Hi all,
After listening to a pair of OB speakers (in a relatively large baffle, I admit) I'm considering an experiment with a relatively small OB design and was hoping to get a few ideas on what pitfalls I should expect aside from what I've already read about on the linkwitz site, amongst a few other threads on this forum.
I'm considering the Tang Band W4-657SH 4" Aluminum Driver assisted on the top end by an Aurasound NT1-204-8D 3/4" Titanium Dome Tweeter, probably crossed somewhere in the 4.5 KHz range.
I've done some research on OB, the primary part of which seems to indicate that the low end response will suffer. In the name of futility since I'm interested in the OB concept, and am willing to sacrifice some raw materials in the name of learning, how ugly is this going to end up being since I'm using relatively low Qts drivers with low Sd? I planned on adding a small subwoofer and the primary objective is more of a home theatre application. I figure if I really mess this up, I could probably convert the system into a small set of speakers for the bedroom or computer, or possibly even find a small set of enclosures to turn them into HT satellites.
I suppose my biggest concern is that I'll have to run the subwoofer at a much higher cutoff point and be limited by localization of the subwoofer with respect to the placement of the speakers. Will it be possible to create a baffle of approximately 8"x12" with 15 degree 'wings' of approximately 4" that is going to allow this driver to reach down to 120 Hz or is this entirely unrealistic? All my research seems to indicate that anything under an 8" driver is probably a pipe dream, but at the price of the components (<$35 plus crossover materials or pre-built?) I suppose I could flub the baffle and build a small-enclosure afterwards at only the time and expense of the baffle materials.
Your thoughts are most welcome prior to my foray into futility!
P.S. I've not dabbled in crossover design (yet?) but am electronically competent and could build nearly any of the circuits I've read about. At the moment, I'm considering a pre-made PE crossover but have my reservations.
After listening to a pair of OB speakers (in a relatively large baffle, I admit) I'm considering an experiment with a relatively small OB design and was hoping to get a few ideas on what pitfalls I should expect aside from what I've already read about on the linkwitz site, amongst a few other threads on this forum.
I'm considering the Tang Band W4-657SH 4" Aluminum Driver assisted on the top end by an Aurasound NT1-204-8D 3/4" Titanium Dome Tweeter, probably crossed somewhere in the 4.5 KHz range.
I've done some research on OB, the primary part of which seems to indicate that the low end response will suffer. In the name of futility since I'm interested in the OB concept, and am willing to sacrifice some raw materials in the name of learning, how ugly is this going to end up being since I'm using relatively low Qts drivers with low Sd? I planned on adding a small subwoofer and the primary objective is more of a home theatre application. I figure if I really mess this up, I could probably convert the system into a small set of speakers for the bedroom or computer, or possibly even find a small set of enclosures to turn them into HT satellites.
I suppose my biggest concern is that I'll have to run the subwoofer at a much higher cutoff point and be limited by localization of the subwoofer with respect to the placement of the speakers. Will it be possible to create a baffle of approximately 8"x12" with 15 degree 'wings' of approximately 4" that is going to allow this driver to reach down to 120 Hz or is this entirely unrealistic? All my research seems to indicate that anything under an 8" driver is probably a pipe dream, but at the price of the components (<$35 plus crossover materials or pre-built?) I suppose I could flub the baffle and build a small-enclosure afterwards at only the time and expense of the baffle materials.
Your thoughts are most welcome prior to my foray into futility!
P.S. I've not dabbled in crossover design (yet?) but am electronically competent and could build nearly any of the circuits I've read about. At the moment, I'm considering a pre-made PE crossover but have my reservations.
Being a cheapskate myself, I tried an OB with 2 NSB, a Dayton ND20 and 2 generic buyout guitar woofers on an 18" by 46" baffle.
The NSB bottomed at a volume that we could still talk if the crossover was under about 200 hz.
I think that small driver and small baffle = limited volume capabilities.
