Free Bass! Subwoofer Room/Cabin Gain: What it is and how to model it with WinISD

[@ErinsAudioCorner]

I was asked the following on DIYMA so I will answer it here: Q: TWO questions for you-- Why do you take the sub response all the way down to 1 hz when inputting the LR transform function in winsd? Would the gain approximation curve change if you used 20hz instead of 1 ?? A: Twenty is just the default for an LT. An LT is an enclosure type which uses DSP to extend the extension to a frequency lower than it would otherwise give in a small enclosure. I imagine the default is simply to keep someone from crushing a subwoofer (you need power and a lot of excursion to get down this low as it is). We are just using the same principle to model cabin gain and in this case, cabin gain won't just stop at 20Hz. It will extend all the way down in frequency.

[@Nordgrinder]

Thank you, Erin! I've been modeling woofers and subs with WinISD for a couple years now, and had heard that cabin/room gain can also be modeled. Now I can grab a tape measure and give that a try as well. Love your channel and your laidback, no nonsense approach to sharing the product of all your hard work and passion.

[@ErinsAudioCorner]

Thanks! Glad it was helpful!

[@Nordgrinder]

@@ErinsAudioCorner I was wondering if you were going to to post this video at CAJ. Must have read my mind. :-)

[@umtbozkr2358]

Respect, your knowledge and the way you explain important issues in audio deserves respect!

[@ErinsAudioCorner]

I appreciate that!

[@7Logik]

Amazing you mentioned a 13w7 that is exactly the reason I watched this video that showed up randomly in my feed 😅. I was always curious about room gain as a kid becuase I knew bass was always stringer in my bedroom, in the corner opposite of my subs . Thank you for this enlightening in depth discussion. I now understand I may not even need to tune my 13w7 down to 25 hz now for my suv. As one who like loud, clean and low understanding this better noe and being able to model it in winisd is a game changer . Bravo , great work . I wish you well on your channel

[@mikewaters6980]

Very interesting and useful. Thanks for taking the time to teach us Erin. Was hoping so see you put a huge boulder rock in the bowl to represent low frequency… but sure… the ball was good too!

[@marianodamiandavalosguille7711]

It is a great compliment, to see the great effort that you develop with each video explaining in a timely manner, I just discovered your channel and I am fascinated with the videos, and I congratulate you for such effort ... I know that in the description you mention that it is not a tutorial on how to handle the WinisD, but I would like you to guide me on how other graphs are modified or altered as the gain is applied in the cabin, since I have carried out tests and simulated some drawers and I observe a large increase in the cone excursion when applying profit in the booth, your comment would be of great help to me ...

[@Cfybb-w7f]

Great video ! I'm doing a car system . What then is the benefit of vented enclosure if cabin gain from the car ( vw jetta in trunk) does even better job of extending low end? I want to use 4x 8 inch subs . Some of these only require sealed cabinets of .3 ft3 . I do my own building . A sealed box is a lot less work and for small subs nearly all ported cabinets I've seen require more space when you consider the port . I'm getting back into this after many years away from installing car audio . I've made ported cabinets in the past that work great . It looks like sealed enclosure will work just as well . I listen to rock so my goal is not to shake the car to pieces! Is my logic correct ? I see vented cabinets for sale all the time , more common than sealed so am I missing something?

[@michaelwhisman2479]

Thank you for doing this video. I have been learning about how to use this program and this topic seems to be one that is talked about as a feature yet never explained in how to use it. it is interesting how much the excursion changes due to the Linkwitz Transform filter being active. I have been working out a new box for my friend's car sub and have wanted to know this since it seems to explain why the sub in its cheap prefab box seems to be working harder than it should. I'm curious though. If you open a window an inch or two, does the size of the window opening affect the Linkwitz Transform a lot? Or would it maybe be better to do a 4th order bandpass for sealed and 6th order bandpass for ported using the window opening as the port dimensions with the internal volume of the cabin as the front volume and tuning the port Hz to make the port length only an inch or two?

[@tyler4051]

I honestly think that was a very good way of explaining it.

[@mkshffr4936]

Thank you for this useful presentation. I am not into car or theater but rather home audio. A question, if I have a room of say 12'x14' but with a couple open doorways to other rooms would I still calculate the turnover frequency based on the shortest dimension of the listening room but figure on a more shallow gain slope? If so a transmission line enclosure might be a good choice as they can be tuned for something approaching a 1st order roll off. For me the ideal total response is flat to 16Hz (low C on the 32' pedal stops) and the settle for is 32Hz which covers the 16s. My current design project is a high efficiency 3 way system of around 95-100dB/w/m. Several 15" woofers look like good candidates in sealed or TL enclosures.

