A 2 way horn project

[Vineethkumar01]

Hello All,

I am starting a 2 way horn project (configuration remains 2 way for now. May become 3 way if we hit design limitations later). The drivers (for now) will be a 15inch Faital pro 15PR400-8 (https://faitalpro.com/en/products/LF_Loudspeakers/product_details/index.php?id=101060100) as the mid-woofer and a compression driver in a horn for the upper end (Let's consider that the CD is SB Audience Rosoos-65 CDN-T 1.4inch neodymium compression driver (http://www.sbaudience.com/index.php/products/compression-drivers/rosso-65cdn-t/) ). The horn/waveguide which will load this driver is yet undecided (there are always options like LTH series horns from faital and other options from 18 sound etc but I want to build a customized horn). I am in the process of asking friends regarding feasibility of getting a horn made. The crossover will be active with DSP.

My projects often stall at the phase where we have to put drivers in a proper cabinet. This is due to me having no time and space to do woodworking where I live. I am also not able to get help from friends/others (at this time since everyone is busy with office work after return to office kind of policies) who know woodworking in getting this part done .. Hopefully, I will get cabinets made with someone's help later but till then we explore and learn. With this limitation aside, let us try to make the learning process involved in the design of such a speaker as much fun and useful (to all of us) as possible.. This is the motivation behind this thread.

I will start with trying to come up with a box (bass) alignment for the woofer. My listening space is either a 16ish m2 room or a 25ish m2 room. My constraints for the cabinet are 1) It should be manageable size 2) It should look good. Without these two, I along with my projects will be kicked out of the house

With these thoughts in mind, I have chosen a cabinet shape as shown in attached pics-1 and 2 (shows back and front of intended cabinet shape). A possible shape with woofer and horn is shown in pic 3 (with/without ports). It favors corner placement in addition to moving away from the rectangular box design, which may come with its own advantages in terms of standing wave mode suppression etc (will verify all these later with measurements).
For now, please see the measured impedance curves for the two woofers that I have in the attached pic 4 (without any 'break in')

I will update this space with T/S parameter measurements of the drivers, further measurements baffle/cabinet sizes, etc next.
Welcoming your comments and suggestions

 

[chander]

I requested Mr. Murthy from Bangalore to build me speaker stands which were copies of Hi-Fi Racks stands. He did a pretty good job, maybe he can help you with cabinet building? No harm speaking with him in any case.

 

[Vineethkumar01]

I requested Mr. Murthy from Bangalore to build me speaker stands which were copies of Hi-Fi Racks stands. He did a pretty good job, maybe he can help you with cabinet building? No harm speaking with him in any case.

Thanks @chander for the suggestion I will explore this option.

 

[Vineethkumar01]

Here is what a closed box of 100 litres will give us (attached pic shows more details) for this woofer.

STATISTICS
f3 87.2 Hz
f6 59.1 Hz
f10 41.8 Hz
Zmin 5.2 Ohm @ 354 Hz
Zmax 42.3 Ohm @ 62.6 Hz
GDmax 3.6 ms @ 32.2 Hz
XmaxC 2.6 mm @ 5 Hz
Pmax 7.9 VA @ 354 Hz
-------------------------------------------------------------
DRIVER: FaitalPRO 15PR400, 1 pcs in series
n0 2.73 % Reference efficiency
SPL 96.5 dB/W Sensitivity
USPL 98.4 dB/2.83 Sensitivity
EBP 102.9 Efficiency bandwidth product
Dd 32.0 cm Effective diameter of driver
Vd 462.9 cm^3 Maximum linear volume of displacement
Cas 1.56E-6 m^5/N Acoustic equivalent of Cms
Mas 1.31E1 kg/m^4 Acoustic equivalent of Mms+Mme
Ras 4.8E2 Ns/m^5 Acoustic equivalent of Rms
Rae 8.44E3 Ns/m^5 Acoustic equivalent of Re+Rg
Lces 6.69E-2 H Electrical inductive equivalent of Cas
Cmes 3.05E-4 F Electrical capacitive equivalent of Mas
Res 8.97E1 Ohm Electrical resistive equivalent of Ras
-------------------------------------------------------------
BOX REAR 1: Vb=100.0 l, Ql=15.0
Fb 62.9 Hz System resonance frequency
Cab 7.08E-7 m^5/N Acoustic compliance of air in enclosure
Rab 4.47E2 Ns/m^5 Acoustic resistance due to absorption
Ral 5.36E4 Ns/m^5 Acoustic resistance due to leakage
Lceb 3.05E-2 H Electrical inductive equivalent of Cab
Reb 9.64E1 Ohm Electrical resistive equivalent of Rab
Rel 8.03E-1 Ohm Electrical resistive equivalent of Ral
Qtc 0.55 Total Q factor

