Your Home Theater ULF Score - Page 22 - AVS Forum

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Subwoofers, Bass, and Transducers

Brian Fineberg's Avatar Brian Fineberg
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Quote:
Originally Posted by neutro View Post

I knew I was missing something biggrin.gif

But for the record, in a 1680 cu ft room, a single SB-12 gets 0.3, 0.3 and 0.2 SI equivalents at 12.5, 16 and 20 Hz respectively, thus 5600, 5600 and 8400 cu. ft. per SI, and 1.5 star each. Interestingly, the cost per star significantly lower too ($743 for 12.5 Hz for the dual Pluses vs $433 for the single SB13).

oops i had the room measurements..for my room in the calc, when I checked yours ...sorry tongue.gif

EDIT: wait sb12 or sb13?
neutro's Avatar neutro
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Quote:
Originally Posted by Brian Fineberg View Post

EDIT: wait sb12 or sb13?

SB12 of course. Where did I say SB13? wink.gif

EDIT: dammit, my edit doesn't propagate to your quote.
ironhead1230's Avatar ironhead1230
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Quote:
Originally Posted by neutro View Post

I have a few comments about the score by the way. I totally understand that the score is not perfect and is only a quick figure that help us compare setups.

The main question I have is that the score is normalized by room volume. It's intuitive that the same gear in a smaller room will result in more SPL. But is the effect directly proportional to volume? I.e. is the same setup placed in a room half the volume automatically twice louder (i.e. +6 dB)? I understand specifics like materials, furniture and room shape can also affect levels at the main listening position, so let's assume an empty rectangular room.

The part about normalizing to a popular sub (the sealed SI) is a good idea too, yet it's still a bit abstract as I'm pretty sure the majority of us here have never seen nor heard that idealized sub. So while it gives us an idea (wow, didn't now that it would take 3 sealed SI's to hit the 16 Hz level I get with my two ported 12"), the score could also be expressed as cu. ft. per max burst dB SPL at a given frequency. Or, if we want a score that goes *up* when it's better, simply the inverse, i.e. max burst dB SPL (or equivalent SI's) per cu ft. Anyway, the stars is the final score and those can be computed in cu. ft. per equivalent SI, or in max burst dB SPL per cu. ft. ... the conversion is direct anyway.

Also there is no reason to limit this to the ULF portion, unless perhaps the room size has much less importance for mid-bass and there would be no reason to normalize room size?

I was just working on posting something very similar. This thread is being referenced a lot now and some are using the scores and output estimates as absolutes. Comparing subs down to the db. Until now, there has really been no testing to see if these methods are valid and if room volume alone makes as large an impact as reflected in the ratings. I think its time we attempt to verify these scores using speclab captures. We could try and pick a clip or two that highlight the different frequency scores and see what people's setups actually do during playback. I started a thread awhile ago to try and put a procedure together to take mic'd speclab captures, but nobody else seemed very interested. I recently found my first attempts with speclab from the PA sub GTG last year. Looking through them again, I think it is worthwhile to revisit.
MKtheater's Avatar MKtheater
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Well, I don't own a meter that can read how loud I could play. I know people can play louder than me because if I go louder the room has too much pressure and my theater doors will open if not locked and they are heavy!

BTW, if we include risers and such it will lower the scores but unless you are on the edge of a class your class won't change. I would become a 126 at 10hz, 118 at 12.5 and 16hz. My class does not change.
neutro's Avatar neutro
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Ultimately the score can be replaced by max sweep frequency measurements at your listening position. Only then will you have the whole story, and if you already have the gear to take accurate speclab measurements, then I guess you can also load REW and perform max output sweeps.

However, there are drawbacks to that. First, it's pretty involved, and close-to-max output FR measurements at the MLP are most often already posted by the guys with the 5-star setups smile.gif It's pretty far from the quick back of the envelope type estimate that the score provides. Second, some people (me included) can't really do a max sweep. Third, if the goal is to condense your setup in a single metric, you still have to convert the FR into a score / stars. Fourth, the most interesting / funny part of the ULF score cannot be achieved by measurements: it's the what-if! What if I had four JTR Captivators in my 1680 cu ft room? biggrin.gif That spreadsheet gives us a quick glance at what can be achieved for us who are contemplating an upgrade. (Disclaimer: no I'm not.)

