Change my mind-Ported subs cant touch sealed - Page 2 - AVS Forum | Home Theater Discussions And Reviews
Forum Jump: 
 116Likes
Reply
 
Thread Tools
post #31 of 201 Old 07-19-2019, 06:59 PM
Advanced Member
 
johnplayerson's Avatar
 
Join Date: Feb 2008
Location: Canada
Posts: 664
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 300 Post(s)
Liked: 79
Quote:
Originally Posted by Remy.Alexander View Post
Here is model - Orange is how I run my sealed now other is massive 13ft with 27HZ HPF because excursion is evil with 500W, If i drop to 250W SPL sucks vs sealed

I dont want to go W or D, so H is the way. max I think 6'.
The size of your room is screwing up the whole situation. Mine is 14 by 11 which does'nt change much from yours but the walls and floor and even ceiling are very good for sound. When I ran all sealed, SOUND QUALITY , in all respects kicks ass compared to ported. Spl wise, with ported you can get more at a very narrow frequency range, but this of course is by no means anywhere near flat response is it? The main difference with ported, is that I can scare myself out of my seat at times, even do a few hair tricks, but this becomes an SPL competition rather than meaningful sound in my opinion.

https://discuss.avscience.com/index.php?topic=459.60
A Good amplifier requires a adequate power supply, It does not matter what the amplifier is capable of if the power supply will not provide the power required. Most amplifiers have under rated power supplies. It is up to you to make sure you get the ones that are least under rated if at all.
johnplayerson is offline  
Sponsored Links
Advertisement
 
post #32 of 201 Old 07-20-2019, 09:52 AM
AVS Forum Addicted Member
 
MKtheater's Avatar
 
Join Date: Jul 2006
Location: New Hartford, NY
Posts: 18,627
Mentioned: 135 Post(s)
Tagged: 0 Thread(s)
Quoted: 2495 Post(s)
Liked: 2551
Quote:
Originally Posted by BassThatHz View Post
So says the guy who switches box-types faster than some switch underwears...
So says the guy who switched over to an IB (and now enjoys that config better, as per his own words.) hehe!
I may be a mandela alzheimer recoveree, but I don't forget THAT easily (yet!)

Many moons ago, when you said your current config is "better", care to elaborate on that? If LLT is so spectacular with the SPL etc, then why ever switch? You are making us second-guess statements here. hehe!
I have to keep you on your toes. My port was too big for my xxx18s, so when I sealed them the tactile response and spl shot right up. I was very impressed, however, I of course never leave well enough alone, measured the difference and the IB will LT indeed brings the tactile experience and spl of the ported but at a cost. That cost is 6 times more distortion which I just learned. That higher distortion seems like more bass and actually shakes more things. I went from 2% THD at 10hz to 12%THD at the same levels. Now this could be solved with adding more drivers, which I am, but I am builing 4 sonosubs again, and this time I am measuring them. They will be tuned to where I will get the same effects on Lone survivor as sealed and more above. Hopefully my new room will have the same gain and extension as previously, it was my one advantage I had. I will be comparing a UM18 to my xxx18 very soon, betting the UM18 is exactly half of the RE in proper sized 22 cubic foot boxes.

Now, having said that, just based on facts, sealed is better. You just buy enough drivers for low distortion and spl. It will give you full band everytime. Everything else is a compromise. The compromise to sealed is cost.
Will P likes this.

Nothing right now
MKtheater is online now  
post #33 of 201 Old 07-20-2019, 10:36 AM - Thread Starter
Senior Member
 
Join Date: Aug 2018
Posts: 371
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 173 Post(s)
Liked: 54
Quote:
Originally Posted by drewp29 View Post
I built a Cinema F20 for my 390HF as well, and am pumping at least 900W into it. I don't run a high pass (currently), and that little driver hasn't given up the ghost yet! Plus I tickle the clip light on my PLX3002 regularly, lol. IMHO, the F20 is the best thing to use a 390HF in if you can deal with the size of the box. I considered building a 2nd F20, but am hunting for single digits now, and attempting to test the structural integrity of my house - according to the girlfriend anyway...



