a car is not a sealed enclosure like one might think all have pressure relief vents if they didn't your eardrums would bottom out everytime someone shut a door with all the windows rolled up.
a car and the behaviour of things within it are not a good example of a sealed enclosure.
you are in fact in a helmholtz resonator(not a closed box) ask any experienced autosound installer.
a car and the behaviour of things within it are not a good example of a sealed enclosure.
you are in fact in a helmholtz resonator(not a closed box) ask any experienced autosound installer.
Quite right.
It's called the fan intake. Fan from outside pushes air into the cabin. Some cars have more than one fan.
I know, there are small leaks everywhere.
Ok, let's calculate the helmholtz resonance, put some real numbers in. How large is the car interior? Several hundred liters? What's the cross sectional area of the fan vents? A few square inches? And how long is the fan vent? A few feet long? Throw some realistic numbers into a simulator and you will find that the helmholtz resonance is in the single digit frequencies. And what is a very low tuned port doing when you play much higher frequencies? Not much at all, basically nothing. Most of the thumping notes in music are at 30 hz or higher and won't be affected much at all by any of the small leaks in a car.
Let's also not forget that car fan vents can be closed. You have an option to recirculate the air in the car (closed) or you can constantly draw in new air (open).
Any pressure relief system that remains open is to protect you ears from stuff like doors closing. This is a very low frequency issue, a pressure issue. When you calculate the helmholtz resonance of any small leak for this purpose you will find that it's very low in frequency and basically has no effect on the 30 hz and higher tones.
So effectively the car interior is acoustically sealed when playing regular music with tones 30 hz and higher.
Now you want to talk? I invited you to talk before. Perhaps you could put all your thoughts down in your own words and I'll tell you why you are wrong.
Calculate the helmholtz resonance of the fan system coupled to the car interior and you will see that the fan system is not much of a pressure relief at 30 hz and above. Ported boxes have the highest velocity at undamped resonant frequencies and almost no velocity far above the fundamental resonance. And you can close the fan intake to recirculate the cabin air. So the fan isn't really a factor at all.
Anthony ( just a guy ).
You enjoy arguing way to much for my having any interest in an attempt at a discussion with you.
You are an intelligent fellow. I am happy to say that.
You have a good grasp on some things.
And I do make mistakes in what I type as well.
So continue on having your recreation and enjoy yourself. But don't expect that you will be able to bait me into any type of an argument.
Most of the time our discussions end up being opposite viewpoints of the same coin.
And I have work to do that is actually related to audio. So I leave you to play in your own sandbox.
You enjoy arguing way to much for my having any interest in an attempt at a discussion with you.
You are an intelligent fellow. I am happy to say that.
You have a good grasp on some things.
And I do make mistakes in what I type as well.
So continue on having your recreation and enjoy yourself. But don't expect that you will be able to bait me into any type of an argument.
Most of the time our discussions end up being opposite viewpoints of the same coin.
And I have work to do that is actually related to audio. So I leave you to play in your own sandbox.
Well, thanks for the condescension. I will remind you again that you frequently make all kinds of very long posts and argue endlessly until the point comes that you are proven wrong and then you just stop talking completely.
I don't see it as an argument anyway, it's just a discussion. And I certainly don't argue for fun, I discuss to provide emphasis for the right answers.
You can't come into a thread and say that all the standard beliefs are wrong, not give any indication of how or why they are wrong, post your resume and experience (AGAIN) as the only argument and leave it at that. Especially when the standard beliefs were derived empirically and scientifically, the effects can be simulated, and they are not wrong.
I don't see it as an argument anyway, it's just a discussion. And I certainly don't argue for fun, I discuss to provide emphasis for the right answers.
You can't come into a thread and say that all the standard beliefs are wrong, not give any indication of how or why they are wrong, post your resume and experience (AGAIN) as the only argument and leave it at that. Especially when the standard beliefs were derived empirically and scientifically, the effects can be simulated, and they are not wrong.
I guess I'll get in here before the lock.
I've pretty much lost track of what the "discussion" is about at this point. What is the real point you guys want to make?
I think even a small car interior is probably over 1000 liters. So, unless you have subs with an enormous Vas or you are using an extreme number of subs, I would expect it to most closely match the inside of an infinite baffle enclosure.
Obviously you guys have history but, again, what is it we're trying to prove here? Whether or not stuffing a subwoofer enclosure has a benefit?
-Chris
I've pretty much lost track of what the "discussion" is about at this point. What is the real point you guys want to make?
I think even a small car interior is probably over 1000 liters. So, unless you have subs with an enormous Vas or you are using an extreme number of subs, I would expect it to most closely match the inside of an infinite baffle enclosure.
Obviously you guys have history but, again, what is it we're trying to prove here? Whether or not stuffing a subwoofer enclosure has a benefit?
-Chris
This sidetrack was about whether or not air moves around in a sealed enclosure, and it clearly does. Not that it matters, since the particles of tiny glass that will move about won't hurt anything, even if they get in the coil gap they aren't big enough to do anything, and they can't escape to the outside air in a sealed box so there's no health issue either.
Stuffing a subwoofer can have benefits but it's not always necessary. if you have higher frequency ripple to sort out then it can be a benefit. If it's a sealed box and you want a lower box q then it can be a benefit. If you don't need either of those things then it's not necessary.
