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Discussion Starter · #1 ·
I'm building a PR enclosure for an LMS Ultra 5400. I'm looking for the practical point of LFE extension without overly affecting other frequencies. I'd like to get the most LFE impact of movies like Tron Legacy, U-571, War of the Worlds, and King Kong etc. This is my first real subwoofer and I don't really have a frame of reference for what is sufficient SPL in the these frequencies. My room is likely going to reinforce frequencies only above 25 Hz, so the subwoofer needs to do all the LFE work.


Below are three enclosure variants I'm considering... Blue has the most at 20 Hz and the least at 10 Hz, while Yellow has the least at 20 Hz and the most at 10 Hz, with green in between. They're all the same in the middle around 14 Hz. I'll be using RoomEQ to flatten the in-room response with a FBQ2496, and to filter LFE frequencies to match driver excursion limits.


Blue: 8.125 ft3 tuned to 16.79 Hz with 3 PRs ([email protected] / [email protected] compared to Yellow)

Yellow: 8.125 ft3 tuned to 13.84 Hz with 2 PRs ([email protected] / [email protected] compared to Blue)

Green: 7 ft3 tuned to 14.85 Hz with 2 PRs (In Between)


When looking at the responses, is it better to give up some 20 Hz to get more 10 Hz content for the most impact in these types of these movies, or is it better to retain the 20 Hz region?


Thanks in advance.

 

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Discussion Starter · #3 ·
Thanks, I just read the thread.. I see you went all out for 20 Hz and nothing toward 10 Hz. I'm just concerned that by going all out at 20 Hz, I'd miss out on 10 to 14 Hz, which some movies can have a lot of. I've read that you don't know what you're missing until you dig into those frequencies. I see you did a quad sealed, which should hit hard at 10-14 Hz, albeit consuming a lot more power and costing lots more money than I have. I'll read that thread as well.


What I might do is build the enclosure for both the blue and yellow, by making the cabinet 8.25 ft3, and making a removable 3rd PR with a bolt on "plug" over the 3rd PR hole when operating with 2 PRs.
 

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Quote:
Originally Posted by Mr. Neverbicker  /t/1469891/help-with-lms-ultra-5400-enclosure-with-practical-lfe-extension#post_23244601


Thanks, I just read the thread.. I see you went all out for 20 Hz and nothing toward 10 Hz. I'm just concerned that by going all out at 20 Hz, I'd miss out on 10 to 14 Hz, which some movies can have a lot of. I've read that you don't know what you're missing until you dig into those frequencies. I see you did a quad sealed, which should hit hard at 10-14 Hz, albeit consuming a lot more power and costing lots more money than I have. I'll read that thread as well.


What I might do is build the enclosure for both the blue and yellow, by making the cabinet 8.25 ft3, and making a removable 3rd PR with a bolt on "plug" over the 3rd PR hole when operating with 2 PRs.

I think the final tuning frequency for the dual PR build was 17hz, so it was solid to 15hz or so.


In my room, anything under 14hz pretty much doesn't exist, even with quad sealed 5400s with 4kw each.


With my latest horns I'm back to that 16-17hz tune with solid output to 13-14hz. Losing that 10-13hz range really doesn't change anything for me in my room.


There are movies with 15-20hz bass, but the list of movies with bass near 10hz is way way less.
 

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I don't understand PR builds. What is the allure for these? LMS 5400 PRs cost so much, wouldn't it be more better to just stick with 2 sealed 5400 builds?

Unless of course, you are like lukeamdman and absolutely don't need anything under a certain frequency.
 

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Quote:
Originally Posted by lukeamdman  /t/1469891/help-with-lms-ultra-5400-enclosure-with-practical-lfe-extension#post_23244998


In my room, anything under 14hz pretty much doesn't exist, even with quad sealed 5400s with 4kw each.

Losing that 10-13hz range really doesn't change anything for me in my room.

I get "usable" output to 12hz with just two sealed LMS-18's (6cubes) with 4kW each; and high woofer excursion down to 5hz (with less usability).

However I will say that a lot of the output at those frequencies are from harmonics, which is to be expected.


I could easily bottom out the LMS at any frequency at or below 30hz if I really wanted to (which I don't
).


I don't run a high-pass filter (most of the time) and I'm boosting below 20hz by 6db and running the subs hot. Which usually isn't a problem, unless I'm listening to ULF-heavy bass music or movies at loud levels.


I went for the, extension with multiples, option.
 

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Quote:
Originally Posted by yelnatsch517  /t/1469891/help-with-lms-ultra-5400-enclosure-with-practical-lfe-extension#post_23245539


I don't understand PR builds. What is the allure for these? LMS 5400 PRs cost so much, wouldn't it be more better to just stick with 2 sealed 5400 builds?

Unless of course, you are like lukeamdman and absolutely don't need anything under a certain frequency.

The allure is zero noise and compression compared to a port, along with not wasting any cabinet volume, and achieving very low tunes in relatively compact cabinets.


Value is definitely not there vs PVC pipe or a slot port. I jumped on my PRs when they were randomly on sale for 1/2 off.
 

