MercedesBerater

Test fitting the holes before adding second layer of MDF.... tested again... then added the 3rd layer for a recessed fit with 45* chamfer — I didn’t do a full chamfer on it, I started it right where the basket ends- I thought that would look more seamless. working on bondo on the seams... and making nice and smooth. then I’ll round over all the corners & add a 45* chamfer to the perimeter of the front then cut out the vent and round over the top and bottom edges. ( I think I’m going to leave the side walls squared off) started shopping for paint codes.... leaning towards Bentley Beluga Black with a buffed and polished finish for a high gloss. Then probably ceramic coat it to prevent scratches and swirls in the paint.

here's another way to look at it -- does a brand new, first time played speaker sound the same as a 30 year old speaker? no, they do not. the surround is weaker, it may be 'sloppy' for lack of technical terms. this is break-in to the extreme.

All mechanical devices have a break in period, that i'm aware of. the amount and parameters of the break in vary. AMG engine, 2500mile break in period with specific guidelines for optimum performance. -- some auto mfg's even go as far as electronically limiting performance to force the break in. Suzuki did a study on bike engines, and found that the motorcycle engines that were properly broken in had more horsepower and lower repair costs than the ones that just twisted the throttle from day one. Speakers absolutely have a break in period - i don't think it's like the gates of heaven opening up and a golden chest of dB's and lower Hz are presented to you with scantily clad angels singing -- but there is value in listening at moderate levels until components break in.

@capo72 Schmeling in Rockford - ask for Adam Kinkaid. good dude.

@CECAA850 - yes subs will bolt through 2 layers of 3/4 cabinet grade MDF (i spent the extra for the good stuff from a real lumber yard, instead of the cheap stuff from Big blue, Big Orange, Big Green.) then, around the subwoofers there will be a third sheet with a 45* bevel around subwoofers and 45* bevel around the front face. make them look recessed, and add some more stiffness - but they won't bolt through it. so not sure if that counts as a triple or double, or a deuce and a half.

Adding poly fill to the one side (easier to get to now) Then I’ll find some time do add the right side wall & clamp up. and need one more sheet to do a double baffle and then I’ll have a third sheet on the front with 45* decorative edge around speakers and the perimeter of box. Technically a triple-baffle, but the speakers will only bolt into 2 sheets.

@Paducah Home Theater I only have two 18's per box now. my original plan was a stack of 3-4 in each corner, but i was nervous about separate cubes vibrating and the stack toppling over. acutal exterior dimensions are 56" tall, 30deep, 23 wide. 18.5" long slot port, 3.5" tall x 18.5" wide. (according to a few websites, this should be an 18-19hz tune.) +poly fill.

Bracing done. next up— cut out woofer holes & amplifier hole. Then run and secure subwoofer power and ground wires and leave excess coil so subs can he hooked up easy. And wire isn’t flapping around inside. then add poly-fil sheeting to the outside wall surfaces before closing up the side wall. then wait until the wife isn’t looking and order the subs & amp. 🤣

And so it begins... here I’m test fitting the panels & brace. There will be more bracing in the subwoofer areas, but will need to draw a window design with subwoofer cutout. So I’ll make all of those at the same time.

@PrestonTom got it, i have some spare safe-n-sound laying around to split up into slices. it does 'delaminate' pretty well into thinner sheets. it will be a fresh build. see earlier in post for dimensions and modeling in WinISD.

@PrestonTom ohh that's a good idea to use a more rigid type thing, maybe even carpet underpad like Jute? that would be more tidy to spray glue in place. in a ported enclosure, would you line the inner side of the port that faces the subwoofer, but not inside the actual port cavity - right?

does anyone know the effect of polyfill? i read somewhere that in large(r) enclosures it isn't as effective as small(er) enclosures and is kind of like a 25% increase in box volume. is this true? i tried re-modeling the box as 16cu/ft and also 20cu/ft leaving every other dimension and spec the same. it looks like it gives almost a 3db bump starting at 20hz, down to 12hz and then rolls off pretty hard. does this seem like a fair guess on what some polyfill will do? then the question is... how much?

