As I tried to say above, it depends on your design goals. How loud do you want these to be able to play?
That port in 16L with heavy fill gives pretty much the same response as I posted above. Excellent. However with the cross-sectional area being so small, port speed quickly gets excessive at higher SPL's. Below is what it looks like with 30W, giving you about 100dB at 1 m before baffle step loss - so closer to somewhere around 94dB @ 1m in reality. Peaking is well above the red line (26 m/s) for content above 30Hz, suggesting that port noise is going to be a problem at those levels.
And don't forget, SPL's also drop off with distance from the source. So at 2m away for example, you are down another 6dB. And you have no second speaker here that would normally fill in some of that loss in SPL's.
If you are using WinISD pro, you can go to the "Signal" tab to change the input wattage. Then in the graghing window, you can choose "Rear port - Air velocity" to see the results. And I think choosing "Max SPL" will tell you how loud they will play a 1 m before baffle step loss. With WinISD though, I'm not sure if the program is distinguishing between series and parallel connections when using multiple driver.
Personally I would not want to build something that restricts the drivers so much and leaves them fairly underutilized even if most of the time I wouldn't be using them at their full potential.
So what is the maximum SPL's that you want and at what listening distance. Here's a link that gives you a quick and easy method to calculate the relationship between distance and SPL: Amplifier Power Required Calculator.
And it may also be worth doing a quick sim with your Jordon's to see what the max SPL out of those will be before xmax is exceeded at your desired xo frequency. Because ideally, you want to fairly closely match the max output of the drivers you are using in your design.
That port in 16L with heavy fill gives pretty much the same response as I posted above. Excellent. However with the cross-sectional area being so small, port speed quickly gets excessive at higher SPL's. Below is what it looks like with 30W, giving you about 100dB at 1 m before baffle step loss - so closer to somewhere around 94dB @ 1m in reality. Peaking is well above the red line (26 m/s) for content above 30Hz, suggesting that port noise is going to be a problem at those levels.
And don't forget, SPL's also drop off with distance from the source. So at 2m away for example, you are down another 6dB. And you have no second speaker here that would normally fill in some of that loss in SPL's.
If you are using WinISD pro, you can go to the "Signal" tab to change the input wattage. Then in the graghing window, you can choose "Rear port - Air velocity" to see the results. And I think choosing "Max SPL" will tell you how loud they will play a 1 m before baffle step loss. With WinISD though, I'm not sure if the program is distinguishing between series and parallel connections when using multiple driver.
Personally I would not want to build something that restricts the drivers so much and leaves them fairly underutilized even if most of the time I wouldn't be using them at their full potential.
So what is the maximum SPL's that you want and at what listening distance. Here's a link that gives you a quick and easy method to calculate the relationship between distance and SPL: Amplifier Power Required Calculator.
And it may also be worth doing a quick sim with your Jordon's to see what the max SPL out of those will be before xmax is exceeded at your desired xo frequency. Because ideally, you want to fairly closely match the max output of the drivers you are using in your design.
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Hi jReave
Thank you for your excellent explanation.
I will go with 2 ports that are 40cm long and have an internal diameter of 5cm. There is not a lot of choice for ports in Europe. The modular PSP ones that Madisound sell look very good, but shipping was going to be $50. I have bought some Monacor ones, and will go to the local plumbing shop for elbows and extensions. No nice flared openings on these
Thank you for your excellent explanation.
I will go with 2 ports that are 40cm long and have an internal diameter of 5cm. There is not a lot of choice for ports in Europe. The modular PSP ones that Madisound sell look very good, but shipping was going to be $50. I have bought some Monacor ones, and will go to the local plumbing shop for elbows and extensions. No nice flared openings on these
What most people do is terminate the port on the inside of baffle face and then roundover the wood opening in the front face to get a flare.
And on the inside, a heat gun on the plastic plus something to create a flare has been known to work as well.
Flaring is something that helps to reduce port noise by the way and with what you have decided to go with now, I don't think you are going to have a problem with that. Doesn't hurt though of course.
I guess you decided slot ports weren't going to work for you?
And on the inside, a heat gun on the plastic plus something to create a flare has been known to work as well.
Flaring is something that helps to reduce port noise by the way and with what you have decided to go with now, I don't think you are going to have a problem with that. Doesn't hurt though of course.
I guess you decided slot ports weren't going to work for you?
Hi
I thought that 2 small (50mm x 36mm) slots would look a bit ugly.
I have also considered using a single accuton passive radiator: sd 220cm2
http://www.falconacoustics.co.uk/downloads/Accuton/Datasheet%20P220.pdf
Thoughts?
I thought that 2 small (50mm x 36mm) slots would look a bit ugly.
