DIY Subwoofer Risers

[Big Daddy]

Originally Posted by ShockWave

Wow, great great job guys on those risers!! I will be making two new ones shortly myself! Thanks Bid D for sharing this info, I have learned a lot from people here. What exactly is a subtrap?

Check the bottom of post #1. You can click on the links and read about SubTraps.

[progers13]

Originally Posted by ShockWave

Wow, great great job guys on those risers!! I will be making two new ones shortly myself! Thanks Bid D for sharing this info, I have learned a lot from people here. What exactly is a subtrap?

Nice setup! Go GATORS!!!

[ShockWave]

Thanks Big, is there a different application for each the riser and the trap?



Thanks Progers!!! Go Gators!

[4x12]

Originally Posted by dancel

I did try the turntable coffin and it made no difference.. so i went down my basement and put this together.. not done yet of course I still need the foam.



what you guys think?

looks good... I would pull a few more mods on it.

1) Get some undercarpet foam from home depot and some 3m adhesive spray glue.
2) Put a full piece of that foam on the top part of the riser, put some between the board and legs and under the feet. This will offer a better decoupling from the sub>riser>floor.
3) Add carpet.

And your set!!

[kareface]

Originally Posted by ShockWave

Thanks Big, is there a different application for each the riser and the trap?

A riser only serves to reduce unwanted sympathetic vibrations via. isolation, where a trap will try and reduce excessive LF energy (usually in relation to the vertical node) and is usually built to offer some isolation as well. The risers I built are more akin to a sub trap rather then a isolation platform. They take a lot more effort but the advantage is lower reverberation time in the spectrum produced by the sub, which is the most important range to reduce your reverb time in. The potential disadvantage is raising the sub will likely require you to reposition them. I had to play around with sweeps for hours trying to find the best position available. My side positions didn't cut it anymore.

[dancel]

Originally Posted by 4x12

looks good... I would pull a few more mods on it.

1) Get some undercarpet foam from home depot and some 3m adhesive spray glue.
2) Put a full piece of that foam on the top part of the riser, put some between the board and legs and under the feet. This will offer a better decoupling from the sub>riser>floor.
3) Add carpet.

And your set!!

Yea, this is not finish yet i will be adding the foams, above and at the bottom , but what do you mean with putting one under the feet?

[4x12]

Originally Posted by dancel

Yea, this is not finish yet i will be adding the foams, above and at the bottom , but what do you mean with putting one under the feet?

Isolating the legs from the floor...

[dancel]

Originally Posted by 4x12

Isolating the legs from the floor...

Oh ok!! thanks

[elninoloco7]

It took me about a year to finally get my subs perfectly (one in front of the room in one corner the other in the opposite back corner both subs are the same...JBL 400watt rms front firing subs) SEE MY IMAGE GALLERY FOR PICS....Today i raised it about 2 feet off the ground just for the heck of it..and to be honest didn't notice a difference....am i doing something wrong? or does this rising thing only work on some subs? (just fyi...my subs sound fantastic where they are placed now without risers...but just wanted to test..to get the maximum potential, assuming i haven't reached it already)

[Big Daddy]

Originally Posted by elninoloco7

It took me about a year to finally get my subs perfectly (one in front of the room in one corner the other in the opposite back corner both subs are the same...JBL 400watt rms front firing subs) SEE MY IMAGE GALLERY FOR PICS....Today i raised it about 2 feet off the ground just for the heck of it..and to be honest didn't notice a difference....am i doing something wrong? or does this rising thing only work on some subs? (just fyi...my subs sound fantastic where they are placed now without risers...but just wanted to test..to get the maximum potential, assuming i haven't reached it already)

Congratulations on your home theater setup. From the pictures in your gallery, it appears that your front speakers are too far apart. Also, your subwoofers may not be in the right place and they are also too close to the side walls. If you don't mind, I will make a few suggestions to improve the sound quality in your home theaters.

