How would you design the ultimate small speaker?

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Challenge: How would you design the ultimate small speaker?

Imagine you had unlimited budget and tooling, and you want to build the best sounding small speaker possible, how would you go about designing this?

Restrictions:

1) The drivers used must be ones that can be bought. However, you can modify the drivers though. You just can't ask a manufacturer to make a custom driver.

2) The external box volume cannot exceed 0.25 cubic feet, and the width of the speaker cannot exceed 6''. The internal volume will be smaller. I purposely defined max size to be an external volume figure to make the choice of wall thickness in this design. The 6'' width is a very strict limit. Originally I wanted it to be 5''.

3) The speaker should be capable of good bass extension (at least 50Hz) and SPL so a subwoofer is not needed for music at normal volumes. DSP's are allowed, but the woofer must be able to handle it.

Second scenario: What if the budget per speaker is reduced to $500? How would that change the design?

Unleash your creativity. How would you cheat physics?

EDIT: I'll offer one design as an example to clear any confusions. Build an MTM with 2x Scanspeak 12MU woofers and a Scanspeak D3004/6040 tweeter and 4x Peerless 4'' passive radiators modified with extra mass to tune to 50Hz in a box 13'' x 5.5'' x 5'' HWD and use a miniDSP as a crossover and bass booster.
 
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How do you define ultimate?

So small is 7 litres. If that is external, say 5-6 litre internal and could be maximized by using something like carbon fibre for the enclosure to reduce the volume taken up by he box material.

The 6" dimension is contradictory. With a max dimension of 6" you have a maximum volume of 3.5 litre external. 6^3 = 216 in^3 = 3.54 L.

How do you define the low frequency cutoff… to humans Toole has shown it is not F3, one is better to look at F10 (or maybe F6)

An Alpair 7 MOAP would fit in that size (internal 7 L -- althou it would prefer a couple more litres). F10 ~42 Hz, F6 about 50. I'd EnABL it. No XO (XOs are evil), quite neutral, good HF extension, phase is kept intact.

If you take it down to 6 L, F10 ~42 Hz, F6 about 50 but a Hz or so higher than 7L.

Won't play overly loud (but the size limitation makes that so for anything).

dave
 
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Isnt thie idea of a tiny speaker with maximum extension answered with the mini onkens?

They certainly do a good job.

Now, if the limit was 0.28 internal, then ive answered that with the LM-1. Not the last word in small bass, but ultimate small 2 way for me at just under $500 per pair.

It still has an XO that screws up phase coherence and the drivers have a C-C greater than ¼ wavelength of the XO (1.8 kHz = 1.9" ¼ wl)

dave
 
How do you define ultimate?

So small is 7 litres. If that is external, say 5-6 litre internal and could be maximized by using something like carbon fibre for the enclosure to reduce the volume taken up by he box material.

The 6" dimension is contradictory. With a max dimension of 6" you have a maximum volume of 3.5 litre external. 6^3 = 216 in^3 = 3.54 L.

How do you define the low frequency cutoff… to humans Toole has shown it is not F3, one is better to look at F10 (or maybe F6)

An Alpair 7 MOAP would fit in that size (internal 7 L -- althou it would prefer a couple more litres). F10 ~42 Hz, F6 about 50. I'd EnABL it. No XO (XOs are evil), quite neutral, good HF extension, phase is kept intact.

If you take it down to 6 L, F10 ~42 Hz, F6 about 50 but a Hz or so higher than 7L.

Won't play overly loud (but the size limitation makes that so for anything).

dave

Ultimate, as in take the performance and sound quality of very high quality bookshelf/floor speakers, and squeeze as much of it as possible to a small speaker with the help of DSP. The speaker must be active, as I don't see how a non active speaker can possibly extract as much performance as possible from a small speaker.

The 6'' restriction is only for 1 dimension. And it is ~7 L external, so internal volume is smaller depending on wall thickness choices.
 
