I just built a sub box with three Elemental Designs SQ10s. I built this box to go exactly where a vert partition would go with the 3 tens firing forward towards the passenger area. This sealed box has 1.0 cubic feet of total internal volume. This setup sounds good only when the top and windows are up. When I put the windows down and/ or the top down there is a huge loss of sub output level. When I turn the subs up to compensate, it seems like they are easier to overdrive.
I previously had a 15" sub in the storage area in the trunk. It really thumped both ways with the top/windows up or down. I went with the 10s for better sound quality, better transient response, and an overall lighter setup. The 15 was all ghetto boom! Loud and muddy. The guys at ED suggested that I went with beefier 10s. (not really what I wanted to hear)

What do you guys think is going on here. Suggestions please. Thanks

 

I would suggest that the problem is not weird. With the top & windows up the drivers are coupled to the cabin and don't have to work as hard to move air. Your 15 in the trunk was coupled to the trunk and that never changed.

The SQ10 is a pretty small driver. The slimline subs are great for fitment, but they just don't have "******** smashing oontz", as it has become known here. The SQ10 is a single VC driver that is fairly inefficient, it's just not going to produce massive SPL. The ED folks may very well be right that you'll have to step up to something beefier to get the results you want.

 

yep, you lose your cabin gain.

 

Komo and Kale are correct, and there's no reasonable way around this.

 

Usually, you hear the opposite: it gets a lot louder when the windows are down. This is a common complaint usually leveled by drivers of small pick ups, but can apply to owners of small vehicles in general. When this happens, it's usually due to the enclosure being too small for the vehicle. Changing the size of the enclosure shifts the peak repsonse of the system outside of the cancellation mode of the vehicle.

Could it be that the opposite is true in your car? Is the enclosure too big for the vehicle? If this is the case, displace some air in the enclosure and try it. You can do the test by placing solid objects inside the enclosure (like books or blocks of wood). Any change? if so, you've identified the problem.

The problem could also be as simple as the woofer is unloading due to pressure drop in front of the woofer. Subwoofers that do not have careful attention to motor design can start to exhibit non-linear behavior very quickly in these situations. The fix if, this is the problem is to make the air pressure consistant in front of the driver no matter if the windows are open or closed. A downward firing design is the easiest or you can build a "loading board" in front of your current enclosure. This would have to be very solid.

Getting excellent performance consistantly in a vehicle is not as easy as building a box and dropping it in. The key is to match the sonic signature of the vehicle. This requires testing of volume and placement and can be quite challenging if you can map the frequency response beforehand.

One of the advantages of the Stealthbox is JL Audio has already done all of this work before it went into production.

Good luck in your quest for sonic nirvana.

 

Nonsense... in order to create sound pressure, the vehicle needs to be more-or-less sealed. The larger the volume of space sound is filling, the more power is required (like in a convertible or windows-down). Ever hear of Quarter-space, Half-space, etc.? This is why serious SPL competitors go to ridiculous lengths to seal their cars.

Again, nonsense. The box provides all the loading any driver needs, unless we're talking bandpass designs, and then it's a function of the box, not the driver.

Very true, but has exactly nothing to do with this particular problem.

What the HELL does THAT mean? Mapping frequency response??? Sonic signature of the vehicle??? Huh??

 

I think his last point refers to the frequency you get most of your cabin gain at, and trying to work around it.

 

I think more of a case of "just enough knowledge to be dangerous."

 

I resemble that remark!

 

I hope you know I didn't mean you!!

 

Oh, I know. but it's true anyway.

 

Nonsense? I had a problem with my Suburban that was exactly as he stated. Perhaps not for the reasons he stated, however...

I was running six (6) Orion XTR DVC 12's with three Orion 250 HCCA's in a sealed box (individual chambers) mounted directly behind my rear passenger seat. The subs were mounted on the top of the box facing the ceiling/roof of the truck.

Bass in the vehicle was 'okay' with the windows and doors closed... but when you opened my windows and rear glass hatch, the bass was insane! It was much louder with the glass open. Why?

My assumption is that there were problems with wave cancellation. The distance between the sub box and the windshield/rear glass was almost identical. Was the soundwave leaving the subs, reflecting off the glass, and canceling out?

You tell me. All I know is it was loud as hell with the rear hatch glass open.

Mark

 

Yes, it's partially a cancellation issue, and by rolling the window down, you've removed the rear reflector. It has a lot to do with radiation patters (again, half-space, quarter-space, etc.). JLTD's explanation is not applicable to the vast majority of consumer systems. His explanation holds some water when we limit the discussion to SPL competition cars. The subwoofer/box design will (at least they should) include the effects of the second pressure field. Systems designed for absurd SPLs generally do not sound good. This is because when the system is playing at reasonable listening levels, the second pressure field is not part of the equation, and the drivers can become unloaded.

Decibels are a measure of pressure. Pressure can't build up if the environment is lossy. There comes a point where so much pressure is applied to a given lossless (relatively) environment that the environment begins to have an effect on the ability of a driver to move. The environment begins to act as a second enclosure. Sort of a pressure field inside a pressure field. Rolling the windows down releases the second pressure field, and pressure can no longer build up, allowing the drivers to move further.

The problem in your case is a little more complex than in a convertible. In your Suburban, rolling the windows down removed the cancellation at your seat. The system did not actually play any louder than before. In fact, it would have reduced the actual measured SPL with the windows down because of the huge pressure leaks that have been introduced. Because the response curve has been changed so dramatically below 120 Hz with the windows down, your perception is that it became louder. In your Suburban, if you had installed the subwoofers at the rear of the vehicle, you would have had a massive increase in perceived SPL. Probably in the quality of the bass as well.

It is not uncommon for a system to sound louder and measure lower SPL simply because of a modified response curve.

BTW, I loved my Orions back in the day. Pulled 130 dB with a 225 HCCA doing the whole system.