Small 30Hz Sub

[mrgarth]

My first post here, for my first DIY project. I've been reading posts on the site with interest for a month or two and I'm admittedly new to this, so I make this request with some humility and respect for the skills you all have, and I know how much I don't know.

I'm posting a question similar to Zwiller on a Smallish 30 Hz PA, but where I didn't see a conclusive answer.

Here's my project:

I would like to build a pair of subs for a portable sound system for my wife and I to do some small parties, DJing bass-heavy electronic music. This will mostly be for outdoor use, so not worried about room response or placement.

I'm looking for subs that can do around 110 dB SPL at 20 feet, flat to 30 Hz - i.e. something suitable for small (20 to 50 people) dance parties outdoors. I don't need "blow your shirt off" SPL; clean/clear response is more important. I find this is putting me in a bit of a gap between "pro" PA systems, which are usually more powerful than I need, and installed systems for bars/clubs, or even home theatre type stuff which may be lower power but usually not small enough to be portable.

To preclude responses of "if you're OK with 40 Hz response instead try this", here's a scan of the type of music I'm interested in playing (deep dubstep, dub, drum and bass, techno, etc.) - noting that response at 30Hz is important, so no compromises there.

I will be building two of these, so estimates for SPL / response can account for two subs side-by-side.

I currently have a pair of Peavey sd 5g for full range tops (rated 250W RMS, 500W program, 8 ohms), and I have a DCX2496 management system for crossover, EQ, etc. which gives me some ability to EQ my way out of using enclosures that are not quite flat to 30Hz...

Let's say that I'll cross over to subs at 90 Hz for the sake of argument, but I'm open to advice here depending on what subs I end up with.

Here are my parameters / decision criteria for sub designs:

- small enough that my wife I can carry them up and down our basement stairs; ideally a 50kg limit (loaded), and fit two a Toyota Matrix with the seats down (I know this may not be possible... so it's "nice to have" and I definitely understand that "30Hz" and "small" don't necessarily go together if I also want some power)

- I have a friend and neighbour with advanced woodworking skills and the shop/tools to do the build, so advanced designs are fine if that's my best option.

- I'm willing to consider paying a premium for higher power and performance from drivers/amps in order to have the smaller size; that said, preference is for drivers I can easily get in Waterloo, Ontario, Canada. I live nearby a distributor (Canada's Largest Inventory of Celestion, B&C and Eminence speaker drivers.) of Eminence, B&C, and several other brands... however other designs close to what I'm looking for have called for high Xmax drivers by Beyma and Faital Pro and these are not as readily available here from what I can tell.

- I would consider also building kick bins if I need to, but would like to avoid the complexity of a 3 way system if I can.

My current contenders for plans are:
- The X1 - possibly larger/overpowered for what I need, but looks close
- Cubo Sub - also possibly larger/overpowered for what I need, but looks pretty close. I initially thought Cubo 15 extended + Cubo kick would be right, but now I think it's probably overkill.
- I quite liked Chris' Teeny Tiny 15"
, but it doesn't quite have the low end extension I was looking for.

I got hooked on the idea of DIY after seeing my friend Jay Michael build a set of othorns... but that's far beyond my needs!

Your feedback is most appreciated

Garth

 

[kipman725]

20ft is 6m so if you look at the systems on data bass (2m results) you need >120dB@30Hz for your spec. A pair of high end >18" drivers should easily do this in sealed boxes while fitting in your car. You will also need a very powerful amplifier.
Two of these would probably be the smallest option:
dB v2
very very expensive...
I would recommend incorporating heat sinks into the box design, sealed boxes get hot doing PA.

Another more practical option would be a pair of small vented boxes:
dB v2

 

[David Morison]

Don't think they sell Toyota Matrix's over here so I've no idea how big that is, but if you're saying that you can fit two X1's in there (plus all the other kit - mid-high speakers, amprack, playback/source systems, cabling etc) then you've got quite a lot of space to play with.

An X1 will come in well over 50kg though, even with a neo driver. There's about 47kg just of timber in the build (assuming 0.7g/cm^3, about the heaviest estimate I've seen for the density of birch ply). The Cubo sub won't be much (if any) lighter.

So your options are 2 somewhat smaller boxes, or 4-6 even smaller ones - Chris's TT15's are approximately one third the size of an X1 each after all.

The good news is that 2 single 18's built down to <50kg or 4-6 single 15's can achieve the SPL/frequency extension you're after, and B&C in particular produce some very suitable drivers for doing it.

