HT sub tuning freqs (1 Viewer)

[Donnie M]

What are the popular tuning frequencies for ported home theater subs? I know many things come into play, especially the room's characteristics, but what kind of response is needed for a robust home theater sound? How about for a mix of music and movies?

 

[Benihana]

i'm in the same boat as you, trying to figure out what frequency is best for HT. It depends on what driver your using, and what its resonant frequency is. You typically would want to tune it around its Fs. In my case my driver has a Fs of 19hz, and from research, it seems like 18hz would be the best tuning point for the loudest HT bass. Tuning lower will give you deeper bass, but it will take some decibels away from 20-30hz, which is where most HT info is.

 

[Donnie M]

Yeah, that makes sense. I just don't want to design a system that looks good on paper and seems to have a flat response curve, then find out it's tuned too high or too low for HT.

Here's an example:

When building car audio subs you generally tune to around 30-35Hz, because this gives you a nice rolloff down to the subsonic range. Most music doesn't have a whole lot of material below 25-30Hz, so 30-35Hz is a safe tuning piont. I know HT can have tons of material below 30Hz, especially in action movies.

Is there some magical range like this for HT, or do you just try for the lowest tuning possible?

lol, would I just be better off building a sealed enclosure?

 

[Benihana]

I just converted my sealed subwoofer into a vented system. I tuned the ports to 18hz, and there is much more lowend now compared to when it was sealed, no contest there. If you want HT bass, do a vented system. I always thought the sealed was great for HT, and it still is, but its nothing compared to the vented version. Usually when people tune lower, they take into account the room gain that will add that lost information back in, but its risky because no one knows exactly how much room gain they are going to have. So i just tuned mine to be flat to 18hz. You can clean it up with a BFD if you prefer.

 

[Donnie M]

Ok, that makes sense. So, basically I want to tune as low as possible and still have a flat response? (or as close as possible)

 

[Benihana]

if you want crazy HT bass, you should tune around 17-20hz(driver dependent). Ever since I ported mine, it does alot better with music than I thought it would.

 

[ChrisBee]

If you use a telescoping port you can easily adjust the tuning of your sub. Then try playing sinewaves and checking against an SPL meter to see what is happening to the response in your own room.

Using PVC drainage/plumbing pipes and fittings will give you cheap, easily-available components that can be telescoped, elbowed or even returned through 180 degrees. Useful where there isn't much room in your box or cylinder. You can then add a flare either end of your port when you are happy with your tuning point. Don't glue anything together until your are finished testing.

 

[Donnie M]

I plan on making a sonosub, so the adjustable PVC port idea sounds pretty good. I want the enclosure to be as small as possible, as I'd like to take it with me to college, so an adjustable port would be ideal. Will having many tiered pipe sizes affect port velocity and create excessive port noise? I suppose if the velocity is kept high enough it wouldn't matter...

 

[Edward J M]

The subwoofer efficiency at Fb is directly tied to Vb.

Don't build a small reflex sub with a very deep Fb or it will roll-off well above Fb unless you use a lot of EQ (which sucks amp power and strains the woofer).

If you are putting the sub into a tiny room, you can get away with a slightly overdamped alignment and let room gain compensate. If the room will be larger, then shoot for a critically damped alignment which will be flat to Fb anechoic in your software models.

 

[Donnie M]

Cool, thanks for the tip Ed.