Power Compression

What is it?

What causes it?


My best guess: At low power, you add power and you get more output (x2 power = 2-3dB). Efficiency depends on box size, coil temperature, motor strength, and lots of stuff... so it eventually rolls off. After a point, the woofer can't produce much more output for a given box/port combo, no matter how much power you throw at it.

Heard the term used by Lakota and Papermaker on CA.com

I had this issue with the sub up port up box I used at finals. I had the same score when I put in 7 power master d1000's. From the 2 nsb 100's not even 1 tenth gain.

2 choices:
- battery power wasn't your bottleneck
- the added power didn't give you any more dB's


I still don't know what power compression is though... just a hypothesis with no facts or physics.

ehhhhhh


think of it like this in fish's situation
2 12's firing up well how far is the nearest flat surface pressure going out the port allows the subs to move pretty easily untill you have pressure not escaping fast enough now what would cause this back pressure on the cones not allowing them to move like they once did the more power you add the more pressure your adding to the cone as well not allowing the subs to have max excursion

this is something that draggers battle alot due to being totally sealed thats why they run alot more port than we do to eliminate this

You might make 10000 posts before you disappear again...

sanman wrote:

ehhhhhh


think of it like this in fish's situation
2 12's firing up well how far is the nearest flat surface pressure going out the port allows the subs to move pretty easily untill you have pressure not escaping fast enough now what would cause this back pressure on the cones not allowing them to move like they once did the more power you add the more pressure your adding to the cone as well not allowing the subs to have max excursion

this is something that draggers battle alot due to being totally sealed thats why they run alot more port than we do to eliminate this

X2

Thanks Sanman,

So... if the cone can't create a differential pressure (add energy to the air), the amplitude at the microphone probably will stagnate.

It happens because of the acoustic energy is greater than the surrounding air's ability to absorb. This is due to insufficient motor force, cone stiffness, or air flow. I'm sure that temperature, internal woofer losses, and poor air flow don't help either.

Gracias Senor.

you use big ass words man you forget im an uneducated army boiiii

more port could eleviate this or a bigger box

I just re-read that post... and I sound like a total nerd. I wasn't trying to show off, but that's the most accurate way I know how to say what I meant. Engineers must live with the curse of over-analyzing everything and speaking a different language from the rest of the world.


How about this for a simplified analogy - amp/sub = air pump. You input energy, and you get pressure out. A pump (or sub) with a strong motor will be capable of driving higher pressures. Pressure can build up in 2 ways: full-system pressure or from flow constrictions (in-box or out-of-box).

Full-system pressure is generally not the problem, except for Super Modified extreme vehicles. If it is... get a stronger motor. Flow constrictions are sometimes good... for loading and tuning impedance rise. In general, flow restrictions lead to inefficiency, so keep things smooth and open. Bracing, corners, and ports. Make sure there are no bottlenecks in the flow around the box. Hopefully, this will minimize the restrictions, and bring you closer to the full-system pressure limit.

PS - My uncle is about to retire from the Army. Apache helicopter maintenance and training, staff sergeant (iirc). By far one of the smartest guys I know, and he never finished college. Experience trumps education almost every time. Thanks for however many years of service you gave.

hey we got something in common i retire next july from a.d. army

chrisbaldelli wrote:

I just re-read that post... and I sound like a total nerd. I wasn't trying to show off, but that's the most accurate way I know how to say what I meant. Engineers must live with the curse of over-analyzing everything and speaking a different language from the rest of the world.


How about this for a simplified analogy - amp/sub = air pump. You input energy, and you get pressure out. A pump (or sub) with a strong motor will be capable of driving higher pressures. Pressure can build up in 2 ways: full-system pressure or from flow constrictions (in-box or out-of-box).

Full-system pressure is generally not the problem, except for Super Modified extreme vehicles. If it is... get a stronger motor. Flow constrictions are sometimes good... for loading and tuning impedance rise. In general, flow restrictions lead to inefficiency, so keep things smooth and open. Bracing, corners, and ports. Make sure there are no bottlenecks in the flow around the box. Hopefully, this will minimize the restrictions, and bring you closer to the full-system pressure limit.

PS - My uncle is about to retire from the Army. Apache helicopter maintenance and training, staff sergeant (iirc). By far one of the smartest guys I know, and he never finished college. Experience trumps education almost every time. Thanks for however many years of service you gave.

I have had more boxes then not lose when i 45 the corners. i always build it without thenn test and most always lose.. it changes the tuning but i test a wide range of frequencies to be sure and almost always lose a few tenths?

No way of knowing whether it's due to smaller box size... or different flow characteristics. I've heard that from alot of people, though.

Maybe it's similar to the tailgate myth for trucks, how you get better fuel economy with the tailgate up. Air flow may be less efficient in the corners, but it will create a pocket of turbulence that allows smooth flow around it.

Any other opinions? wild guesses?

i actually just lost a whole db by 45 and resining my box! think its more to do with tuning changes but it did go down. building a new box next week!lol