BOSSOBASS Raptor system 3

[dominguez1]

No surprise that with them close my low end response dropped. We knew that going in. What was surprising was that I actually felt below 10hz more with them nearfield then with them in the corners. The horse gallops in Pompeii and the ST ship roll I actually felt. It wasn't night and day between the two placements but it wasn't subtle either.

First off...full disclaimer: Not sure how my 'brand' comes off in the AVS world, but I'm somewhat of an amateur when it comes to all this stuff. What I will say is that I'm fairly good with logic and deducing things, but need the 'pros' to keep me grounded. I consider myself as having an entrepreneurial mindset...meaning, I like looking at things differently then mainstream and challenging the norm.

 

That being said...it makes sense that you felt below 10hz more nearfield as opposed to the corners. Even though your FR drops off and more closely resembles a close mic response, your FR does not represent your 'Sound Intensity' response. Meaning, if we had a tool like the Microflows to plot your SIL (Sound Intensity Level), it would look drastically different from your SPL response. In this case, your observation confirms that as even though you had less SPL at 10hz and below, the tactile feedback was more. The two quantities that make up Sound Intensity are pressure and particle velocity. Since SPL dropped, but SIL increased, it must be that PVL increased as a result of the 'nearfield' placement.

 

What I didn't expect was even with them right behind me I ran to the limits at almost the same levels as before. I attribute most of this to the ULF as no matter where you put them they take the same power to get the effect. Far field you get room gain but lose over the distance since I'm on concrete. Near field I felt it but without the room gain I'm still running out of amp. So either way I'm screwed on a slab. Solution is of course a riser or move them to a room with a suspended floor.

 

 

Curious about this...when you say you ran out of steam at the same levels as before: When you moved your subs nearfield, to you recalibrate levels or keep them the same? Obviously, if you kept them the same, you'd run out of steam at the same place. The question is: was it more tactile when you ran out of steam when the subs were placed nearfield vs in the corners?

 

My hypothesis is that there is not PVL generated with room gain. SPL increases, but PVL is a function of how close you are to the sub. So although SPL levels benefit from room gain, PVL remains the same.

 

Dave told me beforehand he doesn't like near field because you lose the room gain the ULF needs. I understood that but since I'm on a slab and he's not I figured why not try it? Plus everyone else is doing near field. Only difference is I put the whole system so I know I would have enough displacement to get the ULF output I need. 

 

So that's the question: What effect does pressure have on tactile feeling vs particle velocity?

 

Distances further away from the subs: SPL increases because of room gain, but PVL decreases because you're further away from the sub. What does that do to the SIL?

 

My hypothesis is that increased pressure is perceived as the 'weight' or under water type sensation. Whereas, increased particle velocity is more of a physical movement or 'wobble'.

 

So here was the second surprise:

 

With 40liters behind me and plenty of power I *still* didn't come close to replicating the feeling of ULF on a suspended floor. Not. Even. Close.

 

Everyone who is doing near field subs on a slab I doubt they're even feeling the ULF unless they have a riser. Even if you do are you sure what you're feeling is ULF? It was only easy for me to tell on those two scenes in particular because Dave played them at his house. It's everything combined that gives you the feeling. A floor and couch that move, displacement, power, and roll-off. After this I just highly question whether most who claim to achieve and feel ULF actually are

 

Just so everyone's on the same page, your definition of ULF is 10hz and below...

 

Given that, FWIW, I've never experienced any physical movement or 'wobble' in any HT system (my room, @laugsbach, @mktheater) at 10hz and below. It's always been the 'weight' or 'under water pressure' feeling. @laugsbach has Crowsons...those most definitely produce the wobble below 10hz..of course those are mechanically driven. He always talks about Bosso's suspended floor and the 'floating' type feeling that is NOT recreated by Crowsons...

 

All that said I did feel it more and that's why I tried it. I even told Paul I was going to keep them there. That is until I saw my response.   Honestly I thought I felt more and was laughing at how much it shook the couch and then after I saw the response I realized I wasn't getting anything from 15-25hz. In that range is a LOT of tactile feeling. I said to Paul "ya know...now I don't honestly remember if it shook more with the subs in the corners".

 

Well it just so happened that same day a friend came over. So I put on OHF and played the monument scene at ref with the subs at 10db hot. We all agreed it felt awesome. We moved the subs in the corner set the subs to 10db hot and HOLY HELL it felt way better!! I couldn't believe it. This whole week of them being nearfield I just didn't remember how they felt up front. Of course this was attributed to the FR and null. It just goes to show with movie and music transients it's hard to know exactly what frequency you're feeling. Certain ranges yes but when played together It's hard to distinguish.

