Room Gain
I don't have room gain measurment experience, but I have been reading many posts by acoustical engineers. In a normal situation for most homes and audio rooms, there is a 2x4 wall with 1/2 inch drywall and the room gain is minimal as the wall is very lossy to bass. If you move up to a 2x6 inch wall with double 5/8 inch drywall, you will have increased room gain. Room gain is much higher when you are talking about a basement with 8 inch (or thicker) concrete walls with tons of dirt on the other side.
Acoustical engineers will also say that those with concrete walls, while they will will have the most room gain, they will also have the worst bass frequency response because the room modes are terrible when the bass has "nowhere to go." The frequency response in the bass region is much easier to deal with when you have 2x4 walls and only 1/2 inch drywall, although less efficient because of little room gain...
Retsel
I don't have room gain measurment experience, but I have been reading many posts by acoustical engineers. In a normal situation for most homes and audio rooms, there is a 2x4 wall with 1/2 inch drywall and the room gain is minimal as the wall is very lossy to bass. If you move up to a 2x6 inch wall with double 5/8 inch drywall, you will have increased room gain. Room gain is much higher when you are talking about a basement with 8 inch (or thicker) concrete walls with tons of dirt on the other side.
Acoustical engineers will also say that those with concrete walls, while they will will have the most room gain, they will also have the worst bass frequency response because the room modes are terrible when the bass has "nowhere to go." The frequency response in the bass region is much easier to deal with when you have 2x4 walls and only 1/2 inch drywall, although less efficient because of little room gain...
Retsel
Well, I guess that wraps it up. Once again.
In any room made of concrete, having no doors or windows, and using ONLY sealed speakers*, the SPL pressurization effect (AKA room gain) is possible but the boost is small enough and low enough, and below what any speaker can usefully trigger to be deemed mythical.
Seems simpler to tweak your EQ a tiny amount below 5 Hz than to build your room with concrete walls on 6 sides.
And sounder just to work with principles room acoustics to support the bass rather than place vain hope for SPL pressurization.
Back to the thread: I suppose it is a whole lot easier to "design"* a sealed box for multiple small drivers (which is what I did) rather than the more complex estimations needed for other housings. Conversely, going with one large driver gives scope for more different kinds of housing both as a design exercise and when it comes to carpentry.
Ben
*Too bad for those with bass reflex, tuned duct, or TH subs. But many horns have drivers in sealed rear boxes, such as the Klipsch.
** I don't really believe that sealed boxes are designed since they have self-evident trade-offs. And all you are doing is picking your favoured trade-off.
In any room made of concrete, having no doors or windows, and using ONLY sealed speakers*, the SPL pressurization effect (AKA room gain) is possible but the boost is small enough and low enough, and below what any speaker can usefully trigger to be deemed mythical.
Seems simpler to tweak your EQ a tiny amount below 5 Hz than to build your room with concrete walls on 6 sides.
And sounder just to work with principles room acoustics to support the bass rather than place vain hope for SPL pressurization.
Back to the thread: I suppose it is a whole lot easier to "design"* a sealed box for multiple small drivers (which is what I did) rather than the more complex estimations needed for other housings. Conversely, going with one large driver gives scope for more different kinds of housing both as a design exercise and when it comes to carpentry.
Ben
*Too bad for those with bass reflex, tuned duct, or TH subs. But many horns have drivers in sealed rear boxes, such as the Klipsch.
** I don't really believe that sealed boxes are designed since they have self-evident trade-offs. And all you are doing is picking your favoured trade-off.
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Room Gain
I think that many people have their audio systems in their basements which do have concrete walls, although the ceiling, which is the floor of the rooms above, would be lossy (to the chagrin of those living upstairs of basement systems).
Also, a concrete structure doesn't just keep bass in, it keeps bass out. So if you want a truly quiet audio room, particularly to the bass frequencies, then you really need a bunker (and some who design their audio rooms from scratch take such an approach). However, you are more likely to have a ragged frequency response when your audio system is in a bunker - this is when multiple subwoofers are REALLY important.