Good luck with whatever you decide on.
Doug
The NSB bottomed at a volume that we could still talk if the crossover was under about 200 hz.
I think that small driver and small baffle = limited volume capabilities.
Good luck with whatever you decide on.
Doug
Your design won't work, to put it plainly.
You can't do a small open baffle with small drivers for any real purpose except nearfield listening. The baffle rolloff is going to be all the way through the midrange, you'll have basically a 2 way mid-tweeter.
You can add a sealed or vented woofer to match below, probably a 7" or thereabouts (though I like big woofers) and have a 3 way.
I'd go back to the drawing board, mate. Open baffles want to be big. Big drivers, big baffles.
You can't do a small open baffle with small drivers for any real purpose except nearfield listening. The baffle rolloff is going to be all the way through the midrange, you'll have basically a 2 way mid-tweeter.
You can add a sealed or vented woofer to match below, probably a 7" or thereabouts (though I like big woofers) and have a 3 way.
I'd go back to the drawing board, mate. Open baffles want to be big. Big drivers, big baffles.
badman said:
Yeah, this seems to be the consensus based on what I've read. I don't mind being wrong as long as I learn something; but, to know beforehand and still do it anyway.. well, that defines futile.
By my calculations, if I flub this, I'll essentially need some tiny enclosure that is approximately 0.15 ft.^3 with a 1.5"x4.5" port tuned to 75Hz, which will probably resonate like crazy. (I'm thinking computer multimedia systems here...)
Anyway, I'll try to stay on topic with the OB idea, despite how crazy it seems or the certainty of the failed experiment. Thanks for your input!
You can probably make this work but you will need helper woofers. In a small room smallish drivers can work if they have a high Qts but low Qts small driver needs to be treated as a wide range midrange.
I would be inclined to skip the tweeter and take care of the bottom end. That TB doesn't really need much help on the top end.
You would have to make the baffle about 14 to 15 inches across but something like this http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-330 is pretty cheap and would give you an affordable look see. If you like then you can upgrade.
I did similar with a 10". For a picture of the raw baffle see the bottom of this thread.
http://www.hawthorneaudio.com/forums/viewtopic.php?f=2&t=1174&p=14423#p14423
These have now become knick knack table speakers which I use daily. I am working on active crossover design right now but it works surprisingly well using the tone controls of the old receiver that is driving the woofers as a crossover.
mike
I would be inclined to skip the tweeter and take care of the bottom end. That TB doesn't really need much help on the top end.
You would have to make the baffle about 14 to 15 inches across but something like this http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-330 is pretty cheap and would give you an affordable look see. If you like then you can upgrade.
I did similar with a 10". For a picture of the raw baffle see the bottom of this thread.
http://www.hawthorneaudio.com/forums/viewtopic.php?f=2&t=1174&p=14423#p14423
These have now become knick knack table speakers which I use daily. I am working on active crossover design right now but it works surprisingly well using the tone controls of the old receiver that is driving the woofers as a crossover.
mike
I did many experimentation with "Small OB" to the point of obsession. Tried multiple variations like hybrid, etc. and it was a complete failure. There is simply no bass, and while listening to pure midrange is good, it's not so nice after awhile
My conclusion was there must be a minimum of 10" woofer which is equalised actively. This will give "decent" bass.
Add another 10" and you get good bass.
Also do a search on "Manzanita OB". It uses a tweeter and 12" woofer and looks small (ish). It's also passive.
My conclusion was there must be a minimum of 10" woofer which is equalised actively. This will give "decent" bass.
Add another 10" and you get good bass.
Also do a search on "Manzanita OB". It uses a tweeter and 12" woofer and looks small (ish). It's also passive.
I've been looking at the same thing and am going to use Martin J. King's U-frame idea here and pair it with a fullrange driver. The U-frame is only 17.5" x 17.5" x 8.25" (WxHxD). Mount a baffle above the U-frame for a fullrange driver and it should work out well.
