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Discussion Starter · #1 · (Edited)
I have never built a speaker or a sub.

I have been reading about LLT and I am fascinated by the tech. I was thinking of adding a larger sub to setup.

My modest room & setup:
mains: Klipsch RF15x2
center: Klipsch RC25
TV: Samsung 61" rear projection 1080p
current receiver: broken HK unit [nickname: Crispy]
-the room is in the lower level of the house and is about 14'x22'x8' with 1 open doorway leading to a hallway and the rest of the house
-In December, I am expecting a new Onkyo TX-SR607 which is 7.2 and possibly a 12" BIC sub which is part of what began the inspiration for this. I feel like I would want more bass than a retail 12" cheapo sub will provide.

I expect to use a new sub for 70%-90% HT and the rest music.

I say "small-ish" because I'm imagining a large sub but it would be small by LLT standards.

The first question is: does it make sense to try to create a LLT using a single 12" driver (most seem to be 15" or 18")? I am trying to keep cost and size down.

I have been thinking of building the sub as an "end-table" style configuration. I was thinking of keeping the largest dimension 2.5' or less [30"x26"x24" or 28"x26"x24" or about 195L to 210L net].

proposed construction:
net volume of 175-225 L
slotted port at bottom
12" driver
1" MDF

Will I be able to get this tuned low enough? If not, approximately how big will I need to go for a 12" driver?

Amp:
plate amp or external?
I like the idea of simplifying the overall system by using a plate amp like a bash 300.

My mains and center will be simply running off my HT receiver (Onkyo TX-SR607) so it would be nice to simply use one of the sub out lines for the sub input.

On the other hand, for $50 more, I can get a behringer ep1500 which would simplify the sub box itself and give me more power.
 

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LLT's are usually tuned to 15 hz or lower, a single 12" can't move enough air to be effective that low. A large ported box tuned to 18 - 20 hz would get the most performance from a 12" sub.

195L to 210L net is big enough for a 15" or even a 18". What is your budget for a sub and an amp?
 

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Discussion Starter · #3 ·
LLT's are usually tuned to 15 hz or lower, a single 12" can't move enough air to be effective that low. A large ported box tuned to 18 - 20 hz would get the most performance from a 12" sub.

195L to 210L net is big enough for a 15" or even a 18". What is your budget for a sub and an amp?
Hmmm, I like the idea of a 15" but I didn't think the box I was imagining would be large enough.

As for price, I was thinking about a $400 budget for amp and driver. Assuming I get a $200 ep1500, the Tempest X2 is a little more than I want to spend. Same story for the Dayton Titanic Mk III.

The problem with jumping up to 15" is that I want to limit the budget yet I don't want to buy a POS driver. The 2 above are 'close' to my price range. Any other good deals on 15s out there? Where else should I look other than the 2 sites in those 2 links?

Is there a realistic amp for <$200 for this type of application? [plate or external, I'm not really sure what kind of power this would need]
 

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Discussion Starter · #4 ·
Possibly something like this?:

Boxnotes report for project: default
--------------------------------------------------------------------------------------------

Finished size 2' in wide 2' 2 in high 2' 6 in deep - Panel thickness 1 in - Double Front Panel

Internal Volume: 6.8 cu.ft Working Vol 6.35 cu.ft Tune 14.3hz

Component volumes: Ports = .03 cu.ft Bracing = .27 cu.ft Driver = .14 cu.ft Total = .44 cu.ft


Cutting List
--------------------------------------------------------------------------------------------
Panel dimensions show finished size

Top panel 2' inches wide 2' 5 inches deep

Front outer panel 2' inches wide 2' 2 inches high

Front inner panel 1' 10 inches wide 2' inches high

Left side panel 2' 5 inches deep 2' 1 inches high

Right side panel 2' 5 inches deep 2' 1 inches high

Rear panel 1' 10 inches wide 2' inches high

Bottom panel 1' 10 inches wide 2' 5 inches deep

Shelf brace 1' 10 3/8 inches wide 2' 3 3/8 inches deep

Shelf brace includes 3/16 inch all round for rebating into 4 adjacent panels


Resonances
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Port Resonance 615 hz

Unable to calculate Driver to bottom wall resonance

Box top to bottom resonance 282 hz

Driver to top wall resonance 282 hz

Driver to rear wall resonance 252 hz

Box front to back resonance 250 hz

Driver to side wall-1 resonance 614 hz

Box side to side resonance 307 hz

Driver to side wall-2 resonance 614 hz


Port details
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Number of ports: 1
Internal Diameter: 2 7/8 inches
Length: 11 inches
Wall Thickness: 1/16 inches


Driver details
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Driver size: 15 inch
Number of Drivers: 1

Location of acoustic centre
-----------------------------------
Box front to mid-depth of cone: 1 3/4 inches
Box top to driver centre: 2' 1 inches
Offset from vertical centreline: 0 inches


--------------------------------------------------------------------------------------------
Report generated at: 15:47:20 on 11-19-2009 from Boxnotes Version:3.1
The latest version of Boxnotes is available at www.subwoofer-builder.com/freesoft.htm
 

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Your budget defines what can be achieved. $400 will put you in the 12" sub range.

