New Mal-X 2 PR Build - Need Help

[Kevin Haskins]

vili wrote:

You are right, no double on those areas. The cabinet doesn't flex or anything so there are no worries there. You basically want as big of a cabinet as possible and doubling up those areas takes up extra space that doesn't really do a whole lot. I like the flushed look of the drivers. Mind you if you use the provided rubber gasket that the surround still sticks out from the front of the enclosure using .75" mdf even with the double baffle. It doesn't bother me, but you may/may not want to use the rubber gasket depending on the look you want.

What are the details of your build Vilii? Size box, mass used on PRs, how much fill? Also, what are you using for power and EQ?

Kevin Haskins
Exodus Audio

[vili]

I have a 26" cube. Should be about 7.5 cubic feet inernally after bracing and drivers. I used all 14 washers which should put me between 1750-1800g mass. I originally had about 6-7 pounds of fill, but I just took half of it out to do a test. It seems to give me 1-2 more dbs, but it has sharper nulls/peaks just a bit, it drops off just a tad sharper as well.

Using a crown xs1200 bridged 4ohm mono to power the mael, run in series. Puts out 3kw. Using SMS-1 for EQ.

[Kevin Haskins]

vili wrote:

I have a 26" cube. Should be about 7.5 cubic feet inernally after bracing and drivers. I used all 14 washers which should put me between 1750-1800g mass. I originally had about 6-7 pounds of fill, but I just took half of it out to do a test. It seems to give me 1-2 more dbs, but it has sharper nulls/peaks just a bit, it drops off just a tad sharper as well.

Using a crown xs1200 bridged 4ohm mono to power the mael, run in series. Puts out 3kw. Using SMS-1 for EQ.

Pull all the fill out. You don't need it. It is just eating up output. I'd also experiment with less mass. I prefer tuning them around 18Hz which will give you more output where you need it most. Aim for around 1200-1300g per PR.

Kevin Haskins
Exodus Audio

[vili]

Thanks Kevin, I will try that.

[altahometheatre]

vili wrote:

You are right, no double on those areas. The cabinet doesn't flex or anything so there are no worries there. You basically want as big of a cabinet as possible and doubling up those areas takes up extra space that doesn't really do a whole lot. I like the flushed look of the drivers. Mind you if you use the provided rubber gasket that the surround still sticks out from the front of the enclosure using .75" mdf even with the double baffle. It doesn't bother me, but you may/may not want to use the rubber gasket depending on the look you want.

Thanks Vili,

Does everyone else agree? Should I not double up the top, bottom, and back. This will add a little extra volume. I would add a brace to keep rigid.

I was also going to use biscuit joints for added strenght. Is this a good or bad idea? I think the only thing bad may be small voids in the wood if glue does not fill them.

Are people using a special MDF glue or will any good wood glue work?

Thanks
Darryl

[vili]

You are fine without the double sides. There is no reason to double the mdf unless you want to flush mount it. I'm not much of a woodworker, all we did was cut the mdf, glue/clamp together and put a couple of headless nails in a couple of parts of it.

No special mdf glue here, just regular woodworkers glue.

Have you decided if you are going to use a speakon connector or regular binding posts?

[altahometheatre]

I have not decided. I know that you went back and forth on the connectors. Are you happy with your selection?

I will be ordering something shortly. If I buy Amp / Filter / Connections etc from US, I would like to combine into as few orders as possible.

I will post a new plan shortly without doubling some of the walls.

Darryl

[altahometheatre]

Attached is a sketch using only single walls on top, bottom, and back. Does the bracing look like it is where it belongs?

The external dimensions are the same but the new internal dimensions are:
23.5 x 24.25 x 26 = 8.57ft3 - .55 (for sub and PRs) - .13 (bracing) = 7.89 ft3

I calculated 7.28ft3 on my original drawings.

If there is no need for the extra double walls, then I think it makes sense to go with slightly bigger volume.

