Your Home Theater ULF Score - Page 25 - AVS Forum
Forum Jump: 
 35Likes
Reply
 
Thread Tools
post #721 of 2246 Old 11-25-2013, 09:44 AM - Thread Starter
AVS Special Member
 
dominguez1's Avatar
 
Join Date: Dec 2008
Posts: 1,721
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 65 Post(s)
Liked: 164
Neutro, you are in the 4.5 star category, but at 16hz. 5 and 4.5 aren't specific to any ULF frequency. It's a frame of reference of what your output is at that frequency.

So 525@16hz, is 4.5 star at that frequency, and least in that category at 20hz.
dominguez1 is online now  
Sponsored Links
Advertisement
 
post #722 of 2246 Old 11-25-2013, 09:48 AM
 
BeeMan458's Avatar
 
Join Date: Jun 2012
Location: Magalia, CA
Posts: 8,374
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 801
Quote:
Originally Posted by neutro View Post

Moving there takes a lot of dedication, as in, you have to dedicate a room, a few breakers in your electrical panel and a substantial part of your income and free time to that project.

Three letters.....WAF. tongue.gif

My problem is not putting the order in prematurely.

(my expectations are, two FV15HPs in our 3300^3 room will be four stars)

Time will tell what REW has to say on the matter.
BeeMan458 is offline  
post #723 of 2246 Old 11-25-2013, 09:55 AM
Senior Member
 
BCRSS's Avatar
 
Join Date: Aug 2013
Posts: 276
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 40 Post(s)
Liked: 45
I will be joining the club before the end of the year, Currently have a PB12+ but have found an awesome deal on a pair of PC12+. Don't need 2 but for the price I can hardly pass them up.

So I am figuring 1745cf should bring me in the ball park of 363 @16. I am getting a nose bleed just thinking about it.

Tux's Elusive 1099 (L/C/R)---Ascend CBM-170 SE (surrounds 9.2)---SVS PB 12 Plus---SVS PC 12 Plus---AVR Denon 4311CI---TV Vizio 70---Unraid 32TB Network Storage---Gateway SX 2370 HTPC with 120 SSD
BCRSS is offline  
post #724 of 2246 Old 11-25-2013, 10:32 AM
AVS Special Member
 
neutro's Avatar
 
Join Date: Jan 2010
Location: Canada
Posts: 2,646
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 9 Post(s)
Liked: 436
Quote:
Originally Posted by dominguez1 View Post

Neutro, you are in the 4.5 star category, but at 16hz. 5 and 4.5 aren't specific to any ULF frequency. It's a frame of reference of what your output is at that frequency.

I understand better now smile.gif Thanks for clearing that up.

neutro is offline  
post #725 of 2246 Old 11-25-2013, 03:39 PM
Senior Member
 
Madaeel's Avatar
 
Join Date: Jul 2009
Posts: 209
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked: 20
Quote:
Originally Posted by beastaudio View Post

Hey dude! For sealed applications, nothing short of 8 cuft for the REXXX 18's. If you can fit 10, it won't hurt biggrin.gif

Dammit. I was afraid you'd say that. Thanks Beast. I take it then the 15" would be no different and need more around 4cuft per driver? I'm thinking of buying one and sending it to Josh if he has time to test it. I'm curious where it'd stack up with the other drivers in Dom's ULF ratings
Madaeel is offline  
post #726 of 2246 Old 11-25-2013, 04:57 PM
AVS Club Gold
 
JapanDave's Avatar
 
Join Date: Jul 2009
Posts: 2,342
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 20 Post(s)
Liked: 99
Quote:
Originally Posted by bossobass View Post


For example, using the spreadsheet for this thread, my current system would not be a 5 star system, but, as anyone can see by hundreds of posted measurements taken with extremely accurate measurement hardware, I have reference playback to 4 Hz with headroom, in-room. OTOH, many of the 5 star systems do not have that capability and it isn't because they lack the main ingredient of the spreadsheet calculations (driver displacement), because they have more than my current system does in that single aspect.
And this is part of the reason why I went with the real Lab Gruppen amps and a high quality receiver. My uncorrected FR for half my subs is above reference when I take the -7db drop from the calibrated FR to the pure signal roll-off uncorrected.