So, what's your preference in terms of box count/size/weight/driver complement first of all please?

Cheers,
David.

 

[mark100]

Ditto to the comments that say your goals are realistic and fairly easily attainable...

I built a pair of simple 18" vented using bms 18n862, based on Ricci's DIY..dB v2

Mine are slighty larger boxes than his, tuned f3 at 30Hz....and weigh about 41kg.
Couldn't be happier with them..

Don't know if sourcing might be problem though, given your comments about Beyma and Faital. Have you checked out Lean in the UK or THLP in France?

 

[mark100]

Haha Kipman725.... didn't see your second recommendation !!

 

[Bigun]

Hi Garth,

There is an excellent source for speakers and all the other materials you might need to build something in Waterloo where you can walk in and buy over the counter. Living in Waterloo myself I purchase from these guys before and have found them to be very good.

Located in Waterloo, Ontario Q Components is a online retailer of loudspeaker parts and accessories.

rgds
Gareth

 

[Circlomanen]

Response of two tapped pipes in 2,0 Pi.

A pair of simple tapped pipes with a B&C 12TBX100 will fill your needs quite nicely.
I estimate that there is 2,2 m2 plywood in each box. 2,2 x 15 x 0,7 = 23,1 kg for each box if built out of 15 mm birch plywood. With driver and some bracing you should hit 40 - 45 kg a piece.

The tapped pipe has a small low Q peak around 80 Hz which will accentuate the midbass punch a little.

80 x 49 x 36 cm outer dimensions.

 

[mrgarth]

Thanks for these quick and thoughtful responses. I had not yet seen any of these three suggested designs - and tapped pipe as a category was completely new to me and I looked up a page (The Subwoofer DIY - Projects : A "Proof of Concept" tapped pipe) to better understand it.

To answer the clarifying question posed:

So, what's your preference in terms of box count/size/weight/driver complement first of all please?

I would consider up to 4 boxes, I think, but 2 is preferable. That mostly comes down to a question of expense.

The tapped pipe is looking like my favoured option at the moment for simplicity and cost, but I'm going to make some paper models to scale so I can actually get a better feel on size—I'm visual that way and need to see things 3d to really get my head around it.

I will have to actually measure the back of my car but it's a compact model, 4 doors with a hatch back. I can lay down the back seats, though, and then it's comparable to, if only slightly smaller than, a light pickup truck with a low cap on the box.

Garth

 

[tommus]

Flat to 30hz is really pretty low for typical PA, which is why you see most portable PA subs tuned to 40-ish Hz. However if you get down there it sounds wonderful. My reference is the Othorn, but that's enormous. If you hear one you will know immediately what most PA subs lack. BTW there is a difference between a box "tuned" to 30hz and a box that is "flat" to 30Hz. You probably want a tuning of 25-27hz to get the extension you want. Othorn is 27Hz if I remember correctly.

A reflex cabinet that will get you down flat to 30 is going to be large, and you will have little freedom to bump the low end because the driver can't handle much below the tuning frequency, also you have a steeper 4th order roll-off anyway.

I just built a sealed sub with a Dayton Ultimaxx 18 in an approx 6ft (net) cabinet. Powered with the Dayton SPA1200 plate amp. This driver has 22mm of Xmax but it is heavy. Heat buildup will be a problem eventually if you run them hard, but I think 2 of these would be good for your situation. What is nice about the sealed subs is you can EQ them as low as you want (to the excursion limit) for different SPL levels. Also the slow roll-off gives you some deeper boom to the low 20's. Most "pro" sub drivers I've seen have an Xmax of 12-15mm because they are made to be used in a vented box, and they are very expensive because they have neo motors with huge power handling specs, and they are optimized for the 40+Hz range.

If you are outdoors, will you be close to a wall or corner? Some boundary reinforcement is nice. And of course put the subs right next to each other, not one under each main.

 

[tommus]

Kipman, can you point to some heat sinking for sealed subs? Are you talking about a finned aluminum plate set into the cabinet wall?

 

[Bigun]

Here’s a very simple calculator for looking at the cone excursion, it may be a little too simplified but it’s a cool starting point

Piston Excursion calculator

 

[kipman725]

Kipman, can you point to some heat sinking for sealed subs? Are you talking about a finned aluminum plate set into the cabinet wall?

I haven't seen it done before so can't post any pictures. However I have had problems with heat build up in my sealed PA cabs. When you touch the (metal) handles you can feel the air inside the cab is very warm after a few hours operation. This causes the effective motor force of the drivers to go down and the system to lose bass weight over time. However if the cab had significant portions made of aluminum the air would not get as hot inside. Sound damping materials should also be avoided as they are not required (box quarter wave modes are above bandwidth of sub for small sealed cab), reduce efficiency and insulate the box.

