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SB Acoustics monitors build

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  • djg
    So converting to US currency, quite reasonable for the finished product. Very nice results. I just want to see that blue tape gone.

    I think most people wouldn't see the value in "homemade" speakers. Your level of finish might overcome that attitude.

    Last edited by djg; 10-12-2021, 03:56 AM.

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  • DeZZar
    One other thing I can share at this point is cost.....if you're ever wondering exactly what goes into building a set like this and the cost to do a one off custom build.....well here it is.

    These are current Australian prices in AUD.

    Some things in Aus are pretty expensive - others on par. A 2x US Pint of Titebond wood glue costs me $25 for comparison.
    Description Qty Unit ($) Total ($)
    1200x1200 Sheet of 12mm MDF 1 $ 40.00 $ 40.00
    Tasmanian Oak (135x19x2400) 1 $ 50.00 $ 50.00
    Fastening & Misc (glue, nails, screws) 1 $ 10.00 $ 10.00
    Felt Padding 1 $ 10.00 $ 10.00
    Acoustic Stuffing 1 $ 10.00 $ 10.00
    2" Precision Port 2 $ 25.00 $ 50.00
    Boxes sub total $ 170.00
    Tasmanian Blackwood Veneer 2 $ 20.00 $ 40.00
    Contact adhesive 0.3 $ 26.00 $ 7.80
    Danish oil 0.25 $ 55.00 $ 13.75
    Cabothane Clear Satin (300g) 1 $ 26.00 $ 26.00
    Sandpaper & Misc 1 $ 10.00 $ 10.00
    Finishing sub total $ 97.55
    Speaker screw (allen key, cup head, M4) 16 $ 0.40 $ 6.40
    Threaded Insert (M4) 16 $ 0.40 $ 6.40
    Speaker Terminals (Gold plated, set of 2) 2 $ 16.00 $ 32.00
    Soundlink OFC Cable (13AWG) 2 $ 3.00 $ 6.00
    Hardware sub total $ 50.80
    SB Acoustics SB29RDC Tweeter 2 $ 55.00 $ 110.00
    SB Acoustics SB17NRX2C35-4 Woofer 2 $ 77.00 $ 154.00
    Shipping 1 $ 15.00 $ 15.00
    Drivers sub total $ 279.00
    5.6uf Jantzen Standard Z-Cap 2 $ 9.00 $ 18.00
    3.3uf Jantzen Standard Z-Cap 2 $ 6.50 $ 13.00
    0.56uf Jantzen Cross-Cap 2 $ 2.60 $ 5.20
    15uf Jantzen Cross-Cap 4 $ 13.50 $ 54.00
    Jantzen 1.0mh 0.30Ohm 2 $ 32.00 $ 64.00
    Jantzen 0.39mh 0.167ohm 2 $ 13.50 $ 27.00
    Jantzen 0.27mh 0.414ohm 2 $ 3.50 $ 7.00
    Jantzen 0.56mh 0.36ohm 2 $ 8.50 $ 17.00
    Jantzen 1.2mh 0.55ohm 2 $ 11.50 $ 23.00
    8.2Ohm 10W Superes Resistor 2 $ 5.00 $ 10.00
    5.6Ohm 10W Superes Resistor 4 $ 5.00 $ 20.00
    1.0Ohm 10W Superes Resistor 2 $ 5.00 $ 10.00
    Mounting Boards 4 $ 5.00 $ 20.00
    Misc Mounting Hardware, Solder, Heatshrink 1 $ 10.00 $ 10.00
    Shipping 1 $ 15.00 $ 15.00
    Crossover sub total $ 313.20
    Total Parts/Materials Cost $ 910.55

    Q: Is it cheap to make your own speakers?
    A: No

    Q: Could I make them cheaper than this?
    A: Sure - either you can find all the parts cheaper or change the finish and hardware. Or both.

    Q: Should the cost of drivers be my focus?
    A: Not really - once you consider the overall build cost - you'll wonder why you bothered only spending 30 bucks on woofers when you could have upgraded significantly and still not ended up with the drivers being the greatest cost. In this case the drivers were only 30% of the total cost.

    Q: Is it worth it?
    A: Very subjective question. I believe you would need to spend a lot more on a commercial product to equal the quality in both construction and output.

