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Which drivers for highly custom, small enclosure?

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suttondesign

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I‘ve all-but decided to use dual opposed 11” scan-speaks, so I am mounting them at either end of an 18“w box with 12” x 12” ends. about 1.25 cu ft. internal. boosting the low end using dsp. I may still ditch that for single, down-firing in slightly smaller boxes, but the first go-round is the dual, just for the fun of it. Plus I need to find a whole bunch of oversized books to conceal the baltic birch box. harder than it sounds.
 
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jaakkopetteri

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I think the asymmetric BL non-linearity would specifically show up as HD.

Looking at the third order distortion of the SB SW26, it does rise. Note the distortion scales are different, and the SW26 trace only goes to 30 Hz. And the 2kHz is far away from where this speaker should operate. Perhaps this is that non-linearity coming into play. If so, this would get worse with SPL. But the SW26 looks like a great woofer, and if you want to minimize these non-linearities, buy two for the price of one Seas L26!:cool:
Yeah, IMD shows up as harmonic distortion, but if I understand correctly, it's a more revealing measure as music is not a sine sweep - I do understand this is a controversial argument. The point about the BL being biased to counteract the airspring makes sense but I'm far from an expert. Would be interesting to see actual IMD measurements for each woofer in a compact box (or simulations by Rene :)). FWIW I can find the L26ROY for about 20% more than the SW26
 

kipman725

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Have you considered the air inside the enclosure is a non linear spring? so eventually as the air volume of the enclosure reduces it will become the dominant source of non linearity. Regardless I wouldn't worry about THD<10% in the frequency range up to 100Hz as its audibility is questionable, furthermore in domestic enviroments objects vibrating external to the speaker add both harmonicly related and non harmonicly related distortion (far more objectionable). I would worry more about maximizing output within the constraints of the system.
 

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Timmermanns has revied 10" woofers this year and 2 'pancakes' by Dayton measured aprox. same as those from SB. I really apreciate this approach, but conventional designs still go ahead regarding distorsions.
One woofer that attracted my interest was the Redcatt SW10.8 AC (maybe 10FHW on producers site, maybe OEM) with Re 5.7 Ohm (10FHW differs with 3,4 Ohm!?) , fs 26 Hz, Vas 67 L, Qts 0,4, Rms 1,6! and Xmax 13 mm, Distorsions below 1 % down to 25 Hz.
Two of them opposite in closed enclosure and plate-dsp-hypexed with 500 W?
 

MAB

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Timmermanns has revied 10" woofers this year and 2 'pancakes' by Dayton measured aprox. same as those from SB. I really apreciate this approach, but conventional designs still go ahead regarding distorsions.
One woofer that attracted my interest was the Redcatt SW10.8 AC (maybe 10FHW on producers site, maybe OEM) with Re 5.7 Ohm (10FHW differs with 3,4 Ohm!?) , fs 26 Hz, Vas 67 L, Qts 0,4, Rms 1,6! and Xmax 13 mm, Distorsions below 1 % down to 25 Hz.
Two of them opposite in closed enclosure and plate-dsp-hypexed with 500 W?
Can you provide the references to those tests? We do post references at ASR when available!
 

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Source (printed, not online available):
hobbyhifi.de 01/2023
by
Dipl. Ing. Bernd Timmermanns

'Screeenshots' :rolleyes: :
 

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MAB

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Source (printed, not online available):
hobbyhifi.de 01/2023
by
Dipl. Ing. Bernd Timmermanns

'Screeenshots' :rolleyes: :
Thanks! Sorry to make you post screen-shots!!!
My German, not so good!:cool: Fortunately, the important parts are in math and clear.:)

I've had this idea... If I find a good deal on some of these pancake woofers, build many small boxes for distributed subs. I have experimented with subs distributed around the room to flatten the nulls and peaks, but my various subwoofers are too big to be practical. I have wondered about building lots of 10" subs in small boxes, like 12 or 16, these pancakes seem good candidates, even if they have some issues compared to other drivers. This would keep them in the small displacement regime, where the non-linearities would be somewhat minimized.
It's an idea. But while these are cheaper than an L26, they are still money, and all those boxes takes time! So for now I will stay intrigued by these little pancakes.;)
 

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It's an idea. But while these are cheaper than an L26, they are still money, and all those boxes takes time! So for now I will stay intrigued by these little pancakes.;)
12-16 10" woofers ? Of what dimensions is the hall of your castle ?
Btw. even a pancake needs some volume in the back, for closed it should give Qtb around 0,5 for EQ up to 0,7 without EQ for flat response.
Going down with enclosure's volume to far will increase power need and potential harm to the coil, but with 16 woofers there might be low enough power consumption for each single one, ... perhaps.
 
