New subwoofer build

[boinger]

Hi I was thinking of building 2 subwoofers for my HT room.

I was initially planning to build 2 15" ported subwoofers.

I came across bear's suggestion of this in a dual opposed configuration:

2x 2x12" Drivers: $600 (~$150/ea)
MiniDSP DDRC24: $450
2 sheets of Baltic Birch 18mm Ply: $100
Amplifier: $500+

I was going to use dayton ultimax drivers but I am open to advice or suggestions for drivers.

All help is appreciated.

[JonMarsh]

Are you considering a plate amp for each cabinet? Makes things tidy. I haven't seen the details of Bear's concept, but I do believe in force cancelling cabinets when possible. There are tradeoffs regarding cabinet size, LF roll off, and the amount of power you need to bring up the LF level to where you want it- larger is usually better.

I've done a couple of subs with Ultimax drivers for friends and they've been happy- lots of travel. But were I doing something like that right now, I would suggest looking at the budget and see if you can use an XBL2 woofer- like the CSS drivers- (available at PE) the BL curve is much more linear, and distortion will usually be lower, especially for music. If this is many for HT LFE, and you're crossing low, then it's not such a big deal.

Just my 0.02.

[boinger]

I was looking at the css drivers. They are double the price of what I was initially looking to spend but they do seem very nice.

I might be able to swing it but the amp might have to suffer if I go for those drivers.

I have an old 5 channel amp. Could I use this for the drivers or would it not be powerful enough?

https://www.anthemav.com/products-archived/model=a5/page=specs

[Bear]

I haven't seen the details of Bear's concept, but I do believe in force cancelling cabinets when possible. There are tradeoffs regarding cabinet size, LF roll off, and the amount of power you need to bring up the LF level to where you want it- larger is usually better.

My only real contribution was looking at radiating area and piston volume rather than just the size of the driver, with the idea of two of a smaller size generally have more Sd, and the ability to offset each other mechanically (dual opposed). For me, 10" or 12" drivers are sufficient. Other people tend to want more. I did snag a Hypex FA502 during December for what will ultimately be a pair of dual-10s. Cabinet #1 should be coming online in a couple of weeks once I get happy with the finish.

On an unfortunately related note, the new? Metabo (Hitachi) M12VC router kit I snagged during Christmas has a really terrible plunge base. The plunge mechanism sticks (not talking about the odd plunge lock; the actual plunge itself), and the depth stop requires really cranking down hard on the thumb screw. Those two gems nearly cost me a cabinet. Grr.

Does anybody near SD want a free 2.25hp router?

I was looking at the css drivers. They are double the price of what I was initially looking to spend but they do seem very nice.

I might be able to swing it but the amp might have to suffer if I go for those drivers.

I have an old 5 channel amp. Could I use this for the drivers or would it not be powerful enough?

https://www.anthemav.com/products-ar...=a5/page=specs

If four of the channels on that amp are available, then just attach one channel per driver. That would basically be like a 500W amp going to a pair. Otherwise, remember that doubling power alone only gets you 3dB in SPL.

[boinger]

Couple more questions.

I am modeling the box size in winisd at 2.09 ft^3 with a qts of .69 is this good?

I understand when applying filters to reduce the signal power to know the max handling, so my question is when the unit is operating how does it prevent overloading the low end if I turn the volume up? Or is it since I am applying a 6db boost essentially that would be the max the amp could output anyway so I wouldn't overload it? I am attaching a picture of what I have modeled.



Last question thoughts on this amp coupled with a minidsp ?

https://www.bhphotovideo.com/c/product/1403415-REG/behringer_nx3000_ultra_lightweight_class_d_3000_watt.html

Also for reference I am currently running a klipsch reference rsw-15 sub which is a 15" with a passive radiator.

I am assuming dual dual-opposed 12's should outperform that comfortably correct?

[Bear]

Try putting the HP/Rumble filter at 10 - 15Hz with a LR4 filter. LR filters are -6dB at Fc, so there will be attenuation well before Fc. Your model is dying at about 33Hz, which is not what you want for a bunch of big subs -- they will be underwhelming (great for EDM, but less great for explosions). I don't use WinISD, but see if you can trace the red line with the blue line below ~40Hz. Remember that in a real room, you will get 6dB or more of lift at 20Hz depending upon placement (E.g., floor-loaded, floor + 1 wall, floor + 2 walls), so the anechoic model at 96dB (red line @ 20Hz) will be closer to 102dB in-room. See about using a lower-Q filter at a lower Fc (try something around 0.6 - 0.7 at 25Hz). Play around to get a starting point, then measure, measure, measure. You may need to counterbalance the lift with a reduction to get things flat in the passband.

