Quick 4th Order VS Vented graphs and a little on subwoofer sq.... - Car Audio Classifieds!
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  #1  
Old 04-21-2011, 01:52 PM
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Default Quick 4th Order VS Vented graphs and a little on subwoofer sq....

Alot of 4th order nuthuggers out there are so into the suposablility that 4th orders and other bandpasses sound good, and that it is mythical to say otherwise.

People think just because something has a flat response that it must have sq. Not true! You may be thinking that i am talking about cabin gain making a flat modeled box have a higher low end? No, not that.

Sq lies in more then just FR. Group delay is a pretty big thing, it is the real measurement of transient response!

Images of the FR and GD of a chebychev ported box, and a 0db ripple/gain 4th order box. Fyi, both the 4th BP AND vented boxes are litterally 4th order boxes(yes vented is literally 4th!) phase response:


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But heres what i mean with Freq response and Group delay, the GD of the 4th order is worse then the vented box:

FR

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GD

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I am not saying someone will like the sound better with the vented, that is personal. But the real tranient response is alot better with the vented box down to about 26hz, after that the ported box is a bit worse below that. Beeing that the passband f3 is before the GD improves on the 4th order BP you are looking at worse transient performance in this model.

So what is the diff between transient accurancy and a flat response(even after being measure IN CAR)? worse GD means that the timing is worse but can still be flat so the 4th order will lag some and the bass may be sloppier then the ported box(till a freq limit where the ported box unloads). Sealed box really do have the best SQ reguardless of flat response acheivable in ported box, the group delay is WAY better in a sealed box! Even if you have a peak in a sealed box!

It's all a tradeoff.

Last edited by Novicaine; 04-21-2011 at 06:27 PM.
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  #2  
Old 04-21-2011, 02:59 PM
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In defence of the 4th BP, to get a better GD from the modeled vented box it was tunned to 21.17hz!! When you tune the vented higher the 4th order looks a little better in comparision but not fully.
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Old 04-21-2011, 03:10 PM
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A few MS isnt a big deal, especially in car when I would think reflections and all would have a huge effect on arrival/phase at listening position as well.

I just keep laughing at people going for 4th orders in subs that just dont like them and thinking theyre louder. Especially given that with the extra space used, you couldve correctly done more woofers in a vented box and been just fine.

Good to see some activity of discussion though.
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  #4  
Old 04-21-2011, 03:13 PM
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I grew up on sealed boxes! The whole ported thing gets blown out of proportion. The ported enclouser has its place as well as the 4th order. But then you limit yourself on FR and the ability to listen to a wider range of music and still sound good(were the SQ comes into play) But I think that so many people listen to a clipped signal and think its bass. That if they did run the proper enclouser it still wouldn't matter. The sound wouldn't be what the expected, so to compensate they turn the gain up.
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Old 04-21-2011, 03:15 PM
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I personally have ALWAYS been a proponent of the sealed design for all the reasons you listed and I have just liked the sound better. However over the last couple summers I have been trying different setups. I did my first ported box last summer and Im doing a 4th now. Im seeing the benefits of different setups and am impressed with the vented design. I was always a little leary of different designs, but im now trying them.

I agree with you 100% it is a tradeoff, do you want tight controlled sound, do you high output the end user has to decide what he/she wants and build around that. There really is no PERFECT box, taht does everything you want all the time. I think each box has its place and in the right conditions all can give the performance the user wants, but it is up to the user in the end.

Very informative post and thanks for posting the graphs.

Tim
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Old 04-21-2011, 03:49 PM
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Quote:
Originally Posted by surreal View Post
A few MS isnt a big deal, especially in car when I would think reflections and all would have a huge effect on arrival/phase at listening position as well.

I just keep laughing at people going for 4th orders in subs that just dont like them and thinking theyre louder. Especially given that with the extra space used, you couldve correctly done more woofers in a vented box and been just fine.

Good to see some activity of discussion though.
I like discussion

About the GD not being a big difference, i agree, i am just showing it so all the nuthuggers will be more quiet about them being perfect. 6ms for 60hz isnt that small a diff though.

Quote:
Originally Posted by audioarsonal View Post
I grew up on sealed boxes! The whole ported thing gets blown out of proportion. The ported enclouser has its place as well as the 4th order. But then you limit yourself on FR and the ability to listen to a wider range of music and still sound good(were the SQ comes into play) But I think that so many people listen to a clipped signal and think its bass. That if they did run the proper enclouser it still wouldn't matter. The sound wouldn't be what the expected, so to compensate they turn the gain up.
Quote:
Originally Posted by quaddropper View Post
I personally have ALWAYS been a proponent of the sealed design for all the reasons you listed and I have just liked the sound better. However over the last couple summers I have been trying different setups. I did my first ported box last summer and Im doing a 4th now. Im seeing the benefits of different setups and am impressed with the vented design. I was always a little leary of different designs, but im now trying them.

I agree with you 100% it is a tradeoff, do you want tight controlled sound, do you high output the end user has to decide what he/she wants and build around that. There really is no PERFECT box, taht does everything you want all the time. I think each box has its place and in the right conditions all can give the performance the user wants, but it is up to the user in the end.

Very informative post and thanks for posting the graphs.

Tim
Sealed boxes are great.


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Last edited by Novicaine; 04-21-2011 at 03:51 PM.
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  #7  
Old 04-21-2011, 04:00 PM
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Agree totally with Hurican3. I've tried them all (TC in sealed, 4th order, and vented) and ended up with a proper ported enclosure. I can confirm the slight delay a 4th order has over a vented design, and can also confirm that the bass is a bit "sloppier" for lack of better term. The graphs only confirm my belief.
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Old 04-21-2011, 04:08 PM
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Thanks upgradde. When i first started understanding and reading frequency response graphs i thought that a flat response was all there is to "sq", or good sounding alignment. Thats why i want to learn horns better.
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Old 04-21-2011, 04:31 PM
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I'm going to bet 99% of the people who read this have no idea what group delay is.
http://www.adireaudio.com/Files/GroupDelay.pdf


Anyway, one of the reasons people go ported over sealed despite the increase in group delay, is the efficiency boost of the vented enclosure. A woofer in a sealed enclosure requires far more excursion to reach the same level of output as a woofer in a properly tuned vented enclosure.

You sometimes see people talk about the effects of time distortion and group delay, but some of the same people push their woofer to levels of absurd distortion to reach the same level of output a ported enclosure could have within it's normal bounds.

Also, group delay is directly tied to frequency response. If you tune low enough, the sharp rolloff of the vented box won't even matter because your program material won't even play that low.
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Old 04-21-2011, 06:23 PM
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That adire pdf is a great read i also found a while back
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