Home Theater Forum and Systems banner

1 - 20 of 24 Posts

·
Registered
Joined
·
18 Posts
Discussion Starter #1 (Edited)
We met over at AVS years ago,
Now I'm building a couple LLTs. I read everything on it and around it and now I think I have information overload.:gah:
I want to build two 63 inch wide trapezoids side by side (attached end to end to each other total 126 inches) above my 65"DLP that will be in a built-in underneath the sub.. The top of the box will be up against the ceiling as will the back be against the back wall. Both ceiling {7'6"h} and wall are sheet rock on studs. The top of the box would be 30" deep and the wall height and bottom depth both 24". I'm looking for about a 6'' forward tilt of the 21" front baffle. I'm coming up with net 20.024 cu ft (567.016L) of volume. (I think the calculator [EVC] here is wrong as it only came up with 16.79) That close enough to work with your 650 liter rule? :hail: I wanted to use the Mach 5 18.2.2 drivers x 2 (1 each box) with the EP 2500 0r a QSC amp.. The 15 hz port slot I came up with is either 3.103 x 12.407 x 17.77 long or if I fold this one, 3.545 x 14.18 x 24.552 long. I can make a nice radius bent rectangle inside if If need to fold it.. I figure 1 1/2" round over port flare because I have the cutter.

I been thinking to space the box from the ceiling and wall by .025" and low expansion foam fill the gap for some isolation and damping.. "Great stuff" and a extension tube.

I suppose I could use 15 inch drivers but I want shock and awe :bigsmile: looking down on the masses seated in front of my silver shrine. There is more to this saga. The actual room dimension is 23ft x 21ft.x 7.5 ft ceiling, yielding 3622.5 cu ft of which the the TV and stuff is only in one half. (Left half) the long way. If you notice the 21/2= the 126 inches..The left wall is sheet rock on metal studs foam board insulated, but not isolated, over a 18" concrete foundation wall. Essentially I have a solid wall to my left and a infinite opening to my right as we seat. The back wall behind seating is stud sheet rock and windows.

I have 1 1/2" AC duct board on the left wall from wainscot to ceiling and hope to build a book case in back. The ceilings are coffer-ed with 1 1/2" AC duct board panels in the bays. Center bays 2x4 and side bays 2x2 ish. The duct boards are cloth covered. (dark blue:R)

Tell me what I forgot or where am I going wrong. TNX Bear.
 

·
Registered
Joined
·
2,398 Posts
Re: Hi SteveCallas and everyone .I'm lost on a LLT.

With all due respect, that's kind of confusing :huh:

You want your subs above your television, up against the ceiling - if you really feel you need to do this, that's fine I guess, but you do realize that these are going to be several hundred pound enclosures, right? Why not make them part of a stand that the tv rests on?

Is the 567 liters for each sub, or the combined volume? Why have you opetd for a slot port as opposed to a cylindrical port?

As for a space between the enclosures and surrounding walls, your best bet is to leave that space empty. Keep the enclosure about 1" shorter than the ceiling and about 1" out away from the back and side walls.

If you have a large open space to your right and a solid concrete wall to your left, my first option would be to position my subwoofers as close to the left wall and left corners as possible for maximum sound reinforcement.
 

·
Registered
Joined
·
18 Posts
Discussion Starter #4
Re: Hi SteveCallas and everyone .I'm lost on a LLT.

With all due respect, that's kind of confusing :huh:

You want your subs above your television, up against the ceiling - if you really feel you need to do this, that's fine I guess, but you do realize that these are going to be several hundred pound enclosures, right? Why not make them part of a stand that the tv rests on?
Tnx Steve for you quick come back. Your expertise and opinion is Much very appreciated.
Attaching...(screwing) to the studs and joists will more than adequately support the boxes, even if I used isolation stand offs up to 1 inch I suppose. On the back wall there are 4 studs behind each box and 2 ceiling joists running across the top. I originally thought I would build them as the base cabinet but (1) I felt I would lose valuable storage space for what ever people put in those base cabinets behind closed doors. (2) The space above the TV is difficult to reach and use for easily accessible "stuff" other than shelving for nic nacs. IOW wasted space.

