Advice on open baffle

Hello! Yes, 40 Hz should not be any problem, even without DSP. The 12" driver has an total Q = 0.74 and a resonance frequency at 32 Hz. You need a baffle width of about 25 inch. Myself use a OB at 24" + tiny sides and two 15" drivers, and they go below 40 Hz in a ordinary room. Without any DSP or analog filter.
 
Thanks, I was thinking to have a tall baffle about 10in wide on top with large chamfers for the full range driver then widening to about 16 inches with wings angled slightly back to extend the baffle to about 30in total and placing the woofer low on the baffle. Are there any things I need to watch out for with this design?
 
I have the sub these were intended for. (Sub is a smaller volume than their recommended enclosures sizes - Hmmmm). Hopefully you're using separate amplifiers, as the efficiency seems low at ~90; to use a single amp driving both the woofer efficiency must be > than the full range, which is typically pretty high.

I've already committed to 18" in my OBs, but I'm still interested on how your design turns out. I use DSP to make it easy to tune, with crossovers at line level using separate amps...
 
Hi again, Etaoin! Despite OB:s are pretty forgiving there are always more to watch out for... My main problem is higher in the frequency domain (shrilling sound from 500-3000 Hz, yeck! I might ask for advice later) but the bass is deep, punchy and natural and free from severe resonances.


There is a lot of discussions here at DiyAudio about OB:s that you can look for, but the most common issue is about how one can get the bass deep enough. The way you describe, with sides smaller than the front, should be OK. With parallell sides the solution is called U-frame. Beware of tunnel-like constructions (sides deeper than front baffle width), they will work like a resonator. Bass Tuba. Nice, but not as a speaker.
 
Open Baffle

I saw these drivers 12" High Excursion Paper Cone Subwoofer Driver 4 Ohm and thought they might work well in an open baffle with a woofer assisted wideband driver like the Dayton ps 95 both have qts ~0.7 or this visation Visaton B 80 3.3" Full-Range Driver 8 Ohm. I dont need lots of spl but I would like it to hit 40hz if possible, is that realistic with dsp?

Etaoin314: Did you look at the 15" version of this driver? $10 more apiece; looks like it it would do a better job for your project goals.

I'm glad you posted....those drivers look pretty decent, and a good value.
 
I was wondering about the 15”, my concern was the higher fs, does the slightly higher qts outweigh the higher fs. My thinking was that the 12 is cheaper, smaller, and will play lower, that seemed like a good trade off for slightly lower efficiency and slightly lower qts. Is my thinking not correct here. Thanks for all the great feedback, guys!
 
Jjasniew- yes I will be biamping so I can use dsp, also my wide and drivers are a few dB down (86db) on the woofer so hopefully that all works out. I am planning for a small diameter driver to reduce beaming.

Klasdiy- yes it will be a u shape but I will use angled cuts so that it widens the further it goes back and avoiding the wings ever reaching parallel. I hope that will avoid the cupped sound.
 
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I'm all ears as to how this can work

Hello! Yes, 40 Hz should not be any problem, even without DSP. The 12" driver has an total Q = 0.74 and a resonance frequency at 32 Hz. You need a baffle width of about 25 inch. Myself use a OB at 24" + tiny sides and two 15" drivers, and they go below 40 Hz in a ordinary room. Without any DSP or analog filter.

Please, I'd like to hear how this works out so well (?)

A Q = .074 and a baffle width of 25 inches is supposed to support a 40Hz note, which has a wavelength of 28 feet.

If you can explain this to me in a satisfactory answer, I'll start construction tomorrow. Thanks !
 
Dear Scott L, I guess it is the usual room effect, not my credit. I put two pairs of Eminence Beta 15A (QTS = 0.58, FR = 35Hz) in a lousy test rig made of thin chipboard and placed them in the living room, about 4x6 m (12x18 ft). Distance to back wall is slightly over one meter (3 ft). Up to about 300 Hz it works out really well. I have done a not-so-precisly (room resonances!) frequency-SPL measurement both by ear and a descent SPL meter and it has useful output down to 40 Hz.


Double bass and drums are really realistic both in timbre and power. And size! I am surprised. The stuff is really cheap. I plan to run them i a larger room (a class room in the school where I work) next week. I will report in a few days.
 
Short report from the promised test in a larger room (approx. 8x12 m/25x40 ft): As I could guess the test revealed that one need bigger OB:s in bigger rooms... No deep bass at all, an annoyng resonant top between 50 and 100 Hz... But well back in my living room they thrive.
 
