Custom Sealed 2x 12" Kappa VQ LowQ Build

[avaserfi]

A member of this forum contacted me looking for a woofer module designed to function optimally in the 50-150Hz range allowing for large output at a relatively low cost while maintaining his aesthetic needs. After some discussion of various drivers the 12 Infinity Kappa VQ was chosen over the others primarily because of its price [the other options were as linear, but more expensive also requiring more amplification]. Both Kappa drivers will be in a single enclosure sharing airspace.

There were certain requirements of such a build:

1) Due to the higher crossover point it needs to be placed extremely close to the speaker it will be supplementing. Because of this it will be a stand for a center channel.

2) Due to the high crossover point extra bracing/damping will be required to make this unit resonance free. Requirements of bracing/damping increase exponentially with each octave. This unit will be close to the range of serious resonance problems, but use of proper bracing techniques and a steep crossover slope will help.

3) Size requirements. Maximum size could be 14" tall x 25" deep x 25" wide. The actual sizing will likely come in closer to 14" tall x 13" deep x 25" wide.

4) Aesthetics. It has to be pretty while being durable. Due to this a textured finish will be used. Black undercoat with black stone finish. The possibility of a magnet mounted grill is being looked into. If this does not happen no grill will be used.

5) Functionality. Depending on future use the client wanted a pair of external binding posts rather than having the wiring internal just in case he decides to use more than my minimum recommended 900watts of amplification. Along side this unreasonable amounts of SPL were requested in the 50-150Hz range. The unit models at about 118db in this range with 900watts input amp limited.

6) Shipping is a concern. A custom shipping crate will be made such that the subwoofer itself will be decoupled during the entire shipping process. Also, the crate will provide puncture protection in the form of a gapped double wall, just in case.

Thus far the modeling of this driver is complete. I will begin working on the CAD design shortly.

SPL vs Frequency at 900 watts:

Cone excursion vs Frequency at 900 watts:

Please note these images say MidQ alignment in them, but they are actually models of the LowQ alignment.

As far as who this is for...it shouldn't be too hard to guess . If not, I will let him make some grand entrance.

More to come...

 

[adk highlander]

Very interesting. With that requency response range what will this be used for?

It must be Mike C.

 

[avaserfi]

Very interesting. With that requency response range what will this be used for?

Well, this unit would be a perfectly capable stand alone subwoofer, especially for music, but it would also perform well with movies. Modeling in at over 100dB at 20Hz with 900 watts of input amp limited*.

From my understanding the subwoofer will be used primarily to achieve mid-bass 'slam' via parametric equalization.

*While typically modeling of high power/excursion scenarios are not representative of a drivers actual performance due to lack of linearity the Kappa VQ is a proven linear device.

 

[avaserfi]

CAD Update

Sizing has been finalized along with the mock up on CAD. Final external dimensions will be 13.5" tall x 27" wide x 16.25" deep. The front baffle is 1.5" thick to allow for flush mounting to be used.

Fairly simple bracing techniques will be used, but due to the relatively high pass band intended the bracing will be supplemented with steel and/or viscoelastic damping to allow for an inert cabinet.

The pictures:

Side view:

Internal aerial view:

Side view:

 

[mike c]

the idea:
the center channel on top of the new DIY sub

purpose:
more bass? what else?

front view:

seriously though, the purpose:
playing around 80-120hz of the center channel frequencies

 

[mike c]

there's actually too much "voices" above 150hz for my taste - i've pretty much narrowed the punch frequencies to below 150hz

when i do get more subs for the mains, the mains will actually become overkill - because of less frequencies required of them.

it's going under this center speaker:

we can't have some extra floor space doing nothing, can we?

unfortunately, the center is 25" in width ... Andrew can't fit the two 12"er's into a 25" wide baffle.
so the eD's will have to go do Left and Right Surround duty (again, 80-120hz)

 

[cbraver]

Yeah, once you moved up those frequencies everything else would have to match or you'd get a drone sound. And the low frequencies seem to be much easier on the ears, at least for me.

