how to choose a small midwoofer for a 3-way tmww design

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As the title says, I'm pretty much obsessed with 3 ways now (or should I say have come to the conclusion they're pretty much the best solution) and am somewhat startled by the bass in my b&w xt4 rebuilds-these are 3 way and based on two 5" ish woofers per side. I'm guessing they were custom manufactured by b&w to perform optimally in this position. I'd love to build another set but with diy-sourceable drivers, so something like 5-6.5".

Are there any particular parameters I should be looking for for good bass performance? Other than extended low fr and a low res freq of course... the main thing that strikes me about the b&w's is the tightness and accuracy if the bass, though I should mention I've moved them into sealed cabinets
 
6.5" .. look over the $63 Anarchy woofer Anarchy Woofer DIY Sound Group
"The 6.5" Anarchy woofer not only works as a woofer or midwoofer, but also as a subwoofer with it's massive 25mm peak-peak xmax"
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You state that one of your goals is strong bass performance..... Let's say you are willing to move from your 6.5" to 8" woofers. With bass, 1.5" changes EVERYTHING.

You can't go wrong by cloning the 3-way Sony Flagship Speaker... Sony SS-AR1
Dimensions: 42.5" (1080mm) H by 12.4" (320mm) W by 19.25" (490mm) D. Weight: 125 lbs (57kg).

"A corporation like Sony has resources that no small company can muster, and Yoshiyuki Kaku, the designer of the AR1, was given an extraordinary opportunity to spend many years studying the most refined aspects of speaker sound. The AR1 is the flagship of a line that will bring the benefits of all this research to lower-priced speakers as well. A medium-sized, three-way floorstander with two 8" woofers, a 5" midrange, and a 1" dome tweeter, it looks fairly conventional, though the elegance of the craftsmanship is immediately apparent, as is the distinctive shape of its enclosure. But there is much about the AR1 that is anything but business-as-usual in speaker design. And the sonic results are truly extraordinary." Sony SS-AR1 Loudspeaker (TAS 214) | The Absolute Sound

Sony uses premium cost ScanSpeak Drivers: xover 400Hz and 4000Hz
Tweeter = 1" dome D3004/660000 with Tymphany’s unique AirCirc Magnet System
Midbass = 15W/4531G00 slit paper cone
Woofer = Scan-speak 22W/8857T-00 aluminum cone

One popular SBacoustic/Satori middle cost alternative. Xover 100Hz and 1800Hz
1" dome tweeter: SB29RNDC-C000-4 $50-$60
5.5" midbass = Satori MW16P-4 $170 - $180
8" woofer = SB23NRXS45-8 $90-$100 F3 from 28-33Hz based upon ported box volume
 

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A search for "Anarchy" will provide several interesting discussions and designs.

A TM-WWW using a real midrange, and only using the Anarchy as the woofers models well. MTM- WWW using JUST the Anarchy for both M and W does not model well. MTM Lobing problems, and there are better true midrange speakers than the Anarchy.
 

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Hi guys, thanks for all the responses, that anarchy woofer sure has potential.

K think my original question must have been badly put though, what I mean was was particular properties of a driver should I be looking for when choosing a woofer for a 3-way, and why?
 
Harmonic distortion and cone resonance certainly play a role. Besides a better transient response from a sealed box, much of the perceived tightness and bass speed has to do with the FR. Speed and tightness reside in the higher frequencies and harmonics of the bass so that avoiding a vented alignment that results in an elevated LF response when combined with room gain is going to help immensely in this regard.

LineSource, how would you wire up 3 of them? 3 x 4ohm in series? Doesn't really give you any increase in sensitivity over a single driver does it?
 
Well my current plan is to use my existing 4 sb15nrxc 8ohm woofers, but I wanted to check if there were any particular parameters I should be looking for. At the moment they're in the bass end of my 2-ways in a simple TW set up, but sounding phenomenal - very extended in the low end, and crossing LR4 allows me to easily build in about 4db of baffle step
 
nannoo,

Attached simulation shows TWO SB15NRX in:
BLUE sealed F3 ~86Hz NOTE: Normal SB15NRX usage as a midbass in a 3-way
YELLOW ported F3 ~46Hz
PINK sealed with a 30Hz Linkwitz transform equalization(very high power >10x watts)

Low A on a piano is 27.5Hz
Low E on a Bass guitar is 40Hz
That's why Sony SS-AR1 uses two 8" Scan Speak Woofers which produce F3 ~24-28Hz.
TWO 8" SB23NRXS45-8 can deliver F3 ~28Hz ..... deep bass
http://www.diyaudio.com/forums/multi-way/212738-sb-acoustics-3-ways.html

Good Woofers have: large cone area; low Fs in 2x Hz; Qts 0.37-0.44; Qms >5; large Xmax >8mm; modest Le; modest Mms
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"LineSource, how would you wire up 3 of them? 3 x 4ohm in series? Doesn't really give you any increase in sensitivity over a single driver does it? "
For Anarchy woofers in a narrow line array I would probably look at two options:

1) use 3 of the Re = 6.2 ohm in parallel for a 2.13-ohm Re load plus about 0.3 ohm inductor resistance with a ROBUST amplifier. ~92db/w

2) use 4 of the Re = 3.8-ohm (connect two in parallel for 1.9 ohms) then (connect these two pairs in series for 3.8 ohms). Use the inductor resistance to match the resistor padded 3.2 ohm SB15NRX and 3.4 ohm SB29RNDC. A Re ~ 4 ohm speaker ~93db/w TM - WWWW
 

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In my opinion the quality of a speaker is based on its midrange performance and its tweeter integration. Bass is not so important for me and I supsect many people that think otherwise.

I think if you want to cover from 200-500Hz to 5Kz range well you shoudl use a driver with a maximum size of 4", otherwise why not go 2 way.

The Scan-Speak 10F/8424G00 seems very tempting to me. It also comes in 4Ohm.

The SB acoustics SB12MNRX25-4 also looks tempting, but seems to only be available in 4 Ohms.

Also have a look at full range drivers :)
 
Simple XDir Simulations to Show TM Spacing Sensitivity for Beaming and Lobing.

Wide bandwidth midbass speakers like the 5.5" Satori are gaining admiration thanks to new dome tweeters with NdFeb motors and new dome shapes which allow Fs~520Hz and Xmax~0.5mm. Top diyDesigners are using 1800Hz Xovers. Audio Democracy --- Everyone can vote with their ears.
 

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yeah, this is definately one of 'those design decisions' we have to make - there's going to be a compromise somewhere. Do we deliver the 'critical' frequencies (for me I regard that as about 260Hz to 2kHz) from a single driver or do we crossover in this region? If we avoid it we can expect greatly improved sound in some respects, but with the compromise of lobing, if we crossover in that range we have to take great care to maintain integrity.... for me, i feel the benefits of crossing over slightly higher out-weigh the negatives.

Thas said I've just unplugged the three-ways and switched back to my 2-ways, as I prefer the sound... read of that what you will!

(probably helps that my 2-ways are now crossed 4th order with BSC and phase alignment taken care of - sounding much much more natural as a result, though a bit bright, I really need to re-measure the FR and make sure my tweeter level is right!
 
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