I was about to pull the trigger and try the F20, but 20cubes YIKES-Stupidly worked in the massive heat yesterday starting on dual 6.6(ish). Saw was not cutting well so I ended up with 20x19.5x64. Not sure the tune yet- Again somehow i got bad cuts so i had to lob off 1" on bottom of faces so ill turn that into slot port.
1"X18"X??



Ill give ported a shot- Winisd showed excursion was way eaier to tame with 6ish cubes and realistically they are just 14" taller then my Sealed ones.
Attached Thumbnails
Click image for larger version

Name:	67267780_453988902089555_4502439552408879104_n.jpg
Views:	45
Size:	880.4 KB
ID:	2592802  
drewp29 and 18Hurts like this.
Remy.Alexander is offline  
Sponsored Links
Advertisement
 
post #34 of 201 Old 07-20-2019, 11:53 AM
AVS Forum Addicted Member
 
MKtheater's Avatar
 
Join Date: Jul 2006
Location: New Hartford, NY
Posts: 18,627
Mentioned: 135 Post(s)
Tagged: 0 Thread(s)
Quoted: 2495 Post(s)
Liked: 2551
BTH,
Guess what I just changed my mine again. Why? Sources. I can locally buy sonotubes which are 4 feet tall and 24 inches round, much too small to port. I am going to seal them up and use 4 in my 1500 cubic foot space, LT as well.
Remy.Alexander likes this.

Nothing right now
MKtheater is online now  
post #35 of 201 Old 07-20-2019, 03:26 PM - Thread Starter
Senior Member
 
Join Date: Aug 2018
Posts: 371
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 173 Post(s)
Liked: 54
Quote:
Originally Posted by MKtheater View Post
BTH,
Guess what I just changed my mine again. Why? Sources. I can locally buy sonotubes which are 4 feet tall and 24 inches round, much too small to port. I am going to seal them up and use 4 in my 1500 cubic foot space, LT as well.



That sounds awesome- Dont give me ideas- I have already changed cabs 3 times. This will be my last lol- if these dont work out ill go back to the sealed and just buy two more woofers when i can
Remy.Alexander is offline  
post #36 of 201 Old 07-20-2019, 04:07 PM
AVS Forum Addicted Member
 
MKtheater's Avatar
 
Join Date: Jul 2006
Location: New Hartford, NY
Posts: 18,627
Mentioned: 135 Post(s)
Tagged: 0 Thread(s)
Quoted: 2495 Post(s)
Liked: 2551
Sealed only matches ported when you have enough drivers for spl, low distortion, and a LT engaged. If you have that it is better than ported even tuned at 10hz or lower. IMHO it is because there is no drop off below a tune with sealed. I like my ULF. If ULF is not wanted then it makes sense to port, but I would do a LLT at minimum.
Will P likes this.

Nothing right now
MKtheater is online now  
post #37 of 201 Old 07-21-2019, 11:37 AM
AVS Forum Special Member
 
AlphaPie's Avatar
 
Join Date: May 2013
Posts: 1,340
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 233 Post(s)
Liked: 422
Quote:
Originally Posted by zora View Post
Get multiples of the $29 JBL driver on sale now. Extension & cheap.
What jbl model?

Pioneer Elite SC-85 | RBH R-515 LCR | Morel Surrounds | DIY 12" Infinity Subs w/ Inuke 3000

2 CH - Realistic STA-2100D | Realistic Optimus 5-B (restored) | Marantz AT 6 | Sony CDP-CE375
AlphaPie is offline  
post #38 of 201 Old 07-21-2019, 11:49 AM
AVS Forum Special Member
 
zora's Avatar
 
Join Date: Nov 2003
Location: Walla Walla, WA
Posts: 1,058
Mentioned: 2 Post(s)
Tagged: 1 Thread(s)
Quoted: 103 Post(s)
Liked: 82
Quote:
Originally Posted by AlphaPie View Post
What jbl model?
The JBL GX1200 was for sale at Best Buy, but I think you missed the sale.
zora is online now  
post #39 of 201 Old 07-21-2019, 02:17 PM
AVS Forum Special Member
 
AlphaPie's Avatar
 
Join Date: May 2013
Posts: 1,340
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 233 Post(s)
Liked: 422
Quote:
Originally Posted by zora View Post
The JBL GX1200 was for sale at Best Buy, but I think you missed the sale.
Its freq response is kind of high anyway I suppose.

