Max verses RMS

Hi. Few questions from a newbie....

Q1: I have a 12" Pioneer sub. Max = 1200W and 300W Normal. Does the 300W mean 300W RMS and therefore I should install up to a 300W RMS amp? Should / could the amp's power rating be little more / less?

Q2: When damping the enclosure (ported), should I damp the front panel too? I was thinking of sealing the inside (MDF wood) with rubberizing paint-on and slightly line and stuff the box with polyfil (to get more volume). I would then play with port length to optimize.

Q3: What is wind noise (coming from the port)? I've seen formulas to calculate lengths of ports when using 2 x ports. Reason why I'm considering 2 x ports is box design. I will not be able to use a 4" port, only 3" will fit. Also when using two ports, does it matter where I put them in relation to one another? I want to use 3" PVC for ports.

"RMS" (or more acurately "continuous" as there is no such thing as RMS power) power is the maximum sustainable rating and is based on the thermal capabilities of the voice coil components.  "Max" or "Peak" or "music" rating is the absolute maxuimum that can be withstood for a short (i.e.: on the order of 1 msec) burst and is largely determined by wire diameter and xMax.  In general, ignore "peak" or "max" ratings as they are meaningless in everyday use.

1) I must disagreee slightly with Jeff.  The "RMS" rating means you may use any amplifier up to that number safely.  You do not have to use that much, but it should represent your ceiling.  Yes, you can go above this if you design the system properly, but for the average person use the RMS number as your max.  If your woofer is rated at 300 watts RMS, then any amplifier up to that number is fine.

2) I always use polyfill inside a ported enclosure.  Line the walls loosely with it and do not cover the port.

3) Port noise can be avoided through proper port design and velocity design, or minimized by using flared or slotted ports.  Look at the port calculator link on the left side of this page.  If you use multiple ports you should place them on the same baffle (enclosure wall) and I suggest equally spaced on either side of the woofer.

That is correct, it would need to be a test tone with a 0db reference at the same time. Dyohn posed this reply it seems as the safe way to do things, and I agree with him. While 300w rms may be the "boiling point" any amp that power up to that point may be fine to use provided the gains are set properly. For the more experienced user, a amp of larger capacity may be used provided that the user knows the limits of the subs abilities, especially when it comes to heat dissipation.  The closer you run the sub to it's maximum output continuously means the sooner the sub will fail due to breaking the thermal barrier.

When I build a ported enclosure I too like to provide some kind of matting on the inside. Dacron sheet works well for this, same with a product I use called Bassline. Works wonders for ported boxes.

As far as the port goes, instead of the two 3" ports, I would head in the direction of a slot port. The area is what is important here, it must remain the same. Never ever just throw ports into a box and expect them to work.  To calculate the area of a round port is PIE * R^2. The length remains the same. So if you know the size and length of the 4" port, it will be easy to calulate a rectangular port from it.

Correct.  And by continuous I mean precisely that: an amplifier rated for 300 watts RMS means it can sustain 300 watts of output continuously at a given test tone and weighting level and remain within its rated S/N, frequency response, distortion and heat dissipation capabilities.  It has nothing to do with reproducing musc, as that is a different beast...

Thanks for chiming in Rob!

Haha, Kfr01 and I just had a lengthy discussion on another thread about how rms power should be applied to subwoofers and how overpower applies to that.

The RMS number on subs is a figment of the marketing teams imagination, with many low-end subwoofers.  A proper enclosure assumed, I have seen many low-end subs fail at or less then the rated rms. 

Ex.:  Not like the Jensen box that is sitting next to me (my brother in law gave me back the 12w0 I loaned him in it, the Jensen is his), that claims 175w rms and 525peak.  When I hooked it up in my wife’s car (amp MTX 202, her reg sub is a 10w3) we started to smell something funky after about 3 min. of hard listening.  Funny, the amp only puts out 200w bridged but his dust cap was hot so we discontinued the listening (i was just bored anyways).  Point being some manufactures lie about power handling.  On the flip, I have ran the 12w0 (rated at 125rms) on the same amp for days and never noticed any ill effects.

Personally... For reasons to do with long-term use of the driver I recommend a amp close to or at the rms power with this particular subwoofer.  Some pioneer subs are good for the true rms, some of the lowend walmart stuff is not.

Give the amp a look.  Just like subs some amps are not good for the rated power!  Oh no!  It's so subjective!  A guy came to me with a amp and was bragging about how its such a good deal cause it puts out 300x4 rms and 600x2 bridged and only costs 145$.  Wow that’s impressive!  So I asked to look at the manual, cause gosh I think these could be the wave of the future!  A look at how they rated the amp stated "rated power is all channels driven into 4ohms @1k with 15% THD and 15.9volts"  Oh, I see.. As if the two 20amp fuses where not enough. 

So his real rating was somewhere in the 50x4 range with 100 or 150 bridged.  I congratulated him on his awesome buy after explaining this and showing him the spec sheets on some of my amps.  He asked for sub recommendations, I wanted to say 'something from the pawn shop you bought this from...'  But sh*t bought now does not justify sh*t bought later.

What I'm saying is that we need to see the amp to give a true recommendation.  Depending on the amp I would say "yeah, go for more power" or "no those amps are underrated, 300w really means 300w or more".

Oh yeah, slot port that sucka.