[nodiak]

John, your system looks great, and the reviewer really liked the sound which is impressive considering some of the other quality systems there. Congratulations!
I've been out of ob for some months but have tried some different things over last few years. Because of their fine midrange have decided on a 2 way passive with the hemps, so the search for a matching bass driver (or 2 drivers). I have decided to not go for a more expensive cure for now - the Rythmik/GR Research OB servo subs. I would use these in stereo up to the 200-300hz range, which would mate to about any single driver or 2 way. I have a single sealed version of these subs and can tell the stereo ob system would satisfy. (I highly recommend the Rythmik/GR Research subs to anyone looking for such a solution). I may go that route later this year.
I listen to enough electronic music that the subs are needed for that (and occassional scifi dvd), and work great. For the more "typical" music range these Philips 15" are working out except for their spl not matching the hemps. So should be able to find a 1 or 2 driver bass for the hemps.
From others experience it seems a single Alpha 15 wouldn't work, but from your calcs they would have higher spl than the Knights and Warriors. Sooo, looks like 2 drivers are needed. Maybe 2 12's (Warrior, Alpha). Will start looking around.
I have a pc problem now that hinders me from trying the recommended programs. My up to date pc crashed and has been replaced with one with dated programs and minimal abilities. I have't been able to do any downloads to it without it locking up. Not sure this will be overcome right away. Will get back to all this tomorrow.    
Martin, forgot to say I appreciate your point.
Don

[MJK]

 
Martin, forgot to say I appreciate your point.

Don,

After I wrote the original post I was concerned that people might take it wrong and I am glad you did not take offense.

Probably the most interesting thing about OB speakers it that due to their simplicity, they are really the easiest to engineer and get right. All you are doing is trading off baffle size and shape against woofer Qts (and EQ if you use it). You don't need to worry about box interactions and standing waves (even with wings) so if you select an appropriate woofer/baffle combination and get it to balance well with the SPL of the midrange or full range driver above it your are on your way to a great performer. Because higher Qts woofers tend to cost less (and don't require EQ) then woofers designed for boxes there is no real reason to spend a lot on the woofer, save some money and buy better drivers for the rest of the system.

Martin

[JeffB]

nodiak,

I am using the Warrior 15" on an 18" open baffle with no wings.  I driver per side.
I have an electronic cross-over and it is being driven by a 110watt per channel JVC RX-D210.
I like them quite well.  It is the only such driver that I have ever heard on open-baffle though.
I think it is the open-baffle that contributes to the sound I like.
I believe they need to be crossed over at 150Hz or lower.  The exact number is hard to say as my cross-over has a potentiometer and I have no means
to measure the actual cross-over frequency.  They sound to slow above 150Hz.  They are really at their best below 100Hz.
My Rat Shack meter shows good output at 25Hz.
They seem to lack some punch, but this could be related to not having an EQ or needing a bigger amp or something else.
I actually think I need another bass driver above them like an 10" to get the bass punch I am looking for.

[scottw]

Hey,

I bought a pair of the knight 15's on sale some time back. Still haven't decided exactly what to do with them. Have only listened to them sitting on the floor with no baffle and got the impression, as others have suggested, they would need their own amp and maybe some EQ. The cones are very stiff and robust, at least compared to large vintage drivers I've played with. The suspension also seems pretty stiff.

I had the idea to replace the stiff accordion surround with a foam surround, thinking this would make it more compliant and increase the VAS (?) and change some of the other parameters. If you have XBaffle try increasing the VAS for the driver. It raises the spl curve. If this was going to be a "subwoofer" it would probably not be a good idea as the more compliant suspension may let the cone over-travel. But as used to augment the lows for a fullrange driver, and not expected to reach too low, the increased compliance may not cause a problem. Also, Shred sells a recone kit for $19usd, so if I bugger it up there is a possible fix.

But I'm just guessing here and haven't changed the surrounds yet. Does this idea make any sense or is it a disaster in the making?


Scott

[nodiak]

