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Discussion Starter #1
First question; When I see a hump as in this graph, is this saying that the bass will peak at about 33hz (in spite of the fact the tuning is supposedly at 29.72 hz) ? I mean is that "2" on the left column in decibels ? Or is this just an arbitrary number to show "higher and lower" ? I mean, if it were 2 db's, that not very much. Barely an audible difference, right ?
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So this was my original plan.... only 3 cubes, for the two clam shelled 18"s..... and I thought it looked really good... flat, and musical, but the Techs at Skar thought it seemed kind of small. Well sure, 3 cubes for two 18"s does sound pretty darn small... but look how they modeled in WinIsd... Still looks the flattest and most musical to me, of anything I've tried....
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Okay, so now look at a 5 cu ft box.... The Skar Techs liked this better, but mentioned the little +2.5 peak, like it was "not great" but maybe okay... Uhhh... Okay. I mean, am I supposed to be trying for as small of peaks as possible ? Because in that case, we are back to the 3 cu ft box that they felt was kind of small ???
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OR..... I can go with 5 cubes, and just weight my PR's down a little more, to get something like this.... a smaller, deeper peak, but at the cost of a little dip in the 45 to 80 hz region... ???

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I just don't know by looking at the graphs, if any of these changes would even make an audible difference ? For those of you with WinIsd and enclosure building experience, do these designs look substantially different to you ? Is their one you would choose over the others, and why ? Would you try pushing one of these farther in any particular direction, and why ?
I'm still feeling like this setup cant help but be fairly loud, just by virtue of the Vd of my sub(s) and 2500 wts RMS. I'm really more concerned with making them sound really musical, and tight, and able to dig deep.
 

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Discussion Starter #2
And another related question... Driver excursion...
This graph is for that 3rd graph down, posted above... 5 cubes tuned to 30.48 The way I'm reading this graph, the sub is not getting anywhere close to its max excursion... which I don't know if this is a good thing ? Or, the sub is hardly doing anything it is designed to do ?
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The PR's are certainly flexing close their max design....
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Switch the mode from Transfer Function Magnitude to SPL, what does it look like then?

Have you entered your input power in the Signal tab?
 

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Discussion Starter #4
I have... but it just looks like this....
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I can totally see whats going on here.... the graph is just getting cut off ? How can I make the graph show me higher up on the scale ?
 

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Discussion Starter #5
Okay, I figured that out, but this sounds ridiculously quiet ? 119 DB's ?!?! I think a sneeze is louder than that ? Am I doing something wrong ? I know the rest of the system adds a little.... but this would seem to be building a 125 db setup ? Pretty sure every system I've ever built has been close to 140 db's ? What am I missing here ???
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I highly suspect your previous systems were not in the 140dB range (maybe though, if you had tons of power, and carefully designed sub/box). An output of 120dB is incredibly loud. Typical conversation is around 60dB, so for a stereo to play conversation levels it requires less than a single watt. From this chart, to acheive the volume of a "heavy truck" an average speaker would need 1 watt.
 

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First question; When I see a hump as in this graph, is this saying that the bass will peak at about 33hz (in spite of the fact the tuning is supposedly at 29.72 hz) ? I mean is that "2" on the left column in decibels ? Or is this just an arbitrary number to show "higher and lower" ? I mean, if it were 2 db's, that not very much. Barely an audible difference, right ?
The tuning frequency should be where the response drops 3 db (F3), or somewhere near that point. Theoretically, it should be where the peak is but it almost never works out like that. It looks like you're looking at the Transfer Function graph which shows gain in decibels, so the 2 on the left is decibels and a barely noticeable difference. The 3 cube graph looks perfectly fine to me. I usually like ported responses as flat as possible, and yours seems pretty flat. However, if you want it even flatter, you'll have to go lower with the tuning frequency and possibly higher (or maybe lower) with box volume.
 

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Discussion Starter #8
Okay, so several years ago, Mr. Steve Meade himself, helped me set all of my gains. At that time I was running the two 15" Daytons in a standard tuned, ported enclosure with the same amp (965 wt sub channel) Im running now.(which I am going to go on and run that exact setup in WinIsd for comparison later) and he told me that that setup was in the 140 db range. I had no reason to doubt him. So your saying 120 db's is incredibly loud ? Hmmm. I've never heard talk of 140 db's with barely an honorable mention. And I do know it works on a curve, so Id have thought that my crappy little stock Prius system (before the upgrades) would hit 120... and that freaking road noise would be 90 db's....