Still, I totally agree with you about at least verifying the effect of room volume. It is the major driver in the current ULF score. What if SPL varies with the square root of room volume instead? That changes everything. I for one would love experimental confirmation but I'd settle for a theoretical argument from acoustics and physics.

It's just that subwoofer don't act like pistons. I agree that for a given piston displacement, in a static situation, half the room volume will yield double the pressure level induced by the piston displacement inside the room. But our rooms are not perfectly sealed, and the sub's piston displacement is actually negligible compared to the total room volume, as evidenced by the fact that all our subs have pretty poor performances at 0 Hz. (Unlike rotary subwoofers by the way... biggrin.gif) So pressure level achieved by our subs is a dynamic phenomenon and linked to the acoustical energy pumped by the driver. How that is affected by room volume is not straightforward for me.
MKtheater's Avatar MKtheater
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The room matters because just imagine putting two Caps in a commercial cinema, not put them in a closet, which one will be louder? Same subs though.
MKtheater's Avatar MKtheater
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I can not take max sweeps as my meter does not go that high or my mic will clip anyways.
ironhead1230's Avatar ironhead1230
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Quote:
Originally Posted by MKtheater View Post

The room matters because just imagine putting two Caps in a commercial cinema, not put them in a closet, which one will be louder? Same subs though.

I am definitely not saying the room doesn't matter, just that it would be a good idea to try and verify how the ratings are being calculated. Especially since the ratings are being used to justify what subs can hit "reference" or not.

For example, using the current ratings, to achieve "reference" output at 20hz in my space I would need 6 submersives. Maybe I am wrong, but that does not seem right.
MKtheater's Avatar MKtheater
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That must mean your room is enormous. In my room two eD A7S-640's could hit reference at 10 hz.
neutro's Avatar neutro
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Of course the room has a tremendous importance. We are just arguing about the specifics. I don't know enough about acoustics to have a clear idea. As I see it, there are two factors in play. The first is distance: sound pressure drops as the inverse of the distance. If you're twice farther, SPL drops by half (-6 dB). But that's not all, since if that were the case, the distance to MLP would be the main driver. The other factor is reflections on the wall, ceiling and floor surfaces which has a reinforcing effect. This is complicated by the resonances and room modes a bit, but if a wall is farther, then the reflection will also come from further. Perhaps this is the basis for the volume normalization.

Then again, you could have a room of infinite volume (e.g. parking lot) and still have some great ULF, whereas this ULF score would simply be infinite cu. ft per SI equivalent (0 star). This is just to show how things break down if you push the idea to the limit, while still acknowledging that this is not an interesting case (unless you have an outdoor home theater I guess). On the other side, if the volume is sufficiently small, you could get a very large ULF score. Get in a 200 cu. ft. closet with an SB12 and there you go, 4.5-star setup. I wonder if that would really give me reference levels @ 12.5 Hz? Again, this is not a very interesting scenario, so the direct proportionality with volume might still be warranted for most home theater rooms.
MKtheater's Avatar MKtheater
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It does not matter whether nearfield, farfield, etc.. If we all calibrate to reference or using auto EQ or whatever, we all will get the same spl at the seats. Nearfield subs will need much less power to do so or less of them. Any 5 star system can play over reference, so I just ask whoever wants to audition how loud do they want it. Kid level, wife level, reference level, MK level(reference with subs 5 dBs hot), or plug your ears level because it will hurt. In my room 10 dBs hot with the IB hurts my ears and that is from bass pressure!
Spanglo's Avatar Spanglo
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Quote:
Originally Posted by MKtheater View Post

The room matters because just imagine putting two Caps in a commercial cinema, not put them in a closet, which one will be louder? Same subs though.