On the low pass side, depending upon your main speakers, you don't want big subs going much beyond about 80 - 120 Hz. Try a LR4 filter at 120 - 160Hz for the lowpass. A steeper filter at 200 - 240Hz may work, but I wouldn't go with a B2 that high. On that front, depending upon what the upstream components do, you may need to account for chained filters (e.g., a receiver may have an LR4 filter built into it) when putting the filters into the DDRC. Depending upon your target volume, your main speakers should be able to give you an adequate SPL with between an 80 - 120Hz acoustic cross between the subs and mains.

Behringer and iNukes are very popular for value shoppers. Note that they require a balanced input, which may erode some of their value proposition. I have read some complaints of fan noise, but I have no stick time with any of them.

Dual-12s in a sealed configuration will generally beat a 15" in a PR alignment. The 15 could have a lower anechoic F3, but with a much sloppier step response and a bigger box. If you add the right DSP and enough power, that anechoic F3 advantage goes away. Also, a general rule of thumb is that you 2x the piston volume in passive radiators as you have in the driver. As a result, a pair of 15" PRs will eliminate any cost advantage for the 15" version. And since you are comfortable playing around with WinISD, you can pull data from various manufacturers and see the differences yourself.

PE annoys me in that they insist on measuring Vas in cubic feet, rather than liters, but converting is straightforward. Look at a pair of RSS315HF-8 in parallel vs a RSS390HF-4 with one or two PRs. With 500W, the 12s will give 102dB at 20Hz in about 2.5 - 3cf (72l) heavily stuffed. A single RSS390HF-4 will perform similarly with the same power in the same sized closed box (no free lunch), but it will be mechanically unbalanced and load the room differently. That's not a big deal, but I prefer my subs not to rock when they're Rockin'. Put the 15" in a PR enclosure, you're looking at 150L (net, twice the size), to hit an anechoic F3 in the mid-20s (700g of mass). With room gain, you're flat to a touch boomy, depending upon placement. For scale, a 150L box is about 2' cubed with a fair bit of internal bracing plus driver volume reducing the net internal volume. I wouldn't want to use those 15s much above 80Hz at the absolute max, though.

Take this with a grain of salt. Measuring low frequency distortion is hard, but Zaph knew what he was doing. Also, this is now more than a decade old. However, here is a distortion plot on the RSS315 from ZaphAudio to provide context...

http://www.zaphaudio.com/tidbits/

(I'm not going to increase Zaph's bandwidth in retirement, hence embedding it here)

[CraigJ]

On an unfortunately related note, the new? Metabo (Hitachi) M12VC router kit I snagged during Christmas has a really terrible plunge base. The plunge mechanism sticks (not talking about the odd plunge lock; the actual plunge itself), and the depth stop requires really cranking down hard on the thumb screw. Those two gems nearly cost me a cabinet. Grr.

Does anybody near SD want a free 2.25hp router?

.

Hi Bear,

Here in “rust country”, I’ve had good luck using some type of dry lube on the plunge “arms” of my M12. Turns a jerky plunge into a smooth plunge, at least for me. If I remember correctly, my thumb screw for the depth stop on my model is pretty big, so it is fairly easy to put some torque into it.

Good luck as it should be a fantastic router,

Craig

[boinger]

Something like this? I removed the highpass filter altogether and it stays below the red line.



The driver FR says a lower limit of 16hz don't we want to protect the driver below that frequency ?



This is my cabinet design going to be 14.5 x 14.5 x 24.5 with 1.5" thick baffles.

Does the bracing look adequate?

Also any point considering a ported dual opposed build? Or unnecessary?

[JonMarsh]

Nice looking box design, what material do you intend to make the braces out of? I'd go with something stronger than MDF, and if so, looking good.

If you want you bass transients to start and stop on a dime, without any extra fat, I would generally say go sealed and with power and EQ. Ported will require a larger enclosure, because unlike sealed, you can't EQ below the box Fb for LF extension.

[Andy_F]

I could recommend the "Almighty Subwoofer" which utilises a 15" JBL driver in a band pass ported enclosure.

It is sufficient enough to rattle away tooth fillings and is very punchy for a 15" sub.

Sent from my SM-N950F using Tapatalk

[Bear]

Hi Bear,

Here in “rust country”, I’ve had good luck using some type of dry lube on the plunge “arms” of my M12. Turns a jerky plunge into a smooth plunge, at least for me. If I remember correctly, my thumb screw for the depth stop on my model is pretty big, so it is fairly easy to put some torque into it.

Good luck as it should be a fantastic router,

Craig

Thanks! I'll grab some graphite or similar and try that on the rails to see if it helps. Given the amount of residual lube on the motor housing (messy!), maybe someone put the right stuff on the wrong part.

[boinger]

Nice looking box design, what material do you intend to make the braces out of? I'd go with something stronger than MDF, and if so, looking good.