[@It-b-Blair]

Oh glorious! My spl went from 128db@23hz to 150db@23hz 🤤 thanks man! My Silverado crew is gonna be a beast 😸 Edit: wait… I took out my rear seats and my box will take that up… with 2- 18” subs in a 22Wx35Hx45L box… should I model from the box to dash? I’m planning on having an 8” gap between the subs and they’ll be on a 30degree angle, like 1’cube ears on a 22x22x45 box because recommended ported vol is 10’cube , so I can still use my rear view, thus there’s still that length from windshield to back glass… in theory… 🤪 man, trying to hash this out with WinISD and the12volt volume calculations is super abstract…. Think I’m starting to grasp the box after a few days of number play 😂😂

[@captanspace]

My living room isn't closed, it has an access to my kitchen. Do I still have the room gain? Should I consider the distance from the living room wall to the kitchen wall or to the other living room wall?

[@mcjonner]

Do you factor room/cabin gain into boxdesign? Would you Stull build the same size box for a sub for a trunk / hatch back and save? A 10x12' room vs large open floor plan living room or can you customize it

[@ErinsAudioCorner]

Do I? Sometimes. Mostly for car audio it can be helpful so you don't lose a ton of space when you don't need to. In a home, space isn't as much of a premium so you can "overbuild" and just cut whatever bass you don't need. That said, it really is important to understand your room/car and the best way to do this is to use an existing enclosure/subwoofer, measure it outdoors far away from any building, then measure it in the car. The difference is your transfer function; that is what your room/car is doing.

[@mcjonner]

@@ErinsAudioCorner thanks for the reply. I was curious cause I was thinking of building 2 large ported enclosures to use as end tables and wasn't sure how much I could manipulate the size and if factoring in room gain could help, but the room gain would work against my favor if it's too large of a space like open floor plan living room, ideally the boxes would need to get bigger.. ah well

[@erics.6275]

Do you have to measure the entire lenght of the vehicle, (bumper to bumper)? Or from subwoofer to listening area, (trunk to cabin)? Also, if the subwoofer is on thr trunk, does it matter if the trunk is sealed off to the cabin? If so, how can me model these changes?

[@ErinsAudioCorner]

Length of the vehicle. Doesn't matter if the trunk is sealed or not because I doubt the trunk is really 100% sealed. Plus, bass waves can travel through the baffle. For example, I ran IB for years. Had a null around 60Hz from the subwoofer's "reflecting" off the trunk lid. If the cabin were sealed off from bass in the trunk that would not happen. At least, that's my thoughts on it. I could be wrong. :)

[@davidtashman8217]

@@ErinsAudioCorner When you say the length of the vehicle, do you mean the entire vehicle or just the cabin/trunk area?

[@kavneetram6582]

Hi @Erin Audio corner Thank you explain throughly ,i was hoping if you can also do a review wharfedale sw-15 subwoofer.

[@ErinsAudioCorner]

It's not on the radar but I can't say it won't ever happen.

[@colbylaro9361]

Erin your timing is impeccable! Thank you for risking your life! All us married guys can surely relate to how serious these things are. This information is what I've been searching for. Cant tell you how I appreciate it. I have a 4 door titan which is obviously longer than a single cab. I built a ported under seat box and tried different port lengths and no matter what I do I keep getting a spike at 50hz. And its 15db louder! Is this just the natural gain of the cabin or am I just doing it all wrong? I can eq it in my dsp but it's just too loud and no where near what I need out of that sub box. My goal was to build a box that would play anywhere from 10 to 60 or 80hz because I intend to install front subs for the higher frequencies. (Building a so called multimedia setup that I can watch movies or videos on my 10.1 inch screen). Obviously I'm doing it on a low budget so I've been wondering if I have to bite the bullet and get better subs? Thanks for these videos, guess I better learn how to model..ugh

[@ErinsAudioCorner]

The cabin gain is more of a slope in response. A spike (or dip) would be a modal issue (resonance). Most likely, at least. If you have a Dayton Woofer Tester then you can run a quick impedance sweep to make sure the enclosure is not the issue itself. But most likely it is the cabin. I would recommend using the DSP with a high-Q value (appropriately matched to the resonance spike) to tame it because without building a Helmholtz absorber or huge bass trap (which are impractical in a car) you really have no other options short of moving the enclosure and finding a better location, which likely isn't practical either.