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Short report from the promised test in a larger room (approx. 8x12 m/25x40 ft): As I could guess the test revealed that one need bigger OB:s in bigger rooms... No deep bass at all, an annoyng resonant top between 50 and 100 Hz... But well back in my living room they thrive.

Thank you (!) for your honest report.
Remember, 40Hz is a wavelength of 28 feet. Very difficult to reproduce, if nothing prevents the acoustic short circuit to occur. Front-to-back wave separation is Loudspeaker 101.

A good audio buddy of mine also claims 40hz from his OB, in a smaller type room. I have listened over there. He's got a room lift that enhances the negative wave, but it's got no punch.
 
Ah. I have no really punch, not that belly-hitting from big PA gears or a real kick drum--but a have the size and ear impact, in some recordings, of the real thing. I have heard OB doesn't give that punch, i takes a closed box for that. That's one thing I can live with (hm...), the openess of the sound is worth it. Not unlike the Apogee I remember from some years ago. Big sound, no fist-instomach.



So, you want the punch as well? That's not the way OB do, I've heard. I was thinking of that myself and chosed OB, not closed box. And I didn't knew what I should get when I started.
 
https://www.newark.com/mcm-audio-select/55-2974/15-woofer-with-poly-conerubber/dp/80R7013

-read through the reviews, there is one in particular that mentions Qts and Fs..

Figure 2 in parallel with a baffle/frame like SL's LX521:

LX521.4 Reference loudspeaker


-if you want more "punch" you'll need more motor (lower Qe) and much higher efficiency with higher excursion and/or surface area.. and of course be willing to waste all that efficiency.

SB has a driver listed in their Audience section that seems most apt. for that (though I've not seen it offered in the US):

BIANCO-18SW450

-figure about 9 times the cost of the MCM woofer.
 
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OB "punch" has been a question on my mind for a while...

ScottG,

Are U saying that IF u want a more visceral impact from an OB design its better to go with high sensitivity, low Q drivers and waste the efficiency , as apposed to a high Q driver thats typically used I believe to get reasonable response deeper into bass?

BTW U say low Qe, did U mean low Qt?
 
Yes. Though don't forget surface area (Sd) and linear Xmax: also critical to the overall result.

It still won't have the physical impact of low Qe driver in a comparatively large sealed enclosure though.

The subjective result is more a matter of "degree".

Qe relates to the motor, Qm relates to the suspension (mostly the spider). Qts is a composite of both (like THD for non-linear harmonic distortion). Note though that the predominate factor in a lower Qts is the Qe, NOT Qm.
 
Yes, the Bianco-18SW450 8 ohms looks interesting, not yet released in Australia but priced at $299 (Au) which should be about $200 in the US.


There are two other 'Bianco' drivers that are worth considering for an Open Baffle design from SB Acoustics.

The Bianco-150B350 a 15" driver 8 ohms with an Xmax of 11 mm. ( yet to be released) $209 in Au dollars or around $140 in US dollars.


The Bianco -120B150 a 12" driver 8 ohms with an Xmax of 6.79 mm ( still to be released) $125 in Au dollars or around $140 in US dollars. Although a little small for OB as a lone driver, using two of these drivers in parallel would give a 6db boost at the lower end.

I have always considered Sd to be more important than Xmax in O.B design, Xmax quickly runs out with the lack of available damping, so if the price is not an issue the Bianco-18SW450 is probably the better investment as it may be reused as a subwoofer if the O.B design is not a successful outcome.


BIANCO-15OB350

SB Audience :: BIANCO-12OB150


C.M
 
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Yes. Though don't forget surface area (Sd) and linear Xmax: also critical to the overall result.

It still won't have the physical impact of low Qe driver in a comparatively large sealed enclosure though.

The subjective result is more a matter of "degree".

Qe relates to the motor, Qm relates to the suspension (mostly the spider). Qts is a composite of both (like THD for non-linear harmonic distortion). Note though that the predominate factor in a lower Qts is the Qe, NOT Qm.

Greetings, my brother !

At what value shall we consider "Low Qe" ? If I would be so bold as to hazard a guess, I would say, at 0.4 and below. I have a great audio buddy/friend of mine, who has been trying to educate me on drivers, as he actually builds them for competition use. Qts is not the whole story, it's only a guide. He insists it's more so the relationship between Qes and Qms and the value ratio between them. By the way, never in a million years would he consider anything remotely related to an open baffle, for anything serious in audio.