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post #31 of 55 Old 07-04-2013, 07:22 AM
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Quote:
Originally Posted by LTD02 View Post


bill, he mentioned using up to a 50"x53"
mouth firing into a car cabin. i was simply
suggesting that might cause the cabin to
function more like an extension of the horn
with a closed mouth, then a horn firing
into a room.
Irrespective of the size of the 'room' the impedance matching of the driver to the surrounding air by the horn remains, so it still has much higher electro/acoustical transfer efficiency than a direct radiator.
I remember one screwball who thought it was a good idea to put a THT in his SUV, until the pressure it created cracked his windshield. eek.gif

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post #32 of 55 Old 07-04-2013, 08:03 AM
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That's where a zero deductible comprehensive comes in handy.
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post #33 of 55 Old 07-04-2013, 09:21 AM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post

"You can take what I've been doing in my car
for a year and the math doesn't add up..."

that is an intriguing comment. i would be
interested to know what you are doing in your
car where math doesn't add up.

i can't think of any examples where math
doesn't work. from tiny two-way bookshelves
to the 40 box vertical subwoofer line array
that metallica uses, the math seems to work
everywhere.

"Now in terms of the throat opening, would it
be possible to make it large and shrink it
without changing the angle of the horn, or
would that be counter-productive? Basically,
so I can keep the same horn shape, but so I
can tweak it inch by inch."

no reason why that couldn't be done.

In my car, a hatchback, I have a single 8" driver with a 57 hz Fs and 83.2 dB efficient in a 1 cu. ft. ported enclosure. 5000 (give or take a few) clamped watts doing 151.2 dB. If I take a stock spider sub that brings the Fs down to 34 hz I lose about 0.5 dB. PA math may work out because it's open area, closer to a lab simulation. That math doesn't work out in a car, never does. I can take 2 identical enclosures just like that, apply 6000 watts to the pair (adding 1000 watts, doubling cone area, same efficiency enclosure) and only gain 1.5 dB.

Quote:
Originally Posted by Bill Fitzmaurice View Post

+1. The math always works. One's understanding of the math, maybe not.
Horns work just fine in cars, they are after all just small rooms.
Unfortunately, they were incorrect.
I think I know what your intent is. It won't work. Been there, done that. One other bit of advice, if you want to get maximum output at 50Hz start with a driver Fs no lower than 60Hz and Qes no higher than 0.3.

See my post above. Also consider this, the sub I use to do that with, at 62 hz, has an Fs of 57 hz and a Qes of 0.6. There isn't another driver I've tried that can match it. In my findings, the closer you get your Fs to your playing freq the better, going above will fail and going below works if you have progressive spiders. This particular sub I use has linear spiders and a nearly flat CMS curve so matching Fs to playing freq works best.

Now, in terms of your "been there, done that" can you go further into detail on what you did exactly? Perhaps any pics of it?

Quote:
Originally Posted by LTD02 View Post

i was thinking about your problem:

maximum spl in a car with as few
of drivers and power as possible
at a single frequency.

to any scientist of acoustics, they
would say create a resonant chamber,
or, lots of them.

so...

in theory, why don't you just turn
the entire cabin into a resonant chamber
by porting it or using passive radiators
to the outside of the vehicle? :-)

so some sort of vented or bandpass design
would excite the cabin of the vehicle,
just like everybody is doing right now,
while the energy would then be further
enhanced by the resonant feedback from the
port or the p.r. to the outside of the
vehicle.

if you use such a design and win, let me
know, an spl world record would be a fun
item to add to the resume as would seeing
a car with a giant smokestack sticking out
of it win an spl competition. :-)


........

"Horns work just fine in cars, they are
after all just small rooms."

bill, he mentioned using up to a 50"x53"
mouth firing into a car cabin. i was simply
suggesting that might cause the cabin to
function more like an extension of the horn
with a closed mouth, then a horn firing
into a room.