It is interesting what Earl Geddes said, I've visited his house and his system is in the basement, so he should have significant room gain. Of course, he has a couple of feet of absorber material at the front of the room so maybe it acts as a huge bass absorber.
Also, I don't think what you are saying about tapped horns and bass reflex boxes is right. These subwoofer systems are designed to delay the rear wave to reinforce the front wave, so they would also benefit from room gain if the room allowed it.
Retsel
I think that many people have their audio systems in their basements which do have concrete walls, although the ceiling, which is the floor of the rooms above, would be lossy (to the chagrin of those living upstairs of basement systems).
Also, a concrete structure doesn't just keep bass in, it keeps bass out. So if you want a truly quiet audio room, particularly to the bass frequencies, then you really need a bunker (and some who design their audio rooms from scratch take such an approach). However, you are more likely to have a ragged frequency response when your audio system is in a bunker - this is when multiple subwoofers are REALLY important.
It is interesting what Earl Geddes said, I've visited his house and his system is in the basement, so he should have significant room gain. Of course, he has a couple of feet of absorber material at the front of the room so maybe it acts as a huge bass absorber.
Also, I don't think what you are saying about tapped horns and bass reflex boxes is right. These subwoofer systems are designed to delay the rear wave to reinforce the front wave, so they would also benefit from room gain if the room allowed it.
Retsel
Thanks for one more clear post on this subject.
But when you "pressurize" (if such a thing were feasible), you can't be taking the wave front and back. Sounds like perpetual motion. Or can you?
Maybe box housing theory presumes playing into non-pressurized vessels since all kinds of parameters would change.
Ben
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Did you even look at the graphs and links posted? It's not a small amount of gain, it's very substantial. And the rooms are not hermetically sealed concrete bunkers. Even in 2x4 on drywall construction you can still have modest amounts of gain below the modal region.
If you think it's impossible to build pressure with a resonant box because there's a port hole in the box you clearly don't understand the most basic principles of acoustics and resonance. Especially after it was just explained how a room with an open door can provide pressure in a recent post.
Everything in this quoted post is wrong but I'm not going to pick it apart piece by piece.
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OK Ben, let's go through this again. Look at this picture...
There is the close mic of the sub in teal -the listening position mic'd in green and -the listening position mic'd with a window in the room open in pink.
Do you see how close mic (teal) rolls off down low and the in room listening position does not? That is room gain. Stop saying that it is mythical, it makes you sound insane.
If your theory was right and it's all pressure, you'd figure that opening a window would let that pressure out of the room therefore lowering the effect of room gain. The response with the window open is actually hotter at 6-7Hz and 25Hz. How do you explain this? What mistake have I made here if I am wrong?
Room gain is not also known as SPL pressurization effect. It's just plain room gain. There's no need for you to be so hard headed about this. If you want to claim that it is irrelevant or mythical or blame it on pressure alone, you should bring in some measurements that substantiate your viewpoint.
Attachments
Oh yeah, and we're talking about a stick-built n' drywalled room on the 2nd floor. Plenty lossy. That is where these measurements were taken.
" Stop saying that it is mythical, it makes you sound insane. "
If you do a time domain analysis you mayl find something different.
If you do a time domain analysis you mayl find something different.
multiple subs vs. single larger sub
I would like to share my experiences with you that might be of interest to the OP. I am no expert on math and testing equipment, but I have many years of hi-fi and live sound listening experience. please don't mock me for being unscientific.
in the case of Bag End subs, the ELF 10" and 12" sound the same as the ELF 18". The 2x12" AND 1X18" are very similar in output and sound the same.
All Bag End ELF subs sound nearly identical to me, and I love them for home use, and Pro PA use. both inside and outside the sound has a low end "presence" or "feel" of a system playing much louder than it is.
The Bag End ELF subs have a very distinct "touchy Feely" tactile feel at all listening volumes, I find very different than any other subs I have used. I find it very pleasing.
