M-21 Giveaway Build Pics

[gmichael]

corock wrote:

oops! I don't live in a mansion. That's cubic feet not sq ft.

Thank you. I was feeling mighty small....

[gperkins_1973]

And if your worried about size then here's a 10 cu ft ported sub. Now try to imagine two of these bad boys.

Believe me two ported subs have much more impact than one. I was really surprised how much better the bass sounded. Much deeper and much more sure footed and really clean.

Mmmm Yum Yum.

cheers

Graham

[Ryan Anderson]

fackamato wrote:

I don't know if a sealed 21 will be enough for that room. Maybe two ported 18s?

the guy won the 21" so this all has to pertain to the 21"

[corock]

from the modelling I did, it looks like I'll have to keep the amp down around 1000W if I want to use any eq. How do companies like Paradigm use big 3000W amps on sealed subs?

[gperkins_1973]

Oops good point.

Here you go with the 21" sub. Both subs with 2000 watts. Sealed not going over max excrusion and the ported not until 12hz.

Guess again, which is the ported.

Tune this to 14.5hz and you will still see a gain with the ported. Unless you are going to listen or watch your stuff at reference you won't need a hpf but even with a hpf you will still be up on the sealed.

The first graph is without a hpf and the second with.

cheers

graham

[Ryan Anderson]

graham, my friend, I fear this battle and war to be lost. The only way for anyone to grasp the truth is experience. Until they themselves simply try it, all the graphs and plots and verbage will go nowhere. No one is going to stick a port in a box with a 21.

corock, I think you should aim for a 3000 watt amp. The sub I'm told loves 3000 watts... maybe 8 cubes is too large to use all 3000 watts, but that makes room for dynamics...headroom... effortlessness... ease of wear and tear on equipment. I wouldn't sell myself short with just 1000 watts even if plotting suggests it to be all you need.

[corock]

Okay, lets go away from simulation and take a look at some real life results. Here are the measurements for one of my PB-13U's.

First ported and tuned to 15hz


Then sealed


I'm not using any eq on either of these
Thoughts?

[corock]

gperkins, when I try to port an 8 cu ft box I end up with a 57" port, and how did you use 2000W sealed without getting the excursion to high? I might be doing something wrong with WinISD.

[gperkins_1973]

When doing a ported you need to do a slot port to get that size port I quoted and not a round one as it will be long. The 21" sealed is fine in a 8 cu ft box and give a qtc of 0.760. Larger than 8 cu ft will go over max excursion and will lower qtc giving you better low end and smaller box will give you less excursion but higher qtc (tighter bass, less low end). Hence the reason going ported to give you more.

I will drop you some more diagrams tonight but it depends what you want your subs for.

cheers

Graham

[corock]

I use my system for music, movies and tv. Music will be the emphasis of its use though. I like all music, but lean toward hip hop, pop, rap, etc with lots of artificial bass. That's definately what I listen to if I got the volume cranked up.

This build will be about compromise, as is all builds I guess. Aethetics do play a big part of my decision making and I'm not a big fan of slotted ports. From the in-room measurements of my SVS it looks like I'm getting pretty good results down to 15hz out of a sealed box. Sure, the ported box has more spl from 15-20hz but I don't think I'm willing to give up my sealed box design ideas for it.

Kevin H. says not to bother with any less than 2000W to power this thing. The amp has to be black so that rules out the 2700W Face Audio amp. I was thinking of the Behringer EP4000. That's overkill but I guess I don't have to use all that power.