The vehicle must be sealed, all windows and doors closed, with no modifications to the interior or like you are suggesting. Now, considering the interior as an extension of the horn. Would that function like the inside of a port where it is rather loud? That could operate as a benefit to the application.
Quote:
Originally Posted by Bill Fitzmaurice View Post

Irrespective of the size of the 'room' the impedance matching of the driver to the surrounding air by the horn remains, so it still has much higher electro/acoustical transfer efficiency than a direct radiator.
I remember one screwball who thought it was a good idea to put a THT in his SUV, until the pressure it created cracked his windshield. eek.gif

That is the kind of pressure I'm after.
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post #34 of 55 Old 07-04-2013, 10:03 AM
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i put a single lilmikes microwrecker in the back of my chevy silverado short bed that has a fiberglass cap on it , it was friggen loud, the presure from one microwrecker was enough that i thought i would bust the fiberglass cap and ended up pulling it out after only playing a few test tones and sweeps.

granted the bed area is much larger then then the cabin area but i think it would still work well with the horn mouth firing into the cabin , if i have time this weekend i could pull mybackseat out of the cab and there should be just enough room for a single horn i could try it
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post #35 of 55 Old 07-04-2013, 10:25 AM
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"The vehicle must be sealed, all windows and
doors closed, with no modifications to the
interior or like you are suggesting. Now,
considering the interior as an extension of
the horn. Would that function like the inside
of a port where it is rather loud? That could
operate as a benefit to the application."

that is what i was talking about earlier. i'm
pretty sure that if you take a horn and seal
off the end, then it functions essentially
as a sealed chamber not as a horn in the low
frequencies.

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post #36 of 55 Old 07-04-2013, 10:38 AM
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Quote:
Originally Posted by LTD02 View Post

"The vehicle must be sealed, all windows and
doors closed, with no modifications to the
interior or like you are suggesting. Now,
considering the interior as an extension of
the horn. Would that function like the inside
of a port where it is rather loud? That could
operate as a benefit to the application."

that is what i was talking about earlier. i'm
pretty sure that if you take a horn and seal
off the end, then it functions essentially
as a sealed chamber not as a horn in the low
frequencies.

i can test that for u guys fairly easy this weekend , i just need to measure out the back of the truck to make sure the cab would actually fit inside the cab of the truck. if it does u dont get a much smaller airspace then that of a pickup truck cabin , and i could take some spl and REW measurements and compare them to a small room and see what happens
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post #37 of 55 Old 07-04-2013, 10:44 AM
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have you measured the transfer function
of the intended cabin?

(in other words, measured a sealed sub
in 2pi space, then plopped that sub in the
car and remeasured.)

btw, here is the back-of-the-envelope math:

83 db sensitive driver
+12 db for a peaking ported enclosure
+37 db for 5000 watts
+18 db for cabin gain relative to 2pi space
+3 db for peak vs rms
-2 db for a little power compression
151 db

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post #38 of 55 Old 07-04-2013, 10:47 AM
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i dont have a sealed sub to compare against , only other thing i have is a set of pheniox gold 12's in a slot vented enclosure and that wont work to measure against will it ?
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post #39 of 55 Old 07-04-2013, 01:35 PM - Thread Starter
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Quote:
Originally Posted by davece View Post

i put a single lilmikes microwrecker in the back of my chevy silverado short bed that has a fiberglass cap on it , it was friggen loud, the presure from one microwrecker was enough that i thought i would bust the fiberglass cap and ended up pulling it out after only playing a few test tones and sweeps.

granted the bed area is much larger then then the cabin area but i think it would still work well with the horn mouth firing into the cabin , if i have time this weekend i could pull mybackseat out of the cab and there should be just enough room for a single horn i could try it

That would be an ideal, real world test. But do you have an SPL meter for accuracy?