This is the corrected and uncorrected FR of 4 subs measured at minimal levels.



Below is 4 of my subs, not quite pushed to their limits in this graph. This graph is using correction files, so -7db's @ 3hz is about 108db (give or take a decibel or 2 as the volume increases). Run the whole 8 subs and I should have a true 2 to 3hz @ reference level. (BTW, I can't measure all 8 subs together due to how my receiver handles REW.)

dominguez1 likes this.

My build thread

My 8 x RE XXX 18" Subwoofers, IB build
Couldn't pour water out of a boot with instructions on the heel.

Do you know what Nemesis means?

JapanDave is online now  
post #727 of 2246 Old 11-25-2013, 05:43 PM - Thread Starter
AVS Special Member
 
dominguez1's Avatar
 
Join Date: Dec 2008
Posts: 1,721
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 65 Post(s)
Liked: 164

Let the 5hz scores start rolling in! :)

 

JapanDave to be upgraded to: 123@5hz, 5 star

 

Here's mine:

 

1000

 

Measurement Gear: Omnimic

 

This would put me at 432@5hz, 4.5 Star

dominguez1 is online now  
post #728 of 2246 Old 11-25-2013, 05:50 PM
AVS Special Member
 
neutro's Avatar
 
Join Date: Jan 2010
Location: Canada
Posts: 2,646
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 9 Post(s)
Liked: 436
Seeing that kind of scores... at which point does an air pressure change stop being "sound" and can be called a "meteorological phenomenon"? biggrin.gif

neutro is offline  
post #729 of 2246 Old 11-25-2013, 05:55 PM - Thread Starter
AVS Special Member
 
dominguez1's Avatar
 
Join Date: Dec 2008
Posts: 1,721
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 65 Post(s)
Liked: 164
Quote:
Originally Posted by neutro View Post

Seeing that kind of scores... at which point does an air pressure change stop being "sound" and can be called a "meteorological phenomenon"? biggrin.gif

Otherwise known as the 'Brown Note'. ;) 

dominguez1 is online now  
post #730 of 2246 Old 11-25-2013, 06:03 PM
AVS Special Member
 
neutro's Avatar
 
Join Date: Jan 2010
Location: Canada
Posts: 2,646
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 9 Post(s)
Liked: 436
I was just kidding but I just did some research. A cold or hot front is characterized by atmospheric pressure changing by more than 100 Pa per hour. 100 Pa registers as 134 dB SPL. So a sudden weather change is about 134 dB SPL (or more) @ 0.0003 Hz. Sorry for being so pedantic but I found that interesting enough to share.

neutro is offline  
post #731 of 2246 Old 11-25-2013, 06:03 PM
AVS Special Member
 
beastaudio's Avatar
 
Join Date: Dec 2010
Location: Western NC
Posts: 7,234
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 369 Post(s)
Liked: 655
Technically, the meteorological event for the brown note is called "The Dark Star Release"
dominguez1 likes this.

(European models do not accept banana plugs.)

 

"If you done it, it ain't bragging." ~ Walt Whitman

 

AE TD12x SEOS12 Build

Beast's DIY Master Measurement Thread

DIY Emminence Coaxial Surround Thread

beastaudio is offline  
post #732 of 2246 Old 11-25-2013, 06:03 PM - Thread Starter
AVS Special Member
 
dominguez1's Avatar
 
Join Date: Dec 2008
Posts: 1,721
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 65 Post(s)
Liked: 164
Quote:
Originally Posted by neutro View Post

As for SVS cylinders, I found a post by SVS's own Ed Mullen in HomeTheaterShack that explain the difference between the corresponding cylinder and box models:
Thus while it's not still 100% clear to me, it would appear that only the PC13-Ultra has 1.5 dB less than the PB13-Ultra at 20 Hz and below due to smaller enclosure volume. The PC12-NSD and PC12-Plus are thus likely to have the exact same numbers as the corresponding PB12s.

