Thigpen Rotary Woofer - Page 13 - AVS Forum
Forum Jump: 
 
Thread Tools
post #361 of 837 Old 04-25-2006, 08:28 AM
AVS Special Member
 
Mark Seaton's Avatar
 
Join Date: Jul 2000
Location: Chicago, IL, USA
Posts: 6,064
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 79 Post(s)
Liked: 286
Quote:
Originally Posted by noah katz
Hmm, my HT area shares a wall with the garage, whose volume is about the same, making the fan sub feasible.

Looks like my original decision not to attend was flawed; I didn't want to torture myself by hearing something awesome that I could never have.
Hey Noah,

While Bruce's fan might be a bit elusive for now, after we got done adjusting the EQ on your DIY sub consisting of dual, sealed 18" drivers, you are much closer than many. I'll see if I can post a screen shot of the response I saved, but we did get ~flat response to ~10Hz in-room. It was too late to check how capable it was, down there, but after you add another pair up front I think you should have more than your neighboors would care for. ;)

Mark Seaton
Seaton Sound, Inc.
"Make no little plans; they have no magic to stir men's blood..." Daniel H. Burnham
Mark Seaton is online now  
Sponsored Links
Advertisement
 
post #362 of 837 Old 04-25-2006, 08:37 AM - Thread Starter
AVS Special Member
 
tzucc's Avatar
 
Join Date: Sep 2002
Location: Hype Central
Posts: 3,162
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
How is it that my dual 18" drivers on my XS fall off dramatically at 18Hz, and you claim to get 10Hz flat on another sub with dual 18's?!

Or more importantly, at what SPL did you get between 10 and 20Hz?

rotary subwoofer install blog ultimate subwoofer install : http://bassment.wordpress.com/ ... c
tzucc is offline  
post #363 of 837 Old 04-25-2006, 09:07 AM
AVS Club Gold
 
Mr.Poindexter's Avatar
 
Join Date: Jan 2002
Location: Clovis, California
Posts: 7,388
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Liked: 25
Quote:
Originally Posted by longtimelurker
until we have video (if possible), can someone who was there explain what it "looks like" when operating...ie are the blades pitching +/- at the driving frequency (so can you see the fan cycle from + to - pitch 2 times/sec at 2hz?).
You cannot really see the fan blades pitch with the naked eye although I did get something close to that on my camera due to a strobe effect.

I am ordering my new video editing station today and should have it in about a week (new Macbook Pro was released this weekend!) and the first order of business will be getting the video I took at 720p24 and 720p60 converted to MPEG2 and MPEG4 streams and uploaded to the net for all to see. I also am curious to find out if my mics will record sound that low.
Mr.Poindexter is offline  
post #364 of 837 Old 04-25-2006, 09:10 AM
AVS Club Gold
 
Mr.Poindexter's Avatar
 
Join Date: Jan 2002
Location: Clovis, California
Posts: 7,388
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Liked: 25
Quote:
Originally Posted by tzucc
How is it that my dual 18" drivers on my XS fall off dramatically at 18Hz, and you claim to get 10Hz flat on another sub with dual 18's?!

Or more importantly, at what SPL did you get between 10 and 20Hz?
Tony, your sub is ported and ported subs roll off VERY fast after their cutoff. My IRS speakers were all sealed and they could put out bass at 5Hz that I could feel shaking my house. If you want truly low bass in a traditional sub, make is an acoustic suspension system, not bass reflex.
Mr.Poindexter is offline  
post #365 of 837 Old 04-25-2006, 09:11 AM
AVS Special Member
 
Ericglo's Avatar
 
Join Date: Oct 2004
Location: Just below the US in South Florida
Posts: 6,288
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 109 Post(s)
Liked: 43
How is it that there are no pics? What did everyone blow there wad that they forgot to take pics (Poindexter not included)?:)

Ericglo

Call AVS For the Best Deals!!!


My new favorite game is Stop the Bots
Ericglo is offline  
post #366 of 837 Old 04-25-2006, 09:21 AM - Thread Starter
AVS Special Member
 
tzucc's Avatar
 
Join Date: Sep 2002
Location: Hype Central
Posts: 3,162
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by Mr.Poindexter
Tony, your sub is ported and ported subs roll off VERY fast after their cutoff. My IRS speakers were all sealed and they could put out bass at 5Hz that I could feel shaking my house. If you want truly low bass in a traditional sub, make is an acoustic suspension system, not bass reflex.
So why would Wilson make that huge gargantuan sub and then port it and lose all the output?!

What SPL levels did your sub put out at 5Hz? It seems inconcievable that your sub with 1 or 2 drivers can create the pressure amplitude anywhere near what a fan sub would do. Something's not making sense here.

rotary subwoofer install blog ultimate subwoofer install : http://bassment.wordpress.com/ ... c
tzucc is offline  
post #367 of 837 Old 04-25-2006, 09:26 AM
AVS Special Member
 
Mark Seaton's Avatar
 
Join Date: Jul 2000
Location: Chicago, IL, USA
Posts: 6,064
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 79 Post(s)
Liked: 286
Quote:
Originally Posted by tzucc
How is it that my dual 18" drivers on my XS fall off dramatically at 18Hz, and you claim to get 10Hz flat on another sub with dual 18's?!