Instead of using the Eminence Alpha 15A's MJK suggests, I have some cheap Goldwood GW-215s that I'm going to try. The driver is also 15" but has a higher Qts. In an earlier OB project I paired these drivers with HiVi B3Ns and was very happy with the results so I'll probably try B3Ns as well again. (Coincidently I also have a pair of Alphas I can try).
One concern I have is the crossover. I have an Behringer CX3400 (analogue) active crossover that only allows 4th-order Linkwitz-Riley filters. In MJK's example he used a 2-order Linkwitz-Riley low-pass filter which helped flatten the rising response of the U-frame. When using the CX3400 I have to set the low pass point lower to reduce the rising response problem. But now in modelling the the design I'm getting a dip in the freq. resp. at the crossover point because the B3N in a smaller baffle is rolling off early.
Other than increasing the baffle size for the B3N I wonder if anyone has any other suggestions to try? I'd like to avoid using the passive 2nd-order filter due to the cost of the components required (particularly the large inductors).
Instead of using the Eminence Alpha 15A's MJK suggests, I have some cheap Goldwood GW-215s that I'm going to try. The driver is also 15" but has a higher Qts. In an earlier OB project I paired these drivers with HiVi B3Ns and was very happy with the results so I'll probably try B3Ns as well again. (Coincidently I also have a pair of Alphas I can try).
One concern I have is the crossover. I have an Behringer CX3400 (analogue) active crossover that only allows 4th-order Linkwitz-Riley filters. In MJK's example he used a 2-order Linkwitz-Riley low-pass filter which helped flatten the rising response of the U-frame. When using the CX3400 I have to set the low pass point lower to reduce the rising response problem. But now in modelling the the design I'm getting a dip in the freq. resp. at the crossover point because the B3N in a smaller baffle is rolling off early.
Other than increasing the baffle size for the B3N I wonder if anyone has any other suggestions to try? I'd like to avoid using the passive 2nd-order filter due to the cost of the components required (particularly the large inductors).
gainphile said:I did many experimentation with "Small OB" to the point of obsession. Tried multiple variations like hybrid, etc. and it was a complete failure. There is simply no bass, and while listening to pure midrange is good, it's not so nice after awhile
My conclusion was there must be a minimum of 10" woofer which is equalised actively. This will give "decent" bass.
Add another 10" and you get good bass.
Also do a search on "Manzanita OB". It uses a tweeter and 12" woofer and looks small (ish). It's also passive.
I actually went over your site with a fine-toothed comb the other night while concocting the idea - thanks for your insight!
It looks like that .15 ft.^3 enclosure is looking nicer by the post... and my driver selection is beyond futile.
If I stick with that selection of drivers, I might still give it a shot. Materials are cheap and I'd still like to go down in flames on a good effort.
Unfortunately, a 10" or 12" 'speaker on a board' would get categorically denied based on WAF alone. 
You could try a passive line-level filter:
http://www.t-linespeakers.org/tech/filters/passiveHLxo.html
If you don't have a sub, you could also try using the high and low outputs of the 3400 to give you independent control of the two rolloff points. But I suspect you'll need an overlap, and I'm not sure the 3400 can do that (i.e. a low-mid XO that's higher than the mid-high XO).
The PE Goldwood series of speakers has quite a few small 5-8" woofers with high Qts (.6 to 1.5) for very cheap prices. Why not try one of those coupled with your chosen tweeter. Not top notch sound quality but can work out.
Say something like these...
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-315
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-355
Or the bicone could be used without tweeter but has lower xmax which could be limiting depending on room size.
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-379
with your subwoofer crossover cranked up to the low 100's might just work. If not just put them in larger baffle for your garage system.
Say something like these...
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-315
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-355
Or the bicone could be used without tweeter but has lower xmax which could be limiting depending on room size.
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-379
with your subwoofer crossover cranked up to the low 100's might just work. If not just put them in larger baffle for your garage system.
