TLS and Haoleb,
Thanks to you both for posting the info and experiences. It's appreciated.
I'm about to upgrade my velodyne sub with a DIY sub in my dedicated HT. Was pretty much sold on the ultimax 18, sealed with an iNuke 3000DSP until I read the blogs on the HO 18" ported design. I plan on building the cabinet whatever way I choose to go.
With that, I'm heading down the rabbit hole to join you. Several reasons.... I already have a QSC RMX1450 sitting here from my old band days so I won't need to buy another amp. And... the woofer doesn't need EQ so I won't need to get DSP (either from the iNuke DSP or form miniDSP) saving more money. My pre/pro is an Anthem AVM20 - so I have some control over the crossover point and it has balanced outputs that will make it easy to feed the QSC amp and I have a bunch of cables laying around, saving more money). I'm saving so much money now that I should go spend it... on a new woofer and wood.
I can always do a second woofer, although I don't really have space for one. My room is 13-foot wide, 20-foot long and has 8-foot ceilings.
With respect to bracing and damping the cabinet, it's gorgeous and definitely takes extra work. Wierdos do this kind of stuff hoping it will make a difference - even though it's based on some sound science. And no one but wierdos looking at the construction photos would recognize the extra work.
I'm wierd just like you guys. I overbuild everything. Just ask my wife.
BRACING: I'm thinking the bracing on the HO sub in this thread could be less and much more simple yet just as effective and still allow the use of 3/4" MDF. Benefits would be 1) internal volumes wouldn't be impacted by as much bracing, and 2) the cabinet is lighter. (Understanding that heavy usually connotes "better". In this case, if the bracing and damping is adequate, I don't believe a heavier cabinet would necessarily perform better.) I"m basing this off the principles that columns are much stronger at supporting a load than a beam (although beams definitely have their place, e.g. large open /unobstructed spaces like a house or office space).
In the case of the interior of a subwoofer... having a series of dowels running from side to side will be very effective at damping the sides when using 3/4 mdf. The biggest force/reaction is produced by the woofer itself... running bracing from the baffle to the opposite side would provide significant support to the back wall as well as the baffle and woofer. Particularly if you coincide the columns to accept the driver screws.
This is what the stonehenge design does. You can check it out at diy soundgroup as well as the build by clemsonjeeper on avsforum (I couldn't include the link or address as i"m such a newbie...)
I really like the stonehenge design. But... the wierdo in me causes me to believe that additional damping of the large panels would be beneficial. This is easily accomplished with some dowels or additional MDF pieces tying the sides and existing column braces together. Thoughts? Flaming?
JOINERY METHODS... I have yet to see sub build that utilizes biscuit joinery. I'm a huge fan of it, way better than pocket screws. I subscribe to the tenet that the glue holds the parts together and fasteners are there merely to align, clamp and support the pieces until the glue sets. Biscuits do this very well while being unseen. And they are super easy to install... very forgiving. I use the straight clamp guides for aligning biscuits as they are very handy (and I have no affiliation to the mfr or rockler, but here's where you can get them at rockler. These are great for routing and cutting large panels with a circular saw as well.
PORT LOCATION: I do note that the port on the stonehenge does not open on the baffle, but on a side. TLS mentions somewhere in these build threads that the port should open on the same face as the baffle. Care to comment more on this??? I do recognize it seems intuitive that the port work with the woofer.... is the length of the port set to have the port vibrations in phase with the woofer? If not, that would be bad...
A suggestion on the existing HO build: the port construction could benefit by leaving out the "back" upright piece as it's redundant. Just use the back wall for the port. You would reduce the impact on internal volume and gain a bit back. I do see why the port has the exra piece of mdf on the bottom... as it raises the port opening on the baffle so it's more aesthetic. I like this touch. Also love that you routed the roundover on the port inside the sub. It's all about fluid flow and the reduction of turbulence......
So....I'm not wanting to flame or criticize, but to gain some knowledge from you, and hopefully contribute some of mine so we can all make better subs. Please accept my questions and observations in this light.
In appreciation and comaraderie,
Rob