Or more importantly, at what SPL did you get between 10 and 20Hz?
Tony,

Your subwoofer is vented, this is a sealed design. While I haven't ever seen any easily comparable measurements of the XS, but I would guess it is tuned somewhere around 16-18Hz. Below tuning, the port and the driver progressively short eachother's efforts out, which results in the roughly -24dB/octave roll off of a vented design. It is a fruitless effort to try and EQ/boost a vented subwoofer much below the tuning frequency.

A sealed subwoofer will often begin to roll off higher in frequency, but this roll off is at 1/2 the rate, or -12dB/octave. In a sealed system the efficiency will drop below the resonant point in the system, but since SPL is just a matter of air displacement, the peak maximum output is mostly limited by excursion x surface area and the resulting displaced volume. Since efficiency drops with lowering frequency, it does require EQ and of course more power to force the system to have flat response to lower frequencies than the resonant frequency of the specific driver in the specific box volume. In this case, you can EQ the response of the driver, with the increasing power requirement and it's variety of effects being the trade off, but the low frequency limitations of a driver come down to how loud you need to play. As you go lower, maximum output also falls at 12dB/octave.

Tieing this into what I was talking about at dinner on Saturday, an enclosed room provides significant low frequency gain once we get below the modal region of the room and into the pressure-region. A rough approximation of this transition can be found by calculating the long diagonal of the room and determining what the equivalent 1/2 wavelength is. In the majority of home theaters, this occurs in the 14-28Hz range. Once in this pressurization range, we are effectively modulating the pressure in the room, not bouncing waves around. Placing a subwoofer in such a an ideally sealed space will provide a gain in output of 12dB/octave below the transition frequency. When I say that it provides gain, this is relative to the same subwoofer measured outdoors as Keith Yates did in his subwoofer tests. Properly designed, sealed, car audio subwoofers are designed in the same manner, where a subwoofer that rolls off in the 45-80Hz range will often exhibit LF response into the 8-16Hz range in-car.

This is the reason we were able to EQ thebland's bDeap's to extend to the 8-10Hz range, where the high pass of his K2s kick in. Note that almost by definition, any room that is designed for noise isolation will have significant LF gain. More common construction methods exhibit a lossier gain function where we see 6-12dB/octave depending on frequency, with ~9dB/octave being fairly common. Ed Mullen measured a perfect example of this effect in his review of the Triad Gold PowerSub (even though its maximum output is rather low) as can be seen in comparing the outdoor and in-room graphs on this page:
http://www.hometheaterhifi.com/volum...05-part-2.html

In some rooms I have seen this effect maintained down to as low as 5Hz. In ideally rigid rooms, this gain effectively keeps output of a sealed subwoofer equal to what it can do near the transition frequency. My first subwoofer is specifically designed to have a frequency response that should integrate well with the low frequency transfer function of most rooms, and can easily provide 10Hz in-room extension with some EQ if the room is reasonably well confined. In your room, the low extension and upper bass headroom in my sub would make for a rather easy and flexible integration with the Thigpen device. Of course I have 2 other designs that also offer some interesting benefits as well.

As you ask, the question of course is how much output is available. Fortunately you can always add more subwoofers or drivers, where each doubling of subs/drivers gains you 6dB. This effect is why I have long argued that in the vast majority of rooms, the optimal anechoic or free-field response is NOT a flat response, but rather one with a gradual roll off. Bruce's subwoofer is affected differently when working in this range so the requirements are a bit different.

The Thigpen subwoofer will likely be the only if not one of a few options to provide high levels below 5-16Hz, where it's 1-10 Hz performance will be very hard to match. Part of my point was that it doesn't have to cost $10-15k, nor require an adjacent space to get a very worthwhile percentage of the VLF capability we experienced on Saturday. Some guys with huge infinite baffle installations are already a long way there.

In the case of Noah's DIY subwoofer, the box is 14-15 cu.ft. internally with two 18" drivers that have about 1.5 x the excursion capability of the drivers in your Wilson XS. As an experiment, you could take some tightly wadded up rags and try to stuff the ports in your XS so they are mostly sealed. With those drivers you would probably see a gradual down-slope to the response measured in-room.

Unfortunately it was way too late at night for us to do any sort of high level testing, but in Noah's system the channel of his K2 amplifier driving the 18s sets the output limit. If he's not clipping the amp, he's not likely past the driver's limits. We were able to briefly listen to U-571 at about -10 to -15 dB on the main volume without any clipping of the amplifier with the system caliabrated pretty well flat.

Mark Seaton
Seaton Sound, Inc.
"Make no little plans; they have no magic to stir men's blood..." Daniel H. Burnham
Mark Seaton is online now  
post #368 of 837 Old 04-25-2006, 09:31 AM
AVS Special Member
 
Mark Seaton's Avatar
 
Join Date: Jul 2000
Location: Chicago, IL, USA
Posts: 6,064
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 79 Post(s)
Liked: 286
Quote:
Originally Posted by tzucc
So why would Wilson make that huge gargantuan sub and then port it and lose all the output?!
A ported sub can be made to be more efficient down to it's low frequency tuning than a sealed sub of similar size. When the XS was designed, 16-18Hz was considered "excessive" for home use. Making it sealed would result in a good bit less output in the 16-20Hz range (near its port tuning). The trade is that maximum output is then greater below say 15Hz. Also note that Poindexter's Infinity's used a tower of multiple drivers.

