A few people have asked me about this, so here's some info on it. As usual, the design was done with the woofer and SEOS12 mounted on the same plane (inset equally). The result ended up being smoothest slightly above center of the waveguide (lobe going a little upward), so you might want it to be positioned a foot or so below ear level. Or you could alternately inset the Celestion 15" a little more (or back mount it, if the baffle's not too thick). The box we used was 2cuft sealed, which checked in around 75Hz f3. If you really want it to go deep, make a 13cuft box and port it! Divorce may be required, though. That woofer turned out to be quite sweet. Very nice smooth midrange, well behaved before it rolls off naturally around 2kHz (actually easier to design with than the TD15M, which has a lot of junk to get rid of above crossover). I may like it better than the TD15, actually, but remember I'm not a high-volume freak-- TD15 may do better if you're wanting your neighbors down the street to hear it clearly. That's a pretty nice result for inexpensive drivers. Check out the smooth phase response! Erich has the one that was built, haven't heard this in stereo but there's no reason to think it wouldn't be pretty fine. Maybe if Erich can tear himself away from outside work, he'll get around to making up a second one.
Thanks Mr. Waslo!!! And a very economical crossover to boot! This is hands down the best bang for the buck yet...... Using a 3/4" baffle, would rear mounting the woof be about right to bring the sweet spot to horizontal? Should the SEOS be mounted adacent to the woofer vertically with minimal spacing? Since I will be using bar grills, the baffle will end up around 16.5" to 17" wide. This is not an issue, correct?
This is hands down the best bang for the buck yet...... No kidding! Bill, with the lobe pointing up like that, and such a large woofer, how close is the woofer to the floor? Any issue with that? I gotta get a pair of these somehow 8)
wow, unless i'm missing something, these come in about $50/speaker under the karma-15. and thats with the more expensive cd (the 360). since there's very little info out there on the karma, and you designed them both, could you maybe comment on how the two would compare, Bill? would you consider this a better speaker, despite the lower cost? similar, but cheaper? or would you say the comparative sound quality is commensurate with their respective costs? i guess i'm not even sure... did you ever build/hear the karma-15, or just model it? if you never heard it, speculation from someone with your experience is still better than nothing. as for efficiency, is it a safe guess that these come in ~97 - 98 db, since thats what the woofer specs/models at? also, i'm interested in hearing some insight from Bill or one of the more experienced guys on the first question zhillsguy asked. i was previously leaning towards a trio of tempests as new l/c/r for my theater, but with the way this woofer models with my available amp power (170W continuous from an onkyo 805) in a box size that works well in my space (17x25x10 or thereabout), and at 2/3 the cost... it seems like these may take the cake.
Well, 1: I dunno, depends on how close you listen. 3/4" sounds like a lot, but work out the trig. The lobe seems to point about 10degrees upward. 2: absolutely! 3: shouldn't be a problem I don't think. The boxes Erich built were 19" wide (I think). That depends on how you build the box and position the woofer. Since I evangelize for having waveguides near ear level and the woof as close to it as you can get, that would put it rather high from the floor (and yeah, there will be a null from the floor reflection -- I also like EQ!). Well, they're basically the same speaker. But with the buyout you can get the woofer cheaper (it's very similar to one of the stock Celestions, Erich knows the number). After we made the "Erich 15" (as I like to call this) I immediately bought a pair of the woofers for safekeeping.... like I need another set of speakers. But I'd really like to hear this in a big ported cab if I get the chance. That should be a good estimate (maybe a dB or so lower to account for crossover inductor loss). But the speaker can really jump with not much power, at least over the frequency range it can cover.
Bill - great info, thanks! These are so cheap and hard to pass up. I'm in no position to need any more woofs at the moment, but still very tempting. Any thoughts around a multi-driver (2+ woofs per cab) design using these guys?
thanks for the answers Bill... I'm in! PE/UPS santa left three buyout woofers on my doorstep yesterday. Unfortunately, i'm not letting myself start on these until i finish the cjd rs150 mtm's and core 2-ways i'm already working on (amongst a billion other projects around the house). couple more questions for Bill, or other experienced designers, if you don't mind. the direction of the vertical lobe is based on the tweeter and woofer's relationship to each other, correct? in other words, if i run these with the waveguide below the woofer to put it closer to ear height, the lobe will then point 10 degrees down rather than up, right? also, if the woofer is recessed a bit more, or back mounted, to redirect the vertical lobe, won't that change the relationship of the drivers' acoustic centers, which will mess with the phase response and/or time alignment (or something of that nature)? if so, is that less important than having the vertical lobe aimed correctly? as you can tell, i'm not a designer... just a builder trying to remember the design related things i've read in the past.
