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Old 16th May 2012, 07:24 AM   #1
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Default SB Acoustics 3 ways

Hello!

I bought about a year and a half ago some SB Acoustics drivers. I haven't found the time to build the speakers untill now. But I managed to get a 1 week vacation, got my best friend to help me build them (I have 2 left hands) and started to work.

The speakers are:

2 x SB Acoustics :: SB29RDC-C000-4
2 x SB Acoustics :: 6" SB17NRXC35-4
4 x SB Acoustics :: 8'' SB23NRXS45-8

I have simulated the speaker using Boxsim and both the manufacturer's FR graphs and the graphs form Zaph|Audio
Results:

Frequency Response:
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Phase:
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Directivity:
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The crossover:
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I considered they are looking good, so I started to build the enclosures:

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And the crossovers:

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Last edited by cosmindaniel12; 25th June 2014 at 10:41 AM.
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Old 16th May 2012, 08:34 AM   #2
_henry_ is offline _henry_  Australia
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hi,

ive tried simulated the volume for sb23, i found out that the best encl is within 60-70L each, from the look of your cabs, im guessing its about 60-80L??

how is the sound ? im kinda interested to use them, as they are well price and available at my place.

cheers
henry
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Old 16th May 2012, 09:15 AM   #3
jernejc is offline jernejc  Slovenia
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Pair of those 8" in 60-70 lit closed box is one of my greatest experiences. Well braced box, rock wool filled evenly all volume...stunning bass.
Cheers, Jernej
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Old 16th May 2012, 01:26 PM   #4
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Quote:
Originally Posted by _henry_ View Post
hi,

ive tried simulated the volume for sb23, i found out that the best encl is within 60-70L each, from the look of your cabs, im guessing its about 60-80L??

how is the sound ? im kinda interested to use them, as they are well price and available at my place.

cheers
henry
Yes, 70 L (best) gives F3=32Hz. OP has it around 50/60Hz.
cosmindaniel12, did you use the drivers phase output in your frd/zma's data for Boxsim? Are you doing the finishings in your speakers? Nice build.
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Old 16th May 2012, 06:47 PM   #5
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Henry - the enclosure is vented, around 70-75 liters, tuned at 30 Hz via a 105 mm tube, 30 cm long, in . The bass is pretty close to a sealed box, short and dry, not boomy. If I will change my mind, I can always seal them. But I like them like this!

Inductor - I did use the phase output. I will paint them.

Today was a rainy day, and that stopped me from working as much as I wanted on them. Tommorow we'll prepare them for painting. Progress so far:

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Old 17th May 2012, 09:35 AM   #6
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Itís going to be nice build .I'd like to point at one detail. You have chosen the mid-woofer for midrange duties. Under acoustic load at high frequencies , plus your 350Hz high pass filter the maximal peak-to-peak excursion will not exceed 2mm for 60W power.
So the remaining 9mm of coil will work like ballast. From other viewpoint we can say that the speaker has low BL/Sd ratio. From here goes worse dynamics in midrange region and not very articulated vocals. Nothing wrong , just think about it.
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Old 17th May 2012, 07:11 PM   #7
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Moon Track: I am aware of the mentioned limitations. Using a midwoofer as a midrange driver isn't that uncommon. I think this driver (the SB17) has one of the best midranges around it's price.
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Old 17th May 2012, 10:49 PM   #8
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Hello Daniel.
I just can say from my experience. If we will take speakerís force factor BL deleted by Sd(in cm2), speakers with result 0.03-0.06 do not inspire me by their dynamics and resolution in midrange region. And I absolutely adore those speakers with coefficient 0.1 and higher. It is all for speakers separated from twitter at 3.5-5kHz.

Itís early to call it limitation without serious math.
You have pretty low crossover point between midrange and twitter.
The low pass filter itself limits too dynamical peaks , most dynamics will be reproduced by twitter and possible you couldnít notice a difference.
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Old 17th May 2012, 11:16 PM   #9
Hentai is offline Hentai  Romania
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Looking great, good job. Indeed a more suitable midrange could've made job on xover easier but if you like it, enjoy it.
I like the inclination, does it achieve temporal alignment?
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Old 17th May 2012, 11:43 PM   #10
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Quote:
Originally Posted by Hentai View Post
... does it achieve temporal alignment?
If you referring to the vertical position (x, y, z) in space relative between drivers (coils or frames) and baffle, yes, the Boxsim software has that possibility for data input and it should reflect on the phase/output time alignment, if correct. OP must be aware of it, as he might answer you soon.
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