Wouldn't it matter how far you're sitting from the two Caps in a commercial cinema? Assuming the Caps were positioned up front, it would be reasonable for the front seats to get reference, but that would be unlikely for the back row being so far away.
neutro's Avatar neutro
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Well if we neglect standing waves (room modes) for now, the effect of boundaries in a room is to reflect sound waves. As such, if the reflection is perfect (no absorption), then it is as if there were mirror images of your sub in imaginary rooms on each side (and up and down) of an hypothetical rectangular room. The first reflection then adds 6 subs at various distances, and SPL decreases as the inverse of the distance. Double reflections will add more subs at greater distances, etc. The sum of all possible reflections (which are infinite), weighted down by the path distances and any reflection loss, is the level provided by the sub inside the room.

So right there we see that room size has an impact, as the "images" will be further apart in a larger room. However, one would expect the effect to be proportional to the inverse of the average room length (i.e. cube root of the room volume). So perhaps the ULF score should be cubic root of room volume / SI equivalent. I think it just doesn't matter too much, because most rooms are 7 to 9 ft high anyway (i.e. not much variations in height), and overall in a rather small range of volume that is mainly affected by the length of the average dimension. Also, the focus is more on the number of stars than the actual ULF score. The root cube of the volume would not change much -- just the limits of the bins for the various stars.
dominguez1's Avatar dominguez1
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Guys...

 

Absolutely love the discussion! I was hoping for these types of challenges earlier on, but glad that now that it's starting to become more AVS mainstream, these discussions are happening. Love it, and appreciate the thoughtful insight. :)

 

Quote:

Originally Posted by neutro View Post

I have a few comments about the score by the way. I totally understand that the score is not perfect and is only a quick figure that help us compare setups.

The main question I have is that the score is normalized by room volume. It's intuitive that the same gear in a smaller room will result in more SPL. But is the effect directly proportional to volume? I.e. is the same setup placed in a room half the volume automatically twice louder (i.e. +6 dB)? I understand specifics like materials, furniture and room shape can also affect levels at the main listening position, so let's assume an empty rectangular room.

The part about normalizing to a popular sub (the sealed SI) is a good idea too, yet it's still a bit abstract as I'm pretty sure the majority of us here have never seen nor heard that idealized sub. So while it gives us an idea (wow, didn't now that it would take 3 sealed SI's to hit the 16 Hz level I get with my two ported 12"), the score could also be expressed as cu. ft. per max burst dB SPL at a given frequency. Or, if we want a score that goes *up* when it's better, simply the inverse, i.e. max burst dB SPL (or equivalent SI's) per cu ft. Anyway, the stars is the final score and those can be computed in cu. ft. per equivalent SI, or in max burst dB SPL per cu. ft. ... the conversion is direct anyway.

Also there is no reason to limit this to the ULF portion, unless perhaps the room size has much less importance for mid-bass and there would be no reason to normalize room size?

Great point Neutro, and you're right. I could have done just volume per max burst. The reason why I decided to use SI, was what you've already eluded to above: Physical 18in drivers where we have pictures, people own them, etc. are much more 'relatable' and intuitive compared to decibels. When comparing from room to room, I feel we can better relate to physical objects than sound pressure levels. It's much more meaningful and comparable to the average joe that in his 1000cf room he has 1 18in sub compared to the same 18in sub in a 3000cf room. That intuitively makes more sense that saying his sub in a 1000cf room can reach 89.2db compared to that same sub in a 3000cf room can reach 89.2db.

 

Either metric could have been used, I just felt converting it to a sub would help visualize things better, and ultimately easier to understand.

 

As for using the SI? Not going to lie...the acronym really worked with its brevity. :cool: Additionally though, it is popular and some of the most well know HT systems use them. So, by using the SI as the baseline, again folks could ultimately compare to those uber AVS HT systems (yes, I'm talking about you pop). The point is, it doesn't matter what sub is used to convert to because all it is doing is setting a frame of reference or baseline to compare with others.