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...DSP. The speaker must be active, as I don't see how a non active speaker can possibly extract as much performance as possible from a small speaker.
Efficiency trades against bandwidth so a lower fs reduces sensitivity. This can be a consideration with a smaller voice coil. A certain output at 50Hz will be proportional to cone area and excursion.

You can equalise with a crossover, but not get around these issues.
 
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Ultimate, as in take the performance and sound quality of very high quality bookshelf/floor speakers, and squeeze as much of it as possible to a small speaker with the help of DSP

That is not a sufficient definition. Even the best speakers have so far to go before being ultimate you can have any number of equally valid speakers that are quite different from each other.

dave
 
No, no limits on number of drivers, as long as you can fit it in a box under 0.25 cu ft.

You can do whatever you want, as long as it is under the size restriction and is capable of reasonable bass output.


Oh, ok. in thatcase, i haveto return to a graduate project from ga tech hich used a methane flame with a voice coil valve. lotsofbass there. of course, would require about 30 feet front and back for clearance.

Best,

Erik
 
That is not a sufficient definition. Even the best speakers have so far to go before being ultimate you can have any number of equally valid speakers that are quite different from each other.

dave

Yes, there can be multiple equally valid speakers that are quite different from each other, and that's OK.

Originally, "ultimate" is a definition up for your interpretation. I offered an interpretation of "ultimate" as getting as much performance of extremely good standard sized speakers (bookshelf and floorstanding speakers) as possible in a small speaker. Although, personally, when the speaker is this small, I feel that "ultimate" is "minimum compromises"

When I put such a strict limit on size, there are serious compromises that must be made. I thought it would be interesting to see what kind of designs people would come up with to minimize compromises.
 
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The whole center image in my frontal lobe is a bit odd, but otherwise a nice set of open back cans can image well.

If I needed to use a pair of cabinets this small I would load them with Seas L12 or C16 coaxials or Kef Q100 coaxials and deal with the lack of low end.
 
LOW COST.... parts from my my closet + 16mm plywood:
BOX EXTERIOR = 432 cubic inches: 6" wide x 10" high x 7.2" deep
-SB-Acoustics...SB26STCN...1' dome tweeter(option: 16mm time-step baffle)
-SB-Acoustics...SB15NRX-08...5" midbass...equalized with 35Hz Linkwitz Transform.
(~$80 in speakers + simple 2Khz LR2 passive Xover + amp with linkwitz transform + cheap plywood cabinet)

HIGH COST...some machining + custom 3/8" thick aluminum+braced_sides case.
-Satori MW16P-08 with portion of the Left+Right front flange machined off.
-Satori TW29 1" dome tweeter with ring-portion of the front flange unscrewed.
(~$280 in speakers + amp with linkwitz transform + EXPENSIVE aluminum case)
 

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You can't ask the question of the ultimate speaker without asking the question of the ultimate listening room !

Design the room first, then only build the speaker which include the few trade offs you must choose for the room even if ultimate budget for building this last !

Take into acount the electronic in the speaker design

But there will be still a problem : few reccordings allow a not too much EQ work and real dynamic (around 30 dB to 130 dB (100 dB gap) assuming the electronics and speaker noise floor can follow... in the case the room can !

Ultimatly, as it's also a question of aesthetic perception than listening music, you may not like the result...

The low end is still problematic : ever heard the lowest 16 Hz of a grand orgue in a huge gothic Church ? ... you understand immediatly, it's not easy task ! PA could do but what about the whole tonal balance equilibrium in the room !

But we have the luck to have computers todays, integration is easier than before.
 
I'd go for a FAST, with the nicest 5" mini-sub you can find, make the entire back a passive radiator tuned low (30Hz ish), 2" wideband unit coming in around 300Hz, and then throw DSP and power at it. The mini-sub is likely to be power hungry, so I'd want 2-300w of clean power for those.

Chris
 
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