 

This is very interesting that at 10hz and above you 'felt' more in the corners...my only explanation is that at the levels that you listen too, the equal loudness curves start to take effect and influence your perception. 15-25hz is certainly audible at those levels, especially running +10db hot. Perhaps you had lower SIL from an inaudible standpoint, but you perceived it as being louder as the added room gain from being in the corners produced more audible impact that you perceived as 'more'.

[dominguez1]

Hey Dom before I forget I did want to say some more about phase and PVL.

 

It was odd when I had the Raptor stack behind the couch that I didn't get the increase in tactile sensation I thought I was. Actually nowhere near what I though I would get. What makes it even worse is Ethan has his A7s-450(still going  ) firing directly into his couch and you feel it more then my subs, which are of course much more capable. Now don't get me wrong that thing drops like a rock around 25hz so there's no comparison between it and the Raptors below that, but above 25hz with it firing directly into the couch is definitely more tactile.

 

I was thinking though the Raptors fire up and down. Most guys running near field, or all of them I'd imagine, are using subs that are front-firing. IF running near field increased the PVL then it shouldn't matter which way the drivers are firing correct?? One foot away or whatever distance near field is considered should be a lot more tactile then with them 10ft away in the corners if PVL is indeed higher when the subs are placed closer.

 

I can't for the life of me think why that would be since even with the subs stacked and a decent FR it was still not impressive

 

Were your Raptors nearfield against a wall or open space? I'm guessing that they were more open space? If so, my hypothesis is: PVL is a vector quantity; meaning that it has a direction. If they were in open space, the direction would be where the driver's were firing...in your case up and down. The associated PVL would scatter in 360 degree direction, giving you less impact as your brother's A7S-450 which is against a wall? The wall would perhaps 'redirect' any rampant PVL toward the couch, further focusing the SIL at the couch?

 

My FV15HPs have both ports and driver firing directly into my couch, but there is also a wall behind them to reinforce the PVL? Just guessing here of course.

 

 

So I'm thinking maybe all this has to do with Dave's theory of progressive constructive reflections. Dave correct me if I'm wrong but you say the rooms longest dimension has nothing to do with when you'll see boundary gain. It's just as the waves grow bigger the lower in frequency you go, they also become more constructive which is where your boundary gain comes in. Dave overlayed I think 7 or more different frequency responses from guys with varying types of room construction and size and almost ALL had gain at the same point. So if thats the case then if the driver is firing directly into the back of the couch it's taking the entire brunt of the wave before any part of those waves "escape" the room. However, if placed away from the couch no matter the SPL you are still not getting the full wave so to speak. It's being transferred into the walls around. Even though bass is omnidirectional, with the driver firing directly into the couch one could assume you would get more tactile sensation. Since a lot of what we feel in movies is above 20hz and escapes the room more than below 20hz once put behind the LP you of course feel them more.....

 

I also could be talking out of my arse since most of this stuff is over my head. 

Don't know! Your arse is as good as mine!

 

 

One more thing though. Dom I want to be clear on the out of phase theory. You said you can get the same PVL running out of phase and at 16db lower then running in phase. Again, correct me if I misunderstood, but you then said you could use that headroom elsewhere, like for ULF. My point was that you don't gain 16db of headroom at that frequency or any other when you do that. You lose that 16db since they're out of phase and fighting each other. Also I'm curious did YOU actually feel a difference even though the "meter" read different?

I'm still not sure if we're on the same page here! 

 

3ld00..said it best. PVL is generated by how much exertion is occurring by the sub. From that perspective, the sub is going to exert the same amount of energy whether it is in phase or out of phase....it doesn't care. It's mechanically producing energy, and the phase at the LP is determining whether or not that energy is efficent (in phase), or inefficient (out of phase).

 

My point was that for these ultra headroom systems, there is a lot of 'exertion' that is simply going unused. In my example, when in phase it takes a lot less exertion to produce the same SPL compared to a sub that was out of phase. However, it's my hypotheses that PVL is directly related to exertion. So in efficient systems (in phase), given the same SPL, the sub will exert less than a system that is out of phase. Since that efficient system exerts less, and PVL is directly related to exertion, then there will be less PVL compared to a system that is out of phase. A system out of phase, will require more exertion (and more PVL as result) to produce the same level of SPL.

