Maelstrom-x 21" 15cu Sealed Build! - Page 8 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #71 of 225 Old 11-21-09, 01:30 PM Thread Starter
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Re: Maelstrom-x 21" 15cu Sealed Build!

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SteveCallas wrote: View Post
A few posts back you said that sliding the baffle into place caused the cone to puff out slightly. You don't want that to happen. With a sealed sub, heat will build up inside the enclosure, and heat causes air to expand - now you will have even more pressure inside the enclosure pushing against the cone. That can mess up the suspension over time.

The trick a lot of people use to counteract this is to place a small pin hole somewhere near the top of the enclosure. This will prevent a buildup of pressure in the sub over time, but should be small enough as to not lose pressure from the backwave while the sub is in use. Someone who uses sealed subs and such a method may want to chime in to give him exact details, as I've never actually done it myself.

As for mechanically exciting the whole room, in my opinion, that the best part I used to have one of my subs in a 3rd floor apartment and it would cause my whole floor to bounce. Now I have two such subs in a one floor townhouse over a concrete foundation and the effect just isn't as good without feeling the ripples of bass run through the floor. The floor still imparts some bass energy, but not nearly to the same level as the wooden floating floor did. In real life, if there is a big explosion, you will feel it through the ground - therefore, a sub that mechanically excites the floor offers a more accurate respresentation of that explosion.

Wow Steve, I've never heard of that before! Great tip! Hopefully someone else can chime in with some specifics as to how that pinhole thing is done.


I do enjoy the floor vibrating, true, but the folded horn did it in such a way that blended with the sound. This sealed box seems...separate from the sound. I'm not sure how to describe it. My fiance noticed it as well, but she's not terribly articulate when it comes to describing audio. I'm hoping tuning everything with Audyssey will help this some. Maybe I'm just being oversensitive.

Last edited by Lonely Raven; 11-21-09 at 02:21 PM.
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post #72 of 225 Old 11-21-09, 01:30 PM
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Re: Maelstrom-x 21" 15cu Sealed Build!

I agree with Steve. Your horn can't mechanically excite the whole room and create the tactile effect present in movies. Looking forward to your impressions after watching Star Trek.




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post #73 of 225 Old 11-21-09, 02:23 PM
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Re: Maelstrom-x 21" 15cu Sealed Build!

Looking back at your first thread on the idea of a LLT to replace your horn, it struck me that you probably haven't been exposed to the reproduction of low frequencies. This was your FR at the seat:



Your new subwoofer will not die below 40hz like the horn. And what do you know, below 40hz is where things will start to transition from audible to tactile at most listening levels. Welcome to the new world.

Also, your horn subwoofer was being used pretty hot for the range that it coud play - the large peak ~45hz probably made the bass essentially one-noted. You may not have noticed it then, and you still may not notice it now, but live with your new sub for a couple months, then listen to a sub with a large peak like that horn again, and you will definitely notice it.


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post #74 of 225 Old 11-21-09, 03:44 PM
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Re: Maelstrom-x 21" 15cu Sealed Build!

great build,, cant wait for the final pics
i want one
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post #75 of 225 Old 11-21-09, 04:01 PM Thread Starter
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Re: Maelstrom-x 21" 15cu Sealed Build!

Steve, I know your dead on. I worked on that big hump with a super-duper-chunk, and some smaller OC703 corner traps around the room. I think I knocked it down a few db, but I don't have those measurements anymore. I realized I've rebuilt the computer I ran this on and didn't save any of the measurements. So it wasn't quite one note, but I had heavy coverage from 30-50.

Playing with the Mal-21 I'm seeing some pretty solid response covering 30Hz down to 15Hz with a dip at 17Hz (at least so say my senses doing a slow sweep). As I said, I'll do some proper measurements later. I just finished running Audyssey which seems to have helped blend everything better.

I appreciate the second set of eyes looking at this and helping my perception.

EDIT: I was just listening/watching a video that has some sweeps and shows you what freq the sweep is at, and I think I still have a bump around 45Hz. I'll know more once I find where I stashed my Mic and Mixing Board.

Last edited by Lonely Raven; 11-21-09 at 04:22 PM.
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post #76 of 225 Old 11-21-09, 04:04 PM Thread Starter
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Re: Maelstrom-x 21" 15cu Sealed Build!

Funny thing about running Audyssey, since putting diffusers on my back wall, Audyssey went from thinking my surround speakers were 6.5 feet (which is accurate) to thinking they were 12' 13'!

I guess that means the diffusers are working some!
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post #77 of 225 Old 11-21-09, 06:17 PM
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Re: Maelstrom-x 21" 15cu Sealed Build!

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Funny thing about running Audyssey, since putting diffusers on my back wall, Audyssey went from thinking my surround speakers were 6.5 feet (which is accurate) to thinking they were 12' 13'!

I guess that means the diffusers are working some!

Steve pretty much nailed it. The sealed sub is coupling to the air just fine, it is doing it significantly lower in frequency that your horn. What most people think of as bass is >40Hz, so your horn sub did fine and dandy for that kind of bandwidth. It won't reproduce 20Hz with any authority, but for music and the upper frequency stuff, a horn can be downright impressive. It just won't plumb the depths the same as a big sealed box driver.

This is my favorite subwoofer horn build.

http://www.royaldevice.com/custom.ht...20TOTAL%20HORN


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post #78 of 225 Old 11-21-09, 06:19 PM
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Re: Maelstrom-x 21" 15cu Sealed Build!

Quote:
Lonely Raven wrote: View Post
Funny thing about running Audyssey, since putting diffusers on my back wall, Audyssey went from thinking my surround speakers were 6.5 feet (which is accurate) to thinking they were 12' 13'!

I guess that means the diffusers are working some!
It could be just because those algorithms seem to have a lot to be desired. I'd manually set it all up and not trust the auto-EQ or the delay & bandwidth choice either.

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post #79 of 225 Old 11-21-09, 08:09 PM
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Re: Maelstrom-x 21" 15cu Sealed Build!

Yeah, I'm not a fan of those auto setup and EQ systems. They get it wrong more often than right, and they tend to roll off your highs and lows for some reason. Setting things up manually shouldn't take but a few minutes. Setting the subwoofer distance will take a bit longer, but you'll want RoomEQ up and running before you try to dial that in.


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post #80 of 225 Old 11-22-09, 01:48 AM Thread Starter
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Re: Maelstrom-x 21" 15cu Sealed Build!

Yeah, Audyssey did a good job of blending the timing of all the speakers, but it goofed up the crossover points and did something to the center channel that dropped the dialog a bit.

Everyone loved the sound with the new sub...the general comment after watching Star Trek tonight was that the impact made them feel like things were actually moving past them. The most notable was the scene where Nero drops the "Red Matter" down the hole drilled into Vulcan, and the device drops past Kirk and Sulu who are on the laser drill. The surround and sub combined really made it feel like something just flew through the room! AWESOME!

So yes, I think this setup is better for the investment of time and $$. It's making me reconsider my choice of main speakers, and reminding me that I need more sound treatments in the room...
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