 

Quote:
Originally Posted by ironhead1230 View Post


I was just working on posting something very similar. This thread is being referenced a lot now and some are using the scores and output estimates as absolutes. Comparing subs down to the db. Until now, there has really been no testing to see if these methods are valid and if room volume alone makes as large an impact as reflected in the ratings. I think its time we attempt to verify these scores using speclab captures. We could try and pick a clip or two that highlight the different frequency scores and see what people's setups actually do during playback. I started a thread awhile ago to try and put a procedure together to take mic'd speclab captures, but nobody else seemed very interested. I recently found my first attempts with speclab from the PA sub GTG last year. Looking through them again, I think it is worthwhile to revisit.

I definitely think it's worth a revisit! I too want to verify these scores...

 

Quote:
Originally Posted by neutro View Post

Ultimately the score can be replaced by max sweep frequency measurements at your listening position. Only then will you have the whole story, and if you already have the gear to take accurate speclab measurements, then I guess you can also load REW and perform max output sweeps.

However, there are drawbacks to that. First, it's pretty involved, and close-to-max output FR measurements at the MLP are most often already posted by the guys with the 5-star setups smile.gif It's pretty far from the quick back of the envelope type estimate that the score provides. Second, some people (me included) can't really do a max sweep. Third, if the goal is to condense your setup in a single metric, you still have to convert the FR into a score / stars. Fourth, the most interesting / funny part of the ULF score cannot be achieved by measurements: it's the what-if! What if I had four JTR Captivators in my 1680 cu ft room? biggrin.gif That spreadsheet gives us a quick glance at what can be achieved for us who are contemplating an upgrade. (Disclaimer: no I'm not.)

Still, I totally agree with you about at least verifying the effect of room volume. It is the major driver in the current ULF score. What if SPL varies with the square root of room volume instead? That changes everything. I for one would love experimental confirmation but I'd settle for a theoretical argument from acoustics and physics.

It's just that subwoofer don't act like pistons. I agree that for a given piston displacement, in a static situation, half the room volume will yield double the pressure level induced by the piston displacement inside the room. But our rooms are not perfectly sealed, and the sub's piston displacement is actually negligible compared to the total room volume, as evidenced by the fact that all our subs have pretty poor performances at 0 Hz. (Unlike rotary subwoofers by the way... biggrin.gif) So pressure level achieved by our subs is a dynamic phenomenon and linked to the acoustical energy pumped by the driver. How that is affected by room volume is not straightforward for me.

Yes, that is the challenge. We need some test subjects in each star category...folks that are willing to take some max sweeps and ensuring we all follow a repeatable process to limit variation. Again, not an easy ask IMO...I am personally hesitant to run a max sweep because I don't know REW, and I don't want to blow up my subs...

 

 

Quote:
Originally Posted by neutro View Post

Of course the room has a tremendous importance. We are just arguing about the specifics. I don't know enough about acoustics to have a clear idea. As I see it, there are two factors in play. The first is distance: sound pressure drops as the inverse of the distance. If you're twice farther, SPL drops by half (-6 dB). But that's not all, since if that were the case, the distance to MLP would be the main driver. The other factor is reflections on the wall, ceiling and floor surfaces which has a reinforcing effect. This is complicated by the resonances and room modes a bit, but if a wall is farther, then the reflection will also come from further. Perhaps this is the basis for the volume normalization.

Then again, you could have a room of infinite volume (e.g. parking lot) and still have some great ULF, whereas this ULF score would simply be infinite cu. ft per SI equivalent (0 star). This is just to show how things break down if you push the idea to the limit, while still acknowledging that this is not an interesting case (unless you have an outdoor home theater I guess). On the other side, if the volume is sufficiently small, you could get a very large ULF score. Get in a 200 cu. ft. closet with an SB12 and there you go, 4.5-star setup. I wonder if that would really give me reference levels @ 12.5 Hz? Again, this is not a very interesting scenario, so the direct proportionality with volume might still be warranted for most home theater rooms.

Another great point...certainly outlier situations in practice, but I do realize your point was illustrative. The Star rating should ideally be bell shaped curves and HT systems would fit within certain standard deviations....meaning if your score lands with a given star range, we should have some confidence level that you're in a certain SPL range.

