Zaph|Audio SB12.3, SB Acoustics 12", 3-Way - PAIR

Zaph|Audio SB12.3, SB Acoustics 12", 3-Way - PAIR
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Price: $1,089.00


  • Buy 10 - 10,000 and get an additional 10 % off
Manufacturer: Zaph Audio
Product ID : sb12.3
Weight: 72.00 lbs
Manufacturer: Zaph Audio
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Zaph|Audio SB12.3 ~ SB Acoustics 12", Dual Midrange, 3-Way, Parts Only
Price shown is for a PAIR

Madisound is pleased to bring you our big SB Acoustics 3-Way kit, the SB12.3. We often receive requests for large and in charge speaker systems. This kit is our hi-fidelity answer. Once again we teamed up with John Krutke of Zaph Audio for his skilled design work. This kit is fully documented on the SB12.3 page on the Zaph Audio website.

SB Acoustics drivers have quickly established themselves as serious performers within the DIY speaker building community. We feel this line of drivers is a perfect choice for a high performance 3-Way design. There is no concession in the driver selection or crossover design, yet the final price is more than reasonable for a system of this stature.

Each speaker is anchored by a 12” SB34NRX75-6 woofer for bass duty. This woofer features a stiff paper cone with 3” voice coil, an open structure cast frame, huge ventilation through the pole piece, and 11mm of X-max. The SB34NRX is a Madisound favorite and does not disappoint here in a sealed box alignment.

Critical midrange duty is carried by a pair of 5” SB15NRXC30-8 drivers. These units feature the same proprietary composition paper cone and a similar open structure cast frame. The extended length copper clad pole piece helps enable very low distortion through its frequency range. The SB15NRXC already has quite the DIY following for mid/bass duty, and we are excited to implement it as a dedicated midrange in this project.

High frequency reproduction is performed by the SB29RDC-C000-4 ring dome tweeter. This is the flagship tweeter of the SB Acoustics line and one of the best tweeters we know of. The SB29RDC features a unique fabric ring dome with large roll surround, a low resonant frequency, and a smooth extended response.

If you desire a large speaker system and demand zero compromise in sound quality, look no further - the SB12.3 is for you!


  • Frequency response: 37 Hz – 20+ kHz, Anechoic F3: 37 Hz
  • In room response even lower. This system has plenty of bottom end!
  • Recommended amplification: 50 W – 250+ W per channel
  • Crossover frequencies: 220 Hz & 2.2 kHz 
  • System sensitivity: 92 dB
  • System impedance: Minimum 4.3 ohms, Avg. 5-6ohms
  • Most amplifiers will have no problem powering these speakers
  • 46” Tall x 16” Wide x 14” Deep (see cabinet drawing)
  • 3.75 cubic foot sealed airspace for woofer
  • 0.58 cubic foot sealed airspace (separate from woofer) for dual midrange drivers

Each SB12.3 Kit Includes:

You may also choose to purchase the optional accessories package. The accessories package is offered at a discounted price, and will provide you with all the miscellaneous speaker building parts that you need to complete your kit.

Optional Accessories Package Includes:

All pricing includes at least a 10% discount on all drivers and parts.

Crossover Information:

Crossover parts were carefully selected for both high quality sound reproduction and adequate power handling. The series circuits feature a low DCR Sledgehammer 15 AWG Steel Laminate inductor for the woofer, Solen Fastcap & Sidewinder 16AWG Air Core inductors for the midrange, and Clarity CSA Caps for the tweeter (please note the older-style ESA caps are pictured). Mundorf MOX resistors are also used throughout the tweeter circuit and in series with the midrange. The crossovers are professionally assembled on three circuit boards. The midrange is on a Matrix Double, and the woofer and tweeter are each on a Matrix. You can bi-wire/amp or even tri-wire/amp the SB12.3 if you desire.

Crossover Upgrade Options: (as described above, but with the following changes)

  • Mundorf M-Cap Supreme caps in the tweeter circuit
  • Clarity PX Caps in the series midrange circuit
  • Clarity PX Caps in the series midrange circuit & Mundorf M-Cap Supreme caps in the tweeter circuit

Miscelaneous Notes:

Cabinets are not available for this kit through Madisound. The speakers are simply too large to make this logistically possible.  Tyler Acoustics built the walnut veneer cabinets you see here and he is willing to build this for people who are interested.  You can choose your own veneer and he will quote accordingly.  Please contact Tyler directly.

Each cabinet uses 3.5 pounds of Acousta-Stuf internal fill. Use 3 pounds in the main woofer chamber and ½  pound in the midrange chamber. You should also line the rear wall and side walls of the cabinet with acoustic foam sheets. These damping materials are included with the optional accessories package.

We recommend using the TD-CUP dual binding post input cup, and it is supplied with the optional accessories package. Run one set of wires from the bottom set of binding posts to the woofer crossover. Then run one set of wires from the top set of binding posts to the midrange crossover - and jumper a set of wires to the tweeter crossover from there. Another option is to run a TD-CUP and a standard input cup, or 3 sets of binding posts on the back of your speaker. You would then wire each crossover to its own set of binding posts.

The SB12.3 rounds out the Zaph line of Madisound kits, giving you multiple kit choices from best lines of drivers available. If this specific kit doesn’t suit your project goals, please consider the new ZA5 family of kits or an established favorite; the Seas SR71 or Scan-Speak ZRT.