Pioneer Elite SC-85 | RBH R-515 LCR | Morel Surrounds | DIY 12" Infinity Subs w/ Inuke 3000

2 CH - Realistic STA-2100D | Realistic Optimus 5-B (restored) | Marantz AT 6 | Sony CDP-CE375
AlphaPie is offline  
post #40 of 201 Old 07-22-2019, 06:12 AM
Advanced Member
 
Jedi940's Avatar
 
Join Date: Dec 2009
Location: Northwest Ohio
Posts: 509
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 286 Post(s)
Liked: 202
Quote:
Originally Posted by Remy.Alexander View Post
I was about to pull the trigger and try the F20, but 20cubes YIKES-Stupidly worked in the massive heat yesterday starting on dual 6.6(ish). Saw was not cutting well so I ended up with 20x19.5x64. Not sure the tune yet- Again somehow i got bad cuts so i had to lob off 1" on bottom of faces so ill turn that into slot port.
1"X18"X??



Ill give ported a shot- Winisd showed excursion was way eaier to tame with 6ish cubes and realistically they are just 14" taller then my Sealed ones.
Be sure to check port velocity in WinISD. 1" isn't very tall for a port and may cause port noise.
Jedi940 is offline  
post #41 of 201 Old 07-22-2019, 07:07 AM
AVS Forum Addicted Member
 
MKtheater's Avatar
 
Join Date: Jul 2006
Location: New Hartford, NY
Posts: 18,627
Mentioned: 135 Post(s)
Tagged: 0 Thread(s)
Quoted: 2495 Post(s)
Liked: 2551
In my room I could hear port noise with 44 m/s(estimated), I could not hear it at 29 m/s. This was at 125+ dB.

Nothing right now
MKtheater is online now  
post #42 of 201 Old 07-22-2019, 09:28 AM - Thread Starter
Senior Member
 
Join Date: Aug 2018
Posts: 371
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 173 Post(s)
Liked: 54
Quote:
Originally Posted by Jedi940 View Post
Be sure to check port velocity in WinISD. 1" isn't very tall for a port and may cause port noise.



WinISD showing about 20ms max with 1"X18"X20" slot. I went with 1" because any taller and port would be massive. Going 2" drops to 10Ms but doubles the port length chewing up my volume
Jedi940 likes this.
Remy.Alexander is offline  
post #43 of 201 Old 07-23-2019, 01:40 PM - Thread Starter
Senior Member
 
Join Date: Aug 2018
Posts: 371
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 173 Post(s)
Liked: 54
Not Proud of my bracing but it'll do- Slapped on "blank" second baffle this morning-(Forgot snap a pic) Im guesstimating after woofer theyll be 6.0ft even


Yes there is a **** ton of glue...Oddly it seems this 3/4" mdf is garbage. Like this morning i went out to the garage and one of the cabs port opening was dislodged on the corner, and the mdf seems more frail then normal. So i lathered the glue on.



I tied the front and two sides with 1." thick lumber scrap and used lots of glue and 1.5" heavy duty staples. the other two braces where the spots my 220lbs was able to flex the cabs- They should be tuned to about 17/18HZ, ill flush out the second baffle tomorrow hopefully get the hardware to mount them to work and slap on the back of the cab
Attached Thumbnails
Click image for larger version

Name:	67384908_329164088037856_935816340927676416_n.jpg
Views:	60
Size:	1.24 MB
ID:	2593744  
Remy.Alexander is offline  
post #44 of 201 Old 07-23-2019, 01:42 PM
AVS Forum Addicted Member
 
notnyt's Avatar
 
Join Date: Dec 2008
Location: Long Island, NY
Posts: 10,273
Mentioned: 322 Post(s)
Tagged: 0 Thread(s)
Quoted: 3790 Post(s)
Liked: 3759
notnyt is offline  
post #45 of 201 Old 07-23-2019, 02:10 PM
Advanced Member
 
lknhomeaudio's Avatar
 
Join Date: Jan 2012
Posts: 677
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 287 Post(s)
Liked: 148
Change my mind - OP is modeling subs wrong.
lknhomeaudio is offline  
post #46 of 201 Old 07-23-2019, 02:17 PM - Thread Starter
Senior Member
 
