Simple 12" Infinity Kappa VQ MidQ Plans

[avaserfi]

Due to a large amount of requests I have spent some time designing a simple version of my Infinity Kappa VQ Build. These plans would likely be easily completed by someone with wood working experience in less than one day. A novice would probably want to take more time, but shouldn't have much trouble with this design.

The graphs:

Transfer function:

SPL versus frequency at 400 watts:

Cone excursion at 400 watts:

Port air speed at 400 watts:

The CAD design:

The cabinet is 22.5" wide x 22.5" deep x 25" tall with a port that measures 12.5" wide x 55" long x 3" tall.

With the top taken off:

Front baffle and top taken off:

Side taken off as well:

One cross brace removed as well:

Cut list (Use 3/4" cabinet grade plywood):

Front baffle: 21" x 24"
Rear baffle: 22.5" x 24"
Sides: 21.75" x 24"
Top/Bottom: 22.5" x 22.5"
Cross brace (large): 16.5" x 21"
Cross brace (small): 6.25" x 21"
Port bottom:
2x 18" x 3"
17.25" x 14"
Port back:
2x 24" x 3"
18" x 14"
Port top:
2x 13.75" x 3"
13" x 14"

You will want to get some OC705 or 8lb Rock wool to place inside the cabinet. Use a 4" piece wrapped in cloth (to eliminate chances of pieces being blown out the port) and glue it (using 3m Spray 77) to the large brace.

Recommended amplifier EP2500.

Thats everything. Optional things you can do to increase sound quality:

1) Round over/cove the port corners with a router. This will decrease air turbulence and minimize chances of port noise/compression at high SPL.

2) Integrate the unit with a DCX2496. This will also allow for equalization of your subwoofer for maximum perceived sound quality.

3) Build 2 and integrate as a stereo pair with the DCX.


**Please note I make no guarantees about actual performance as there are a variety of factors that effect such a unit.***

Feel free to ask any questions either here or via PM.

 

[Sheep]

Could you make one for a 10inch VQ?

SheepStar

 

[mike c]

thanks for doing this ...

 

[WmAx]

Andrew makes no mention of possible in room performance levels. But, with his slightly different, and for more complex version(in terms of bracing, fascia and round overs in the slot port), he achieved maximum SPL of 120dB at 20hz, corner loaded, and measured at a little over 2 meters away in distance at the listening position. This was the in-room SPL for 1 unit powered by a bridged Behringer EP2500 amplifier.

I don't know if this result can be achieved on average with this setup - but it is his maximum result that I found impressive.

-Chris

 

[Matt34]

I be sure to post when I get mine done, having a pair of these made. Big thanks to avaserfi for this.

 

[Matt34]

Going to go ahead and make this a sticky.

 

[Haoleb]

Theoretically, How would a single, or stereo pair of this compare to say, the Axiom EP500 or 600 or PB13 ultra?

 

[WmAx]

Theoretically, How would a single, or stereo pair of this compare to say, the Axiom EP500 or 600 or PB13 ultra?

It is not fair to compare a pair. The potential output of one of these is so great, that it would be very similar to a PB13 Ultra, except that the PB13 would not have as much output in the lowest range, because the port on Andrew's design offers less compression due to the large cross section area, and the PB13 would potentially offer greater output by some degree, in the higher octaves, because of it's larger cone surface radiation area. But to realize the output potential of the Kappa Perfect cabinet design above, you would need to use a bridged EP2500 to deliver sufficient peak power. However, one does not need this level of capability in actual use. It's overkill. However, stereo units are always going to provide better ability to integrate with the main speakers, even if you don't need the output ability that is possible.

-Chris

 

[E-A-G-L-E-S]

Very cool...thanks for your work!

 

[Haoleb]

I know this is an impossible question to answer but sound quality wise, Is this really going to be THAT good?

The reason I ask is because I have been shopping around for a sub for a while now and everything that i really like is out of my budget by the time I get it shipped here, I am in the process of hopefully getting a used EP2500 for a great price and am now thinking of going the DIY route. I looked at lowes yesterday and 4x8 sheets of 3/4 MDF are only 40 bucks I figure I could build the cabinets for just around 100 bucks, With this design I would probably even laminate a second layer of MDF to all outside panels for even greater weight and rigidity.

I wish there was more info on actually building this exact design and doing comparisons with commercial products as I would really want to know for sure that if I am going to drop close to a grand to build a stereo pair of these that they are going to devastate anything else I could have gotten commercially, especially the subs I have asked about. Particularly because my parents theater room has the EP600 which i have used in my system for a month or so, and have been quite pleased with its performance for my uses.

 

[WmAx]

I know this is an impossible question to answer but sound quality wise, Is this really going to be THAT good?

I know that audio seems like a mystery, but really, it's not. Your SQ will be dictated, when using a driver like this one, and in a cabinet like this one, by your tonal shaping of the sound using a device like the DCX, room treatments, acoustics and other secondary factors. The driver IS that good, and the cabinet IS that good, if 'IS THAT GOOD' is to mean transparent. If you don't cross it over with ideal xover setting to get a smooth transition to the mains, if you place it in the room where the response is the worst, if you try to cross it over too high(>80Hz), then yes, you will have issues. If you build the cabinet poorly and/or don't use the recommended dampening, then yes, you will have issues.

BTW, MDF is not as good a choice as high grade hardwood cabinet plywood. The ply will be stiffer/stronger for a given amount(pushing resonances higher) and it is lower in weight.

