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Why are center channel speakers ported?


marcb515

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So, should I start drilling holes in my Heresys?? [*-)]

I hope that this is not meant as a serious question, but I would rather ask then make the assumption![:P] (Nor is this meant to be insulting if it IS a serious query!![:D]) ...Its just that the quality of this thread has deteriorated a 'bit'!!! And its hard to believe anyone is following it for anything other then comic relief at this point![:P]

For any of the various sealed and vented enclosure topologies and alignments, there are a series of relationships that can be modeled which provide a criterion for a integrated design.

As a result of Thiele, Small (and Benson), where closed and vented systems using equivalent circuit modeling methods were shown to provide good agreement, the frequency response of a closed and vented loudspeakers could be accurately predicted from well-defined measured driver and enclosure parameters (assuming a half-space acoustical spatial loading).

You cannot simply modify one variable as an independent variable and retain accuracy.

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Who---I see what you mean though if the level is dropped things may even out. Now what if you plot a sealed box with a high Q?

Anyway, I took dragon to imply that widerange efficiency was increased which seems obvious by his claim that efficiency and F3 are bettered, as though they were different things. I think he caught on later that they could be expressed as the same.

By now this is all about personality anyway. I like to watch him dance, a Domincan he should be though a Domincan is always bettered by a Jebbie.

How's about a movie about Ignatius, "Return of the Jebi".

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Hahahahahahahahaha!

To repeat my summary regarding ported enclosures from my first post:

"For a given transducer the advantages (OF A VENTED ENCLOSURE - per parallel structure with the previous severl paragraphs per proper English usage!!) include an extended low frequency response and greater efficiency in a smaller enclosure then that offered by a sealed enclosure. "

They are two characteristics referenced from different frames of reference for the same behavior! Much like you can describe the SAME system with both an impulse response in the time domain and the frequency response in the frequency domain!

Only one who does not understand the multiple legitimate frames of reference for a given system would invent a problem here!

Get your head out of your posterior and read Heyser!!!!!!!!!!

This is indeed a case of arguing with a fool!

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So, should I start drilling holes in my Heresys?? [*-)]

The cabinet modelled was 3.5 cubic feet for the ported and 1.7 cubic

feet for the sealed (small variations in the actual volume won't make a

huge difference). If you're going to port the heresy, then you might as

well just get yourself a cornwall, forte, or chorus and get superior

performance from the 15" driver.

I have a reversible ported heresy mod that I built a while ago...you

just remove the back panel, set the stock heresy in the seat and then

put the back panel on the back of the seat. I have no problem with

anyone that wants to try it out and see how "big" the improvement is.

It uses a slightly different configuration which means less low end

than I modelled, but there is definetly an improvement in the bass.

Whether or not it's an aesthetic option is a completely different issue

(not to mention I'm yet to go about finishing it).

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"for a given transducer" yada-yada "include an extended low frequency response and greater efficiency in a smaller enclosure then that offered by a sealed enclosure. ""

Your own words that imply that increased efficiency and lowered F3 are two different characteristics and an implication (which I think you believed) that venting effects broadband driver efficiency.

Now you can continue to call me a fool and whatnot but it doesn't change my thinking that you thought venting effected driver efficiency and have come around to a new notion of efficiency as this thing has gone along. Which is reasonable because I used to have that notion myself and I certainly value myself higher than I value you.

By the way, I thought you were leaving. Can't let it go, can ya? "Dragon".

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"...but it doesn't change my thinking that you thought venting effected driver efficiency and have come around to a new notion of efficiency as this thing has gone along. Which is reasonable because I used to have that notion myself and I certainly value myself higher than I value you."

"Anyway, I took dragon to imply..."

Yes you did so erroneously, but don't let reality confuse you!

I love your idiocy which says that you used to be stupid so everyone must be stupid too! What is this "used to be"??

And are Pre-Cambrian haploids capable of changing their thinking? Are they capable of thinking? Present day examples point to an answer of no...

And it is a joy(sic) on this site to encounter anal orifices such as yourself who are preoccupied with other individuals rather then the ideas presented. Especially when individuals like YOU persist in attempting to misrepresent their own asinine fantasy based upon their own preoccupied delusion and inability to interpret simple English.!