I have also considered using a single accuton passive radiator: sd 220cm2
http://www.falconacoustics.co.uk/downloads/Accuton/Datasheet%20P220.pdf
Thoughts?
This ignores some complexities, but the slot port can have any dimensions so long as the cross-sectional area is accurate. Shapes can vary too. Triangles in the corners?
But if you don't like the looks, well..... you're the one that has to live with them.
I thought that Accuton PR was going to be much more expensive than it is, but they don't provide all the parameters I need to sim it in Unibox, so I'm afraid I can't advise at all in terms of suitability. Personally, I don't think the PR's that seem to be available to you are worth the cost if you are able to fit those ports into your design.
But if you don't like the looks, well..... you're the one that has to live with them.
I thought that Accuton PR was going to be much more expensive than it is, but they don't provide all the parameters I need to sim it in Unibox, so I'm afraid I can't advise at all in terms of suitability. Personally, I don't think the PR's that seem to be available to you are worth the cost if you are able to fit those ports into your design.
Build log started here:
http://www.diyaudio.com/forums/full...dan-jxr6hd-tang-band-w5-1138sf-build-log.html
http://www.diyaudio.com/forums/full...dan-jxr6hd-tang-band-w5-1138sf-build-log.html
Hi jReave
I am just about to start routing the holes for my drivers, but I haver just realised that The Tang Bands that I have bought are W5-1138SMF W5-1138SMF - 5" Paper Subwooofer - TB SPEAKER CO., LTD. and not the W5-1138SM http://www.tb-speaker.com/uploads/files/b94e657e4e684db6e43ead25dd51f3b7.pdf that you kindly did the box sims for.
Will my cabinet of 17litres with 2x 50mm ports of 400mm length still be ideal?
I am just about to start routing the holes for my drivers, but I haver just realised that The Tang Bands that I have bought are W5-1138SMF W5-1138SMF - 5" Paper Subwooofer - TB SPEAKER CO., LTD. and not the W5-1138SM http://www.tb-speaker.com/uploads/files/b94e657e4e684db6e43ead25dd51f3b7.pdf that you kindly did the box sims for.
Will my cabinet of 17litres with 2x 50mm ports of 400mm length still be ideal?
I don't think that will be a problem at all. The simulations suggest that the 2 drivers are similar enough that they are almost interchangeable.
Attached is a sim for the W5 SMF's you have purchased in 17L with 2 x 5cm ports 40cm in length with heavy stuffing. Looks almost identical to the previous one with the neo W5. If anything, there is a tiny little bit more output from about 100Hz down to the roll-off.
Now depending how much room gain you get in that frequency range, there is perhaps a potential for some boomy bass. Trying it out is really the only way to find out or not but here's a suggestion that you might want to think about and that I think you can implement without too much trouble: split your 17L woofer chamber down the middle into 2 separate 8.5L chambers, each with its own woofer and port.
There'll be no difference in each of the vented woofer FR's, but if you find the room is giving you too much of a boost in the 40Hz to 80Hz range, you have the option of adjusting the output in that frequency range by stuffing a single port instead of both of them. So in that case, your LF output below about 100Hz will be a combination of the sealed response (2nd attachment) and the vented response. So, half way between the vented FR and the sealed FR, the latter being what you get if you have to stuff both ports which is the only option when both woofers are in a single chamber.
One other suggestion I have is to not glue/seal up your front baffle right away. Clamp it in place if you have to to start. This will allow you to also make changes to the stuffing or port length if necessary which are your other options for fine tuning the LF response.
Attached is a sim for the W5 SMF's you have purchased in 17L with 2 x 5cm ports 40cm in length with heavy stuffing. Looks almost identical to the previous one with the neo W5. If anything, there is a tiny little bit more output from about 100Hz down to the roll-off.
Now depending how much room gain you get in that frequency range, there is perhaps a potential for some boomy bass. Trying it out is really the only way to find out or not but here's a suggestion that you might want to think about and that I think you can implement without too much trouble: split your 17L woofer chamber down the middle into 2 separate 8.5L chambers, each with its own woofer and port.
There'll be no difference in each of the vented woofer FR's, but if you find the room is giving you too much of a boost in the 40Hz to 80Hz range, you have the option of adjusting the output in that frequency range by stuffing a single port instead of both of them. So in that case, your LF output below about 100Hz will be a combination of the sealed response (2nd attachment) and the vented response. So, half way between the vented FR and the sealed FR, the latter being what you get if you have to stuff both ports which is the only option when both woofers are in a single chamber.
One other suggestion I have is to not glue/seal up your front baffle right away. Clamp it in place if you have to to start. This will allow you to also make changes to the stuffing or port length if necessary which are your other options for fine tuning the LF response.
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