The flame technology tends to not leave much in the way of walls. If you breath or listen through a piece it is almost as if it wasn't there. If you have trouble breathing through it then its not true open-celled foam.
As to the manufacturers claims and the available products, I can't speak. I only know the foam directly from the manufacturer and there it comes in an enormous array of pore sizes and cell characteristics. I would seriuosly doubt that any foam has much absorption at 50 Hz. I've seen the claims, I have my doubts.
Porous absorbers "work" at every frequency. The problem is:
- can you place a porous absorber at the correct location where velocity is highest (at boundaries velocity is 0)
- can you make it thick enough without making it too reflective (waves need to be able to penetrate the whole absorber)
Talking about room treatment, a lot of absorbers like this will certainly have some effect:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Best, Markus
But is it applicable for frequencies under the lowest mode of a room?
Because that is basically the situation we have in a subwoofer, where wavelength are much larger than any dimension of the box and the box is pressurized.
Can we talk about velocity zones in a box used under its "0" mode (typical subwoofer)? I thought it was only pressure.
Look, guys, box stuffing is NOT an exact science. 
If your building a DIY speaker system, you have the luxury of fine tuning the stuffing to suit your listening and/or measuring tastes. It CAN be an iterative process simply because all you have to do is remove the woofer and re-do the type or arrangement of the stuffing. This can be accomplished by using a closed foam sealing strip around the woofer frame against the cabinet.
Or, am i totally missing something here?😱 So why all the detail questions?
Can anybody show some test data that illustrates the standing wave problem in subwoofers?
If your building a DIY speaker system, you have the luxury of fine tuning the stuffing to suit your listening and/or measuring tastes. It CAN be an iterative process simply because all you have to do is remove the woofer and re-do the type or arrangement of the stuffing. This can be accomplished by using a closed foam sealing strip around the woofer frame against the cabinet.
Or, am i totally missing something here?😱 So why all the detail questions?
Can anybody show some test data that illustrates the standing wave problem in subwoofers?
Did you read my post? The first mode for a really huge 1000l box is at 170 Hz. For smaller enclosure sizes the first mode is even higher. The typical application for a subwoofer is 20-80 Hz.
Best, Markus
Really would love to hear some arguments. Or is this the kind of “common knowledge” described in DIY-AV • View topic - About Trolling
Best, Markus
If you're referring Post #145, you seem to be quoting theoretical calculated values based on the box geometry. Have you built the box with the driver, xover and stuffing and actually measured a problem at these frequencies??
If it's truly a sub, then it should only operate at <60 hz or at the most <=100 hz. After that a properly functioning xover like those used in powered subs with high cut off rates will mitigate signals above those crossover frequencies, thus mitigating any theoretical modes at those higher frequencies. So, to me at least, the whole discussion about standing waves in subs appears quite moot.
My prior post was intended to challenge those who seem overly concerned about internal cabinet reflections. Where's the test data? I don't even recall any anecdotal comments on actual listening experiences.
First, if I were going to modify the room to that extent I would just re-built it and do it right - damped walls etc. Next, the tiny main loudspeakers, are a joke, and no comprable center channel. This guy will of course tell you that he can't use bigger speakers because of WAF - I'm sure his wife loves all those lovely panels all over the place. Next, there should not be any absorption behind the listener, only behind the loudspeakers (lots of that)and the ceiling between the loudspeakers and the listener. With decent speakers you don't need to worry about wall reflections.
The owner of that room is probably very proud of it, but I pretty sure that I would be completely unimpressed with either the video - too small - and/or the audio - an obvious problem there. His money was spent in all the worng places.
skeptic43
I think we're both on the same page. But nevertheless the "theoretical calculated values" for the first mode are always quite exact even if the room (or enclosure) shape is irregular. The point was to show that for a subwoofer the first mode is way above the application. So why bother?
