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post #1621 of 1629 Old Yesterday, 07:02 PM - Thread Starter
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Originally Posted by Mfusick View Post
How much max depth do you have to work with? (JPA)

If you build 4 Gjallerhorns you might not end up needing smoothing subs. You certainly would NOT need more bass One Ghorn alone already has more output than 4 sealed UXL18's at 16hz. Multiple subs in different locations have a way of smoothing themselves too.

If you could fit them the infinity 1260 would make a really nice smoothing sub. $60 each. Good quality with harman technologies. They are almost a proper bass solution unto themselves. You don't need much low or ULF output for smoothing subs, most of the trouble is between 30hz-90hz. You have a big room too.
I could probably swing 16" for the column depth if I had to. I'm actually considering some mid-build changes that may give me a little more flexibility in column depth.

WIth regard to the subs, my issue is going to be room modes. It looks like both rows of seating fall in a null at 38 Hz and 76 Hz. No amount of extra output will fix that. So I'm looking at adding smoothing subs to help eliminate modes, not increase output. The question I have is, if my horn subs are giving me 115 dB at the LP, but I have a 9 db null at 38 Hz, does the smoothing sub have to be able to output 115 dB to smooth out the response. I'm guessing it does not, but I can't think of why the physics would support that.

Another option I have, recommended by Toole, is a single sub at the front wall midpoint and another at the rear wall midpoint. This is supposedly an optimal configuration for a rectangular room with the seats within a 6' square at the middle of the room.

Dude, are you made of leprechauns? Cause that was awesome!

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post #1622 of 1629 Old Today, 06:52 AM
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Is the change you're considering in treatment depth? I think 6" for treatments would be pretty close to ideal. Then a 16" deep column would stand out 10" and look right. Of course, there's no rule about that - the column could end up flush with the treatment and still look very good, IMO.

Regarding the output from smoothing subs: I have a few thoughts here, which might be half-baked, so prepare a few grains of salt. In a room with perfect walls (zero transmission - perfect reflection) the null from a single driver located at a room boundary would be a perfect notch, where SPL goes to zero at one line across the room. If an additional sub is at the opposite wall, the measured SPL at that location should be equal to every other position ( I think, but again, this might be half baked), assuming the subs are identical. If the second sub were good for half the output of the first, I think the notch should be reduced to being only -3dB - so that's pretty good. Obviously a theoretical perfect room doesn't exist, so expect some smearing in space, time, and frequency. (Speaking of that, can you put a small sub in there and check out your modal response as is? There's lots to learn at this stage, with the basic shell complete.)

I just don't see why anything other than identical subs should be considered, when flexibility, phase, and output are all taken into account. I'm sure I haven't supported that statement enough to be persuasive, but there you have it: I favor symmetry in all aspects of subwoofer system design. Maybe that's naive or ill-informed, but that's what I'm doing - but sealed, which I think will be a lot more forgiving that horns.
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post #1623 of 1629 Old Today, 07:34 AM
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Originally Posted by HopefulFred View Post
Is the change you're considering in treatment depth? I think 6" for treatments would be pretty close to ideal. Then a 16" deep column would stand out 10" and look right. Of course, there's no rule about that - the column could end up flush with the treatment and still look very good, IMO.

Regarding the output from smoothing subs: I have a few thoughts here, which might be half-baked, so prepare a few grains of salt. In a room with perfect walls (zero transmission - perfect reflection) the null from a single driver located at a room boundary would be a perfect notch, where SPL goes to zero at one line across the room. If an additional sub is at the opposite wall, the measured SPL at that location should be equal to every other position ( I think, but again, this might be half baked), assuming the subs are identical. If the second sub were good for half the output of the first, I think the notch should be reduced to being only -3dB - so that's pretty good. Obviously a theoretical perfect room doesn't exist, so expect some smearing in space, time, and frequency. (Speaking of that, can you put a small sub in there and check out your modal response as is? There's lots to learn at this stage, with the basic shell complete.)

