New speaker design by NOOB

[AdamFrandsen]

Hi,

I have done the following calculations and selections, and now I need help correcting any errors and would also appreciate any other inputs. If someone could also help make a pcb/schematic of the crossover, pads and BSC it would be amazing. I tried using easyEDA, but I cannot get the nets to connect properly and am really not sure I am doing it right. Thanks in advance:

Speaker build:



4-way speaker build:



**Bass Driver: Scanspeak 32w/4878t00**

- Frequency Range: 20 - 225Hz

- Power: 200W RMS, 550W long-term

- Sensitivity: 90dB

- Nominal Impedance: 4 Ohm

- Impedance at 225Hz: 4.5 Ohm

- Diameter: 320mm

- Depth: 151mm

- Resonance Frequency: 18Hz

- Vas: 203.9 l

- Qms: 7

- Qes: 0.33

- Qts: 0.32

- Price: 630 euro



**Mid Woofer: Scanspeak 18w/4531g00**

- Frequency Range: 225 - 1100Hz

- Power: 70W RMS, 110W long-term

- Sensitivity: 90dB

- Nominal Impedance: 4 Ohm

- Impedance at 225Hz: 4.5 Ohm

- Impedance at 1100Hz: 6 Ohm

- Diameter: 182.2mm

- Depth: 78mm

- Resonance Frequency: 33Hz

- Vas: 41.9 l

- Qms: 5.2

- Qes: 0.38

- Qts: 0.35

- Price: 200 euro



**Mid Tweeter: Scanspeak d3004/662000**

- Frequency Range: 1100 - 7500Hz

- Power: 90W RMS, 150W long-term

- Sensitivity: 91.5dB

- Nominal Impedance: 4 Ohm

- Impedance at 1100Hz: 4.5 Ohm

- Impedance at 7500Hz: 4.5 Ohm

- Diameter: 104.25mm

- Depth: 29mm

- Resonance Frequency: 500Hz

- Vas: 0.02 l

- Qms: 3.79

- Qes: 0.62

- Qts: 0.54

- Price: 240 euro



**Tweeter: Scanspeak d2104/712000**

- Frequency Range: 7500 - 40000Hz

- Power: 50W RMS, 120W long-term

- Sensitivity: 92dB

- Nominal Impedance: 4 Ohm

- Impedance at 7500Hz: 3 Ohm

- Impedance at 40000Hz: 5 Ohm

- Diameter: 92mm

- Depth: 33mm

- Resonance Frequency: 500Hz

- Vas: 0.01 l

- Qms: 2.3

- Qes: 0.48

- Qts: 0.40

- Price: 220 euro



These are the driver specifications with the correct crossover points. All drivers are of the Scanspeak brand and all have a nominal impedance of 4 Ohm, with specific values at crossover points as listed. Their respective power ratings, sensitivities, diameters, depths, resonance frequencies, Vas, Qms, Qes, and Qts values are also provided.



Dimensions of the speaker cabinet:



**Main Cabinet Size:**

- Total Height: 187 cm

- Width: 35 cm

- Depth: 38 cm

- Thickness of MDF: 24 mm



**Driver Placement Spacing:**

- Bass Driver: 31.25 cm from bottom of the cabinet (center of driver)

- Mid-Woofer: 87.25 cm from bottom of the cabinet (center of driver)

- Mid-Tweeter: 142.5 cm from bottom of the cabinet (center of driver)

- Tweeter: 167 cm from bottom of the cabinet (center of driver)



**Inner Compartments:**

- Bass and Mid-Woofer Compartment: starts from the bottom to 125 cm height. The volume of this compartment is approximately 137 liters.

- Mid-Tweeter and Tweeter Compartment: starts from 125 cm to the top (187 cm). The volume of this compartment is approximately 27 liters.



**Port Specifications:**

- The port is placed in the Bass and Mid-Woofer compartment.

- Diameter: 7.62 cm

- Length: 38.9 cm



The port should be placed on the rear panel of the Bass and Mid-Woofer compartment, ensuring that there's sufficient clearance from the edges of the cabinet and the internal components.



**Summary:**

The main cabinet's outer dimensions are 187 cm x 35 cm x 38 cm, built from 24 mm thick MDF. The total internal volume is approximately 164 liters, divided into two compartments: one for the bass and mid-woofer drivers with an approximate volume of 137 liters and another for the mid-tweeter and tweeter with an approximate volume of 27 liters. The port is in the bass and mid-woofer compartment with a length of 38.9 cm and a diameter of 7.62 cm.