Mark Seaton
Seaton Sound, Inc.
"Make no little plans; they have no magic to stir men's blood..." Daniel H. Burnham
Mark Seaton is online now  
post #369 of 837 Old 04-25-2006, 09:43 AM - Thread Starter
AVS Special Member
 
tzucc's Avatar
 
Join Date: Sep 2002
Location: Hype Central
Posts: 3,162
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Mark, thanks for the detailed response. I suppose all that matters in the end, is what is the SPL curve from DC to 30Hz, let's say, and THD of that output.

Now, in your post above, where you said you saw the room gain result in a signal of 5Hz, what was the SPL of that frequency?

Also, I can tell you that the XS can not take anywhere near the full power of my K2... I have it set at about 40% of total amplification on the amp... I can find out the input signal level tonight.

edit: I don't think any talk about extending a sub's range into 8Hz is useful, unless we also qoute a SPL with that. As we learned Saturday, 8Hz at 80-90dB is basically not there as far as the human is concerned. It gets to an interesting level, for me, at 110dB.

rotary subwoofer install blog ultimate subwoofer install : http://bassment.wordpress.com/ ... c
tzucc is offline  
post #370 of 837 Old 04-25-2006, 10:22 AM - Thread Starter
AVS Special Member
 
tzucc's Avatar
 
Join Date: Sep 2002
Location: Hype Central
Posts: 3,162
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
just had an interesting thought on the consequences of my demo Sat. I seem to now detect vibration more easily, after having focused on looking for it during the last week's demos. So my wife pulls in the garage, or the garbage truck down the street crashing the dumpsters on the ground... could feel them in my house.
Now I am wondering if my neighbors are going to blame me every time they feel some low F vibration in their house... I could become the scapegoat and public enemy #1 around the area, if I install the fan subs, no matter what I do. The only way to not take the hit would be to prove they are not there.

rotary subwoofer install blog ultimate subwoofer install : http://bassment.wordpress.com/ ... c
tzucc is offline  
post #371 of 837 Old 04-25-2006, 10:34 AM
AVS Special Member
 
Morbius's Avatar
 
Join Date: Nov 2000
Location: Livermore, CA USA
Posts: 4,728
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 13
Quote:
Originally Posted by tzucc
j The only way to not take the hit would be to prove they are not there.
tzucc,

"You can't prove a negative." :)

Quote:
just had an interesting thought on the consequences of my demo Sat. I seem to now
detect vibration more easily,
This sounds just like comic book "superheros" - after being exposed to spider bite,
gamma radiation,.... whatever; Spiderman, The Incredible Hulk, Green Lantern....
are endowed with special powers!!!

After being bombarded by 120 dB of 3 Hz audio radiation, tzucc is now transformed into...[drum roll]
"Bass Man" - who with his super power at detecting subsonic audio vibrations seeks out low
frequency movie content, and strives for truth, justice, and the American way!!! :)

Dr. Gregory Greenman
Physicist
Morbius is offline  
post #372 of 837 Old 04-25-2006, 11:18 AM - Thread Starter
AVS Special Member
 
tzucc's Avatar
 
Join Date: Sep 2002
Location: Hype Central
Posts: 3,162
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
hehe... actually with the right install, as currently planned, you can do a complete walk through of the habitable areas of the house, and you won't see anything unusual.

rotary subwoofer install blog ultimate subwoofer install : http://bassment.wordpress.com/ ... c
tzucc is offline  
post #373 of 837 Old 04-25-2006, 01:27 PM
AVS Special Member
 
Morbius's Avatar
 
Join Date: Nov 2000
Location: Livermore, CA USA
Posts: 4,728
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 13
Quote:
Originally Posted by tzucc
hehe... actually with the right install, as currently planned, you can do a complete walk through of the habitable areas of the house, and you won't see anything unusual.
tzucc,

Yeah - you're going to have to post a sign; "Beware of Subwoofer" :)

Dr. Gregory Greenman
Physicist
Morbius is offline  
post #374 of 837 Old 04-25-2006, 01:29 PM
AVS Special Member
 
Randybes's Avatar
 
Join Date: May 2002
Location: Midwest
Posts: 2,622
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by Morbius
tzucc,

Yeah - you're going to have to post a sign; "Beware of Subwoofer" :)
Funny! You are "hittin the note today" :)
Randybes is offline  
post #375 of 837 Old 04-25-2006, 01:34 PM - Thread Starter
AVS Special Member
 
tzucc's Avatar
 
Join Date: Sep 2002
Location: Hype Central
Posts: 3,162
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by Morbius
tzucc,
Yeah - you're going to have to post a sign; "Beware of Subwoofer" :)
what I should get is one of those signs at extreme amusement park rides... something about not entering if you have back or heart problems, or experience incontinence occasionally :)

rotary subwoofer install blog ultimate subwoofer install : http://bassment.wordpress.com/ ... c
tzucc is offline  
post #376 of 837 Old 04-25-2006, 01:35 PM
AVS Addicted Member
 