FRONT SPEAKERS SETUP

For front speakers, put the speakers at least 1-2 feet or more away from the front wall.

• The distance between the two speakers should be between 6 to 10 feet.
• The distance between your main listening chair and the distance between the two speakers should be approximately the same. They should form approximately an equilateral triangle.

• The tweeters should be about the same level as your ears when you are seated. For smaller speakers, use a stand. Slight tilting backward or forward of the speakers until the tweeters point toward your head may also work.
• You can slightly angle (toe-in) the speakers toward the listening chair. You can use a string to make sure both speakers are angled exactly the same. Angling the speakers too much may have two disadvantages:
  1. It may ruin the sound stage.
  2. It will not be very effective for others who may be sitting elsewhere in the room. Don't be selfish.

Play a CD with good soundstaging and a singer in the middle.

• If the soundstage is good and wide but the center stage is blurred, move the speakers closer together.
• If the center stage is focused and sounds great, but the soundstage isn't very wide, angle the speakers away from the listening position a little at a time until the soundstage becomes wider without losing the center stage.
• Many speakers may sound better if they are pointed at your shoulders rather than directly at your head.
• Always use a string to make sure both speakers are angled the same way.
• Don't be afraid to experiment. Rooms are not the same and interaction with room boundaries, furniture, carpets, etc. play an important role in the sound that you hear.
• Many experts believe that in a small home theater room, you hear the room and not the speakers.

As far as the two subwoofers are concenred, follow the diagrams below and change their positions in the room. Also, keep them about a foot away from the side walls.

The low frequency waves generated by subwoofers have very long wavelengths and create standing waves or room modes. The strongest modes are horizontal and vertical axial modes. When you move the subwoofers around the room for optimum placement, you are dealing with horizontal axial mode. A riser deals with vertical axial mode. In most cases, a riser helps with a subwoofer's performance, but the position in the room and the shape of the room its contents play a role. You must be willing to experiment for the most optimum horizontal and vertical positioning of the subwoofers in the room.

DIFFERENT OPTIONS FOR PLACEMENT OF MULTIPLE SUBWOOFERS

[elninoloco7]

I tried all of these set-ups (the images below are kind of sort of to scale....gives u a good idea of my room anyhow)
PLEASE NOTE THAT THE (REAR SPEAKERS HAVE BEEN CORRECTED AND SWAPPED) and the RED IS A CURTAIN NOT A WALL.

THIS ONE FAIL

TOO MUCH BASS IN ONE END OF THE SEATS and NO BASS FELT AT THE OTHER SIDE

BASS was EVEN but WASN'T happy with results

WAY BACK AS I WAS BUILDING THE THEATER

[Big Daddy]

Originally Posted by elninoloco7

TOO MUCH BASS IN ONE END OF THE SEATS and NO BASS FELT AT THE OTHER SIDE

Everytime you change the position of the subwoofers, you need to adjust their levels independently so that one subwoofer does not overpower the other one. You may also have to run the built-in calibration program inside your receiver before you sit down and test the results.

I have a included a set of instructions in the middle of https://forum.blu-ray.com/subwoofers...anagement.html thread on how to calibrate multiple subwoofers in the room. As a general rule, the calibration of two or four subwoofers consist of three steps:

1. Placement.
2. Adjusting the level of each subwoofer independently by turning the other subs in the room off.
3. Turning all of them on and calibrating all the subwoofers together and making sure the combined level of the subwoofers is approximately equal to the rest of the speakers.

[elninoloco7]

So i moved the fronts closer they are exactly 80 inches away from me...and 10 feet apart (any closer and it will be in-front of the screen...they are now 1.5 feet away from wall (well one is the other the wall is a longs way back there)..as far as sub i placed it 1.5 feet away from the back wall and from the side wall...i'm going to try the placement the way it is now....because i am satisfied with the results....So do i the angle the fronts a little bit?..or should i not angle it at all? ..by the way..i am recalibrating the system as well....as far as my rears go..they are perfectly that one took forever to find the sweet spot as far as height and angle..but finally got my rears well i can hear all of them from virtually any seat.

