Hi all,
O.K., now here's some outside of the box (no pun intended) thinking for you to ponder. I have a Chevrolet Double Cab Silverado, see here for reference >> https://www.google.com/imgres?imgurl=ht ... jwSC-J2ABA
Basically, it's a 4 door pickup. One of the very Annoying features of most newer cars and trucks is that the cabs are so air tight that when you roll down certain windows at speed you get a very audible low pulsing wind shudder in the cab, to the point it rattles not only your ears but your entire body, much the same you would feel and hear on the very lowest notes of an organ. Today was one of those warmer mornings on my way to work where the question was, should I turn on the AC, or roll down a few windows and enjoy the outdoors? I tried a few different windows down combinations as I drove along and when both back windows are down about half way at speed I get that very audible wind shudder, so I figured I'd do some experimenting as I drove along, but yes I also kept my eyes on the road (hey, at least I wasn't texting!).
One thing I was curious to see was depending on the speed I was traveling if the pitch would go up or down along with the given speed. Sure enough it did! The faster I went the pitch went up, at 70 mph it was a very intense higher pitched shudder, to the point my ears couldn't take it, the pitch being probably around a 32' middle C give or take, the slower I went the pitch went down and at about 40 MPH it was down at what I would estimate to be at or near very near the lowest 32' notes and was more subtle but still with a pretty good shake to things, I figured probably because of the lower frequency and it getting close to dropping off the audible spectrum.
This got me thinking, yes, in subs it's all about air movement, but the general theory also seems to be we will also need a certain sized space for that air to move in or it's going to be very difficult at best to produce these very low notes as is usually the case, even with my 15" sub I still struggle to reach the very lowest notes, but it's in a very small roughly 2' x 2' box. My Chevy pickup seemed to debunk this needing a large space theory to an extent and it got me to thinking about box design as the difference maker where we could duplicate this 'windows down' situation. Could the success of a sub be dependent on not only how air enters the box but also how it also enters or exits the box or a chamber within the box? I know there are ported and folded horn boxes out there of various designs and sizes, I don't know which are better than others but it seems it would be interesting to build a box where there is a driver at the front like a traditional box (this would be the wind speed and force at speed) and have it driven towards another box that would act like a pick up cab with the back windows down. Then the question is since we're really not working with a conventional design so to speak and likely no way to calculate things, how big would the box have to be, would bigger be better, etc., etc? I'm thinking a box with a 15" driver probably wouldn't need to be much larger that say 4' x 4'? Maybe even smaller?
Thoughts, ideas on this crazy one?
Marc
O.K., now here's some outside of the box (no pun intended) thinking for you to ponder. I have a Chevrolet Double Cab Silverado, see here for reference >> https://www.google.com/imgres?imgurl=ht ... jwSC-J2ABA
Basically, it's a 4 door pickup. One of the very Annoying features of most newer cars and trucks is that the cabs are so air tight that when you roll down certain windows at speed you get a very audible low pulsing wind shudder in the cab, to the point it rattles not only your ears but your entire body, much the same you would feel and hear on the very lowest notes of an organ. Today was one of those warmer mornings on my way to work where the question was, should I turn on the AC, or roll down a few windows and enjoy the outdoors? I tried a few different windows down combinations as I drove along and when both back windows are down about half way at speed I get that very audible wind shudder, so I figured I'd do some experimenting as I drove along, but yes I also kept my eyes on the road (hey, at least I wasn't texting!).
One thing I was curious to see was depending on the speed I was traveling if the pitch would go up or down along with the given speed. Sure enough it did! The faster I went the pitch went up, at 70 mph it was a very intense higher pitched shudder, to the point my ears couldn't take it, the pitch being probably around a 32' middle C give or take, the slower I went the pitch went down and at about 40 MPH it was down at what I would estimate to be at or near very near the lowest 32' notes and was more subtle but still with a pretty good shake to things, I figured probably because of the lower frequency and it getting close to dropping off the audible spectrum.
This got me thinking, yes, in subs it's all about air movement, but the general theory also seems to be we will also need a certain sized space for that air to move in or it's going to be very difficult at best to produce these very low notes as is usually the case, even with my 15" sub I still struggle to reach the very lowest notes, but it's in a very small roughly 2' x 2' box. My Chevy pickup seemed to debunk this needing a large space theory to an extent and it got me to thinking about box design as the difference maker where we could duplicate this 'windows down' situation. Could the success of a sub be dependent on not only how air enters the box but also how it also enters or exits the box or a chamber within the box? I know there are ported and folded horn boxes out there of various designs and sizes, I don't know which are better than others but it seems it would be interesting to build a box where there is a driver at the front like a traditional box (this would be the wind speed and force at speed) and have it driven towards another box that would act like a pick up cab with the back windows down. Then the question is since we're really not working with a conventional design so to speak and likely no way to calculate things, how big would the box have to be, would bigger be better, etc., etc? I'm thinking a box with a 15" driver probably wouldn't need to be much larger that say 4' x 4'? Maybe even smaller?
Thoughts, ideas on this crazy one?
Marc