![]() ![]() Unfortuantely, that means energy storage, and some compromise of the group delay and transient response. ![]() The simplest and easist thing to do is a nice sealed box or IB - they have excellent time domain characteristics without doing hardly any work on the designers part (as long as you don't pick a driver with screwy T/S parameters), but they're both limited in maximum acoustical output by the swept volume issues - Xmax time Sd.īass reflex enclosures (originally known as Helmhotz resonantors, after their inventor) all use a reonant box system to augment the rear wave. You're on the right track here as I think your're discovering, sub design is all about traeoffs, including box size, power handling, and especially outright power handling at very low frequencies. Is what I am doing by setting a point where I want to see excursion limitations and basing my maximum wattage and thus SPL on this point valid at all? two tempests in an IB with 250 watts of power) BUT if you look at the excursion charts, one of those two might have more excursion left so if you adjust the watts until they run out of steam at the same frequency, one of the setups gains an advantage in output. Quite a few driver combinations will give the exact same output given the same total power (i.e. Since that original post, I've been modeling different drivers for IBs and have run accross the same concept. So any way, I saved off the excursion graphs and then I made a comparison of my current sub with 210 watts where the excursion limit is reached at 15 hz and a ported sub in the same box where the excursion limit is reached at 15 hz so that you can see the net effect of porting the box AND gaining power handling.ĭoes this make sense, or am I making incorrect assumptions? I could hit 400 watts and still have the excursion limit be reached at 15hz. With a ported sub, there is a big dip in excursion around the tuning point, which means I can add more power. The excursion graph of this sealed sub ramps up exponentially as frequency drops, so as I add more power, it causes the sub to bottom out at exponentially higher frequencies. See, with a simple 200 watts, my sealed design would reach its excursion limit at 15hz. Frequency graphs were almost the same, given the same amount of power) how could I use the extra available excursion provided in the 35-15hz range to my advantage. So I decided what I would do is determine that IF I ported the same size box (even though the SPL v. ![]() But after the suggestion about looking at woofer excursion I decided to play around with wattage, as the woffer excursion charts showed that not ALL things are as simple as looking at the frequency response chart. This is all in theory as I've not decided whether to port this box or build a new one or leave it alone. So, after fiddling around a bunch more, I present this concept that I have arrived at for anyone to validate if they choose. Holy Smokes! From that 30hz point to the tuning point, the excursion of the woofer drops, leaving me tons of headroom (of course it rises quickly again below the tuning point, but so does the sealed version) I've been introduced to a concept that I never even considered before. It was then pointed out that if I model that port in my current box then I should look at the woofer excursion charts for sealed vs. Basically I could gain 1-2 dB from 30hz to the tuning point. The first thing I noticed is that if I port my current box to a reasonable tuning point I get almost no increase in output accross any significant bandwidth. I've been running all kinds of models through it since then. OK, I posted about porting my 121L sealed Tempest and eventially got directed to checking out Unibox, which I did. Any way, here, esentially, was my question. No beef about it, just the plain fact that I got no response and I'm still curious. So Is started a new thread at the other forum with some questions and trying to confirm my understanding but got no response. Any way, I was introduced to Unibox and spent about a week figuring out how it works. I was posting on another forum about porting my current sub just to play around and learn because the sub box will be tossed in the next six months when I move and the driver either get sold, given away to my brother (if I'm really nice) or used in the IB. ![]()
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