not again!! port ??'s

At tuning frequency the port makes almost all the sound, so it needs to be large enough. With small ports, we get port noise, air traveling in and out at very high speeds.

The thing is, we don't care about air. Its interfering with the sound that we want to come out of the port.

I use a general rule, for 1 10-inch woofer, I want a 3-inch port minimum A 4-inch would be prefered. For a single 12-inch, the absolute minimum size would be a 4-inch port with a 6-inch being recommended. Many times the box size determines the size of the port. So we need to be realistic.

 

Larger is always better, again be reasonable. A 6-inch port will NOT fit in your 1.9 cu ft box. A 4-inch would be a good choice for your box.

Your right, you cannot hear port noise if the box is in the trunk. But Port noise is air rushing in and out of the port at very high speeds. It interferes with the sound we want coming out of the port. But lets think about it another way.

Your in a small row boat, (the boat is the sound) and you need to cross a river. (the river current represents the air velocity in the port). If the river has a very slow current, rowing across is no problem. If the current is very fast, rowing across becomes very difficult.

In a port the problem is worse. The air in the port is changing directions very rapidly. Imagine crossing that same river if the current changes directions every second.

So larger will have an improvement over small

My recomendation on tuning (if you want louder) would be get closer to 38-40Hz. The f3 point (how low it hits) will stay the same.

The biggest misconception I see is that many people believe that tuning lower causes it to hit lower. Thats so wrong. Box size effects f3 point alot more than tuning ever will.

 

i thought it was also to have a flatter response across the board.

 

Yes, by tuning lower the response is flatter. So if I'm concerned with SQ, I will typically tune a little lower. But if I wanna get the attention of everyone around me, I'm gonna tune Higher.

But also if I'm concered with SQ, I would use a sealed box.

In any case, if my f3 point is 36Hz and I'm tuned to 40 HZ, retuning to 30 will only drop my f3 point to maybe 35, if I'm lucky.

 

Manufactures recommend low tuning to protect poorly made woofers. To far below tuning frequency, woofer excursion increases alot and can damage the woofer. Many manufactures advertise really high Xmax values, when in reality they are barely able to handle a third of that advertised excursion. By lowering the tuning frequency, excursion decreases. Cheaply made woofer lives.

So How High can we safely tune? Be cautious.
(SPL for this daily driver was 158.2)


I Built this many years ago, it was tuned to around 50 to 55Hz. The owner listened to it every day. He played the same music you and I listen to. He did not have any problem putting in a 30Hz test signal. We NEVER had to warranty a woofer for excursion problems, in fact we never had to warranty a woofer for any problem.

Now do I recommend you tune that high, absolutely NOT. But tuning around 40 is perfectly safe for any well built woofer.

By the way, those ports measure 13 x 13-inches