 

For those uber HT systems that have massive headroom, by suggestion was to not let that go unused, and try and take advantage of that by running more out of phase to increase PVL levels and resulting SIL and tactile feedback.

 

Did I ultimately 'feel' a difference? In that specific test I did not sit in the couch to take subjective impressions. However, I will tell you in my many hours of listening to different FRs in my room, some are 'heavier' and more tactile than others give the same FR.

 

 

I think it would be awesome if one of us got ahold of the Microflown meter. Strange they're so hard to get ahold of though. I just don't know how much trust we should even put in measurements with a phone. Not trying to be a smartass but seriously it's a phone...I can't imagine something that is primarily used for talking, texting, and porn surfing could measure anything remotely accurate for sound and/or velocity. 

 

That's hilarious! Dude, that made laugh out loud for real...

[wth718]

Would the Bosso amp be enough to power 4 FTW-21s? This is on my radar as a power solution down the road.

[Bossobass Dave]

Distances further away from the subs: SPL increases because of room gain, but PVL decreases because you're further away from the sub. What does that do to the SIL?

 

My hypothesis is that increased pressure is perceived as the 'weight' or under water type sensation. Whereas, increased particle velocity is more of a physical movement or 'wobble'.

 

 

This may help: distance is governed bu the Inverse Square Law. Every doubling of distance reduces SPL by -6dB. What this means is the frequencies in a room that are governed by ISL drop but the ULF, which is not governed by the ISL stays the same, relative to seat placement in and around standing wave phenomena.

 

A simple experiment where you measure close mic and then move the mic towards your seat, doubling the distance from the sub each time:

 

 

The frequencies <10 Hz are the same everywhere in the room. With a corner placement and seating 4M from the subs, applying the amount of L/T signal shaping that best compliments the Room Gain Profile will result in a flat response. The nearer you move the subs toward the seat, the more the frequency response will revert to the sub's native response.

 

So, if Adam kept the signal level the same, the response <10 Hz was the same, but >10 Hz was higher.

 

 

The second part of the quote, yes, except when the pressure wave moves the structure you're sitting on.   It's pretty hard to move masonary walls and concrete floor with subwoofer drivers because their resonant frequencies are well out of band and they are extremely lossless vs a wood frame structure, which more likely than not will have resonance in band.

[Bossobass Dave]

Would the Bosso amp be enough to power 4 FTW-21s? This is on my radar as a power solution down the road.

 

Make sure you get 4 ohm drivers (dual 2 ohm or single 4 ohm) so that you can wire 4 of them to 4 ohms nominal load into the amp in bridged mode and the A-14K will power them with it's thumb up it's ass.

 

I believe the FTW-21 is a single coil 4 ohm config, Re = 3.2 ohms, so yes, good to go...

[wth718]

Make sure you get 4 ohm drivers (dual 2 ohm or single 4 ohm) so that you can wire 4 of them to 4 ohms nominal load into the amp in bridged mode and the A-14K will power them with it's thumb up it's ass.

 

I believe the FTW-21 is a single coil 4 ohm config, Re = 3.2 ohms, so yes, good to go...

Appreciate it! I suspect I will be in for 2 in the coming months.

[Madaeel]

That being said...it makes sense that you felt below 10hz more nearfield as opposed to the corners. Even though your FR drops off and more closely resembles a close mic response, your FR does not represent your 'Sound Intensity' response. Meaning, if we had a tool like the Microflows to plot your SIL (Sound Intensity Level), it would look drastically different from your SPL response. In this case, your observation confirms that as even though you had less SPL at 10hz and below, the tactile feedback was more. The two quantities that make up Sound Intensity are pressure and particle velocity. Since SPL dropped, but SIL increased, it must be that PVL increased as a result of the 'nearfield' placement.

 

I understand that PVL must have increased, but what I don't get is why I only felt below 10hz more. Had me scratching my head. Again if PVL increases as you get closer to the sub then why did only those freqencies feel better?

 

Curious about this...when you say you ran out of steam at the same levels as before: When you moved your subs nearfield, to you recalibrate levels or keep them the same? Obviously, if you kept them the same, you'd run out of steam at the same place. The question is: was it more tactile when you ran out of steam when the subs were placed nearfield vs in the corners?

 

I had them 10db hot in the corners and behind the couch. Both were calibrated to the same level. Problem was my FR was shit. I just thought I wouldn't have to turn it up even close to what it was before to get the same effect.