Quote:
Originally Posted by LTD02 View Post

"The vehicle must be sealed, all windows and
doors closed, with no modifications to the
interior or like you are suggesting. Now,
considering the interior as an extension of
the horn. Would that function like the inside
of a port where it is rather loud? That could
operate as a benefit to the application."

that is what i was talking about earlier. i'm
pretty sure that if you take a horn and seal
off the end, then it functions essentially
as a sealed chamber not as a horn in the low
frequencies.

But is that a thought, or something that has actual data to back it up?
Quote:
Originally Posted by davece View Post

i can test that for u guys fairly easy this weekend , i just need to measure out the back of the truck to make sure the cab would actually fit inside the cab of the truck. if it does u dont get a much smaller airspace then that of a pickup truck cabin , and i could take some spl and REW measurements and compare them to a small room and see what happens

That would be awesome, again if you have an SPL meter for accuracy.
Quote:
Originally Posted by LTD02 View Post

have you measured the transfer function
of the intended cabin?

(in other words, measured a sealed sub
in 2pi space, then plopped that sub in the
car and remeasured.)

btw, here is the back-of-the-envelope math:

83 db sensitive driver
+12 db for a peaking ported enclosure
+37 db for 5000 watts
+18 db for cabin gain relative to 2pi space
+3 db for peak vs rms
-2 db for a little power compression
151 db

That is literally making stuff up. How do you KNOW the box has a 12 dB peak? How do you know cabin gain when you don't know the cabin size or transfer function? The power was taken with true RMS meters, so it is RMS power, not peak. It's also worth mentioning the metering is done over 3 samples which are averaged over a period of 3 seconds, not peak there either. How can you define 2 dB for power compression? You don't know the coil temperature, or coil rating for that matter. I can throw numbers together to match up too when they're all fabricated with no data. So sure of yourself? How about a challenge. Tell me the SPL of my truck which I have never metered. 12 8's with 81.5 dB sensitivity in a ported enclosure with estimated 6000 watts total. Sometime next week I'll meter it.
Quote:
Originally Posted by davece View Post

i dont have a sealed sub to compare against , only other thing i have is a set of pheniox gold 12's in a slot vented enclosure and that wont work to measure against will it ?

For the sake of argument, the same driver and quantity and power would have to be used between the different enclosures. But if you've got the time and don't mine, humor me, test it, and tell me what subs are used with the results and I can probably figure out realistic gains.
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post #40 of 55 Old 07-04-2013, 02:01 PM - Thread Starter
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Also, LTD02, I'd like to point you that you left out your explanation as to why adding 1000 watts and doubling cone area yields a 1.5 dB gain. Theoretically the power compression you claim I have should be less as I'm dividing power between 2 drivers and enclosure efficiency didn't change so that should be a 3.6 dB gain, minimum, using your math.
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post #41 of 55 Old 07-04-2013, 04:03 PM
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emf i actually have access to a termlab setup , i do have a portable spl meter but its flaky over 135db
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post #42 of 55 Old 07-04-2013, 06:26 PM
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"But is that a thought, or something that
has actual data to back it up?"

just a thought. kind of like if you put
a driver in a sealed enclosure, it doesn't
really matter what the shape of the sealed
enclosure is. once you are in the pressure
zone, i think you are in the pressure zone.
that's all i was thinking there.

putting a large horn with something like
a 50x50 mouth in a car would seem to be
more like adding a little bit of horn length
to the horn and then sealing it off, then
it would be to a horn firing into a room.


"That is literally making stuff up."

not really. it is a simple mathematical
way to get to 151db using what we know about
sound. you said that you were violating math
with your system and i don't see it that way
at all. that is all i was trying to show there.

"How do you KNOW the box has a 12 dB peak?"

i don't know. a 12db peak isn't out of the
question though for a max spl ported cab
though. it is just one way that you could get
to about 150db.

"How do you know cabin gain when you don't
know the cabin size or transfer function?"

i just used the difference between 1/2 space
and 1/16 space. 1/8 space is corner-loading
and a car at 50hz will provide more gain than
that. it could be a little more or a little less
depending on structural losses, how close
to the boundary the measurement was taken,
and some other things. but it wouldn't surprise
me if you were getting 18db of gain vs. 2pi space.

