Please Explain Tuning

[Bill 3]

Hi guys, I am new here and have already learned a lot.

Can someone explain tuning - Why choose 12Hz over 20Hz? I am talking about a LLT or sonotube. I am sure some depends on the driver used, but I see where members have used a Splinter Sound RL-p18 with boxes tuned from 11 to 23 Hz

I have a lot of questions and I know that search is my friend, so I will attempt that first.

I currently have a Klipsch KSW-15 and have recently moved things into a lot bigger room Theater/game... and I find myself less than impressed-my reason for being here. I am pretty much convinced to build a sonotube with 15 or 18" driver (maybe 2 of them).

Thanks,
Bill

[ringbearer3791]

i'm relatively new to this as well but i'll attempt to answer your question regarding tuning and why to tune low rather than higher in an LLT setup. The size of the port tunes the frequency response of the subwoofer, WinISD pro is a great free program you can download from on the site here and a little playing around with it will allow you to visualize how a different tuning frequency for a given size box will affect frequency response. The traditional issue with ported subwoofers comes from poor response at and below the tuning frequency. If the subwoofer is designed for music use alone then a tuned frequency of 20 Hz isn't likely going to cause any problems since music doesn't really get down that low but in HT applications there are definitely effects that do reach down into the low 20s or even the teens. The goal with a ported HT sub is then to drive the tuning frequency down below where any of the actual frequency content exists and thereby avoid the issues with driving a subwoofer below its tuned frequency. there is a wonderful treatise on why to go LLT posted as a sticky on this site which says everything i've just said with much more detail and far more eloquently.

hope this has helped.

[bonehead848]

Basically you can choose only 2 of the 3 following options for a given sub build: Small box, low tuning, low power requirements.

The reason many choose to tune to 20 over 12 is that it the box can be much much smaller. Also consider that the human threshold for hearing is 20Hz which means nothing below 20 is audible (to most people at least). So instead of hearing any bass everything just shakes. If you can afford a huge box then build it but if not there are other options.

[Bill 3]

Thanks for the info. I have read through the LLT sticky and it is more or less the reason for my heading in this direction. I am sure it could use another re-read or two. I don't have much for size constraints, but I don't want it to get out of hand either. I can ealily do 2 30" by 7-8' sonotubes.

Currently my 15" Klipsch gets down to about 25Hz. Is there a lot of info in the 20-25Hz range that I am currently missing?

[bonehead848]

Yeah, there is definitely some great sub 25 content. But there is also a big difference in how a sub like your klipsch does 25Hz and how an rl-p 18 does 25Hz. There will be so much more pressurization of the room it will totally amaze you!

[Bent]

Also transient response (group delay) is affected by the box size, a large(er) box has increased group delay - but at reduced frequencies. It's transient response is comparable to a IB at higher frequencies but extended box loading is available to a wider frequency range.

[thxgoon]

Bill 3 wrote:

I can ealily do 2 30" by 7-8' sonotubes.

Well then you are in for some fun

If this is the case then only your budget will be your limitation as you can fit some rediculous bass in a cab that big. You will laugh at your Klipsch when you are done Pick some drivers and some power and start to model them. You'll find that there will be a tradeoff point between extension and output with lower tunes. If you are in the rehlm of LLT you will also keep the negative effects of porting out of the audible range.

[Bill 3]

I guess since it will be mostly used for HT then I will tune as low as I can afford. It takes more power to get down to the really low Hz - correct? I think I will persue it along the lines of buying the best drivers that are reasonably affordable (read bang for buck) and then an amp. I was thinking of a Behringer EP2500 for both subs to begin with (is it anywhere near enough amp for decent 18's or do I need 2). My second biggest problem (first being justifying the $) is getting enough AC power to the amp(s)

Thanks for all the responses here. I suppose I should start another thread with questions regarding speakers/amp if my searching doesn't if search doesn't answer them completely.

Bill

[SteveCallas]

Can someone explain tuning - Why choose 12Hz over 20Hz?

Several reasons, all of which are spelled out in my LLT Explained thread, but I'll summarize a few.

1) Since dvd came along, a good portion of action/adventure/sci fi/horror movies have been incorporating bass frequencies below 20hz. If you have the capability to reproduce them, they add another level of intensity to the experience.

2) If done properly, one can get all the performance benefits of using a port while eliminating just about every potential drawback. Infrasonic tuning with large diameter ports is the proper way to do this, as the "epicenter" of port use falls in a non audible range. While it is debatable whether or not the phase shift and delay in transient response that takes place at the tuning frequency is audible with very high tunes (do you hear these things in pro audio? Probably not, and they tune in the low 30hz range), it is not debatable with an infrasonic tuning, it just won't be audible. So in the end, you getting additional clean headroom, low end extension, and sensitivity with no performance drawback - this is what propels the LLT alignment over any other.

3) No need for a highpass filter, which protects a higher tuned sub from overexcursion with low frequencies, but also degrades transient performance and distortion. The lower tune protects from overexcursion, actually results in significantly reduced distortion, and while transient performance is degraded at tuning, it is not on the sam elevel of magnitude, and again, it is happening at infransonic, inaudible frequencies.