A 2way speaker with Peerless NE180-8 and SB26CDC/ADC

[Vineethkumar01]

I am exploring a 2/2.5 way speaker design with the Peerless NE180-8 midwoofer and an SB26ADC/CDC tweeter. It started out as a 2-way speaker design for a friend. But he has moved on to other designs. So, I am considering building it anyway and experimenting with it.

There are a few 2-way designs available on the net with this woofer, like this one: https://ampslab-spk.com/2020/12/04/rosefinch/
I really like the Satori midbass driver-like looks of this midwoofer. It also has a good enough output capability for a small room and has been praised by many on DIYudio. So why not try it out.. I have high hopes for this speaker...

The 2-way speaker has the form factor of a bookshelf speaker. Later, if this turns out well, I will try out a separate 2.5-way design that uses a pair of NE180-8 per side in a tower format.

This speaker is supposed to have a passive crossover and versions with/without custom designed waveguides for the tweeter

 

[Vineethkumar01]

Before we jump into technical details, here are the approximate cost calculations for the drivers alone for a pair of these speakers

2 x NE180-8 midwoofers will cost Rs 16000/- (https://electrocarts.in/product/peerless-by-tymphany-ne180w-08-6-1-2-fiber-cone-woofer-speaker/)
2 x SB26ADC tweeters will cost Rs 10400/- (https://audiofy.in/products/sb-acou...j3HqKBqb69nBrC1ypNVyJAsrSjGfjOrPQPndDfBgiZvJN)

So, excluding any shipping charges, the drivers will cost Rs 26,400/-.
I have these drivers in hand from a few years back.

 

[Vineethkumar01]

Here is a preliminary enclosure simulation with a closed box of 13L internal volume and a series cap of 330uF with the NE180-8

 

[Vineethkumar01]

Here are the specs of a bass reflex cabinet with 15L volume for this driver




SPL curve with inductance roll of at higher frequencies modeled as per VituixCAD

 

[Vineethkumar01]

Now that we have some ideas for the woofer box alignment, it is time to focus on the tweeter and the waveguide for it.
My goal was to enable a smooth transition in directivity between the tweeter & woofer around the crossover point. It is easier to make the directivity curve very flat with this tweeter upto about 10kHz or so and thereafter it quickly rises up. But I chose not go down that path and let the tweeter directivity gently as the frequency increases. This will determine the waveguide size and the profile curve.

A friend gave me full polar measurements of the woofer in a 21cm wide box. So I had atleast some actual data to play around with the waveguide simulated polars.

Here are a few iterations of waveguides

1) The ultra flat DI version of waveguide
Cabinet is 244mm wide with 18mm roundings on sides:





A possible system polars with crossover (NE180 polars and waveguide polars combined with a hypothetical crossover)



Since I was not completely convinced with the directivity step around 1kHz and because friends over at diyaudio called my attention to it, I thought of making a differently sized waveguide

 

[Vineethkumar01]

I think I finally found something I liked


Waveguide polars


Full system Spinorama curves


Note that here the CTA curves have slopes falling in a certain recommended regions indicated by the light colored highlighting around the curves

 

[Vineethkumar01]

The actual waveguide designed in fusion





Time to get it printed and start testing...

 

[Vineethkumar01]

Did a preliminary box design as well

 

[Vineethkumar01]

Ok.. So here are some renders of a version of the cabinet I really really liked..
Inspiration from Sonus faber, JBL K2 and a whole lot of similar speakers..

It is about 33 cm wide at the widest point, 40cm in height, and about 20cm in depth at the deepest point
Cabinet volume is approx 13L





Two part baffle

 

[Vineethkumar01]

The top edge chamfered version

 

[yogibear]

Very very nice !!!

 

[Vineethkumar01]

Sadly, all beautiful looking boxes are not good for speaker cabinets,
Here is a simulation showing what a mess the step changes in cabinet profile near to baffle can do to tweeter radiation even with waveguide

 

[Vineethkumar01]

For a more acoustically optimized cabinet, I am very confident of this one

 

[diyaudio]

Vineeth, Any reason the tweeter waveguide is not same size as woofer?

 

[Vineethkumar01]

Vineeth, Any reason the tweeter waveguide is not same size as woofer?

So, with a waveguide of the same size as that of the woofer, especially constant'ish' directivity type, the DI initial climbs because of the midbass cone and size and then flattens where is joins the waveguide. There is a school of thought which says does not recommended such a directivity profile for relatively farfield listening. Here is an example from the Neumann KH120 speaker

Measurements for speaker Neumann KH 120 II

www.spinorama.org

Many speakers have this directivity step in their spinorama data.. Some of my speakers also have this kind of DI curve.

My objective was to avoid the step and let it rise as smoothly as it can. So the waveguide looses directivity at a higher frequency, the woofer starts beaming enough and the joining of these two with an in phase crossover will give a smooth DI curve.. or so is the hope..

 

[grindstone]

I always think you spend too much money on inquiries but I will defend your right to go wild Better shape.

Presumably you're 3-D printing a bezel and the WG and getting curvy veneered bling outsourced, but if you haven't heard the drivers before, big bevels (flats) both sides and top -- at least 2.5" -- and your foam skills can get you auditioning and measuring fast. FWIW.

Thanks for posting and carry-on, you wildman!

 

[Vineethkumar01]

Today's version of the cabinet..
Color scheme is just for highlighting features and is not final..
I really like this version of the cabinet too..

 

[Vineethkumar01]

I might have arrived at something which balances important things along with looks, I think..
(Colors are not final)

 

[rwnano]

Extremely amazing work and fine craftsmanship and efforts! Best wishes

 

[Vineethkumar01]

Before I finally go ahead with the build, I took some time to do detailed Akabak simulations of the waveguide in this final cabinet
For that, here is the process

1) Stripping down the cabinet to surfaces with only essential features


2) Integrating the waveguide with it


3) Meshing the whole thing


4) Doing sims in Akabak in half symmetry


Dome driver modeling of the SB26ADC/CDC using actual dimensions


5) Generating horzontal and vertical polars



6) Converting everything into a more easily visualizable format




We have good directivity control down to 1kHz.
The cabinet shape and depth help extend the usable directivity control of the waveguide from 2.6kHz (128mm diameter waveguide) down to 1 to 1.3 kHz. It is an octave more of directivity control for free..
I am very happy with the way things are looking now..