I tried mounting 2*Tangband 871S in parallel on OB and listened to the sound which was very disappointing.
There was no soundstage, very close in. I knew from many sources that the TB 871S sounded very good in vented cabinet, in my case I did not get good sound. One explanation is small drivers don't make good sounding OB.
You need at least 5" midrange/full range and at least 10"woofer(better dual) in OB the sound will open up.
There was no soundstage, very close in. I knew from many sources that the TB 871S sounded very good in vented cabinet, in my case I did not get good sound. One explanation is small drivers don't make good sounding OB.
You need at least 5" midrange/full range and at least 10"woofer(better dual) in OB the sound will open up.
WAF ..... Lord I hate that expression. When did the source of music become the decision of our wives? Are speakers supposed to look like flower pots or photos of her parents? Isn't SOUND the point? Yeah, yeah, I know. Me too.
Anyhoo .... I've experimented with all of it.
Question is, what is bass if WAF is primary? I've run a series of NSB's OB in the Computer room and they sound great that way but granted 120 at best - corner loaded. Closest I've come to reasonable bass ( guessin 80) would have been a pair of 8" run OB. 10" does seem to be the least you're gona get by with in OB configuration .
How bout compromise if OB sound is what you're after? OB mains and box subs or IB subs? Will she let you cut holes in the wall? Wall treatments will cover that and many think IB bass even more natural than OB bass. Is it her or you that wants the bass?
My wife wants the subs turned down to near nothing when watching DVD's because she finds it irritating but likes it when listening to music.
Decisions, decisions.
I'm just wondering how you're gona get anything near to even 50 even in a box if a footprint of 10" is too wide or do you have a place for a box if you chose to do a hybrid system?
If that were the case maybe the new Dayton FR Reference might be a consideration. Pretty high QTS.
Bluto
Anyhoo .... I've experimented with all of it.
Question is, what is bass if WAF is primary? I've run a series of NSB's OB in the Computer room and they sound great that way but granted 120 at best - corner loaded. Closest I've come to reasonable bass ( guessin 80) would have been a pair of 8" run OB. 10" does seem to be the least you're gona get by with in OB configuration .
How bout compromise if OB sound is what you're after? OB mains and box subs or IB subs? Will she let you cut holes in the wall? Wall treatments will cover that and many think IB bass even more natural than OB bass. Is it her or you that wants the bass?
My wife wants the subs turned down to near nothing when watching DVD's because she finds it irritating but likes it when listening to music.
Decisions, decisions.
I'm just wondering how you're gona get anything near to even 50 even in a box if a footprint of 10" is too wide or do you have a place for a box if you chose to do a hybrid system?
If that were the case maybe the new Dayton FR Reference might be a consideration. Pretty high QTS.
Bluto
Gainphile -
You keep comin through for me! Thanks for link on 'Manzanita' ! How did I miss that?
Best I've seen since Hawthorne and just spent about an hour reading on it. Thus far I'm of the opinion it's likely a better design, drivers seem superior, will watch thread and study further.
Thanks - Bluto
You keep comin through for me! Thanks for link on 'Manzanita' ! How did I miss that?
Best I've seen since Hawthorne and just spent about an hour reading on it. Thus far I'm of the opinion it's likely a better design, drivers seem superior, will watch thread and study further.
Thanks - Bluto
I knocked up a small OB experiment a couple of weeks back.
Drivers were some PE buyout 6-inch I think they're ARs. AL cone, w/ the smooth bowl no dustcap style. Cast frame. Tweeters are the Dayton silk dome. Both drivers are shielded, I think. Can't find the PE page on the 6-in any more, and they didn't come with a spec sheet...
I put them in a u-frame made from scrap. 1 6in, 1 tweeter, 12in wide by 24 tall by 6 deep.
I'm pretty suprised by how much bass they make. Not shakin the earth, but satisfying in the basement even when I'm 10 or 15 feet away.