Hmmm. Anyway, like I say, I'm going to sit down and do some modeling of my Dayton 15"s and also my NVX 10"s for comparison. And now I'm hoping those model at like 110 or 115..... which again, seems stupid quiet to me....
 

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Okay, I figured that out, but this sounds ridiculously quiet ? 119 DB's ?!?! I think a sneeze is louder than that ? Am I doing something wrong ? I know the rest of the system adds a little.... but this would seem to be building a 125 db setup ? Pretty sure every system I've ever built has been close to 140 db's ? What am I missing here ???
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I've found that WinISD doesn't model spl very well for cars, I think it was designed for home theater or open air spaces, in any case it doesn't model the cabin gain we see in cars. I've used the Signal Tab> Listening place> Distance box to approximate the cabin gain, 0.046 meters in my car. An accurate spl measurement is helpful to dial that in, but you can't do that until after the box is installed. In short, take that spl estimate as a home theater estimate.
 

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You also need to account for cabin gain.

This is from MECA's 2020 competitions so far, across the entire US. S class is apparently for "daily driven vehicles with fully functional back seat(s)"

Top 10 Results for S Class
PLACECOMPETITORCLASSSTATESCORE
1Salena BallingerS4KY156.31
2Kyle RhodesS3CA149.54
3Jason HammerS3PA149.53
4Henry HillS4CA149.3
5Ryan CustardS3CA149.29
6Sean ParadisS2IN148.84
7Kyle McCoyS3OH148.78
8Rich CrawfordS2IL148.31
9Andrew CalvilloS2CA147.7
10James BowersS3FL147.58


These are competition level, dedicated SPL vehicles, just to put into perpective how loud 140dB's is.
 

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Okay, so several years ago, Mr. Steve Meade himself, helped me set all of my gains. At that time I was running the two 15" Daytons in a standard tuned, ported enclosure with the same amp (965 wt sub channel) Im running now.(which I am going to go on and run that exact setup in WinIsd for comparison later) and he told me that that setup was in the 140 db range. I had no reason to doubt him. So your saying 120 db's is incredibly loud ? Hmmm. I've never heard talk of 140 db's with barely an honorable mention. And I do know it works on a curve, so Id have thought that my crappy little stock Prius system (before the upgrades) would hit 120... and that freaking road noise would be 90 db's....

Hmmm. Anyway, like I say, I'm going to sit down and do some modeling of my Dayton 15"s and also my NVX 10"s for comparison. And now I'm hoping those model at like 110 or 115..... which again, seems stupid quiet to me....
Gijoe is partly right, 120 db IS incredibly loud, but only in the frequencies subwoofers DON'T play. A single 8 inch ported sub can hit 120 db in a hatchback or truck. You're building for a truck, I'd expect mid to high 140's for spl with your isobaric ported 18's, if not 150-ish.
 

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Okay, so several years ago, Mr. Steve Meade himself, helped me set all of my gains. At that time I was running the two 15" Daytons in a standard tuned, ported enclosure with the same amp (965 wt sub channel) Im running now.(which I am going to go on and run that exact setup in WinIsd for comparison later) and he told me that that setup was in the 140 db range. I had no reason to doubt him.....

Hmmm. Anyway, like I say, I'm going to sit down and do some modeling of my Dayton 15"s ......
You're on the right track there. Model the 15's, adjust the distance in the "Listening place" distance box until the spl gets to around 140, then use that distance for all modeling for that or very similar vehicles. I wouldn't doubt Steve Meade's estimate either.
 