If you want you bass transients to start and stop on a dime, without any extra fat, I would generally say go sealed and with power and EQ. Ported will require a larger enclosure, because unlike sealed, you can't EQ below the box Fb for LF extension.

I am planning to do the entire build in 3/4" Baltic Birch. I like quick bass myself so I think I will stick with sealed then. I have ordered the CSS sdx12 drivers, now time to start getting the wood ready.

Now I just need to decide whether I stick with the Amp I have already or order a "pro" type amplifier.

Also just to confirm if I wire 2 CSS subdrivers in parellel they are 4 ohm each so in essence I will make them a 2 ohm load to the amplifier correct? So I should look for one speced accordingly?

[Bear]

Something like this? I removed the highpass filter altogether and it stays below the red line.
[..]
The driver FR says a lower limit of 16hz don't we want to protect the driver below that frequency ?

There's very little content below ~18Hz, even with explosion effects. If you have the capability (e.g., the DDRC), you can look at something like a LR8 at 10Hz, and that should keep everything nice and tidy. Unlike smaller drivers, a well-made sub should survive being bottomed-out without damage if you only do it a few times.

This is my cabinet design going to be 14.5 x 14.5 x 24.5 with 1.5" thick baffles.

Does the bracing look adequate?

Made out of Baltic Birch, this should be a good design. If you want to simplify the build, you can just cut some 2" strips for bracing, instead of two large, interlocking pieces. However, if you are going to miter the corners of the exterior skin, then the interlocking braces will significantly help glue-up, especially if you put dadoes down the center of the sides. One thing that CSS does which ought to be more common is to provide the driver volume on their spec sheets. Definitely account for the driver volume and bracing when you are calculating the net volume.

Also any point considering a ported dual opposed build? Or unnecessary?

Again, and as Jon indicates, it's dependent upon your goals. If you want the loudest possible explosions for the least amount of input power, and least amount of input money, then ported is the way to go (e.g., Marty). Your box size will increase substantially, though (e.g., Marty). If you have the input power and EQ, then stick with sealed. Jon had a bandpass subwoofer design a little while ago using an 18" pro driver, if I recall correctly. That's also a great way to go, if your design criteria leads you that way (e.g., large box is okay, and you don't want to spend a lot of money on EQ).

I am planning to do the entire build in 3/4" Baltic Birch. I like quick bass myself so I think I will stick with sealed then. I have ordered the CSS sdx12 drivers, now time to start getting the wood ready.

Now I just need to decide whether I stick with the Amp I have already or order a "pro" type amplifier.

Also just to confirm if I wire 2 CSS subdrivers in parellel they are 4 ohm each so in essence I will make them a 2 ohm load to the amplifier correct? So I should look for one speced accordingly?

Check with CSS, but if you limit the input power to something Not Absurd, then you can probably just use 1 voice coil per driver. However, given the XBL2 motor, this may not be desirable. If you use the Anthem amp, then just wire the two drivers individually to channels on the amp. The same goes for the Behringer amp you posted earlier. A home-oriented amp that handles 2 ohm loads is not common.

[boinger]

There's very little content below ~18Hz, even with explosion effects. If you have the capability (e.g., the DDRC), you can look at something like a LR8 at 10Hz, and that should keep everything nice and tidy. Unlike smaller drivers, a well-made sub should survive being bottomed-out without damage if you only do it a few times.

Ah okay this should put my worries at ease. I just didn't want to damage the drivers I don't have the minidsp ddrc version I just bought the regular, is the ddrc worth the extra cost?

Made out of Baltic Birch, this should be a good design. If you want to simplify the build, you can just cut some 2" strips for bracing, instead of two large, interlocking pieces. However, if you are going to miter the corners of the exterior skin, then the interlocking braces will significantly help glue-up, especially if you put dadoes down the center of the sides. One thing that CSS does which ought to be more common is to provide the driver volume on their spec sheets. Definitely account for the driver volume and bracing when you are calculating the net volume.

I am planning to CNC all these panels out.

I built a CNC for myself late last year, this will be my first big project I am going to be putting through the paces on it.

My internal measurements of the final design are 14 x 14 x 21.5 which gives me 2.438 cf -.2cf per driver and -.1cf total for bracing which gives me 1.938 cf for a qtc of .708. I think that's everything I should account for?

Check with CSS, but if you limit the input power to something Not Absurd, then you can probably just use 1 voice coil per driver. However, given the XBL2 motor, this may not be desirable. If you use the Anthem amp, then just wire the two drivers individually to channels on the amp. The same goes for the Behringer amp you posted earlier. A home-oriented amp that handles 2 ohm loads is not common.

Will do, I will probably just use the anthem for now and maybe invest in the ddrc if you think it is worth the added cost. Maybe at a later date I can add more power if I need it. The anthem amp is just sitting in storage anyway so should be fine with that for now I am hoping.


