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DIY Dual 18" Ultimax - Captivator S2 style

mandragora78

Active Member
Hello All,

I've been lurking around the DIY subwoofer thread for a while now and I've finally decided to go ahead and take of my first DIY project.

I've exchanged few emails with @Ringnut already and he made some suggestions already but I would like to gather a wider set of opinions :)

What I'm after is building something similar to the captivator s2, so a dual driver with vertical driver placement.

Do you guys think that is feasible ? would it be more appropriate/easy to just build two single and stack them?

Component wise those needs to be available here in the UK and unfortunately I don;t have skills to build the cabinet so I'll definitely ask help of people like Gordy :)

So in regard to driver and amp having had a look around my choice are falling to :
  • Dayton Ultimax UM 18-22
  • Crown XLS 2502 or similar

What do you guys think ? any suggestion and/or advice ?

Thanks a lot for all the help,

Ben
 

Ringnut

Distinguished Member
Undersrood and thanks for the tip :)

For the single box is it enough just to contact Gordy asking "I would like to have a box suitable for an Ultimax 18 with a hole on the back to fit a speakon connector like Neutrik NL2MP 2-Pole Speakon Chassis Socket"

would be as simple as that ? :)

'Fraid not, to the best of my knowledge he isn't an AV follower, just a good craftsman. You have to tell him EXACTLY what you want, preferably with diagrams so there's no misunderstanding. ;)
 

mandragora78

Active Member
'Fraid not, to the best of my knowledge he isn't an AV follower, just a good craftsman. You have to tell him EXACTLY what you want, preferably with diagrams so there's no misunderstanding. ;)
:thumbsdow OK understood.

Where I can look for help in designing the cabinet or does exist a place with "open" projects complete with cabinet design ?

I'm sorry but I have no idea where to start with the design of the cabinet .

if I was going to do it myself I would have used the dayton recommended volume for the UM18 multiplied by 2 and created a Parallelepiped with that volume to host the 2 woofers :) ... but i guess is not that simple ... isn't it ? :)
 

Ringnut

Distinguished Member

Ringnut

Distinguished Member
Basically (others may wish to come in here) what you are looking for I'd suggest is a box made out of 18mm mdf with a double baffle (36mm) with a cut out and step for that size driver.

https://www.parts-express.com/pedocs/specs/295-518--dayton-audio-um18-22-spec-sheet.pdf

(Personally I'd wait until you actually have the driver with you in case it comes with a gasket that needs to be taken into account.)

The box needs to have an internal volume of around 4.22cu ft (according to Parts Experss)...

"Dayton Audio UM18-22 18" Ultimax DVC Subwoofer 2 ohms Per Coil" from www.parts-express.com!

Enclosure Volume Calculator - Subwoofer Box Calculator

...but subtract the volume of the driver and any bracing you choose to add. (Do a quick search on "subwoofer bracing" for more info there.)

Read as many build threads as you can as each one will provide valuable insights for when you come to build yours.

You will also need to consider how you are going to power it and I would strongly advise getting a MiniDSP 2X4 to make setting it up that much easier.

All the above IMHO. :)
 

mandragora78

Active Member
...
Read as many build threads as you can as each one will provide valuable insights for when you come to build yours.

You will also need to consider how you are going to power it and I would strongly advise getting a MiniDSP 2X4 to make setting it up that much easier.

All the above IMHO. :)
thank you so much for the help here ... I already own a minidsp so no problem there.
Power wise I was looking at crown xls 2502 as I like the look and have used it in the past .
I'm collating all different information for now but I;ve started to realize that maybe the DIY route won't save me that much.
From a very early estimate I think for a single 18" I'll be looking at just over 1000£ I guess now ... a single PSA S1811 is ~1500£ realistically how much I'm going to save?

probably ~300£ ... don't know if it will be worth it :(

thoughts on this perspective ?

thanks as usual for all help and advice!
 