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Quote:
Originally Posted by Mr. Neverbicker  /t/1469891/help-with-lms-ultra-5400-enclosure-with-practical-lfe-extension#post_23245692


BassThatHz, do you feel that
 

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Quote:
Originally Posted by Jay1  /t/1469891/help-with-lms-ultra-5400-enclosure-with-practical-lfe-extension#post_23245667


not wasting any cabinet volume

I wouldn't say that, per se. PR's can take up quite the space when you factor in their mounting depth and required WxH.

The other disadvantage is that they produce lots of harmonic noise from all that moving mass that is trying to move and then trying to stop, in a non-linear way. Like a piano where all the strings are just a little bit off tune, in an unpredictable way.
Quote:
Originally Posted by Mr. Neverbicker  /t/1469891/help-with-lms-ultra-5400-enclosure-with-practical-lfe-extension#post_23245692


BassThatHz, do you feel that
 

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Discussion Starter · #12 ·
Got it. As far as PR vs ported, I'm open to doing either. I'm looking into it again and I may be able to fit the port in the room without too much hassle. I'm seeing a decent compromise in tube size that wouldn't be too large or noisy when tuning this to 15 Hz.
 

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Quote:
Originally Posted by BassThatHz  /t/1469891/help-with-lms-ultra-5400-enclosure-with-practical-lfe-extension#post_23245910


I wouldn't say that, per se. PR's can take up quite the space when you factor in their mounting depth and required WxH.

The other disadvantage is that they produce lots of harmonic noise from all that moving mass that is trying to move and then trying to stop, in a non-linear way. Like a piano where all the strings are just a little bit off tune, in an unpredictable way.

Yes it can be beneficial; and Yes it is a waste of money. It is also not worth trying unless you plan on running 4 or 8 subs and 2 or 4 amps.

I could live without it on movies and be happy.

But that never stopped us from trying, regardless.

A PR is a resonating mass, which is coupled to the enclosures air spring. This is functionally the same as the air inside of a port. What is this "harmonic noise" you speak of?


The volume eating by a PR is extremely negligible compared to a large long port
 

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Discussion Starter · #17 ·
I read through much of the Master List Bass Thread and see that the vast majority of bass is above 20 Hz, with some dipping down to 15 Hz, and very few under 15 Hz. I think I should be okay with optimizing for 15 Hz+. The lighting strikes in War of the Worlds hit down to 5 Hz, although the sound ranges well above 20 Hz, so there'd still be plenty impact I would think.
 

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Quote:
Originally Posted by Mr. Neverbicker  /t/1469891/help-with-lms-ultra-5400-enclosure-with-practical-lfe-extension#post_23250165


I read through much of the Master List Bass Thread and see that the vast majority of bass is above 20 Hz, with some dipping down to 15 Hz, and very few under 15 Hz. I think I should be okay with optimizing for 15 Hz+. The lighting strikes in War of the Worlds hit down to 5 Hz, although the sound ranges well above 20 Hz, so there'd still be plenty impact I would think.

That too. Beneficial but wasteful.
Quote:
Originally Posted by Jay1  /t/1469891/help-with-lms-ultra-5400-enclosure-with-practical-lfe-extension#post_23246381


A PR is a resonating mass, which is coupled to the enclosures air spring. This is functionally the same as the air inside of a port. What is this "harmonic noise" you speak of?

The volume eating by a PR is extremely negligible compared to a large long port

Have you ever tried pulling a bowling ball with a slinky before?

What happens when you pull a snow sled with a car and slam on the brakes? The kids crash into the car at 20mph, that's what.

It's a delayed reaction of the conversion of potential energy into kinetic energy.


It's 2 lbs undergoing 100 g-forces. When the signal stops or changes frequency that energy has to go somewhere. It goes back into the woofer(s) as a modulation (distortion).


The air has far less density and viscosity and frictional forces, it's more lossy, and thus damps faster than a moving-mass does.


It's easier to stop 100 Newton's of Air, than 100 Newton's of Lead, because the air will bend and deflect and give way. The lead won't. That's why shotguns shoot lead, not air.
 

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Discussion Starter · #20 ·
The PRs moving mass dampening is adjusted to be equivalent to the air compression dampening of a vent. I've read a lot that group delay is indicative of SQ, namely transient response, which doesn't vary according to vent vs PR.


Also, something about the AE PRs makes them more capable of lower frequency SPL than the VMPs, and they each consume just 0.05 cubic feet. However, PRs are still limited by excursion, whereas ports are not. Even with 3 PRs, there is still a portion of the max SPL clipped off when compared to ported with the same volume and tuning. When I carefully optimize the tuning, enclosure size, and vent size to the smallest vent volume possible without too much air flow noise, the same PR configuration is still 25% smaller overall. But then I found, at least with the LMS Ultra, that when tuned low enough, they become equal in overall size. Eight cubic feet tuned to 15 Hz consumes a net 10.6 cubic feet when adding vent volume. Equivalent response with PRs requires 3 PRs with the same net 10.6 volume, and would still have some of the response clipped due to PR excursion. So I'm probably just going to go ported with 8 cubic feet tuned to 15 Hz. Keep in mind, I'm carefully minimizing the port volume by keeping the air flow around 20 m/s at [email protected], and around 35 m/s at [email protected], assuming the higher air speed would still remain inaudible when the sub is hitting louder.
 
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