes for personal preference.

The The thing about my recommendations that people need to understand is that these are for response calculations only as of now. Tweaks can be made to fit your lifestyle of musical choice any way you choose. Nothing says you cannot tune these to say, 26Hz and not be fine with that. But for what I figure, it is the best starting point of optimum operation of the subs of choice in whatever box I calculate for. Too many variables exist that make these recommendations solid for everyone. But I can guarantee that efficiency is going to be increased, and musicality will be amount its best in any of my figures, regardless of how low you personally want to go.

When I design, I use these calculation I have come up with as either a definite, depending on how it matches your taste and limits, or I change it a bit to better the transience of the response for a more natural output. There are likely always going to be minor changes in any design to customize it to your liking because, as we all know very well at this point, everyone's will be slightly different as a majority.

I also take most ts parameters with a grain of salt. They seem to vary greatly from what companies post.

 

[CAT MAN 5,000+ posts]

I also take most ts parameters with a grain of salt. They seem to vary greatly from what companies post.

thats because of the use of the sub. factory fresh subs are within a few decimals. once they get broken in its another story. You yourself should know to get the latest test for them if you are able to test. if not most companies would be glad to assist in post break in ts specs.

 

[duanebro 10+ year member]

I have not modeled this, I just wanted to say that the small box alpine recommended is intended for a smaller vehicle. So the op is right, a bigger box is better in this case, do to less cabin gain in a bus. I know that larger boxes have been suggested, I thought someone might wonder why the designs suggested are so different than what alpine recommends.

 

[Buck 5,000+ posts]

Alpines recommendations are far from optimal for most boxes that I've done. I don't do theirs from specs.

 

[Argent Audio 10+ year member]

Most important thing to keep in mind is that once you put any box into a listening enviornment about 75% of your calculations go out the window //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

From what I recal the new Type R's do just fine in a smaller box due to the fact that Alpine beafed up the BL product on them recently.

Andrew

 

[pro-rabbit 5,000+ posts]

Are we really going back in this debate of T/S and how accurate/inaccurate they are?

On topic, depending on what the user wants, the Type R is a very "forgiving" driver. All though the enclosure makes a large difference in the over all sound/response, that sub seems to work decently well in a wide range of enclosures. Well.... It works well enough to suffice for most.

 

[Argent Audio 10+ year member]

thats because of the use of the sub. factory fresh subs are within a few decimals. once they get broken in its another story. You yourself should know to get the latest test for them if you are able to test. if not most companies would be glad to assist in post break in ts specs.

Some companies state how much play time their woofers have had before the measurements were taken, some do not. I know most major companies give theirs around 2 hours of play time at about 80% xmax values before taking their measurements. How long a sub is fully broken in depends on spiders etc. The most noticable thing you will see after break in time if you took a second set of measurements is a drop in the Fs value.

Andrew

 

[pro-rabbit 5,000+ posts]

Some companies state how much play time their woofers have had before the measurements were taken, some do not. I know most major companies give theirs around 2 hours of play time at about 80% xmax values before taking their measurements. How long a sub is fully broken in depends on spiders etc. The most noticable thing you will see after break in time if you took a second set of measurements is a drop in the Fs value.
Andrew

I can tell you that most companies do not even test their own drivers. They allow the build house to do various testing then they just regurgitate their findings. In reality a vast majority of companies alter their drivers over the course of time and the specs listed are rarely adjusted to the new product.

This is still basing a conversation on how valid T/S really are.