Another DIY sub, this one a trapezoidal enclosure x 2.

Johnny.G

Active Member
Already using two svs subs in dedicated room but after being converted by Swiftpetes two 18" cylinders have decided to go diy instead of commercially upgrading . Was going to do cylinders but just can't intergrate them into the available space of the room. Example of build can be seen on Hometheatershack site under "Enclosure Volume Calculator".
Fairly accurate shopping list costs below for anybody contemplating something similar.

5 sheets 25mm mdf ..................................................... £146
12 mtrs 14 oz fibre fill wadding ...................................... £36
2 Fi Q18 D2 drivers .................................................... £680
3mtrs 6" soil pipe ....................................................... £32
4 x 60 wood screws .................................................... £12
Wood glue ................................................................. £12
2 recessed speaker binding posts ................................... £16
1 Behringer EP4000 ..................................................... £ 247
2 18" speaker grill covers (if used) ................................. £16
2 6" speaker grill covers for ports (if used) ...................... £10
Primers and paints / coverings ?? ................................... £20
Total in the region of £1227.00.

Will be using existing Antimode.
My Joiner friend and i have done some constructing today, will post up some pics when i remember how to do it !.:)
 

Johnny.G

Active Member
the new site for the two new enclosures are along the back wall behind the sofa, the majority of the enclosure concealed behind with just the two drivers exposed at each end of the sofa.... more pics to come of the construction
 

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Johnny.G

Active Member
room stripped a bit , easier to see where they will fit..
 

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Johnny.G

Active Member
First stage of construction, waiting for a few more bits
 

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Johnny.G

Active Member
Both part built enclosures side by side more or less as they are going to be when snook behind the sofa :D
 

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Johnny.G

Active Member
assuming iv'e done the calcs right with the bracing Pete, i recon the internal cabinet volume as it is will be in the region of 12.8 cubic feet / 362.6 litres. The cabs as seen, basically are built as to stretch from one side of the room to the other at the back of the sofa with virtualy no gap in the middle. The actual internal volume of the cab can have another internal wall built in to reduce the total volume if required, need guidance here from Dan and yourself . I,m going to build them ported with the port exit flare on top of the cab near to the driver end (imagine the driver placed to the extreeme left of the left hand cab and the extreeme right of the cab on the right hand cab. I should be able i think, to use the 6" port tube you gave me , with a clearance of 6" from port entrance to cab bottom to give me a tune of around 15.5 - 16Hz tune. It will be so easy to bung or remove the port in that position to go sealed at a later date if required. Shouldn't be too long now before the Q18 arrives. :smashin:
There was no way i could intergrate two large cylinders in the available space Pete, colliding with the rears etc .... this design means the angled slope of the cabs matches the angle of the sofa, dosn't come up any higher than the sofa and the top of the cabs are just the right height for resting the pint pot on!.
 

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Member 639844

Former Advertiser
Unless you seriously limit input power (like limit it to 250 watts), a single 6 inch tube isnt sufficient. 2 of those vents will work, but if you want a 15hz tune they need to be 1500mm long. A slot port may be a better solution for porting them.
 

Johnny.G

Active Member
Thanks for the input Dan, to be honest i think i am going to need a dig out with getting the correct design info from Winisd. Iv'e had an attempt with it but not 100% sure i'm on the right tracks, think i will need to go up to 200mm for a single port tube and aim for a port tune of around 16 to 17Hz, and remind me please what the ideal 1st port resonance figure needs to be when modeling different configurations. The input figures that are shown on the enclosure calculator pic are the ones that i will be working to.
 

Member 639844

Former Advertiser
The enclosure diagram does not show input power.

The calcs I did though were based upon 326 litres empty cabinet volume. What is this figure? Dont forget, larger diameter tubing will need to be longer.

Air speed needs to be no higher than 30 m/s and first port resonance ideally wants to be a good 50hz or so above the working range of the sub. If you only plan to run it to 80hz, then you can get away with about 130hz lowest, if you want to run it to 120hz, then 170hz would be the lowest resonance. You can cut it closer if you like but those are the figure I work too.
 

Johnny.G

Active Member
Might have confused you there with the word "input", would have been less confusing if i had said "amounts entered in enclosure details" boxes etc. I can still at this stage of the construction, fit an extra internal wall inside the enclosure to the opposite end of the driver to tailor the total enclosure volume to a desired amount if required. They could end up being sealed in the end but if i have read correctly some where, i think the internal volume will need to be reduced a bit, advise me on that if you would Dan please. The reason for building ported was to give me the option to easily bung up the port and listen to them sealed once built.
Thanks for the info .... I'll go away and have another play with the numbers and see what i can come up with.
 

Member 639844

Former Advertiser
The Q drivers like large cabinets, so even with 350 litres they will run sealed ok. However, I think that 250 litres is about right for one of these drivers. With a pair running they can take max power all day long and never hit xmax, and you get a nice balance of upper bass punch and good clean depth to high spl's.