So unless someone finds a better reference, I think we could use the following numbers for the cylinders.

PC12-NSD: as the PB12-NSD (data-bass)
/ / 93.3 103.2

PC12-Plus: as the PB12-Plus, estimated as PB13-Ultra - 3 dB
Sealed: / 81.6 88.5 94.6
16 Hz tune: / 86.3 102.1 106.2
20 Hz tune:/ / 94.4 107.6

PC13-Ultra: estimated as the PB13-Ultra - 1.5 dB
Sealed: / 83.1 90.0 96.1
16 Hz tune: / 87.8 103.6 107.7
20 Hz tune: / / 95.9 109.1

For the record that makes the ULF scores for my setup (doesn't change the number of stars):

neutro - 525@16hz - 1680cf - 3.2 SI - Dual SVS PC12-Plus

Thanks neutro. I'll add/modify these when I make the next update.

dominguez1 is online now  
post #733 of 2246 Old 11-25-2013, 06:05 PM - Thread Starter
AVS Special Member
 
dominguez1's Avatar
 
Join Date: Dec 2008
Posts: 1,721
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 65 Post(s)
Liked: 164
Quote:
Originally Posted by beastaudio View Post

Technically, the meteorological event for the brown note is called "The Dark Star Release"

LOL!

dominguez1 is online now  
post #734 of 2246 Old 11-25-2013, 07:24 PM
AVS Special Member
 
Archaea's Avatar
 
Join Date: Apr 2004
Location: Kansas City, MO
Posts: 5,859
Mentioned: 6 Post(s)
Tagged: 2 Thread(s)
Quoted: 314 Post(s)
Liked: 611
There's some nonsense in this thread lately. No ported sub should be given much creedence at producing frequencies below port tune. It doesn't work like that. So a pb12 tuned to 20hz for example shouldn't be scored at all at 10hz. It would be largely distortion at best at 10hz on a 20hz tune ported sub.

Two Rythmik HPs are not going to create reference level play back to 10, 12.5, 16, or perhaps even 20hz in all but the smallest of rooms at the listening position. Reference being truly peaks of 115dB at the listening position. (At the frequency specified)

I say this as the former owner of a pair of SVS PB13 ultras, and as one having measured many many subs in many many rooms.

"Without subs it's just background music - with subs it's the main event!"
Archaea's Theatre Room
2011 KC Sub Shootout
2012 KC Blind Sub Shootout
My Subwoofer Recommendations by Pricepoint
Archaea is offline  
post #735 of 2246 Old 11-25-2013, 07:37 PM - Thread Starter
AVS Special Member
 
dominguez1's Avatar
 
Join Date: Dec 2008
Posts: 1,721
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 65 Post(s)
Liked: 164
Quote:
Originally Posted by Archaea View Post

There's some nonsense in this thread lately. No ported sub should be given much creedence at producing frequencies below port tune. It doesn't work like that. So a pb12 tuned to 20hz for example shouldn't be scored at all at 10hz. It would be largely distortion at best at 10hz on a 20hz tune ported sub.

Two Rythmik HPs are not going to create reference level play back to 10, 12.5, 16, or perhaps even 20hz in all but the smallest of rooms. Reference being truly peaks of 115dB at the listening position. (At the frequency specified)
Where do you see it he pb 12 scored at 10hz? It is not capable of that.