Another idea for a sealed cab would be to port it! using ports that are very low tuned and of small diameter then use fans on these ports to circulate air.

When a very high BL pro driver is used in a sealed box the box size requirements become minuscule as electrical damping dominates which is why I suggested sealed boxes if the only objective to maximize output for the physical volume of the system.

I'm of the opinion though that the easier solution would be to use some sort of vented alignment as air naturally circulates in such boxes. They are also more efficient which becomes important when you want more subs as you start to run into electrical power limitations.

 

[waxx]

I think a tapped horn will be the best also to get that low outside.

A sealed enclosure going so low is almost impossible outside (needs a massive ammount of eq, and a lot of xmax, so a big driver). And vented will be too big for your requirements. I did try the same for someone with a Faital Pro 18FH500 driver and i came to a 350L vented cabinet for a 30Hz tuning, wich got 117dB output when fully driven (600w). That is more or less the same size as a classic scoop horn like used in many reggaesoundsystems (60x68x100cm) and wiil weight a lot (more than you want). For the owner for who i designed it it was perfect for his garden soundsystem (he lives remote in the woods with no neighbours) and they do sound very good in that application. The tops are Fane 12-250TC's in a closed box btw.

I've seen tapped horns with a 12" driver (Lab12) that go that low and loud, and that are half the space and probally also half the weight... But i have no plans or am an expert in those.

 

[mark100]

I think a tapped horn will be the best also to get that low outside.

A sealed enclosure going so low is almost impossible outside (needs a massive ammount of eq, and a lot of xmax, so a big driver). And vented will be too big for your requirements. I did try the same for someone with a Faital Pro 18FH500 driver and i came to a 350L vented cabinet for a 30Hz tuning, wich got 117dB output when fully driven (600w). That is more or less the same size as a classic scoop horn like used in many reggaesoundsystems (60x68x100cm) and wiil weight a lot (more than you want). For the owner for who i designed it it was perfect for his garden soundsystem (he lives remote in the woods with no neighbours) and they do sound very good in that application. The tops are Fane 12-250TC's in a closed box btw.

I've seen tapped horns with a 12" driver (Lab12) that go that low and loud, and that are half the space and probally also half the weight... But i have no plans or am an expert in those.

Interesting to see you tried to use the 18FH500 that low, because i have a little side project going on with it right now.
I'm trying to make the lightest sub possible, so I chose the 18FH500 due to it's 4.6kg weight for a bass-reflex try. I've settled settled on f3 at 45Hz, because it seems when I try to increase box size to get lower extension, it comes at the expense of diaphragm displacement limitations in the 50-90 Hz range. Going by Hornresp's 'Maximum SP'L tool, which I hadn't used till this sub try. Box is now 160L.

Anyway, my point is not to propose that Garth raise f3, but to say with the right driver an 18" BR will work within his goals. Just repeating my vote for what worked for me, the 18n862. I went back and applied the Max SPL to the f3 30Hz boxes I built with the driver, and found I was plain lucky and have balanced limitations through its 30-100Hz intended range.

I don't have experience with tapped horns either....
I totally agree a sealed has no real chance...

 

[kipman725]

To all those saying that sealed has no chance, the measured results on data-bass show that it would meet spec, using two small boxes. Its just expensive in drivers and amplifier power required.

This cab is 173L external volume and hits 115dB@30hz@2m with the amplifier limiting. Use two and you get 121dB which meets spec. dB v2

 

[mark100]

To all those saying that sealed has no chance, the measured results on data-bass show that it would meet spec, using two small boxes. Its just expensive in drivers and amplifier power required.

This cab is 173L external volume and hits 115dB@30hz@2m with the amplifier limiting. Use two and you get 121dB which meets spec. dB v2

You made me check it out Wow!
And yikes, I see what you mean..... $2500 msrp, and crazy power needed.

I also see it weighs 70lbs. Part of the OP's spec was 110lb loaded.
Could a box for it come in under 40lbs...???

I have to stick with sealed having no real chance, certainly if pragmatism comes into play..

 

[waxx]

To all those saying that sealed has no chance, the measured results on data-bass show that it would meet spec, using two small boxes. Its just expensive in drivers and amplifier power required.