Besides. I was hoping to not have to cover the drivers for shock and awe purposes and in the base cabinet I would need a chain link mesh to keep my grand kids and idiot friends from poking their fingers and toes into the cone..
Is the 567 liters for each sub, or the combined volume? Why have you opetd for a slot port as opposed to a cylindrical port?
Yes, 567 liter each box. Slots for looks I guess.:1eye: I thought 2 vertical slots 12" off the center on each side of the divide and pretty much the same height as the speaker diameter (14 inches opening plus the 2" rounded over bezel around the slot) with the speaker 40 inches left and right of center in each box which would place the 18" driver at the outer line of the TV and directly above the line arrays on either side of the TV. Looks/balance had some to do with it plus I felt the vertical slots would give the best infrasonic boost/blast to the center of the room where most people (me) sit, Even though I know those freq are non-directional per se I want my hair to blow back when the bomb goes off or the organist hits the 64 ft subsonic organ stop. (pipe)


As for a space between the enclosures and surrounding walls, your best bet is to leave that space empty. Keep the enclosure about 1" shorter than the ceiling and about 1" out away from the back and side walls.
The 1" distance from the walls/ceiling is doable but I figure mass (the combination of 1/2" sheet rock and 3/4 MDF had more damping effect than basically a sealed 1" sound box (drum), even with box wall reinforcements. Now filling that 1" space with high density spray in foam might have some advantage but I don't think as much as doubling up does. I been wrong before.. I have a whole pile of wrongs outside my work shop.. :duh: I was thinking of the 1/4 inch spray foam to more take up the inherent typical un-squareness of most frame built houses where walls meet ceiling and high sheet rock mud seams without leaving a drum gap between the box and wall/ceiling.

An Bear Opinion moment; Because spray in foam is so dense I figure it would work better at low freq damping as a filler. Just as the dense HVAC duct board is designed for low freq air noise attenuation through the ducts. R-13 fiberglass insulation and soft couch foam as a acoustic at low freq compared to thick HVAC duct board is practically useless except to John Mansfield, Home Depot and the upholstery shop. Not to say its the bass node boom cure but it sure does more.

If you have a large open space to your right and a solid concrete wall to your left, my first option would be to position my subwoofers as close to the left wall and left corners as possible for maximum sound reinforcement.
The very reason I wanted to go 18" vs 15". To Rely on the drivers rather than so much on room reinforcement for energy. The left corner is not very appealing with space very limited and I was looking for reinforcement by essentially useing the left half of the whole room as the corner. I suppose I could open the boxes center to combine each other and get a 1134 liter "big box" and put in two 18s to the left side and super vent the whole thing. Might look a little weird and out of balance but should work. There is always that aesthetic compromise. :dizzy:

Where you able to make sense of my numbers For box, tune freq, and port size?. Why did you ask about the slot vs round? What does one need for a room response calculation? Based on what I have given here for numbers can a performance efficiency be determined? Like I said.. I read too much and I'm starting to go in circles.
 

·
Registered
Joined
·
18 Posts
Discussion Starter #5
Re: Hi SteveCallas and everyone .I'm lost on a LLT.

The 650 liter rule does not apply to the IXL-18 due to the drivers parameters. It works well in 400 liters or less.
EVEN In the LLT design? HUH? Well that would make life a litlle easyer..
 

·
Registered
Joined
·
18 Posts
Discussion Starter #7 (Edited)
650 liters is a target mainly for the Avalanche 18, FiCar Q18, and SoundSplinter RL-p18. The Maelstrom X 18 likes less, and the Mach 5 IXL 18 likes even less.
I wrote a reply to your first reply a hour or so ago.. It said it was redirecting to the mods for their approval. Without trying to sound political is this some censure board or something. I never said anything out of the ordinary. Where is it?

How much less. Is there a known optimum volume for the IXL 18. I thought because its a black arts LLT the regular Win box programs doesn't figure it . Is 400 liter the "it" like Mike said.

Now according to Mach they suggest 350 liter 15 hz tuning in a EBS. Are we talking the same technology with different terms for the same thing?
 

·
Premium Member
Joined
·
19,397 Posts
I wrote a reply to your first reply a hour or so ago.. It said it was redirecting to the mods for their approval. Without trying to sound political is this some censure board or something. I never said anything out of the ordinary. Where is it?
There was no problem with the post, it's a forum glitch that happens from time to time. Post #4 has been approved, the duplicate you posted has been deleted.
 