Martin, no offense taken and no problem here. I appreciate your work/play and that you share it online. It's up to anyone else to "do with it as they may", seems the huge majority put your material to great use, and then share their results (as on diyaudio). I'm in and out of all this and so am behind on the learning curve so far.
JeffB, what driver/s are you using above the Warriors? I find my main issue is in matching bass tone to the main drivers, so it sounds like a system. Using the hemps (or similar) puts a demand on the bass drivers to be pretty tight. I also don't want to pad down the hemps, so low powered amps can work. And want to use a single passive xo < 500hz on the mains, then the powered sub/s. So that's the corner I've painted myself into. Leaning toward two 12's (or 10's even) now because:
I hooked up the 15" Knights, only played one cd so far. Baffle is 18.5" x 18.5" with sides that are 9" at base and 3" at top.  (*see below.) 
Marcus Miller (Silver Rain) a good bass tone test. I'll let them break in a day or two but so far -subjectively- they have a touch more spl than the Philips I was using, still don't match the hemps tho. They are pretty bold and go low. Midbass is pretty tight, lowest bass is big and smooth, but also has punch/body. All of Marcus' notes are coming through strong. Will see what a few days brings.
This ob method requires the bass driver to play clean to 200-300hz, and I also want solid 20hz (and lower) performance, I'm not seeing that range coming from one (or two) drivers on ob. 30-40hz no problem. So it seems best for me to go for ob bass system to ~ 60ish hz f6 (generic guess). Then blend in sub/s. Free air/no baffle this driver might be a good one for that, I'll try that later. But to reach hemp spl's looks like I'm still on the search, two smaller drivers probably best idea.
Scott, hope you can hook yours up and compare notes. If I decide to not use these, (even for shop or friends system, they would raise hell in a huge bib), I will try to sell to their intended users locally. They seem very tough, perfect for bass player (~ 3ft3 vented box is how they are sold). Imo, changing surrounds sounds like you could lose more time and dollars than selling and trying something else.
Don

* My room has some bass lift, it's #1 issue for dialing in bass here. Have corner bass traps, helped. 12' wide but 26.5' long. Suspended wood floor. YMMV.

[JeffB]

nodiak,

I have a B200 on top.
I don't think I can really help you with advise on your setup.
I have not heard enough gear and my own gear is far from top notch.
I bought the Warrior as an experiment because I was able to buy them for $25 each on a b-stock discount.
I need some EQ on the B200.  I have been wanting to do this with Open Source software on Linux, but never seem to find the time to work through this problem.
I like what Magnetar on diyaudio did with his bass setup here.
5 * 10" Warrior.
http://www.diyaudio.com/forums/showthread.php?s=cb4e20fa0880030575cea3884272cde8&threadid=116871&highlight=warrior
Apparently the 16Ohm version of the Warrior that was used is no longer available though.

[gitarretyp]

Nodiak,

If you want OB bass to 20Hz, you should look at drivers with an FS of 20Hz or lower. Something like the Acoustic Elegance IB15.

JeffB,

Speaker workshop works under wine, though i've never tried to make measurements with it in linux. RoomEQ wizard works fully in linux, but its measurement package isn't very robust. I typically measure using ARTA on my laptop, export the measurement to text file, and fiddle with crossovers in speaker workshop and EQ in RoomEQ wizard.

[nodiak]

"Nodiak,

If you want OB bass to 20Hz..."

gitarretyp, I'd stick with the Rythmik/GR Research OB system I mentioned. Their servo controlled bass reigns supreme ime. Check out the W-frame Danny's worked out, scroll down first page in link.
http://www.audiocircle.com/index.php?topic=54875.0
It's out of my budget for now but would cover 20-300hz and so eliminate the need for any other drivers but mains to the 200-300hz region, (or lower if they do it). Simple, but ~ $1200 (yet covers, 2 amps with some eq, 4 drivers). Would work with the Radian 5208c's we both have, or these hemps, or whatever someone likes. (Btw, not battling with your opinion, I respect what you've worked out for sure. Just stating what my experience with their sealed version has lead me to. I expect to get their stereo OB's later this year, or bust.)

After letting these run loud this morning they show a nice tight toneful midbass. Pretty good sq match to hemps at this point. Will make a baffleless frame for them to see if the big fat bottom can be trimmed down to fit in my room. I have a pair of plate amps to try on them too (they go in subs that are for sale, so just an experiment). As warned they don't match spl of hemps, but their tone is as good as I wanted, so will work with them for now...life will interrupt soon enough anyway  .
Don

[gitarretyp]

gitarretyp, I'd stick with the Rythmik/GR Research OB system I mentioned. Their servo controlled bass reigns supreme ime. Check out the W-frame Danny's worked out, scroll down first page in link.
http://www.audiocircle.com/index.php?topic=54875.0
It's out of my budget for now but would cover 20-300hz and so eliminate the need for any other drivers but mains to the 200-300hz region, (or lower if they do it). Simple, but ~ $1200 (yet covers, 2 amps with some eq, 4 drivers). Would work with the Radian 5208c's we both have, or these hemps, or whatever someone likes. (Btw, not battling with your opinion, I respect what you've worked out for sure. Just stating what my experience with their sealed version has lead me to. I expect to get their stereo OB's later this year, or bust.)

I've considered those. They look great, but the price is too high for me. Also, the swept volume of a single IB15 is nearly equal to a pair of the sw12s. For what i'm thinking, two IB15s per side ($400 total + an amp), i'd need $2400 worth of sw12s and and amps to reach the same output capability.