 

Quote:
Originally Posted by neutro View Post

Well if we neglect standing waves (room modes) for now, the effect of boundaries in a room is to reflect sound waves. As such, if the reflection is perfect (no absorption), then it is as if there were mirror images of your sub in imaginary rooms on each side (and up and down) of an hypothetical rectangular room. The first reflection then adds 6 subs at various distances, and SPL decreases as the inverse of the distance. Double reflections will add more subs at greater distances, etc. The sum of all possible reflections (which are infinite), weighted down by the path distances and any reflection loss, is the level provided by the sub inside the room.

So right there we see that room size has an impact, as the "images" will be further apart in a larger room. However, one would expect the effect to be proportional to the inverse of the average room length (i.e. cube root of the room volume). So perhaps the ULF score should be cubic root of room volume / SI equivalent. I think it just doesn't matter too much, because most rooms are 7 to 9 ft high anyway (i.e. not much variations in height), and overall in a rather small range of volume that is mainly affected by the length of the average dimension. Also, the focus is more on the number of stars than the actual ULF score. The root cube of the volume would not change much -- just the limits of the bins for the various stars.

IMO, this is what we need to hash out more.

 

The score itself is factual. It is

  • room size / SI

That is a metric, and it can be compared with others. It's the interpretation and categorization where we need to hone in on.

 

 

The above chart is what we need to figure out and potentially change. IMO, the ULF scores can stay the same. What should be the ranges and how does that relate to reference output?

 

The output estimate started based some very good data that Bosso posted here. He basically stated that in his experience, the recipe for reference output was a sealed design where you would have .01 Liters of displacement per cubic foot. So for 2000 cubic feet, you would need 20 liters of displacement. 4 SI is equal to 21.2 liters of displacement. 2000cf / 4 SI = 500 ULF score....around the middle of the range. I created the categories before relating his post, so it confirmed I was in the general ballpark.

 

If we can keep the score the way it is, it will keep it simple (the goal of this metric). I think we can just put more science around the above chart to determine how close it is, and what needs to change.


dominguez1's Avatar dominguez1
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To be honest, looking at the chart more...I do think it's pretty close. Building off of Bosso's findings and relating that to the ULF score: 500 would get you reference level at the lowest frequencies, but in this case 10hz. In my 1900cf room, with just my dual FTW21s, my score is 424 or so. I've got some video of the Hulk end sequence where I recorded the scene with Omnimic, and I was getting reference level output to 5hz according to OM.

 

If I can get reference at 10hz, then I can certainly get it at 12.5hz. At 16hz and 20hz, I should be able to get above reference. This makes sense; look at all the max spl sweeps on data-bass. 16hz and 20hz output is more that 10 and 12hz. This was how the output estimate was formed for 4.5 star.

 

If 4.5 star is Reference, than 5 star is certainly Above Reference at all frequencies.

 

So, 5 star and 4.5 star seem to make sense to me. Perhaps, 4 star and 3.5 star need to be evaluated more? If you look at the member scores, reference at 16 and 20hz or so seem likely. Basshead is a good example, and he has done max sweeps.


BeeMan458's Avatar BeeMan458
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My question revolves around the FV15HP which is tuned to 12Hz. With two of them in our 3300^3 room, we have a score of 868, yet your chart only gives it reference capability at 16Hz. confused.gif

In the case of the FV15HP, I would expect it to obtain reference to it's tuning point (one vent plugged) of 12Hz. What am I missing?

(if you've responded to this question prior, forgive my asking again)
Lecter83's Avatar Lecter83
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Quote:
Originally Posted by neutro View Post

I don't remember where I've seen it, but this is what I remember. However I'm far from certain that it's 1.5 dB down from the PBs at all frequencies. I think they are "within 1.5 dB of the PBs". I'll try to find a reputable source for this. This is due to the cylinder having a tad smaller volume than the equivalent box if I remember correctly.