    Q: Is this what you would sell them for?
    A: Hahaha....not even close - no labour or workshop costs included above. These would have to be about $1,800 to a paying customer otherwise its just not worth it. However, you have to consider that for the the cost of a laptop you have a set of hand made speakers made from top quality parts, that sound amazing and will last 20+ years without missing a beat. My neighbour will eventually be giving these to his new born daughter for her first speakers!

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  • DeZZar
    commented on 's reply
    Thank you. I really appreciate the feedback - I know I learn something from every build so if I can share and someone else learns something too that's awesome! :D

  • a4eaudio
    commented on 's reply
    Nicely done! There has been a decrease in build threads here as people don't post a lot of detail or migrate to other websites. Your threads have been great, please keep posting your builds and all of the details, they are great resources!

  • DeZZar
    Long listening session last night and to cut to the chase - I don't think we'll change anything! No need to move to 1.1 on that first coil. As rpb mentioned above, once combined into stereo image what seemed to be a slight forwardness has gone completely.

    Covering everything from metal to rock to country to jazz to classical to pop to dance and trance.....I'm really happy with the performance from these and second guessing myself as to why I'm giving them away!!

    To use a bunch of subjective language - they have a warm rich tone with substantial depth that seems to defy their size. I have to confess that I have never really been that interested in bookshelf sized speakers for the simple reason I never found that they produced enough bass or bass depth for my liking - and although still true to an extent, in my view - these have completely shifted my mindset! The bass performance is substantial - never fat, bloated, flabby or overwhelming - just solid, punchy and full - not something where only a given note here or there make you think "oh yeah there is a bit of bass there" - nope - from the outset - even the pluck of a guitar string has that deep harmonic underpinnings that give it a full real life sound.

    Male voices, like Sully Erna's on the track 'Broken Road' come through with a full rich tone that you'd expect from much larger speakers. His loud, 'pingy', 'echoy' piano playing, often problematic on some speakers, is rendered in its true form without any lingering uncomfortable harmonics.

    Metal is what it is, you can listen to it and understand that its a bright loud amalgam of distortion, shredding and cymbal bashing without thinking "good grief, please take me back to the string quartet". The tonal balance is there without thinking the woofer dropped out.

    Stereo image is strong and precise. Michael Jacksons Stranger in Moscow renders out the beginning parts with a precise centre, left, right, centre of the punchy synth notes. His voice is clear and dead centre. The sort of mind tricks dead centre - stare at the left or right speaker and try and convince your brain the sound is coming from them - you cant do it.

    Diana Krall's Temptation is fantastic - the opening riff combination of piano and double bass might as well be in the room - and her voice is present and right in front of you - the brushes on the drums, the person slapping the tambourine - every little detail is right there as good as I've ever heard this track.

    I could go on but I'm starting to sound like I write for What Hi-Fi so I'll shut up.

    This of course is all via a crappy interface to a cheap amp through a conglomeration of nuts bolts plugs and wires for the prototype crossover using the cheapest crossover parts available. So I cant wait to see where this lands once we have higher quality parts in the final assembly. It'll be time to hook up my Rega for one final listen before I say goodbye :'(

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  • DeZZar
    commented on 's reply
    And that is exactly what's happened. Lol. Have spent some time listening to both hooked up now and I would no longer describe them as forward!

  • rpb
    commented on 's reply
    My experience is that auditioning one speaker vs two is that two will sound less forward than one.

  • DeZZar
    Originally posted by augerpro View Post
    I've read cautions about using those bypass caps on the first woofer inductor without a resistor in series. It's a short to ground via the first parallel cap and can send an amp into oscillation. I usually throw an 8 ohm resistor in series with those bypass caps.
    Thanks - I wasn't aware of that. The resistor had little effect so I figured it could be left out. I'll put something back in.

    Originally posted by augerpro View Post
    How does it sound? Tweeter better behaved? How much farther down is response at Fs of the tweeter?
    Still some more listening to do. I've only had one speaker running so far but have found enough crossover parts to get the second one up and running so I'll be doing that today and get some more listening happening tonight.

    I would say there is no longer that sort of extra treble sticking around which I'm sure was due to the flare. Otherwise all the measurements say everything is behaved now - the tweeter is well and truly down at Fs (600Hz) @ -70db.

