SUV's benefit from "smaller" enclosures rather then "bigger" enclosures.

[adrenalinejunkie]

Ran into this a few times and would like to know if it's true along with some information on how the volume makes a difference on a SUV/car.For example, I've run into people that said a sealed enclosure with less volume is better in a SUV rather in a car and that a sealed enclosure with more volume is better on a car.

[SaturnSL1]

That doesn't make any sense.

[adrenalinejunkie]

Originally Posted by SaturnSL1

That doesn't make any sense.

Doesn't make sense to me either. I layed it out just how they layed it out to me.I'm assuming this has to do with transfer funtion though, but I'm trying to understand how this is true.

[Jroo]

Never heard anything about size of the box doing anything in an SUV. Type of enclosure yes (ex. sealed/ported/bandpass), but not size.

[niceguy]

Don't think I've even seen an enclosure in an SUV that's less than 4-6cf...

[Bayboy]

Without assuming too much I understand the statement, but it can go either way depending on the size of the SUV and it's associated transfer function. For instance I did a install in my S10 Blazer 4 door and it really needs a sub with a lower F3 no matter sealed or ported. Anything with a roll-off around 50 hz (sealed of course) really needs deep cuts in the upper bass (60 to 80hz) and boosting in the lower (below 40hz) to get the sound I like.

Now compared to a install I did in a later model new body style Trailblazer with the inline 6 motor , that same sub/box was tuned way too low. Now I would have thought being a slightly bigger vehicle would have given opposite results although I just gave it a test to see anyway. She had no EQ, but the bass was entirely deep due to the vehicle's construction and could have went with a smaller box or much higher xover setting coupled with turning the sub down to match the stock speakers. That one totally fooled me as I didn't measure it's function. I accredited it to the Trailblazer's better sound dampening from the manufacturer.

In a much larger SUV like a Expedition or Suburban, surely it may have been different needing a bit more lower extension to match the transfer function.

[adrenalinejunkie]

Here's some info I got from JL AUDIO.

"1:
Very small vehicle (small pick-up truck)
Longest dimension: 120 cm (47 inches)
Starting frequency: f = speed of sound/twice the longest dimension
f = (34500 cm/sec)/(240 cm)
f= 144 Hz
Sonic effect: these vehicles tend to sound very "boomy". There seems to be a lack oflow-end, but it is probably more accurate to say that there is an over-abundance
ofupper bass which tends to overshadow the low-end.
What to do: Design a subwoofer enclosure with a fairly flat response curve. For
example, a low Q sealed box or a larger, lower-tuned ported box. Choose a low
crossover point for the subwoofer (between 50 and 70 Hz). Stagger the crossoverfrequencies between the subwoofer and the satellites if necessary.
2:
Medium-Size Vehicle
Longest dimension: 172 cm (68 inches)
Starting frequency: f = speed of sound/twice the longest dimension
f = (34500 cm/sec)/(344 cm)
f=100Hz
Sonic effect: These vehicles tend to sound quite good. There is a good balance
between the gain on the extreme low-end'and the upper-bass which complements the
sound of medium Qtc sealed enclosures and well-tuned ported enclosures.
What to do: Follow the enclosure recommendations in the JL AUOIO Reference
Manual directly. Choose crossover points between 80-1 OOHz.
3:
Very Large Vehicle (Full-size Van)
Longest dimension: 351 cm (138 inches)
Starting frequency: f = speed of sound/twice the longest dimension
f = (34500 cm/sec)/(702 cm)
f o 49 Hz
Sonic effect: These vehicles tend to sound very "heavy" on the extreme low-end. It
sounds like the vehicle lacks upper-bass impact, but it is probably more accurate to
say that there is an over-abundance of extreme low-end which is overshadowing the
upper bass.
What to Do: Design a Subwoofer enclosure with a "peakier" response curve. For
example, a higher Qtc sealed box or a smaller, higher tuned ported enclosure.
Choose a high crossover point for the Subwoofer (between 90 and 120 Hz). It oftenhelps to overlap the crossover frequencies between the subwoofer and the
satellites."

[Bayboy]

That seems like a fairly general guide that I would not follow at all. From my experiences it has been fairly opposite and depends heavily on the vehicle itself. The only way to really know is to take a sub with a known open field response then compare it to the response when placed within the target vehicle (closed field).


You would be surprised that often a smaller vehicle can get away with a fairly high roll-off around 60hz or more because the low end lift is greatly exaggerated compared to that of a larger vehicle. I would still target a low Qtc for a smooth plot throughout it's bandwidth, but it's F3hz point can vary depending on what you are trying to achieve and the vehicle itself. For instance I run all Peerless 830876 XXLS subs in my vehicles. One is a 96 Ford Ranger Xtra Cab, the other is a 91 S10 Blazer 4 door. With a single sealed sub the low end is pretty full with a slightly exaggerated low end that can require cuts around 40-60hz to smooth things out. In the blazer with that same box I have to boost the low end around 30hz a few db and cut around 60-80hz heavily to get that same sound. The Blazer clearly could use a sub/box with a lower F3hz point while the Ranger is fine as it is. This could and probably will vary from vehicle to vehicle.