"How can you define 2 dB for power compression?"

random guess. maybe more. maybe less. but the
order of magnitude seemed about right for burping
a big load of power for a short bit of time.

"I'd like to point you that you left out your
explanation as to why adding 1000 watts and
doubling cone area yields a 1.5 dB gain. Theoretically
the power compression you claim I have should be
less as I'm dividing power between 2 drivers and
enclosure efficiency didn't change so that should
be a 3.6 dB gain, minimum, using your math."

kind of...if you account for everything else that
may have changed. but i don't see any discussion of
any of the other variables and there are simply too
many unknowns to narrow it down to why you didn't measure
2 db at 150db. for all i know, that could be within
the tolerance of your measurement rig at that level.

Listen. It's All Good.
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post #43 of 55 Old 07-05-2013, 12:27 PM
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1 micro wrecker in the cabin of my ext cab silverado, measured at the dashboard , driven with a single mtx thunder mono amp 350W rms

edit

the driver in the cab is a alpine type s 15

ill take a room measurement later tonight
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post #44 of 55 Old 07-07-2013, 02:37 PM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post

"But is that a thought, or something that
has actual data to back it up?"

just a thought. kind of like if you put
a driver in a sealed enclosure, it doesn't
really matter what the shape of the sealed
enclosure is. once you are in the pressure
zone, i think you are in the pressure zone.
that's all i was thinking there.

putting a large horn with something like
a 50x50 mouth in a car would seem to be
more like adding a little bit of horn length
to the horn and then sealing it off, then
it would be to a horn firing into a room.

I see where you're coming from with the added length, but there is a point where that shape not being part of the horn changes nothing in regard to the horn. So lets say it is acting like you're sealing it off, why can't that be loud?

Quote:
"That is literally making stuff up."

not really. it is a simple mathematical
way to get to 151db using what we know about
sound. you said that you were violating math
with your system and i don't see it that way
at all. that is all i was trying to show there.

No, it is making things up because you're throwing out figures to match a result you already know. That's rigging results. 1+4=5 and 2+3=5 but how did you get 1,2,3,and 4 data points? Same result, made up figures. It's defying math because you can't simply guess power compression, or guess cabin gain, or guess port gain. If you model my enclosure and plug in all the power numbers and all that, the result isn't what actually happens.
Quote:
"How do you KNOW the box has a 12 dB peak?"

i don't know. a 12db peak isn't out of the
question though for a max spl ported cab
though. it is just one way that you could get
to about 150db.

That's my point, it's not an unreasonable guess, but that's not data, that's a fabricated figure.
Quote:
"How do you know cabin gain when you don't
know the cabin size or transfer function?"

i just used the difference between 1/2 space
and 1/16 space. 1/8 space is corner-loading
and a car at 50hz will provide more gain than
that. it could be a little more or a little less
depending on structural losses, how close
to the boundary the measurement was taken,
and some other things. but it wouldn't surprise
me if you were getting 18db of gain vs. 2pi space.

Again, that's a fabricated guess, not data. Everything that you're referring to has to do with a room, not a car. Cars act differently, much differently, and the louder you go the more different they act. The resonant frequency of a vehicle changes with pressure even.
Quote:
"How can you define 2 dB for power compression?"

random guess. maybe more. maybe less. but the
order of magnitude seemed about right for burping
a big load of power for a short bit of time.

I couldn't have said it better myself, guess, not data. To accomplish my goal I need data, not guesses. I can tell you per my testing at various power levels (actual clamped power) I don't have 2dB of power compression.
Quote:
"I'd like to point you that you left out your
explanation as to why adding 1000 watts and
doubling cone area yields a 1.5 dB gain. Theoretically
the power compression you claim I have should be
less as I'm dividing power between 2 drivers and
enclosure efficiency didn't change so that should
be a 3.6 dB gain, minimum, using your math."

kind of...if you account for everything else that
may have changed. but i don't see any discussion of
any of the other variables and there are simply too
many unknowns to narrow it down to why you didn't measure
2 db at 150db. for all i know, that could be within
the tolerance of your measurement rig at that level.

