Joined
·
3 Posts
Hello diyma!
I've been doing research on cabin gain in vehicles and there seems to be all sorts of different information on the effects of the volume levels of certain frequencies in smaller spaces where the wavelength of the frequency is longer than the space it is occupying. Apologies if I am confusing the concept of cabin gain and something else, as it's a little tricky to understand.
I am on this journey because I'm looking to downsize my vehicle's subs to something a little more practical in terms of space, and upgrade in terms of the sound. I currently have 2-12" subs in a sealed box with 1.25 cubes per chamber, and it's just a bit too much sub for what I need nowadays. They also, unfortunately, are high qtc drivers, so they are very peaky across their range require a lot of EQ to get the flat, deep response I really like. I'm replacing these two subs with a single 10" Alpine X-W10D4 woofer.
I really love deep bass ~30hz, and I wanted something that sounded nice and even in output as I swept between ~80 down ~27hz. I initially went in modeling a box in WinISD that would give me the flattest response from the woofer within that range, and ended up with this design in a ported box.
![Rectangle Slope Font Parallel Screenshot]()
Now, this was great to me! It's tuned to 27.1 hz, has an extremely flat response with a -3db point at ~24.5hz, and I'd save space over my 2 12" subs and have a killer flat response that can get as deep as I need it to without rolling off early and thus saving me from requiring lots of eq! However, what I didn't take into account was the cabin gain. From what I have read on DIYMA posts, cabin gain is easily calculated for a sealed enclosure using linkwitz transform in WinISD, BUT! It apparently doesn't work the same for a ported enclosure. At least, according to this DIYMA post, a ported enclosure is a dipole, which in their example, doesn't add any cabin gain at 30hz, unlike a monopole which will add 12 db at 30hz. Now, I might just be confused and reading this wrong, but based on that post, there won't be any cabin gain from a ported enclosure.
But based on my research, a ported box != a dipole and they are two different designs. Also, according to SVS, both types of enclosures experience room gain. Their sealed subs roll off at 32-35hz to take advantage of the average room gain in a home to create a flat response. Their ported subs, however, do not have a frequency roll off like this, and remain fairly flat until ~20hz or less in a quasi-anechoic environment, but in a smaller room, they experience room gain, so to combat this and prevent uneven peaky sound from their ported enclosures, they include room-gain compensation controls to flatten out the sound.
So, I modeled the sub in a sealed enclosure and with approximate measurements of the longest path inside my SUV, I included a cabin gain simulation using linkwitz transform to see how my frequency response would be for BOTH ported and sealed enclosures.
![Slope Rectangle Plot Font Line]()
Oh no! In both ported and sealed examples, assuming cabin gain for both, I've got a less-than ideal curve for the outputs! It seems that in both cases, cabin gain will cause the lowest frequencies to dominate the higher ones! It seems cabin gain might make my flat responding ported sub to sound much more progressively louder as it gets deeper. But so does the sealed box.
The Color Key for the curves is
Black - Ported (no cabin gain)
Orange - Ported with cabin gain
Green - Sealed (no cabin gain)
Blue - Sealed with cabin gain
You may ask why I originally modeled a ported enclosure vs just going with a sealed enclosure. My main reasons for doing so were the calculated flat response down to 30hz (prior to this journey into understanding cabin gain), the fun in the hobby of designing and building the enclosure (I'm excited to build something with more complexity!), the increase in output vs sealed (I'm concerned with the loss in output going from 2 12's to a single 10), power requirements (lower for the same output), and less potential for excursion related distortion at lower listening levels (less required excursion to achieve similar output).
I think I might be misunderstanding how cabin gain affects ported enclosures, and where I think I might be misunderstanding is the whole dipole argument. Is it just acting as a dipole BELOW the tuning frequency of the port, where the sub would essentially be acting as if it's in free-air? Also, with the frequency response of human hearing being less at the deepest frequencies, would a bump in the volume levels in both sealed and ported from cabin gain result in a peak sound at sub 40 hz, or to my ears, even with the higher db levels, would sound "flat" due to the decreased sensitivity our ears have at those frequencies? This is assuming that cabin gain also affects ported enclosures. Are my concerns overblown?
