The long and winding road to get here is within sight of coming to fruition... I'm posting this thread to force me to stay on task and hopefully it will shame me or pressure me enough to finish this experiment.Project Description:
A "modular" speaker design that would allow me to re-use the bass and midbass driver cabinet in combination with at least two different horns and 4 or more compression drivers to (hopefully) find a combination of horn / compression driver (along with the bass cabinets) that results in an overall speaker that I like the sound of enough to keep long term. If I like multiple combinations, the "modular" approach taken allows me to effectively have multiple speakers without having to store multiple large speaker boxes in my space. Details below.Project Goal:
find a combination of horn/CD and woofers that produce a speaker that I can use for 2 channel music listening that do everything I like about the commercial speakers I have here, but also add the dynamics, low distortion, and directivity that these horns are supposed to do in spades. I've heard a *LOT* of horn based speakers over the years.... a couple have done some things that I've really liked... but there has always been something that aggravated me about them to the point that I just couldn't live with them.... call it HOM, call it "honk", call it a personal, subjective dislike of the concept.... who knows what it was.... I've built a bunch of SEOS12 designs and while they all have merits and represent a value, none of them so far are on a level sound quality wise where I'd keep them for high end 2 channel listening and abandon my other speakers. That's not a knock against any design or particular designer or the concept as a whole...... but so far, they've just not been for me and my personal tastes (and yes, I built them all correctly and verified so)... along with the Zephyr build for a buddy, a 3Pi build I'm building just to hear it, and a ported version of the Cheap Thrills as a present for the nanny, this big horn project is my last attempt at experimentation with horns and waveguides before I consider my curiosity quenched on the topic for now... I originally also got involved with this concept because I was intrigued with the controlled directivity concept because of increased sweet spot possibilities and potential to get away with less room treatment and still get good sound (that would certainly have WAF given my current acoustic treatment setups throughout my house).... so far, of all the designs I've built, none of them allow me to ditch any room treatments... they're marginally better in a crappy room... but they unfortunately don't magically get around limitations of an acoustic space, nor do they work well enough with less treatment where I can live with getting rid of some of the stuff I have setup... it was just too much of a negative impact that I would have to keep all the treatment in place....Project Details:
The horns/waveguides that will be experimented with for this project are the SEOS 24 1.5" entry fiberglass horn and the Iwata-300 2" entry fiberglass horn, both from Poland and both imported by DIY Sound Group. Right now, the only CD I have here that fits the mounting holes on the SEOS 24 is the BMS 4595ND coaxial CD. I have a JBL 2447 CD with beryllium replacement diaphragms here as well... but the bolt pattern is too big for the tiny metal mounting plate on the SEOS24 and can't be used without modifications. I'll play with the BMS first before deciding if I want to bastardize the horn enough to build an adapter plate to make it work. I also have someone that has a pair of 2450SL CDs they'd sell me that use the smaller bolt pattern needed to fit the SEOS24... not sure I want to buy them and sell the 2447s.... will decide later.... I also managed to get another pair of JBL 2446 2" CDs, these ones from the period where they made them with the smaller bolt pattern needed to fit the metal mounting plate on the Iwata horn. I also have a BMS 4592ND coaxial CD to directly compare against the JBL. so at least I can do a direct head to head shootout on the Iwatas without having to do any modifications...
I have had rather conventional looking speaker enclosures built for me (see attached image showing the plan) that will house the woofers. The horns/waveguides will sit on top of these woofer cabinets in free space. All cabinet walls and internal cabinet dividers are 1.5" thick made up of 3/4" 13 ply birch plywood laminated together with 3/4" MDF. Bracing put in at the time of construction was ok... I'll likely have to beef it up significantly by the time I'm done to reduce any cabinet wall resonances to a point they aren't offensive to me or overtly noticeable in the final voicing of the speaker.
These boxes have two independent sealed cavities. The bottom, sealed cavity will house the Acoustic Elegance TD15H woofer. It will effectively be the "subwoofer" of the system and have it's own separate dedicated amplifier (in this case a Crown XTi 2002, which sounds like complete a$$ run full range, but is adequate for bass frequencies and has some flexibility with its DSP allowing electronic crossover and PEQ to flatten the overall bass response in room). The top, sealed cavity will house the Acoustic Elegance TD15M. In the enclosure size I'll have the TD15M, without factoring in the room, the woofer should start rolling off a little under 80Hz according to the models. The TD15M will cover from this ~80Hz point up to the crossover with the various CDs/horns. So, essentially, this is a "X
.5 way" speaker with no high pass on the TD15M, only a low pass on the TD15H to roll it off at the point the sealed TD15M starts to roll off naturally. I chose to use the TD15H instead of a second TD15M in the "X
.5 way" design to take advantage of the extra Xmax in the 15H... 99.9% of the time, I'm never going to play the overall speaker at a volume level where I'll run into power handing or excursion issues. The extra excursion will get eaten up trying to compensate for the sealed bass design and adjusting for some anomalies in the room that affect every speaker I've ever put in the room and I want to fight a bit with some EQ...
The AE woofers are used exactly the same way in every combination of CD/horn, with only the low pass crossover of the TD15M where it crosses to the CD/horn combo changing.... all passive crossovers for TD15M/CD/horn are external to these woofer boxes stored in their own external boxes to allow quick changes when the CD/horn is swapped.... each woofer has a straight run of JPS Labs speaker wire from the binding posts on the back of the box to the woofers themselves.