Actually the difference is only 1.5 db in the lowest range, 15Hz - 25Hz if I remember correctly.
At other frequencies, the gap is reduced and are practically similar.

This is all more measurable, I fear that it is not audible.
Reddig's Avatar Reddig
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Be nice to have some volunteers in category 4 and up to do compressions sweeps to see how well they r playing reference. If compressing like crazy at reference is it really reference? Just a thought smile.gif
dominguez1's Avatar dominguez1
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Quote:
Originally Posted by BeeMan458 View Post

My question revolves around the FV15HP which is tuned to 12Hz. With two of them in our 3300^3 room, we have a score of 868, yet your chart only gives it reference capability at 16Hz. confused.gif

In the case of the FV15HP, I would expect it to obtain reference to it's tuning point (one vent plugged) of 12Hz. What am I missing?

(if you've responded to this question prior, forgive my asking again)
From databass, at 12.5hz the fv is 98.5. At 16hz it is 104db. This is about 6db difference. This is the reason why...as you go deeper in frequency, the less output you have. However, from an SI perspective, it may be the same conversion factor...that is only confirming that the SI also follows the downward trend in output.
BeeMan458's Avatar BeeMan458
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Quote:
Originally Posted by dominguez1 View Post

From databass, at 12.5hz the fv is 98.5. At 16hz it is 104db. This is about 6db difference. This is the reason why...as you go deeper in frequency, the less output you have. However, from an SI perspective, it may be the same conversion factor...that is only confirming that the SI also follows the downward trend in output.

Thanks!

I sure hope I don't have to add a third FV15HP to the mix but I am keeping my options open. In my mind, I'm committed to the concept of three FV15HPs and out but if I find bliss with two, the additional monies will find themselves spent on an AVR upgrade.

Crap, the Saints won.....tongue.gif
neutro's Avatar neutro
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Quote:
Originally Posted by dominguez1 View Post

I think we can just put more science around the above chart to determine how close it is, and what needs to change.

Well apart from limit cases (outside, or in a closet!), it's certainly holding its own. My own case illustrate a bizarre side-effect of the current rankings though. My subs are 16-Hz tuned so I get above reference at 16 and 20 Hz with 4.5 stars. However below tuning the output drops really fast, so I'm down to 3.5 stars at 12.5 Hz. So since I'm not reaching reference at 12.5 Hz, it can't be a globally 4.5-stars setup. So we put in in the 4-star category?

Another point is what constitutes reference level. Is it 115 dB SPL for each frequency? If so, it's worth noting that 115 dB SPL sounds much louder (but is way easier to achieve) at 20 Hz than 10 Hz.
Quote:
Originally Posted by BeeMan458 View Post

My question revolves around the FV15HP which is tuned to 12Hz. With two of them in our 3300^3 room, we have a score of 868, yet your chart only gives it reference capability at 16Hz. confused.gif

In the case of the FV15HP, I would expect it to obtain reference to it's tuning point (one vent plugged) of 12Hz. What am I missing?

I think the lower the tune, the more spread out is the port resonance, and the sub behaves more and more like a sealed sub. If you look at the FV15-HP graphs on data-bass, you'll see the overall FR is very smooth with a shallow roll-off. The tune is much less spiky than, say, with an SVS sub (even with 2 ports open). So even at the tuning point, you have a large drop compared to 20 Hz. Yet, the overall curve is pretty close to the SVS PB13-Ultra in 15 Hz tune.
Quote:
Originally Posted by Lecter83 View Post

Actually the difference is only 1.5 db in the lowest range, 15Hz - 25Hz if I remember correctly.

Well these are the frequencies of interest in this exercise anyway.
Quote:
This is all more measurable, I fear that it is not audible.

Indeed -- adjusting for 1.5 dB under the PB12-Plus, the categories don't change.