I believe the difference is the time delay caused by phase relationship from one frequency to another. for example: the 100hz part of the kick drum beat and the 20hz part of the same drum beat need to be in phase with each other in order to create a realistic tactile listening experience. The classic vented box with 180 degree phase shift at the tuned frequency can't do that.
I haven't seen anyone mention using several larger woofers vs one smaller woofer. I have to heard the Bag End 4x18" box next to the Danley tapped horn th-115 with a single 15" woofer. I own both systems in multiple.
For the most part, The Danley with one Tapped horn 15", could get as loud as the Bag End quad 18" and in a slightly smaller box ( same footprint, but 1 1/2' shorter) but didn't sound nearly as deep and touchy feely.
On the other hand, the Danley TH-115 was very "punchy" and is the preferred box for most live music. 4 th-115 danley boxes per side go a long way! (really rock)
I use 6 Quad ELF 18" sub cabinets (24x 18" drivers total, 300wt per driver max) for festival PA (approx. 2500-3000 audience) and I get a "home hi-fi" sound I've never heard with any other PA system.
in both cases the mid high is the EV x-array (new at rolling stones tour 1999). When I got the EV system, It had 8 boxes of EV 2x 18" 1000wt drivers, and I quickly replaced them with 6 boxes quad 18" Bag End.
Huge sound quality improvement below 100hz!
The point is :
1. several small woofers in the Bag ELF alignment with processor sound as good as a larger single driver in same Bag End system.
2. While the Bag End system definitely is trading efficiency for sound quality, the trade is a good one and the system works fine in a small room at home or small to medium concert live concert; with HI-FI sound quality.
3. While not a new system, everyone should get a chance to hear the Bag End ELF system for themselves before choosing a subwoofer for home or PA.
4. Many systems have merits and should be considered based on personal listening as much as measured data.
I would like to share my experiences with you that might be of interest to the OP. I am no expert on math and testing equipment, but I have many years of hi-fi and live sound listening experience. please don't mock me for being unscientific.
in the case of Bag End subs, the ELF 10" and 12" sound the same as the ELF 18". The 2x12" AND 1X18" are very similar in output and sound the same.
All Bag End ELF subs sound nearly identical to me, and I love them for home use, and Pro PA use. both inside and outside the sound has a low end "presence" or "feel" of a system playing much louder than it is.
The Bag End ELF subs have a very distinct "touchy Feely" tactile feel at all listening volumes, I find very different than any other subs I have used. I find it very pleasing.
I believe the difference is the time delay caused by phase relationship from one frequency to another. for example: the 100hz part of the kick drum beat and the 20hz part of the same drum beat need to be in phase with each other in order to create a realistic tactile listening experience. The classic vented box with 180 degree phase shift at the tuned frequency can't do that.
I haven't seen anyone mention using several larger woofers vs one smaller woofer. I have to heard the Bag End 4x18" box next to the Danley tapped horn th-115 with a single 15" woofer. I own both systems in multiple.
For the most part, The Danley with one Tapped horn 15", could get as loud as the Bag End quad 18" and in a slightly smaller box ( same footprint, but 1 1/2' shorter) but didn't sound nearly as deep and touchy feely.
On the other hand, the Danley TH-115 was very "punchy" and is the preferred box for most live music. 4 th-115 danley boxes per side go a long way! (really rock)
I use 6 Quad ELF 18" sub cabinets (24x 18" drivers total, 300wt per driver max) for festival PA (approx. 2500-3000 audience) and I get a "home hi-fi" sound I've never heard with any other PA system.
in both cases the mid high is the EV x-array (new at rolling stones tour 1999). When I got the EV system, It had 8 boxes of EV 2x 18" 1000wt drivers, and I quickly replaced them with 6 boxes quad 18" Bag End.
Huge sound quality improvement below 100hz!
The point is :
1. several small woofers in the Bag ELF alignment with processor sound as good as a larger single driver in same Bag End system.
2. While the Bag End system definitely is trading efficiency for sound quality, the trade is a good one and the system works fine in a small room at home or small to medium concert live concert; with HI-FI sound quality.