Sub #2 is up and running as of 20 minutes ago. Same type and amount of stuffing as the first, running stereo and crossed over at 90 Hz.
My highly calibrated measurement ears are telling me they sound pretty good, even being poorly positioned as shown below. I'll run a sweep with REW this evening and see what I've really got but right now I'm enjoying some Morphine - Cure for Pain.
-Chris
Even the dog likes it. He's old but his ears are probably still better than mine.
My highly calibrated measurement ears are telling me they sound pretty good, even being poorly positioned as shown below. I'll run a sweep with REW this evening and see what I've really got but right now I'm enjoying some Morphine - Cure for Pain.
-Chris
Even the dog likes it. He's old but his ears are probably still better than mine.
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From an 'ol hillbilly that has built quite a few portable Bluetooth units..
I've used cotton batting, cotton cloth, poly fill of all types, bubble wrap of different varieties, foam bed mattress covers, Styrofoam beads and pieces of Styrofoam sheets, underinflated vinyl balls, tennis balls, Depends adult diapers, Maxi pads, course sawdust in cloth bags, wool blanket, ect.. ect.. Anything that I could think of to absorb sound to put inside of a sealed enclosure..
Pink Panther fiberglass wins hands down and don't be shy with the amount used. I don't have any fancy test equipment but my ears don't lie..
Take it for what it's worth..
I've used cotton batting, cotton cloth, poly fill of all types, bubble wrap of different varieties, foam bed mattress covers, Styrofoam beads and pieces of Styrofoam sheets, underinflated vinyl balls, tennis balls, Depends adult diapers, Maxi pads, course sawdust in cloth bags, wool blanket, ect.. ect.. Anything that I could think of to absorb sound to put inside of a sealed enclosure..
Pink Panther fiberglass wins hands down and don't be shy with the amount used. I don't have any fancy test equipment but my ears don't lie..
Take it for what it's worth..
I moved the subs around in my room quite a bit last night and measured at least 20 frequency sweeps from my listening position. I didn't find anything better than both subs sitting right there in between the mains but pulled about a foot out from the wall. I kinda had a hunch that would be the case after listening but wanted to try some other positions.
Below in green is the response from the two subs together, with the amp for my mains turned off. The red line is where I ended up after 30 minutes of playing with the PEQ in JRiver. I can flatten it more but I'm satisfied until I get my mid-bass modules built.
-Chris
Below in green is the response from the two subs together, with the amp for my mains turned off. The red line is where I ended up after 30 minutes of playing with the PEQ in JRiver. I can flatten it more but I'm satisfied until I get my mid-bass modules built.
-Chris
Yes, nice curve. But it is flat to the eye and dull to the ear. Good sub-woofer sound requires rising slope with lowering frequency, not ruler flat.
Where did people ever get the notion that a flat FR sounds right and you should design to achieve that?
Ben
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I understand that our ears are more and less sensitive to different frequency ranges.
https://en.wikipedia.org/wiki/Equal-loudness_contour
But that has little to do with smoothing peaks and valleys which are each only a portion of an octave.
I think what you're talking about is a house curve, which I may do to some degree, but not right now, and probably not very much in the sub-bass. Personally, I think the house curve to match our hearing is misunderstood and somewhat overrated.
The problem I have with a sub bass curve matching our hearing sensitivity is that many recordings are mixed by someone with ears having the same general frequency response as any other human, so the bass is boosted down there already. So, basically, music that already has nice deep bass with a flat setup becomes unlistenable if my curve also ramps up sharply as frequency goes down. And it's not limited to any specific genre.
I tune with frequency sweeps at a constant DB level. But the music I listen to is nothing like that.
In my car I have a little panel, mounted next to the gear shift, where I can change the subwoofer level song by song with one knob and add bass boost curve with another knob. I hardly ever touch the bass boost, which is probably more accurate than changing sub output overall. But I use the sub adjustment knob all the time.
As far as sub bass at home goes I don't know of a better overall solution, for music, than tuning pretty flat.
I can assure you these subs do not sound remotely "dull to the ear" as they are set right now. Unless the recording itself is dull down there.
So that's where I got the idea that a pretty flat response curve can be the best compromise.
-Chris
Sure, a matter of taste and depends on your sources.
But I would just mention:
1. discussions on this board lead me to think most people end up with rising bass and there are reasons besides F-M loudness for it (for example, the absence of low freq reverb at home compared to a concert hall sucks a lot of bass-experience out of music at home, even if FR curves are flat..... have you ever thought about that?)
2. I thought it was a matter of pride to have a system that you never have to twiddle the knobs to have things sound right all the time. If your system is otherwise, might be time to question your sources, system, or taste.
Ben
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I think both Ben and Chris are on the same page, just different sides.
Some recordings do beg for a little lift, and others are well endowed in the low end.
It is a function many times of the choices of the recording engineer. Microphone choices, playback monitors available and such.
I am friends with a few recording engineers and it is very interesting listening to them discuss the various choices made versus what would be a considered a totally accurate recording.
Some recordings do beg for a little lift, and others are well endowed in the low end.
It is a function many times of the choices of the recording engineer. Microphone choices, playback monitors available and such.
I am friends with a few recording engineers and it is very interesting listening to them discuss the various choices made versus what would be a considered a totally accurate recording.
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