I told you everything that changed. 2 identical subs, in 2 identical enclosures, with an additional 1000 watts in the same environment. The tolerance of the equipment is 1/100th of a dB. What I was getting at is you math doesn't work for this application, at all.

Quote:
Originally Posted by davece View Post



1 micro wrecker in the cabin of my ext cab silverado, measured at the dashboard , driven with a single mtx thunder mono amp 350W rms

edit

the driver in the cab is a alpine type s 15

ill take a room measurement later tonight

Any progress in comparison testing?
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post #45 of 55 Old 07-07-2013, 02:58 PM
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unfortunatly no i havent had the time, i had a gig last night and ive been busy prepping my camaro to go in for paint on this coming friday ., ill get to it soon though, i also have enough 3.4 wood left over i could build aproper vented box for the alpine and test that intruck as well but that will take some more time , then getting an in room measurement of the microwrecker
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post #46 of 55 Old 07-07-2013, 03:49 PM - Thread Starter
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Not a huge rush, still waiting on the red tape to clear on the vehicle it's going in. I appreciate the extra mile of effort.
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post #47 of 55 Old 07-07-2013, 05:29 PM
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"So lets say it is acting like you're
sealing it off, why can't that be loud?"

it can be loud. all i was thinking is that
once you are down into the pressure vessel gain
region, you are already coupling to the air
pretty well, so adding a horn might not do anything.

kind of like if you took a sealed sub and put it
in the car, then changed the shape of the cabin
into a triangle shaped like a horn. i don't think
that would do anything as far as further loading
the driver in the pressure vessel gain region.



"No, it is making things up because you're
throwing out figures to match a result you
already know. That's rigging results."

i was just showing that under a reasonable set
of assumptions, the math works fine.



"If you model my enclosure and plug in all the
power numbers and all that, the result isn't
what actually happens."

then the model is incomplete. it is not accounting
for something that you are doing.



"That's my point, it's not an unreasonable guess,
but that's not data, that's a fabricated figure."

i didn't suggest that it was data. just a reaonable
path to get to your measured result using common
known math.



"Everything that you're referring to has to do
with a room, not a car. Cars act differently,
much differently, and the louder you go the
more different they act."

the physics of acoustics don't change
based on the size of the room, whether it is large,
small, car, living room, truck, stadium, or whatever.

maybe, you are trying to make a different point
that is getting lost.



"I couldn't have said it better myself, guess,
not data. To accomplish my goal I need data,
not guesses."

ok. but you came into the forum to ask for guesses
on how your horn vent would work. nobody has
the data that you need, so folks have suggested
various ways to model and various theories for
why it might or might not work.



"I can tell you per my testing at various power
levels (actual clamped power) I don't have 2dB
of power compression."

ok. you are aware that clamp meters don't measure
power, right?



"I told you everything that changed. 2 identical
subs, in 2 identical enclosures, with an additional
1000 watts in the same environment. The tolerance
of the equipment is 1/100th of a dB. What I was getting
at is you math doesn't work for this application, at all."

two sources is different from one source. you could
easily be getting a cancellation, or partial, based on
placement of the second sub. i won't suggest that you
had them wired out of phase by accident, but mistakes
can happen, no? could it have been erroneous data.