Out of curiosity, to what have you compared the sealed servos? Also, did you eq them both flat in room?

[nodiak]

Are those the IB15's that have been in discussion over at ib cult for a couple years (I haven't been there for a year)? Reported to be very well dialed in for that purpose. What size baffle needed for 20hz with 2 per side? Listed at $129 each, four = 520, plus amps, and eq if.
SD of three 12's ~ = two 15's (3 x 550, 2 x 850). Servo amps can do three 12's each. Two amps for 580, 6 drivers for 900 = 1480. So I don't think the $ difference is as big as you said for similar performance. But either way that's a heck of a lot of bass drivers in the house!
I've compared the servo sub to diy subs using Meniscus 1284's (drivers used in ACI Titan reportedly) which are clean and strong. But servo's cleaner and tighter. The servo's ability to control driver excursion produces the very clean bass. Also compared them to Hawthorne Augies. Augies overloaded my room and I wasn't happy enough with their mid/upper bass range, and they aren't designed for sub 25hz, which they helped me discover I wanted. Augies would do better in my old large room with concrete floor imo. Again, ime it's back to the individual room, and listeners tastes. It would be interesting to compare the Augies to these Knight 15's which have a nice mid/upper bass.
The servo has shown to be best for dialing in here. I have the original amp without the eq of new ones. I use the phase adjustment as a tone control of sorts, dialing in a fuller or lighter tone as desired. I set the xo at 40hz/24db and then adjust mains passively with baffle size, I'm limited by lack of eq equipment but am ok with this method. I actually have more gear than innitially intended, got more into it than I expected, in other things I'm more of a minimalist. Basically have been spending more time indoors than I used to.
Don

[gitarretyp]

I don't know which IB15s were discussed previously, i've never visited ib cult. There's a Dayton IB15 that's been around for several years. The IB15s i'm referring to are the acoustic elegance models to which i linked above.

I've been modeling them in xlbaffle on a 20" baffle.

Keep in mind the xmax is ~16% greater on the IB15s. The swept volume for 4 x IB15 is 12.24L vs 12.55L for 8 x SW12. The IB15 is also $100/each in sets of four. A pretty good Crown amp to power the woofers would be ~400 new, less used. You could even get something from the Crown XTi series with built-in crossover and eq functions for ~500. I would use eq in either case, so i didn't figure that into the price.

I'd really like to compare a well EQed servo subs to a similarly EQed non-servo in room.

[nodiak]

gitarretyp, The system you discribed sounds like a great idea. As a fan of the servos it's understandable I don't want the costs to appear so different. Seems it's in the $1000 range or so for your idea. Considering the 16% difference in xmax I would only say that the servo feature is unique and would keep driver excursion in check from inertia causing it to use more travel than necessary, which is unwanted. Either should have very high power handling and fill a big room. 4-6 total bass drivers is alot to keep under control. I'd like to hear and compare the two systems too.
These types of bass systems are expensive but for me they also allow more choices for mains. One benefit is they would allow to be able to just focus the speaker hobby on midbass and up drivers.
One thing about the passive 2 way ob's I'm considering in the thread is that the Radian coax's wouldn't fit in for ob (with another bass driver and only one xo point). They would work with a powered ob sub systems. They are what I use for reference now, in a 35 liter aperiodic box and sound great.
Don
 

[nodiak]

I built a 17" wide 2x2 ladder frame that holds the Knight 15's off the ground, (6" to bottom of woofer frame). Woofer is screwed into 2x2 frame so pretty close to free air. Theres no baffle, sides or bottom, just legs angled back to floor. This took care of the lower bass bloom. The Hemp 8's are mounted above on a 14" 16"w baffle.
This woofer is made for big dynamics and power handling and has a nice tight sound that matches the Hemps well. If the Alpha 15's would be similar in sonics and a few db louder they would be a good fit (although in here I'd prefer a 12" for a 14-15"w baffle). This room has more bass lift than most, and I believe makes a difference in why I can maybe get away with a single woofer with the 94db hemps. Also I'm not going for bass below ~ 80 hz (passing that off to a sub). To help with midbass fill I took the caps off the Hemp for now. Obviously rough work with no measurements, if i can get to it soon I'll pull out an old Audio Control eq/analyzer and see if any meaningful measurements a can be taken. Also have some other fr drivers that are lower spl than hemps that could blend well with Knights. Will try to get some small baffles made up for them soon. I'm glad the Knights have hope as they have great sound.
Don

[nodiak]

Have been using the 15" Knights with 4.5" Pioneer fr on top. Good spl match, great tone from both, nice blend. These woofers can handle ALOT of power and stay controlled and tight sounding. Also spl match with 8" hemps was improved when I let the hemps run full range. It's turned out to be a good driver. I'd love to be able to compare to some of the other choices down the road.
Don