Latest filter modeling.



Parts laid out for cnc

[Bear]

Looks good. I'm jealous of your CNC! You may want some cheaper materials (e.g., MDF) to train your controllers/head unit if you haven't already done it. It's been a long time since I hung out on CNC Forums, though, so largely ignore me on this. That was a project that basically died when my twins were born. The piece parts look great, and the whole thing ought to come together very quickly. If you need it, you can stuff the heck out of the internal volume (~1.4lb/cf) with Dacron, long-fiber wool or AcoustiStuff.

[boinger]

Quick question should I bother waiting to cut holes for the subwoofer drivers until I get them? Or just go for it?

And any point to countersink subwoofer?

[Bear]

Quick question should I bother waiting to cut holes for the subwoofer drivers until I get them? Or just go for it?

And any point to countersink subwoofer?

From an audio performance standpoint, there's no point in countersinking a sub. In my view, it just looks a lot nicer with the counter sink.

As far as holes, ff you take the extreme size in a spec sheet (Good ones will give an error spec like +/-0.5mm or similar) and then add 1 - 2 mm, things tend to work out. I have had to hammer a tweeter into a cutout before (very carefully, obviously), and I've pooched the conversion from metric into Jasper Jig. That being said, your absolute easiest path is to take your existing design, and then create an overlay/outer baffle out of 1/2" (12mm) Baltic Birch. If the hole isn't quite right, then cut another one. That will save you from having to have a more complex tool path that requires a longer run time for the baffle (1 - 2 layers of 18mm with just a through hole, then an outer layer of 12mm sized for the frame diameter). Depending upon your aesthetic and finishing strategy, the outer layer would also make it easier to build grills for the drivers.

Some options on the grill idea:
1) Embed some small neo magnets on the outer layer of 18mm at the corners and the inside of the 12mm layer. Cover the 12mm layer with grill cloth. Tidy and hidden, depending upon your luck/skill with stretching the cloth.

2) Moderately more elaborate: cut a much larger hole in the 12mm layer (~1 - 2" larger diameter), and glue up as normal. Then cut an inner ring that's sized to be a decent, but not snug fit inside the larger circle. Cover with grill cloth so that the fit becomes tight. Add a discrete pull tab for removal.

For me, these are all theoretical. I like looking at my drivers. :-)

[CADman_ks]

...

Some options on the grill idea:
1) Embed some small neo magnets on the outer layer of 18mm at the corners and the inside of the 12mm layer. Cover the 12mm layer with grill cloth. Tidy and hidden, depending upon your luck/skill with stretching the cloth.

...

For me, these are all theoretical. I like looking at my drivers. :-)

I used option 1 when I built my sub. The neo magnets in the cabinet are under a 1/32" layer of veneer, so you can't see them at all, even when the grill is off. That part didn't work bad. I then used opposing poles in the grill, and wrapped the whole thing.

I never weighed my grill, but one thing that I was surprised at, was the lack of "sticktion" between the grill and the cab. I used some 1/2" x 1/8" neo's, and I don't know what the holding power of each one is, but we use them at work to hold up some pretty heavy stuff, and when two of them are stuck back to back, they are very very hard to get apart with your fingers. So, I thought that I would be good to go. Don't get me wrong, the grill hasn't fallen off, but it doesn't exactly "snap" on there either. As far as I know, it has never moved down either, so it's holding tight. I think that the magnet idea works good, it just didn't work as good as I thought that it would.

YMMV...

[Steve Manning]

I've used buried magnets on several occasions, typically ~ .10" bellow the surface of the baffle. This place has a great selection, https://totalelement.com/collections...Diameter_3%2F8. I've used the 3/8" X 3/16" and typically doubled them up since I had plenty, next time I'll just go for the 3/8" X 3/8". Anyway, they hold the grills extremely well ..... here's a few pictures.

[Bear]

And so that I'm not accused of being completely "all hat, no cattle", here is my second dual-opposed sub:

https://www.htguide.com/forum/showthread.php?44513-Helios-mk1-A-cautionary-tale&p=638139&viewfull=1#post638139

Both are repurposed out of my original Helios cabinets (the first was much smaller because of an inability to get square cuts...). Once I get the third one built, then Home will be decommissioned. The drivers (SW223BD03) will be used elsewhere. Or maybe not. We'll see. That's a ways into the future.

[TEK]

Just curious, as I did not see it when scrolling over your thread (might have missed something).
What are your goals for the sub?
Are you focusing on movies and high SPL as well as earth moving experience, are hou or more into music and high quality with the best possible accuracy?

As in everything else, building a sub is about wheighting different pros and cons against each other, and what is pros and cons depends on your goals and planned usage.