SB12.3 Drivers

Professionally Assembled SB12.3 Crossovers

SB Acoustics Ring Dome Tweeter

SB Acoustics Midrange Side View

SB Acoustics Woofer Riew View

SB12.3 Tweeter Crossover Detail

SB12.3 Midrange Crossover Detail

SB12.3 Woofer Crossover Detail

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Product Reviews

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Reviewed by warlock187
warlock187 bought "Zaph|Audio SB12.3, SB Acoustics 12", 3-Way - PAIR" on our website
02/07/2017 - 06:34:18 PM
Excellent Kit - Huge, Clear, Impactful Sound from Equally Huge Cabinets!
I recently completed a build of the Zaph Audio SB 12.3 kit. For my particular needs, I altered the standard kit in a few distinct ways...

The first alteration I made was to include two 12" passive radiators (SB34NRX-00) in each cabinet, to help extend the low end even deeper. The additional radiators were placed with one on the front baffle (above the wired woofer), and one at the exact same height on the rear baffle. So each cabinet contains three 12" cones. To accommodate these additional radiators, I reworked the cabinet dimensions to be slightly larger than the original kit specs. The finished cabinet measures 15"W x 18"D x 51"H. Needless to say, the finishes speakers are pretty massive!

Another variation I did, after completing the build and doing some test listening, was to remove most of the polyfill from the bass chamber. To my ears, with much of the polyfill removed, the bass sounded more ample and full, without getting muddy at all. I believe this may be because I added the passive radiators, but I'm not certain. I am guessing if the kit was built without passive radiators (as the standard kit), you would probably want all of that polyfill included inside.

A mistake I made (in case this helps others avoid the same in the future) was that I connected the lead wires from the midrange crossover to the binding posts in reverse polarity, because the Zaph site had mentioned that circuit requiring reverse polarity. After listening, however, I could tell something was wrong, but could not identify the problem on my own. There was a distinct lack of midbass, which made the overall sound seem hollow and kind of empty within a certain frequency range. After some helpful troubleshooting assistance from Madisound, we theorized it may be a polarity issue. A recommended battery polarity test confirmed the theory. Ultimately, I had not realized that the crossover wiring diagrams provided with the kit already accounted for the reverse polarity, and did not require me to reverse the polarity at the binding posts. Thus, I had unintentionally "reversed" the already-reversed polarity. When I then switched the quick connects to normal polarity at the binding posts, the sound improvement was significant, most noticeably in a much fuller midrange/midbass.

Building the cabinets for this beast was no small task. I had a local lumber house do all of the raw milling, as they have a computer-controlled plunge router machine, to ensure all of the cutouts would be perfect. I then assembled all of the raw pieces. The front and rear baffles are 1" MDF, with all other pieces being 3/4". Needless to say, these suckers are heavy, but I feel their large stature is well worth it. Even when played at a crazy volume, there are only negligible vibrations on the exterior. The weight and thickness of the cabinet really stands up to some huge bass. Also, with the increased cabinet size, the inner volume is even larger than that of the standard kit, for even deeper potential low end frequency response. Whenever someone comes into the listening room, they typically have a comment about the giant speakers!

Since now being broken in, at least to my ears, these things have massive sound, that remains distortion-free and full of immense clarity, even when driven to frightening levels. I am driving them with an Anthem i225 integrated amp, which provides more than enough power to get these things cranking. If anything, I wish my listening room was even larger, to be able to crank them up even louder without putting my hearing in jeopardy.

All in all, this was a really fun project. My preliminary critical listening, and all third-party listening feedback thus far, has garnered rave reviews! I would certainly recommend this kit to anyone else looking for a set that can produce absolutely huge sound that remains clear and detailed, up to levels beyond what your ears can safely handle. Kudos to Zaph for an overall superbly-designed system, and many thanks to Madisound for providing excellent service and support when I needed it throughout the entire building process.
Reviewed by steakisbetter
12/21/2016 - 06:56:26 PM
Nothing these can't do!
I've owned these for many years now and they continue to impress me! One of my first builds because of the insane value here and still one of my favorites. These started out as the mains in my living room and ran them hard using my CJ 2250 without ANY problem. They would play lighter tracks like "Night Train" by Amos Lee with great detail and then turn around and slap you in the face with RHCP's "Slow Cheetah"! These were the mainstay as my mains until I had kids, worried about them playing around them and the weight. So they were put in the basement and sadly used less over the past few years.

This summer my cousin asked me to do the music for his wedding, these came to mind right away! The room was a converted barn with huge barn doors that would be open and high cathedral ceilings. I was a little worried about the room size and set up to be honest. I brought an extra powered sub and a set of smaller speakers to pick up any lost highs. WOW, I didn't need any of it. Had these set up in the corner and they really filled that space with clear, loud music all night long! Used the same CJ amp with them and I had no less than 10 people come up to me and ask about the speakers!

A great buy without any fear of regret! Very fun to rediscover these.
Reviewed by
03/21/2014 - 05:20:28 PM
SB12.3 is excelent speaker. This was the first speaker i ever built myself and later i also built SR71 and other kits of famous authors. Believe it or not - after spending years building some top $ projects availible - these speakers are still one of the best i had and my presonal favorites.
What makes it special:
1. Outstanding bass driver which will dig down to 20Hz easily with right amplifier offering one of the best and deepest bass which is tight and accurate. Some say closed box can't do deep bass - i built some ported, quarter wave (DTQWT) and some exotic bass enclosures - when built right these will eat most of them for breakfast. With digital class D amp easily pick down to 20Hz+ causing small armageddon in the house.
2. It's large baffle along with MTM confuguration throw gigantic and deep soundstage.
3. It is very detailed and fast, with sparkling yet delicate highs.
Recomendations: do NOT save on tweeter crossover components, the cheaper you do with crossover the brighter and more sibilant it may get because tweeter is very fast so you'll hear every bit of distortion and noise. Cheap caps kill it's sound because there's 2 in signal path.
Adding variovents to cabinets will allow for even deeper bass and make it more "open and free". And it's probably the only speaker for rock music fans