# New build using SB acoustics drivers



## EG92B16A

Hi All,

I'm wanting to build a new set of front tower speakers using SB Acoustics drivers.
Reasons why: They are readily available in OZ, great value for money, and have good specs.

I've looked and there doesn't seem to be any designs for WWMTM using above brand.
What I was proposing is something like Joe Rasmussens Elsinore's, but using SB17MFC35-8 x 4 and SB29RDC,
or Jim Holtz's Statements but using 2 x SB23NRXS45-8, 2 x SB15NRXC35-8, and SB29RDC.

Has anyone out there had any success with SB drivers and larger builds?



cheers. :help:


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## EG92B16A

*Re: Help with new build using SB acoustics drivers*

Would there be any advantages in doing a 2.5 way with 4 of the same drivers, or should I just go for a 3 way setup? I'm trying to get around the baffle step issue by using multiple drivers, and crossing over in the baffle step region to take advantage of the natural roll off.

Considering I already have an SB Acoustics SB34 subwoofer that will have an amplifier upgrade soon, I don't really need that much bass extension out of the tower design, it just has to integrate. Who am I kidding, I do like well defined bass.

I've read that the 5" SB drivers have better distortion figures than the 6.5" drivers. Can forum members confirm this, as my choice of driver will depend on the outcome. As I will be using multiple drivers, the low end figures won't be as significant as with a single driver system?


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## EG92B16A

Hi All,

I've decided on the SB15NRXC30-8, and SB29RDC drivers for my build.
Nominal box size of 40L tuned to 42Hz, giving F3=52Hz and F3/Fb=1.24
I'll be using 4 of the SB15 drivers in series/parallel arrangement. 
Two will be used up to approx. 2.2Khz as MTM with tweeter and other two
rolled off in the baffle step region for lower end reinforcement.
I'm in the process of using SPL trace with the published specs so I can get a start
with the response modeller and baffle design.

Does anyone have any opinions about the above? Should I be using the SB17's instead?


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## EG92B16A

Hi All,

I have done a bit of mucking around on the weekend plotting the frd and zma files from published data.
Put that data through response modeller and baffle diffraction simulator to get the box diffraction responses, then put that data into PCD to start modelling some crossovers.
Attached are some preliminary responses. I've gone for a cascaded parallel 2.5 way crossover design with very few components. Tweeter is 12dB/octave with just a padding resistor, woofers are essentially 6dB/octave with quasi zobels to roll off at 12dB/octave.
Next task is to purchase the drivers so I can get some real data.


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## EG92B16A

I have a question about the above phase plot.
Is there any way I can reduce the phase angle at 100Hz, or is it always going to be an inherent issue due to the box resonances? Will damping material change the outcome?


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## EG92B16A

Hi everyone,

I have now purchased the drivers. 8 x SB15NRXC30-8-UC and 2 x SB29RNDC-C004.
Tried using speaker workshop to measure the TS parameters and got some wacky numbers.
Tried using limp to measure the TS parameters and got some wacky numbers.
Managed to get some impedance data so I could at least measure the Fs of each driver. Massive variation.
Will post the data later.


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## EG92B16A

OK,

I have the preliminary data. This is after burning in the drivers for 24 hours at 35Hz and 4mm excursion.
1. 61Hz, 2. 52Hz, 3. 56Hz, 4. 61Hz, 5. 49Hz, 6. 61Hz, 7. 52Hz, 8. 62Hz
As you can all see, the data is far from the published spec of 38Hz.

I have also attached a pic of the in box data using all four sb15 drivers + tweeter. Mic at 1m and in direct line with the tweeter.
I may be able to get away with a 2.5k crossover point to the tweeter and roll the .5 woofers off at 500Hz with a shallow slope.
I'm not sure what the 6K dip is, but it's more than likely my measuring environment. (My shed).
Now back to more measurements.


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## EG92B16A

Hi all,

after some box building and more measuring, I have some up with the following results.
The box still needs some finishing touches but you can see where I'm going.
Crossover has been designed on acoustic response in my shed and only has 9 components so far.
I had to parallel the 0.5 woofers to get the low end looking like it is now. It didn't affect the impedance that much, still above 5 ohms for most of the frequency range and the acoustic phase looks good too.
Cheers


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## EG92B16A

Hi All,

Assembled one of the crossovers this afternoon. I'm using Jantzen cross caps, standard Z caps, Jantzen P core and air coils, and MOX resistors.
Was just preforming some more testing and my sound card died. (Low profile Sound Blaster Audigy 2).
Now trying to work out what to replace it with.

Any suggestions? I've been looking at another Sound Blaster Audigy 2, Asus Xonar D1, or Sound blaster X-Fi Elite Pro.