Join Date: Aug 2018
Posts: 371
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 173 Post(s)
Liked: 54
Quote:
Originally Posted by notnyt View Post
you need much more bracing

Why? then I have no internal volume. I thought the point of bracing was to eliminate flex? I weight 220lbs and i put my weight into the sides and could barely move them. I stood on the front this morning with the same results.



only part not braced is top to anywhere. When I get the woofers hardware sorted out ill probably put another brace on the top going from front to back
Remy.Alexander is offline  
post #47 of 201 Old 07-23-2019, 02:20 PM
AVS Forum Addicted Member
 
notnyt's Avatar
 
Join Date: Dec 2008
Location: Long Island, NY
Posts: 10,273
Mentioned: 322 Post(s)
Tagged: 0 Thread(s)
Quoted: 3790 Post(s)
Liked: 3759
Quote:
Originally Posted by Remy.Alexander View Post
Why? then I have no internal volume. I thought the point of bracing was to eliminate flex? I weight 220lbs and i put my weight into the sides and could barely move them. I stood on the front this morning with the same results.

only part not braced is top to anywhere. When I get the woofers hardware sorted out ill probably put another brace on the top going from front to back

Not going to waste time extolling the necessities of bracing, there are lots of posts here that explain it thoroughly. Short answer is that it's not just flex, it's resonances. Also, "barely moving" is still moving.

Your cabinet is severely under braced. Ideally you do not want any point on a panel further than 6" from a corner or a brace.
notnyt is offline  
post #48 of 201 Old 07-23-2019, 02:33 PM
AVS Forum Special Member
 
Join Date: Sep 2016
Posts: 1,162
Mentioned: 20 Post(s)
Tagged: 0 Thread(s)
Quoted: 438 Post(s)
Liked: 362
Quote:
Originally Posted by Remy.Alexander View Post
Why? then I have no internal volume. I thought the point of bracing was to eliminate flex? I weight 220lbs and i put my weight into the sides and could barely move them. I stood on the front this morning with the same results.



only part not braced is top to anywhere. When I get the woofers hardware sorted out ill probably put another brace on the top going from front to back
A panel can resonate loudly at less than a 1/4 mm movement.

Imagine how loud a speaker gets and has no noticeable movement. Stiffness is a part of it but you have to make sure the stiffness is equally distributed. 1/2' dowel rods don't take up much space and make great cross braces. Angle bracing is good for tough spots you can't get cross bracing in.

Not's recommendation for 6" spacing is standard although not a strict rule. Still its pretty smart spacing in big boxes such as subs.
notfastenough and Will P like this.
Trimlock is offline  
post #49 of 201 Old 07-23-2019, 02:35 PM - Thread Starter
Senior Member
 
Join Date: Aug 2018
Posts: 371
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 173 Post(s)
Liked: 54
Quote:
Originally Posted by lknhomeaudio View Post
Change my mind - OP is modeling subs wrong.



How so? I was modeling the size I wanted for sealed and ported.

Last edited by Remy.Alexander; 07-23-2019 at 02:39 PM.
Remy.Alexander is offline  
post #50 of 201 Old 07-23-2019, 03:51 PM
Senior Member
 
Join Date: Dec 2018
Posts: 219
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 149 Post(s)
Liked: 68
Change my mind-Ported subs cant touch sealed

I have a bracing question. Just in general whule were discussing it. Pro Subs, even the high end brands and models typically brace around the exterior with like 1x1 or 1x2 birch to form like C’s from back of cab to baffle mostly along the longitudinal side. so if its 24 high by 40 wide theres two going from bottom to top along the length and usually two going other direction and for a double vented the middle is sealed with ports aiding in the bracing. Thats it. It seems our builds far far exceed these typical specs for bracing. So that leads me to my question finally, does freq response have any direct correlation to bracing requirements, ie does lower freqs at 20 hz need more bracing at 1w/1m same sensitivity than say 80hz (same volume and size for discussion purposes)


Sent from my iPhone using Tapatalk Pro
FOHTech is offline  
post #51 of 201 Old 07-23-2019, 04:43 PM
Advanced Member
 
lknhomeaudio's Avatar
 
Join Date: Jan 2012
Posts: 677
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 287 Post(s)
Liked: 148
Quote:
Originally Posted by Remy.Alexander View Post
How so? I was modeling the size I wanted for sealed and ported.
First off, I'll preface this with "people on a budget don't need to be chasing single digits!". lol And I am right there with you, believe me! At low dB, you aren't gonna feel any of that, and you FOR SURE aren't ever gonna hear it.