I just don't see why anything other than identical subs should be considered, when flexibility, phase, and output are all taken into account. I'm sure I haven't supported that statement enough to be persuasive, but there you have it: I favor symmetry in all aspects of subwoofer system design. Maybe that's naive or ill-informed, but that's what I'm doing - but sealed, which I think will be a lot more forgiving that horns.
Half baked thoughts? No!

A sub systems limiting factor is the weakest link........ie. the lesser capable drivers limits system's overall ability. Had this fact given to me by an expert from Triad.

So I dropped leveling subs in columns which were designed in my system......and went to 4 identical drivers. Level and gain matching was easy! I do suppose in the hands of an expert with appropriate equipment anything is possible.
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post #1624 of 1629 Old Today, 07:42 AM
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Are you looking for the column to be the same depth for it's full height? If not, you could have a deeper column base up to your chair rail height for the smoothing sub and then keep a thinner upper column.
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post #1625 of 1629 Old Today, 09:15 AM
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Originally Posted by TMcG View Post
Are you looking for the column to be the same depth for it's full height? If not, you could have a deeper column base up to your chair rail height for the smoothing sub and then keep a thinner upper column.

This is a good idea. If you needed a little extra depth this could work and look good.


Quote:
Originally Posted by HopefulFred View Post
Is the change you're considering in treatment depth? I think 6" for treatments would be pretty close to ideal. Then a 16" deep column would stand out 10" and look right. Of course, there's no rule about that - the column could end up flush with the treatment and still look very good, IMO.

Regarding the output from smoothing subs: I have a few thoughts here, which might be half-baked, so prepare a few grains of salt. In a room with perfect walls (zero transmission - perfect reflection) the null from a single driver located at a room boundary would be a perfect notch, where SPL goes to zero at one line across the room. If an additional sub is at the opposite wall, the measured SPL at that location should be equal to every other position ( I think, but again, this might be half baked), assuming the subs are identical. If the second sub were good for half the output of the first, I think the notch should be reduced to being only -3dB - so that's pretty good. Obviously a theoretical perfect room doesn't exist, so expect some smearing in space, time, and frequency. (Speaking of that, can you put a small sub in there and check out your modal response as is? There's lots to learn at this stage, with the basic shell complete.)

I just don't see why anything other than identical subs should be considered, when flexibility, phase, and output are all taken into account. I'm sure I haven't supported that statement enough to be persuasive, but there you have it: I favor symmetry in all aspects of subwoofer system design. Maybe that's naive or ill-informed, but that's what I'm doing - but sealed, which I think will be a lot more forgiving that horns.

A local friend of mine I know in real life is HAA, ISF, Cedia, THX, ..etc.. Certified and has taken Dennis Classes and also traveled out to the THX ranch for some trainings; He explained this to me once: In an ideal scenario you'd actually have 4 subs, one in each corner, and two on the floor and two on the ceiling. This would produce the best result.

Placement of subs can fix a lot of issues, so can a properly designed room. Smoothing subs are a good tool to use for sure, but not a requirement. And with a properly designed bass horn you won't necessarily have better or worse response at the LP than a sealed sub. The only certain is you would have more bass and lower distortion within the design intentions assuming it was designed right. You'd also need a lot less watts to get that. I think around here there is a prevailing assumption that sealed is better simply because they are easy to calibrate, have good extension, easiest to build, and take the least amount of space. This is all true, and obviously has some serious benefits too. But, the one thing sealed isn't great at is output so while they are a great solution for a smaller space they become much worse solution for bigger spaces.