 

My hypothesis is that there is not PVL generated with room gain. SPL increases, but PVL is a function of how close you are to the sub. So although SPL levels benefit from room gain, PVL remains the same.

 

So no matter the direction the driver is firing I should have felt much more then I did. I didn't and if you look at my FR that tells the story. That huge dip from 15-25hz is a LOT of the tactile feeling range. IOW it looks like it is more FR then PVL.

 

Distances further away from the subs: SPL increases because of room gain, but PVL decreases because you're further away from the sub. What does that do to the SIL?

 

My hypothesis is that increased pressure is perceived as the 'weight' or under water type sensation. Whereas, increased particle velocity is more of a physical movement or 'wobble'.

 

Just so everyone's on the same page, your definition of ULF is 10hz and below...

 

Given that, FWIW, I've never experienced any physical movement or 'wobble' in any HT system (my room, @laugsbach, @mktheater) at 10hz and below. It's always been the 'weight' or 'under water pressure' feeling. @laugsbach has Crowsons...those most definitely produce the wobble below 10hz..of course those are mechanically driven. He always talks about Bosso's suspended floor and the 'floating' type feeling that is NOT recreated by Crowsons...

 

Yah sorry about that I meant below 10hz. See that's the other problem. I don't think most guys have or are experiencing ULF. I don't get any feeling and certainly not an 'under water pressure' feeling. Maybe if you run sine waves I guess it would give you that. The Hulk Cannon scene is proof. Those 13hz hits are brutal in my room and no one else yet I've seen mentions that. It is heavy so to speak but the waves go through you and it's not some obscure pressure. In Dave's room there is no need to guess since he's on a suspended floor. There's no pressure feeling. It's an unbelievable wobble that scares you when it hits. When I played the ST ship roll scene and Pompeii horse gallops I got a taste of what it's like in his room. It was awesome and I wanted more.  Need a riser in that room...

 

This is very interesting that at 10hz and above you 'felt' more in the corners...my only explanation is that at the levels that you listen too, the equal loudness curves start to take effect and influence your perception. 15-25hz is certainly audible at those levels, especially running +10db hot. Perhaps you had lower SIL from an inaudible standpoint, but you perceived it as being louder as the added room gain from being in the corners produced more audible impact that you perceived as 'more'.

 

I just think if you look at the FR that tells it all. That null is ugly!

 

 

Were your Raptors nearfield against a wall or open space? I'm guessing that they were more open space? If so, my hypothesis is: PVL is a vector quantity; meaning that it has a direction. If they were in open space, the direction would be where the driver's were firing...in your case up and down. The associated PVL would scatter in 360 degree direction, giving you less impact as your brother's A7S-450 which is against a wall? The wall would perhaps 'redirect' any rampant PVL toward the couch, further focusing the SIL at the couch?

 

My FV15HPs have both ports and driver firing directly into my couch, but there is also a wall behind them to reinforce the PVL? Just guessing here of course.

 

Yah they're in open space. Actually Ethan's is in the middle of the room but again it's right up against the couch and firing right into it.

 

Don't know! Your arse is as good as mine!

 

I'm trying to wrap my head around PVL but right now to me it seems its simply FR more than anything.

 

 

 

I'm still not sure if we're on the same page here! 

 

3ld00..said it best. PVL is generated by how much exertion is occurring by the sub. From that perspective, the sub is going to exert the same amount of energy whether it is in phase or out of phase....it doesn't care. It's mechanically producing energy, and the phase at the LP is determining whether or not that energy is efficent (in phase), or inefficient (out of phase).

 

My point was that for these ultra headroom systems, there is a lot of 'exertion' that is simply going unused. In my example, when in phase it takes a lot less exertion to produce the same SPL compared to a sub that was out of phase. However, it's my hypotheses that PVL is directly related to exertion. So in efficient systems (in phase), given the same SPL, the sub will exert less than a system that is out of phase. Since that efficient system exerts less, and PVL is directly related to exertion, then there will be less PVL compared to a system that is out of phase. A system out of phase, will require more exertion (and more PVL as result) to produce the same level of SPL.

 

For those uber HT systems that have massive headroom, by suggestion was to not let that go unused, and try and take advantage of that by running more out of phase to increase PVL levels and resulting SIL and tactile feedback.

 

Did I ultimately 'feel' a difference? In that specific test I did not sit in the couch to take subjective impressions. However, I will tell you in my many hours of listening to different FRs in my room, some are 'heavier' and more tactile than others give the same FR.