 

[madman29]

Hello All,

I am starting a 2 way horn project (configuration remains 2 way for now. May become 3 way if we hit design limitations later). The drivers (for now) will be a 15inch Faital pro 15PR400-8 (https://faitalpro.com/en/products/LF_Loudspeakers/product_details/index.php?id=101060100) as the mid-woofer and a compression driver in a horn for the upper end (Let's consider that the CD is SB Audience Rosoos-65 CDN-T 1.4inch neodymium compression driver (http://www.sbaudience.com/index.php/products/compression-drivers/rosso-65cdn-t/) ). The horn/waveguide which will load this driver is yet undecided (there are always options like LTH series horns from faital and other options from 18 sound etc but I want to build a customized horn). I am in the process of asking friends regarding feasibility of getting a horn made. The crossover will be active with DSP.

My projects often stall at the phase where we have to put drivers in a proper cabinet. This is due to me having no time and space to do woodworking where I live. I am also not able to get help from friends/others (at this time since everyone is busy with office work after return to office kind of policies) who know woodworking in getting this part done .. Hopefully, I will get cabinets made with someone's help later but till then we explore and learn. With this limitation aside, let us try to make the learning process involved in the design of such a speaker as much fun and useful (to all of us) as possible.. This is the motivation behind this thread.

I will start with trying to come up with a box (bass) alignment for the woofer. My listening space is either a 16ish m2 room or a 25ish m2 room. My constraints for the cabinet are 1) It should be manageable size 2) It should look good. Without these two, I along with my projects will be kicked out of the house

With these thoughts in mind, I have chosen a cabinet shape as shown in attached pics-1 and 2 (shows back and front of intended cabinet shape). A possible shape with woofer and horn is shown in pic 3 (with/without ports). It favors corner placement in addition to moving away from the rectangular box design, which may come with its own advantages in terms of standing wave mode suppression etc (will verify all these later with measurements).
For now, please see the measured impedance curves for the two woofers that I have in the attached pic 4 (without any 'break in')

I will update this space with T/S parameter measurements of the drivers, further measurements baffle/cabinet sizes, etc next.
Welcoming your comments and suggestions

Hi Vineethkumar01

I have used the same mid-woofer for my calpamos project by Humble homemade hifi. I guess you have already gone through that project. This project have used a Faital Pro tweeter. I found it necessary to add a tweeter/super tweeter with the calpamos project.

Wish you a happy DIY time ahead

Will wait for the construction pics!

 

[Vineethkumar01]

Hi Vineethkumar01

I have used the same mid-woofer for my calpamos project by Humble homemade hifi. I guess you have already gone through that project. This project have used a Faital Pro tweeter. I found it necessary to add a tweeter/super tweeter with the calpamos project.

Wish you a happy DIY time ahead

Will wait for the construction pics!

Thank you @madman29
I had seen your thread and was very excited reading it. Especially one of the posts about listening impressions an FM had posted in your thread.
Yes. I have gone through the Calpamos project and Troels' Faital 3WC-15 projects. There are several builds now with the 15PR400 driver on diyaudio forum and has been widely recommended there. These were my motivation in trying to do something with this driver.
In Calpamos project, I think the Faital HF 201 compression driver was used on P-audio horn. The driver having 2 inch throat will be able crossover lower with the woofer but will have issues at the high frequency range above 10K. I actually wanted to use a 1-inch throat CD (good at the high frequencies but needs higher crossover point) on an appropriate horn but all the 1inch CDs I want are not in stock at the moment. Hence, as a compromise, I chose the AB audience Rosso CDN65 which has a 1.4 inch throat. It will definitely not have much usable response above 15kHz due to breakup modes around 17kHz but my hearing stops at 14.5k or thereabouts..
I will write about more thoughts about the drivers and the overall project directions in the subsequent posts.
Thanks a lot for your wishes. I too sincerely hope that I will be able to able to get some construction pics. Speaker cabinet construction has been my nemesis so far in all projects..

 

[jls001]

Pic 1 & 2 don't show horn tweeter. Is the horn going to be in a different cabinet, or simply placed on top? Also, are these drivers available locally or have to be imported?