    I'm unfortunately in a pretty noisy area on a main road so I don't really trust the distortion measurements that much (distortion and noise floor are the same! and distortion basically follows the noise floor!!!) - but, absolute levels aside, they are not showing any significant spikes etc at crossover or down near tweeter FS (0.24% THD). Actually the region 500Hz through 2K is the cleanest of the distortion results with a rise to about to about 1% over crossover that stays consistent for tweeter range.

    Tweeter by itself at these levels (~90db) is just on 1% from 3K and up (with crossover in play) (again, according to my noisy environment).

    I would describe the sound at the moment as very slightly forward in the midrange - and I think I will increase the first inductor on the woofer from 1 to 1.1 when I order the final parts.

    I'm being super critical here (as usual) and to be honest its already crossed that threshold of where you can stop listening to the speaker and start listening to music - and to me that's always the pivotal moment in custom design where you know its a success. From here you can sort end up in a song vs song tweaking never ending loop (an adjustment for one track, reduces how good another one sounds and so on).

    Neighbor was super happy two iterations ago and I can tell he just wants them handed over now! lol

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  • augerpro
    I've read cautions about using those bypass caps on the first woofer inductor without a resistor in series. It's a short to ground via the first parallel cap and can send an amp into oscillation. I usually throw an 8 ohm resistor in series with those bypass caps.

    How does it sound? Tweeter better behaved? How much farther down is response at Fs of the tweeter?

    Leave a comment:

  • rpb
    For anyone that doesn't know, those two dips near 3k are the result of the x-over, and are normal. It's due to the relative distances from the drivers to the mic changing. This is the same reverse null that occurs on axis when you swap polarity.

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  • DeZZar
    0-60 Off-Axis going Up

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    And 0-90 coming down

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  • DeZZar
    After a decent few rounds of re-modelling, re-working, measuring, rinsing and repeating I am happy to present the results on this build.

    In the end I had the best results with a fourth order electrical all round (tweeter and woofer).

    Here is the final crossover schema.
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    Yes its a fairly high parts count crossover but overall fairly simple and the smaller sized caps on the tweeter provide an opportunity to spend a little more here if so desired.

    All in all this woofer isn't the best behaved in terms of upper octave performance and I would have to admit the baffle and resultant tweeter positioning aren't optimal either - however, the point is that an older style "box speaker" design was the order of the day. Crossover lands right on 2.9K in the end which helps dramatically with off-axis performance.

    All of the following measurements were taken @2.83volt with mic @ 850mm distance on tweeter axis.
    REW was not SPL configured so SPL shown is not absolute.

    Here is the final full spectrum result:
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    Here's the result with the woofer and tweeters individual measurements and an inversion of tweeter polarity. Everything looks to be well behaved. The troublesome parts of woofer breakup have been pushed -50db down. The fourth order electrical is giving us an acoustical slope of just under 18db per octave on the woofer, and 20db on the tweeter.
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    Sanity checking the voicing here shows that on the chosen -5db gradual slope out to the top end, the performance stays well within +-2.5db from 42Hz all the way to 20K.

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    Horizontal Off-Axis performance shows that the previously encountered flare around 2-3K has been eliminated in terms of seeing a significant spike up in off axis db, although I do note that the 2-3K region stays about the same level all the way out to 45 degrees. From listening so far this certainly doesn't seem to be problematic at all and in terms of the overall off-axis performance we've got the sort of roll off you would expect all the way out to 90 degrees.
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  • DeZZar
    Definitely agree - the steeper the slope the more it becomes obvious the sound is coming from distinctly different points on the baffle, depending on the content.

    The model above I am yet to try, although 4th order electrical on the woofer, it actually only results in around 13.6db/octave over the crossover region (2-4K). On the tweeter the third order yields 11.3db over the same octave. Is this where we say "fourth order electrical, 2nd order acoustic" ? So then 3rd and 4th order electricals in this case have yielded second order slopes on both drivers.

    Keen to see how this sounds anyway!!

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  • Wolf
    I find the really steep filters like the DSP/48 really sound like one driver stops and one picks up. In shallower targets, this is not such an issue and the drivers blend really well together.
    I say- steep enough to do what is necessary for blemishes should be the MO. This does not mean you cannot experiment, but with regards to cost, lesser orders are usually less costly.


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  • Steve Lee
    "Build a Kit"

    Damn sound advice!!

    Pun intended.

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