Michael Grant's Avatar
 
Join Date: Apr 2001
Location: Austin, TX
Posts: 10,239
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 22
Well, needless to say, I'm gonna bank on Mark Seaton being right about the bass reproduction capacity of a sealed room. We'll just have to see how rigid I can get those walls :)

Michael
Michael Grant is offline  
post #377 of 837 Old 04-25-2006, 02:08 PM
AVS Addicted Member
 
noah katz's Avatar
 
Join Date: Apr 1999
Location: Mountain View, CA USA
Posts: 20,623
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 297 Post(s)
Liked: 167
Mark,

One thing that's not clear in my mind is how the perceived extra oomph varies with the LF extension it adds; i.e., if it only extended to 10 Hz, how much of the subjective incremental improvement would that give?

It sounds like you think the second sub would put me a good way there on what the fan sub offers for my room volume - cool!

And thanks again for the great sub tuneup.

Near midnight after a late dinner, Mark asked if I'd like to take a look at my sub's response.

Could I say no? :) One thing leads to another, and after 3 hr (I have an analog EQ accessible only from the garage), things were nicely smoothed out.

[back to the Helmholtz tangent]

Morbius,

"The constraint on the wavelength is a condition on being able to treat the enclosed air as
a single unit... "

True, but that doesn't preclude Helmholtz operation if the condition isn't met.

An example is induction tracts on piston engines, where the diameter of the piping determines the freq/rpm where cylinder filling and torque is increased by Helmholtz resonance (smaller diameter tunes lower just like ported speakers), and the length determines where it is increased by acoustic pipe effects.

Noah
noah katz is online now  
post #378 of 837 Old 04-25-2006, 02:27 PM
AVS Club Gold
 
Mr.Poindexter's Avatar
 
Join Date: Jan 2002
Location: Clovis, California
Posts: 7,388
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Liked: 25
Quote:
Originally Posted by tzucc
So why would Wilson make that huge gargantuan sub and then port it and lose all the output?!

What SPL levels did your sub put out at 5Hz? It seems inconcievable that your sub with 1 or 2 drivers can create the pressure amplitude anywhere near what a fan sub would do. Something's not making sense here.
As Mark said so well technically - they sold out its low frequency output to buy more upper frequency output. That was probably a determination on what would net more dollars into the coffers - or put another way, what would be more important to most end users - greater output above 20Hz at the expense of output below 20Hz.

While you have just become more aware of VLF, I have a long history of experiencing it. I was easily able to feel the output of my IRS V's at those levels. I even saw them reach full excursion recreating a 2-3Hz signal but I would say that I couldn't sense that. All I could do was hear the woofers moving - a strange sound actually since one normally never hears a woofer move.

Sadly, I no longer have the output graphs of my IRS system - one of the mains and one of the full system with all 32 (yes, thirty-two) 12" woofers. Considering that all of them were sealed and they used servo feedback it was astounding what they could do. It was about as impressive as Bruce's demo in the 12-18Hz range, much more impressive from 18hz and up and much less impressive from 12Hz and lower. Sometimes it was so intense I was afraid the floor was going to open up and that my house would fall apart. Sadly, I am now down to 10 12" woofers - about comparable to 4 1/2 18" woofers. They are all sealed, however, so I still get some decent output down low.
Mr.Poindexter is offline  
post #379 of 837 Old 04-25-2006, 02:32 PM - Thread Starter
AVS Special Member
 
tzucc's Avatar
 
Join Date: Sep 2002
Location: Hype Central
Posts: 3,162
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
If adding more subs helps, then I must be missing something.

I went to add 2400W and a Wilson XS and didn't get as much perceivable improvement from just the two Watchdogs as I expected, and that is after trying several room positions at which point I ended up obtaining a relatively flat SPL level from 20-80Hz. Maybe I haven't tried enough room locations for the XS, but it is a bit unwieldy.

As it is, my room has no response to speak of below 18Hz. Decent amounts above 20Hz.
From Bruce's analysis, we would need 10 XS subs to approach his volume of air movement at below 10Hz.

rotary subwoofer install blog ultimate subwoofer install : http://bassment.wordpress.com/ ... c
tzucc is offline  
post #380 of 837 Old 04-25-2006, 02:36 PM - Thread Starter
AVS Special Member
 
tzucc's Avatar
 
Join Date: Sep 2002
Location: Hype Central
Posts: 3,162
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by Mr.Poindexter
Sadly, I no longer have the output graphs of my IRS system - one of the mains and one of the full system with all 32 (yes, thirty-two) 12" woofers. Considering that all of them were sealed and they used servo feedback it was astounding what they could do. It was about as impressive as Bruce's demo in the 12-18Hz range, much more impressive from 18hz and up and much less impressive from 12Hz and lower. Sometimes it was so intense I was afraid the floor was going to open up and that my house would fall apart. Sadly, I am now down to 10 12" woofers - about comparable to 4 1/2 18" woofers. They are all sealed, however, so I still get some decent output down low.
Actually Bruce's sub wasn't producing all that much output from 12-20Hz it seemed. He needed to do some more tuning there, wrt phase coherency with the other subs, at least that's what I remember him mentioning. Above 18Hz, it was all about the Dogs and the XS, so, yes, I can see how 32 12" woofers could out do 2 18" and two 10" drivers. Must have been something to see and hear!

