DIY sub

[flippo]

Thanks

Still planning to use the infinity driver but keeping options open!

 

[synapsis]

2 Perfect 12.1's, seperate boxes

Alright, so i picked up 2 plate amps from mcm at $85 a pop (300W @ 4 ohms), and just yesterday picked up two of the woofers (12.1 kappa perfects) from my work (futureshop ). Now, im looking to design the boxes for them. I modeled the driver in WinISD, giving me a 125L (55cmx55cmx55cm) box, with 1 inch thick MDF. It seems ported gives a better SPL curve, allowing much higher volumes at the lower frequencies.

As im a greenhorn in making subwoofer enclosures, i was wondering if im off to the races with this design, or if you guys would recommend something else, im very open to ideas. Ive got all my materials (minus the wood), so now its just up to design and building... i cant wait!

Let me know what you guys think.

 

[WmAx]

Alright, so i picked up 2 plate amps from mcm at $85 a pop (300W @ 4 ohms), and just yesterday picked up two of the woofers (12.1 kappa perfects) from my work (futureshop ). Now, im looking to design the boxes for them. I modeled the driver in WinISD, giving me a 125L (55cmx55cmx55cm) box, with 1 inch thick MDF. It seems ported gives a better SPL curve, allowing much higher volumes at the lower frequencies.

As im a greenhorn in making subwoofer enclosures, i was wondering if im off to the races with this design, or if you guys would recommend something else, im very open to ideas. Ive got all my materials (minus the wood), so now its just up to design and building... i cant wait!

Let me know what you guys think.

The 12.1 Perfect should be used in a ported enclosure. The VQ version can be used in any enclosure optimally - but the 12.1 Perfect version is ideal in ported/passive radiator systems.

A critical consideration is the port cross sectional area. This driver, at low frequencies, needs the equivalent of about 30 square inches in the cross section of the port area, if you want to have high SPL output at very low frequencies near the port tuning. If you use say, a 4" port, you will have substantial maximum SPL compression at and around the tuning frequency.

If you want a specific suggestion for an enclosure design, I'll provide one.

-Chris

 

[synapsis]

The 12.1 Perfect should be used in a ported enclosure. The VQ version can be used in any enclosure optimally - but the 12.1 Perfect version is ideal in ported/passive radiator systems.

A critical consideration is the port cross sectional area. This driver, at low frequencies, needs the equivalent of about 30 square inches in the cross section of the port area, if you want to have high SPL output at very low frequencies near the port tuning. If you use say, a 4" port, you will have substantial maximum SPL compression at and around the tuning frequency.

If you want a specific suggestion for an enclosure design, I'll provide one.

-Chris

I would love to have an enclosure design, be it either a port or slot, as long as it doesnt have quite as many braces as the one that avaserfi designed for his VQ! I dont want to make something that complicated . And as for maximum SPL output, i dont want to make the box huge and standout by anymeans (ie sonotube styles ), but a nice slightly audible 19Hz would be wonderful

 

[cbraver]

I would love to have an enclosure design, be it either a port or slot, as long as it doesnt have quite as many braces as the one that avaserfi designed for his VQ! I dont want to make something that complicated . And as for maximum SPL output, i dont want to make the box huge and standout by anymeans (ie sonotube styles ), but a nice slightly audible 19Hz would be wonderful

You won't be able to hear 19Hz, but you'll feel it!!! In order to make this a 20Hz sub the box will probably have to be sizable. I'm interested to see what WmAx posts!

 

[avaserfi]

I am almost complete with my build of a 12" Infinity Kappa VQ which is extremely similar to the 12.1 Perfect, but is slightly more versatile. You can see the build here.

The Perfect seems to model very similarly in WinISD. In fact the two model so similarly that I would recommend the same dimensions as mine. This will give you an F3 of about 20Hz.