 

But in your test you turned up the main volume another 16db after switching them to out of phase to get a higher reading.  That is my problem with you saying those with massive headroom should try this. I have mssive headroom but that gets eaten up quickly when you're flat to 10hz let alone a couple db down at 5hz. Again even if SIL went up with less SPL, which in turn meant the PVL went up, the meter didn't read higher. You raised the volume. If switching the subs out of phase resulted in a more tactile sensation without doing anything else then yes I'd agree. But it didn't. Even if you don't need to raise the MV that high to get the same SIL you're asking for trouble. IOW it's smarter to just run subs near field if you need that shaking. Or you can get Crowsons which are the devil I'm told. Though I don't think it'd be that hard for those with multiple ID subs to try out since they all have phase adjustments on them. Of cousre we'd jsut need a FR to confirm they're not hearing FR.

 

 

That's hilarious! Dude, that made laugh out loud for real...

 

Funny thing is I did download that Vibsensor Coolrda found on his iphone.

 

 

The second part of the quote, yes, except when the pressure wave moves the structure you're sitting on.   It's pretty hard to move masonary walls and concrete floor with subwoofer drivers because their resonant frequencies are well out of band and they are extremely lossless vs a wood frame structure, which more likely than not will have resonance in band.

 

Perhaps I felt below 10hz more with them nearfield since like I said I'm feeling more of the wave itself before it escapes the room?? I'm just guessing here since until we have a meter we won't know how PVL "works".

[dominguez1]

Hey Madaeel,

 

I'm with you...it's tough to determine how PVL is reacting without measuring directly. Would love to get a Microflown in hand that's for sure.

 

Although the phone is indirect and certainly not perfect, it's the best thing we have that I know of to help widdle this PVL mystery down.

 

If you're willing, I'd love to be able to take the subjectivity of 'tactile feeling' out of the equation in your tests, and quantify it better with an app on your phone. Not doubting at all what you felt, but it's just hard to quantify. I'd also suggest running sine waves instead of movie content so we can essentially get a mock PVL response. Movie content is great, it's just so complex to really isolate what is going on.

 

What I will say regarding your impressions: SIL is definitely related to SPL, so your FR does in fact play a part. The null you have is most definitely having an impact of what you feel as it is Sound Intensity causing this tactile feeling, not just PVL. So even though PVL may be higher since it is closer, if SPL is so low (as in your null/dip) it will definitely impact what you feel as well (SIL = SPL * PVL).

 

Jumping on a plane, so will address your other response in a bit.

[Shredhead]

While we're broscience-ing here...

 

I don't think we detect particle velocity for the most part.  10kHz seems pretty intense to me at the same SPL as 120Hz.  I would guess 1k, 5k, & 10k, wouldn't show up as much on a Microflown at the same distance and SPL matched with a sub producing 40Hz.  It seems we only sense the particles "velocitying" very close to a driver(s) that is moving a considerable amount of air. 

 

Even Ethan's setup...  An 18" firing at your back isn't a very good test because it's firing into a couch which has a resonant frequency like anything else and maybe it acts as a buffer that absorbs the desired effect for the other frequencies. 

 

Even if you set up some ultra nearfield subwoofer headphones for nearfield tactile effect, your frequency response would be butchered and source material would not be reproduced accurately because it's mixed for mainly SPL in studios.  Dom, I understand your idea about letting separate subs fight each other with phase to keep SPL down and increase PV, it is an interesting experiment for sure.  It would have to be a serious system to waste all that power and displacement and still keep up with WOTW at reference SPL.  Like maybe Popalock's previous insane, house destroying setup?

 

Another idea would be to get a high excursion 12", give it a 2nd order low pass at 15Hz and fire it at your back.  It shouldn't butcher your frequency response from your main subs too much and it would be a lot cheaper.  It is still firing the piston into a buffer before it hits your body but short of hanging it above your head or firing it at your crotch from the floor...

[dominguez1]

Damn puddle jumpers...no wifi..

 

The phase scenario: I feel good that we are on the same page here on how it works or rather how I assume it works based on my tests.   

 

- My point of this test wasn't to give a priority of what tactic can increase tactile feeling the most. The point was to identify another potential way to increase tactile feedback. Having said that, 100% agreement with you that nearfield placement, floating risers, crowsons, etc. would be a much more effective route.

 

- The frequencies that this out of phase opportunity could occur would not be typically 20hz and below (ULF) frequencies. Depending on room, they would typically be in the LF regions as I explained here. Didn't get much feedback here, so don't know if I'm thinking about it in the right way, but it does support my observations as well as what others have observed.

