Home Theater Forum and Systems banner
1 - 20 of 23 Posts

·
Registered
Joined
·
33 Posts
Discussion Starter · #1 ·
I posted this over at the Cult but after reading some of the article thread on LLt and the IB makeover I think I am interested in this option.


POST FROM CIB

I am pondering an IB sub and would like your help on what to do in this area for a sub, if you have photo's to help me understand that would be great.
Being a total newb to IB I need recommendations on which driver's and a direction on how to build.
This is for HT use 95% and casual (no critical) listening. I do like heavy bass feel for movies but it would still need to sound good so if I am on the wrong track please feel free to steer me or tell me this is the wrong direction all together.
I think the amp would be an EP2500 and planning to invest in a BFD.

If I could get 2 18's (maybe these Ficaraudio in either the SSD or Q model if the Q is worth the $ upgrade) in the area that would be great but if I have room for more please let me know. I don't have a budget yet I just want the best value kinda stuff, I understand there is no free lunch but there is a point that performance to dollar ratio has a quick rise to a point then it takes alot more $ for small performance gains so I want to find the sweet spot of spending to performance and I am sure many of you have found it already.

I am currently using a HSU VFT III mkII or something like that model and when I play around with the sub setting to get it to the sound I like it loses control on big peak's so I am thinking two larger subs should give me the sound and feel without having to over drive them.

Here are some photo's
Room is 14X22 with cathedral ceilings.
The TV is now above fireplace and the space I am thinking of using is behind the mantle on the right with q chimney up the middle.


Is this enough info to get some ideas?

END



Can someone design me a LLT for the opening behind the right speaker picture for any 18" woofer (with price/performance information above in mind) using 24.5" wide 18" deep and I would like to be under 30" high if I can. I am not real good when it comes to technical details my mind just turns off so sorry if I left something out or missed something obvious.

Thanks
 

·
Registered
Joined
·
33 Posts
Discussion Starter · #2 · (Edited)
I think I can move to opposite wall and go higher than 30" if needed, ideally I would like two 18"s if I have the space. What ohm woofer would I need to run them with a EP2500 amp in bridged mode so the amp would see 4 ohms. I forgot the rules of figuring this out but I know that it takes two 8 ohm spk wired parallel to get to 4 ohm I just don't know if this changes with the amp bridged mono.

The speakers would be firing 90* in relation to the mains and have about 5' until the hit the rooms side wall basically opposite of the left rear speaker in this photo.



The wall proposed for an in wall LLT is identical to this one just on the opposite side.




Yes we did change the orientation of the seating/TV, first picture is the previous seating and the second is current.




http://www.behringer.com/EP2500/index.cfm?lang=ENG

Thanks again for any help.
 

·
Registered
Joined
·
33 Posts
Discussion Starter · #4 ·
I can go to 54" or higher high on the other side which should be 13.5 cu.ft less the woofer volume, can I get an example of what would be the ideal size for a single 18" woofer.
Is the 12 cu.ft needed for the woofer above for a single or dual application?
 

·
Registered
Joined
·
33 Posts
Discussion Starter · #6 ·
It is a sticky at the top of this forum, I didn't know what one was until reading here either.
 

·
Premium Member
Joined
·
19,397 Posts

·
Registered
Joined
·
2,398 Posts
How much are you wanting to spend?

A pair of Mach5 IXL 18s at 13 net cubes each with an 8" diameter port that is ~44" long for a ~14.5hz tuning would be great. Yes, 44" length breaks my rule of keeping first port resonance above 190hz, however, I had a nice debate here a while back discussing extra long port lengths and found that the impact of output from the sub above 150hz using a 4th order crossover at 80hz plays almost no role. I have not yet modified my LLT Explained thread on this, but I will soon.

Sounds like the driver will be front firing and port opening at the top of the enclosure?

If you are willing to go taller, we can start looking at Maelstrom X LLT options. You'd need to get to ~17 net cubes for that.

Wise choice on the switch to LLT by the way - more, better performance for your dollar.
 

·
Banned
Joined
·
1,131 Posts
How much are you wanting to spend?