rotary subwoofer install blog ultimate subwoofer install : http://bassment.wordpress.com/ ... c
tzucc is offline  
post #381 of 837 Old 04-25-2006, 02:49 PM
AVS Special Member
 
Morbius's Avatar
 
Join Date: Nov 2000
Location: Livermore, CA USA
Posts: 4,728
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 13
Quote:
Originally Posted by noah katz
An example is induction tracts on piston engines, where the diameter of the piping determines the freq/rpm where cylinder filling and torque is increased by Helmholtz resonance (smaller diameter tunes lower just like ported speakers), and the length determines where it is increased by acoustic pipe effects.
noah,

It's really a misnomer to call what is done in induction tracts on piston engines a "Helmholtz
resonator". What's going on in the induction tract is actually a standing wave like in an organ
pipe.

Now it is true that Hermann von Helmholtz described how organ pipes work in his book,
"On the Sensation of Tone" - but that's NOT what he called a Helmholtz resonator.

Perhaps that's the vernacular to call these standing wave devices a "Helmholtz resonator" -
but that's not the terminology that Helmholtz used for such devices.

Dr. Gregory Greenman
Physicist
Morbius is offline  
post #382 of 837 Old 04-25-2006, 03:25 PM
AVS Addicted Member
 
noah katz's Avatar
 
Join Date: Apr 1999
Location: Mountain View, CA USA
Posts: 20,623
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 297 Post(s)
Liked: 167
Morrbius,

"It's really a misnomer to call what is done in induction tracts on piston engines a "Helmholtz
resonator". What's going on in the induction tract is actually a standing wave like in an organ
pipe."

As I said, both phenomena are operating.....I think.

I thought I read such in my youth before I had any education in these things. The fact that smaller diameter tracts give better filling at lower freq bears superficial resemblance to Helmholtz resonance, but that may be simply because it increases velocity, which is choked off at higher freq by viscous losses.

And it's all complicated by the fact that there's a DC throughput, but at this point I don't see why it should be ruled out.

What are your reasons for doing so?

Noah
noah katz is online now  
post #383 of 837 Old 04-25-2006, 03:31 PM
AVS Special Member
 
Morbius's Avatar
 
Join Date: Nov 2000
Location: Livermore, CA USA
Posts: 4,728
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 13
Quote:
Originally Posted by noah katz
And it's all complicated by the fact that there's a DC throughput, but at this point I don't see why it should be ruled out.

What are your reasons for doing so?
noah,

I'm not sure what you mean above. What am I ruling out and where?

I am ruling out the higher frequencies produced by the rotarty subwoofer. Those, like the
noise of the running fan itself are attenuated in Thigpen's setup. What one wants from this
rotary subwoofer are only the frequencies that it alone can produce - the truly sub-20 Hz or
even sub-10 Hz components. Anything above that is taken care of by a conventional subwoofer.

That, at least, was how the system was setup at tzucc's. The rotary subwoofer only handled the
very lowest sub-sonic frequencies, and the resident XS and Watch Dogs did the rest.

Dr. Gregory Greenman
Physicist
Morbius is offline  
post #384 of 837 Old 04-25-2006, 03:52 PM
AVS Special Member
 
Mark Seaton's Avatar
 
Join Date: Jul 2000
Location: Chicago, IL, USA
Posts: 6,064
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 79 Post(s)
Liked: 286
Quote:
Originally Posted by tzucc
Mark, thanks for the detailed response. I suppose all that matters in the end, is what is the SPL curve from DC to 30Hz, let's say, and THD of that output.

Now, in your post above, where you said you saw the room gain result in a signal of 5Hz, what was the SPL of that frequency?

Also, I can tell you that the XS can not take anywhere near the full power of my K2... I have it set at about 40% of total amplification on the amp... I can find out the input signal level tonight.

edit: I don't think any talk about extending a sub's range into 8Hz is useful, unless we also qoute a SPL with that. As we learned Saturday, 8Hz at 80-90dB is basically not there as far as the human is concerned. It gets to an interesting level, for me, at 110dB.
Starting from the bottom of your post up, I fully agree that extension without context of output capability is meaningless. Bag End is (in)famous for that one. In my oppinion and experience as I've stated here before, getting to around 100dB @ the listening position is where things start becoming "useful" to the point that they clearly add to the experience. We didn't really spend much time at levels where the VLF was near the hearing threshold, but I don't equate the supposed threshold of audibility the same as detection or reaction. The addition of the lower frequency range has a subjective effect in my experience at a good range of listening levels, and sometimes due to other more subtle effects.

So far as "desireable" levels, I would agree that ~110dB at a given frequency down to 10Hz should be a minor benchmark, where I think there is merit to allow for peaks up to 125dB down low... in dedicated spaces that won't fall apart in the process. ;)

What you are missing about the talk of multiple subwoofers is that with any reflex (vented or PR) subwoofer, adding more subwoofers gives you very little gain in useful low frequency extension no matter the EQ you have. This is the nature and trade-off of the design. A sealed system requires much more displacement from the driver vs. the reflex design near tuning, and thus is more difficult to maintain very low distortion. What you might be overlooking is that as you go lower in frequency, the multiple subwoofers are in fact quite close together from the perspective of wavelength, so at very low frequencies, multiple subwoofers usually exhibit a full 5-6dB of summation, even when placed separately. As you add more subwoofers, the maximum output down low increases. If the single subwoofers are capable of enough and enough are employed, the maximum output can climb to useful levels.

