Measuring for resinate Freq:

[mrogowski 6]

Whats the res freq of my house?

Dunno, but mine is at ~32Hz. I found this out through trial and error...

[mrray13 30]

i know a box is more efficient at/near tuning, due to the port handling the majority of the output and the sub moving very little. but i really have no idea (well, i have a basic one, but i can't put it into words. it has to do with with making the sub move more and forcing the port to help, but that doesn't sound right) why a box's output almost always peaks above tuning, and in that 7-11hz range. i know vehicle is part of the equation, as well as placement. but what am i missing?

and he's trying to match box peak with car peak to maximize spl score at kick.

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

[JimJ 11]

But those equations don't make sense. They divide feet/second by viberations/second...and get a distance/second...ummmm Houston we have a problem.

You never cease to amaze me with your nonsensical babbling.

1131 Feet per sec/20 Feet = 1131/20 per sec or 56/sec or 56 hz Mathematically that portion is just fine. WTF are you talking about. I will save my issues with the rest of the article for later, but dopey you completely missed.

[mrogowski 6]

So I guess it would make sense to have a flabby box then if that is the intent...

Forgive the questions as I have never been involved with/doing SPL stuff..

[DevilDriver 28]

Well, I'm not much of an SPL guy, but from a theoretical standpoint, I think the goals being discussed here are at least semi-legitimate.

Get speaker and port to be in phase at the location of the mic when playing a signal at or near the vehicle's resonant frequency. I think it is worth noting that, not only must you consider the physical distance from your enclosure to the mic position, you must also consider the axis the port is on (side-firing, up-firing, etc) and the degree to which the port is out of phase. Careful considerations in positioning to get an in phase relationship at the mic would be a big bonus.

Tune a little bit lower than your vehicle's resonant frequency to allow for a good balance of woofer and port output (at Fb, excursion is greatly reduced, and so is thermal power handling, which isn't a good thing, so playing a little bit above that might be a good thing).

From what I have seen, SPL has always been higher on the side with the speaker; maybe using a sort of waveguide for the port to achieve some directionality and dispersion control may help boost the score even more.

Dunno, they're just thoughts.

[audio-neon 34]

i know a box is more efficient at/near tuning, due to the port handling the majority of the output and the sub moving very little. but i really have no idea (well, i have a basic one, but i can't put it into words. it has to do with with making the sub move more and forcing the port to help, but that doesn't sound right) why a box's output almost always peaks above tuning, and in that 7-11hz range. i know vehicle is part of the equation, as well as placement. but what am i missing?

and he's trying to match box peak with car peak to maximize spl score at kick.

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

Basically you are looking for the compromise max excursion and maximum port velocity. 7-11 hz under burping frequency will do this. It is sub/ box/ cabin gain dependent.

[audio-neon 34]

and my car sucks, port to mic location is just over 11 feet which makes my 1/4 wave 25.50xx hz. my half wave (which is supposed to be dead, has been where I have been burping at...) 51 hz.

[Tommythecat 0]

But those equations don't make sense. They divide feet/second by viberations/second...and get a distance/second...ummmm Houston we have a problem.

You never cease to amaze me with your nonsensical babbling.

1131 Feet per sec/20 Feet = 1131/20 per sec or 56/sec or 56 hz Mathematically that portion is just fine. WTF are you talking about. I will save my issues with the rest of the article for later, but dopey you completely missed.

He's talking about where the paper says:

"1131(fps) / 60Hz = 18.85 feet per second"

That's what doesn't make sense, if you'd taken the time to read it. Dont be such a prick.

Lord Baccus, a White Paper is a technical report on a subject put out by a company. While they often promote a certain viewpoint (which can coincide with their strategy/products/etc.), they are most likely technically correct. OzAudio has the balls to call their little document a white paper - a shame.

