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Discussion Starter · #1 ·
Hi there,

Can you stuff a ported box like a sealed box to make it think its in a bigger enclosure.

If you can it may well change what I do as regards to two ported instead of two sealed as I need to get my box bigger ported to get a better result but it all depends on stuffing. Also if it does will it increase it about 20-25% like a sealed box.

cheers

Graham
 

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Discussion Starter · #3 ·
Mike,

Thanks for the reply. I still keep humming and harring with the slot ported design. I have designed a 8 cu ft box but need it to be 9.5 as 8 cu ft is the biggest I can get in. I will be building two of these. At the moment it will be tuned to 16hz with the 1st port resonance at 150hz with a slot port of 110cm long. The only issue I am worried about is that the port velocity will be 32 m/s max at 10hz with no high pass filter. I remembered you saying for 15hz and over you wont need one aslong as you crossover at 80hz.

If I added the fiber fill to get 9.5 cu ft how much would it lower the tune and decrease output. Should I be concerned about the 32 m/s port velocity.

cheers

Graham
 

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Discussion Starter · #9 ·
Mike,

So do you think there is alot more to gain between the ported and sealed. What about films like transformers 2 etc.... Will watching movies like that become an issue. If I apply a high pass filter it brings the spl level down a fair bit.

cheers

Graham
 

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Discussion Starter · #11 ·
Mike,

What happens if the 1st port resonance was lower than 120 hz say 50 - 80hz.

Bassotronics - I love you. Doesn't that play 8hz.

cheers

graham
 

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What happens if the 1st port resonance was lower than 120 hz say 50 - 80hz.
Any lower then 120 hz when using a 80 hz crossover and you'll start hearing it.

Bassotronics - I love you. Doesn't that play 8hz.
I have no idea what frequencies are on that song.




 

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I'd stick with sealed on these subs a ported design doesn't really look like a big advantage.

Also your slot port diameters are overly skewed. You'd be better off with a more squarish port. Remember a square port works as a brace if you build it right!

Still I see no reason to port this sub. Just use an eq to shape out the response you want in a sealed box.

110 db at 20hz in a sealed box is plenty of headroom. Especially if you got dual subs.
 

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Discussion Starter · #14 ·
Mike,

8hz in places mate. I love low low bass which is why I am concerned. The dual sealed sub will play a 10hz frequency without any excursion issues. Not sure how a single sealed sub would cope as there is more excursion than a dual. I ideally need to be in that same situation but need a cleaner bass which is why I thought about changing to two single sealed subs which would give a qtc of 0.83 instead of 0.97.

What do you think.

cheers

Graham
 

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Discussion Starter · #15 ·
lsiberian

Thanks for the reply mate. I did find it hard to model the FI's as ported subs without making a squiggle in the curve. The maelstroms model like a piece of cake and give much more output then the Q's. I just got a quote on the 18 and 21 maelstroms and they quoted me £500 for the 18 and £700 for the 21 driver.

Being in the UK it could be a nightmare trying to sell my drivers and after paying £700 for them, what would I see back. Not sure.

I like the idea of two subs but hope that I get more output than a single sub. I was getting 102db at 10hz and 114db at 20hz (according to winisd) with my dual. On the single I did in winisd you will see that the max excursion just goes over the max. Not sure if this is something to be concerned about. I have the FI's with the BP power upgrade which apparently gives them a bit more power.

cheers

Graham
 

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Discussion Starter · #17 ·
Mike,

The curve looks smoother and gives about 2.5db over the dual. I did try taking one of the drivers out of my dual box and blocked up one of the holes. The bass was defo more there but I found the midbass a bit lacking compared to the dual. It did sound cleaner though so I want something in between. I can't fit a 20 cu ft dual in which is why I thought about two subs. If they don't work out in either corners, I can lay them on their side on top of the other one where it is now so they are in the same place.

cheers

Graham
 

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Mike,

8hz in places mate. I love low low bass which is why I am concerned. The dual sealed sub will play a 10hz frequency without any excursion issues. Not sure how a single sealed sub would cope as there is more excursion than a dual. I ideally need to be in that same situation but need a cleaner bass which is why I thought about changing to two single sealed subs which would give a qtc of 0.83 instead of 0.97.