Also remember that for the majority of demos we listened to before you guys let me "drive," peak levels at a given frequency were rarely over 110dB, and more commonly around 100dB, and Bruce had the <10-12Hz level adjusted probably 8-10dB stronger than the other subwoofers. Don't get me wrong, I don't expect a pack of sealed subwoofers to have the same effect as Bruce's subwoofer which was amazingly clean and compression free into the single digit range, but it should be clear from our experiences Saturday that adding more VLF capability is useful.

In the systems I have measured extension into the 5-10Hz range, I have seen maximum output at say 10Hz ranging from 95dB up to near 110dB. I believe that Tom Nousaine's 8 x 15" IB which he wrote an article about did nearly 120dB at 12Hz at his listening position in a 7,500 cu.ft. room, but I would have to check the exact details. By pure comparison of volume displacement, 4 of my subwoofers should be within ~3-4dB relative to volume displacement of his IB (while needing quite a bit more power to get there).

From our testing Saturday it was clear that my TEF25 & TEF04 mc was accurate to 6Hz, and I need to do some checking into the roll-off below there to find the source. I believe the TEF20, which I used for some of the measurements I mentioned, may do better down extremely low. Here is a ~1/12th octave resolution measurement from Noah's seat after we finished adjusting 4 bands of parametric EQ. For the record, I HATE adjusting these analog EQ's where 1 minute of rotation on a ~3/8" diameter knob can be very significant. The measurement level was low because it was after midnight as Noah mentioned. There may be a little extra wiggle due to the low measurement level, but noise levels were very low and the noise rejection of the TDS measurement allows working at these levels. The overlaid yellow curve at the upper end was a quick check of integration with the center channel after we finished working on the subwoofer.

http://home.comcast.net/~mark_seaton.../Noah-2x18.jpg

Mark Seaton
Seaton Sound, Inc.
"Make no little plans; they have no magic to stir men's blood..." Daniel H. Burnham
Mark Seaton is online now  
post #385 of 837 Old 04-25-2006, 04:11 PM - Thread Starter
AVS Special Member
 
tzucc's Avatar
 
Join Date: Sep 2002
Location: Hype Central
Posts: 3,162
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Nice work Mark. Why didn't you do that for my room?!?! I had a case of cold Corona's in the fridge!

Anyway, the curve is nice, but not very meaningful to me... at 65dB, I am sure it's not audible below 20Hz and certainly below 15Hz it's not even detectable. I agree that although you might not hear 10Hz at 90dB, still it might mean 'something useful' to the senses, but at 75dB falling to 60dB, I would wonder if it still does anything at all for someone. Heck, I can barely stand to watch a movie at 85dB, and that's for higher freq where the ear is far more sensitive to loudness. Maybe (well not maybe) I am just deaf.

I would want to know what the curve looks like at your 'reference' volumes for the rest of the system.

Also, I am guessing there is a big difference between 95dB and 110dB that you measured. Apparently our dynamic range at the sub 15Hz range is only a handful or two of dB, and so 95dB might be nothing, and 110dB everything or at least detectable and impactful.

I suppose my conclusion after the weekend is that raw wattage and conventional cones is an exercise in maximizing dollar, space, and power consumption, leaving one frustrated in the pursuit of emotional and impactful full range bass. When you are trying to create impactful sub-20Hz with an ear and human perceptual system such as it is, go for something that moves air in volumes far beyond the ability of large paper cones that move 20mm back and forth. I just don't subscribe to the solution of putting like 8 subs or columns of woofers and expending 10-20kW to do much less than the full range of what one fan sub and 200W will do.

Alas, there is no free lunch, and I think the major draw back of the fan sub is the fan noise that needs baffling to reduce. I am not a huge fan (had to put that in somewhere) of that aspect. But I am willing to put in the construction effort to go for it. Esp if I can hit 130dB across DC to 15 or 20Hz.... that would be sweet... and I have you to blame for that... I really didn't get hooked on the sub, truth be told, until later at night you cranked up the volume. IF for some reason, the fan sub can't be reliable at that amplitude, then it's toast for me. If it can, I will bend over hard to make it happen.

rotary subwoofer install blog ultimate subwoofer install : http://bassment.wordpress.com/ ... c
tzucc is offline  
post #386 of 837 Old 04-25-2006, 09:41 PM
AVS Special Member
 
Mark Seaton's Avatar
 
Join Date: Jul 2000
Location: Chicago, IL, USA
Posts: 6,064
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 79 Post(s)
Liked: 286
Quote:
Originally Posted by tzucc
Nice work Mark. Why didn't you do that for my room?!?! I had a case of cold Corona's in the fridge!
Hey Tzucc,