How are the crossovers going to work? Pass the L & R's over at 120 to the eDs, the C over at 150 to the new super dual, and then pass them all below 50Hz to your 6 SVSs?

Please post a video of 36 Mafia - Late Nite Tip playing when you are done. Even if you hate rap, you kind of have to. It's the anthem of bass junkies.

 

[Matt34]

Cool little project Mike and Andrew. For some reason the filters here are letting me see the pictures you post Mike. First time I've seen your system since the flood you had in your basement.

 

[mike c]

Yeah, once you moved up those frequencies everything else would have to match or you'd get a drone sound. And the low frequencies seem to be much easier on the ears, at least for me.

How are the crossovers going to work? Pass the L & R's over at 120 to the eDs, the C over at 150 to the new super dual, and then pass them all below 50Hz to your 6 SVSs?

Please post a video of 36 Mafia - Late Nite Tip playing when you are done. Even if you hate rap, you kind of have to. It's the anthem of bass junkies.

the L C R preouts from the receiver is sent to a DCX2496 to split the signals to highs and lows. the mains play 80hz and up, the main subs will play parallel 80-120hz. and the 4 LFE subs will still play 80hz and below.

when i'm done with this, all channels will have their own subs playing 80-120hz or so - except the rear surrounds which will share a sub as soon as i get a low pass crossover for that one.

Cool little project Mike and Andrew. For some reason the filters here are letting me see the pictures you post Mike. First time I've seen your system since the flood you had in your basement.

must be because you are about to come home (somebody's looking over your shoulder)

this isn't the HT that got flooded though ... this one is in the house where i live everyday. so i can go crazy here, the other one is neater, will have better speakers, but only two subs

 

[avaserfi]

Update.

Got some work done today, of course, I woke up sick... Anyways that didn't stop me. I will be placing the rear baffle on in the middle of the night and then applying Bondo and hopefully get some painting done tomorrow...

 

[Haoleb]

MDF?! What happened to Cabinet grade ply?

 

[avaserfi]

MDF?! What happened to Cabinet grade ply?

MDF was used over plywood to reduce labor costs greatly. I typically prefer using a high grade plywood, but the amount of work required to properly paint such a material is immense compared to the work required with MDF. You will note I still used a nice piece of high grade ply for the second part of the baffle to mount the drivers to for added stability.

 

[mike c]

.

you're awake again?

what happens to this thing when wired in series then 8 ohm bridged to just 360w - how much SPL do we end up with?

 

[ParadigmDawg]

I hope Mike's little sub project is not keeping you from finishing mine!

 

[avaserfi]

I hope Mike's little sub project is not keeping you from finishing mine!

The acoustic panel frames? I just need to go to lowes sometime and and by some wood. That will only take 10 minutes since I can cut straight and use a ruler .

 

[avaserfi]

Next update

Drivers:

 

[Matt34]

Note to self, I need more clamps.

Looks good Andrew.

 

[Haoleb]

Did the inserts fly all over inside the box and ding up the baskets on those drivers or am I the only one who's been fortunate enough to have that happen everytime I got one

 

[avaserfi]

Note to self, I need more clamps.

Looks good Andrew.

I actually used an industrial adhesive to attach the rear baffle to the rest of the box. I didn't necessarily need that many clamps, but I was sick and having trouble sleeping so...I spent the extra time doing something not needed.

Did the inserts fly all over inside the box and ding up the baskets on those drivers or am I the only one who's been fortunate enough to have that happen everytime I got one

Just you. All the units I have ordered haven't had a single problem .

The corners of the cabinet have been rounded and I will be starting to bondo the unit and eventually paint it, but now I need to catch up on school work and get over whatever has me sick.

 

[MidnightSensi]

Nice looking bin. The mid boxes are important for big rooms.

Have you looked at the LAB subwoofer?

prosoundweb.com/index.php/lsiuni/article/lsp_documentation_page_drawings_photos_specs_and_more/

Powerful with usable output down to 25-30Hz, but generally cross'd over well before that to a ported bin in applications that want very deep bass.