Ringnut

Distinguished Member
PSA subs are probably the nearest thing to DIY out there commercially ATM. Excellent VFM, very good performance, really helpful owner (Tom) who is always available for help and a very good retailer (Ricky @ Kalibrate). The big advantage of going the PSA route is, should you wish to sell it/them you will get a much better price than trying to sell a DIY sub. :(
 

MattSPL

Active Member
Would you plan to use the crown amp in bridged mode or 2ch mode? Just thinking as it’s rated at 2 x 775w @ 4ohm and might not produce those figures for sub duties. It will be plenty enough to drive the 2 um18’s, but if you plan to squeeze the most SPL from them, it might not quite get there.
 

mandragora78

Active Member
Would you plan to use the crown amp in bridged mode or 2ch mode? Just thinking as it’s rated at 2 x 775w @ 4ohm and might not produce those figures for sub duties. It will be plenty enough to drive the 2 um18’s, but if you plan to squeeze the most SPL from them, it might not quite get there.

Initially just one to save on costs and once funds allows get another one and use them in bridged mode
 

mattkhan

Distinguished Member
Unfortunately I like sealed designs and getting a cheaper driver I fear that won't give me the performances I'm after :-(
1 ported instead of 2 sealed, not a cheaper driver, just fewer drivers, a port and less amp.

Have you heard a well designed ported sub?

Ultimately sealed is not an obvious choice if your main constraint is budget. Similarly ported is not a good choice if your main constraint is space. Pick your trade off really.
 

mandragora78

Active Member
1 ported instead of 2 sealed, not a cheaper driver, just fewer drivers, a port and less amp.

Have you heard a well designed ported sub?

Ultimately sealed is not an obvious choice if your main constraint is budget. Similarly ported is not a good choice if your main constraint is space. Pick your trade off really.
Hey mattkhan thanks for your reply and yes I heard good ported subs, but I already own two sealed subs and integrating sealed and ported is going to be a pain in the neck.
Also space is a key factor for me and the reason why I was considering a design with 2 drivers disposed vertically opposed to for example a dual opposing one.
 

simonb3665

Active Member
A PSA S1811 is very small for an 18 sub, well reviewed,will come with a nice long warranty and you know its been tuned by someone who really knows his business. A twin Ultimax 18 is a very different beast performance wise but will be 8cuft at least and then you will have the external aplification to house too. A single ultimax should be a match for the PSA in the right enclosure which will save money and maybe a cheaper amp to just drive the one.
What is it you are looking for in the sub if you have two already?
 

MattSPL

Active Member
I'm after increasing tactile response with near field subs.
With the two I've got bass response is very smooth, so no lack there. I just want to increase that "chest punch" sensation

I believe subs such as the Jl audio F212 offer more chest thumping bass your after due to the stacked driver being higher up, so you might be onto something. Also though, ported or transmission line seem to produce more trouser flapping, chest thump at the lower levels, whereas the sealed need real spl to get the air moving the same.
 

mandragora78

Active Member
Hello all, I haven't given up (yet :) ) and I'm still looking around for the cabinet.

Looking at data-bass (Data-Bass) they have used for their tests a 22"x22"x22" box to host the UM18-22.

I guess that if I give to gordy those measures with the following references for mounting the driver
Mounting Information
  • Overall Outside Diameter18.24"
  • Baffle Cutout Diameter16.75"
  • Depth9.625"
  • Bolt Circle Diameter17.40"
  • # Mounting Holes8
Those would be enough for him to build me a nice cube where I'll fit the driver.
is it enough?

P.S. those measurements from data-bass are incredible ... :)
 

Ringnut

Distinguished Member
Don't forget to tell him how you want it braced unless you intend to do that yourself afterwards. ;)
 

markymiles

Distinguished Member
triad-gold-subwoofer-internal-bracing.jpg


Something like this? I've seen Gordy make boxes on other people's builds similar. You could make do with one in each direction rather than this many.
 

Ringnut

Distinguished Member
Last edited:

mattkhan

Distinguished Member
IME it makes v little difference in actual use, certainly feels more solid but audible impact is essentially nil (for the size cab we are talking about here and assuming a well built xabinet). Some dowel rods stuck in there as @Ringnut says and move on.
 

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