The crossover sounds like it was made by a retarded monkey, but it's just a cap on the tweeter (@ 4khz) that's all I had layin around...
Anyway, my OB experiment with TB w3-871s was not satisfying (tho it had positive aspects), but these are quite satisfactory.
Drivers were some PE buyout 6-inch I think they're ARs. AL cone, w/ the smooth bowl no dustcap style. Cast frame. Tweeters are the Dayton silk dome. Both drivers are shielded, I think. Can't find the PE page on the 6-in any more, and they didn't come with a spec sheet...
I put them in a u-frame made from scrap. 1 6in, 1 tweeter, 12in wide by 24 tall by 6 deep.
I'm pretty suprised by how much bass they make. Not shakin the earth, but satisfying in the basement even when I'm 10 or 15 feet away.
The crossover sounds like it was made by a retarded monkey, but it's just a cap on the tweeter (@ 4khz) that's all I had layin around...
Anyway, my OB experiment with TB w3-871s was not satisfying (tho it had positive aspects), but these are quite satisfactory.
Just got a new PE flier in the mail today and it has a couple possibilities worth serious consideration.
Audax 6.5
I bet that one would be very nice.
Paper Cone Buyout
Would have to cross to the tweeter lower than the Audax no doubt but a very nice Q for your application and good xmax. The very high Q helps quite a bit with small baffle.
mike
Audax 6.5
I bet that one would be very nice.
Paper Cone Buyout
Would have to cross to the tweeter lower than the Audax no doubt but a very nice Q for your application and good xmax. The very high Q helps quite a bit with small baffle.
mike
I agree with Gainphile's comments about lack of bass using small woofers posted above. I looked at the Manzanita OB thread and modeled some of the small woofer suggestions above with Martin King's MathCad worksheet. Unfortunately it seems for OBs "there's no substitute for displacement" (and high Qts). None will produce significant levels of bass unless the woofer is large (meaning 12" or over), has a high Qts (over 0.7), and/or you're willing to use EQ to compensate. (I'll refrain from making any jokes here!).
So unless you're looking at nearfield listening only at lower SPLs (significant levels of bass EQ will quickly overwhelm your woofer), an OB has to be large. Consequently I've moved to the idea of making a U- or H-frame as a seperate subwoofer only and pairing it with small OB satellites, sealed box satellites, or something else.
Tony Gee of Humble Homemade HiFi had this to say about u-frame subwoofers in comparison to other types: "The next step was to add an open-backed enclosure, a so called U-frame making the system more practical and at the same time extending the bass response even further. Also there was a significant increase in efficiency. Bass from these U-frames was perfect! Extremely well defined, totally free from any colouration, deep and easy. The downside is that there is a "sweet-spot" in the bass." He ended up ging with a sealed box design using a 21" woofer (!).
I'm surprised that there is a "sweet-spot" to u-frames if anything I would've predicted that the cardioid response pattern of u-frames (or OBs) would have less of a "sweet-spot" because it would excite fewer room nodes (yes?).
Sorry I realize that this is straying a little off-topic.
So unless you're looking at nearfield listening only at lower SPLs (significant levels of bass EQ will quickly overwhelm your woofer), an OB has to be large. Consequently I've moved to the idea of making a U- or H-frame as a seperate subwoofer only and pairing it with small OB satellites, sealed box satellites, or something else.
Tony Gee of Humble Homemade HiFi had this to say about u-frame subwoofers in comparison to other types: "The next step was to add an open-backed enclosure, a so called U-frame making the system more practical and at the same time extending the bass response even further. Also there was a significant increase in efficiency. Bass from these U-frames was perfect! Extremely well defined, totally free from any colouration, deep and easy. The downside is that there is a "sweet-spot" in the bass." He ended up ging with a sealed box design using a 21" woofer (!).
