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-   -   Ported sub with good transient response (https://www.diyaudio.com/forums/subwoofers/337618-ported-sub-transient-response.html)

audfrknaveen 8th May 2019 05:22 AM

Ported sub with good transient response
 
1 Attachment(s)
Dear all,

How much GROUP DELAY is acceptable in a PORTED SUB to have good TRANSIENT RESPONSE?

The goal is to design a sub with tight bass to the extent possible.
The sub should work reasonably "ok" for both movies and music in a HT.
I know everything is a trade off in subwoofer design and the room modes play a role too.

But in the design phase, "in a very general sense" what is the maximum group delay we can restrict to?

As an example.... in the attached image, RED is large box tuned to 25hz
And GREEN is small box tuned to 36hz. Obviously GREEN graph has better transient response. But how much group delay is too much in general ??

Thanks & Regards,
Audfrknaveen

trojantrow 8th May 2019 06:30 AM

Actually itís the red line that has the best group delay not the green.. to understand this you need to know where most of the bass frequencies are in movies and music.

These frequencies tend to be at above 30hz and below 100 hi with a very strong bias for the 40 to 80 area

All these places are where the red line is lower than the green.

Also to throw another one in, the lower the frequency the higher the output has to be for your ears to hear it. And group delay is less important.

So basically, go big and tune low. A 20hz tune is good for movies and music.. the group delay wonít really get going for music

freddi 8th May 2019 07:04 AM

hi trojantrow - what is your take on assisted 6h order bass reflex? I think but can't prove some of those will in practice, sound "tight".

of course the example below at ~42Hz tuning isn't subwoofer territory - but IIRC, close to some of the old EV Interface designs
such as Interface B.

https://i.imgur.com/OzpNpoX.png

TBTL 8th May 2019 07:58 AM

Equalization of room modes is more important for tight bass than having a subwoofer with a low group delay.

audfrknaveen 8th May 2019 08:29 AM

Quote:

Originally Posted by trojantrow (https://www.diyaudio.com/forums/subwoofers/337618-ported-sub-transient-response-post5784192.html#post5784192)
Actually itís the red line that has the best group delay not the green.. to understand this you need to know where most of the bass frequencies are in movies and music.

These frequencies tend to be at above 30hz and below 100 hi with a very strong bias for the 40 to 80 area

All these places are where the red line is lower than the green.

Also to throw another one in, the lower the frequency the higher the output has to be for your ears to hear it. And group delay is less important.

So basically, go big and tune low. A 20hz tune is good for movies and music.. the group delay wonít really get going for music

Thats an interesting point. !!! Thanks a lot.

audfrknaveen 8th May 2019 08:32 AM

room modes are definitely important!!! . Im trying to understand what care we can take before building the box to make it sound less boomy.

trojantrow 8th May 2019 08:32 AM

I agree with the above also... the tight bass muddy bass myth.

E.g I run a DIY alpine swr1542D in a sealed box.

I have room correction built in to my anthem AVR.i can have it sounding tight and not able to locate the sub.

Or. Do it wrong and itís muddy and horrible.

Spend more time getting the crossover to the mains correct and the slopes of the crossovers correct and it will sound good, donít worry about that.

Circlomanen 8th May 2019 08:38 AM

1 Attachment(s)
Attachment 755182
Simulation.

ROAR with Helmholtz front resonator
Layout, prototype of something similar but with another driver and passband, and measurements of the prototype.

With a pronounced peak centered around the midbass you get a very tight punchy and tactile character. Very usable for both music and HT.

Bass reflex has its limitations in "tightness" and punch suitable for HT. A driver suitable for BR has to much moving mass and to little Bl for a good mid bass punch and perceived tightness. The port in a BR takes several wavelengths to reach peak amplitude - which is pretty much the opposite of "tightness".

TBTL 8th May 2019 08:54 AM

Quote:

Originally Posted by audfrknaveen (https://www.diyaudio.com/forums/subwoofers/337618-ported-sub-transient-response-post5784263.html#post5784263)
room modes are definitely important!!! . Im trying to understand what care we can take before building the box to make it sound less boomy.

Nothing, except designing the subwoofer such that it does not produce bass.

trojantrow 8th May 2019 09:03 AM

Quote:

Originally Posted by freddi (https://www.diyaudio.com/forums/subwoofers/337618-ported-sub-transient-response-post5784210.html#post5784210)
hi trojantrow - what is your take on assisted 6h order bass reflex? I think but can't prove some of those will in practice, sound "tight".

of course the example below at ~42Hz tuning isn't subwoofer territory - but IIRC, close to some of the old EV Interface designs
such as Interface B.

https://i.imgur.com/OzpNpoX.png



Hi freddi.

I wish I could help you but what Iím sharing here is just what I have learned from constant reading and first hand experience. I donít actually know I lot about the different types of subwoofer design. At all

Wish I did and wish I had the skills to build them.

I ended up going with a simple strategy

Pick a good big driver
Build the right size good sealed box
Make sure itís set up right.

Sounds good as well. Better than subs that cost a lot more

Wish I could help you more but hopefully someone will come a long with much more experience than me to help you out


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