Best, Markus
I think we're both on the same page. But nevertheless the "theoretical calculated values" for the first mode are always quite exact even if the room (or enclosure) shape is irregular. The point was to show that for a subwoofer the first mode is way above the application. So why bother?
Best, Markus
Ah already off to good start by invoking trolling. It's not a common belief as far as I can tell. I think I am in the happy minority that doesn't think room treatment does anything except mess with the sound a little and probably makes the room a lot less efficient.
I don't agree with everything Mr. Geddes says. I think the smaller you can make a speaker the better, of course this is only in theory and maybe in reality his room might need a little more power. It looks like he does have a matched center channel to me but all of the channels are misaligned with the screen - they are below the screen. I actually prefer his surround speaker layout but one of the channels has a huge early reflection or more accurately it's being blocked by the couch. He should maybe move them up higher and face them down somehow.
The thing with rooms and treatment is that even with all those panels he has in his room I could still probably count up to a thousand or more unmitigated reflections. And even if he did treat all of them I think the net result is to make you have to turn your amps up louder wasting energy.
But yeah I agree with Mr. Geddes that if he bought some better speakers he shouldn't need the room treatment.
Hope the thread starter doesn't mind a little off topic conversation.
Yes, but not possible if you rent a space or if you sell absorbers for a living - we look at Ethan Winer's livingroom 😉
Most people don't listen at reference level. Not even near. My setup is calibrated and I'm listening at 10-20dB below reference. So smaller speakers might be capable of delivering enough undistorted SPL for that type of application.
WAF, well, either you have to live with it or not.
That's a matter of believes as there are virtually no studies that objectively tell us what's right and what's wrong. All studies I know are not really conclusive for home sound reproduction.
Even with common piston speakers reflection levels (except the floor reflection) are below detection threshold (Olive et al.).
That's probably exactly the type of room most Americans use their speakers in.
Best, Markus
Yes, but not possible if you rent a space or if you sell absorbers for a living - we look at Ethan Winer's livingroom 😉
Most people don't listen at reference level. Not even near. My setup is calibrated and I'm listening at 10-20dB below reference. So smaller speakers might be capable of delivering enough undistorted SPL for that type of application.
WAF, well, either you have to live with it or not.
That's a matter of believes as there are virtually no studies that objectively tell us what's right and what's wrong. All studies I know are not really conclusive for home sound reproduction.
Even with common piston speakers reflection levels (except the floor reflection) are below detection threshold (Olive et al.).
That's probably exactly the type of room most Americans use their speakers in.
Best, Markus
Any two people viewing a movie in my room or in that room will ALWAYS pick my room as the better. If the kind of room that you show is OK for you then so be it. Its not OK for me, and you asked.
I do disagree about your sidewall reflection statement, just as I have always disgreed with Toole and Olive. They did not do detection thresholds, they did preference. Big difference. The side wall reflections are NOT below the detection threshold for an omni speaker.
It always amazes me how you can switch hats from "most people" to "very particular" to suite your position. "Most people" could care less about virtually everything that you obsess about.
I do disagree about your sidewall reflection statement, just as I have always disgreed with Toole and Olive. They did not do detection thresholds, they did preference. Big difference. The side wall reflections are NOT below the detection threshold for an omni speaker.
It always amazes me how you can switch hats from "most people" to "very particular" to suite your position. "Most people" could care less about virtually everything that you obsess about.
I'm more into folklore myself haha. But I am not a pro in anyway. It's my theory I guess which doesn't mean a thing in reality.I was thinking that if we could construct a speaker with an anechoic response from 20Hz - 40kHz that was as small as you could make it and had a perfect off axis response, it would be the best speaker ever. Of course that is way beyond practical theory.
I guess I have never been into big speakers since I haven't had the oportunity to hear many no compromise designs. The few that I have heard I get the impression from them that they tend to make everything sound .. well big and bloated.
I guess I have never been into big speakers since I haven't had the oportunity to hear many no compromise designs. The few that I have heard I get the impression from them that they tend to make everything sound .. well big and bloated.
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