This cab is 173L external volume and hits 115dB@30hz@2m with the amplifier limiting. Use two and you get 121dB which meets spec. dB v2

I don't think this fits the goal of the OP, and that is what we are talking about. There are more ways to still have that, even a lot cheaper and with less power. But those speakers are big and heavy, past the limitations of the OP. And his budget and amp power won't stretch this far to make this work i think...

 

[waxx]

Interesting to see you tried to use the 18FH500 that low, because i have a little side project going on with it right now.
I'm trying to make the lightest sub possible, so I chose the 18FH500 due to it's 4.6kg weight for a bass-reflex try. I've settled settled on f3 at 45Hz, because it seems when I try to increase box size to get lower extension, it comes at the expense of diaphragm displacement limitations in the 50-90 Hz range. Going by Hornresp's 'Maximum SP'L tool, which I hadn't used till this sub try. Box is now 160L.

Anyway, my point is not to propose that Garth raise f3, but to say with the right driver an 18" BR will work within his goals. Just repeating my vote for what worked for me, the 18n862. I went back and applied the Max SPL to the f3 30Hz boxes I built with the driver, and found I was plain lucky and have balanced limitations through its 30-100Hz intended range.

I don't have experience with tapped horns either....
I totally agree a sealed has no real chance...

I can tell from measurements that the box i designed and he build is going down to 30Hz more or less flat with the amp he uses (a 300w custom tube amp) without cone breakup. A bit above you start to lose low due to the overexcursion.

But for his gardenparties (max 100ppl with roots and dub music) in the summer, that system (2x 300w tube amps on subs and 2x150w tube amps on tops) is loud enough. We don't need those extreme volumes that most roots and dub systems have, we want a good sound and a deep bass and this simple 2 way system delivered that on the 3 parties he did this summer. When testing his total system in open space we measured about 106dB on 10m distance in open air while testing on max volume of the amps. I also played on it (i'm an old reggae soundsystem selector) and it was a joy to play with...

And most of the time, it's just the music for him and his family and guests when they are in the garden and the volume is even lower (more background music).

Edit: i just checked the specs again of that woofer, and the Xmax is 9.5mm, but the xdamage is 17.5mm. So you can go further than the 9.5mm. I know from experience that 10-15% over xmax is not really a problem for a woofer, and mostly not hearable. So i think your calculations are not right. And WinISD says that for 9.5mm, you can pull 220w to it before it goes over xmax. Wich explains my experiences with the box that i designed...

 

[David Morison]

So, I'm far from an expert, but it seems to me that a couple of decent 15's in conventional vented boxes can do what OP needs if Circlomanen's tapped pipe doesn't end up being chosen.

Granted, this is modelled in WinISD so no semi Inductance etc, but as Le is moderate it should be OK.

Drivers are B&C 15BG100 each in 124litres net tuned to 31Hz. Drive level after processing is 63V or approx 950W into 8 Ohms, well within the driver's power rating.

Vent is sized for 20ms^-1 at the stated drive level - not quite hi-fi low but should be ok for the stated use.

Overall box size is 450 x 650 x 650 mm and there is about 27kg of timber in each, plus 8.6kg of driver. So even if grilles, handles, adhesives, screws, paint, wiring etc weigh several kg each will still be well under 50kg.

If more SPL is needed, the manufacturer does give an "Xvar" spec that is 30% higher than the Xmax for this driver - presumably linearity won't be quite so good in that region and airspeed would go up too but it is another couple of dB of potential output.

If size is still an issue, the box could be made smaller, at the expense of needing more EQ to flatten the response - it would also result in a much longer vent, more like Chris G's TT15's whereas this is pretty simple to build - no angled cuts for example.

FWIW,
David.

 

[mark100]

Edit: i just checked the specs again of that woofer, and the Xmax is 9.5mm, but the xdamage is 17.5mm. So you can go further than the 9.5mm. I know from experience that 10-15% over xmax is not really a problem for a woofer, and mostly not hearable. So i think your calculations are not right. And WinISD says that for 9.5mm, you can pull 220w to it before it goes over xmax. Wich explains my experiences with the box that i designed...

It's encouraging to hear the success you've had with the 18FH500...

I may be making a mistake with Hornresp...like I say, I've just begun using the Maximum SPL tool. But it seems pretty straightforward....dunno.

Anyway, below are the Max SPL screens for both 350L tuned to 30Hz, and 160L tuned to 40Hz. I used 12mm xmax.

These comparisons are what led me to the 160L build. I'd love to find out if I'm looking at it wrongly...or rightly..

To OP, apologize for the swerve...tell me to start another thread if you want...no prob.

First one is 350L.