-Chris

 

[mike c]

if you were pleased with the EP600 (tuned high), a DIY creation tuned to 20hz will give you a better HT experience.

music SQ wise, well, if you build TWO lfe subs (not stereo), you should have less demand on each of the subwoofers and thus have less distortion.

 

[Haoleb]

My system is primarily for music, The occasional dvd and tv listening done holds much less importance for me. basically, if it sounds good with music it will be just fine for my HT uses.

Its not that I dont understand that this is linear driver and so on, But in my mind anyway, If you could just sit down on the computer, punch in a few numbers into a program and have something that stands heads and shoulders above, why are there so many crap products on the market and why doesnt everybody do it. Make any sense?

This would be a large investment for me and not something that would be practical to even sell if I was dissapointed

 

[WmAx]

My system is primarily for music, The occasional dvd and tv listening done holds much less importance for me. basically, if it sounds good with music it will be just fine for my HT uses.

Its not that I dont understand that this is linear driver and so on, But in my mind anyway, If you could just sit down on the computer, punch in a few numbers into a program and have something that stands heads and shoulders above, why are there so many crap products on the market and why doesnt everybody do it. Make any sense?

This would be a large investment for me and not something that would be practical to even sell if I was dissapointed

I can only speculate: the costs involved with a DIYer on completely different scales as compared to a mass manufacturer. What you can do with $1000, they could do with $300-$400, under mass production circumstances, in terms of parts/materials. But, there is massive over head(building lease/payment, manufacture equipment payments, employee pay/benefits, re-investment dollars, profit margin, etc.). And you take for granted the labor that you are not even figuring - because you are not being charged for labor - but they have to pay an arm and leg to actually build/finish these cabinets properly. So when it all comes down to it, figuring all costs into the picture, your $1000 project did not cost them all that much less to build in all likely hood, and they have to still make a sufficient profit to stay in business and advertise to perpetuate the company.

-Chris

 

[Haoleb]

Alright. I'm In.

just ordered two of the 12vq's

Picking up the behringer DCX and some binding posts/plates at PE, Does that behringer crossover come with XLR to RCA adapters? Need to know incase I have to get them too.

 

[Matt34]

Alright. I'm In.

just ordered two of the 12vq's

Picking up the behringer DCX and some binding posts/plates at PE, Does that behringer crossover come with XLR to RCA adapters? Need to know incase I have to get them too.

No, you'll have to get those seperate.

 

[avaserfi]

Could you make one for a 10inch VQ?

SheepStar

This was a relatively time consuming process. I probably won't have time to do something so detailed for the 10VQ, but would be willing to help you with your build.

Alright. I'm In.

just ordered two of the 12vq's

Picking up the behringer DCX and some binding posts/plates at PE, Does that behringer crossover come with XLR to RCA adapters? Need to know incase I have to get them too.

XLR to RCA adapters are very simple to make, just follow these instructions.

Since you will be using the DCX 2496 I recommend you put a second order highpass filter at 20Hz. This will act as a protection filter such that at high SPL at low frequencies (below 20Hz) there is minimal chance of the driver bottoming out. Also, to fully make use of the DCX2496 you will need a mic, pre-amp and measuring software. The cheapest solution would be following the REW instructions over at hometheatershack.com as you can use some simple cables and a Radioshack SPL meter.

Also, you will want to purchase some OC705 or 8lb rock wool for inside the cabinet as well as some method to decouple the built cabinets from the floor if optimal sound quality is the goal.

 

[Djizasse]

Hi, thanks for providing these "instructions"

I was searching for the driver on ebay, should I only look for the newest model (1600W) or the older ones (1400W) are ok?

 

[Haoleb]

I found some nice Neutrik XLR to RCA adapters at mouser for 8 bucks a peice so i got a couple of those. So far everything is on order except the amplifier which I am hopefully getting used. Going to head to lowes or home deeps and see what they have for plywood or MDF, I may just go with the MDF anyway if its much cheaper.

By my calculations i'll need just under one 4x8 sheet to do one box following the plans which isint too bad at all.

Can you elaborate a little more on this 20hz filter i have not read up too much on the crossover unit, I thought it would have some kind of subsonic filter or something along those lines as I did read mention of a HP in one of the threads. If i'm going to be building a passive crossover to put inside the speaker, any schematics? I will admit that I have never dabbled in speaker design so am in unfamiliar territory here.

 

[avaserfi]

Hi, thanks for providing these "instructions"

I was searching for the driver on ebay, should I only look for the newest model (1600W) or the older ones (1400W) are ok?

Please provide links.

I found some nice Neutrik XLR to RCA adapters at mouser for 8 bucks a peice so i got a couple of those. So far everything is on order except the amplifier which I am hopefully getting used. Going to head to lowes or home deeps and see what they have for plywood or MDF, I may just go with the MDF anyway if its much cheaper.

Lowes carries a plywood that is 23/32mm that costs about $35 per 4'x8' sheet which would be sufficient for your application. An exact 3/4" sheet is about $45 for the same size. Both these are far superior options to MDF.

Can you elaborate a little more on this 20hz filter i have not read up too much on the crossover unit, I thought it would have some kind of subsonic filter or something along those lines as I did read mention of a HP in one of the threads. If i'm going to be building a passive crossover to put inside the speaker, any schematics? I will admit that I have never dabbled in speaker design so am in unfamiliar territory here.

There would be no need to use a passive crossover in this case. You could simply use the DCX2496 to create this protection filter. If you go to Behringer's site you can download the DCX software for free and start to get familiar with it.

Cone excursion with protection filter at 400w:

You can compare this to the previously posted excursion with no protection filter and see that such a filter prevents over excursion at low frequencies and high SPL. This is had at minimal cost to extension.