28 m/s would be above any of the max air speeds I've seen suggested for any build.Hi,
I'm planning on building two LLT subs with 2 dayton titanic mk3 drivers I got for a great price.
I want to stick to Mr Steve Callas' specifications as much as possible but have run into an issue:
With a 6" port I have a peak airspeed of 28m/s and a port resonance of close to 250Hz. This air speed seems a bit high according to Collo's flare-it program. Will it be unacceptably noisy at max power?
With an 8" port I get a peak airspeed of 17m/s which should be noise free. The downside is the port resonance is close to 140Hz which is not a good thing according to the LLT spec.
Any advice on which of these 2 options I should go for would be appreciated.
What box volume and tuning frequency are you using?With a 6" port I have a peak airspeed of 28m/s and a port resonance of close to 250Hz.
+1.The port resonance will be there at any magnitude level whereas port chuffing and compression can only potentially happen at very high power levels, so under that logic, the higher air speed is the lesser of two evils.
Unfortunately, one of the things it will likely require him to do is use a highpass filter. With the dual Titanics and 14hz tunes, he would be fine without one. For that reason alone, I like the 14hz tunes.Ricci said:If it were me I'd increase the tune slightly from 14hz to 16 or 17hz. You'd be surprised what this increase of just a few hz in tuning can do.
Perhaps, but you must consider that if you can reach port compression before completely maxing out the driver, you aren't getting what you models predicted you will, as compression will actually limit output. So why go with a larger ported subwoofer that tends to have more design and construction work if in the end it will only give a couple db more than a sealed sub in the infrasonic range? To get your full, clean 6db advantage, you need a port that can handle all of the required air movement without too much turbulent air flow.vann_d said:My personal opinion is that many of the great subwoofer designers here at the shack tend to be overly conservative in regard to port velocity - which is not a bad thing. However, this may prevent us from implementing certain designs that, in practice, are perfectly acceptable.
The problem is not knowing at what air speed does the compression start to make a noticeable difference, measurable and noticeable are two different things.Perhaps, but you must consider that if you can reach port compression before completely maxing out the driver, you aren't getting what you models predicted you will, as compression will actually limit output.
I disagree. I don't see the extra little bit of extension preventing the need for a highpass at all. Actually the subs are IMHO more prone to bottoming in the 20-25hz range than somewhere below 14hz, especially with the 14hz tune and larger enclosure, because that area almost always has very high level signals whereas the amount of sub 14hz signals that are that LOUD is very rare. This is the area that most sub 20hz tuned long excursion drivers run into trouble NOT below tuning IMO, FWIW, etc...Unfortunately, one of the things it will likely require him to do is use a highpass filter. With the dual Titanics and 14hz tunes, he would be fine without one. For that reason alone, I like the 14hz tunes..
I'm showing reference level capability. If he corner loads both subs, then he will have headroom on top of reference level capability. There shouldn't be any trouble in the 25hz range unless he starts acting like a fool (no offense Robert :R).Ricci said:Actually the subs are IMHO more prone to bottoming in the 20-25hz range than somewhere below 14hz, especially with the 14hz tune and larger enclosure, because that area almost always has very high level signals whereas the amount of sub 14hz signals that are that LOUD is very rare. This is the area that most sub 20hz tuned long excursion drivers run into trouble NOT below tuning IMO, FWIW, etc...
Check the LLT Explained, it's all in there. A <15hz tune with reference level capability will keep you quite safe.Robert said:One thing I don't understand is why a highpass is not necessary when I tune to 14Hz and it is when tuned higher. Why if there is content way below that on certain scenes in movies would the driver be protected by the LLT design?