[Big Daddy]

Originally Posted by elninoloco7

So i moved the fronts closer they are exactly 80 inches away from me...and 10 feet apart (any closer and it will be in-front of the screen...they are now 1.5 feet away from wall (well one is the other the wall is a longs way back there)..as far as sub i placed it 1.5 feet away from the back wall and from the side wall...i'm going to try the placement the way it is now....because i am satisfied with the results....So do i the angle the fronts a little bit?..or should i not angle it at all? ..by the way..i am recalibrating the system as well....as far as my rears go..they are perfectly that one took forever to find the sweet spot as far as height and angle..but finally got my rears well i can hear all of them from virtually any seat.

Don't angle them too much. Let them fire into the room as opposed to your head.

[ShockWave]

Thanks. What is a good test to tell if I would actually need a subtrap?

Originally Posted by kareface

A riser only serves to reduce unwanted sympathetic vibrations via. isolation, where a trap will try and reduce excessive LF energy (usually in relation to the vertical node) and is usually built to offer some isolation as well. The risers I built are more akin to a sub trap rather then a isolation platform. They take a lot more effort but the advantage is lower reverberation time in the spectrum produced by the sub, which is the most important range to reduce your reverb time in. The potential disadvantage is raising the sub will likely require you to reposition them. I had to play around with sweeps for hours trying to find the best position available. My side positions didn't cut it anymore.

[Big Daddy]

Originally Posted by ShockWave

Thanks. What is a good test to tell if I would actually need a subtrap?

Do you have a small table or a sturdy wooden box in your house? Stuff a couple of pillows under it and put your subwoofer on top it. Expeiment with its position and see if you get an improvement in its performance.

[ShockWave]

Thanks Big. Hey how do you use string to balance the angle of the speakers? Also, I need to use a 35 foot xlr for on of my subs because have to run it in a wall. The other would need 15 foot. Should I just get the same lenghts?

[Big Daddy]

Originally Posted by ShockWave

Thanks Big. Hey how do you use string to balance the angle of the speakers? Also, I need to use a 35 foot xlr for on of my subs because have to run it in a wall. The other would need 15 foot. Should I just get the same lenghts?

Cut two equal peieces of string and attach them to the middle front baffle of your speakers. Attach the other end of the strings exactly to the middle of your main listening chair. Adjust the positions of the speakers and the chair until the two strings are streched exactly the same and equally. The angles will be automatically the same. Remember that it is not rocket science and use your eyes and common sense.

Yes, you can get the same length XLR cables and hide the extra length inside the walls. Because you are adjusting the level of each sub independently, the difference in length is not a big factor. If you are using RCA to XLR cables, I highly recommend the Samson S-Convert. You can buy one from Sweetwater for $50 + Free Shipping. The S-Convert has two channels and will accomodate both subwoofers.

[ShockWave]

Thanks Big. Just curious, what should I listen for when moving my subs around? Can it be measured, or is this just a preference test? Not trying to be a jerk just curious how it should be done.

[Big Daddy]

Originally Posted by ShockWave

Thanks Big. Just curious, what should I listen for when moving my subs around? Can it be measured, or is this just a preference test? Not trying to be a jerk just curious how it should be done.

Usually, when you move a subwoofer around, you will hear a difference in sound output. Use your ears or an SPL meter.

In the case of two subwoofers, put them in the middle of the side walls about a foot away from the walls. Set the gain in the receiver to zero. Turn one off and adjust the level of the one on its back so that you get approximately 73-74dB on your SPL meter. Do the same for the other subwoofer by turning the first one off. After you are sure that their levels are approximately the same, do not adjust their levels on their backs anymore. Now, turn both of them on and adjust the total level of both in the receiver so that the combined level of the subwoofers is equal to the rest of the speakers.

For alternative placement of two subwoofers, follow the diagrams I included a few post ago (post #1310).