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## Mike Edwards

you did a good job on the finish of the speaker cabinets. I'm not familiar with the drivers you're using so I can't be much help there, but so far they look pretty decent


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## EG92B16A

I've been doing some more testing over the weekend.
Couldn't get the crossover working properly with the 0.5 woofers in parallel and the mid woofers in series.
Had to run the 0.5 woofers in series and sacrificed a little in the bottom end.
I've attached a few pics.


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## EG92B16A

The above plots were taken in room using holm impulse.

I have now assembled the crossovers. Components are as follows:
0.5 woofers - 7.1mH 15AG Jantzen Pcore coil. (further testing required for quasi zobel of 18uF and 2.2ohm).
mid woofers - 1.2mH Jantzen Pcore coil with quazi zobel using 12.7uF Jantzen cross cap and 2.2 ohm 10W resistor.
tweeter - 6.8uF Jantzen superior Z cap, 3.3 ohm 10W Superes resistor, 0.37mH Jantzen air coil.
Notch filter - 0.56mH Pcore coil, 2 x 10 ohm 10W metal oxide resistors in parallel, 68uF cross cap.

I'll post a pic of the crossover when I get my camera working.


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## EG92B16A

I now have my camera working so here's the pic of the crossover network.
The components are mounted on 10mm pine and glued in place.

I thought I'd go over the box construction as I've already posted a pic and not gone into any detail.
I'd made these boxes for a previous project and they worked out pretty much perfect volume wise for the SB Acoustics drivers. The main box is made of 18mm marine ply, the rear panel is made of 36mm marine ply, the front is made of 25mm mdf. The 16mm mdf driver panel has been laminated to the 25mm mdf. I did something a little different with the sides and top, I laminated on some 10mm wooden floor boards for a textured effect. It looked good but greatly improved the rigidity and weight. The inside walls are completely lined with carpet underlay and internal bracing has been used to help stop standing waves in the box. I'm not sure how heavy each box weighs, but with drivers and crossover installed, I can barely lift one.


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## EG92B16A

I have pretty much finished the speakers now. The final dimensions of the boxes are 124cm x 24cm x 26cm. Internal volume of approx 50L. 
I've attached a pic of the lining of the inside of the box, and of the finished product.
Listening to them for a bit this afternoon and I'm gobsmacked at the clarity and punch from these small drivers.
I've heard nuances in music tracks that I haven't heard before or not noticed. Wow.


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## Mike Edwards

very nice, glad you were able to get the performance you wanted out of the. the finish looks real classy with the mix of black and pure white


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## EG92B16A

Thanks for the kind words Mike.

Now for some serious listening.:T


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## fusseli

Nice build! Looks like it was a bit of extra work using drivers that happened to vary from manufacturer spec by a surprising margin. How much did that effect your box plans?


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## EG92B16A

As it turned out, the boxes that I already had ended up being about the right size. 
Paper spec drivers - 39L box tuned to 45Hz, -3dB 51.2Hz
My drivers - 48L box tuned to 47Hz, -3dB 42.3Hz

There's a couple of issues: 
1. the group delay is 19.3ms at Fs, where the printed spec would have been 10.5ms at Fs. 
2. shape of response. Can't get that nice slope to allow for room interaction.
3. cone excursion response is slightly worse below Fs, but they'll handle more power above Fs, 90W vs 70W for paper spec drivers.

I've attached the screen snapshot from winisd. The yellow plot is my drivers.

I was listening to Adele 21 and Karise Eden (The Voice Australia winner last year) last night. The speakers are quite punchy down low, mid range voice reproduction is excellent and treble is super smooth. Stereo imaging is superb, you'd swear I had the centre channel turned on.


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## EG92B16A

After listening to these speakers for about 50 hours now, I'm ready to start a little tweaking. My first tweak will be to do a few listening tests without the notch filter installed. I believe that an improvement in sound is possible if I remove the large poly cap from the signal line. T's and S's and the Shhh sound should be improved.
I can always move the speakers slightly off axis to tone down the 1khz region anyway.

cheers.


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## EG92B16A

I've removed the LCR trap from the signal path. The sound is so much cleaner and more detailed. I can listen to these for hours. I've even tried them just as a stereo pair without the sub, and I must say that for general listening there's no need for it. Only if I want bass below 40Hz I turn on the sub. HT benefits from the sub for maximum impact, but this project has surprised me. The SB Acoustics drivers are top notch for the price.:bigsmile:

Jason


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## fusseli

Tweaking and fine tuning can be the most tedious part of making a speaker, but it's definitely necessary. Good luck and glad to hear it's working out!


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