Persist in thinking anything you want! "For a given transducer" simply means that for the same driver - 'any' driver - common to the situation! The driver is thus removed as a variable and the enclosure and its various characteristic variables (especially the port as was the focus of the original post!! DUH!) are focused upon in the system! If it is removed as a variable, that means that it does not change! If this was not the case I would have never bothered to compare it to the acoustical suspension loading, as that would have rendered the repeatedly referenced sealed acoustical suspension enclosure as a purely superfluous point which it clearly was not. And it would make no sense to compare a transducer to an enclsure loading! But then I incorrectly assumed a somewhat lucid audience and failed to account for such wackos in the crowd. My bad. But I am confident that you will not allow such a fundamental fact confuse your persistent delusion.

The two characteristics are two characteristic perspectives of the same event! Just as the time and frequency domains portray the same event from different frames of reference! Multiple frames of reference of the same event are not mutually exclusive, nor do they represent different distinct 'things'! The distinction is meaningless. They simply infer context!

And you can say whatever YOU think, but don't misrepresent what I think! As I am capable of expressing exactly what I think! Even if it is wasted on an idiot such as yourself!

And I have consistently disagreed with your fantasy! And the rampant display of your ignorance and your perverse preoccupation with me doesn't make me stupid!

I don't give a f--- what you think. But I would appreciate your limiting your expression to your own confused ideas and NOT misrepresenting them as my position!

And as far as allowing your misrepresentation of what I said to stand??? Yes, you are much like excrement that remains stuck to one's shoe after one has gotten too close to such an unfortunate accident. But such seems to be the case when one is stuck dealing with a delusional wacko from Uranus. I can now more easily understand the persistence of the flies that persist in hovering about such excrement. I only wish it was easier to clean my shoes of your crap. I will try harder to avoid your pile of ignorance in the future as we walk by LMAO!

So as you have already acknowledged, this is no longer about any lucid acoustical point, but only of your wacko preoccupation with another person. So I must wonder why this feels like when out on the road one would be approached and propositioned by a preoccupied wacko to whom I would respond with a disingenuous 'thanks but no thanks' rejoiner characterized by polite disdain...

Shoo, fly.

Or, to rephrase using the immortal words of Clint Eastwood, "Does F O mean anything to you?"

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"...but it doesn't change my thinking that you thought venting effected driver efficiency and have come around to a new notion of efficiency as this thing has gone along. Which is reasonable because I used to have that notion myself and I certainly value myself higher than I value you."

"Anyway, I took dragon to imply..."

Yes you did so erroneously, but don't let reality confuse you!

I love your idiocy which says that you used to be stupid so everyone must be stupid too! What is this "used to be"??

And are Pre-Cambrian haploids capable of changing their thinking? Are they capable of thinking? Present day examples point to an answer of no...

And it is a joy(sic) on this site to encounter anal orifices such as yourself who are preoccupied with other individuals rather then the ideas presented. Especially when individuals like YOU persist in attempting to misrepresent their own asinine fantasy based upon their own preoccupied delusion and inability to interpret simple English.!

Persist in thinking anything you want! "For a given transducer" simply means that for the same driver - 'any' driver - common to the situation! The driver is thus removed as a variable and the enclosure and its various characteristic variables (especially the port as was the focus of the original post!! DUH!) are focused upon in the system! If it is removed as a variable, that means that it does not change! If this was not the case I would have never bothered to compare it to the acoustical suspension loading, as that would have rendered the repeatedly referenced sealed acoustical suspension enclosure as a purely superfluous point which it clearly was not. And it would make no sense to compare a transducer to an enclsure loading! But then I incorrectly assumed a somewhat lucid audience and failed to account for such wackos in the crowd. My bad. But I am confident that you will not allow such a fundamental fact confuse your persistent delusion.

The two characteristics are two characteristic perspectives of the same event! Just as the time and frequency domains portray the same event from different frames of reference! Multiple frames of reference of the same event are not mutually exclusive, nor do they represent different distinct 'things'! The distinction is meaningless. They simply infer context!

And you can say whatever YOU think, but don't misrepresent what I think! As I am capable of expressing exactly what I think! Even if it is wasted on an idiot such as yourself!

And I have consistently disagreed with your fantasy! And the rampant display of your ignorance and your perverse preoccupation with me doesn't make me stupid!

I don't give a f--- what you think. But I would appreciate your limiting your expression to your own confused ideas and NOT misrepresenting them as my position!

