VERY interesting Type-r info....

mebcop
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Well, I've been doing a LOT of reading trying to decide if I wanna go 2 type-r 10's ported or 3 sealed.... Seemed like everyone I had talked to said "PORT EM", but then I ran across this post on another forum... VERY interesting....

Here's a sophisticated modeling of your woofer, based on the Thiel-Small parameters found in the owner's manual for your woofer. Let me explain what it it telling you.

 

Firstly, you can see the root of the manufacturer's recommendation. The optimal (Qtc=.707, or B4 alignment) for the sealed enclosure occurs at ~.67 cubic feet. And this is without any enclosure dampening material. In reality, if you fill the box with the typical fiberfill dampening material (pillow stuffing), the optimal sealed box occurs at ~.56 cubic feet. Even the manufacturer's .75 cubic feet recommendation is actually a bit large for this woofer, if the published speaker parameters are really accurate.

 

Look at the sealed plot on the graphs (the yellow lines). This is what they should look like if you want it to sound good. Notice that there are two yellow lines on the plot, diverging at about 80Hz. The one that extends almost perfectly linearly down to 5Hz has the effect of the being placed in the car's interior added in. Putting a subwoofer in the car changes its response as compared to the other yellow line, which is the response achieved in free air. Your actual in-car response will look a lot more like the flat line rather than the free-air response. The low frequencies are reinforced by the 'room gain' of the car's interior. This whole scenario is optimal, and you simply can't fix what isn't broken by increasing the box size. Notice how well controlled the phase response is, and how good the group delay is--in that it lies at low levels (6ms or less) and is fairly constant over the operating range of the woofer.

 

The red lines are the plot of the optimal ported box. Again, we can see the root of the manufacturer's ported box recommendation (1.3 cubic foot) as this is almost exactly what is optimal with no enclosure dampening. But the key thing to realize here, and what the people who are recommending you use a ported enclosure are omitting in their advice, is that this is really a sealed box woofer. Look how bloated the low-end becomes once room gain is added in. And more importantly, look at how the phase response and especially the group delay tear up at low frequencies. This is indicating that the speaker will be underdampened at low frequencies in a ported box, even one designed as expertly as possible. The low-frequency output will definitely increase, but it will be out of porportion with the output at higher frequencies, and the bass will be loose and flabby. In other words, sound quality will be significantly degraded, just as in the case where you arbitrarily increase the sealed box's volume big-time. Fortunately this woofer's design is versatile enough that your power-handling at low frequencies is still adequate to prevent woofer damage, but the sound quality will indeed go to crap. A true 'boom box' effect.

 

You have a small-box woofer. And you have a sealed-box woofer. Wanting more thump cannot change this. If you're running the .75 cubic foot sealed design, you've already done the best you can with this driver. Understand that the same things that make a 10" driver tune optimally in this small of a sealed box also kill the efficiency. Your real problem here is you just don't have enough output total, rather than you don't have enough low bass. At your level of experience you are prone to make this error--thinking if that the problem is not enough down low rather than realizing that you just don't have enough period.

 

The cure for this is indeed easy, and you yourself proposed this. The second woofer. Put the second woofer in it's own .75 cubic foot enclosure, and run them both. You'll find you've got the thump you're looking for, and you wont trade all your sound quality for it--assuming you double your amplifier power at the same time. If each of the two woofers ends up only having half the power that you were putting on the single woofer, you indeed aren't gaining anything other than a bit of sound quality due to the reduction in woofer excursion.

 

I hope you can see that this isn't as simple an endeavor as many assume. And also, I hope it is clear that the common advice as delivered elsewhere in this thread really isn't a whole lot more insightful than your original use of the box program. The cures are almost always more cone area and/or more amplifier power, rather than slanting the enclosure design to unproductive extremes or expecting a sealed-box design to magically become a ported-box one because you want more.

 

Also understand that several of the 20 years I mentioned in my previous post were spent working for Rockford Fosgate. The technical training I received there, along with 20 years of buying woofers, testing them to derive their actual Thiel-Small paramaters, building multiple enclosures for each, and testing them in-car has given me an unusual degree of expertise where subwoofer design is concerned. I also hold a degree in electrical engineering (amongst others). I gladly share my experience as not everyone has 20 years to spare, and please don't take it personally if what I bring to the table puts the commonly held 'understanding' of these topics and the typically-encountered advice in a bad light. I'm simply not just 'some guy posting on msg boards'. I know these topics inside-out, and my sincerest desire is to provide you with the benefits of all the years I've devoted to learning enough to make these decisions artfully and produce the best possible results.

This guy sure seems to know what he's talking about!!!

 
i stopped reading after the first paragraph, still gettin louder ported..all ive ever really ran the most in my car was r's and nothing was better then porting them and tuning the box between 30-34 hz to me

 
On this forum most everyone seem to care about getting loud from what I see, so although some of us may see the significance in the thread most will say port em!!! and call it a day

 
I've come to the conclusion that a lot of people on here don't care how it sounds, as long as its LOUD.... Sorry, not me

Who would you listen to, a guy who OBVIOUSLY knows what he's talking about, or some random guy on a forum saying "I don't know why, just port em dude"

I guess I'd rather run more subs with a ton of power in an enclosure that actually sounds decent....

 
On this forum most everyone seem to care about getting loud from what I see, so although some of us may see the significance in the thread most will say port em!!! and call it a day
They get extremely loud for the money.

Its not that no one cares they are for sealed boxes, it is those that use sealed boxes do not run type rs.

 
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