Yep that would be the same as flipping the speaker upside down. The time/phase alignment made in the crossover it what determines the position of the forward lobe, changing the woofer recess does indeed mess with them and that is the goal. What your doing is changing the listening position where path distances between each driver remain the same as original design called for. As long as you keep those driver path distances the same as the original design the time/phase alignment will also stay the same. So for example if you were to move the woofer out a little the listening position (or lobe) must move up in order to keep the proper distance between each driver. Now this only works for reasonably small angles where the response of the drivers have not changed much from moving off axis. Now someone might want to double check my number but it seems the woofer must be recessed almost 2" to point to vertical lobe on axis. That seems quite large to me but I ran those numbers at 30" and 10' and got similar results. I did it the same way I explained above by keeping path distances between drivers the same. At 30" baffle distance 6" above tweeter center LP distance to tweeter is 30.6", assuming woofer center is 11.25" below tweeter center then LP is 17.25" above tweeter and distance to woofer is 34.6". So path distance offset between the two drivers is 4". If you move to directly on tweeter axis at 30.6" distance then the woofer is just 11.25" below the LP and distance to the woofer is 32.6" Therefore 2" must be added to the woofer distance in order to equal the 10 degree above axis offsets.
^ | | what he said (thanks, mtg90) On the question about a design with dual matched 15" mid-woofers, I have to ask.... why?? Unless utterly huge ported boxes are used, these designs are meant to be used with a subwoofer. The 15" Celestion (or AE, or whatever pro mid-woofer) used to crossover to the waveguide shouldn't be thought of as a woofer really -- it is a really a big midrange! The idea isn't to get smoking bass, but to control directivity (match waveguide) to a decent low-midrange frequency with good efficiency. What does a design with dual mid-woofers buy you? You get two midranges spaced at least 15" vertically offset, a recipe for vertical lobe problems. That's not good. It gets you more mid-bass output capability, but this works only 70Hz and up -- that's going to be way more than you need with just one. For example, if the mid-woofer is to play down to 70Hz, then for a 15" sealed sub to do the same output SPL down to 20Hz it will have to move about 12 times as far (not counting room gain, which can help on that). If the mid-woofer has xmax of 3mm, then the sub would have to linearly excurse about 1.4" to keep up! That's simplified because of baffle step and room effects, but you can see the scales involved. A 15" midwoofer is way more than enough for anyone without a death wish, over the frequencies covered. Using two 15" midwoofers will also cost you twice the box volume, just to get the same -3dB point. Don't change the box size and they won't go as low as one would. You could cross them over differently, using the woofer closest to the waveguide at higher frequencies and the other one at lower frequencies. But it would still take a bigger box to get the same frequency coverage as one woofer would have. You might get something out of having the woofer for around 100Hz closer to the floor boundary, but that's already pretty close to where the response will likely start dropping (assuming, again, a sealed box of reasonable size). Possibly using a 15" subwoofer driver (different driver) below the midwoofer would have some merit, but you'd have to pad down the waveguide and the 15" midwoofer to match the sub driver's much lower sensitivity. Or power the sub from a different amplifier. But you'd lose the capability to place the sub for best in-room response, because it would be tied to the other two drivers that also have their own needs for room placement (seldom the same as for the sub). So other than maybe looks, there isn't much benefit that I can see for doing that.
I'd like to get a pair, but jeez, what would I do with such big speakers. For the shop maybe? I have enough speakers to make shop speakers. That would be a waste. But so hard to pass up quality 15s for $50 each. :-\
Unboxed my pair received from PE tonight, one was damaged and not working properly :-[ . Extremely minimal packing, not really surprised with the damage, I feel lucky to get one that works.
Thanks for posting that. I'm gonna pass on them. I'd have to have them sent to my parents in Minnesota and then get them later. To risky.
i was thinking the same thing... bought three, only opened one all the way. mine were packaged pretty thoroughly though. granted, it was standard buyout packaging - driver in folded cardboard, surrounded by scrunched up paper, in a makeshift box. but thorough none the less.
Bill - I understand the problems with vertical lobing with such large distances from the waveguide. The primary (perceived) advantage I was thinking would be to gain efficiency, power handling, and output across the spectrum, but it sounds like that is as not as feasible as I had originally would have guessed. So - I guess we can scratch the practicality of implementing such a a design. For such an inexpensive price (two of these still cost much less than most 15s) I at least had to ask. But man would a pair of these in a tower based design look cool.
Well, I’ve only completed one speaker so far. So my listening impressions are based solely upon listening to music in mono on Big Daddy. If only a single word is afforded, the word “immense” immediately comes to mind. The stature, the soundstage and the effortless rendition of favorite tunes are all immense. Immensely pleasing. This is my seventh build of OPSD (Other’s Professional Speaker Designs) and it is a new high water mark in my listening experience. I’m looking forward to building its sibling and listening in stereo. If you have the room, consider these a personal luxury item.
I went with the sealed box design in the attached picture, I did skip the inner baffle. The bass is very satisfying, but I can't help but wonder about a large ported cabinet.
Haha I would LOVE to see someone build these into huge Cornscala-style boxes. Watch peoples' reactions when they absolutely pound, then tell them they were a couple hundred bucks each.