Using a enclosure volume of 3.5 cubic feet with a slot port with a cross section of 12.5" x 3" and is 55" long you will get a subwoofer that goes low and plays loud (modeling at 109dB at 20Hz anechoic). With this model first port resonance would be about 120Hz which mean you would not want to cross the subwoofer over at higher than 80Hz. To ensure to unwanted noise is not introduced it would be a good idea to purchase a high quality crossover such as the DCX2496. This would allow you to put a high order crossover in place as well as allowing you to integrate your subwoofer ideally giving maximum sound quality. Another plus of this unit is that it is a parametric equalizer allowing you to adjust your bass response to your tastes.

As far as bracing goes my subwoofer has far more than enough. If you design a bracing matrix that simply ties all the axes together you should be fine. For internal dampening you will want to use 2" layers of OC705 or 8lb mineral board on the sides and as an option the top. The bottom should have a 4" thick layer.

In regards to the port you will want to round all the edges as shown in my build this will keep air turbulence to a minimum reducing the chances of port chuffing. Also, internally be sure nothing is within four inches of the slot to allow for maximum airflow. Another step you could take to insure the port is properly designed is using four 1" rounds within each layer of the port. This will keep port resonance to a minimum as well as making life much easier (slot ports can be a pain to build). If you do this be sure to find the total volume taken by the rounds and lengthen the port appropriately.

I would recommend using an EP2500 to power these speakers as it is a high quality, but inexpensive amplifier for the job.

Let me know if you have any questions.

 

[WmAx]

Avaserfi's advice is good. But I will suggest that you skip the large radius rounding of the slot ports -- this will add substantial complexity. If you don't want to do complex bracing, I doubt you are willing to do the radius. But if you do, that's a good thing. BTW, if you actually build a sub cabinet to this spec using that driver, it should decimate even a Velodyne DD15 in low bass output and distortion.

-Chris

 

[synapsis]

avaserfi,

I followed the box that you are making for your VQ, with several weeks of work, im sure i could make a similar box, however, i was looking to go with simplicity, as it will take me less time, and also will have fewer things for me to mess up . The slot port shouldnt be a problem, it is more the bracing and dampening that concerns me. When you say 8lb mineral board, is this a sheet I'm adding to the interior of the sub for a thicker box? Would it be possible to use multiple layers of MDF for this (less materials = lower cost, which is also what im going for, im a student and cheap )

Also, to power the sub(s), i already have the MCM 300W RMS plate amplifier. I think im going to skip the crossover, as again, more cost, more complications. Is the unit you were mentioning a standalone eq designed for subwoofers? If so it could always be added in the future.

WmAx,

I do plan on building 2 of these subs, as i already have the amp and driver for it, just need a plan on enclosure and some wood and im of to the races. I cant wait to sit my boss down and blow his velodyne out of the water, to think he makes fun of my custom speakers for his beloved "energy's"

 

[avaserfi]

The slot port shouldnt be a problem, it is more the bracing and dampening that concerns me.

As I said in my previous post my bracing was more than sufficient and less could easily be used. The most efficient method would be tying together all the axes (XYZ). I would recommend using oak for this application as it is far more dense than most alternatives.

When you say 8lb mineral board, is this a sheet I'm adding to the interior of the sub for a thicker box? Would it be possible to use multiple layers of MDF for this (less materials = lower cost, which is also what im going for, im a student and cheap )

This is actually an acoustic material that will absorb standing waves within the box. It does not need to be accounted for in volume calculations. This material is dirt cheap at around $0.60 per square foot. I recommend seeing if there are any SPI locations near you to purchase it if there is not you can find it online. OC705 is the only other reasonable alternative I am aware of, but costs about 3 times as much as the mineral board. Be sure to wrap the material in cloth just in case it degrades within the subwoofer. If you do this none will be expelled via the port if the degradation occurs. This dampening step is not expensive at all and is vital to achieving high quality sound reproduction.

Also, to power the sub(s), i already have the MCM 300W RMS plate amplifier. I think im going to skip the crossover, as again, more cost, more complications. Is the unit you were mentioning a standalone eq designed for subwoofers? If so it could always be added in the future.