Ok, here is what i have got modeled up.... this is laying on it's side.... the port would be on the bottom. dual UM18-22's this is the SPL graph transfer function magnitude cone excursion (with a highpass filter, butterworth 15hz n=2) air velocity

@Iteachstem sealed Home theater. Acoustic treatments. Dedicated room. 16wide 25 long 7’8” tall

i've found kind of what i was dreaming up...well, one of many dreams. dual 18's in a large ported box. i am not so great with WinISD - i think i've kind of reverse engineered it pretty accurately - i just can't figure out how long to make the port. BOX= 22.5" wide, 28" deep, 54 tall dual 18 UM18-22's Speakerpower SP1-2400 slot port = 3.5" tall x 18" wide..... which the bottom of box would make it 28" + ?????? how far up the back of the box? to tune it to 11hz. (SeatonSound did a very limited run, 6, of these and they were tuned to 10.5hz. just can't figure how long to make the port to achieve that.) Thoughts??? because THIS....THIS makes me happy. I could look at these for days....

if i get the green light from wife - i'll start a build thread. i had one for my theater years ago - and that was fun to document.

@MookieStl i noticed that too - all GSG stuff is ported, and i believe all has a recommended UM18 as driver listed. - sealed is easier to build anyway. i'm not entirely sure i would be missing anything earth shattering going 3-4 sealed 18's in the front corners and a couple in the rear to smooth out the room response VS. a stack of ported. improvement? yes, i'm sure - worth the effort and mental headache & loss of clean lines? probably not in my opinion. and- if i hate it, not too hard to disassemble and start over. MDF is cheap. 🤣

@CECAA850 ohh, i'm not sure. I'm trying to rapidly learn all these Alphabet soup letters and meanings and calculations. I thought with WinISD i could input the driver & dimensions and it would say 'hey, for 22 cu/ft, 4 drivers, you need a XYZ sized port) maybe i'll stick with sealed & just base it off the 4-6cu/ft ideal range Dayton specifies and adjust the box dimensions accordingly. That's way easier. @RandyH000 yes, i'm sure there are good deals out there on used - but there's something to be said for figuring it all out, building it, and saying 'i built that' and to get it to fit perfectly in my space - and the look i want - i'll probably never find used.

@CECAA850 i'm 75%movies & 25% music (CD 100% of the time i listen to music) also note, when i listen to music, it's typically turned up with the theater door open so i can hear it in other areas of basement - so sound quality isn't paramount. i use it as a giant boom-box. the driver Fs is 19.5hz (Dayton Audio UM18-22)

@henry4841 thank you for the link ! that site says i should be building SEALED with that driver, it says not recommended as ported. Guess that's why the Seaton F18 (same driver) is just a sealed box, simple... I didn't want to build a bunch of identical boxes to the Seatons - because i'm worried about stacking 4 subs high, and then they vibrate and topple over like a scary Jenga game. I'd rather build one massive box and have basically a Stonehenge monolith in the corners. Essentially - i want this... just don't want to spend $12,000 to get it. I'm sure i can DIY for a few grand.

@CECAA850 If you were doing a build with 4 drivers, basically a box floor to ceiling (in the corners) would you go ported or sealed? seems like ported is the no brainer since i have about 22cu.ft of volume - i'm just a bit nervous about the complexity of figuring out the slot port length.

I am trying to model a subwoofer box before i undertake a DIY build. I have added a UM18-22 into WinISD I am trying to model sealed vs. ported for the left and right front corner locations in my HT. I want to build a stack of four UM18-22 in each corner. Box dimensions roughly 22'' wide, 22'' deep, 7 feet tall. (~22 cu/ft) Basically - trying to build the Seaton F18's (stack of 4) for fraction of the cost. When I graph out the sealed box - and the ported box (both same box dimensions) they don't graph much different. Is this abnormal? I expected a box with 4 drivers, this big and ported would be 'off the charts' so to speak. they both peak at 35hz and then begin to roll off, almost identical slopes even, except the ported is 1.85db higher output at 35 hz. something can't be right. If this is the case, i would totally build it all sealed just for simplicity sake - just mimic the Seaton F18 dimensions and be done with it. any help-thoughts-insight? (ported box square vent = 18" wide x 4"tall x 35.54" length (last value won't let me change it)

right- if the subs are powered with their own dedicated amplifier - you'll just need a 'sub out' on whatever processor you have. source material > processor / AVR > amplifier > speakers > subwoofers

@Majestictone capacitor life is in the thousands and thousands of hours - often referenced as 30 years. everything you're looking at *should* be fine. but new(er) might be less failure/maintenance prone.

@garyclayton if you are new to the scene - AudioGon website is a used swapmeet - sometimes good stuff on there. and cragislist is still a good option.