Just like 2.5 years ago when I last visited your theater, I saw your system as a pandora's box that would keep the perfectionist in me busy for 6-12 hours. More importantly, without any EQ or treatments to adjust, it would have been more of an effort in pointing out problems that we can't fix or needing to start moving things around (not a trivial issue with the X-1s or the XS). Aside from the fact that Noah and I have conversed via the internet for 8-10 years now (but only met face to face on this trip) and I was partly responsible for him going with a sealed option rather than vented, his system was limited in what we could play with since the subs were set, and the receiver's auto-setup wasn't very friendly in letting us make adjustments. That left the only adjustment being the subwoofer EQ. As so often happens, what should have taken 1 hour turned into a 3 hour ordeal, and Noah has the scar to show for it. :eek:

On a more serious note, I would say that as good as your system sounds, it has room for notable improvement through setup, placement and EQ, but I didn't get the feeling you were ready to try much in the way of changes, and we certainly didn't have time, nor EQ available to do it properly. I'm pretty sure I'll be in the region again this year, so we'll see where things have progressed by then. I would second Keith's recommendation for you to find the 4 ch, Lake Mesa Quad, or splurge for the Dolby Lake Processor which has a plethora of configuration options. Additional channels could be put to good use for the center channel or surrounds. While that does leave a lot to play with and adjust, the good news is that I'm dirt cheap compared to Keith Yates. :cool:


Quote:
Anyway, the curve is nice, but not very meaningful to me... at 65dB, I am sure it's not audible below 20Hz and certainly below 15Hz it's not even detectable. I agree that although you might not hear 10Hz at 90dB, still it might mean 'something useful' to the senses, but at 75dB falling to 60dB, I would wonder if it still does anything at all for someone. Heck, I can barely stand to watch a movie at 85dB, and that's for higher freq where the ear is far more sensitive to loudness. Maybe (well not maybe) I am just deaf.
As I said in my earlier post, it was after midnight, and Noah has nearby neighboors. My guestimate would say we should have anywhere from 25-40dB of headroom above the level shown. Again, this was a pretty quick & dirty adjustment by my standards/expecations. Even so, this isn't exactly the first system in which I've seen this sort of response. The output capability is entirely dependent on the size and construction of the room, how many, and of course what type of subwoofers are used. Unfortunately I lost most measurements of such systems in a hard drive crash on my laptop this past fall. In a few months I should have more opportunities to see what can be had down low with sealed subwoofers in real rooms. I noted that I have measured various systems reaching into the 95-110dB range near 10Hz to precisely make the point that it's not always hugely useful, but it's a matter of adding 1-3 more subwoofers (+6-12dB) to get some useful levels. I should also probably note that the measurement at Noah's listening position is through his HK receiver which is known to have a high pass filter down low, and his room has large, glass windows and doors which are fairly leaky at very low frequencies.

Quote:
I would want to know what the curve looks like at your 'reference' volumes for the rest of the system.

Also, I am guessing there is a big difference between 95dB and 110dB that you measured. Apparently our dynamic range at the sub 15Hz range is only a handful or two of dB, and so 95dB might be nothing, and 110dB everything or at least detectable and impactful.
The important part to look at when increasing the level is for signs of compression. In the cases I am referring to, there was less than 2-3dB of compression at the levels mentioned. Once the level is achieved without compression, then it's just a matter of EQ to bring it to whatever relative level we prefer.

Indeed, if the main speakers are similarly up to task (not always true), there is a very significant, subjective difference between a system limited to 95dB vs. 110dB @ 10Hz. Of course 110dB + would be preferred. The part that might have been missed was that I have found that even shallow downward taper which allows content to pass down to 10Hz makes a noteable improvement over a system limited to 20Hz. Call it a much more subtle change in the direction of what we experienced on Saturday. Being the "all or nothing" guy you are (which we have all come to admire), this might seem pointless to you, but I think it worth noting for those reading along.

While you are correct that our dynamic range at low frequencies is very different, it is not only 2-3dB. What we see from looking at the equal-loudness curves is that while a subjective doubling of loudness requires roughly 10dB at 1kHz, it takes much less increase at lower frequencies, where a 10dB increase can be more than 3 times the subjective loudness. What this means is that once we get into a more audible range and not just a realm of feeling/perception, seemingly small gains can sound quite substantial.

Quote:
I suppose my conclusion after the weekend is that raw wattage and conventional cones is an exercise in maximizing dollar, space, and power consumption, leaving one frustrated in the pursuit of emotional and impactful full range bass. When you are trying to create impactful sub-20Hz with an ear and human perceptual system such as it is, go for something that moves air in volumes far beyond the ability of large paper cones that move 20mm back and forth. I just don't subscribe to the solution of putting like 8 subs or columns of woofers and expending 10-20kW to do much less than the full range of what one fan sub and 200W will do.
I would certainly agree that below 10-14Hz there is little chance of matching what the fan subwoofer can do. That said, you still need to add a subwoofer system that is capable to 20Hz or lower. Let's also not forget that you are looking at this from the strict perspective of the world of retail/consumer products. Bruce's sub is as much a customized installation as it is a "product." He does not sell the enclosure. You or a contractor have to find or construct the enclosure. You are also forgetting infinite baffle designs that are so popular in the DIY world. Tom Nousaine and others who frequent this forum have such systems which do produce the levels you describe into the 10Hz range. These subwoofers have very similar requirements to Bruce's device. While they will not offer the same sort of 1Hz performance, they do have a benefit of much greater upper frequency capability, and I would argue are a much easier installation. When using the huge volume of an attic, basement, or crawl space they don't require anywhere near the power that smaller box counterparts require. Only a bit more than the total power consumed by Bruce's device.


