Vortex Speaker Kits

Thanks erich. MTG’s tower design from post #3 looks most desirable to me, I’m assuming there’s ports placed on the rear for that enclosure. Maybe Matt still has the prototype dimensions as I’m curious how high up the driver is centered.

 

That enclosure for the Vortex-15 is 17" wide x 44" tall x 18.5" deep. I used two 4" ports 4" long (flared ones parts express sells) on the rear of the enclosure which tunes it to ~32hz. Driver center is 10.75" down from the top.

 

I'm getting ready to build enclosures this size and I would like to incorporate a slot port on the front. Can you tell me what size the port should be to achieve similar tuning? Will there be any issues swapping the port from the back to the front?

 

If you make the port full width (15.5") x 1.5" high x 4" long you should end up with roughly the same tuning. No issue putting it on the front of the cabinet.

 

Since tower flatpacks for these aren’t in the immediate future, are there any T/S parameters we can use to model sealed vs ported?

 

Hi - can I just check this is correct? When I calculate volume (assuming 3/4" thickness) I get 6.5 cu. Minus perhaps 1/4 cu for ports, driver and braces it still comes out to well over the 5cu suggested volume for the Vortex 15. I see 35hz mentioned for 5cu, and elsewhere 33hz - if the 6cu+ for the extra few hz extension over the 5cu?

One other question if I may - would making the cabinet 2" wider (and 2" shallower to keep same volume) make and appreciable difference to frequency response?

Thanks
Bevan

 

The flat pack will end a little smaller then my initial prototype cabinet. The smaller cabinet sacrifices just a little bit of extension and low end output. The 15" vortex driver itself works well up past 6cuft tuned to 30-40hz.

I'd try and keep the baffle width the same if you can. Adjustments there have impacts on the baffle step and diffraction frequencies which have been compensated for in the crossover with the stock baffle width. You could certainly make it 2" wider but know that the response in the lower midrange may just be slightly more uneven then stock, how much worse I can't say.

 

Thanks Matt.

 

I think I found the T/S for the 15” from an AVS thread:
15" Specs:
Fs: 39.3hz
QM: 12.12
Vas: 259.2 liters
Cms: .249 mm/N
Mms: 66.1 g
SD: 856.3 cm^2
VD: 348.0
QE: .33
Re: 5.05 ohms
Le: 0.60 mH
Bl: 15.68 Tm
QT: .33
SPL: 98.6 1w/1m
Mmd: 51.7 grams

 

I get errors with these on WinISD

 

Enter just
Qms, Mms, Cms, Re, BL, Le, Sd.

Xmax = 6mm,
Pe = 250w

 

12" Specs:

Qms 8.63
Mms 44.5 g
Cms 0.294 mm/N
Re 7.110 Ohm
BL 17.42 Tm
Le 0.72 mH
Sd 532.4 cm^2
Xmax 6mm
Pe 250w

Fs: 44Hz
Qts: 0.279
Qes: 0.288
SPL: 97.47dB

 

Is it necessary to line the interior walls of the enclosure with denim insulation? Any benefits?

 

You don't have to use denim, you can use polyfil or acoustic foam. It is however necessary to use some kind of damping material prevent the sound generated off the backside of the woofer cone from bouncing around inside the cabinet and reflecting back out through the cone itself.

 

Egg crate acoustical foam is available in 1.5” or 2.5” thickness. Does it matter how thick it is?

 

You can get away with either.

If you are building them in a tower enclosure similar to my prototype enclosures I discovered there is a quarter wave cancellation that can occur along the vertical axis of the enclosure. I found filling the top portion of the cabinet (midpoint of the driver upwards) and the bottom 6-8" greatly reduced the issue. I have a feeling placing damping material in the middle of the cabinet would be more effective but I was afraid of it blocking the path to the ports and reducing their output contribution.

 

Would it be crazy to use the Vortex-12 in, say, a ~1.5cuft sealed box?