And as far as allowing your misrepresentation of what I said to stand??? Yes, you are much like excrement that remains stuck to one's shoe after one has gotten too close to such an unfortunate accident. But such seems to be the case when one is stuck dealing with a delusional wacko from Uranus. I can now more easily understand the persistence of the flies that persist in hovering about such excrement. I only wish it was easier to clean my shoes of your crap. I will try harder to avoid your pile of ignorance in the future as we walk by LMAO!

So as you have already acknowledged, this is no longer about any lucid acoustical point, but only of your wacko preoccupation with another person. So I must wonder why this feels like when out on the road one would be approached and propositioned by a preoccupied wacko to whom I would and would respond with disingenuous 'thanks but no thanks' rejoiner characterized by polite disdain...

Shoo, fly.

Or, to rephrase using the immortal words of Clint Eastwood, "Does F O mean anything to you?"

This post has to get the "eloquent slam award" I'm writing a note to myself " If dragonfry comes after me run and stick my head under a pillow. Tom I suggest you do the same.

Craig

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First of all....MOST of this thread has been informable. Man......it is so tiresome at times having to wade through all the BS just to feret out the info. [:(] Anyhow............

I seriously don't mean to be picky; however, this comment was made (name withheld to protect the guilty (innocent??)):

"Throughout the driver has been assumed to be a static variable - a given - a constant..."

I realize that I only have a minor in mathematics, but how in the hell can a variable be a constant? Was I sleeping in advance differential equations? I got a 'B' in the damn course. Anywho......... back to the TB and Dragon show. [:)]

Tom

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You evidently were sleeping...[:P]

In a multivariant model, one variable can be 'made' to be 'static' - defined to be common to all changes of state in the other variables. Within the context and scope of the model it thus becomes a constant. But that does not mean that it is an absolute constant that transcends the scope of the model nor of the particular case(s)!

And since my focus was on the enclosure, namely sealed versus ported enclusure characterisitcs, I couldn't care less what driver was being used as long as it would be considered viable for the addressed enclosure types. In other words, I was not referring to an electrostatic or ribbon or plasma or some other driver that was inappropriate for use in the design of a sealed or ported/reflex enclosure. Plus the scope of my example was meant to be a 50 word or so synopsis - a generalization.

But thanks to adding your input to the continuing nonsense of this thread.

So is anyone going to come up with some non-standard use of an exotic driver, such as a plasma driver, in a sealed or reflex enclosure and cite it as violating some imagined presonceived notion? At this point I would be terribly disappointed if this doesn't occur, as the only quality on this site that tends to live up to low expectations is the inanity so many have for missing the main point and becoming preoccupied with a non sequitar about which they are confused. And since they are confused, they naturally assume everyone else must be as well.

Sorry you were confused... But don't worry, as I trust you will find many here with whom to commiserate ...

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So, What have we learned?. This reminds me of the TalkBass "pissing" contests. I wanted to learn something here, but I got exhausted with the technical arguing.

I have an RC-7 in a cabinet under my TV. It has rear ports, so I felt I needed to cut two big holes in the back plywood of the cabinet to let the rear sound get outside the cabinet. It sounds the same now as it did before. FWIW

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I have an RC-7 in a cabinet under my TV. It has rear ports, so I felt I needed to cut two big holes in the back plywood of the cabinet to let the rear sound get outside the cabinet. It sounds the same now as it did before. FWIW

If your rear ported speaker is placed into a constrained volume that is not sufficiently large, you will effect the sound of the speaker system as your ports will be firing into an additional 'tuned' (or in this case an 'unintentionally tuned') enclosure.

Also, if you simply cut holes that are roughly the same size as the ports, the ports will be firing into an additional 'unintentionally tuned' ported cavity!

Unless this cabinet space and the holes are sufficiently large, either case will potentially effect the speaker systems response (and I am referring to the speaker SYSTEM, not some individual transducer - as I know some are slower out there!)

As I don't know the specific meaurements and cabinet specifics I can't predict what the difference might be off hand...(and the number to my psychic is busy![:P] )

A general 'rule of thumb' - it is not good to place a rear ported speaker, nor any speaker for that matter into a relatively small surrounding enclosure, as the enclosure will act as a tuned enclosure and potentially contribute to the response of the speaker system placed therein.

So the answer is a definate maybe...

Now let's see - do I think that is one thing or two things, or three things, or no things or some thing or ....??? [:P]

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