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Gijoe is partly right, 120 db IS incredibly loud, but only in the frequencies subwoofers DON'T play. A single 8 inch ported sub can hit 120 db in a hatchback or truck. You're building for a truck, I'd expect mid to high 140's for spl with your isobaric ported 18's, if not 150-ish.
I understand that bass frequencies don't appear as loud, but we are talking about a box tuned to be musical, with a pretty flat response, not a box designed for SPL. I'm not sure 140dB is nearly as easy when designed for music 🤷‍♂️
 

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I understand that bass frequencies don't appear as loud, but we are talking about a box tuned to be musical, with a pretty flat response, not a box designed for SPL. I'm not sure 140dB is nearly as easy when designed for music
I had a 15 in a ported box modeled ruler flat down to 25 hz (tuning freq of 26 hz) with WinISD, it metered 148 db with 2200 watts in a hatchback AND it was quite musical and accurate. Tuned to 36 hz it metered 150.3 db and was boomy and crappy sounding.
 

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I had a 15 in a ported box modeled ruler flat down to 25 hz (tuning freq of 26 hz) with WinISD, it metered 148 db with 2200 watts in a hatchback AND it was quite musical and accurate. Tuned to 36 hz it metered 150.3 db and was boomy and crappy sounding.
How much do you think cabin gain contributed (there's a lot of it in a hatchback)? I guess what I'm getting at is that I don't think the dB levels of Chris' graph are inaccurate.
 

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How much do you think cabin gain contributed (there's a lot of it in a hatchback)? I guess what I'm getting at is that I don't think the dB levels of Chris' graph are inaccurate.
12-20 db under 30 hz. And WINISD doesn't model cabin gain, which is present in any vehicle whose longest internal measurement is shorter than one half wavelength. 80 hz has a 14 foot wavelength, so almost all passenger vehicles have very significant cabin gain. The gain rises as the frequency falls.
 

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12-20 db under 30 hz. And WINISD doesn't model cabin gain, which is present in any vehicle whose longest internal measurement is shorter than one wavelength. 80 hz has a 14 foot wavelength, so almost all passenger vehicles have very significant cabin gain. The gain rises as the frequency falls.
I know that WinISD doesn't show cabin gain. That's what I'm getting at, Chris seems to think the 119dB he shows on the graph is too low, I think it's accurate because it doesn't account for the cabin gain that will boost the low end once the box is in the car.
 

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I know that WinISD doesn't show cabin gain. That's what I'm getting at, Chris seems to think the 119dB he shows on the graph is too low, I think it's accurate because it doesn't account for the cabin gain that will boost the low end once the box is in the car.
Gotcha, it's accurate for a non-car environment.
I mistakenly stated "shorter than a wavelength" above, when it should be "shorter than half a wavelength".
 

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Okay, so several years ago, Mr. Steve Meade himself, helped me set all of my gains. At that time I was running the two 15" Daytons in a standard tuned, ported enclosure with the same amp (965 wt sub channel) Im running now.(which I am going to go on and run that exact setup in WinIsd for comparison later) and he told me that that setup was in the 140 db range. I had no reason to doubt him. So your saying 120 db's is incredibly loud ? Hmmm. I've never heard talk of 140 db's with barely an honorable mention. And I do know it works on a curve, so Id have thought that my crappy little stock Prius system (before the upgrades) would hit 120... and that freaking road noise would be 90 db's....

Hmmm. Anyway, like I say, I'm going to sit down and do some modeling of my Dayton 15"s and also my NVX 10"s for comparison. And now I'm hoping those model at like 110 or 115..... which again, seems stupid quiet to me....
If it helps, here's a formula to determine where cabin gain starts in your vehicle.
L is the longest measurement in your car in feet
F is the frequency where cabin gain starts.
F=565/L
Gain goes up as frequency goes down, we can see as much as a 20 db gain at 16 hz. (maybe more)
 

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Discussion Starter #20
Much thanks to both of you. This has been a very interesting discussion. I am hoping for a lot of cabin gain then 🙂 Although I've heard that relatively speaking, F150 Supercabs in particular, kind of suck for bass gain. It might have something to do with the fact that my cabin, unlike a Supercrew cab, has no mid-pillars so the cab tends to flex in the middle like a big wicker basket 😲

But again, as I said, I am going to go ahead and input all the info for both my Dayton 15"s as well as my NVX 10"s so I can get a better idea. Again, if it says these are at least a little quieter, then I'll be okay with all of this. Well, I'm going to model the 15"s in an Isobaric setup, just as they are at the moment.... And I guess how they were in the standard tuned ported enclosure before. If the 18"s were only "as loud" as that was, but deeper, and more musical, I'd be okay with that too.
 
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