SB17CAC35-8 and SB26ADC-C000-4 two way project

Hi everyone,

I'm planning to build a set of bookshelf speakers using the SB17CAC35-8 midrange driver and the SB26ADC-C000-4 tweeter (+wave guide), cross at ~1300 Hz. My goal is to build speakers that sound clear and crisp in the mid/high-frequency ranges for casual acoustic music listening in a medium/small-sized room. This time, I've decided to invest more time and effort into planning and building the right enclosures. The speakers will be connected to a Topping PA5 II plus 4Ω amplifier.
I have a few questions that I hope you can help me with:
  • I used WinISD to simulate the box volume and tuning frequency. Can you please take a look at the attached screenshots and let me know if there are any issues with the box design?
  • Do the cutoff and tuning frequencies make sense for a pair of speakers?
  • Do I still have some low frequency to enjoy?
I'm planning to tune the box to 60Hz with a volume of 15 liters and a high-pass filter cutoff frequency of 80Hz.

I will keep updating this thread

Thank you for your help!
 

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The link to the Troels Gravesen design has a lot of background info.

Maybe 1.3KHz for the tweeter in a waveguide is pushing the tweeter a bit much.
Hard to tell as I haven't seen any supporting measurements, possibly a slightly higher frequency may be less stressing for the tweeter and give you a lower distortion content.
All this is linked on how loud you want to play the speakers.
 
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Hi everyone,

I'm planning to build a set of bookshelf speakers using the SB17CAC35-8 midrange driver and the SB26ADC-C000-4 tweeter (+wave guide), cross at ~1300 Hz.

I doubt you will need to xo that low, as Nisbeth points out. But you can figure that out later when you take measurements, it doesn't really affect the box design and tuning at this point, unless you are trying to figure out center-to-center spacing of the drivers before you start.



I'm planning to tune the box to 60Hz with a volume of 15 liters and a high-pass filter cutoff frequency of 80Hz.

Why? Do you have a subwoofer?
If you are not going to have a subwoofer, the SB17CAC can produce plenty of low bass but you are not taking advantage of that. In 20 Liters you can get an F3 of 38Hz, which is more than enough for your needs.
If you are going to use a subwoofer, and you don't need the lower bass, then you should consider using the 5" SB15CAC.
 
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Do your self a favor and at least buy the speakers used in an open kit. Some are mentioned here.
When you finaly realize, building a speaker cabinet is easy, but constructing a working x-over near to impossible for you, just build the kit as planed.
Your idea of 1.3 kHz , 60 Hz tune and 80 Hz something filter, shows you are far away from an experienced speaker developer. These ideas are the sure way to an acoustic desaster. Please, accept that speaker construction from scratch is nothing you do for a first project. It is serious sience, needs a lot of knowledge, some measuring equipment and the room to measure. The x-over is the most important part of a speaker and the best chassis do not work without a perfectly matched one.
 
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I recently completed a small 2-way speaker using very similar drivers: SB17NBAC and SB26CDC. You might find this short thread to be useful.
https://www.diyaudio.com/community/threads/tall-thin-2-way-for-workshop-pc.402268/post-7426447

With a waveguide, the SB26ADC is probably good down to 1.6k. But 1.3k is asking a lot from this driver.

If you are going to use a subwoofer, and you don't need the lower bass, then you should consider using the 5" SB15CAC.
... Or, you can stay with the SB17, but use a sealed box enclosure. It is much easier to integrate a subwoofer with a sealed box main speaker versus a vented box main speaker.

When you finaly realize, building a speaker cabinet is easy, but constructing a working x-over near to impossible for you, just build the kit as planed.
Impossible is a big word... but the point is a valid one. It seems like this is your first attempt at designing a speaker. It is very rare that someone's first design is really good. If you view speaker designing/building as a journey, and each speaker is a step along the path of improving your skills and knowledge, then welcome to a rewarding activity... this first project will be fun for you and you will learn a lot. If, however, you want to design and build one pair of speakers, and you want it to be really good, then I would suggest going with a kit.
 
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Thank you all for your feedback and links. I appreciate it!

Yes, this is my first attempt at designing a speaker from scratch. I understand your advice to use a kit, but I want to learn as much as I can from this build, even if the results are not perfect or good.

To summarize:

I will base my design on the SB Acoustics Bromo https://sbacoustics.com/product/bromo/
  • I will remodel speakers in CAD
  • Tune the enclosure to 45 Hz.
  • Crossover at 3000 Hz.
  • I will copy the crossover schematic from the Bromo and simulate it with my measured results.
  • I will build and install the crossovers, then measure the frequency response.
  • After this point I will see if I need to adjust crossovers, hope with your help
Does this make sense?
 
For casual small/medium space use, your choice of a low crossover point of the Sb26cdc supported by a waveguide is fine. The extended directivity will allow for more flexible placement options as well.

Since you are in a learning mode/phase, consider DSP for your first design. It will allow you the flexibility to understand the audible results of the choices you make much faster that wiring up passive components. Afterwards, you can take on a hybrid approach as you develop skills…..using a combination of passive components along with DSP.

The SB26ADC 4 is one of the few tweeters that can cross low and can be used with an 8” woofer IF output considerations are taken…..this means that this design would be NO HOUSE PARTY speaker as your design goal initially stated. An 8” woofer would more easily allow for deeper bass extension.
 
For casual small/medium space use, your choice of a low crossover point of the Sb26cdc supported by a waveguide is fine. The extended directivity will allow for more flexible placement options as well.

Since you are in a learning mode/phase, consider DSP for your first design. It will allow you the flexibility to understand the audible results of the choices you make much faster that wiring up passive components. Afterwards, you can take on a hybrid approach as you develop skills…..using a combination of passive components along with DSP.

The SB26ADC 4 is one of the few tweeters that can cross low and can be used with an 8” woofer IF output considerations are taken…..this means that this design would be NO HOUSE PARTY speaker as your design goal initially stated. An 8” woofer would more easily allow for deeper bass extension.
I quickly checked some options and it seems that this minidsp https://www.audiohobby.eu/en/minids...al-2x4-digital-signal-processor-balanced.html in this configuration should fit my needs. preamp - topping pa5 II plus, source as topping e50 dac.
 

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Hello all. I'm finishing up cad model of the speaker.
This is almost exact copy of Bromo Kit .

This kit also provides crossover plans. I replicated them in XSim to see the response (FRD and ZMA files are from the internet, but I will do a measurement of the drivers when the box is finished). Would you be able to take a look? I still plan to go with DSP first, but I'm curious.

Additionally, I calculated the final internal volume to be ~13.3L and double-checked the vent diameter and length in WinISD (based on the Bromo design). If I want to keep the vent round, there is hardly any space to fit it. With a 53mm diameter, I need a 305mm length to stay above 17 m/s air velocity peak. In the screenshot, the vent length (without flange) is 240mm. I can go as much as 250mm before the vent touches the tweeter. Will there be problems if I stay with a ~240mm length?
 

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