[@colbylaro9361]

@@ErinsAudioCorner thanks again, loving your content, thanks for helping the laymen 👍

[@ErinsAudioCorner]

@@colbylaro9361 you got it, dude.

[@CoreMaster111]

So according to this I should get great low end performance out of my sealed sub. But in reality I barely hear or feel 20hz, 30 hz is quiet and at 40hz is where it starts playing decently. Which is pretty much in line with frequency response/ SPL numbers in WinISD without your cabin gain approximation. Vented box in the other hand seems to gain some at low end.

[@ErinsAudioCorner]

Too many variables to draw such a generic conclusion from a video.

[@TyGuyPS5]

So my SVS sub has a room gain compensation. But I cant really find out what that actually is doing. My room gain is 40hz. When I activate it, the output goes up about 3db. But I dont have REW to actually measure across the board, just using my phone. What does activating this do?

[@HiFiNi-TheDigitalScientist]

Hey very interesting video 🤓 I tried the same process for a triple 12" JL shallow mount enclosure with 3 x 12TW3-D4 and the cone excursion went from 15.2mm to 220mm 👀 Any ideas on what's caused that 🤔

[@ErinsAudioCorner]

The sim is likely just telling you that - mechanically - in order to achieve what room gain would do it would need that much excursion. Though, I agree that does seem nuts.

[@sherm6644]

@@ErinsAudioCorner my intuition is that with the transformation applied the excursion graph is null, is that true? without the filter i am within tmax, so within my car it will be within tmax also?

[@TylerStout]

How does this work with open concept rooms? For example my room is 18x13 roughly but one of the corners is open to the rest of my house and is probably 40-50ft distance in that corner to the next wall.

[@ErinsAudioCorner]

Well, if the opening is large enough then the space is effectively "infinite" and there would be no cabin gain... *I think*.

[@TylerStout]

@@ErinsAudioCorner Wouldn't surprise me based on my measurements. My subs drop off like a rock after their rated frequency response. Thanks for the reply.

[@FOH3663]

@@ErinsAudioCorner Although I don't believe I've seen it, I believe it can be modeled as a coupled acoustic space with the opening being the acoustic aperture. The room would likely reciciprocate with some Vessel Gain based upon it's 18'x13' volume. However, the opening to the larger area certainly diminishes the magnitude and onset frequency of the Vessel Gain. So it really depends upon how acoustically large the aperture is. It'd be fascinating to measure this because modeling the behavior of the two coupled spaces would merely be a simple approximation with accurate boundary wall impedances, rigidity/damping.

[@robcohen]

Does corner loading help below the room gain transition frequency?

[@valorantorion1588]

So if I have a ford ranger right the longest amount of room I have would be diagonally from front right to back left its only like 7 feet give or take so that would be 14hz that doesn't sound right but it could be idk

[@FMATTV1986]

My back porch is 12feet long 6 feet wide and 10 High concrete. But on 1 of the 12feet sides is the open Savannah so it's only 3 walls. How do I calculate the gain for this?

[@FSXgta]

you only get room gain in rooms/cabins, this is probably too open

[@FMATTV1986]

@@FSXgta thought so. The bass sucks. Due to the opening. I have 4 12s and barely hear the frequencies below 40hz

[@shanecabbage2187]

Absolutely love it. Thanks for the new info

[@shawnsanderson3695]

Then it makes sense that the low hertz sound better with the window down mabey?

[@Lordxfx]

Such a fun channel. Subbed.

[@OriginalWis]

Nice man thank you so much for this video!

[@bassxtcy]

12dB/octave in a room seems a bit much doesn’t it?

[@ErinsAudioCorner]

If it is airtight, maybe not. Most rooms are not. But in car audio, this generally holds true (other than the pressure vents typically located in the trunk area). It could be too aggressive. It might not be aggressive enough. That’s why I stressed that the gain calculation is just an attempt at providing an estimation of what the LF does in a real room. To know the exact transfer function of your room would require actual testing of a subwoofer outside the room vs inside.

[@bassxtcy]

I measured the cabin gain in my Corvette C6 and got about 12dB/octave.

[@audfrknaveen2256]

Hi ... after adding room gain and parametric EQ filters in winisd. Both for sealed and ported simulations. Cone excurtion is way too beyond the Xmax.

[@ErinsAudioCorner]

I mentioned this in this video but the room gain is simulated using a linkwitz transform which is a form of low frequency EQ. Remember, this is just a simulation. So that portion of excursion won’t exist in the real world.

[@mkshffr4936]

So you plot max SPL v.s. frequency using just the predicted response without room gain. Then at the frequency of interest you add the room gain to that figure to get the actual effective SPL.

