Hi,
I am trying to figure out if given the T?S parameter of a driver, how does one determine what type of enclosure is better sealed or port?
Oon
I am trying to figure out if given the T?S parameter of a driver, how does one determine what type of enclosure is better sealed or port?
Oon
There can be lots of opinion on this one. Personally I prefer the sealed enclosure as it's easier to implement and you'll get a leaner and smoother bass. Ported is a good way of getting a bit more apparent bass from a smaller box, but difficult to get right and difficult to integrate with your room.
I personally prefer sealed enclosures too. I am just trying to understand the theory, something to do with the Q of the system...
On a different note do you know if it is necessary to create a groove for the speakers to be sunk into the cabinets. I've heard that it makes a difference to the sound.
Oon
On a different note do you know if it is necessary to create a groove for the speakers to be sunk into the cabinets. I've heard that it makes a difference to the sound.
Oon
Most woofers can be made to work in both a sealed box or a vented box.
Here are other issues to consider: Size. A properly vented system will typically be twice as big as the same woofer in an appropriate sealed box. Power handling. A vented system will have a nice increase in available output at the excursion null of the vent frequency, but it will have more excursion below that frequency. Transient response. A vented box is higher order and will tend to have worse transient response.
David S.
Here are other issues to consider: Size. A properly vented system will typically be twice as big as the same woofer in an appropriate sealed box. Power handling. A vented system will have a nice increase in available output at the excursion null of the vent frequency, but it will have more excursion below that frequency. Transient response. A vented box is higher order and will tend to have worse transient response.
David S.
Huh?!?!? Coming from you, Dave, this is a bit of a boggle. A major selling point of reflex systems has always been "reduced size".
The EVM12L, which was designed for a ported cabinet, has a Qts of .232. I suspect even lower Qs would work as well. Thing is, as the Q goes up, the bandwidth of the "bass boost" from the port gets narrower, and someplace above .7 it becomes a "Why bother?". The slight amount you can lower the bass response isn't worth the faster roll-off.
A rebate (groove) for a woofer is a nice touch, but I'd worry more about reflections from the grille frame or edge diffraction unless you're talking a very high xover.
True, but you have to be careful not to be doing an "apples and oranges comparison".
Vented boxes are inherently higher performance and will give a lower cuttoff with the same efficiency, but only if you redesign the woofer to get there. (more magnet strength plus more cone mass)
If you start with a given woofer then the ideal vented box volume is typically about twice the size of the ideal sealed box.
David S.
You can use EBP as a guide. EBP=Fs/Qes and if less than 50, then use sealed, if greater than 100, then use vented. For values between 50 - 100 it could go both ways. Excursion available is also a consideration as generally sealed may need more travel.
I'm referring to the efficiency, f3, box size tradeoff. The vented box is inherently better in that regard. i.e. if you pick sensitivity and box size the vented box will go lower. If you pick f3 and box size the vented box will be more efficient, all assuming optimum woofers and enclosures.
David S.
I'm surprised no one has mentioned modelling 🙂 If you have MS excell, get a hold of unibox and try modeling in each of vented and sealed, and get a visual idea of how it will perform in each. Also will demonstrate what David is saying about vented generally needing a bigger box compared to sealed for any given driver. going to the various tabs in the spreadsheet gives heaps more info about the performance characteristics.
Tony.
Tony.
+1 Model both configurations in a modeling software,Unibox,WinIsd,etc...
After you draw up your requirements that should give you a idea on what box would be best.Keep in mind no two applications are the same.So you want to consider the room in which these speakers are going into as well, they all make a difference. 😉
Dear Winter mute, Altec Best,
I did consider modelling, but most people told me that I really really really need to beef up my body first before I can consider that as a career. 🙁
My wife on the other hand, says i don't stand a chance and I should just stick to building speakers.😉
I did a bit of modeeling based on some simple box claculator, but I suppose winISD and unibox are more complicated software.
Where can I get them, are they available for free?
Oon
I did consider modelling, but most people told me that I really really really need to beef up my body first before I can consider that as a career. 🙁
My wife on the other hand, says i don't stand a chance and I should just stick to building speakers.😉
I did a bit of modeeling based on some simple box claculator, but I suppose winISD and unibox are more complicated software.
Where can I get them, are they available for free?
Oon
Woofer enclosure design assistance
Go here: http://www.mh-audio.nl/spk_calc.asp
Some very good free calculators that will help you gain some insight into sealed vs. ported alignments.
Go here: http://www.mh-audio.nl/spk_calc.asp
Some very good free calculators that will help you gain some insight into sealed vs. ported alignments.
Grin 🙂
you can download unibox here UniBox - Unified Box Model for Loudspeaker Design - Kristian Ougaard
It is my proffered application.
Winisd is available here LinearTeam some people really like it but I'm not keen on it.
If you have the patience akabak is worth a look but I'd strongly advise reading this thread before trying http://www.diyaudio.com/forums/multi-way/90362-akabak-simulator.html#post1840182 The "standard" alignments feature is pretty cool!
Tony.
Loudspeaker Design Cookbook (6th Ed) by Vance Dickason, section 1.40 and EBP came from R.Small (the "S" in T/S (Thiele/Small) parameters).
To get the most out of a driver it needs to be loaded correctly and EBP is a good guide on it's use. It's a waste of time trying to get a driver designed for vented use to work in sealed and visa versa. There are drivers such as the 18W8531 that can go both ways as it has an EBP around 71.
Have a look at WinISD and as you choose a driver it shows the EBP and an appropriate loading (little bar graph as well).
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So the debate seems to be between 'performance'/efficiency versus sound quality?
Personally I'd trade a few Watts for a nice smooth uncoloured bass.
Personally I'd trade a few Watts for a nice smooth uncoloured bass.
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