I'm surprised that there is a "sweet-spot" to u-frames if anything I would've predicted that the cardioid response pattern of u-frames (or OBs) would have less of a "sweet-spot" because it would excite fewer room nodes (yes?).
Sorry I realize that this is straying a little off-topic.
gainphile said:Why not use 5.6" and 2" aura instead, and if you don't like it convert them into the Plutos
The Plutos would meet WAF standards if finished correctly, but building amplifiers is still well out of reach from my current capabilities. I wonder if anyone has developed a passive crossover for that particular arrangement of drivers, including the Seas L16RN-SL. This is totally O/T at this point, but I don't understand how that driver is a direct replacement for its Peerless cousin without elongating the primary tube to augment the enclosure volume. If someone were to come up with a crossover design, this would be more interesting to me. To that end, I guess I would still be rummaging around for a suitable amplifier.. but that's once again severely O/T.
Yes the pluto is very small and slender. It looks noticeably more slender than any floorstander out there.
I haven't seen a passive version of Pluto yet, although it shouldnt be too hard. Cross them high order at 1kHz basically. For bass EQ, just simply use amplifier with tone control. But the notch filters maybe a bit difficult.
But the pluto needs large room. I played them in my study room which is 3x4m and they sound really bad. No bass and smeared. I put them in my living room about 5x7m, away from walls ... wow.
Amps are easy, if you have the experience to troubleshoot hum, buzz etc. then build gainclones. Otherwise go to second-hand shop and grab $50 old amps. My amps for pluto is about 20yrs old a JC-Penney one bought for $60 at that time. You can't have "audiophile" mindset though (like signal purity, PRAT, etc.) but an 'engineer' ear rather, he..he..
Btw. both the Peerless and Seas are too expensive to import here so I just use some 5.5" lying around and it's fine. Cabinet size for sealed enclosure is not too critical, maybe just a bit different on Q. There is no substitute for the tweeters however.
Going back the topic of small OB, try it anyway and let us know how it goes
I haven't seen a passive version of Pluto yet, although it shouldnt be too hard. Cross them high order at 1kHz basically. For bass EQ, just simply use amplifier with tone control. But the notch filters maybe a bit difficult.
But the pluto needs large room. I played them in my study room which is 3x4m and they sound really bad. No bass and smeared. I put them in my living room about 5x7m, away from walls ... wow.
Amps are easy, if you have the experience to troubleshoot hum, buzz etc. then build gainclones. Otherwise go to second-hand shop and grab $50 old amps. My amps for pluto is about 20yrs old a JC-Penney one bought for $60 at that time. You can't have "audiophile" mindset though (like signal purity, PRAT, etc.) but an 'engineer' ear rather, he..he..
Btw. both the Peerless and Seas are too expensive to import here so I just use some 5.5" lying around and it's fine. Cabinet size for sealed enclosure is not too critical, maybe just a bit different on Q. There is no substitute for the tweeters however.
Going back the topic of small OB, try it anyway and let us know how it goes
p0lar said:
Siegfried is not afraid of using active filters like the Linkwitz Transform to achieve the frequency response he wants. The approach gives a lot more flexibility in driver selection.
The Peerless driver has a bridged-T circuit correcting its response which gets deleted when the Seas is used with its more appropriate Thiele-Small parameters.
Pluto-2 adds a Linkwitz Transform yielding a second order Butterworth roll-off at 40Hz.
If someone were to come up with a crossover design, this would be more interesting to me. To that end, I guess I would still be rummaging around for a suitable amplifier.. but that's once again severely O/T.
The electronics are easy to build especially if you use a nice soldering iron. I'm real fond of the Metcal I picked up on E-bay - the ergonomics are pretty much like using a pen except you have a 600 degree soldering tip instead of ink at the end.
The boards have test points after each circuit, the plans package includes a chart of what the outputs should be at each point for various input frequencies, and SL will ship you a CD with test tones if you don't have a signal generator (which can be done in software on a laptop with a headphone output)./
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