Listen. It's All Good.
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post #48 of 55 Old 07-07-2013, 08:08 PM
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i will tell u that a horn in the cabin works really well , back when i used to compete i ran 2 well built bandpass boxes with 12's that did 147.7, that single 15 did about 137db at about half power.
i know lil mike has some in room measurements of that cab and they wont go that high .

instead of remeasuring in room i think a better test would be to build the proper vented box for that 15 put it in the truck and remeasure to see the difference , more of an apple to apples type thing


and no problem at all man im really interested in building a horn type cab to install into my twin turbo powered 89 camaro so all this testing will tell me if its really worth the extra effort
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post #49 of 55 Old 07-07-2013, 08:32 PM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post


"No, it is making things up because you're
throwing out figures to match a result you
already know. That's rigging results."

i was just showing that under a reasonable set
of assumptions, the math works fine.

Yeah, the math can work fine, if you're just making up numbers for an answer you already know.


Quote:
"If you model my enclosure and plug in all the
power numbers and all that, the result isn't
what actually happens."

then the model is incomplete. it is not accounting
for something that you are doing.

Right, its not modelling for 1 key factor, reality. The reality is you can't simulate every fine detail that would make that accurate. I'll be glad to give you exact dimensions of my car interior, give you sub parameters, and box specs, then you give me a power level and tell me exactly what number it does. Then you can explain why that number changes when I move the box to the left 4".

Quote:
"Everything that you're referring to has to do
with a room, not a car. Cars act differently,
much differently, and the louder you go the
more different they act."

the physics of acoustics don't change
based on the size of the room, whether it is large,
small, car, living room, truck, stadium, or whatever.

maybe, you are trying to make a different point
that is getting lost.

I'm guessing you've never built anything for a car, ever. If it were as simple as simulation, everybody would be doing 160's with a pair of 10's and one of the loudest vehicles in the world wouldn't be struggling to get 1 more tenth for the last 4 years. FYI, hes at a 181.8.

Quote:
"I couldn't have said it better myself, guess,
not data. To accomplish my goal I need data,
not guesses."

ok. but you came into the forum to ask for guesses
on how your horn vent would work. nobody has
the data that you need, so folks have suggested
various ways to model and various theories for
why it might or might not work.

Somebody DOES have the data I need. That data can be had in the form of "if you build a horn like this, it does this", it's not specific to how I'm using it. The general rules I was given that were said to be false I have found to be sufficient for the purpose.
Quote:
"I can tell you per my testing at various power
levels (actual clamped power) I don't have 2dB
of power compression."

ok. you are aware that clamp meters don't measure
power, right?

You are aware clamp meters are a required tool to measure power, right? Output current x output voltage = wattage, those of us who do that call it "clamped power" because it's not estimated power, or simulated power, or theoretical math power (using only AC voltage). 2 meters and ohms law gives actual data. I know resting DCR, I know actual playing impedance, I know impedance rise, and I know actual wattage, all because of that clamp meter that doesn't measure power.
Quote:
"I told you everything that changed. 2 identical
subs, in 2 identical enclosures, with an additional
1000 watts in the same environment. The tolerance
of the equipment is 1/100th of a dB. What I was getting
at is you math doesn't work for this application, at all."

two sources is different from one source. you could
easily be getting a cancellation, or partial, based on
placement of the second sub. i won't suggest that you
had them wired out of phase by accident, but mistakes
can happen, no? could it have been erroneous data.

You're right, I could have cancellation. But that math of yours doesn't have a place for cancellation in dB's, does it? Can you simulate cancellation of having another identical enclosure directly next to the other one (like I said earlier) firing the same direction in the same manner? No. That's where DATA comes in, not simulation and math that doesn't work.
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post #50 of 55 Old 07-07-2013, 08:59 PM
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LilMikes 911 TH was quite awesome to see. I believe it had four 15's in the bed of the truck.
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post #51 of 55 Old 07-09-2013, 01:44 PM
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sorry i havent had time to remeasure for ya yet ive just been tied up with my car





that how it sits as of right now and its going for paint on friday.

on a side note ive drawn up a ported box for the alpine 15 based on alpines recomended box specs , ill get that built soon and measure that inside the truck for ya so u can see the difference between the tapped horn and the vented box
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post #52 of 55 Old 07-09-2013, 05:57 PM
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"Yeah, the math can work fine, if you're
just making up numbers for an answer you
already know."

that kind of model is called an explanatory model.
http://en.wikipedia.org/wiki/Explanatory_model

it takes the performance and breaks it down into
components in order to explain what was going on.

what you are really saying is not that "math doesn't
work in your car",but that you don't have a model
that can accurately predict the performance, which
is an altogether different idea and with which
i find no disagreement.