As far as tuning the box goes, this is very woofer dependant. Initial modeling(WinISD) of a conventional speaker - like a Mach5 MJ18 or Ascendant Avalanche 15 - shows a peak output slightly above tuning. But a driver like the FI BTL seems to have peak output, min excursion, and min impedance all at the tuning freq (which doesn't happen in the typical case).

[mrogowski 6]

As far as tuning the box goes, this is very woofer dependant. Initial modeling(WinISD) of a conventional speaker - like a Mach5 MJ18 or Ascendant Avalanche 15 - shows a peak output slightly above tuning. But a driver like the FI BTL seems to have peak output, min excursion, and min impedance all at the tuning freq (which doesn't happen in the typical case).

Just so I'm following you, what tuning are you referring to here?

[Tommythecat 0]

Im simply talking about the box tuning. What else is there to tune?

[mrogowski 6]

Ok, I understand now - thanks.

[Lord Baccus 1]

so how do i account for the 90degree sub/port ?

i measured from the subs to the point where the mic will be !

should i measure from the port to the roof & from that point on the roof to the Mic spot ?

[tejcurrent 13]

so how do i account for the 90degree sub/port ?

i measured from the subs to the point where the mic will be !

should i measure from the port to the roof & from that point on the roof to the Mic spot ?

That is excactly what I was trying to say with my first post. I was trying to figure that out from the link.

sorry

[Lord Baccus 1]

so how do i account for the 90degree sub/port ?

i measured from the subs to the point where the mic will be !

should i measure from the port to the roof & from that point on the roof to the Mic spot ?

That is excactly what I was trying to say with my first post. I was trying to figure that out from the link.

sorry

the formula assumes the subs & port are fireing forward...

maybe that accounts for the differance in the formula & the accual res of my truck.

thats an 8Hz differance

[Lord Baccus 1]

[mrray13 30]

But those equations don't make sense. They divide feet/second by viberations/second...and get a distance/second...ummmm Houston we have a problem.

You never cease to amaze me with your nonsensical babbling.

1131 Feet per sec/20 Feet = 1131/20 per sec or 56/sec or 56 hz Mathematically that portion is just fine. WTF are you talking about. I will save my issues with the rest of the article for later, but dopey you completely missed.

He's talking about where the paper says:

"1131(fps) / 60Hz = 18.85 feet per second"

That's what doesn't make sense, if you'd taken the time to read it. Dont be such a prick.

Lord Baccus, a White Paper is a technical report on a subject put out by a company. While they often promote a certain viewpoint (which can coincide with their strategy/products/etc.), they are most likely technically correct. OzAudio has the balls to call their little document a white paper - a shame.

As far as tuning the box goes, this is very woofer dependant. Initial modeling(WinISD) of a conventional speaker - like a Mach5 MJ18 or Ascendant Avalanche 15 - shows a peak output slightly above tuning. But a driver like the FI BTL seems to have peak output, min excursion, and min impedance all at the tuning freq (which doesn't happen in the typical case).

what's confusing about 1131(fps)/60hz (or cycles per second)=18.85ft? it's pretty straight forward.

i agree about the white paper part, lol

and box tuning is only woofer dependant as far as how much the woofer displaces in the box. if the mj18 and the ava18 displace the same amount of air inside the box, the box tuning won't change. now the fs of the sub might change where your peak is at, depending on how it reacts in said tuned box.

also, the program, no program that most of us will use, will ever be accurate in car, or under actual power. they are nothing more then an educated guess as to what the sub might do given the t/s parameters. a nice starting point, yes. but i for one will not depend upon a modeling program to determine overall output in any given application. jsut way too many varibles in car, under power to account for.

that said, if one wants to take an accurate frequency response reading of the car and can duplicate the exact gross displacment of the enclosure and it's location, as well as measuring/charting said enclosure for impedence rise and using the exact same power, one might indeed get really close to predicting output. but for the most part, it's all about getting close and then testing and a little bit of luck, IMO anyway.