Quote:
Alas, there is no free lunch, and I think the major draw back of the fan sub is the fan noise that needs baffling to reduce. I am not a huge fan (had to put that in somewhere) of that aspect. But I am willing to put in the construction effort to go for it. Esp if I can hit 130dB across DC to 15 or 20Hz.... that would be sweet... and I have you to blame for that... I really didn't get hooked on the sub, truth be told, until later at night you cranked up the volume. IF for some reason, the fan sub can't be reliable at that amplitude, then it's toast for me. If it can, I will bend over hard to make it happen.
I whole heartedly agree that there is no presently available technology that can deliver the complete VLF performance that the Thigpen rotary subwoofer can. Even so, the experience this weekend should remove all doubt that sub 20Hz performance is valuable. To suggest that the gains come in an all or nothing increment seems presumptuous.

Mark Seaton
Seaton Sound, Inc.
"Make no little plans; they have no magic to stir men's blood..." Daniel H. Burnham
Mark Seaton is online now  
post #387 of 837 Old 04-25-2006, 10:14 PM - Thread Starter
AVS Special Member
 
tzucc's Avatar
 
Join Date: Sep 2002
Location: Hype Central
Posts: 3,162
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Mark, thanks for the post. I am not suggesting the gains come in an all or nothing increment, I am demanding it! I am not about to go thru the hassle of taking out the XS and ripping into lots of construction without high degree of confidence in achieving the 99th percentile solution. If I can't be confident of that, then fine, then I'll stay put with what I have. I am not positive that I have the ideal placement and EQ solution as it stands today, but I do know I measured a flat response 80 to 20Hz... I will remeasure the room down to 10Hz and see what kind of SPL's I can achieve. Take me another 2-3 weeks to get that done... stay tuned.

I agree that I need a sub solution from 80 down to 20Hz to match with the ET sub. You know I have to watchdogs, and I will sell the XS.

Do you think the 2 WD's make for a good match for the room and the ET sub? If I was to sell both of those, would there be something I could put in their place that outdoes their output. Together, I have to say, these two Dogs do pretty darn well, but I am open to suggestions backed up any measurements.

There is no possibility for IB cone subs here. The only large rear baffle oppty in my room has now been solely reserved for the ET sub. Also, it just doesn't seem intuitive that a number of cones can move even close to the amount of air that the ET sub can.

Also, do you have a room in mind which has the ideal bass solution of placement, eqpt, and EQ? I sure would like to hear the golden model for bass down to say 10Hz.

p.s. we do have some leeway in adjusting treatments... all those things are movable and basically are on hangers. FYI.

rotary subwoofer install blog ultimate subwoofer install : http://bassment.wordpress.com/ ... c
tzucc is offline  
post #388 of 837 Old 04-26-2006, 02:13 AM
AVS Addicted Member
 
noah katz's Avatar
 
Join Date: Apr 1999
Location: Mountain View, CA USA
Posts: 20,623
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 297 Post(s)
Liked: 167
"...and Noah has the scar to show for it."

Well, we'll see when the Superglue comes off :)

For the curious, the door to my equipment area has shelves on it; one of the times I was closing it after an adjustment, an electric drill fell from the top shelf and the steel belt clip punched a nice crescent through the skin of my forehead.

Morbius,

"What am I ruling out and where?"

You said "It's really a misnomer to call what is done in induction tracts on piston engines a 'Helmholtz resonator' ".

Noah
noah katz is online now  
post #389 of 837 Old 04-26-2006, 03:20 AM
AVS Club Gold
 
Rene-L's Avatar
 
Join Date: Jan 2003
Posts: 234
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by tzucc
I agree that I need a sub solution from 80 down to 20Hz to match with the ET sub. You know I have t(w)o watchdogs, and I will sell the XS.
Tzucc / others,

Do you think that only having one ET-fan as sub (downwards 20Hz) will do when matched with W/A Alexandria's (fullrange, 18Hz upwards)? So, with no other subs involved at all.

Furthermore, I repeat my previous asked question (because I really like to know), why do you think you need two ET-fan's? Is this your invention or does Bruces recommend this as the ultimate solution?

Regards, Rene-L
Rene-L is offline  
post #390 of 837 Old 04-26-2006, 06:17 AM
AVS Special Member
 
Morbius's Avatar
 
Join Date: Nov 2000
Location: Livermore, CA USA
Posts: 4,728
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 13
Quote:
Originally Posted by noah katz
Morbius,

"What am I ruling out and where?"

You said "It's really a misnomer to call what is done in induction tracts on piston engines a 'Helmholtz resonator' ".
noah,

I just mean that, in my vernacular, when someone says "Helmholtz resonator" to me - I don't think
of organ pipes and other standing wave devices.

Dr. Gregory Greenman
Physicist
Morbius is offline  
Closed Thread Ultra Hi-End HT Gear ($20,000+)

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