$200 for an EP1500 is only part of the story. The amp doesn't have a hi pass filter which is required for sub protection at the lower frequencies. An add on unit is about $100. In your case a plate amp would be a better choice as most of them have a hi pass filter built in.

For $440 shipping included you can get the TRIO12 sub kit, definitely the best value for your dollar. You get the sub, 2 passive radiators, a 500 watt amp and all mounting hardware for a sub designed to fit in a 20" cube.

http://www.creativesound.ca/pdf/Quartet12B_Subwoofer_Kit.pdf
 

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Discussion Starter · #8 ·
Right Mike. I forgot there are guidlines in the LLT essay about volume for 15" drivers. I am willing to adjust size to make this work [before I was thinking that there was a volume that would work for a 12 - ie. that the theory would scale down to a 12" driver].

So, assuming 15" and that I need 300L+ effective...

it looks like a 26"x28"x34" box with a 28" long 6" port will work for a 15" driver (326L effective and tuned to 14hz). It's a little bigger than I was thinking but I would rather increase size than give up on the theory of the LLT at this point.

Does this sound realistic?
 

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Discussion Starter · #12 ·
from the internet, I see:

Bridged Mono: 1 kHz, 0.1% THD
- 8 ohms: 900 w
- 4 ohms: 1400 w
So I guess the next question is: is there an amp out there that will work well in this application with less power and that would cost less? It seems the ep1500 is overkill...
 

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Discussion Starter · #14 ·
It's not really overkill, you'll have plenty of power for headroom, and the amp will never clip.
OK, so clearly it's amateur-hour from my end on building a sub.

So, assuming I create a LLT box (for a 15" Tempest X2 and a EP1500) which is approximately 35"x30"x28" with a 6" port tuned to 13hz...

what else do I need besides the driver, amp, and the basics like wiring/connectors?
 

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That won't work. The net volume of the cabinet is about 13.5 cu.ft. Tuned to 13 hz, 6" diameter port is too small for the air speed. An 8" diameter port will work, but a 13 hz tuning means the port would have to be 53" long. Raise the tuning to 15 hz and port length drops to 38.5", much more manageable.
 

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Discussion Starter · #16 ·
That won't work. The net volume of the cabinet is about 13.5 cu.ft. Tuned to 13 hz, 6" diameter port is too small for the air speed. An 8" diameter port will work, but a 13 hz tuning means the port would have to be 53" long. Raise the tuning to 15 hz and port length drops to 38.5", much more manageable.
What are you using to calculate these numbers? I'm using boxnotes to get the volume, port diameter and length, and tuning frequency.
 

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Discussion Starter · #18 ·
Has anyone built a box LLT from the application guide for the Tempest X2 provided on the diy cable site? I haven't found one. I realize it references sonotube but a box should work as long as the volume is the same, correct?

LLT (340L – 12 cubic feet) Tuned 12Hz
This is a large build, using a low tuning frequency and no subsonic filter. This is a design popularized by Steve Callas of Home Theater Shack fame. It is similar in concept to an EBS alignment and the general idea is that you use the port extremely low in frequency so that no subsonic filter is needed. The port is of little value with output >20Hz so most of the output is handled by the driver, rather than a combination of driver + port in most standard ported designs. This sub goes deep, but for the 20-40Hz range, it will have less output than a sub with a higher tuning frequency. For deep in-room response though, the only competition is from IB subs. If you can live with the size, this is an awesome HT sub that can plumb the depths unlike any commercial subwoofer available. It will sound less exciting, due to the loss of output 20-40Hz but if you don’t need the extra output, or can build multiple subs (one in each corner), you can have the best of all worlds. Due to the large enclosure size the port can also be upsized such that it won’t compress as much at full output. Since the tuning frequency is at 12Hz, most of the output is significantly lower in SPL compared to the content above 20hz. In most cases, port chuffing is a non-issue. Sonotube (round concrete forms) make the ideal enclosure for LLT designs. They don’t require bracing, are much lighter than MDF and their form-factor, makes very efficient use of floor space. A 20” Sonotube, 72” tall would be large enough for this example.
 
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