[Mike P.]

It wouldn't hurt to add two more strips between the PR's, one on the top and one on the bottom.

[altahometheatre]

Mike P. wrote:

It wouldn't hurt to add two more strips between the PR's, one on the top and one on the bottom.

Does that look better? The bracing strips are 2.5" high.
Could anyone tell me where is the most bracing required? I could strengthen in that direction if required.

Thanks for your input.
Darryl

[vili]

To be honest, I don't really see a need for that much bracing. I just have the one going vertical and two going horizontal, one at the top and one at the bottom. I guess more bracing never hurt anyone, but it takes up volume in the box and especially doing that crossbracing is going to be a pain to put together.

[Mike P.]

As long as the pieces are cut accurately to fit, cross bracing is easy. Wood glue on each end and your done.

[Warpdrv]

Not sure you have many more options to add any more bracing, I like your last pic and it should be more then plenty.... the box looks great IMO....

[altahometheatre]

I have the wood cut and have started to put this thing together. I thought I would post some build pictures. Not because I am an expert - but because I enjoyed looking at the various builds when I was attempting to get the courage to build my own.

The first picture is my second mistake. My first mistake was writing down the wrong dimensions before I got the MDF cut. Luckily my error was to the good side.

I noticed this second error when dry fitting all the lumber. As you can see the two side pieces are of different lengths.



I could not figure out how this could happen since I carefully drew this up in Sketchup. When I pulled the bottom panel off I could see the error.



When I inserted the side panels, I pushed them into the bottom panel for 1/4 inch. Everything looked correct in the drawing, but when I exploded the panels out and took dimensions, I was 1/4 inch too long on the side dimensions. You can see in the picture that the bracing was located on the top of the bottom panel, but 1/4 inch higher than the sides. In sketchup it is important to remember that you can push pieces into each other. Hopefully this will help others not make the same mistake.

Darryl

[altahometheatre]

Here are some more pictures of the dry fitting of the materials.

One negative about this build is that it is NOT an efficient use of MDF. This build took three sheets of MDF due to size of the panels. A more efficient design this that by SturnMD which is only slightly smaller and used only two MDF sheets. MDF is cheap so I decided to go slightly larger and spend the extra $26.

The first one shows circles cut on the inside panel, but not on the outside.


This one is a better picture of the error I discussed in previous post.


Still without the outside holes cut. Still just dry fit.


All the holes are cut. PR inserted to check the fit.

[altahometheatre]

I tried to by a circle jig for my router but it did not fit. I made my own and it worked very well. If you do not plan on cutting many circles, I would recommend making your own.

Here are some pictures.





I simply used a old piece of plexiglass and mounted it to the bottom of my router. From the edge of the bit I did my radius measurement and drilled a hole. I used the drill bit to rotate the jig around. It made a very accurate circle cut.

Regard Darryl

[altahometheatre]

Here is the final "dry fit" picture.

After I dry fit everything, I marked for the biscuits. This picture shows the final dry fit with all the biscuits in place.

I put four biscuits along every edge.


Tomorrow I start with glue. Reminds me I had better figure out which connectors and order them soon. Then I have to get back to amplification and filters.

Darryl

[vili]

Looks great!

[altahometheatre]

Warpdrv wrote:

Here is one for sale... http://forums.audioholics.com/forums...ad.php?t=55569 Chopin Guy is a standup guy...

Thanks Warpdrv,

I purchased the SMS-1 from ChopinGuy. I have not received it yet, but should be here in the next couple of days.

More expensive than some of the alternatives (Reckhorn or eQ.2) but should be fun to play with.

Darryl

[Kevin Haskins]

altahometheatre wrote:

Thanks Warpdrv,

I purchased the SMS-1 from ChopinGuy. I have not received it yet, but should be here in the next couple of days.

More expensive than some of the alternatives (Reckhorn or eQ.2) but should be fun to play with.

Darryl

Once you set it up in-room you won't regret spending the extra money. The real value of the SMS-1 is the ability to easily take a measurement and view the response without the complexity of figuring out how to take measurements, buying the equipment and then going through the process. It just simplifies the process having all the tools in one device.

Here is a helpful hint. Use it to optimize room placement too. If you have a couple choices on where the sub gets placed, use the SMS-1 to measure those locations and pick the one that requires the least amount of EQ. The EQ is just a band-aid for some of the room problems. Your always best off picking the best room location.

Second helpful hint. You can do the same thing with your main speakers. You won't leave the SMS-1 attached to them but if you have a couple different setup locations, the measurements can help you pick the best location (at least for bass) for the main speakers. Be careful using a high output test signal into the speakers. The drivers may not care for lots of LF information below their tuning frequency (if they are ported). I'd be at the ready to terminate the test via shutting down the amplifier just to be safe.

Kevin Haskins
Exodus Audio

[altahometheatre]

Thanks for the pointers Kevin,
I have not finished the Mal-X build yet but I did start playing around with the SMS-1 last night with my current subs. I have a lot to learn how to set it up and use it.

I spent a few hours trying to get the video to work properly. I never could get a picture with the composite video connection. With S-Video, I get the picture doubled up on the screen. There is some overlap in the double-up making part of the screen very difficult to read.

Has anyone else seen this issue before? I am sending the video through to my Anthem D2 (pre) and from there to an JVC RS-1 (through HDMI).

I am going to do some searching to see if I can find a solution.

Darryl

[altahometheatre]

I found this on the velodyne site.

Digital Drive Service Bulletin

Problem: Loss of video on Digital Drive products.

Solution: Many new receivers and AV processors support HDMI connectivity and can up-convert legacy source material to true high definition 1080i/p output. If you're having difficulty currently seeing the video from your Digital Drive product, go into the receiver's setup menu and select a lower output resolution. You may also find that it's helpful to utilize a composite to S-video adaptor to help in this process and go into your receiver using the S-video input. Doing so will eliminate one step in the video processing chain.

I already tried the lowest output resolution. Must be something to do with the scaler in the D2. I will try some other options such as going directly to the projector.

Darryl

[Kevin Haskins]

Unplug every other video source from your TV and just run the Velodyne direct in the monitor. You only need it connected to get everything set up so there really is no reason to leave it connected to your video source once everything is calibrated.

Kevin Haskins

[altahometheatre]

Thanks Kevin,

Thats a good idea. I will give it a try tonight.
Still working on the Mal-X box. Doing some of the final bracing. I will post some more pictures soon.

Darryl

[altahometheatre]

I have finally finished the Mal-X sub. I can say it has been amazing addition and filled the room with lots of powerful bass. I will post some final pictures later.

I have watched a few movies with spectacular results (ie Batman Returns & Master and Commander on bluray). Today I thought I would throw in War of the Worlds (DVD). The beginning scenes were great (lighting / pod emerging). I watched the clipping light (EP4000) to make sure no issues. I also set sound meter to catch maximum sound pressure (109 db). All was going great until the scene when pod first begins shooting. The sub made some sort of odd sound, like maybe at end of excursion???? Not sure what it was but sounded more mechanical than sound that should have been from movie. The sound lasts a few seconds and will occur at couple of times during that scenes when everyone is running away and the pod is shooting up the city. The subwoofer is moving in and out, but does not appear to be anything crazy like the videos that Kevin has put up.

Thinking that this might harm the sub, I started playing with SMS to see if I could change something to stop the sound. I raised the filter, changed the slope, used a flat curve, but nothing except lowering the volume on sms would remove the noise.

I have a couple of questions:
1) Although I did terrible job of attempting to describe this sound, is it maybe normal at this point in movie?
2) Is this damaging to sub?

I played Batman/Master at similar levels of volume and did not have any issues. I would hate to lower volume on sub just because of this one movie.

Thanks
Darryl