This is a stand alone unit you could added in the future. You will want to have some control over the frequencies being played by the subwoofer. Using a receivers crossover would be a reasonable alternative. If you are looking for a cheaper alternative to the DCX2496 the BFD1124 is a good alternative. Look at the hometheatershack for free software to use with the unit. The BFD is also an external unit that can be added later.

I do plan on building 2 of these subs, as i already have the amp and driver for it, just need a plan on enclosure and some wood and im of to the races. I cant wait to sit my boss down and blow his velodyne out of the water, to think he makes fun of my custom speakers for his beloved "energy's"

Let us know how this one goes. I think you might have him crying .

 

[synapsis]

This is a stand alone unit you could added in the future. You will want to have some control over the frequencies being played by the subwoofer. Using a receivers crossover would be a reasonable alternative. If you are looking for a cheaper alternative to the DCX2496 the BFD1124 is a good alternative. Look at the hometheatershack for free software to use with the unit. The BFD is also an external unit that can be added later..

For now i will have to use my receiver, which is a decent not to expensive introductory Harman Kardon AVR-240. From what ive heard and experienced myself, i hear it is best to keep the plate amp's freq set at max (120), and do all the eq through the receiver. Correct me if im wrong, as this is an easy change.

As for the dampening, i'll see if i can find something around town, i live outside toronto in canada, it seems things are always harder for me to find in country . Also with the bracing, what is the most efficient way to brace between 2 axis, without interfering with air flow and whatnot? Ive seen holes cut in full sheets of wood, short sheets between etc... but what would be easiest? Sorry for all the questions, im kinda excited, even though the building of the sub is what is going to take the longest

Oh, ps, i have some spare dynomat laying around as well, would this serve any useful purpose (lining the inside layer of MDF before the fiberboard?)

 

[avaserfi]

For now i will have to use my receiver, which is a decent not to expensive introductory Harman Kardon AVR-240. From what ive heard and experienced myself, i hear it is best to keep the plate amp's freq set at max (120), and do all the eq through the receiver. Correct me if im wrong, as this is an easy change.

You are correct, generally it is best to use the receivers crossover while bypassing or setting the amps to the maximum level. Long term I would strongly recommend buying one of these stand alone units as they will give you far more functionality.

As for the dampening, i'll see if i can find something around town, i live outside toronto in canada, it seems things are always harder for me to find in country .

I strongly suggest looking into this fully and finding some. It can be found online at various places, but you pay a premium for shipping. If you have trouble open up a phone book and look for anywhere that would sell insulation or even deal with it. Heating/cooling places are a great source. Even if they normally wouldn't sell to the public call and ask it cannot hurt and you might find some where you wouldn't expect. If you have exhausted all resources contact me via PM and we can arrange a shipment - it is that important.

Also with the bracing, what is the most efficient way to brace between 2 axis, without interfering with air flow and whatnot? Ive seen holes cut in full sheets of wood, short sheets between etc... but what would be easiest?

I find the easiest method to be a biscuit joiner or Craig jig, but these require additional tools. A more simple way to do this that would be cheaper would be buying wooden dowels and drilling holes into the wood and making a T-joint with that. Be sure to fill all the holes the dowel would be put in with glue before hand. You will need to use a clamp on the joint until the glue has solidified some if you use this method. Pictures of similar examples are in my build thread.

The other methods you mentioned would work as well. The easiest would likely depend on your comfort level with various methods and the tools you have at your disposal.

 

[synapsis]

blah, need this post for a link...

 

[synapsis]

I strongly suggest looking into this fully and finding some. It can be found online at various places, but you pay a premium for shipping. If you have trouble open up a phone book and look for anywhere that would sell insulation or even deal with it. Heating/cooling places are a great source. Even if they normally wouldn't sell to the public call and ask it cannot hurt and you might find some where you wouldn't expect. If you have exhausted all resources contact me via PM and we can arrange a shipment - it is that important.

I think i found a place that is not to far from where i am, http://www.glasscellisofab.com/en/mineral.html is the website, could you point me in the right direction in terms of exactly what im looking for, ive never delt with this material before, so i dont know exactly what i should be getting (other than 2inch and 4 inch 8lb mineral fiber board... ). Also not sure if you saw the edit, but is dynomat of any use? i have some laying around...