 

- As far as turning up the main volume, yes this was absolutely the reason sound intensity increased in my test. And like you said, when I didn't turn up the mv, SIL stayed the same...agree. But this is exactly my point. In the LF regions where there is typically more headroom, an out of phase condition provides the opportunity to increase SIL and tactile feeling while keeping SPL the same. For example: you like to run your subs +10db hot across the entire pass band I assume. If you ran just the LF region at +20db hot, the sound would likely not blend very and sound too bass heavy compared to everything else...but, you love the added tactile feel it gives you when you run the LF region 20db hot. In this fictitious example, what if you could raise the tactile feeling of the LF region, but keep they same SPL so that it blends with the rest of the speakers at +10db, or the level you normally listen to? In an out of phase scenario, you could do this to a degree: keep SPL levels the same, but raise SIL by taking advantage of an out of phase condition.

 

- Whether or not people have the headroom to do this or not is really a different question. My point was, if the headroom is available, this could be a way to take advantage of that to make it more tactile and raise SIL. I do this in my room, and I find it quite effective. I wish I could say I did it on purpose...but it was pretty much dumb luck.   

[Madaeel]

You do see on that app that if the phone itself is vibrating then the results are almost worthless. I just can't put much trust in a phone to measure vibration accurately. There's a reason the ACO mic cost $2k.  

 

It would be easy for anyone with multiple subs and phase adjustments to try it though. My subs are seen as one unit so I can't even check to see a difference.

[Madaeel]

 It seems we only sense the particles "velocitying" very close to a driver(s) that is moving a considerable amount of air. 

 

  Dom, I understand your idea about letting separate subs fight each other with phase to keep SPL down and increase PV, it is interesting for sure.  It would have to be a serious system to waste all that power and displacement and still keep up with WOTW at reference SPL.  Like maybe Popalock's previous insane, house destroying setup?

 

Another idea would be to get a high excursion 12", give it a 2nd order low pass at 15Hz and fire it at your back.  It shouldn't butcher your frequency response from your main subs too much and it would be a lot cheaper.  It is still firing the piston into a buffer before it hits your body but short of hanging it above your head or firing it at your crotch...

Yah this is what I'm saying. Most guys are already boosting their LF. You say to boost that frequency even more.  I just don't think this is plausible in any scenario except as Shred mentioned maybe Pop's. I guess maybe some other guys with DIY capable subs could try it as well.

[dominguez1]

You do see on that app that if the phone itself is vibrating then the results are almost worthless.

Not sure what you mean? I have an android...no iphone.

 

Every vibration app will have a certain tolerance level or noise floor. Above the floor, should be valid.

[dominguez1]

Yah this is what I'm saying. Most guys are already boosting their LF. You say to boost that frequency even more.  I just don't think this is plausible in any scenario except as Shred mentioned maybe Pop's. I guess maybe some other guys with DIY capable subs could try it as well.

Not sure why you think it's out of the realm of possibility. There are a number of HT systems that have much greater headroom than what you're used to...@mktheater comes to mind.

[Shredhead]

- The frequencies that this out of phase opportunity could occur would not be typically 20hz and below (ULF) frequencies. Depending on room, they would typically be in the LF regions as I explained here. Didn't get much feedback here, so don't know if I'm thinking about it in the right way, but it does support my observations as well as what others have observed.

 

 

I am not a master of phase yet so I can't contribute much there.  I know I have seen phase curves that go anywhere from 60 to 180 degrees from 2Hz to 200Hz but usually that ends up affecting the signal like a parametric band of EQ or a low shelf filter.  Maybe it is possible in the digital domain to affect phase variably from 2Hz to 100Hz but not affect the EQ of the signal to be able to dial in the desired SPL response between the 2 subs?

 

Would you be down for just a listening test of different source material since a Microflown is not available.  Maybe A/B stuff with a high filter like superman and then full bandwidth?  You seem better at describing sound than I am (I dug the underwater reference) and it's better than nothing. 

[dominguez1]

While we're broscience-ing here...

 

LOL..probably!! It's fun to bropythesize tho.. 

 

Even if you set up some ultra nearfield subwoofer headphones for nearfield tactile effect, your frequency response would be butchered and source material would not be reproduced accurately because it's mixed for mainly SPL in studios.  Dom, I understand your idea about letting separate subs fight each other with phase to keep SPL down and increase PV, it is an interesting experiment for sure.  It would have to be a serious system to waste all that power and displacement and still keep up with WOTW at reference SPL.  Like maybe Popalock's previous insane, house destroying setup?