Getting to your modeling graphs you posted, I'm not sure if I have the wrong WDR file for that driver, or what, but you mentioned 800 watts in the original post... and I see your picture indicated 17mm of excursion, which for me takes 200 watts to get there in a 6ft box. So 200 watts for each driver is what I used for some quick modeling. Also, looking further into your excursion graphs, I can see you have entirely too high of an HPF on the ported sub, which isn't letting it do it's thing down low. I lowered the HPF to allow the sub to reach the same 17mm of excursion that the sealed sub does(fair is fair, right?) and the end result is +2dB for the ported sub from 11hz to 40hz and +4dB from 14hz to 22hz. With the overall performance being greater from up top, all the way down to 10hz.

So, either I missed some info somewhere, or your modeling is quite wrong.

Same box, same power



HPF adjusted to get excursion more equal

Attached Thumbnails
Click image for larger version

Name:	avs spl.JPG
Views:	110
Size:	180.4 KB
ID:	2593794   Click image for larger version

Name:	avs excursion.JPG
Views:	119
Size:	162.8 KB
ID:	2593796  
lknhomeaudio is offline  
post #52 of 201 Old 07-23-2019, 04:47 PM
Advanced Member
 
lknhomeaudio's Avatar
 
Join Date: Jan 2012
Posts: 677
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 287 Post(s)
Liked: 148
And this graph is keeping the box size the same, but cranking the power up to the excursion limits(about 550 watts), and adjusting HPF accordingly. Basically destroys the Sealed enclosure. (except below 10 hz that you'll never notice at low dB levels)

Attached Thumbnails
Click image for larger version

Name:	avs 550w.JPG
Views:	116
Size:	182.1 KB
ID:	2593800  
lknhomeaudio is offline  
post #53 of 201 Old 07-23-2019, 04:53 PM
Advanced Member
 
lknhomeaudio's Avatar
 
Join Date: Jan 2012
Posts: 677
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 287 Post(s)
Liked: 148
Here, I have changed to the 12ft box you mentioned... tuned it to 13hz, HPF @ 14hz and gave it 375 watts. Excursion is right at 17mm above and below tuning. Blows the sealed box out of the water down to 9hz.



Attached Thumbnails
Click image for larger version

Name:	avs 12ft.JPG
Views:	109
Size:	184.5 KB
ID:	2593802   Click image for larger version

Name:	avs 12ft excursion.JPG
Views:	119
Size:	167.0 KB
ID:	2593804  
lknhomeaudio is offline  
post #54 of 201 Old 07-23-2019, 07:19 PM - Thread Starter
Senior Member
 
Join Date: Aug 2018
Posts: 371
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 173 Post(s)
Liked: 54
@lknhomeaudio- Hey thanks for posting all the information, I appreciate it. Ill have a look at my figures and see what I did different.



I had the HPF set on the ported where it was as all I read about is death the the woofers And now im informed because of this thread 14mm is just overhang so thats awesome.


I have also learned doubling down the woofers wont make much of a difference? So now I have changed to two cabs both 6.6ft before bracing and woofer. And its funny you go into detail here about HPF and such because im currently trying to work out what I need for these and eq limits As its apparent I suck at modeling lol and WinISD has no shelf filters
lknhomeaudio likes this.
Remy.Alexander is offline  
post #55 of 201 Old 07-23-2019, 08:50 PM
Advanced Member
 
lknhomeaudio's Avatar
 
Join Date: Jan 2012
Posts: 677
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 287 Post(s)
Liked: 148
Quote:
Originally Posted by Remy.Alexander View Post
@lknhomeaudio- Hey thanks for posting all the information, I appreciate it. Ill have a look at my figures and see what I did different.




