That driver looks like it would perform well in a 4th order bandpass box also... Looks like it would reach ~110 db from ~20-50 Hz in a 200 l enclosure (120r/80f) with ~300 W driving it (linked plot).
-Doug
-Doug
bottomfeeder said:
Pretty big: ~18"x18"x50", 22"x22"x32", or 5' high 16" sonotube.
I am planning to build one of these, but not sure what box I'd prefer (and where to put it). The port is ~25" x 6" diameter so that limits things a bit.
-Doug
You definetly dont want the port on the end of a 5' sonotube ,you will get some cancellation . Cant fit 6x25 in a 32" tall tube . Have you thought about a building a square port ?DougSmith said:
it will be shorter and may work !!
Where did you get your cabinet/port sizes from ?
Why dont you build it sealed first ?
You may like the sound .
How much power are you going to drive the sub with ?
bottomfeeder said:
Why cancellation? The port is the only way out for the sound. I want to build a trio of bandpass subs according to Earl Geddes' design philosophy to go with the Abbey's I currently have on order: two broadband for the ~50-150 Hz range (with B&C drivers) and one ULF (so far the Dayton HF 15" is looking attractive). It's a bit ambitious, but I enjoy the challenge of doing the research, learning and building things myself. I'm not sure how to model square ports, but that might be interesting. I have been using WinISD, Unibox and Speak to do the modeling (WinISD for initlal approximation and the others to verify and refine things). Here are some mockups of the designs I am thinking of (rectangular box link and sonotube link). I don't see any problem with the port length, only the fact that they come fairly close to the box and baffle walls in these designs (I would welcome any comments from folks who have tried something like this). I am planning to use an outboard 3-channel amp capable of putting out ~200W into 8ohms or ~300W into 4ohms and Behringer DCX2496 for filters and bass management in conjunction with my existing Yamaha AVR.
-Doug
at 20 hertz the wavelength is 55 feet but at 100 hz the wavelength is 11 feet so there will be some cancellation and it will be partially out of phase out of phase . Well if winisd said it was it is big enough I guess thats fine .DougSmith said:
Sounds small though !
So these are bandpass boxes? So how far was curve down in DB at 20 hz ?
Bandpass is nice , I have not built any but tried a alumipro bp12 in my truck (127 db at 40 hz from a single 12") it made my headliner slap against the roof ! and that is a 2 cubic box .
I realize thats car stuff and we are talking of home stuff here !
I talked to a guy who tried one at home , it was awesome !
I thought a 25" port tube in a 32" tube was to close .
bottomfeeder said:
Well, that is the beauty of using 3 subs with those ranges. The placement, phase and level on each can be adjusted independently to create a uniform sound field, compensating for the kinds of cancellation effects you are talking about. The rolloff characteristics at ~20Hz can be seen in my earlier post.
-Doug
DougSmith said:
On your 50" 7.36 cubic that should sound good !
I still would go sealed (check it winisd) let room gain bring up the low end where it hugely improve group deley , improve transient response (reduce boominess) avoid tuning issues, etc
Bottonfeeder... Yes, group delay is pretty high for that bandpass design (peak of ~39 ms at ~20 Hz), but it is still less than 1 cycle across the design bandwidth and most likely wouldn't be a problem. A sealed design (190 l box) does indeed have much lower group delay, but that goes up to ~15 ms when a low pass filter is added to create the desired roll-off at 50 Hz. Overall it has ~2db less response at 20Hz (probably not a big deal, as you say, especially since my room is very long and has a mode at ~20 Hz). One potential issue, though, is that the cone excursion goes way past xmax with 300W driving it.
Looking at a number of different designs, I see that those which produce a curve such as the one I linked previously (flat top with fairly steep rolloff on either side) also have fairly high group delay. On the other hand, those that produce a more rounded curve with smoother rolloff have lower group delay. I am now thinking that this may be more desirable. Another driver I modeled is the Acoustic Elegance AV15-H, which has similar output at 20Hz to the Dayton bandpass (in a similar sized enclosure) and produces a more rounded curve with lower group delay (peak of ~21 ms at ~20 Hz, which is less than half a cycle). Overall, that looks like it will mate better with the B&C broadband subs I am already committed to (drivers on order), curves are linked here: SPL, Group Delay.
-Doug
Looking at a number of different designs, I see that those which produce a curve such as the one I linked previously (flat top with fairly steep rolloff on either side) also have fairly high group delay. On the other hand, those that produce a more rounded curve with smoother rolloff have lower group delay. I am now thinking that this may be more desirable. Another driver I modeled is the Acoustic Elegance AV15-H, which has similar output at 20Hz to the Dayton bandpass (in a similar sized enclosure) and produces a more rounded curve with lower group delay (peak of ~21 ms at ~20 Hz, which is less than half a cycle). Overall, that looks like it will mate better with the B&C broadband subs I am already committed to (drivers on order), curves are linked here: SPL, Group Delay.
-Doug
Wow looks like you will be down 4 db 20-100 HZ !
Thats awesome !
Have you choosen a amp ?
I recomend something with R&L gain adjustments , the graph looks close but the amp adjustment will work like a 2 ch eq allowing for variances in your room to blend.
Are you using a externall xover ?
This setup reminds me of a schametic I have been looking at for 15 years , its a externall electronic xover that splits the sub signal
with the idea you get a good sub for the 20 hz area and another to fill the 50hz up .
Please post some pix of your cabinet building !!
Thats awesome !
Have you choosen a amp ?
I recomend something with R&L gain adjustments , the graph looks close but the amp adjustment will work like a 2 ch eq allowing for variances in your room to blend.
Are you using a externall xover ?
This setup reminds me of a schametic I have been looking at for 15 years , its a externall electronic xover that splits the sub signal
with the idea you get a good sub for the 20 hz area and another to fill the 50hz up .
Please post some pix of your cabinet building !!
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