Tang Band W6 2100 ported sub diy project

[vlad99]

I have a tang band w6 2100 woofer and i'd like to build an enclosure for it. I did plot the sub on winISD and on Basta! and was able to get the sub to play down to 21 hz at -3db with a 28 liter enclouser and a port tuned to 22.5 hz, the port adds to the enclosure about 3 liters (7cm diameter * 76 cm lenght). To me seems pretty great but i was a little worried about sound quality, the woofer itself seems to be fine, but i am concerned with the box kind of distorting the sound. I would be cutting the sub at around 100 Hz hoping to cut off any resonant frequencies of the port, but i am still concerned with some factors like the speed and overall quality of the bass. so basically the question is : "is it a good enclosure?". i will add some graphs from winISD so you can see how it performs.
Also i can't really translate in "good/bad" some of this graphs, like group delay, i heard is the indicator of the speed and is kind of an important graph, seems like under 10ms is good, but also i read that the lower you go the less is perceivable hence you can get away with more than 10 ms, i heard that it is important to match impedance phase with the crossover, how do i do that?, i also heard that the speed of the air at the port should not be more than 17m/s, but does it really matter at 20hz?(i'm reffering to the fact that most content doesn't have huge presence at 20hz anyway so the sub would not even have the possibility to reproduce these lower notes). again i am new and i'd like some advice, if i got something wrong correct me, i'd like to learn more about good sound and how to design better boxes. thank you in advance.

 

[digitalfrost]

Is that an 80cm long port? I'm not sure this is a good idea.

 

[voodooless]

Long ports in general are a bit tricky, but it can work. Given that this is only a 6” woofer, it won’t go super loud anyway, so port noise should be okay. In any case, make sure to flare both ends of the tube.

It would be good to plot the maxSPL curve to see if you don’t have too much sag below fs.

Personally, I would probably tune it a bit higher to get better power handling. Expecting output up to 20 Hz is a bit unrealistic anyway.

 

[DVDdoug]

but i was a little worried about sound quality

Your frequency response looks smooth so it should be fine if you don't over-drive it. Except I'm not sure about "port noises". The potential-possible port noise is also related to how hard you drive it... how much the air in the port is moving...

But you're probably not going to get "useful output" at 20Hz with a small woofer. And just for reference... You generally don't NEED 20Hz for music. The lowest note on a standard bass guitar is around 40Hz, and subwoofers used for live music and in dance clubs are usually tuned to go-down to around 40Hz. That's low enough for bass you can feel in your chest and by not trying to go lower they can make a more efficient speaker for filling a large venue with chest-thumping bass.

With your small woofer it might actually sound better if you allow a small bump around 40Hz, even if that means less output at lower frequencies (that you won't hear anyway). But I wouldn't expect bass you can feel.

...In a home environment you can make different compromises to go lower in frequency because you don't need as much output in the smaller space.

 

[vlad99]

The

Long ports in general are a bit tricky, but it can work. Given that this is only a 6” woofer, it won’t go super loud anyway, so port noise should be okay. In any case, make sure to flare both ends of the tube.

It would be good to plot the maxSPL curve to see if you don’t have too much sag below fs.

Personally, I would probably tune it a bit higher to get better power handling. Expecting output up to 20 Hz is a bit unrealistic anywhiay.

Hi, MaxSPL should be this graph.

 

[vlad99]

Is that an 80cm long port? I'm not sure this is a good idea.

Hi, why is that so?

 

[vlad99]

Your frequency response looks smooth so it should be fine if you don't over-drive it. Except I'm not sure about "port noises". The potential-possible port noise is also related to how hard you drive it... how much the air in the port is moving...

But you're probably not going to get "useful output" at 20Hz with a small woofer. And just for reference... You generally don't NEED 20Hz for music. The lowest note on a standard bass guitar is around 40Hz, and subwoofers used for live music and in dance clubs are usually tuned to go-down to around 40Hz. That's low enough for bass you can feel in your chest and by not trying to go lower they can make a more efficient speaker for filling a large venue with chest-thumping bass.

With your small woofer it might actually sound better if you allow a small bump around 40Hz, even if that means less output at lower frequencies (that you won't hear anyway). But I wouldn't expect bass you can feel.

...In a home environment you can make different compromises to go lower in frequency because you don't need as much output in the smaller space.

Thank you for the response, i agree that generally under 40-30hz there isn't much information anyway and i think i am going to build two boxes, the one tuned to 22hz and maybe a closed one or a bass reflex one tuned to 35-40hz. When you say "useful output" what do you exactly mean, based on the max spl graph it says that even at 25 hz i should be getting around 97db, i heard that small subs are not able to play low since they are not able to move enough air but since the graph suggests 97db does it mean that the woofer is just very very good or does it mean that it's going to play those frequencies at 97 db but not really sounding like a proper subwoofer? i guess what i am trying to ask is if this 6.5 inch that seems to play 25hz at 97db is going to sound the same as like a 15inch that plays the same note at the same spl, and if there are differencies where could they be? distorsion? "feeling" of the bass? perceived speed? thanks in advance.

 

[digitalfrost]

Hi, why is that so?

So the port itself has resonances (standing waves) and if you make it very long this can go into the band where the speaker plays.

You see that WinISD calculates the first port resonance at 226hz.
WinISD appears to use the half-wavelength resonance formula for ports:

f1 = c / 2L

WinISD treats the port as an open resonator rather than a quarter-wave resonator. A bass reflex port is not a perfectly open pipe, because one end is inside the enclosure, behaving somewhat like a closed end.

If you use the quarter-wave formula

fn = (2n-1)c / 4L

you will get a first port resonance of ~107hz.

In reality it might be somwhere in between. Can you check the air velocity inside the port? WinISD has a tab for it. e: The velocity depends on the signal power, so increase it from 1W to something realistic.

As an example: https://www.diyaudio.com/community/threads/help-with-bass-reflex-port-response.402016/

This guy here has some resonance at 500hz. Quater-Wave formula would say it should be at 330hz, half-wave formula would say it should be at 660hz.

So I imported the chassis myself into WinISD, with a small chassis like that, you kinda cannot help ending up with long ports.

 

[vlad99]

So the port itself has resonances (standing waves) and if you make it very long this can go into the band where the speaker plays.

You see that WinISD calculates the first port resonance at 226hz.
WinISD appears to use the half-wavelength resonance formula for ports:

f1 = c / 2L

WinISD treats the port as an open resonator rather than a quarter-wave resonator. A bass reflex port is not a perfectly open pipe, because one end is inside the enclosure, behaving somewhat like a closed end.

If you use the quarter-wave formula

fn = (2n-1)c / 4L

you will get a first port resonance of ~107hz.

In reality it might be somwhere in between. Can you check the air velocity inside the port? WinISD has a tab for it. e: The velocity depends on the signal power, so increase it from 1W to something realistic.

As an example: https://www.diyaudio.com/community/threads/help-with-bass-reflex-port-response.402016/

This guy here has some resonance at 500hz. Quater-Wave formula would say it should be at 330hz, half-wave formula would say it should be at 660hz.

So I imported the chassis myself into WinISD, with a small chassis like that, you kinda cannot help ending up with long ports.

the graph for the air velocity is this one, the driver is rated for 55W rms so i used that value as reference, also at that value it plays at around 98db. to avoid resonance can't i just cut the driver at around 100Hz?

 

[digitalfrost]

You need to take into account the steepness of the filter. If you use LR4 (24db/oct) at 80hz for example, you will only be down ~7.7dB at 100hz. You have the right idea, but 7.7dB is not that much.