Can you have too much?

[shadyJ]

Hey what shape did they say helps reduce chuffing the most? I wonder if it's those slotted ports like the Captivators have

Here is the paper. It suggests that a flared ported with a tapered shape is very good for reducing port turbulence, with a large taper on the inlet side and a narrow taper on the outlet side. Similar conclusions are reached in this paper:
"A significant reduction in the vortex shedding can be
obtained by gradually widening the port cross section toward
both port ends to obtain a converging–diverging port cross
section and rounding both port edges."
These papers only study round ports. My guess is that the same tapering angle would hold true for slot ports. I am told that round ports are better for reducing turbulence than slot ports, as a general geometry, but I am sure that a large slot port will still be much better than an equivalently smaller round port.

 

[Verdinut]

IMO, there has been to some extent too much emphasis on port turbulence noise. Port turbulence noise will only happen in situations when the sub is driven to low frequency extremes and at very high SPL.

In most situations in a home cinema or music environment, port turbulence does not happen unless the total tube port area is relatively small in comparison with the cone area of the subwoofer.

For example, if you have a 15" sub with a total port area of at least 25 square inches in an average listening room size, you should not expect any turbulence noise, unless you were driving the sub to a high SPL at frequencies below 20 Hz and even so. Some experts even do not consider this as a problem as it is effectively masked by program material. When the port is at the back of the enclosure, there is even more reason not to worry about it.

 

[ryanosaur]

The 'Harmonic Limit' cell in my CEA-2010 tables are what kind of distortion that is occurring which is limiting the test from achieving higher SPL readings. To get a better sense of what that means and why that matters, read the section from this page that is subtitled 'A More Sensible Metric of Distortion' which discusses how and why the CEA committee established those distortion thresholds for the CEA-2010 testing standard (what is written there is not the whole story, btw, but it is a good primer).

Very nice, man. That old acoustics class comes crashing back a bit reading that. Thank you!

Beyond that, now I have a better understanding of how to read those CEA charts. Its one thing to be told "higher is better," but the context is everything.

So between all of this, I now see a measure for dynamic SPL (in a certain manner... as you said the complexities of the music v. test tone in an less-or-un-controlled environment...) and then the stress test of a continuous tone at high SPL. (As you said, a pedal note on organ is exactly that!)

(And is the long term output sweep similar to the RMS testing speakers go through?)

Seriously, thank you!!! Shady, you and @Steve81 are really being helpful in helping educate me more here!

 

[shadyJ]

(And is the long term output sweep similar to the RMS testing speakers go through?)

Not quite the same. Long term compression sweeps are as loud as the subwoofer can get at a steady level. But subwoofers are generally self-amplified devices that have all kinds of sophisticated electronics and circuitry in them, with all kinds of filters and protection, so how they perform at maximum levels will be different than how passive devices perform at very high levels. The RMS power handling that passive loudspeakers have is a different kind of specification. It is a general guideline to how much power can be given to the speakers before it risks destroying the speaker. We had a recent discussion about that subject that started here in this thread.

 

[Danzilla31]

Here is the paper. It suggests that a flared ported with a tapered shape is very good for reducing port turbulence, with a large taper on the inlet side and a narrow taper on the outlet side. Similar conclusions are reached in this paper:
"A significant reduction in the vortex shedding can be
obtained by gradually widening the port cross section toward
both port ends to obtain a converging–diverging port cross
section and rounding both port edges."
These papers only study round ports. My guess is that the same tapering angle would hold true for slot ports. I am told that round ports are better for reducing turbulence than slot ports, as a general geometry, but I am sure that a large slot port will still be much better than an equivalently smaller round port.

Hey on a side note I reran Audyssey while I'm stuck in the house with my back healing and ran the PB 4000's in 3 port mode standard

Man I just can't get over how impressed I am with these sub's. I like both modes standard and extended. I think I'll end up running them in 3 port mode mostly. But when I get a deep bass monster movie or horror flicks stuff like that then I'll go with extended mode. But regular movies and most music I just really enjoy the standard mode on.

Just super awesome subs man

 

[TechHDS]

Ok... been trying to learn more about sub performance, and I guess where i'm getting stumped is understanding and interpreting the potential output from a sub. Might you guys help me with that, please?

Hey there new members welcome to AH! Be careful what you ask for on AH! Great bunch of ole timers on here. Know what You are asking about first and foremost!! Cause these old Timers on here do know How to play Hard Balled! One of two things, Either you’ll get what you ask for in response or 2. Or you’ll end up with a response of Scabs with a “Sketchy”ness, of Certainty your Guaranteed to be pleased with the results
Enjoy! Your Hobby!!! I know I did from the very begain!! Wow I never knew this Audio, chatroom was Sooo much Fun! But it was much easyer back in the 70’s 80’s with No internet!! Back than with this hobby the only way you could get Any Kind of (into). was you went to someone’s “Homie” walked in and said, I’ll Show You Mine! If You show Me Yours? If that didn’t work? You could use, Want Two go half in on a Baby? Sub,? Usually worked everytime with a double blind test! Once the Light Bulb went out!

Sketchiness results!! Guaranteed Lolo!


Mike

 

[TechHDS]

Very nice, man. That old acoustics class comes crashing back a bit reading that. Thank you!

Beyond that, now I have a better understanding of how to read those CEA charts. Its one thing to be told "higher is better," but the context is everything.

So between all of this, I now see a measure for dynamic SPL (in a certain manner... as you said the complexities of the music v. test tone in an less-or-un-controlled environment...) and then the stress test of a continuous tone at high SPL. (As you said, a pedal note on organ is exactly that!)

(And is the long term output sweep similar to the RMS testing speakers go through?)

Seriously, thank you!!! Shady, you and @Steve81 are really being helpful in helping educate me more here!

You just Hit that old Pariva statement of anything out of “ Context” can be Very subjective!! Especially with this Hobby!! Can be No end in if your Shortsighted. Ask and You Shall Receive.

Mike

 

[ryanosaur]

Thank you everybody that helped me out here. The decision was hard, but Black Friday sales made it easier. I just jumped on the Outlaw sale for 2 X-13s! Even if I find I need to upgrade, these will hold down the fort long enough. Or when the lady decides its time to upgrade the old HTIB, I can move these out there and order up some next-level sh!t for me.

 

[Danzilla31]

Thank you everybody that helped me out here. The decision was hard, but Black Friday sales made it easier. I just jumped on the Outlaw sale for 2 X-13s! Even if I find I need to upgrade, these will hold down the fort long enough. Or when the lady decides its time to upgrade the old HTIB, I can move these out there and order up some next-level sh!t for me.

In that room that you ended up in those X-13's will be way more then enough. Your going to be very very happy. And such a sweet ass deal too. Man you gotta send us some pics when they come in hell you definetly gotta send us pics when the speakers come in for sure! Congratulations!

 

[ryanosaur]

All right. the receiver is finally back from warranty service... seems to be working. Just have a little pair of Rat Shack Linaeum tweeter bookshelves hooked up to test until Dennis sends my speakers...
Oh, that pair, and my X-13s.
Oh yes.
I asked... can you have too much? My answer is yes. And.
May I have some more please!
Just running sealed right now to test them out, but Wow, Mom, Wow! (I think there's a raunchy joke in there somewhere.)
Stoked!

Thanks again, everybody!