"Output current x output voltage = wattage..."

it's actually not quite that simple which is why
i asked what kind of signal you were using.

Listen. It's All Good.
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post #53 of 55 Old 07-09-2013, 06:16 PM
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"You're right, I could have cancellation. But that
math of yours doesn't have a place for cancellation
in dB's, does it? Can you simulate cancellation of
having another identical enclosure directly next to
the other one (like I said earlier) firing the same
direction in the same manner? No."

i suppose that it depends on the conditions. boundary
reflection cancellation would be the most obvious, but
i'm guessing that you were down in the pressure vessel
gain region for the vehicle? so that probably isn't it.
another type of cancellation can be caused by absorption.
if something about adding the second enclosure changed
a resonant frequency of a panel, it could be turned into
a bass absorber where it wasn't when being tested with
one sub. there are quite a few possibilities for what
could have caused the cancellation, but without knowing
a little more, it is kind of tough to say what it might
have been.

one thing that might be worth having a look at is the
phase response of the second sub relative to the first.
putting the second sub on a delay and finding the point
where the deepest cancellation occurs and then flipping
polarity should provide maximum summation, at least
holding all other factors constant.

Listen. It's All Good.
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post #54 of 55 Old 07-09-2013, 08:47 PM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post

"Yeah, the math can work fine, if you're
just making up numbers for an answer you
already know."

that kind of model is called an explanatory model.
http://en.wikipedia.org/wiki/Explanatory_model

it takes the performance and breaks it down into
components in order to explain what was going on.

what you are really saying is not that "math doesn't
work in your car",but that you don't have a model
that can accurately predict the performance, which
is an altogether different idea and with which
i find no disagreement.

Further proving my point, that isn't data, that's guessing. You don't have the data to do the math, making it irrelevant.


Quote:
"Output current x output voltage = wattage..."

it's actually not quite that simple which is why
i asked what kind of signal you were using.

Ohms law says otherwise. It's every bit of that simple.
Quote:
Originally Posted by LTD02 View Post

"You're right, I could have cancellation. But that
math of yours doesn't have a place for cancellation
in dB's, does it? Can you simulate cancellation of
having another identical enclosure directly next to
the other one (like I said earlier) firing the same
direction in the same manner? No."

i suppose that it depends on the conditions. boundary
reflection cancellation would be the most obvious, but
i'm guessing that you were down in the pressure vessel
gain region for the vehicle? so that probably isn't it.
another type of cancellation can be caused by absorption.
if something about adding the second enclosure changed
a resonant frequency of a panel, it could be turned into
a bass absorber where it wasn't when being tested with
one sub. there are quite a few possibilities for what
could have caused the cancellation, but without knowing
a little more, it is kind of tough to say what it might
have been.

one thing that might be worth having a look at is the
phase response of the second sub relative to the first.
putting the second sub on a delay and finding the point
where the deepest cancellation occurs and then flipping
polarity should provide maximum summation, at least
holding all other factors constant.

I know the data, I've tested the data, I know why. I asked for your explanation because your math is wrong, which I proved. You can't simply take simulation and math and draw the conclusion that actually happened. You have no way of simulating the environment or its effects, making simulations inaccurate outside of a lab. I merely saved $10,000 and 100 hrs by simply building it and going "that doesn't work" after real world testing.
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post #55 of 55 Old 07-09-2013, 09:18 PM
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so...what caused the mysterious reduction?

Listen. It's All Good.
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