There is a reason why Metallica uses bass horns at their show and not sealed subs. There is a reason why most of the IMAX theaters have Danely bass horns installed in them. It's because in bigger spaces they work better, and in situation where you want good output they are the best choice. The problem with bass horns isn't that they are hard to calibrate really, it's more just the WAF factor they are big, and difficult and expensive to build and design. Ported subs are out of phase 180 degrees at port tune, sealed are not- and horns are 90 degrees out of phase. Mixing them can be a tad bit tricky but it's not impossible. There is a bunch of guys in the DIY section running mixes with good results validated with measurements and I have read a couple threads where even Dennis calibrated some sealed smoothing subs with some ported cabs and said the results were very good.

Room nodes and response are tough to really account for 100% in the design phase because just moving the sub off the wall or closer can change things, and it's not always as perfect as it seems in theory when you actually measure the room. Things can be different so really the best way is to plan the room the best you can according to theory and then measure the final results to calibrate. I'm not sure JPA would know the full importance of some of this stuff until he has subs in his room, but either way it's all fixable for a great result with any kind of sub and even a mix of them.

I think that an 80Hz null would occur if the radiating plane is 3.5 feet from the wall. With most subs that wouldn't be a problem. If a sub was so large that the baffle was that far away from the wall the simple cure is to aim it at the wall I think. More subs in more locations has a natural effect of smoothing response so probably the best solution is to have more than just one subwoofer and to locate the subwoofers properly. If you can get some subs on the side of the room and back of the room that will do a great job at evening out the response. The way subwoofers interact with a room are usually dependent on their placement in the room, and moving them or placing them in a different spot can get a different result. But having a bunch in different spots has a way of averaging out things. JPA can you do a sub in the back to counteract the sub in the front ? That's a great option for you. It won't necessarily alleviate your need to calibrate but my guess is it would minimize it and have a positive effect at your bass response at LP.

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post #1626 of 1629 Old Today, 09:33 AM
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Originally Posted by doublewing11 View Post
Half baked thoughts? No!

A sub systems limiting factor is the weakest link........ie. the lesser capable drivers limits system's overall ability. Had this fact given to me by an expert from Triad.

So I dropped leveling subs in columns which were designed in my system......and went to 4 identical drivers. Level and gain matching was easy! I do suppose in the hands of an expert with appropriate equipment anything is possible.
I don't think so. Shawn Byrne explained to me in a PM:

" You don't need to go that low in frequency for the balancing sub. It isn't necessary due to the nature of the modal fundamental frequency in the room. Your problems don't begin till you hit those frequencies which are usually around 30 Hz or above, which is why bass thumping subs are not needed for a balancing sub. "

This was within what I was already told by others too, and so I trust his advice.

It's not about being the "weakest link" for a smoothing sub, it's just about providing enough balance for a smooth response and being properly integrated. Triad is good stuff and certainly using good stuff helps make things easier, but I think any modest but decent quality sub woofer has the ability to be a smoothing sub. It doesn't have to be an ULF thumber or keep up with your main bass solution.

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post #1627 of 1629 Old Today, 10:16 AM
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Quote:
Originally Posted by Mfusick View Post
It's not about being the "weakest link" for a smoothing sub, it's just about providing enough balance for a smooth response and being properly integrated. Triad is good stuff and certainly using good stuff helps make things easier, but I think any modest but decent quality sub woofer has the ability to be a smoothing sub. It doesn't have to be an ULF thumber or keep up with your main bass solution.
I hope you are correct. I am planning two 15" ported subs up front, and 3 10" sealed balancing subs in the columns around the room. We shall see--stay tuned.
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post #1628 of 1629 Old Today, 10:20 AM
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I hope you are correct. I am planning two 15" ported subs up front, and 3 10" sealed balancing subs in the columns around the room. We shall see--stay tuned.
Are you porting the 10" at the same tune as the 15"? That's probably smart to keep it simple.

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post #1629 of 1629 Old Today, 10:25 AM
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Actually, the 10" subs will sealed Procella P10si (smaller, so they'll fit in the columns). The ported 15" subs are JBL Project Array 1500 which I already have, and am very happy with.
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