Are you referring to fv15hps? Why would you think it's not capable of reference?
dominguez1 is online now  
post #736 of 2246 Old 11-25-2013, 07:46 PM
Advanced Member
 
rcohen's Avatar
 
Join Date: Feb 2005
Posts: 997
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 144 Post(s)
Liked: 61
Why does the ULF score use cubic feet rather than surface area? In a closed room, don't surfaces absorb the acoustic energy, rather than air absorbing the energy?

According to the spreadsheet, my 4x Rythmik F25s gives me 3.5 stars, due to my 30x17x12 room. It says I need 18x F25s to get 5 stars.

What about corner loading?

Thanks
rcohen is online now  
post #737 of 2246 Old 11-25-2013, 08:00 PM - Thread Starter
AVS Special Member
 
dominguez1's Avatar
 
Join Date: Dec 2008
Posts: 1,721
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 65 Post(s)
Liked: 164
Quote:
Originally Posted by rcohen View Post

Why does the ULF score use cubic feet rather than surface area? In a closed room, don't surfaces absorb the acoustic energy, rather than air absorbing the energy?

According to the spreadsheet, my 4x Rythmik F25s gives me 3.5 stars, due to my 30x17x12 room. It says I need 18x F25s to get 5 stars.

What about corner loading?

Thanks
Not sure i understand the question. It uses cubic feet for the room size and a normalized displacement metric regardless of design (of which surface area is a factor) for the sub.

It is an anechoic measurement that gives a general guideline of in room performance.
dominguez1 is online now  
post #738 of 2246 Old 11-25-2013, 08:08 PM
AVS Special Member
 
Archaea's Avatar
 
Join Date: Apr 2004
Location: Kansas City, MO
Posts: 5,859
Mentioned: 6 Post(s)
Tagged: 2 Thread(s)
Quoted: 314 Post(s)
Liked: 611
As to the pb12 comment it was just an example keyed from some of the conversations in the last couple pages.

As to the rythmik fv15hp comment look at the long term ouput testing under comparable charts on databass.

10hz, 12hz, even 16hz aren't going to be very likely on something sustained with a pair in a typical theater room.

http://www.data-bass.com/data?page=system&id=51&mset=49

I like the ryrthmiks quite a bit, but some of the reason people may think they handle reference so well is that they handle their limits so well. The limiter can engage when necessary and compression may occur on the lowest frequencies without the listener ever being the wiser.

"Without subs it's just background music - with subs it's the main event!"
Archaea's Theatre Room
2011 KC Sub Shootout
2012 KC Blind Sub Shootout
My Subwoofer Recommendations by Pricepoint
Archaea is offline  
post #739 of 2246 Old 11-25-2013, 08:24 PM - Thread Starter
AVS Special Member
 
dominguez1's Avatar
 
Join Date: Dec 2008
Posts: 1,721
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 65 Post(s)
Liked: 164
Quote:
Originally Posted by Archaea View Post

As to the pb12 comment it was just an example keyed from some of the conversations in the last couple pages.

As to the rythmik fv15hp comment look at the long term ouput testing under comparable charts on databass.

10hz, 12hz, even 16hz aren't going to be very likely on something sustained with a pair in a typical theater room.

http://www.data-bass.com/data?page=system&id=51&mset=49

I like the ryrthmiks quite a bit, but some of the reason people may think they handle reference so well is that they handle their limits so well. The limiter can engage when necessary and compression may occur on the lowest frequencies without the listener ever being the wiser.

Explain to me how it is not likely? Let's take a 16hz example:

 

Per the long term compression sweep, at 16hz the FV15HP produces 104db with 8.7%THD anechoic. Duals co-located would product 110db at 16hz. You don't believe that when you put these inside a room that it would benefit from 5db of room gain?

dominguez1 is online now  
post #740 of 2246 Old 11-25-2013, 08:24 PM
Advanced Member
 
rcohen's Avatar
 
Join Date: Feb 2005
Posts: 997
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 144 Post(s)
Liked: 61
Quote:
Originally Posted by dominguez1 View Post

Not sure i understand the question. It uses cubic feet for the room size and a normalized displacement metric regardless of design (of which surface area is a factor) for the sub.