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suttondesign

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For the Scan-Speak 28W 11" subwoofer, the attached gets me 1.37 cu. ft. internal volume (blue transparent box) before stuffing. I would use as much stuffing as possible. The material is 3/4" baltic birch.

I'm thinking that the end panels do not need to be thickened given the stiff box material and strong surrounding joints (dominoes, which are a kind of tenon, and some pocket screws on the inside) and the vibration-cancelling characteristics of the dual opposed drivers.

If anyone has thoughts on these issues, please share.
 

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To be clear, I have already ordered the Scan-Speak 11". The modeling for another driver does not help me.
 

MAB

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12-16 10" woofers ? Of what dimensions is the hall of your castle ?
Btw. even a pancake needs some volume in the back, for closed it should give Qtb around 0,5 for EQ up to 0,7 without EQ for flat response.
Going down with enclosure's volume to far will increase power need and potential harm to the coil, but with 16 woofers there might be low enough power consumption for each single one, ... perhaps.
I have a large basement (9 x 11 meters). I have my office, musical instruments, my electronics hobby stuff, and my main listening system. In USA we call this 'man-cave'.:cool:

Some years ago, I had four Seas X26x001, and six Seas L26 woofers from previous projects. I built them into 10 sealed enclosures, in very small sealed enclosures. I drove them with a Niles 12-channel amp. They were ugly, and wires all over the place, but I did get great bass, and learned lots about my room and room-modes in general. The amps and woofers had so much headroom, I could EQ with no worries relative to the sensitivity of my main speakers at the time... I never ran out of amplification, and the drivers barely moved even on unrealistic bass tracks. And it was a mix of the W26 Excel, two generations of L26ROY, and a pair of Rev1 L26RO4Y.:facepalm:

I didn't have sophisticated bass management back then, just level controls on the amp and marginally accurate measurements. I would like to retry this with a more modern approach.
But my mains now are JBL M2 clones: I would likely need to get lots of these drivers. But I need to finish the M2 cabinetry first!;)

People are right to point out the things like the asymmetric BL, it is really significant in the measurements!

OP bought gold-standard subs I think. Which is not a bad approach. Avoid any doubt, and prioritize the work to build the sub's cabinet. And use the headroom that will be available to EQ to flat.
 

MAB

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Impressed (by room square) ;)
Thank you.
Built by a German guy (Henry Thiele) almost 100 years ago. He ran a German restaurant in Portland, this was his farm-house and it has a very useful basement! It keeps the hobbies, and noise, out of my family's way.
 
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The 11” scan-speak drivers have arrived, finally, so today I built the box. It was a good opportunity to learn how to cut circles with a router and circle jig. The material is 3/4” baltic birch. The construction method is glued and pocket-screwed.
 

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MAB

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The 11” scan-speak drivers have arrived, finally, so today I built the box. It was a good opportunity to learn how to cut circles with a router and circle jig. The material is 3/4” baltic birch. The construction method is glued and pocket-screwed.
Can you build my M2 cabinets for me?;) That looks very nice.
 

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The 11” scan-speak drivers have arrived, finally, so today I built the box. It was a good opportunity to learn how to cut circles with a router and circle jig. The material is 3/4” baltic birch. The construction method is glued and pocket-screwed.
Maybe some braces inside would give some kind of stability and damping of enclosure resonance.
Nice work.
 
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suttondesign

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Maybe some braces inside would give some kind of stability and damping of enclosure resonance.
Nice work.
the dual config should elim a lot of that. otherwise, the thing is small enough that maybe it doesnt need additional bracing? anyone can chime in here.
 
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