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Discussion Starter · #1 · (Edited)
Hi from Down Under,
I thought I would start my build thread as I have decided the path I wish to travel after much deliberation, research & advice.

I was trying to decide between 15's or 18's, sealed or ported and have concluded that two Dayton Ultimax 18's in 145L sealed enclosures will be the best for my application.

Of course, when the drivers & exact numbers are released, I will probably have to recalculate a little, but I would imagine they will remain largely unchanged in the basics.

Please have a look at my design drawings and let me know your thoughts. All the details are attached in a PDF file to this thread below. I have also attached the WinISD project file for anyone to have a look at and I am happy to receive any suggestions from more experienced individuals. I have not built DIY before and am new to the MiniDSP and tuning jargon & types. I am not 100% sure about the Linkwitz Transform or even if it is necessary or not for this build, but I would like to know more.

All the details of the project are listed on sheet 2 of the attachment. But I have transposed them below for simplicity sake.

SUBWOOFER SPECIFICATIONS:
Driver: Dayton Ultimax UM18-22
- 18" driver
- 1000W nom. 2000W max

Box: Sealed (~145L)
Materials - 25mm MDF
- Brushed aluminium plate or laminex
- Plastic body filler
- Gloss white spray paint
- 50mm screws

Tuning & EQ specs: (subject to change)
- Using MiniDSP 2x4 with 2.1 plug-in
- Linkwitz transform
f0: 33Hz
fp: 20Hz
- High-pass filter @ 15Hz
TUNING RESULTS: -3dB @ 22Hz
Max cone excursion at 18Hz with 400W
Max SPL: 117dB @ 65Hz
108dB @ 20Hz

Amplification:
- Behringer EP4000
- Both 2 Ohm voice coils wired
for 4 Ohm to amp
- One sub per channel

I will update this thread as I make more progress. Thanks for your support! :T

P.S. I am an architectural draftsman by trade hence the work related title blocks. :)
 

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Looks like a really good plan :T These are going to be monstrous cabinets! Appears thought that you are doing a single baffle the driver attaches to with bracing. Most builds I've seen with MDF use a double baffle. You will gain some rigidity with the outer baffle, but it is indirectly mounted to the driver and you may lose some stiffness there. I would suggest a double inner baffle with the planned bracing. Looks really good.
 

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Looks like a great plan!

I could recommend you to look at IXL-18 Mk2 much higher sensitivity, more Xmax, lower Q in same sized cabinet (more defined sound), less mechanical losses. And you don´t have to wait for it :)

+1 double baffle.

Use some rockwool to make the Q value drop some more and even out temperature peaks in the cabinet. Rockwool fibers facing like I have placed them towards the driver. 50-60% fill would do good.
 

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WOW, thats a detailed plan for sure.

My only question to you is did you ever consider ported subs? You would get more SPL down low but then once you hit tuning it would drop like a rock.

Otherwise it looks quite nice and I am sure you will make it look REALLY good.

If your interested in what a ported box could do, google "Martysub FlatPacks" on AVSForum. They have some WinISD graphs and a breakdown of the box.

Thats what I am shooting for with my Stereo Integrity sub. If all holds to measurements I am looking at 114 db @ 20hz with a single sub and a 1000 watt Dayton SA-1000a amp.
 

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Thanks for that link. Very good info and I agree with all of it actually. I was just making sure the OP had looked at ported as it can provide more SPL at its tuning frequency, however as you stated it drops like a rock and you need to choose the right box configuration as well. Also mostly because the "MartyCube" or "MartySub" design is actually 5 or 6 cubic feet depending on which you use, and its been basically made for 18" subs like the one he's using.

I've seen folks use the 18" Ultimax, 18" Stereo Integrity D18, 18" Dayton HO18 and I will be using a 15" Stereo Integrity D15 in one of the smaller MartyCube's....
 

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Yes ported could work in smaller cabinets with slotport but the Ultimax is not a very good choice for linear respons in 5-6 cft ported.
I managed to fit a 20-21Hz tune in 85liters with the CSS SDX12 but longer vents won´t fit. If I had built them today I would have chosen slotport instead but I´m a fan of having options so I build with the possibility to seal the cabinet.
 

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Discussion Starter · #8 · (Edited)
Yes I have looked at vented for the same 145L boxes. See the Transfer Magnitude graph below showing both sealed (blue) and vented (grey) and wpr file attached for vented (sealed file is in the OP). If you have a look at the SPL graph in the winisd file you will see that yes I will get more SPL out of it, but less LFE. The real facts are that I won't be playing at reference levels, and so LFE really is what I am looking for.

TM graph:


SPL and Cone Excursion graphs:



SPL's:
Sealed ~109db @ 20Hz and ~93db @ 10Hz
Vented ~112db @ 20Hz and ~88db @ 10Hz
(add 6db for two of them)

However it is very tempting to go ported when I see 120db @ 50Hz (x2=126db) for vented but only 113db @ 50Hz (x2=119db) for sealed. Makes me feel like I am missing out. And to be honest, I don't know how much I "need" much loud volume below 20Hz. But I do have to remind myself that the facts are that we would probably never actually play anything at 126dB, so it is best for me to focus on low frequency extension below 20Hz.

I don't fully understand the whole Linkwitz Transform thing yet. It seems to make the graph look great for extension, but I have to put in a high pass filter at 15Hz otherwise driver excursion skyrockets like a vented box. Also, the driver achieves full excursion at only 400W. When with the vented box it takes 1400W to reach xmax. I must admit I need to learn more about this.
 

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