**Crossover Network:**



*4-way 2nd Order Linkwitz-Riley design (with crossover frequencies at 225Hz, 1100Hz, and 7500Hz)*



For the Bass to Mid-Woofer Crossover (225Hz):

- Series Capacitor: 176.37uF (100V, 200W)

- Shunt Inductor: 7.06mH (200W)



For the Mid-Woofer to Mid-Tweeter Crossover (1100Hz):

- Series Inductor: 1.36mH (70W)

- Shunt Capacitor: 8.87uF (100V, 70W)



For the Mid-Tweeter to Tweeter Crossover (7500Hz):

- Series Capacitor: 1.06uF (100V, 90W)

- Shunt Inductor: 0.23mH (90W)



**L-Pad Attenuator:**



- For the Mid-Tweeter:

- Series resistor: 0.64 Ohm (90W)

- Parallel resistor: 19.5 Ohm (90W)



- For the Tweeter:

- Series resistor: 1.08 Ohm (50W)

- Parallel resistor: 13.7 Ohm (50W)



**Baffle Step Compensation (BSC) Circuit (6dB):** (Not sure if I will use)



- For the Bass Driver:

- Series Inductor: 1.39mH (200W)

- Parallel resistor: 6.73 Ohm (200W)

• For a 176.37uF capacitor, I might use a 100uF and 68uF capacitor in parallel, and add an 8.2uF and 470nF capacitors, to get approximately 176.67uF.
• For a 7.06mH inductor, I could use a 4.7mH inductor in series with a 2.2mH and 0.15mH inductors to get approximately 7.05mH.

Rough schematic:

AMP/IN --[C4=12.9μF]-- --[L4=1.68mH]-- || --[R1t=1.2Ω]-- --[R2t=7.1Ω]-- Tweeter
|
|
--[L3=0.47mH]-- --[C3=22.7μF]-- || --[R1m=1.8Ω]-- --[R2m=6.5Ω]-- Mid-Tweeter
|
|
--[L2=0.61mH]-- --[C2=118μF]-- -- Mid-Woofer
|
|
--[L1=1.47mH]-- -- --[R1b=0.9Ω]-- --[R2b=7.5Ω]-- Bass Driver
|
|
Grnd-------------------------------------- Ground (Common Ground)

 

[fluid]

The list of information you have above is not how to design a speaker. Choosing crossover points in advance and making them fit purely electrical slopes will not work out in reality. Making a box of those dimensions sounds like it was made to hit a target volume rather than thinking about how that box will behave or even how you will build something of that size. Two tweeters and a mid woofer is going to give you rough directivity.

Here is an example of how to use that 32W in a very well thought out design.
https://pkaudio.webnode.cz/ellips-a/

Diyaudio thread
https://www.diyaudio.com/community/threads/new-project-bliesma-t34b-in-wg-18we-32w.365836/

Passive version
https://www.diyaudio.com/community/...me-with-pasive-crossover.400971/#post-7396226

Troels Graveson's site has a lot of information that is useful for DIY speaker builders, there is no real need for a PCB point to point wiring and tag strips is fine, layout of the passive components is much more important.

http://www.troelsgravesen.dk/crossovers.htm

http://www.troelsgravesen.dk/tips.h...avesen.dk/tips.htm#CONSTRUCTION_OF_CROSSOVERS

 

[D!sco]

This isn’t much fun. I really don’t like doing work for people, and you have left out even the abstract notion. Why? What is this for and what does it do? Because a four way first design will be awful, and passive no less. I do not recommend spending money on this. A ground-up approach will yield more desirable results.

 

[voodooless]

1260 euros only on drivers for a single speaker is just madness! You can make a much better speaker for far less money.

Speaker design is not solved by throwing money at the problem but by solid engineering!

Two tweeters are never a good idea. In a 4-way you’d use a small midrange and tweeter. Also, the mounting points are way too high unless you want to listen to the speakers standing up all the time? Driver-to-driver distances are also way too large. You want the driver to be close together, especially the higher frequency ones.

The speaker is massive! Building with MDF is not ideal, better use plywood.

Calculating a crossover is mostly futile. It’s not going to work. You’ll need measurement equipment to verify the results: a decent microphone as a minimum, preferably an impedance measurement jig as well. Then you’ll need a shitload of passive components to mix and match your filters to perfection based on measurements and listening.

Why passive in 2023? Looking at this design you are probably the type that would waste another few hundred euros on passive components, so why not spend them on an active DSP system? It would make tuning the crossover much simpler and will give a lot more flexibility in choosing components. The end result will be better as well.

If this is your first attempt at a DIY speaker, be prepared to fail badly. Limiting that chance can be done by first building a proven DIY kit. There are plenty of good (and bad) kits out there for any budget.