It is an anechoic measurement that gives a general guideline of in room performance.
I'm questioning whether sound energy at the listening position will be inversely proportional to cubic feet for a closed non-anechoic room.

In an anechoic or outdoor environment, I would expect sound energy to be proportional to 1/distance^2.
In an indoor closed room, depending on surface absorption, I would expect sound energy to be roughly proportional to 1/distance.

Has anyone tried verifying the predictions with different size rooms? I mean normal closed rooms, instead of anechoic chambers.

I'm not certain how this applies to bass, so I may have this wrong. I haven't made any measurements to back this up.
rcohen is online now  
post #741 of 2246 Old 11-25-2013, 08:29 PM
AVS Special Member
 
Archaea's Avatar
 
Join Date: Apr 2004
Location: Kansas City, MO
Posts: 5,859
Mentioned: 6 Post(s)
Tagged: 2 Thread(s)
Quoted: 314 Post(s)
Liked: 611
Room Gain if you are fortunate enough to have nice gain is offset by listening distance. Six foot is closer than most sit in a theater room. Most folk don't colocate dual subs. They space them apart to get smoother FR.

"Without subs it's just background music - with subs it's the main event!"
Archaea's Theatre Room
2011 KC Sub Shootout
2012 KC Blind Sub Shootout
My Subwoofer Recommendations by Pricepoint
Archaea is offline  
post #742 of 2246 Old 11-25-2013, 08:52 PM - Thread Starter
AVS Special Member
 
dominguez1's Avatar
 
Join Date: Dec 2008
Posts: 1,721
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 65 Post(s)
Liked: 164
Quote:
Originally Posted by Archaea View Post

Room Gain if you are fortunate enough to have nice gain is offset by listening distance. Six foot is closer than most sit in a theater room. Most folk don't colocate dual subs. They space them apart to get smoother FR.

I guess it all depends on your room. Certainly the smaller the room, the more gain. But, to say the reference is not possible with a pair FV15HPs is all but the smallest of rooms is silly. That's like saying a pair of $9000 Paradigm Sub2's can't achieve reference at 16hz or 20hz in your typical rooms. The FV15HP can actually produce more clean output than those!

dominguez1 is online now  
post #743 of 2246 Old 11-25-2013, 09:41 PM
Advanced Member
 
rcohen's Avatar
 
Join Date: Feb 2005
Posts: 997
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 144 Post(s)
Liked: 61
I did a little Google'ing on sub distance and room size and found a nice explanation here:
http://www.audioholics.com/loudspeaker-design/subwoofer-room-size

Most subwoofer room calculators seem to use the conservative cubic feet measurement.

That does seem overly conservative for closed rooms, though.
rcohen is online now  
post #744 of 2246 Old 11-26-2013, 04:36 AM
 
BeeMan458's Avatar
 
Join Date: Jun 2012
Location: Magalia, CA
Posts: 8,374
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 801
(very nice Audioholics article. thanks for the link)

And the FV15HP scores! A pair of FV15HP rips up the boards. (and the crowd goes wild) biggrin.gif

How pedantic are we suppose to get so as to know if our subs are worth a Tinker's Damn?

(i haven't changed my mind)

It seems that some aren't happy if they're not pushing string to the max which is fine as that's their prerogative, and I support their decision to do so but shouldn't the individual just come right out and publicly state for the record, that's what they're about? confused.gif

-
BeeMan458 is offline  
post #745 of 2246 Old 11-26-2013, 07:10 AM
AVS Special Member
 
Cowboys's Avatar
 
Join Date: Jun 2012
Posts: 1,346
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 106
Quote:
Originally Posted by Archaea View Post

Room Gain if you are fortunate enough to have nice gain is offset by listening distance. Six foot is closer than most sit in a theater room. Most folk don't colocate dual subs. They space them apart to get smoother FR.