[@deanedgx]

great info. thanx.

[@ErinsAudioCorner]

You're welcome!

[@pliedtka]

Ussually for conventional sub box I t like them sealed, smooth bass without hump.

[@johnviera3884]

With this technique applied in my car, cabin gain lands around 56Hz. Sounds accurate because my subwoofer response dips at 56 Hz and above. But why does the graph show me flat out to 20Hz, and my 15” subwoofer in a sealed box starts dipping bad around 34Hz?

[@ErinsAudioCorner]

Resonances, likely. A hard null can make the response look like it’s falling off.

[@johnviera3884]

@@ErinsAudioCorner thank you for the response. Great video. I’m going to set up a microphone with REW also.

[@johnviera3884]

With a sealed 15” subwoofer, My in car response is like a poorly designed band pass. 35-50Hz.

[@johnviera3884]

Why do you multiply the side by 2?

[@Rene_Christensen]

You will only get a flat response for a sealed woofer below its resonance frequency, where it will deliver volume displacement instead of volume acceleration. We are also assuming a perfectly sealed room. If you have a port, then at low frequencies you will just short the front and the rear side of the woofer driver, so you will not get the flat response.

[@noncog1]

I dont understand this comment. Is it implying that cabin gain works differently for ported. Is there a better q than .707 to use to assume losses from cabin flex and leak?

[@Rene_Christensen]

@@noncog1 It sure does work differently. The first room mode is at zero hertz so it will be excited no matter where you place the speaker. But the speaker needs to be sealed for this too work at very low frequencies. If there is a port, at low frequencies the front pressure is cancelled out by the rear pressure through the port. The ported speaker at very low frequencies acts as dipole and has no net volume displacement. A dipole cannot excite the lowest mode, only a monopole like a sealed speaker can.

[@bpintogsxr1000]

Thanks man. Appreciate the info 👍🏻

[@tyler4051]

Thanks for the help!

[@deegermild8340]

thank you erin

[@shawnsanderson3695]

Super cool man thanks.

[@magnusnielsen2648]

thanx!

[@ErinsAudioCorner]

No worries!

[@akjohnny5997]

this is really cool, but how do we know that this even remotely resembles the real world? has anyone ever tested or verified it? i get that it's just a 'simulation' but is it even close?

[@angelvip2474]

Awesome videos

[@ErinsAudioCorner]

Thanks!

[@stevenbrown4534]

Was just trying to figure out my truck subs. This helped a ton. Thanks!

[@ErinsAudioCorner]

Glad to hear it!

[@BarrySchanz]

Thank you

[@ErinsAudioCorner]

Welcome!

[@EvAnA876]

If your enclosure size is not the same as the recommended size from winISD do you need to be putting in different numbers for the linkwitz transform?

[@ErinsAudioCorner]

The LT is just to model cabin gain. The enclosure is separate from this. So you can imagine them as two different models combined to give you an idea of the in-room response. If I understand your question.

[@EvAnA876]

@@ErinsAudioCorner I think I got it. I just meant if the ensloure size was slightly off would you try to match actual enclosure Q setting with the filter to get the best guesstimation

[@adrianegowski5012]

Heh.... For Polish it is not so easy to follow "feets" instead of meters ;-)

[@ErinsAudioCorner]

Yea, but you guys are doing it wrong. LOL. I kid. I kid. Truth is the overwhelming majority of my viewers are from the US. Well in to the 90-th percentile. Besides, google will convert for ya'. Speed of sound is ~343 m/s (standard conditions). :)

[@pliedtka]

One foot 0.305m. But the formula is still the same ~340m/s 2xthe dimension in meters. f=v/2d Kumasz czacze

[@single_cam9199]

Vid on putting the woofer in the field then in the cabin I have all smd measuring devices

[@VioletGiraffe]

I know cabin gain is very important in car subwoofer calculations, and I wonder this: aren't the car subwoofer speakers designed differently from home/studio subwoofer speakers? In theory, the car subwoofer should have a rolled-off frequency response towards DC, and the home subwoofer should not.

[@ErinsAudioCorner]

Some might be. But certainly not all.

[@gerritgovaerts8443]

As a side note : I don't know about cardioid bass , but I am pretty sure that dipole bass does not benefit from room gain (there is no total net presssure change). On top of that , dipole bass in a room cannot go lower than the frequency that has a wavelength that is twice the longest dimensions in your room : want to go down to 20 Hz , make sure that the longest side of the room is 8.5 m

[@It-b-Blair]

What about 1/4 length resonance?