So I’ve decided to go the OB/Fullrange DIY option over the Maggies with OB subs….I guess I just appreciate a challenge!
My initial thoughts are two 15” SBAudience OB woofers for each channel…..one downfiring into SLOB type slot and the other forward facing on a 20” wide U baffle. Above would be a fullrange driver within the 6-8” class.….something that will handoff nicely to a 15” woofer in the 250-300hz range and extend to 10k…….i‘m 55 and there’s not much I can hear above 10 anyways.
My thinking here is the slot loaded woofer will extend the bottom end a little deeper. Was also considering using it in a .5 configuration and a low pass around 100hz but not sure the extra component or effort is needed since it’s going to be mechanically HF attenuated firing downward and into a slot. Thoughts?
My initial thoughts are two 15” SBAudience OB woofers for each channel…..one downfiring into SLOB type slot and the other forward facing on a 20” wide U baffle. Above would be a fullrange driver within the 6-8” class.….something that will handoff nicely to a 15” woofer in the 250-300hz range and extend to 10k…….i‘m 55 and there’s not much I can hear above 10 anyways.
My thinking here is the slot loaded woofer will extend the bottom end a little deeper. Was also considering using it in a .5 configuration and a low pass around 100hz but not sure the extra component or effort is needed since it’s going to be mechanically HF attenuated firing downward and into a slot. Thoughts?
which FR driver are you thinking of using? just curious.
And what makes you think that just one 15" woofer per channel firing near the floor in SLOB fashion is not enough? You have a VERY large room?
Keep in mind that generally OB's need a fare amount of distance from room walls to perform at their best.
Yes….large room….and lots of room behind the speakers for OB to breathe. My concern with the single downfiring woofer is integrating with the full range….the second fwd facing driver eliminates that and would allow for using the smaller fullrange driver with better off axis performance……at least that’s my reasoning. In order to get premium HF extension from an 8”, I’m gonna have to spend some $$$ I think…..but the poor off axis response will remain.
hate to break it to you...........
but, most of those designs that have a baffle less than 2' wide, the woofer has to run way up to a maybe crossed at 400hz full range (or higher).
if I remember, some run say a 50hz low pass 12db to get it to "roll" into the full range.
some links that may be helpful
https://www.blackdahlia.com/html/tip_43.html
https://www.blackdahlia.com/html/tip_83.html
https://www.blackdahlia.com/html/tip_81.html
but, most of those designs that have a baffle less than 2' wide, the woofer has to run way up to a maybe crossed at 400hz full range (or higher).
if I remember, some run say a 50hz low pass 12db to get it to "roll" into the full range.
some links that may be helpful
https://www.blackdahlia.com/html/tip_43.html
https://www.blackdahlia.com/html/tip_83.html
https://www.blackdahlia.com/html/tip_81.html
The plan is a U frame…..20” baffle…..16” deep side panels tapering to where the dipole peak can be mitigated mechanically
Have a look at these bass drivers. They look to get the job done nicely and are very inexpensive.
https://www.diyaudio.com/community/...ofer-best-for-open-baffle.187784/post-5447475
Also, I'm guessing you already saw the Papa SLOB thread?... With that large baffle you could start with the one pair down-firing and later add the other forward firing if it's needed (largely room dependant).
https://www.diyaudio.com/community/...ded-open-baffle-version-2.362482/post-7136606
I'm still very curious how the lower cost SB Acoustics SB20FRPC30-8 FR sounds in this size OB.
I'm inclined to try this kinda thing and then later (if needed) add something like an Aurum Cantus 2GSi crossed over very high or some other "super-tweeter" that doesn't go low enough to muck up the FR driver's response.
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why does if "have to"? If the driver has a low Fs and decent output below 200hz
It's best to ignore me as I have zero experience, but my critique would be that I'm anti downfiring speakers if they have reasonable mass on the cone/VC as I don't feel the effect of gravity over time can be good in terms of maintaining symmetry around a zero point. That's entirely based on intuition and comments elsewhere, not experience though.
The FE108eSigma works well, as do FF85/105/165wk
We used FF85k in one we built, probably the best one
dave
The XO point is driven by the baffle width and the baffle loss. The MJK article has the math and reasoning
dave
Yes….calculating SAG is always a good idea….the SB drivers are good to go!
Why do driver manufacturers and many speaker builders then make comments like ~0.6 ish Qts is ideal for OB use?
And why do ppl generally say that low Qts is best used in a backhorn cab?
Because they forget that most have a woofer, T/S is meaningless at the typical 300-400 Hz XO
dave
dave
well, a driver on an infinite baffle naturally rolls off at Fs/qts
so if a 30hz driver has a qts of .3, no matter how big the baffle (even infinite), it will roll off at 100hz (that may even be the F3).
Now take a 30hz driver with a floppy-ish qts, say .7, now that driver will roll off at 42hz.
But let's throw a monkey wrench at this also.
Some projects, people have liked using a stronger magnet (say qts under .4) versus a floppy woofer (such as eminence Alpha 15 with its 1.26 qts).
To me, distortion is also related to displacement.
And I believe a lower qts (stronger magnet) grips the cone and keeps it from having less distortion compared to a weaker magnet.
And a low qts is not always a backhorn.
W8-2145 was tested by hobby hifi back in 2017 with a qts of .53
"At 0.53, the resonance quality is too high for proper bass reflex tuning. The Tang-Bander looks better in a closed housing.... The w8-2145 cuts a particularly good figure as a horn driver: in the cobra horn from hobby hifi 1/2013 and 5/2015, it produces practically exactly the same frequency response as the monacor full range driver originally used there...... Assuming careful linearization of the frequency response, it achieves high-end qualities in the cobra horn."
I too had always thought rear horns are only for really stronger qts, say below .35, but you learn something every day.
so if a 30hz driver has a qts of .3, no matter how big the baffle (even infinite), it will roll off at 100hz (that may even be the F3).
Now take a 30hz driver with a floppy-ish qts, say .7, now that driver will roll off at 42hz.
But let's throw a monkey wrench at this also.
Some projects, people have liked using a stronger magnet (say qts under .4) versus a floppy woofer (such as eminence Alpha 15 with its 1.26 qts).
To me, distortion is also related to displacement.
And I believe a lower qts (stronger magnet) grips the cone and keeps it from having less distortion compared to a weaker magnet.
And a low qts is not always a backhorn.
W8-2145 was tested by hobby hifi back in 2017 with a qts of .53
"At 0.53, the resonance quality is too high for proper bass reflex tuning. The Tang-Bander looks better in a closed housing.... The w8-2145 cuts a particularly good figure as a horn driver: in the cobra horn from hobby hifi 1/2013 and 5/2015, it produces practically exactly the same frequency response as the monacor full range driver originally used there...... Assuming careful linearization of the frequency response, it achieves high-end qualities in the cobra horn."
I too had always thought rear horns are only for really stronger qts, say below .35, but you learn something every day.
If I’m not mistaken, QTS is measured on the standard infinite baffle……so if Fs is measured at 30hz on an infinite baffle with a QTS of 1 and your enclosure baffle has a calculated QTS of .75 your Fs is now 52hz.…..or the native Fs of the driver combined with that of the enclosure……hence the floppy cone comments…..the magnet is quite weak in this example.