Thanks all for any help! Searching through this forum has been helpful but I still am confused a bit! Cheers!
I've been doing research on cabin gain in vehicles and there seems to be all sorts of different information on the effects of the volume levels of certain frequencies in smaller spaces where the wavelength of the frequency is longer than the space it is occupying. Apologies if I am confusing the concept of cabin gain and something else, as it's a little tricky to understand.
I am on this journey because I'm looking to downsize my vehicle's subs to something a little more practical in terms of space, and upgrade in terms of the sound. I currently have 2-12" subs in a sealed box with 1.25 cubes per chamber, and it's just a bit too much sub for what I need nowadays. They also, unfortunately, are high qtc drivers, so they are very peaky across their range require a lot of EQ to get the flat, deep response I really like. I'm replacing these two subs with a single 10" Alpine X-W10D4 woofer.
I really love deep bass ~30hz, and I wanted something that sounded nice and even in output as I swept between ~80 down ~27hz. I initially went in modeling a box in WinISD that would give me the flattest response from the woofer within that range, and ended up with this design in a ported box.
Now, this was great to me! It's tuned to 27.1 hz, has an extremely flat response with a -3db point at ~24.5hz, and I'd save space over my 2 12" subs and have a killer flat response that can get as deep as I need it to without rolling off early and thus saving me from requiring lots of eq! However, what I didn't take into account was the cabin gain. From what I have read on DIYMA posts, cabin gain is easily calculated for a sealed enclosure using linkwitz transform in WinISD, BUT! It apparently doesn't work the same for a ported enclosure. At least, according to this DIYMA post, a ported enclosure is a dipole, which in their example, doesn't add any cabin gain at 30hz, unlike a monopole which will add 12 db at 30hz. Now, I might just be confused and reading this wrong, but based on that post, there won't be any cabin gain from a ported enclosure.
But based on my research, a ported box != a dipole and they are two different designs. Also, according to SVS, both types of enclosures experience room gain. Their sealed subs roll off at 32-35hz to take advantage of the average room gain in a home to create a flat response. Their ported subs, however, do not have a frequency roll off like this, and remain fairly flat until ~20hz or less in a quasi-anechoic environment, but in a smaller room, they experience room gain, so to combat this and prevent uneven peaky sound from their ported enclosures, they include room-gain compensation controls to flatten out the sound.
So, I modeled the sub in a sealed enclosure and with approximate measurements of the longest path inside my SUV, I included a cabin gain simulation using linkwitz transform to see how my frequency response would be for BOTH ported and sealed enclosures.
Oh no! In both ported and sealed examples, assuming cabin gain for both, I've got a less-than ideal curve for the outputs! It seems that in both cases, cabin gain will cause the lowest frequencies to dominate the higher ones! It seems cabin gain might make my flat responding ported sub to sound much more progressively louder as it gets deeper. But so does the sealed box.
The Color Key for the curves is
Black - Ported (no cabin gain)
Orange - Ported with cabin gain
Green - Sealed (no cabin gain)
Blue - Sealed with cabin gain
You may ask why I originally modeled a ported enclosure vs just going with a sealed enclosure. My main reasons for doing so were the calculated flat response down to 30hz (prior to this journey into understanding cabin gain), the fun in the hobby of designing and building the enclosure (I'm excited to build something with more complexity!), the increase in output vs sealed (I'm concerned with the loss in output going from 2 12's to a single 10), power requirements (lower for the same output), and less potential for excursion related distortion at lower listening levels (less required excursion to achieve similar output).
I think I might be misunderstanding how cabin gain affects ported enclosures, and where I think I might be misunderstanding is the whole dipole argument. Is it just acting as a dipole BELOW the tuning frequency of the port, where the sub would essentially be acting as if it's in free-air? Also, with the frequency response of human hearing being less at the deepest frequencies, would a bump in the volume levels in both sealed and ported from cabin gain result in a peak sound at sub 40 hz, or to my ears, even with the higher db levels, would sound "flat" due to the decreased sensitivity our ears have at those frequencies? This is assuming that cabin gain also affects ported enclosures. Are my concerns overblown?
Thanks all for any help! Searching through this forum has been helpful but I still am confused a bit! Cheers!