Your cabinets are fine and your in a good position to play around with things and experiment. Reducing internal volume can be a simple as placing solid blocks (of known volumes) inside the cab to displace some of the internal volume. You can then happily run sealed at their max size, and reduce the volume of the cabs at any time with no real work involved. Keep the size as large as possible for the ported versions, for the sealed fell free to play with anything from 150 litres to 350, and observe the change in character, then settle to taste.
 

Johnny.G

Active Member
Thanks for that info Dan, .... ive been reading the Winisd tutorial which i see your name appearing in the threads as well, and had another play with the program. I can see what you were getting at with limiting the input power now etc so as to not exeed maximum cone excursion. With a max signal input of 500watts & 16Hz port tune it seems that if i use the 160mm port tube i will get a tad too high port air velocity of about 38 m/s at around 14Hz, 16Hz and above & 12Hz and below seems ok, wether i will notice this in practice ... i don't know. Using 200mm pipe clears the problem but get into awkward port tube lengths etc.
Iv'e took some WinISD grabs of various possibilities so will put them up asap.
 

Member 639844

Former Advertiser
Dont forget that limiting input power has side effects of its own, especially if you wish to employ electronic eq. More spl takes more cone excursion and power, and lower frequencies require more actual spl to be perceived equally, so limiting input power wouldnt be something I would do unless I had to as a last resort. Chances are, if you buy a 1kw rated driver, and limit the system to use only half that power, your wasting potential somewhere.
 

swiftpete

Distinguished Member
The 160mm tubing that you have is actually only 150mm as the walls of the tube are 5mm thick.
One of the things to consider is that when you're looking at port air speed, you're looking at the worst case scenario, with the sub working at full bore. In real life it's unlikely it will be working that hard as you have twin 18s in a smallish room. Mine on paper didnt really work as the port speed was too high, but you've heard them and even when they're turned up, there is no audible port noise at all because even turned up they're not going flat out. If I had a room 10 times bigger and was driving them at their max then maybe you would, but I don't and I doubt you will either.
 

Member 639844

Former Advertiser
The 160mm tubing that you have is actually only 150mm as the walls of the tube are 5mm thick.
One of the things to consider is that when you're looking at port air speed, you're looking at the worst case scenario, with the sub working at full bore. In real life it's unlikely it will be working that hard as you have twin 18s in a smallish room. Mine on paper didnt really work as the port speed was too high, but you've heard them and even when they're turned up, there is no audible port noise at all because even turned up they're not going flat out. If I had a room 10 times bigger and was driving them at their max then maybe you would, but I don't and I doubt you will either.

His initial idea was quite high though, peaking at 65 m/s at around 15hz. Even at half power its still up at 45 m/s. Some people will say dont go over 25 (ish) m/s, but I think in a high performance system you can likely get away with a peak upto 35 or so in the model, 150mm is a big port and if you never go that loud your fine. Even a single 18 maxes at around 115db in this enclosure size tuned to 15hz.
 
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Johnny.G

Active Member
Not long been back in from meeting up with Chris who very kindly collected my Fi Q18 driver from Bladeice, big thanks for that Chris. Had a quick look inside the box...... what a magnificent beast it is as well !. Will try and make some progress with the build now. :D
 

chrislaw1968

Active Member
Not long been back in from meeting up with Chris who very kindly collected my Fi Q18 driver from Bladeice, big thanks for that Chris. Had a quick look inside the box...... what a magnificent beast it is as well !. Will try and make some progress with the build now. :D

No problem at all , nice to meet another member:smashin:
 

Johnny.G

Active Member
A bit hampered with a dog bite injury to my left hand but managed to do a bit more today, the front baffle is double 25mm mdf and managed to seal all the internal joints for added air tightness and cut out the initial driver hole. All being well the rebating of the driver into the front baffle will be done tomorrow. Couple of pics showing work done today.
 

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Johnny.G

Active Member
Another....
 

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Ashmanuk

Well-known Member
Can't wait to see the driver in that bad boy :) and what did you use as a glue ?
 

Johnny.G

Active Member
Still staring at it in amazement at the mo Ash ... :D , dropped it into the cut-out yesterday just to make sure that part of the operation was correct. I too have a carpenter mate who casts his professional eye apon proceedings as we go along and he felt the weight of the thing and was amazed at it's weight .... and size, as a lot of ordinary folk have not seen drivers of this size. Re: glue, can't remember the exact name of it as it was my mates but it was or sounds very similar to the stuff you used, powder form and mix with water to a paste etc, takes a good day or longer to totally set and grab and is superior to pva iv'e been told. We are doing a bit more today so i will ask him the name Ash.
How you getting on with yours pray tell
 

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