LB..yep, you'll have to measure that exact way, up to roof, roof to mic. maybe build to split the difference? again, like mentioned before, you're looking for the compromise between port velocity and sub xmax. so, unless i'm just way off base, i'd aim for 7-11 cycles below the average of the two measurements, as a starting point only.

but i could be wrong, lol

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

[Lord Baccus 1]

did ya like the pics

the WMD logos glow from the blue lite on the amp...

pic does not do it justice

ill do the port measurement ASAP

[ANeonRider 3]

Units wise:

1131ft/s divided by 60Hz = 18.85ft

[helotaxi 46]

Getting the sub and port in phase is part of the issue. Getting the peak of the box in line with the best peak you can get out of the sub and the transfer function of the car is another part. Getting the standing wave node at the exact freq of the other parts at the mic location is the homerun. You can helo yourself with the port sub phase thing by running a phase plot and accouting for the phase difference at the peak freq with port and sub placement in the car.

[Lord Baccus 1]

what if i change where i put the meter ? and build to target say the Legal Usaci position of passangerside A piller ?

[Tommythecat 0]

what's confusing about 1131(fps)/60hz (or cycles per second)=18.85ft? it's pretty straight forward.

That's not the point as ANeonRider stated again they fudgeed up. If you read the paper it says:

Feet-per-second divided by cycles-per second = feet per second

As far as box tuning goes, yes the tuning of a box is quite independant of the driver - in and of itself. But when you do put the driver in, the impedance/excursion/spl characteristics will not be similar. I have to wonder in the BTL's case whether or not Fs, Le, or something else or some combination is affecting how those things "line up" per se.

[mrray13 30]

what's confusing about 1131(fps)/60hz (or cycles per second)=18.85ft? it's pretty straight forward.

That's not the point as ANeonRider stated again they fudgeed up. If you read the paper it says:

Feet-per-second divided by cycles-per second = feet per second

As far as box tuning goes, yes the tuning of a box is quite independant of the driver - in and of itself. But when you do put the driver in, the impedance/excursion/spl characteristics will not be similar. I have to wonder in the BTL's case whether or not Fs, Le, or something else or some combination is affecting how those things "line up" per se.

to be quite honest, i overlooked that simple wording. i was just looking at the math.

no, they won't be similiar. and i'm sure fs plays the biggest role. but again, what happens on paper, doesn't translate to what happens in car. if it did, everyone on the planet could break 160db legal. programs just can't account for the car and everything in it. not without doing some serious mapping and definitely not the programs most of us use.

as far as the btl doing what it does, in how many different tuned boxes did you plot? i'm sure it doesn't do that in every single box. and truth be told, it's a specific purpose woofer, so if yoru using the recommended design, then according to yoru program, it's doing exactly what it's supposed to be. peaking at the nominal areas.

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

[Tommythecat 0]

I never said a model will predict the results of an enclosure in a car. But it should accurately predict what the enclosure and driver will do alone. That is not trivial. Being able to analyze that result against the cars transfer function, and then the actual combined results, is what makes sense.

[mrray13 30]

I never said a model will predict the results of an enclosure in a car. But it should accurately predict what the enclosure and driver will do alone. That is not trivial. Being able to analyze that result against the cars transfer function, and then the actual combined results, is what makes sense.

it should, but should isn't a definitive word. but the majority of the problem lies in the fact people don't map out the car's response and they handicap the program. and i know of no competitor that actually uses any kind of program because not a single program has ever gotten them close to what they could do with just plain old testing. entirely way too many varibles involved in car. (from flipping a sun visor down to sliding the seat up one notch, i've seen many things add or subtract a tenth or so)

and let's not forget the performance of subs who don't model well. several tc sounds sourced drivers model like shit in just about every program, yet in real world, they perform remarkably well. and i've seen drivers model very well, yet fall flat on their face in reality. a program isn't foolproof, but i'll agree that with the proper testing and mapping, a program can indeed give one a basic starting point.

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee