Ear or other expert diy'ers. I currently have a

[michael hurd]

You have an option to model sealed, vented, bandpass and PR boxes in WinISD. You must consider each design's pro's and con's and how they relate to your listening area. ( also the parameters of the woofer somewhat determine what sort of enclosure each is going to be good for )

[dcmo]

This is what I came up with, looks good to me but then again I am new at this. What do you think?

Driver : Exodus Maelstrom-X 18
Vas : 324.0
Qts : 0.36
Fs : 17.70
SPL : 89.00 (this is just a guess, they don't state what it is)
--
Number of drivers : 1
Box type : Vented
Box size : 434.6 l
Tuning frequency : 15.03 Hz
Vent : 2 vent(s)
16.22 in length for each
4.00 in round


Relative
Freq Gain
[Hz] [dB]
10.00 -16.50
11.00 -12.91
12.00 -9.68
13.00 -6.95
14.00 -4.89
15.00 -3.56
16.00 -2.87
17.00 -2.57
18.00 -2.47
19.00 -2.45
20.00 -2.46
21.00 -2.47
22.00 -2.47
23.00 -2.46
24.00 -2.43
25.00 -2.40
26.00 -2.35
27.00 -2.31
28.00 -2.25
29.00 -2.20
30.00 -2.14

I still have some questions though, I am sure there will be more to follow.

1) Does this need fill and if so how does one apply it? Is it glued to the walls of the cabinet? From what I've read fill increases the lower end as if it were a bigger cabinet, but I don't know if I want to do that. The models I've run show when the bottom end is raised, that the ranges from maybe 20 to 30hz are lowered which isn't to my liking.

2) Bracing. Is this for a sturdier cabinet, or for driver support, or for both of these things? How many braces should go within a cabinet and where?

3) X-Max. You said to be sure X-Max wasn't gone past. I don't really understand this. I would have thought that the source signal and the power being supplied would make this happen, but what I am getting from what you said is the cabinet size would also factor into this.

4) What kind of plywood would be the best to construct the cabinet?

5) I probably should wait on this question but it's bugging me. When applying the veneer how does one make sure the seam doesn't show where the edges of the cabinet come together.

6) They have some nice vents on Parts Express (looking at the precision port flared port tube kit), but they will have to be cut. What would be the best thing to use to make the evenest cut? How do you get the end piece glued back on securely,do I need to use some kind of wrapping as well as glue?

7) Do I need to put some kind of gasket between the driver and outer cabinet wall where the driver and cabinet join together?

Thanks again for all your help, I'm sure I will have more questions later especially as the cabinet is being built. The amp is supposed to be here Tuesday, hope the driver ships on the 9th as they have stated (it would be nice if it was earlier than that).

[michael hurd]

In a vented box there is a bit less need for fill, and most people apply a foam product to the interior of the enclosure to mask any higher frequencies being emitted through the port into the listening area. 3/4 - 1" thick convoluted foam ( say like a mattress topper ) is good.

Bracing is to keep the panels of the enclosure from generating spurrious out of band ( intended pass band ) resonances that can be measured. Whether or not they are audible, the jury is still out. I would try to keep all bracing on the light side, as overbracing requires a much larger box to start with. ( to account for the volume taken up by the bracing )

Try to keep each panel small, about 12-14 inches or so between braces. Driver support is not really necessary unless you start getting into the overkill drivers with 60 pound plus magnetic assemblies.

X-,max is a product of enclosure type, size and drive level. For example in a sealed box you will have less excursion than if you were to drive the speaker in free air with the same amount of power.

Baltic birch ply is a great material for building enclosures, but it is heavy. ( 13 plies of birch, not 7 ply *poplar core with a birch veneer on each side*) It is also sold in 5 foot by 5 foot sheets, and runs about $ 65 a sheet in my area.

Another suggestion would be to find a similar ply like apple ply ( again multiple veneers ) as they are both dimentionally very stable and smooth with no voids. They will require minimum prep for finishing, unlike a cheaper more economical plywood.

As far as veneer, there are a few fellows on this forum that have done quite a bit of it, I have not so I really can't comment on it other than to make sure that the surfaces are perfectly flat. Any slight imperfection will show through the finished veneer. IE: it will "telegraph" through. Again using baltic birch or apple ply, you have a much better chance of getting a good veneer job.

As far as construction, you can glue and screw most of the joints from the inside using glue blocks, so that there are no exposed screws except for maybe the bottom of the box. ( IE: less finishing work again )

2 4" ports are not going to be enough for a driver of this caliber, maybe a mid-level 15", but not the Maelstrom-x. Thriller Audio sells the 6 inch precision port kits, as well as a few other sources on the internet. I would consider as a minimum for this driver a single 6", and even at that you will have non-linear results at a lower drive level. This driver should really have dual 6" flared ports or a single 8" if possible.

This pushes your gross enclosure volume up and may not fit in your area, again it is all about compromise. If a single 8 or dual 6" will not fit due to length, you may also consider a single 7" Acoupower port.

As far as a gasket goes, most people don't use one, but you may consider a thin closed cell foam tape that you can apply to the enclosure at the cutout.

[dcmo]

Should the bracing connect with all four sides? Do you think two would be enough, roughly splitting the cabinet into thirds? Just what is the size and shape of this bracing as compared to the cabinet it will be mounted in?

Ports. Running the winisd, it shows these need to be 38" for 2 6's or 32" for a single 8 (I've looked around and can't even find an 8" on the net). Both these put the depth or width of the cabinet at 3' plus, I really don't care for these dimesions (I would really like to bring it in at 39H X 28D X 28W). Can I mount the ports on top? If I can't or it's not preferred it looks like I will have to go with the Acoupower, but at 115.00 that is pretty expensive for a port.

On X-Max, is there a formula that will take all the things you said into account so one doesn't build too much of a cabinet for a driver?

Thanks again Michael for all your help.

[michael hurd]

As far as the bracing you can tie all four sides together yes. However a simple piece of 1" x 2" or so glued on each face will help. I used diagonal strips of MDF glued and stapled into place in a smaller box. The ports can be either internal ( only the opening on the outside ) or external. ( think like a chimney ) It doesn't make that much difference, other than if the entire port is internal it's volume must be subtracted from the gross internal volume to get the net volume. ( as well as the volume of the rear of the woofer and magnet )

Some people have used 8" sonotube ( not exactly 8", so best to measure it exactly ) for a port. Using a router and a steady bearing and a round over bit, you can make a slight flare.

[dcmo]

I would still want the port to be internal, what I mean by being on top is the port opening would be thru the top of the cabinet with the tube extending towards the bottom instead of the front or side. This really wouldn't be preferrable either (much rather be able to see the ports in front, looks like I am leaning towards the 7" port. Anyone else make them besides Acoupower?), but to me much better than a 3' front or depth. How does one get an accurate measurement of the area the port takes internally? Do you just guestimate it and make the cabinet that much bigger? On the bracing what I am understanding from what you are saying is 2"W X 1"H X cabinet width, with 1 or more going from side 1 to side 3 and 1 or more going from side 2 to side 4.

[michael hurd]

For the frequencies involved there would not be a difference if the port is down from the top or on the same face as the driver. As far as the port you would have to calculate the volume from measuring the diameter of it. Take the diameter ( outer ) in inches, and divide by 2, times itself and then Pi. Take that and times it by the length in inches and take that product and divide it by 1728, This will give you the volume displaced by the tube. As far as what the flare on the end would displace on the inside, I would guesstimate about 1.5 times the area of the actual tube x the length of the flared portion.

You could instead make a slot ported box, a bit cheaper and a bit less bracing needed. You would also have to calculate the length of the port and add it to your net volume to get your gross enclosure volume. However once you have built it you can't modify the length of it. This requires careful calculation of the volume of port and woofer, and any bracing. If you are off on the length, it will change the tune.

[dcmo]

Received the Behringer yesterday but have a bit of a problem here. The Behringer only has TRS or balanced inputs, while all I have coming off the Pioneer or the RSW15 are RCA outputs. I've done some looking on the net, but haven't been able to find some kind of adaptor. Please tell I'm not up the creek with this amp.

Okay, I might have found something. It's called a Live Wire Dual RCA-Mini TRS Adapter, is this what I would need. What is the difference between TS and TRS, they both kind of look the same?

Now I found this one at PE, RCA Jack To 1/4" Mono Plug Adapter. Rather go with this one if this is what I will need.

Am I going in the right direction on these.

Sorry for panicking on this, this project just keeps getting bigger and bigger and I sure didn't want to have to turn around and buy a new pre-amp.

On a side note, I got the Acoupower 7" port ordered. When I talked to Carlos though, he said the modeling programs were off on the needed length. How do I go about getting it to the right length. I know I need to leave it long and cut it down bit by bit until I get to where I want to be but I have no idea what I am looking for. It is going to be tuned to 15hz with it being down right at 3db at that point. If I am running a set-up disc it should be putting out either 75 or 85 db during set-up (can't remember right off hand what the signal strength is, or maybe I select the volume level. I've always just let the Pioneer set it up). Would I have it run a 15hz signal with a volume level of one of the above (whichever one is right or whatever I pre-select), and then see how much it is down or up and adjust the port length until I was down 3db at 15hz. Anyway thanks for all your help.

[michael hurd]

TS= 1/4 mono..... TRS = 1/4" stereo. The reason there is capability for a three conductor plug is for quasi-balanced operation, which uses three wires. What you need is either a 1/4" TS to RCA adapter or a pre-made cable.

To tune the port to the right frequency play test tones. ( make sure that all other speakers are disconnected from you pioneer reciever.... as they don't like to reproduce low bass without blowing up )

You need test tones that have a 1 hz increment. Play them sucessively ( at low volume ) and note where the cone almost stops moving. Make sure the volume is not cranked in the pioneer. You will need to have the gain turned all the way up on the Behringer EP2500, as the Pioneer puts out low voltage in the pre-amps.

When you shorten the port, it raises the tune of the box. Making it longer will lower the tune. Keep playing test tones and repeat to get close to your simulation. Don't sweat a 2-3 hz difference in actual vs simulation.

[dcmo]

I'm getting ready to order the Art Cleanbox and have a few questions about it, as well as a couple of other things. Sorry for being such a pain, I really am grateful for all your help.

1) If the voltage is low going to the sub, shouldn't I have something going to the other seven speakers in my set-up?

2) When doing the port length does the cleanbox need to be connected? I would think not but this is all new to me and I could easily be wrong on my thinking.

3) Setting the gain level.The pdf file says to set the level control to the best signal strength and clarity, what am I looking for here?

You've been a big help Michael, couldn't have done this without you. If you ever have any plans to come to the Kansas City area just let me know and I will have to at the very least fix one heck of a meal for you.

[CECAA850]

I've read somewhere that the Cleanbox rolls off lower frequencies, you may want to read up on it. There may be a mod to alter it, or ART may have fixed it by now, I don't know.

[CECAA850]

As a side note, I have the EP-2500 and used an adapter like Michael referred to, works fine and is a heck of a lot cheaper than the ART.

[dcmo]

I must be blind, but I can't find where he said an adapter would help with low voltage coming off the Pioneer. There is a mod for the cleanbox, already removed my question concerning it from my last post. I think I am going to see how the sub functions without the cleanbox at first. There is a lot I don't know about this (learning though), but when checking out the cleanbox it talked about increasing the gain (which I would assume is another way to say volume). If this indeed the case I know that my RSW15 was always set down about - 2db (with a setting at 12 on the sub) as compared to the front speakers (RF-7's) while being further away than them so I wonder if I need any increase in volume (again assuming that gain and volume are the same). Michael knows what he is talking about, but I have no idea what role voltage plays into this or how.

I'm still not sure what he was talking about when it came to bracing. He said to glue a 1" X 2" to each face (assume that means each side of the cabinet). Is this to mount a brace on or this the brace itself? If this is the brace which one gets glued down, the 1" or the 2" (if this is a mount I would think it would be the 2" side).

There is much I still don't know, but the cabinet will be swinging into gear very soon (the driver is supposed to ship next week). I will almost surely pick up the baltic birch this weekend and start cutting it to size.

[michael hurd]

The Pioneer receivers have known low output voltages in the pre-amps, and not quite sufficient to drive a pro-amp. The EP 2500 has a lower input voltage than most "pro" amps, and can develop full power with 1.23 volts in.

You would not get full output at all from the Behringer paired with the Pioneer. An amplifier is a voltage multiplier.... it takes a certain amount of input voltage to get full output. The gain control does not limit the amount of power that the amp can produce, rather it adjusts the amount of input voltage that is required to get full output.

In the case of a pro level device driving the EP 2500 amp, you would turn the gain down on the amp, as the input voltage being higher would overdrive the amp.... meaning it will clip. Having the gain controls set properly are crucial to getting the best S/N and output.

As far as the brace is concerned, If you put a 1x2" on each panel it would stiffen it, and change the resonant frequency. You could always do a brace that connects all 4 walls.... with a large hole in it or several small holes. This makes it a bit harder to calculate the volume. What I meant in the original post is that the 1x2 ( or whatever dimention you have ) will act as a brace, not necessarily needing any more panels.

Making a cabinet twice as thick results in a 8 fold increase in stiffness.... but also heavier. An acceptable alternate is to use a few bits of scrap ripped in the saw to a certain width... this makes calculating the volume displaced by it easier. Glue and screw to the walls and it will make it a lot stiffer.

Diagonal braces require a bit more work, but if you have the time, they really help out.

[dcmo]

So how does one know when the cleanbox has the right amount of voltage being sent? All it says is to adjust the control for the best signal strength and clarity. Does one just keep turning the gain up on the cleanbox until it is at the loudest it can go and still retain the optimum clarity. If so how does one judge clarity with test tones? Is there a device that could test the voltage being sent from the cleanbox?

Another line of thinking; if all it needs are 1.23 volts, should this be what one shoots for or would going even a little higher make it easier on the amp. If one can go higher, just how much higher would that be?

[michael hurd]

With the amplifier gain turned all the way up it requires 1.23 volts to make full power. Ideally if you are using a cleanbox ( or other like device ) you will set your Pioneer a bit less than 3/4 ouput in the menu for level ( say if the LFE output adjustment goes to say... + 12, set it to about 3/4 of that or around + 8 ) this will keep loud transients in DVD's from clipping the pre-amp output and producing distortion that will get amplified.

The cleanbox is designed to boost voltage to the amplifier to better match consumer level and pro-level equipment. The website does not mention what the maximum input voltage is, but should accept up to at least 8 volts, as most pro stuff does.

Ideally you want to be able to drive the amplifier fully without clipping before as in the output stage of the AV receiver, or in the ART clean-box itself. This will take a bit of time to get ironed out... like I said set the Pioneer LFE out to somewhat less than full, set the clean-box to less than full, and with high level volume in the Pioneer ( your reference volume ).. then slowly turn up the EP2500 gain control until you get full output.

[dcmo]

Well I received the cleanbox yesterday, but while thinking about the task at hand (still waiting on the driver, supposed to be in tomorrow - hopefully it will ship then) I realized (should have known all along, knew it was going to be like this anyway) that it might not be necessary. I say not necessary (still might be though) because it's not the Pioneer that is going to feed it the signal but rather the RSW15. Looking at the specs for the RSW15 it says it puts out a line level signal, but nothing about the voltage. The signal is going to go from the Pioneer to the RSW to the Maelstrom. Will I need to keep the cleanbox in the chain (between the RSW and the Behringer), is the RSW going to feed the Behringer what it needs? Not a big deal at all if I still need to keep it in line, but if I don't need it I will have to return some cables and order new ones.

Above you said to slowly turn up the gain control on the EP2500 until I get full output. Does this mean turn it up until I reach reference level (reference level is 75db on the Pioneer)?