Quote:
Originally Posted by rcohen View Post

I did a little Google'ing on sub distance and room size and found a nice explanation here:
http://www.audioholics.com/loudspeaker-design/subwoofer-room-size

Most subwoofer room calculators seem to use the conservative cubic feet measurement.

That does seem overly conservative for closed rooms, though.
Per this article: 'So in order for us to translate our 2 meter groundplane data to a corresponding 4 meter (~13ft) corner-loaded approximation, we can simply add 6dB (+12dB for two additional surfaces and -6dB for doubling of distance) to our SPL data. IE. If a sub measures 110dB 2 meter groundplane, the corresponding in-room output if the sub was corner-loaded would be roughly 116 dB at 4 meters.'
Cowboys is offline  
post #746 of 2246 Old 11-26-2013, 07:31 AM
Advanced Member
 
rcohen's Avatar
 
Join Date: Feb 2005
Posts: 997
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 144 Post(s)
Liked: 61
This is the part of the Audioholics article that I found most relevant to real rooms:
Quote:
In real rooms the walls are not infinitely long and are also lossy so boundary additions are closer to +3-4dB for each surface added yielding a net gain of +9dB to +12dB for 3 surfaces instead of +18dB theoretical. However, SPL fall off in real rooms is more like 3dB for every doubling of distance instead of 6dB which happens in an anechoic environment. We are being conservative in our SPL derating to add more cushion in our recommendation which reduces the likelihood of overdriving the sub in the intended listening space. Also we do not factor in room gain which is highly dependent on room dimensions and composition and will also help your sub play louder than what can be predicted in our theoretical scenario.
rcohen is online now  
post #747 of 2246 Old 11-26-2013, 07:51 AM
AVS Special Member
 
neutro's Avatar
 
Join Date: Jan 2010
Location: Canada
Posts: 2,646
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 9 Post(s)
Liked: 436
rcohen, the topic of using room volume in the score was discussed a few pages back as well.

I think we all know it's a bit flawed, as can be seen when considering limit cases. E.g. if you play a sub outside, you still have output, but the room volume is then infinite (that would give a solid zero star score). Likewise, you can take about any sub and place in an arbitrary small volume to generate 5-star experience. Perhaps that last one is justified (would running an SVS SB12 in my car -- a sub-200 cu ft volume -- provide me with reference level at 10 Hz?) but we can see there are flaws. However room volume is an easily computed proxy. Going past that would perhaps require something like a room simulation. That would be neat but harder to do in an Excel spreadsheet.

Note that in acoustics, we don't perceive intensity, but pressure directly. Pressure diminishes as 1 / distance, not 1 / distance squared. But what a room does is basically create reflections of the acoustical sources (6 images for the first reflections in a rectangular room, and many more from multiple reflexions). The bigger the room, the further the reflections. When a sub is corner-loaded, the three images in the corner are very close together and they are effectively co-located.

neutro is offline  
post #748 of 2246 Old 11-26-2013, 08:26 AM
Advanced Member
 
rcohen's Avatar
 
Join Date: Feb 2005
Posts: 997
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 144 Post(s)
Liked: 61
Thanks...I'll look back at the last discussion.

Here's where I'm coming from. My room is large and closed - 30x17x12. I have 4x Rythmik F25s in the corners. The calculator says I have 3.5 star bass, but I need 18x F25s (36x 15" drivers and 14,400 watts) for 5 star bass.

That seems pretty far off. I suspect that raising the room volume to some exponent between 1/2 and 2/3 would be more accurate for real rooms, rather than anechoic chambers.

I guess the number that really matters is db at the listening position, so I could just measure that for my purposes, rather than worrying about the spreadsheet.

