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Multi-Way Conventional loudspeakers with crossovers

Thoughts on the SB Acoustic SB12PAC25 and ideal tweeter and box?
Thoughts on the SB Acoustic SB12PAC25 and ideal tweeter and box?
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Old 15th October 2017, 08:09 AM   #1
JonesySA is offline JonesySA  Australia
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Default Thoughts on the SB Acoustic SB12PAC25 and ideal tweeter and box?

Hi guys

I have been offered a couple of SB12PAC25 drivers:
4" SB12PAC25-4 :: SB Acoustics

I would like to use them with a reasonably priced tweeter in a 2-way. I haven't come across much info on these drivers. Thoughts?
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Old 15th October 2017, 10:57 AM   #2
HorvathS is offline HorvathS  Hungary
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Hi,

There is a kit here:
SB Acoustics :: Micro Kit

The SB19ST tweeter is cheap and good.
Crossover should be OK - you can find it under "Schematic" link.
S
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Old 15th October 2017, 12:57 PM   #3
JonesySA is offline JonesySA  Australia
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Quote:
Originally Posted by HorvathS View Post
Hi,

There is a kit here:
SB Acoustics :: Micro Kit

The SB19ST tweeter is cheap and good.
Crossover should be OK - you can find it under "Schematic" link.
S
This is great! Thank you
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Old 15th October 2017, 05:10 PM   #4
HorvathS is offline HorvathS  Hungary
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I don't like white boxes, but this is nice.
Only the 70Hz (-3dB) should be high . . .
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File Type: jpg SBA Micro front.JPG (36.5 KB, 419 views)
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Old 15th October 2017, 11:09 PM   #5
JonesySA is offline JonesySA  Australia
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Quote:
Originally Posted by HorvathS View Post
I don't like white boxes, but this is nice.
Only the 70Hz (-3dB) should be high . . .


They would certainly benefit from a sub. They will be used on a PC. The speakers they are replacing are 6.5" drivers good for 54Hz but quite a large box. These are very compact.
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Old 16th October 2017, 01:30 AM   #6
rabbitz is online now rabbitz  Australia
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Quite a nice driver and Troels used them in a TV speaker.
myTV

I bought a pair to carve up as a small PR but were too good. I did a pair for near field use above my workbench. The box has a removable baffle so I can test small drivers. Used the NE19VTS-04 tweeter crossed over at 3800Hz. The breakup above 10kHz is better than most metal cones and the crossover drops it far enough (around 18dB) that it's not an issue, plus it's off axis listening. The NE19VTS-04 works well with them but needs really small screws which can be hard to find in black. The SB26STCN-C000-4 could be another choice as used in JB's Soprano.

The combination worked better than any FR drivers I tested with more body, slam and top end. The bottom end was enough for near field use and the small listening area.

The shallow box I used was Vb=2.6 litres, Fb=78Hz, F3=72Hz, F6=65Hz but can go up to around 4 litres for a lower F3 but xmax increases.

BTW... I didn't bother to rebate the SB12PAC as not worth the effort but the tweeter is rebated. I could have gone for tighter TM spacer but kept it wider so a larger tweeter could fit if the NE19 didn't work.
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File Type: jpg SB12PAC_NE19.jpg (173.5 KB, 400 views)
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Old 8th January 2018, 07:27 AM   #7
akarma 76 is offline akarma 76
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rabbitz

Can you publish filter scematic?

Wanna make mini 2 way speaker with subwoofer support and SB12PAC25 is a main contender for midwoofer role. Dayton RS125P-8 and HiVi B4N are other ones.
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Old 9th January 2018, 05:22 AM   #8
rabbitz is online now rabbitz  Australia
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The crossover I designed was based around the components I had in hand. I tried my usual series xo first but not suitable, so parallel it is. Sounds very good with a nice overall balance but I would say that wouldn't I.

These are used nearfield at my work bench.
Attached Images
File Type: jpg sb12pac_ne19.jpg (44.9 KB, 293 views)
File Type: jpg sb12pac_ne19_rev.jpg (45.2 KB, 289 views)
File Type: jpg sb12pac_ne19_z.jpg (34.9 KB, 282 views)
File Type: jpg sb12pac_ne19_xo.jpg (13.4 KB, 73 views)
File Type: jpg sb12pac_ne19_xo_val.jpg (14.4 KB, 70 views)
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Old 31st May 2018, 08:15 AM   #9
Gropascal is offline Gropascal  France
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Default SB micro-kit

Hi Rabbitz and Everybody,


I built a SB Acoustics micro-kit, which is close to Rabbitz design except :
* SB12PAC is BR loaded
* Tweeter is SB19ST
* Hi-Pass is 3rd-order


At first listening, these tiny speakers are impressive : very good tonal balance, a lot of details, dynamic and lively and not shouting.


The imaging (and specially depth) is just OK, not great


After listening with more attention, a flaw can appear : treble is a bit "sad", or should I say shy ? Not a tonal balance problem, which remains crispy, but lacking of engagement. Too much attenuation ?
In fact I can't find the SB19ST character mentioned in different reviews.


Analyzing SB12PAC FR, a big and wide ringing appears (7k --> 17k, up to 12dB). Even if it is attenuated by LP, I guess it can affect the LP transfer function.
Here comes the idea of adding a notch to tame the SB12 ringing.


I first try a series L + R + C, paralleled with the speaker. Values are :0.22mH + 8.2R + 1uF


Improvement is obvious : the treble is kind of "free'd", more tuneful and delicate. Now the character of SB19 appears.
Imaging improves a bit.
But no free lunch : now, it seems to appear a small "missing" between the two drivers.


Next experiment will be to increase a bit LP cut-off frequency.
Will let you know.


Has anybody (and specially Rabbitz) experienced such behavior of SB12 PAC ?


I would be happy to share informations about our experiments / solutions.


Regards


Pascal
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Old 1st June 2018, 07:59 AM   #10
rabbitz is online now rabbitz  Australia
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I didn't notice anything odd with the behaviour of the SB12PAC25-4 as it worked well straight from the design to build. Both my design and Troel's version have very simple crossovers and mine pushes the SB12PAC a bit higher so would notice any nasties in the higher frequencies if they were there. Mine uses the natural driver roll off with the filter to drop it faster to give it the final acoustic slope. This was done to have a high xo point (3800hz) to remove any stress on the tweeter as it used a 2nd order filter. I never listened to the woofer only with LP filter plus I only hear to 10kHz which may have a bearing.

For reference here is Troel's xo. http://www.troelsgravesen.dk/panason...sonic--203.jpg
The article link is in post #6 and he gave no indication of anything nasty.

You may want to check the drivers polarity as the Micro kit has them both wired +ve polarity. What you are describing sounds like a dip in the crossover area or a phase issue.... sort of a hole in the middle.

You could try Troel's woofer xo components and/or dropping the tweeter back to 2nd order (try both polarities) to get a wider overlap between the drivers.
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