Richard, bass reflex don't work anything like you're describing. I know intuitively it seems right, but you really should do a search on the principles. I'm at work, so I don't really have the time for a long essay.
i have done research and asked on other forums. i mostly got replies like yours "be ready for super sophisticated physics, your mind will melt"
and then those people promising such a detailed mind melting explanation dissappeared never to be heard from again.
if 5min video about theory of relativity can leave your mind clear and without questions then so should a passive radiator 5 min video.
lets agree theory of relativity is a lot more complex than spring oscillation physics.
at the moment i am leaning to think that this is a very inconvenient truth for speaker manufacturers. sales pitch is "its the best of the two worlds: sealed box and ported box. that's all those consumer chimps on budget need to know. more information will expose all the flaws" everyone wants bass. its impossible to sell any bookshelf speaker without bass. it will be the first complaint of reviewers and you are out of business. since everyone is cheating bass out of small boxes you have to do it too to stay alive in business. if you can't explain something simply then you don't understand it yourself.
and then those people promising such a detailed mind melting explanation dissappeared never to be heard from again.
if 5min video about theory of relativity can leave your mind clear and without questions then so should a passive radiator 5 min video.
lets agree theory of relativity is a lot more complex than spring oscillation physics.
at the moment i am leaning to think that this is a very inconvenient truth for speaker manufacturers. sales pitch is "its the best of the two worlds: sealed box and ported box. that's all those consumer chimps on budget need to know. more information will expose all the flaws" everyone wants bass. its impossible to sell any bookshelf speaker without bass. it will be the first complaint of reviewers and you are out of business. since everyone is cheating bass out of small boxes you have to do it too to stay alive in business. if you can't explain something simply then you don't understand it yourself.
Respectfully suggest you stick a microphone there and hook it to an oscilloscope.
Your ears won´t help much at very low frequencies but trace will definitely wiggle up-down.
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We were already slipping at the Physics end, now you add conspiracy to it?
Let alone insulting buyers.
Yes, because everybody reads 6 moons before heading to the Audio shop. 🙄
Boy you certainly despise everybody 😳
Simple explanations are fine, but holding at least some relation to reality helps a lot.
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i have to read up on sounds from ports. they most probably do produce sound. i am relatively new in the field. but either way ported and passive radiators play out of phase. so sealed boxes are more accurate in sound reproduction.
No, they most certainly produce sound!
At the tuning frequency, the cone excursion is reduced to a minimum, but the enclosure radiates strongly through the vent.
so can you provide that super sophisticated explanation of passive radiator operation with some relation to reality ? i am sure it will help a lot now
no one is slipping on physics end. i haven't seen any physics yet. only unproven claims that you are an Einstein level physicist. but no proof. so show proof or else continue the life of a poser, Einstein in virtual world, the wizard of oz.
no one is slipping on physics end. i haven't seen any physics yet. only unproven claims that you are an Einstein level physicist. but no proof. so show proof or else continue the life of a poser, Einstein in virtual world, the wizard of oz.
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http://speakerdesignworks.com/Sealed_v_Vented.htmlhttp://speakerdesignworks.com/group_delay.htmlHere's some good articles on the subject from http://speakerdesignworks.com/index.html
You are obviously not prepared to listen to what you are being told, so I see no point in continuing the conversation.
thank you for making my point, wizard of oz.
did you notice that I was querying the issue. not claiming that what i think is the absolute truth. you on the other hand are running away into hiding, because you don't understand the topic clearly yourself. but you sure do understand how to pose as a world renowned physicist.
thank you for those articles. was briefly reading about group delay.. and human perception of them. good topic to learn more about
This kid does a pretty good demonstration of how bass reflex works:
In your model, you state that the woofer cone moving in causes the passive radiator (or air mass in a port) to move out, as if by rigid connection. But it's not rigid. The air in the box acts like a spring. And that spring interacts with the system resonance of the PR or port air mass in a dynamic way. So the woofer cone mass has its own behavior, and the PR or port air mass has its own behavior, and the two are only loosely couple by a spring. Around the system resonance, both masses move in harmony, but also in phase, as shown in the video.
PRs have two main advantages. They are great for small boxes, because small air volumes require very long ports for a given resonant frequency compared to larger air volumes. So trying to stuff a long port into a small box is obviously a problem. PRs don't take up space in box so problem solved. Also PRs don't have pipe resonances, so second problem solved. I should add though, that they have there own diaphragm resonances, but measurements I've seen suggest they aren't strongly excited by the woofer. So those are the two considerations you should be thinking about regarding your original question. All the stuff about ports not making sound and xmax should be dropped since that's not how they work and aren't relevant.
In your model, you state that the woofer cone moving in causes the passive radiator (or air mass in a port) to move out, as if by rigid connection. But it's not rigid. The air in the box acts like a spring. And that spring interacts with the system resonance of the PR or port air mass in a dynamic way. So the woofer cone mass has its own behavior, and the PR or port air mass has its own behavior, and the two are only loosely couple by a spring. Around the system resonance, both masses move in harmony, but also in phase, as shown in the video.
PRs have two main advantages. They are great for small boxes, because small air volumes require very long ports for a given resonant frequency compared to larger air volumes. So trying to stuff a long port into a small box is obviously a problem. PRs don't take up space in box so problem solved. Also PRs don't have pipe resonances, so second problem solved. I should add though, that they have there own diaphragm resonances, but measurements I've seen suggest they aren't strongly excited by the woofer. So those are the two considerations you should be thinking about regarding your original question. All the stuff about ports not making sound and xmax should be dropped since that's not how they work and aren't relevant.
so far from reading bunch of articles and youtube videos it sounds like closed boxes facilitate much lower group delay than vented or passive radiator designs
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Sealed has lower group delay, but also lower SPL. You need to decide what is more important for your needs. I'm ignoring EQ of sealed for simplicity.
But how "tight" depends on the sealed box Q.
A PR is a replacement for a vent and will follow the alignments of a vent.
Vents absolutely produce sound.
Drivers move to X-Max because an amplifier drove it there. Not the alignment.
Alignment, no matter which method, controls F3 and slope. Not excursion.
Only SPL at the lower end of the passband. Above that SPL is a function of driver efficiency.
This is because of the slower rolloff rate, like any filter. Group delay is the derivative of the phase wrt frequency.
aguerpro. thanks for the video. but its the same model as on video by definitive technology I posted before.
point of both videos is at the perfect resonance frequency passive radiator does produce bass and now it's clear how its in phase with active driver. but below resonance its out of phase.
and above resonance frequency it's still shaking around randomly and contributes to some low end back ground noise, that some perceive was "warmths" some perceive is fogue
point of both videos is at the perfect resonance frequency passive radiator does produce bass and now it's clear how its in phase with active driver. but below resonance its out of phase.
and above resonance frequency it's still shaking around randomly and contributes to some low end back ground noise, that some perceive was "warmths" some perceive is fogue
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