The reason I ask is because the system is already running 8x JBL CX1200 12" subwoofers in a series of cheapo prefab car subwoofer boxed I purchased on eBay. Buying two more of them would save me quite a bit of time and money relative to building the cabinets myself, since I'd need to pay someone to do the cuts for me. I assume the ported prefab boxes wouldn't work well because the slot port tuning frequencies tend to be very low.

The crossover to my mains (a pair of SEAS Idunns) is currently set at 120Hz and I've run it at 160Hz in the past and been fairly satisfied with it.

These speakers obviously deserve nice cabinets, but I'm not sure I want to design/build them around my current furniture and room, which is likely to change over the next couple of years.

 

You can use the Vortex-12 in a sealed box in the 1.0 - 1.5cuft range if you don't mind the f3 being around 100-110hz which seems like it should not be a problem in your case.

 

Can I ask how come the measurements of the 15 are a bit better than the 12? I would have expected a bit of narrowing off axis at the crossover point on the 15 due to beaming?

And opinions that might help me choose between 15 and 12 would be appreciate.

Cheers
B

 

The 15" radiation pattern is more narrow then the 12" below the crossover point but that more narrow pattern just happens to match up to the radiation pattern of the horn/HF driver. So the overall directivity control of the 15" Vortex is therefore more uniform down to lower frequencies then the 12".

Generally I think the Vortex-15 is the better sounding design, not only is it a more capable and more efficient speaker but the frequency response both on and off axis is slightly better then the 12". The only negative is that it requires an enclosure volume of almost double that of the 12".

 

Alright, so I decided to do the right thing with this project and went with the 15 and am building my own cabinets. This is the first time I've used WinISD, and I want to make sure I get the box tuning and port length correct.

The cabinets are 26x17x13 out of 3/4" baltic birch, giving me an internal volume of ~2.5cuft. Going by the first post, this puts me in the "65hz - 20khz in a ported 2.5cuft cabinet tuned to XXhz with four 2" ports" bucket, so those are the ports I requested and received from Erich (they measure 2.25" in diameter to be precise).

WinISD recommends the "BB4/SBB4 Super boom box" alignment. By default this spits out 4.3cuft cabinets tuned to 39Hz with an f3 of 60Hz.

With 2.5cuft cabinets, I came up with a tuning frequency of 55Hz as giving the lowest f3, around 65-66Hz. The transfer function graph shows a slight hump around 115Hz. The four 2.25" ports should be cut to 4 inches each (measured from the front face of the port flange, yes?).

Does that appear correct? Is that the correct alignment to be using in WinISD or is a different one more appropriate?

 

That sounds about right.

Let me know how it turns out as both the 12 and 15 were voiced in the larger tower cabinets and I'm interested in hearing how you think it sounds in that smaller cabinet. A smaller cabinet will end up with more output in the upper bass/low midrange so I'm wondering if it will end up sounding muddy or bloated in that range.

 

I just got them together to test out for a couple weeks before finishing the boxes. First of all, bravo: these are awesome speakers. They sound huge. My setup is a kind of bizarre hybrid where I spend a lot of time in nearfield sitting at a computer, but also have a sofa further back where I frequently sit and listen with a book or laptop. The appeal of these is that the coaxial alignment gives me a point source for nearfield without compromising on the big speaker sound and even coverage of the room. I was worried about whether I'd like sitting so close to a compression drivers, but I don't think that's going to be an issue at all - smooth as silk.

As for the tonal balance, for this initial go, I wired up the crossover with the HF pad but without the MF pad. I'm guessing from previous posts in this thread, that the MF pad is to dial back some of the BSC when they are placed close to the wall, and that would be in the ballpark of 800Hz for a 17" baffle? I think i will probably try the MF pad because I have them fairly close to the wall by necessity they do sound a touch honky in the mids. I will take some sweeps and play around with EQ before I disassemble them for finishing.

Midbass output is nice. I will definitely be able to cross to my subs a bit lower.