I dunno...some people have a real sickness when it comes to bass. Notnyt, bassthathz, japandave, mktheater, n8dogg, etc. They have loads of headroom that just goes unused (well, mostly anyway)...my point in all of those types of systems, this might be a way to take advantage of the extra headroom. 

 

My system pales in comparison, but I'm able to take advantage on a smaller scale anyway...

[3ll3d00d]

I am not a master of phase yet so I can't contribute much there.  I know I have seen phase curves that go anywhere from 60 to 180 degrees from 2Hz to 200Hz but usually that ends up affecting the signal like a parametric band of EQ or a low shelf filter.  Maybe it is possible in the digital domain to affect phase variably from 2Hz to 100Hz but not affect the EQ of the signal to be able to dial in the desired SPL response between the 2 subs?

 

You can certainly create filters that correct/change phase only. You need something that can execute FIR filters and a means to generate them. OpenDRC + RePhase is the standard combo, there is an overview on the minidsp site - http://www.minidsp.com/applications/advanced-tools/rephase-fir-tool- and there is the master thread on diyaudio which is extremely long - http://www.diyaudio.com/forums/multi-way/221434-rephase-loudspeaker-phase-linearization-eq-fir-filtering-tool.html 

 

RePhase has a "paragraphic phase EQ" feature that lets you dial in arbitrary phase changes.

 

I made this point on avs but implementing this sort of change when you have multiple subs in play, as you must do to have the headroom required, and maintaining a stable/smooth FR (which you definitely can hear) is likely to be fairly challenging to put it mildly.

[Madaeel]

^^^^The truth comes out. Not only is that hard to accomplish but regardless of your headroom, you boost a range of sub frequencies, and I'm tellin you either the amp clips to hell or you're buying new drivers. Watching Earth to Echo or Interstellar would heat those coils up quick! Both Dave and myself literally jumped for the remote when that scene in EtE hit.

 

Dom all those guys you mentioned have near field subs or transducers. I just dont see the point to this. I'm just worried people will try this and cook something.

 

I'm still interested to see what part PVL plays in this and how much though.

[Bossobass Dave]

I haven't been paying a lot of attention over the past months so I need to ask:

 

Dom, have you tried the 21" driver only near field vs far field and if so, what was the result?

 

[dominguez1]

You can certainly create filters that correct/change phase only. You need something that can execute FIR filters and a means to generate them. OpenDRC + RePhase is the standard combo, there is an overview on the minidsp site - http://www.minidsp.com/applications/advanced-tools/rephase-fir-tool- and there is the master thread on diyaudio which is extremely long - http://www.diyaudio.com/forums/multi-way/221434-rephase-loudspeaker-phase-linearization-eq-fir-filtering-tool.html 

 

RePhase has a "paragraphic phase EQ" feature that lets you dial in arbitrary phase changes.

 

I made this point on avs but implementing this sort of change when you have multiple subs in play, as you must do to have the headroom required, and maintaining a stable/smooth FR (which you definitely can hear) is likely to be fairly challenging to put it mildly.

Wow...good info. Thanks 3ll3d00d. That does seem to be fairly complex based on what you said above.

 

However, in my case, it was fairly easy in my room, and repeatable. I have my FTW21s on one phase adjustment, and have the FV15HPs on another. Leaving them in phase, audyssey couldn't remove the peak at 27hz, and my elemental designs eQ.2s couldn't remove the peak either. So prior to running audyssey, I set the phase on both pairs of subs to tame the peak (out of phase) before audyssey. I then ran Audyssey XT to flatten it out. Viola! 

 

Perhaps my situation is unique...don't know, but would love someone else to try. 

 

 

 

^^^^The truth comes out. Not only is that hard to accomplish...

 

LOL, yes...if I had to perform the techniques that 3ll3 described, I'd probably be out as well. But like I said, in my room and in my experience, it wasn't difficult.

 

 

...but regardless of your headroom, you boost a range of sub frequencies, and I'm tellin you either the amp clips to hell or you're buying new drivers. Watching Earth to Echo or Interstellar would heat those coils up quick! Both Dave and myself literally jumped for the remote when that scene in EtE hit.

 

Dom all those guys you mentioned have near field subs or transducers. I just dont see the point to this. I'm just worried people will try this and cook something.

 

I'm still interested to see what part PVL plays in this and how much though.