[Bayboy]

There is a graph on here somewhere that Andy Weyhemer posted that shows the different response. I have one I studied from Vance Dickason's book that aligns to what Andy showed and the results are fairly real. I'm not sure about JL's though. Of course they may have been referring specifically to their subs. It's just hard to gauge such a thing without testing. The best you can do is shoot for a smooth Qtc plot (.707) and employ a good EQ which is always a good option regardless. The most usable EQ bands I've found were 30, 45, 60, 80, and 120. Yes if you can have all of them at once in an EQ like a 31 band then you're pretty much in control.

[thehatedguy]

JL is describing cabin gain. The smaller the room, the higher in frequency it occurs.

[BuickGN]

Assume JL is right and you have a vehicle with an over abundance of low end sub bass. I would still go with a larger less peaky box and use EQ to cut the bottom end and enjoy the added efficiency and lower power requirements. It seems like that was written with no eq capability in mind.

[Bayboy]

Originally Posted by BuickGN

Assume JL is right and you have a vehicle with an over abundance of low end sub bass. I would still go with a larger less peaky box and use EQ to cut the bottom end and enjoy the added efficiency and lower power requirements. It seems like that was written with no eq capability in mind.

Perhaps that's why it seemed backwards to me... rather moving box Q I rather shoot for woofers with a roll-off that will mate better and then EQ.

[thehatedguy]

There was a time in the not too distant history of car audio when you didn't have the ability to EQ something unless you bought an outboard expensive EQ...and not too many things to tune with other than some very expensive stand a lone RTAs.

[cajunner]

Originally Posted by thehatedguy

There was a time in the not too distant history of car audio when you didn't have the ability to EQ something unless you bought an outboard expensive EQ...and not too many things to tune with other than some very expensive stand a lone RTAs.

right, right.

the plethora of tuning equipment available nowadays, is almost like moving from hieroglyphics to the electric typewriter in the ability to change response curves.

plethora, say it with me...

plethora.

[Bayboy]

I can't go along with that. A decent parametric or even 9 band EQ has been out long enough to omit that suggestion from JL. We are talking about the early 90's.....

[thehatedguy]

They might have been on the market, but retail sales and use of such a thing has pretty much been nil until recently...like 6-7 years. Good ones were just plain expensive.

I worked at a large local chain of shops in the early-mid 2000s and we had one RTA for then about 10 stores...and there wasn't more than a handfull of people that knew how to use it for anything other than measuring SPL.

Bayboy, you ever worked retail car audio?

[Bayboy]

Oh you are talking about the use of an RTA.... I thought you were referring to the use of an EQ.


No I have never worked in that area, although I have worked with installers on side jobs back in the 90's. Yes, I'm old....

[Andy Wehmeyer]

OF course, all of this depends on the shape of the bass respons that you prefer. In addition, small adjustments in the size of a sealed box will have very little effect on what you hear, especially if those size differences change the Qtc of the box between...oh...say....6 and .8

I'd say that I disagree with the statement almost completely--when it comes to practice. Here's why: It seems that the suggestion is meant to add some midbass (60-80Hz) while limiting the sub bass. This is a haphazard way to EQ unless you're doing all of this by knowing what the "transfer function" of the car is by measuring it and carefully modeling the response of the box to compliment it. The down side is that all of that midbass boost from a super high Q box and woofer combo and the attenuation of the lower frequencies come at a huge cost of inefficiency. Rather than building a tiny box and buying a huge amp, build a vented box, a smaller amp and an EQ. Much better solution.

[Bayboy]

Andy that definitely makes more sense and should be general knowledge IMO. I'm not sure when JL wrote that suggestion, but it's not one I would follow. Creating a peak in the upper band of a sub is never a good idea. That is the old way where we used Qtc's in the range of .9-1.1, then twisted the knob of death (bass boost). Of course, back then pop music favored that somewhat...

[adrenalinejunkie]

That "guide" that I posted above was written on 1996.

[Bayboy]

Uhhhh yeah, that would make a little sense as it appeals to that time. Perhaps they should update that.

[rugdnit]

Originally Posted by cajunner

right, right.

the plethora of tuning equipment available nowadays, is almost like moving from hieroglyphics to the electric typewriter in the ability to change response curves.

plethora, say it with me...

plethora.

https://www.youtube.com/watch?v=-mTUmczVdik