·
Premium Member
Joined
·
19,397 Posts
How much less. Is there a known optimum volume for the IXL 18. I thought because its a black arts LLT the regular Win box programs doesn't figure it . Is 400 liter the "it" like Mike said.
There is no black art in LLT. It's a big ported box tuned low to get the best balance of low end extension and SPL. 400 liters does it for the IXL-18.
Now according to Mach they suggest 350 liter 15 hz tuning in a EBS. Are we talking the same technology with different terms for the same thing?
Yes. EBS and LLT both focus on large low tuned box sizes the get the most low end extension from the sub.
 

·
Registered
Joined
·
2,398 Posts
Bear Paws said:
Attaching...(screwing) to the studs and joists will more than adequately support the boxes, even if I used isolation stand offs up to 1 inch I suppose. On the back wall there are 4 studs behind each box and 2 ceiling joists running across the top
So are these boxes going to be anchored to the ceiling and back wall as opposed to free standing on top of a tv credenza?

The 1" distance from the walls/ceiling is doable but I figure mass (the combination of 1/2" sheet rock and 3/4 MDF had more damping effect than basically a sealed 1" sound box (drum), even with box wall reinforcements. Now filling that 1" space with high density spray in foam might have some advantage but I don't think as much as doubling up does. I been wrong before.. I have a whole pile of wrongs outside my work shop.. I was thinking of the 1/4 inch spray foam to more take up the inherent typical un-squareness of most frame built houses where walls meet ceiling and high sheet rock mud seams without leaving a drum gap between the box and wall/ceiling.

An Bear Opinion moment; Because spray in foam is so dense I figure it would work better at low freq damping as a filler. Just as the dense HVAC duct board is designed for low freq air noise attenuation through the ducts. R-13 fiberglass insulation and soft couch foam as a acoustic at low freq compared to thick HVAC duct board is practically useless except to John Mansfield, Home Depot and the upholstery shop. Not to say its the bass node boom cure but it sure does more.
Unfortunately I'm just not following. Can you perhaps post a crude drawing of what you are envisioning? :hide:
 

·
Registered
Joined
·
18 Posts
Discussion Starter #11
So are these boxes going to be anchored to the ceiling and back wall as opposed to free standing on top of a tv credenza?
Yes.. Think of it as to one large 126 inch long trapezoidal box divided in half (the long way) internally by a double wal mounted into the wall/ceiling corner. The credenza/armoire/entertainment center is incidental to the actual mechanical structure and mounting of the sub..
Unfortunately I'm just not following. Can you perhaps post a crude drawing of what you are envisioning? :hide:
I'll try to in the am.
 

·
Registered
Joined
·
2,398 Posts
Yes.. Think of it as to one large 126 inch long trapezoidal box divided in half (the long way) internally by a double wal mounted into the wall/ceiling corner
That's going to physically couple it to the rest of the house and whenever you play anything with bass at what I would guess to be even moderate levels, it's going to be heard and felt everywhere. No amount of spray foam - let alone less than an inch - is going to prevent that from happening.

If you are ok with this, more power to you, but I would try to avoid it.
 

·
Registered
Joined
·
18 Posts
Discussion Starter #13 (Edited)
That's going to physically couple it to the rest of the house and whenever you play anything with bass at what I would guess to be even moderate levels, it's going to be heard and felt everywhere. No amount of spray foam - let alone less than an inch - is going to prevent that from happening.

If you are ok with this, more power to you, but I would try to avoid it.
Hmmm. Being a vapid sexist as I am. Like women, I thought bass was to be felt and seldom heard?:devil:
Isn't that what this whole exercise of BIGGER and BADDER BASS is all about. Other wise I might as well stay with my Sony sealed 12 incher. :sarcastic:

WE Got used to that with the 4 AE IB 15s at the other house. As did the wife.
I have considered coupling and I don't think it will be as bad as the IBs. That loosened the hardwood floors, cracked plaster and made the poor dog :hide:

Here is the problem Steve and Mike, for good or bad I'm a mechanic not a engineer. Once I run out of fingers and toes to count on I reach for the hammer. When I read your LLT article I understood it intuitively from the mechanical perceptive. I liked the idea. I no longer have the place, space, or itch (literally) to do another IB and this LLT seemed to fill that empty spot I had.