It would still be interesting to find a definitive source for the 1.5 dB figure however.
Quote:
Originally Posted by Reddig View Post

Be nice to have some volunteers in category 4 and up to do compressions sweeps to see how well they r playing reference. If compressing like crazy at reference is it really reference? Just a thought smile.gif

Haven't done max sweeps, nor reference-level sweeps. However I tested a few demos at reference level, including the infamous Pulse Server Room scene that got heavy 15 Hz content, and the Super Lycan scene from Underworld: Awakening, and apart from rattles everywhere in the room for the first, I didn't notice anything wrong (no port chuffing, no obvious distortion). Of course a measurement would show compression more readily but at first sight, it seems that I'm indeed able to go reference level with 15 Hz content without problem.
BeeMan458's Avatar BeeMan458
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Quote:
Originally Posted by neutro View Post

I think the lower the tune, the more spread out is the port resonance, and the sub behaves more and more like a sealed sub. If you look at the FV15-HP graphs on data-bass, you'll see the overall FR is very smooth with a shallow roll-off.

Thanks! Good catch as I have been looking solely at the one port open graphs and have not paid attention to the graphs representing two ports open. Wow, 9dB, that's a "HUGE" difference in output and yes, it does look more like a sealed subwoofer's output graph than ported. With in room gain, the one port open graph will come up a bunch more. With room gain and the addition of a second FV15HP, I would expect the left end to come up +12dB. Not quite reference but 110dB @ 12.5Hz, that's not too shabby.

(am I being overly optimistic?)
Brian Fineberg's Avatar Brian Fineberg
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neutro, did you measure those movies with REW?
neutro's Avatar neutro
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post #654 of 2755
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Quote:
Originally Posted by BeeMan458 View Post

With room gain and the addition of a second FV15HP, I would expect the left end to come up +12dB.

(am I being overly optimistic?)

Who knows. You can count on +4-5 dB from duals, that's for sure (+6 dB if you co-locate them but that's probably not your goal in the first place going with duals). So that would mean you expect +7-8 dB of room gain at 12.5 Hz. I have no idea if this is realistic or not, but it does seem a bit high at first sight.

That being said, the FV15HP looks like a terrific sub for the price even if you don't hit reference at 12.5 Hz. This thread is about ULF, but the FV15HP seem to provide tons of mid-bass slam as well.
Quote:
Originally Posted by Brian Fineberg View Post

neutro, did you measure those movies with REW?

Nope, sorry. The goal was to verify that I had no driver distress with dual Plus playing at reference. There was a member who had badly behaving Plus drivers playing the same content at lower volume, so I wanted to make sure this was indeed not the norm. Turns out his two subs were out of phase and cancelling each other.

In my room, I think the dual Pluses are barely breaking a sweat playing U:A at reference. I've seen videos where 12" drivers were pushed much harder than mine (although admittedly it's a bit hard to see the drivers on down-firing subs). The video I made is here but it's pretty boring.
BeeMan458's Avatar BeeMan458
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Quote:
Originally Posted by neutro View Post

Who knows. You can count on +4-5 dB from duals, that's for sure (+6 dB if you co-locate them but that's probably not your goal in the first place going with duals). So that would mean you expect +7-8 dB of room gain at 12.5 Hz. I have no idea if this is realistic or not, but it does seem a bit high at first sight.

Greed and envy are sins. Greed and envy are motivating forces. Can I go for being a motivated sinner? tongue.gif
neutro's Avatar neutro
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Quote:
Originally Posted by BeeMan458 View Post

Greed and envy are sins. Greed and envy are motivating forces. Can I go for being a motivated sinner? tongue.gif

The way I see it is that for a standard living room, circa $2500 (lower if you go DIY) will buy you solid reference level down to 16 Hz. This is what you get with dual FV15HP. You also get non-negligible output below, just not reference.

To go reference level at 12.5 Hz (i.e. 4.5-star ULF setup), due to the physics in play and the diminishing return effect, you have to up your game significantly.

In my 1680 cu ft room, according to the calculator spreadsheet, like you, two FV15HP provides me with a 4-star setup (i.e. above reference down to 16 Hz). To hit reference at 12.5 Hz, a third FV15-HP won't even cut it. I have to add a fourth. (If I use my SVS Plus subs, I'd have to go with 5, lol). So to go from a 4-star setup to a 4.5-star setup, I'd have to double (or more) the investment (not to mention try to fit that much subs in a small room). Thus the dedication level to get a 4.5-star setup is not the same at all.