The "modular" part of the speaker comes in largely because of aesthetics, but also legitimately because of the uncertainty over what (if any) combo of gear will stay long term. I'm going to use JBL's 2509a metal mounts bolted to a 1.5" thick "mounting plate" (two 3/4" 13 ply birch plywood layers glued together) that is the exact same dimensions as the top of the woofer cabinet. Given the different sizes (and definitely depths) of the SEOS 24 "waveguide" versus the Iwata-300 horn, if I bolted the JBL 2509a to the top of the woofer cabinet, I would have two different mount points.... that means two different sets of bolt holes in the cabinet itself, having to unbolt and re-bolt the JBL mounts each time I want to swap back and forth between the different horns, and having to beef up those locations in the woofer cabinet to avoid weaknesses or air leaks around the bolt holes thanks to the sealed TD15M cavity.
If I ultimately end up keeping only the SEOS24 and ditching the Iwata (or vice versa), now I have extra bolt holes in the woofer enclosure that serve no purpose and have to be filled and re-finished, or forever are a reminder of what once was.... by having multiple sets of JBL 2509a metal mounts, as well as multiple sets of "mounting plates" that are the same size as the top of the enclosure, I can leave the JBLs permanently bolted in their ideal locations on each set of mounting plates, have both sets of horns permanently attached and ready to swap back and forth, and the mounting plates being exactly the same size as the top of the box makes lining everything up super easy to get set correctly when you switch back and forth.... if I get rid of one horn or the other, it's just a couple pieces of wood and some stain gone and no one is the wiser. I can swap back and forth between horns by just lifting off one assembly of "mounting plate"/JBL 2509a/CD/horn and dropping on the other.... takes a few seconds... quick swap of speaker cables to the new external crossover network box for that design and I can be listening to an entirely different horn speaker in a couple minutes tops.... all without having to move the woofer cabinets and only needing space to sit the horn assemblies off to the side instead of enough room to have a completely different speaker box...
The really big aesthetic perk of the "modular" approach I'm taking is in finishing the speakers and their look.... this design allowed me to request boxes be made very quickly and cheaply, yet still result in a pretty nice aesthetic look.... see the pictures below.... the design calls for butt joints everywhere so it can be slapped together really quickly (i.e. quick and dirty with less labor time to build than beveled edges or box within a box to limit the edge grains showing)... all the edge grains are showing on the front face, top face, and back of the enclosure. The front, top, and back can now be covered in Duratex to hide the edge grains, leaving the side panels to be stained and lacquered. The separate mounting plates set on top of the box now allows the top to also have stain and lacquer, with only edge grains for that plate showing (and that can be edge banded with veneer and look acceptable easier than trying to veneer the MDF and plywood edges on the top, front, and back of the box by itself)... I don't have a photo yet of the mounting plates sitting on top of the woofer enclosures to better demonstrate what it looks like finished.... that will likely make it easier to show... I'm just now finishing up staining those mounting plates and should have them done in the next day or two.... I'll put a pic up at that time to show the design better than I'm describing here in words... but so far, I am very happy with how it is going to turn out based on finishing the boxes to their current state and how far along I have the mounting plates themselves...
In order to allow use of simplistic, minimalist two channel electronics I already own, I'm going to make the attempt to do passive crossover in between TD15M and CD/horn combos, no matter the cost of the passive crossover components, or even if the passive is less than ideally optimized.... Power handling simply doesn't matter beyond a couple watts as 99.9% of my listening will be at volume levels far lower than folks on this thread like to run their setups. I'm not opposed to trying a couple forms of EQ / room correction I've not yet played with (from directly within JRiver, or from using Dirac Live filters) if the less than ideal crossover means it still needs a little EQ to even things out. I'd rather do that than complicate the system with active crossovers and need two of everything (DAC and amp channels) for powering the TD15M and horn assembly).... The cross between BMS MF and HF inside the CD will definitely be passive based on quick listening to the stock BMS passive crossover unit and a couple different ones I put together... if I don't want to deal with the complexity of active crossover and extra amp channels for the woofer/horn crossover, I definitely don't want to do it for the BMS
heheProject status (as of this posting):
raw woofer cabinet is constructed by a friend and delivered to me. I installed the 3" casters in their semi hidden recessed bottom plate area to allow the boxes to be rolled around if I need to move them. I then spent the past couple weeks finishing the box to a point that it is now permitted into the house. The birch veneer side panels are stained with a nice antique walnut gel stain and sanded to 400 grit level. the front, top, and back panels are prepped, coated in two thick coats of Duratex, and then have been sanded down to 400 grit level and the duratex finish buffed out to hide as much of the orange peel finish look as possible.... I still need to put many layers of lacquer on the birch side panels and do some finish spray coats of Duratex on those surfaces as well (to get rid of as much of the orange peel as I can)... but I'm going to listen to the various options and design some crossovers first before I spend any more time on cabinet finishing.... it's good enough to get past the Boss's objections to coming in the house
so I'm stopping finish work for now and moving on to stuffing boxes and beginning measurements and crossover designs... which should hopefully start in earnest this week....
The raw "design" of the woofer boxes:
The woofer boxes as they were delivered to me by my buddy who built them:
The current state of the woofers after staining the side panels and putting Duratex on the front, top, and back. One photo includes the spray can of flat black paint I used to paint the routed driver recesses for a sense of scale. I didn't want to put the Duratex in the driver recesses since it builds up and my buddy cut the recesses pretty tight for the TD woofers.... last thing I wanted was woofers that wouldn't fit in the openings after putting the Duratex on