 

 

I don't know what to say that I haven't said already: if you're concerned about cookin' drivers or clipping amps when in phase, then that is a sure sign that you don't have enough headroom for this experiment! Make no mistake...this is by no means a knock on your system or some underhanded comment that you don't have ample headroom...you do! In fact, I would trade in my system for Raptors in a heart beat!

 

This is for those systems that have enough headroom where there is never a fear of bottoming out or clipping the amp at the highest levels of playback...for them. Does this mean you have to have an mk type system? Actually no...it might be that a person who's listening volumes never exceed -15db MV, but have above reference capabilities, just going unused.

 

I really have no dog in this fight and am bringing it up for those that may be interested in trying something unconventional to potentially get more out of their systems. Will it work for other rooms? Will it be as easy as what I did? Will it be worth it? Don't know...but only one way to find out. I had positive results from it and wanted to share a potential new lever to pull to increase tactile feeling.

[dominguez1]

I haven't been paying a lot of attention over the past months so I need to ask:

 

Dom, have you tried the 21" driver only near field vs far field and if so, what was the result?

 

Hey Dave,

 

The only time I ran the FTWs nearfield and farfield were the original PVL tests in the ULF thread over a year ago. Other than that, the FTWs have always stayed put further away.

[maxmercy]

I would like to hear what you guys think of tactile feeling from 50-500Hz, where small room effects rob us of so much SPL/SIL/Impact.  The most tactile movie presentation I ever heard was TF2 at this theatre:

 

 

An old small town Texas theater that was completely renovated and THX certified.  'Punch in the chest' was a very mild way to put it.  More like 'Mule Kick to the chest'.  I have never felt more impact save for at hearing-damage-loud large outdoor concerts.  I know the response did not dig below 25Hz, but it was impressive nonetheless.  So many HTs simply cannot do this, and it may be due to room size and the inherent cancellations therein.

 

Thoughts?

 

JSS

[Madaeel]

50-500hz?? You BLASPHEMER!! You insult the LF and ULF gods and all the goodness they give us!

 

That is odd a theater that size can give you that impact and our theaters can't. You don't happen to know what they used in there do you?

[SME]

I'm drawing a house now of concrete construction with a dedicated HT and you can bet the farm I'm putting the seating on a suspended wood structure that's designed to offer support headroom but with flex room as well.

 

I am contemplating for my "dream" HT room, if/when I ever build it having a suspended wood floor with a good amount of damping and a set of carefully calibrated tactile transducers.  I'd probably aim to calibrate them so that they are always at the threshold of perception versus the sound.  I have a hypothesis that the two (sound versus vibration) are capable of masking one another in perception.  If the two are balanced just right at all frequencies and there are no serious ringing problems with either, the bass will "sound" the best.

[SME]

Probably one reason the theater sounds so good is that it's a big enough space that the room doesn't influence the response as much.  I have a hunch that a flatter bass response gives more kick.  Why?  It's because the strongest bass transients have energy spread widely across the spectrum.  When the response is flat (and minimum phase, technically speaking) all that bass energy arrives at once, which is a very moving experience to say the least.  On the other hand, any peaks or dips in the response also cause the energy to not all arrive at once and to be smeared out in time so the instantaneous pressure is not nearly as high.

 

Strong kick can be achieved in a smaller room, but it requires very flat frequency response without excess phase issues.  When I got my MiniDSP 2x4 configuration optimized with separate EQ for my 2 deep bass subs (up front) and 2 mid bass subs (near-field), I was able to achieve +/-2 dB from 20-100 Hz with fairly minimal (and smooth) excess group delay.  The subjective difference was very apparent on impulsive and transient sounds as well as wide-band noise.  The bass also sounded louder for a given calibration level.

 

Ideally you want to be as flat as possible all the way up to 200 Hz and make sure your mains and amps have the headroom to handle the 80-200 Hz material as well.  Much if not most "kick in the chest" feeling comes from bass in this range.  Both bass traps and aggressive EQ will almost certainly be necessary to get the best response here unless your room is especially large.  Likewise, subs in multiple locations (ideally with individualized EQ, but this is *very hard* to do right with currently available software) are practically essential for the 40-80 Hz range which contributes plenty of the kick as well.

 

Edit: Now I see you say 50-500 Hz!  I have little doubt that one can "feel" > 250 Hz, but I'm not sure I want to experience that kind of sound level.  I have experienced some pretty strong chest sensations from sound around 200 Hz though.  One of the Danley recordings of a live parade evokes it pretty well.