No problem.


Quote:
Originally Posted by Remy.Alexander View Post




And its funny you go into detail here about HPF and such because im currently trying to work out what I need for these and eq limits As its apparent I suck at modeling lol and WinISD has no shelf filters

They can completely rape your system! When I first started all of this, I inadvertently had my dip-switches on my amp set to either a 30 or 50hz HPF. And I had no idea haha. Like a year later I stumbled upon it and was soooo happy with all of my new found bass!
lknhomeaudio is offline  
post #56 of 201 Old 07-23-2019, 09:10 PM - Thread Starter
Senior Member
 
Join Date: Aug 2018
Posts: 371
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 173 Post(s)
Liked: 54
Quote:
Originally Posted by lknhomeaudio View Post
No problem.





They can completely rape your system! When I first started all of this, I inadvertently had my dip-switches on my amp set to either a 30 or 50hz HPF. And I had no idea haha. Like a year later I stumbled upon it and was soooo happy with all of my new found bass!
If the wife and kids leave me alone tomorrow i should be able to fire them up. If im reading @LTD02 thread correctly, I need to set a 20HZ HPF and a negative shelf like 2 or 3DB and then i think 2/3DB gain to offset. I want to add a tad of boost at 15HZ but again I have zero clues with these Inukes and their 20hz limited bs

Also going to add a bit more bracing- @notnyt said its really low lol so i have to evaluate that in the AM.
Remy.Alexander is offline  
post #57 of 201 Old 07-24-2019, 01:27 PM - Thread Starter
Senior Member
 
Join Date: Aug 2018
Posts: 371
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 173 Post(s)
Liked: 54
Just fired them up now- lightly stuffed HOF 20hz 12db and HS12 -2db, +2DB gan on bot to offset-- Whats thoughts on this?
Remy.Alexander is offline  
post #58 of 201 Old 07-26-2019, 08:31 PM
AVS Forum Addicted Member
 
BassThatHz's Avatar
 
Join Date: Apr 2008
Location: Northern Okan range (NW Cascades region)
Posts: 10,788
Mentioned: 233 Post(s)
Tagged: 0 Thread(s)
Quoted: 3763 Post(s)
Liked: 4269
Quote:
Originally Posted by MKtheater View Post
That cost is 6 times more distortion which I just learned. Sonosubs again. I will be comparing a UM18 to my xxx18 very soon.

sealed is better. You just buy enough drivers for low distortion and spl. It will give you full band everytime. Everything else is a compromise. The compromise to sealed is cost.
Let me highlight it for everyone: "Sonotubes AGAIN"
I hear an echo in here.

The RE-18's should walk circles around the UM's, at least below 40hz they will...
The UM's don't have much excursion, which is actually a HUGE problem when you are trying to get low and/or loud with watts. Especially so with fewer subs. As the cone-count increases that advantage likely diminishes, because (at some threshold) unused headroom is just that... that threshold is never encountered below 20hz because of how inefficient those frequencies are in regards to cone-based displacement and how our ears work.

Stated a simpler and different way: It seems one can never have TOO MUCH <20hz,
the SPL is never-enough!

As per sources, the men-in-black did tests back in the 40-60's with big subwoofers and other loud things ->



A 20ft subwoofer ought to git-ur-dun!
and supposedly 170db @ single digits is ear-damage loud (as per the "them"...)

Don't be scared of the "hypersonic missiles" fear mongering of recent. Someone needs to tell them we've had Mach-20 missiles since the 40's, it's nothing new. (Also tell them that we knew back then... that they had it too. The Russians. ) China has it now as well (yes, we know that too! )
The whole crust was mutually assured back THEN.
Just think of how mutually-assured we are with TODAYS technology...
High Technology has made war pointless. (and it always has been; in case it wasn't completely obvious...)
Breaking things is easy, any imbecile can do that... making the earth a BETTER place takes real-intelligence and properly applied-skills. (The human race ain't there yet on either count. LOL! )

Anyhow, where we're we again? Oh yes, loud things. Right!
Attached Thumbnails
Click image for larger version

Name:	L3.jpg
Views:	98
Size:	417.4 KB
ID:	2595040   Click image for larger version

Name:	L2.jpg
Views:	99
Size:	190.1 KB
ID:	2595042   Click image for larger version

Name:	L1.jpg
Views:	107
Size:	490.6 KB
ID:	2595044  
lknhomeaudio likes this.