Thanks so much for all the great advice avaserfi, ive gotten much futher in my building plans than expected very quickly!

 

[WmAx]

WmAx,

I do plan on building 2 of these subs, as i already have the amp and driver for it, just need a plan on enclosure and some wood and im of to the races. I cant wait to sit my boss down and blow his velodyne out of the water, to think he makes fun of my custom speakers for his beloved "energy's"

If you want to surpass the Velodyne DD units, you will have to get the DCX2496(or comparable) device that I have suggested. This device provides for ideal crossover integration and bass response customization. You have to be prepared to do some basic room acoustic measurements to set these devices up. A Radio Shack SPL meter and Room EQ Wizard(freeware) are all that you need to make the measurements. And remember, room acoustical treatments are the best solution for high bass frequency correction.

The amplifier you have chosen will work, but I would recommend against installing the amp in the cabinet. This is because instead of buying a 2nd amp for the 2nd sub you plan on building, buy an EP2500 amplifer. This is a much more capable amplifier and you will connect the DCX2496 directly to this via XLR cables. The EP2500 will power both sub cabinets with ample power(650WRMS at 4 ohms, to each channel).

-Chris

 

[WmAx]

Oh, ps, i have some spare dynomat laying around as well, would this serve any useful purpose (lining the inside layer of MDF before the fiberboard?)

The Dynomat has no real application for the subwoofer. If you design the subwoofer cabinet with proper bracing, the panel resonance frequencies will be above the passband in which you operate the subwoofer. Also, consider cabinet grade hardwood plywood as opposed to MDF. This type of ply is a better choice because it is stiffer/stronger as compared to MDF and it is lower in mass as compared to MDF.

-Chris

 

[avaserfi]

I think i found a place that is not to far from where i am, http://www.glasscellisofab.com/en/mineral.html is the website, could you point me in the right direction in terms of exactly what im looking for, ive never delt with this material before, so i dont know exactly what i should be getting (other than 2inch and 4 inch 8lb mineral fiber board... ). Also not sure if you saw the edit, but is dynomat of any use? i have some laying around...

I am not actually familiar with the product designations of the mineral board. I would just call the company and ask if they carry 2" thick 8lb mineral board. To make 4 inch chunks buy some 3M Super 90 glue and you can adhere two pieces together. If they don't carry two inch, but have 1" you can do the same, but glue four pieces together.

If the company does not know what 8lb mineral board is ask for the "FBX Industrial Board Insulations 1280." Based on the absorption coefficient of this material it should work well.

 

[synapsis]

perfect, it shouldnt be a problem getting the mineral fiber board. They have a few warehouses around my area. Good to know that dynomat is useless, i probably would have coated the inside thinking it would help dampen the enclosure. As for getting an external amplifier, i think it is out of the question, as ive already invested in buying the two plate amps. They may not function at 100% with these cheaper plate amps, but thats something im going to have to live with. For my first sub build, im sure it will be low and loud enough for a townhouse with neighbors on both sides . Let the earthquake begin !

Avaserfi and WmAx, thanks so much for all the help you've provided me with. I dont know if chris is still going to ring me up some plans, or if i am just going to match avaserfi's build with less complications . But either way, i should be able to handle it! Thanks again!

 

[flippo]

Plate amp

What other sites sell plate amps besides Parts Express?

 

[synapsis]

MCM audio has some plate amps on sale, i picked up the 300W RMS one for 89$,
you should check it out, it is very decent, especially for the price. If you need more than 300W though, you will have to look elsewhere...

http://www.mcminone.com/

It's pic should be staring you in the face... i ordered two of them to power the infinity 12.1 perfects, they get shipped in a dayton box, which makes me think that dayton custom made these amps for MCM... but who knows.

I hear Bash's 500W amp is a nice step above, but you'll be paying alot more for it!

 

[flippo]

What insert?

In the model it was reccomended to use low insert. In the driver manual for volume of 3 cubic feet it is reccomended to use the mid insert. Which way should I Go?