A pair of Mach5 IXL 18s at 13 net cubes each with an 8" diameter port that is ~44" long for a ~14.5hz tuning would be great. Yes, 44" length breaks my rule of keeping first port resonance above 190hz, however, I had a nice debate here a while back discussing extra long port lengths and found that the impact of output from the sub above 150hz using a 4th order crossover at 80hz plays almost no role. I have not yet modified my LLT Explained thread on this, but I will soon.

Sounds like the driver will be front firing and port opening at the top of the enclosure?

If you are willing to go taller, we can start looking at Maelstrom X LLT options. You'd need to get to ~17 net cubes for that.

Wise choice on the switch to LLT by the way - more, better performance for your dollar.
If port resonance is at about 110Hz or above and a 4th order crossover at 80Hz is used there will be absolutely no audible effects. For safety's sake I recommend when modeling keeping port resonance at or above 120Hz if an 80Hz crossover is to be used because modeling rarely exactly what will occur in the real world.

The original discussion can be found here and a follow up article can be found here.
 

·
Registered
Joined
·
33 Posts
Discussion Starter · #10 · (Edited)
I can go larger, just tell me how big to go and any design tips you can to get me started would be great. I think I can stay with one 18" for now and I would like to do a square port so it you could calculate what size would be needed and how much volume the port and woofer will take up I would greatly appreciate any assistance you can offer.

I can budget a single Maelstrom if the performance is worth the extra $ over a Fi or similar
 

·
Registered
Joined
·
2,398 Posts
Out of curiousity, why do you want to use a square port? For a given cross sectional area, a circle is the best shape to minimize turbulent air flow.

I'd shoot for 17 effective cubes with an 8" diameter port that is 36" long to give you a tuning just under ~14hz. Just the right balance between extension and headroom in my opinion. Though there have been no detailed measurements posted of either driver, I think it's relatively safe to say the Maelstrom X is a better driver than the IXL.
 

·
Registered
Joined
·
33 Posts
Discussion Starter · #13 ·
The only reason to go square is that I think they look better and I dont have to find/buy a round port.
Can someone make a graph or something to show response of above LLT to a typical size box and tune to help me understand better.

How much volume does the woofer and port use?
 

·
Premium Member
Joined
·
19,397 Posts
Here's a SPL graph of the Maelstrom with 1400 watts applied. Cone excursion is not exceeded until 12 hz. The tuning is a little under 14 hz with a 5" x 10" port 36 inches long. If the port is built from 3/4 inch material and one side is against a wall of the sub, then it displaces 1.3 cu.ft. I'm not sure what the Maelstrom displaces, you can ask Kevin on the Exodus Audio forum.

Maelstrom.JPG
 

·
Registered
Joined
·
33 Posts
Discussion Starter · #17 · (Edited)
to get 36" I would need to use the back wall and either a side wall, front wall or the top wall which would make the port high up the wall.
1) 17" deep I would have to 90* the port does this change anything in tuning and is it 19" + the 5" port already present from the front 17" part.
Can someone draw it out somehow.
It seems the best bet would be to run the port starting in the upper area in front face of the box and have it stop around 24" above woofer and have a 90* out the front. Does this sound right.
Do I mount the sub as low as I can in the wall as long as it is clear of obstruction.

 

·
Premium Member
Joined
·
19,397 Posts
to get 36" I would need to use the back wall and either a side wall, front wall or the top wall which would make the port high up the wall
For this design you need 18.5 cu. ft. gross internal volume after tyhe displacement of the sub, port and bracing are added. What are the dimensions of the cabinet that you will be using? From that we can figure out the best port placement.

The port needs to be 34.5 inches long to get a 14 hz tune if the port is 5" x 10".
 

·
Premium Member
Joined
·
19,397 Posts
Why did the port go from 36" down to 34.5"
An 8 inch round port 36 inches long tunes to 13.77 hz. A 5" x 10" square port 34.5 inches long tunes to 14 hz.

This model of 17 cu.ft. tuned to 14 hz has a huge advantage in low end output over the smaller 6 cu.ft. box shown in the link.
 
1 - 20 of 23 Posts
Top