That aside. The important question now has been answered, I believe. Box size. After reading your dissertation on LLTs and other writes I was getting confused as to how to figure volume and then thus port size.. Mike took issue with my calling it a "black art" but I yet to see or find a formula or program that address optimum box volume for LLT. What in the parameter numbers brings us to 400 liters? I dunno. :huh:

Right now I have come up with a box net each (1 of 2) 14.152 cu ft {400.5 liter} at approx 14.750 ish hz with a slot port of 3.5" x 14.250" by 36.543" long. Radius the port opening at 1.5" and fold the port runner into a L or one shorter legged U shape inside the box. Maybe even the the U's short leg opening directly facing the back of the driver depending on that days ambition. .
What have I missed..


I do have a question about large ported boxes. What would the down side be of useing a AE IB15 http://aespeakers.com/shop/catalog/product_info.php?products_id=55 in a 550 liter ported box. The have a looser vas 439 L to the IXL 18's 274 L but less xmas. They are less expensive and a really nice driver. Albeit not as intimidating looking as a couple 18s visually but still awesome.
 

·
Premium Member
Joined
·
19,397 Posts
Just to make sure we're on the same page here, I never took issue with anything, I simply stated there is no magic involved in LLT. My apologies if I came across any differently.

As for what in the parameter numbers brings us to 400 liters, it is how the sub models. Modeling programs show the frequency response and SPL of the IXL-18 in 400 liters tuned to 15 hz with the appropriate power input to reach Xmax. For the IXL-18 400 liters tuned to 15 hz is the best combination of low end extension and SPL.
 

·
Registered
Joined
·
2,398 Posts
bear paws said:
After reading your dissertation on LLTs and other writes I was getting confused as to how to figure volume and then thus port size.. Mike took issue with my calling it a "black art" but I yet to see or find a formula or program that address optimum box volume for LLT. What in the parameter numbers brings us to 400 liters? I dunno.
- Tuning <=15hz
- Cylindrical port diameter >= 6” for 15" drivers and >=8" for 18" drivers
- Port opening clearance equal to at least the port diameter in all directions
- First port resonance >=190hz
- No discrete high pass filter
- FR with a ~4db/octave rolloff between the tuning frequency and the lowest room node
- Minimal resonance enclosure (use of cylindrical concrete forms made of paper – generically referred to
as Sonotube - for the enclosure makes this easy)

If you can achieve these port and rolloff characteristics with a reasonably flat frequency response using something different than 400-450 liters, please let me know. 650 liters results in a tuning region that has a peak. There is no equation that spits out 400-450 liters, you just have to work with it and see what volume achieves the desired performance characteristics. That said, if you gave myself, Mike, or someone else who understands the LLT characteristics a brand new driver and asked us to independently reach an ideal volume, I would wager that we would come within 50 liters of each other.
 

·
Registered
Joined
·
278 Posts
I do have a question about large ported boxes. What would the down side be of useing a AE IB15
Nothing other than possibly increased box size. FWIW, just 'running the numbers' of the IB15A in an ancient X-bass alignment I get 430 L/15.3 Hz, but this alignment is highly damped for blending to horns, so can be somewhat larger tuned a bit lower to flatten it out more like an EBS as long as you don't tune it < ~0.7*Fs for drivers with a < ~0.577 Qts.

GM
 

·
Registered
Joined
·
18 Posts
Discussion Starter #17
Just to make sure we're on the same page here, I never took issue with anything, I simply stated there is no magic involved in LLT. My apologies if I came across any differently.

As for what in the parameter numbers brings us to 400 liters, it is how the sub models. Modeling programs show the frequency response and SPL of the IXL-18 in 400 liters tuned to 15 hz with the appropriate power input to reach Xmax. For the IXL-18 400 liters tuned to 15 hz is the best combination of low end extension and SPL.
Same page.:T I too was not at issue with your comment. Just lack of a better word at the moment.

Got it. I think I see the error of my ways. I was looking at LLT as "Large" first and then tune. In actuality the method is to determine the "low" tune first (a little Below FS) and then build the box around it or to suit the low tune freq rather than tune the box after its sized...Because normally with programs you input the TS numbers and it decides the optimum box size with a tune above fs based on some black magic :R (to me) formula. Like the WinISD wants to make it a 206 L box at 19.34 hz with a 4" x 9.3" Long port. Or do I have that wrong too. I'll add that to the pile of wrongs out back also. :dizzy:

So for me its not necessary to know why just how.
 