Last edited by BassThatHz; 07-26-2019 at 11:05 PM.
BassThatHz is offline  
post #59 of 201 Old 07-26-2019, 09:16 PM
AVS Forum Addicted Member
 
BassThatHz's Avatar
 
Join Date: Apr 2008
Location: Northern Okan range (NW Cascades region)
Posts: 10,788
Mentioned: 233 Post(s)
Tagged: 0 Thread(s)
Quoted: 3763 Post(s)
Liked: 4269
Every time I've ever modeled ported vs sealed, it was always louder than sealed from slightly below tuning, to an octave or so above tuning...

Quote:
Originally Posted by lknhomeaudio View Post
Here, I have changed to the 12ft box
This is a good example of how SPL closely tracks watts in the upper Hz.
(This is exactly why IB sucks at mid-bass, because: it operates in the XLF excursion-limited power zone.)

There shouldn't be a huge separation of the SPL in the upper Hz like that. A clear indication of too much box and not enough cone. That is clearly NOT the optimal box-size for sealed for that driver, put it in a smaller box and crank the power so that it is equal to what you modeled with the ported. The ported will still show an advantage near tuning, obviously... and the sealed's SPL below 10hz will likely suffer a bit as well.
(Or alternatively: just boost the mid-bass with EQ to match it... or just use the MAX SPL plot, same difference.)

Sealed doesn't take advantage of the back side of the driver, ported does (focusing all that extra energy at the tuning frequency). In fact the back side on a sealed drivers fights the cone motion in every possible regard, leading to the inefficiency it is known for.

Below tuning the excursion and distortion on a ported sub abruptly rises to unusable levels. The HPF protects it from itself, and introduces additional phase issues... like ALL iir-based filters do. That's the price you pay for that extra SPL near the tuning. For many people that is a totally acceptable trade off.
Will P likes this.
BassThatHz is offline  
post #60 of 201 Old 07-26-2019, 10:29 PM
AVS Forum Addicted Member
 
BassThatHz's Avatar
 
Join Date: Apr 2008
Location: Northern Okan range (NW Cascades region)
Posts: 10,788
Mentioned: 233 Post(s)
Tagged: 0 Thread(s)
Quoted: 3763 Post(s)
Liked: 4269
Quote:
Originally Posted by notnyt View Post
it's not just flex, it's resonances. Also, "barely moving" is still moving.
I partially disagree...

Internal-resonances can be damped with fill to an acceptable degree, and yes for extremely long enclosures the braces can act as barriers and do help break up those standing waves in that regard as well.
However: The remainder IS caused by box flex (which IS solved by stiffening the box via bracing).

The stiffer the box, the higher the resonant frequency. Push it up high-enough and it will shift outside the bandwidth of the cone and therefore cannot be induced by it.

re: still moving...
"Technically": Everything above 0 Kelvin is moving. Motion can NEVER be stopped.
(Unless... it is currently in-the-process of being converted to/from pure energy: i.e. black holes, antimatter and fission etc. )

Every 6 inches is good. The box shouldn't be cardboard.
That said: a lot of people go complete overkill on their bracing, it doesn't need to be 24inches of solid tungsten to achieve the required\acceptable stiffness...

Density and mass can also HELP decrease box flex.
Generally most metals are FAR stiffer and denser than most woods. There have been speaker boxes made from aluminium. Mass resists changes in motion as per Newton's laws (flex being a motion.)
Composite CLD is another well-known approach, basically converting acoustic and kinetic energy into thermal-energy. Those options are often too costly or difficult to be worth the effort though. Using normal wood bracing for 3/4" panels is "good enough".

Identical principles are used for sound-proofing rooms (decoupling and anti-flanking too etc etc.)

Most of us already know all of this, I just like to be more-clear for those that don't...
bimmaguy and Will P like this.

Last edited by BassThatHz; 07-26-2019 at 10:33 PM.
BassThatHz is offline  
Sponsored Links
Advertisement
 
Reply DIY Speakers and Subs

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off