Hello All,
Is it ok if I build a very shallow box for a ported sub? I will maintain the required volume by increasing the height and width. But I want the depth to be as low as possible. Purpose is to keep the sub behind my projector screen.
In this video, at 2min 15 sec, he says the subwoofer needs to have the required "depth"
YouTube
Is the depth very important? Or can we build a shallow box leaving just around 1 inch behind the driver magnet? (something like the subs behind the screen in a baffle wall) I know im violating the golden ratio, standing waves issue etc. But any other issues with shallow boxes for sub??
Can any one suggest please .... Thanks in advance, AudFrkNaveen
Is it ok if I build a very shallow box for a ported sub? I will maintain the required volume by increasing the height and width. But I want the depth to be as low as possible. Purpose is to keep the sub behind my projector screen.
In this video, at 2min 15 sec, he says the subwoofer needs to have the required "depth"
YouTube
Is the depth very important? Or can we build a shallow box leaving just around 1 inch behind the driver magnet? (something like the subs behind the screen in a baffle wall) I know im violating the golden ratio, standing waves issue etc. But any other issues with shallow boxes for sub??
Can any one suggest please .... Thanks in advance, AudFrkNaveen
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The Golden ratio is really not important unless you are a strong believer in the biblical proportions of the golden rule. As long as the required volume that is needed is inside the box you can do whatever you want. Standing waves inside the cabinet are miniscule compared to the standing waves in the room itself.
When building shallow subwoofer it is wise idea to use driver itself as enclosure reinforcing structure by means of pressing magnet against box backwall and apply moderate tension. Subwoofer box does not 'require' particular depth or any 'golden ratios' unless it is insufficient to maintain correct cabinet volume. Most important (audible) standing wave is that one perpendicular to driver's membrane and shallow box can throw it really high past operating passband. Becouse of large width/height ratios of sidewalls no further reinforcing structures are necessary which is crucual for preserving high interior/exterior box volume ratio.
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USRFobiwan & Windforce85
Thanks a lot for the inputs !!!!
First of all I am happy that shallow sub is possible as long as we maintain the volume
Thanks you for the help !!
Thanks a lot for the inputs !!!!
First of all I am happy that shallow sub is possible as long as we maintain the volume
Thanks you for the help !!
by the way ...
I know how to calculate the port size and length etc.
But I have a few questions....
1. Is it necessary to put the port on the same side as the driver?
2. If so, how close or how far away from the driver should i place the port? Any thumbrules?
3. Lets say the driver is mounted on the front of the enclosure, is it ok to put the port at the bottom or top of the enclosure? Or on the Sides?
Since I m going to build a shallow sub, the depth will be around 8", width will be around15" and the height will be 4 or 5ft based on the volume.
So a long port can be used if I place it down firing or up firing. Any problem with this??
For a side port I may use a bend inside.
I know how to calculate the port size and length etc.
But I have a few questions....
1. Is it necessary to put the port on the same side as the driver?
2. If so, how close or how far away from the driver should i place the port? Any thumbrules?
3. Lets say the driver is mounted on the front of the enclosure, is it ok to put the port at the bottom or top of the enclosure? Or on the Sides?
Since I m going to build a shallow sub, the depth will be around 8", width will be around15" and the height will be 4 or 5ft based on the volume.
So a long port can be used if I place it down firing or up firing. Any problem with this??
For a side port I may use a bend inside.
No. Shallow design calls for labyrinth design:
But with driver placed on 'side' wall instead of 'front' as on this picture. I'm astonished that it is not done more frequently in DIY so finding an exact example pic is very hard.
Eventually, for higher performing subwoofer use passive radiator next to active driver in form of this:
But front-to-back reinforcing points around passive radiator are necesssary.
But with driver placed on 'side' wall instead of 'front' as on this picture. I'm astonished that it is not done more frequently in DIY so finding an exact example pic is very hard.
Eventually, for higher performing subwoofer use passive radiator next to active driver in form of this:
But front-to-back reinforcing points around passive radiator are necesssary.
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Hey Windforce85,
Please see the attached pic, those were the ideas I was considering.
Option 1 : Port is very close to the driver
Option2: Port is at the bottom end of the enclosure. (away from the driver)
Option3: Down firing port
Option4: Side firing port.
Im inclined towards option4, since the air from front port may vibrate my PJ screen. Side port may not have that issue.
When you say labyrinth , do you mean something like transmission line?
Please see the attached pic, those were the ideas I was considering.
Option 1 : Port is very close to the driver
Option2: Port is at the bottom end of the enclosure. (away from the driver)
Option3: Down firing port
Option4: Side firing port.
Im inclined towards option4, since the air from front port may vibrate my PJ screen. Side port may not have that issue.
When you say labyrinth , do you mean something like transmission line?
Attachments
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Labyrinth is only semantics, I meant bass reflex tunel in form of labyrinth in order to save space and make some 'free lunch' reinforcements to the enclosure. You're free to try other alignments techniques, you can sim it in Hornresp but it is additional time and effort and it is also measured as design cost efficiency.
I'd rather put active driver and port together close to the floor so you will gain a few dB more SPL for free due to boundary coupling.
Any other shapes, forms or angles are irrelevant for subwoofers while box/tunnel volumes and tunnel minimum cross-sections are preserved.
I'd rather put active driver and port together close to the floor so you will gain a few dB more SPL for free due to boundary coupling.
Any other shapes, forms or angles are irrelevant for subwoofers while box/tunnel volumes and tunnel minimum cross-sections are preserved.
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Transition between bass reflex which is simple Helmholtz resonator and transmission line which is quarter-wave resonator is smooth in case of this particular design and you can explore it using Hornresp. There are drawbacks and benefits each of the alignments mentioned here. Personally I'd go for sealed subwoofer with small help of DSP technology as it will deffinitely yield most compact, flexible and highest performing unit with correct driver(s) used. Potential drawback is that you possibly need to rethink all your audio setup.
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my driver EBP (efficiency bandwidth=Fs/Qes) is more than 100 ... so in theory it is more suitable for ported.
Im not sure how strictly we have to consider this EBP.
Will it sound good if we build a sealed sub with a driver that is more suitable for ported?
Im not sure how strictly we have to consider this EBP.
Will it sound good if we build a sealed sub with a driver that is more suitable for ported?
Port location is irrelevant for sub, I guess you want the port to be a low tuning type somewhere below < 50hz. So cancellation is not a problem here with those wavelengths. Phase should also not be an issue.
Well, I tend not to agree with it. Even at 50 Hz 1-meter height distance between uncorellated sound sources is 60-degree phase shift in vertical plane, from room modal response point of view it still can be considered as significant level for end result. Don't forget also about pressure wave propagation time inside of tall enclosure.
If its going behind a screen, the port(s) do not even need to be inside the box. That would make it easier to tune if any adjustment is needed!
Amen to that Xoc1. Not thought about that. I would als do multiple subs across the screen if its al behind it.
dear all ... thank you very much for so many valuable suggestions !!!
I got the point that since the sub is behind the screen, the port need not be inside the box. I dont want to put it on the front baffle as the port air may move the screen material. Thats the reason I started this thread to find out if the port placement should be on the same side of the driver .... or distance between the driver and the port is important etc etc ....
Thanks again for all the help people ... !!!
I got the point that since the sub is behind the screen, the port need not be inside the box. I dont want to put it on the front baffle as the port air may move the screen material. Thats the reason I started this thread to find out if the port placement should be on the same side of the driver .... or distance between the driver and the port is important etc etc ....
Thanks again for all the help people ... !!!
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