What do you think.

cheers

Graham
Going ported is not a good solution for 10hz bass. Your driver needs the reinforcement of the box to prevent over excursion. If you use a Behringer Feedback Destroyer or Behringer DCX2496 you can shape the response you want using parametric eq's. This is a much better solution than totally redoing your subs. You also need to treat the room. Often times bad bass is the result of poor subwoofer placement. Even the commercial boom-boxes sound impressive when well placed in conjunction with the seating. If your sub lacks power it's time to do a crawl test, check all the connections, and the simple stuff. Your order of fixing this should be

1. A placement crawl test
2. A check of all connections and dials.
3. ensuring your seat isn't in a natural null for the bass you like.
4. adding a parametric eq and running REW.
5. adding room treatments to address room issues.
6. adding a sub or upgrading.(option of last resort.)

Your sub is no slouch, but it needs the right conditions to do it's best. Let's check all the conditions before we get you building another sub. Besides if you get the conditions in place you will maximize any sub you put in the room.

I realize SSF is nice, but there is very little down at 8hz and none of it is really useful in home theater. A well built sub with 20hz extension with all the parameters above correctly done can shake the house down with bass.
 

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Discussion Starter · #19 ·
Hi there,

I did EQ my dual but with dimensions of 33" wide by 22" deep by 36" high it is very limited on placement. I did get it flat to 12hz as I played various test tones and noted them down with the spl meter. One thing that was for sure was that 2 feet in front of my listening position there was a 10db increase.

Here's my layout of my living room to show you. You will see that I can put two single subs in each corners. I did have my previous PB13 sub in that corner and it was pretty good but not as good as where it is now which is why I thought two subs would be good.

The other thing is that on the left side of the sofa the sound is the best (my listening position), the seat next to the sub is and can be quite over powering as it will be I guess because it is a dual. the right side of the sofa is less bassy than the left side so I guess there is a bit of a null there and the right side seat is somewhere in between the listening position and the right side of the sofa in terms of how good it sounds.

I was hoping having a sub in the right corner would balance the bass on that side of the room or would it. I did run some measurements before but I didn't save them and the other problem is that I have disconnected my sub because one of the t nuts came out. It was a real nightmare, the fiber fill got tangled up in the screw.

Your thought please matey.

cheers

Graham
 

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Hi there,

I did EQ my dual but with dimensions of 33" wide by 22" deep by 36" high it is very limited on placement. I did get it flat to 12hz as I played various test tones and noted them down with the spl meter. One thing that was for sure was that 2 feet in front of my listening position there was a 10db increase.

Here's my layout of my living room to show you. You will see that I can put two single subs in each corners. I did have my previous PB13 sub in that corner and it was pretty good but not as good as where it is now which is why I thought two subs would be good.

The other thing is that on the left side of the sofa the sound is the best (my listening position), the seat next to the sub is and can be quite over powering as it will be I guess because it is a dual. the right side of the sofa is less bassy than the left side so I guess there is a bit of a null there and the right side seat is somewhere in between the listening position and the right side of the sofa in terms of how good it sounds.

I was hoping having a sub in the right corner would balance the bass on that side of the room or would it. I did run some measurements before but I didn't save them and the other problem is that I have disconnected my sub because one of the t nuts came out. It was a real nightmare, the fiber fill got tangled up in the screw.

Your thought please matey.

cheers

Graham
FYI stuffing doesn't increase the size of a box it only decrease the distortion introduced by the back wave. If anything it technically decreases volume.

Placement variations as small as a foot can change sound vastly. I'd suggest you try it where you can. Even the orientation can help.

Are you using a great gamma or subdude? Those will tighten up bass really well and reduce bass pollution in other rooms.
 
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