3. While not a new system, everyone should get a chance to hear the Bag End ELF system for themselves before choosing a subwoofer for home or PA.
4. Many systems have merits and should be considered based on personal listening as much as measured data.
Hi Douglight,
Thank you for sharing your experiences in Post #130. I happen to prefer sealed boxes over all others in the home environment.
You may want to note, that the output phase of the bass-reflex is app. 90° off @ resonance. It's around the lower resonance peak that you see 180°.
Regards,
Thank you for sharing your experiences in Post #130. I happen to prefer sealed boxes over all others in the home environment.
You may want to note, that the output phase of the bass-reflex is app. 90° off @ resonance. It's around the lower resonance peak that you see 180°.
Regards,
The proof is in the pudding. This is a fade from the digital information on a bluray disc to the mic'd listening position. Room gain in full effect below 20Hz. It is clear from this that you get usable gain in the lower octaves because of your in room response.
Looks like you have a nasty ~43 hz dip in there. I'm sorry for your loss 🙂. I wish i had 10 Hz extension but I like horns too much to do anything but a 60 cu. ft. horn and that's impossible for me to move.
I may "sound insane" but at least I have a basic grasp of elementary logic.
1. LOTS OF THINGS influence bass boost (and loss) in a room.
2. SPL pressurization (AKA "room gain") is trivial to non-existent in normal home rooms.
3. Hey, you can observe bass boost without insisting again and again and again that it was caused necessarily by SPL pressurization.
QED
Ben
1. LOTS OF THINGS influence bass boost (and loss) in a room.
2. SPL pressurization (AKA "room gain") is trivial to non-existent in normal home rooms.
3. Hey, you can observe bass boost without insisting again and again and again that it was caused necessarily by SPL pressurization.
QED
Ben
I don't really consider it pressurization, It's not just bass boost, it is predictable, and sloped 12 db/octave boost occurring based on the largest edge length of the room. You can continue to discount measurements all you want, but you won't be right.
-I would believe you if you would start paying attention to the measurement data.
Like what? And what is bass boost, a button on your 80's boombox?
Absolute rubbish. I've been showing you examples otherwise of room gain from normal rooms all week.
I am stating that the low end boost is from room gain. That's what we call it Ben: ROOOOOM... GAAAIIIINNNN. Say it with me... ROOOOOM... GAAAAIIINNN. When you take a sub from outside and put it in a ROOOM you get low end GAAAIIINNN.
ROOM GAIN.
Please list some of these "LOTS OF THINGS" that influence bass boost below the modal region in a room. If it's not pressure what is it? Magic? Wizards? A myth so widespread that it came to life?
What are we looking at in these measurement graphs? It's spl vs frequency. Spl is sound PRESSURE level. If there's no pressure there's no sound. If the line in the graph is above 0 db we are looking at pressure. Measure the same sub outside and then in a room and there will be gain at frequencies lower than the room's modal region. What is causing that?
"SPL pressurization" is a redunancy. SPL is pressure. How that for elementary logic? The room has more radiation resistance than outside free space. The pressure is somewhat confined in the room even if it's leaky and not perfectly sealed. This isn't rocket science.
I don't discount the measurements at all. I measure all I can with my calibrated Dayton mic and like it when others do so.
In fact, I agree with you completely. The boost is not due to SPL pressurization; it is likely due to room modes. I agree with you completely.
As has been pointed out by everybody knowledgeable in acoustics, SPL pressurization (AKA "room gain" to those individuals) is trivial or non-existent in ordinary homes. I believe you agree with that.
But why do you want to call the gain due to room modes, "room gain." Why not just call that "room modes" or "eigen schtuff", or something coherent and meaningful, just like the usage of the rest of us?
Ben
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This makes no sense.
Changing his story again. I thought it was bass boost.
No one agrees with this.
It is not room modes creating the lower octaves' boost to DC. That's why I don't call it room modes. I call it room gain because that is what it's known as.