Just pointing out the potential issue.
rcohen is online now  
post #749 of 2246 Old 11-26-2013, 08:36 AM
 
BeeMan458's Avatar
 
Join Date: Jun 2012
Location: Magalia, CA
Posts: 8,374
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 801
That's the problem with sealed units. The only ported unit I know of that works the middle ground between ported and sealed is the FV15HP in single port mode.

The reason I post the above, your above comments seems more like a lament than a statement. confused.gif
BeeMan458 is offline  
post #750 of 2246 Old 11-26-2013, 09:52 AM - Thread Starter
AVS Special Member
 
dominguez1's Avatar
 
Join Date: Dec 2008
Posts: 1,721
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 65 Post(s)
Liked: 164
Quote:
Originally Posted by rcohen View Post

Thanks...I'll look back at the last discussion.

Here's where I'm coming from. My room is large and closed - 30x17x12. I have 4x Rythmik F25s in the corners. The calculator says I have 3.5 star bass, but I need 18x F25s (36x 15" drivers and 14,400 watts) for 5 star bass.

That seems pretty far off. I suspect that raising the room volume to some exponent between 1/2 and 2/3 would be more accurate for real rooms, rather than anechoic chambers.

I guess the number that really matters is db at the listening position, so I could just measure that for my purposes, rather than worrying about the spreadsheet.

Just pointing out the potential issue.
That does seem a bit counter intuitive, but let's play it out with the math...(please someone correct me if my math/logic is wrong).

The SI at 10hz produces 89.2db. The UXL-18 produces 92.2db at 10hz. The difference is 3db. Using the calculation below:

L = 20 Log (x)

Where L is the difference in db (3) and x is the factor or multiple of SI

Solving for (x)

10^(3/20) = 1.4

This means it takes aprox 1.4 SIs to equal the UXL.

We can do this in reverse if we wanted to solve how much db is produced for a given SI (or factor):

Solving for L:

20 Log (1.4) = 3db
89.2 + 3db = 92.2db or the output of the UXL-18 at 10hz

Using the same logic, the calculator is estimating that it would take 18 F25s to produce above reference output at 10hz (5 Star). 18 F25s is equal to 21.6SI

20 Log (21.6) = 26.7db
89.2 + 26.7db = 115.9db or aproximately reference level in an anechoic environment.

Throw it in a room, and conservatively add 9db (used 9 instead of 12 for RMS value based upon the Audiholic conservative in room gain), and you're at 124.9db, or above reference output.

The calculator also estimates that it would take 8 F25s to get reference level output at 10hz (4.5 Star). 8 F25s = 9.6 SI

20 Log (9.6) = 19.6db
89.2 + 19.6 = 108.8db anechoic

Throw it in a room using the logic above: 108.8 + 9db = 117.8db in room, or right around reference output.

Larger rooms would exhibit closer to the 9db conservative estimate (example above). For smaller rooms that 9db would increase, thus why you don't need as many subs for smaller rooms.

Again, not perfect, but fairly close. Someone jump in here if my math/logic is incorrect...I'm no mathemetician. smile.gif

EDIT: in my mind reference level is between 115 and 121. most movies don't call for more than 115, but there is a theoretical reference of 121 if all channels required it at once and bass mgmt directed it to the Sub channel
dominguez1 is online now  
Reply Subwoofers, Bass, and Transducers

Tags
Fv15hp Subwoofer , Svs Sb13 Ultra Piano Gloss 13 Inch 1000 Watt Powered Subwoofer , Danley Sound Labs Dts 10 , Bic Pl 200 Acoustech Platinum Series Subwoofer , Elemental Designs A7s 450 , Bowers Wilkins Asw 610 , Epik Empire , Hsu Vtf 15h Subwoofer , Klipsch Sw 311 , Svs Pb12 Nsd Black Vinyl 12 Inch Powered Subwoofer , Velodyne Eq Max 15 15 Subwoofer , Seaton Sound Submersive H P

User Tag List

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