·
Registered
Joined
·
18 Posts
Discussion Starter #18 (Edited)
- Tuning <=15hz
- Cylindrical port diameter >= 6” for 15" drivers and >=8" for 18" drivers
- Port opening clearance equal to at least the port diameter in all directions
- First port resonance >=190hz
- No discrete high pass filter
- FR with a ~4db/octave rolloff between the tuning frequency and the lowest room node
- Minimal resonance enclosure (use of cylindrical concrete forms made of paper – generically referred to
as Sonotube - for the enclosure makes this easy)

If you can achieve these port and rolloff characteristics with a reasonably flat frequency response using something different than 400-450 liters, please let me know. 650 liters results in a tuning region that has a peak. There is no equation that spits out 400-450 liters, you just have to work with it and see what volume achieves the desired performance characteristics. That said, if you gave myself, Mike, or someone else who understands the LLT characteristics a brand new driver and asked us to independently reach an ideal volume, I would wager that we would come within 50 liters of each other.
Wow.... sorry. I wasn't trying to convince anyone of anything. I was just asking because I figured I was wrong. My intuition told me I was... That's why I asked you guys. I said in the title I didn't understand the LLT characteristics and was lost... Apparently I was and got pointed in the righter direction and was convinced on 400 liter after the the 3rd post....TNX for the help.

As I build I'll post because its different and it may help someone not to make the same mistakes if I'm wrong...Again.. .However if it works...:yay2: It will be a few weeks before I start. Need to order the drivers and finish up a few honey do-s. In the mean time all criticisms welcome. I'll be lurking.

Because of the layout design of the cabinet/entertainment center the available space of 567 space is cast in wood so to speak thus leaving me with 167 liter of excess space. I will need to put a false back wall inside the original box design to bring it down to 400.. I may build a cylindrical or curved wall/partition to reduce enclosure resonance and isolate the front 400 space from the rear 167.. Ala 1/2 radii sono tube length wise, the driver coming from the side rather than the end.. I wonder if after I cut the Sono tube in half, I double up and laminate the two halve radii of the sono tube together whether that will be rigid enough to equivalent a 3/4inch MDF.? Hmmm. The hard part may be finding a 24 inch tube 6 ft long to cut down in half length wise. Bracing the half tube should be easy. I will brace it from the back side thus eliminating any internal window bracing in the noisy area. The front baffle I figure 3/4 MDF and topped with 3/4 Baltic plywood. Maybe one brace in the middle.After all the baffle is 63" by 21".
 

Attachments

·
Registered
Joined
·
2,398 Posts
The sonotube backing seems like a lot of extra work for essentially no real benefit. I would just use a piece of MDF. Also, your slot port construction would be easier if you guided it along one of the internal sides of the enclosure instead of keeping it free standing in the middle.
 

·
Registered
Joined
·
18 Posts
Discussion Starter #20 (Edited)
The sonotube backing seems like a lot of extra work for essentially no real benefit. I would just use a piece of MDF. Also, your slot port construction would be easier if you guided it along one of the internal sides of the enclosure instead of keeping it free standing in the middle.
TNX.I been rethinking that curved idea also. It seemed like it would afford minimal resonance like you mentioned in your bullet points but I agree the benifit of the work/cost could be as well achieved other ways.
Yep on the port. I was more trying to illustrate the folding idea. I was going to build the port assembly outside the box. I think that would be easier because of the curved fold.. .. Then slide it in with the back portion of the wave guide up against the back partition wall and throw a couple screws in it to secure it against the back wall. The 1 1/2" front flare bezel I will probably make out of 2x2inch stock and rabbit it to sit into the box opening maybe 3/4 inch proud..also rounding over 3/4" on the outer perimeter of the bezel."... With the 18" hole in the front before I put the driver in I could practically crawl in there and work hunched over.:unbelievable:

On slot ports..It would seem important also to round over the inner opening. Like the round tube flares Yes? But I don't see (or haven't noticed) that in other builds and plans. Any thoughts?
 
1 - 20 of 24 Posts
Top