With commercial subs, it would indeed take me about $5000 to reach 4.5-star: e.g. 4 x FV15HP, 4 x PSA XS30, 2 x Submersive HP, etc. (Interestingly if the numbers are right, I see that a single JTR Captivator S2 or PSA Triax would get me there, making those the least expensive ways for me to achieve 4.5-star. Here's why that calculator is so useful!)
BeeMan458's Avatar BeeMan458
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Quote:
Originally Posted by neutro View Post

To hit reference at 12.5 Hz, a third FV15-HP won't even cut it. I have to add a fourth. (If I use my SVS Plus subs, I'd have to go with 5, lol). So to go from a 4-star setup to a 4.5-star setup, I'd have to double (or more) the investment (not to mention try to fit that much subs in a small room). Thus the dedication level to get a 4.5-star setup is not the same at all.

I can say this from the start, the WAF will not allow for a fourth subwoofer. frown.gif

Quote:
I see that a single JTR Captivator S2 or PSA Triax would get me there, making those the least expensive ways for me to achieve 4.5-star. Here's why that calculator is so useful!)

I was under the impression that a single Triax was 2.4 SI. In our room (3300^3), three FV15HPs would happily give us 5.7 SI or a score of 579. This would give us a 4.5 star subwoofer system or reference to 12.5Hz. I do have to say, in my opinion, the FV15HP, easily hits all the check points.

(based on what you posted above, what am I missing?)
neutro's Avatar neutro
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Quote:
Originally Posted by BeeMan458 View Post

(based on what you posted above, what am I missing?)

I have no idea. I think I entered the wrong sub (perhaps the 2-port line instead of 1-port). 2 FV15HP indeed provides me with a 4.5-star system.

Incidentally, I hesitated a lot between the Plus and the FV15HP. But importing the Rhytmik subs to Canada is a PITA and adds hundreds to the bill. In retrospect, I just don't know where I'd have put them either as the cylinders barely fit biggrin.gif
BeeMan458's Avatar BeeMan458
10:27 AM Liked: 801
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11-22-2013 | Posts: 8,374
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Quote:
Originally Posted by neutro View Post

But importing the Rhytmik subs to Canada is a PITA and adds hundreds to the bill. In retrospect, I just don't know where I'd have put them either as the cylinders barely fit biggrin.gif

I hate intrinsic details. tongue.gif
ahmedreda's Avatar ahmedreda
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In your space (1680 cu ft), if you use 2 of the FV15HP in 1 port mode, you would get 4.5 stars starting at 12.5hz and up unless I am missing something.
Quote:
Originally Posted by neutro View Post

The way I see it is that for a standard living room, circa $2500 (lower if you go DIY) will buy you solid reference level down to 16 Hz. This is what you get with dual FV15HP. You also get non-negligible output below, just not reference.

To go reference level at 12.5 Hz (i.e. 4.5-star ULF setup), due to the physics in play and the diminishing return effect, you have to up your game significantly.

In my 1680 cu ft room, according to the calculator spreadsheet, like you, two FV15HP provides me with a 4-star setup (i.e. above reference down to 16 Hz). To hit reference at 12.5 Hz, a third FV15-HP won't even cut it. I have to add a fourth. (If I use my SVS Plus subs, I'd have to go with 5, lol). So to go from a 4-star setup to a 4.5-star setup, I'd have to double (or more) the investment (not to mention try to fit that much subs in a small room). Thus the dedication level to get a 4.5-star setup is not the same at all.

With commercial subs, it would indeed take me about $5000 to reach 4.5-star: e.g. 4 x FV15HP, 4 x PSA XS30, 2 x Submersive HP, etc. (Interestingly if the numbers are right, I see that a single JTR Captivator S2 or PSA Triax would get me there, making those the least expensive ways for me to achieve 4.5-star. Here's why that calculator is so useful!)

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