 

[madman29]

Thank you @madman29
I had seen your thread and was very excited reading it. Especially one of the posts about listening impressions an FM had posted in your thread.
Yes. I have gone through the Calpamos project and Troels' Faital 3WC-15 projects. There are several builds now with the 15PR400 driver on diyaudio forum and has been widely recommended there. These were my motivation in trying to do something with this driver.
In Calpamos project, I think the Faital HF 201 compression driver was used on P-audio horn. The driver having 2 inch throat will be able crossover lower with the woofer but will have issues at the high frequency range above 10K. I actually wanted to use a 1-inch throat CD (good at the high frequencies but needs higher crossover point) on an appropriate horn but all the 1inch CDs I want are not in stock at the moment. Hence, as a compromise, I chose the AB audience Rosso CDN65 which has a 1.4 inch throat. It will definitely not have much usable response above 15kHz due to breakup modes around 17kHz but my hearing stops at 14.5k or thereabouts..
I will write about more thoughts about the drivers and the overall project directions in the subsequent posts.
Thanks a lot for your wishes. I too sincerely hope that I will be able to able to get some construction pics. Speaker cabinet construction has been my nemesis so far in all projects..

Yes the Faital pro tweeter doesn't go as high as one would wish it to go. And after installing the JBL tweeter it was evident to me what the sound was missing.

But one thing I have noticed--- The micro details of sound of a well designed bookshelf speaker is something I should not expect from a speaker of the size we are discussing. It is all about dynamic range and sheer power of the low-end I was heading towards. At semi concert-hall level sound becomes a whole new beast if you understand what I mean. This is my personal opinion.

 

[aeroash]

Speaker cabinet construction has been my nemesis so far in all projects..

Will you be doing this by yourself, or do you have assistance from a carpenter?

 

[Vineethkumar01]

Pic 1 & 2 don't show horn tweeter. Is the horn going to be in a different cabinet, or simply placed on top? Also, are these drivers available locally or have to be imported?

Hi,
As of now the plan is to let the horn be placed on top/freestanding configuration. So that I will be able to experiment with different top modules. (Other horns/coaxials later)
Faital pro 15PR400 is available locally: https://www.soundland.in/, and here: https://www.paequipments.com/
SB Rosso/Bianco CDs are available here: https://diyaudiocart.com/index.php?route=product/search&search=SB audience
Even BMS, and 18sound are available locally here: https://gmaudio.co.in/,
Celestion here: https://www.decibelpro.in/speaker/loudspeakers-driver/hf-driver.html

I try to buy everything locally as much as possible.

Thanks
Vineeth

 

[Vineethkumar01]

Yes the Faital pro tweeter doesn't go as high as one would wish it to go. And after installing the JBL tweeter it was evident to me what the sound was missing.

But one thing I have noticed--- The micro details of sound of a well designed bookshelf speaker is something I should not expect from a speaker of the size we are discussing. It is all about dynamic range and sheer power of the low-end I was heading towards. At semi concert-hall level sound becomes a whole new beast if you understand what I mean. This is my personal opinion.

I am not heard many/any big woofer + CD systems in home settings except in clubs, live events and auditoriums. There, most often, I felt the focus is on high SPL levels. So I don't know much about the micro details aspects in these type of bigger systems.

But I have another project (an active 3 way using home audio hifi drivers) which is supposed to take care of micro detail aspects. Let's wait and see what these projects can bring along..

 

[Vineethkumar01]

Will you be doing this by yourself, or do you have assistance from a carpenter?

No question of me doing the cabinet completely by myself. I have built a 2 way in the past myself and bid bye-bye to the cabinet making part (at least MDF ). So I will definitely need help from some one. In the worst case, access to a CNC facility which is ready to cut parts.
Unfortunately, CNC shops near me and carpenters nearby are not interested in speaker box making..
So I will have to find some way out..

 

[aeroash]

No question of me doing the cabinet completely by myself. I have built a 2 way in the past myself and bid bye-bye to the cabinet making part (at least MDF ). So I will definitely need help from some one. In the worst case, access to a CNC facility which is ready to cut parts.
Unfortunately, CNC shops near me and carpenters nearby are not interested in speaker box making..
So I will have to find some way out..

May the force be with you!

If only we were in the same town; I would've been more than happy to lend you a hand.

 

[sandeepsasi]

No question of me doing the cabinet completely by myself. I have built a 2 way in the past myself and bid bye-bye to the cabinet making part (at least MDF ). So I will definitely need help from some one. In the worst case, access to a CNC facility which is ready to cut parts.
Unfortunately, CNC shops near me and carpenters nearby are not interested in speaker box making..
So I will have to find some way out..

Two years ago, I had briefly considered getting Troels Gravesen's Faital-3WC-12 built here in Bangalore. As you mentioned, it was almost impossible to find a carpenter/CNC workshop who was willing to take this up. And a few who were willing did not instill confidence - they were trying to picture the speaker box as a regular cupboard and were tying to argue with me why the extent of bracing needed is not necessary and even advised me to use nails to hold the pieces together in place of glue.

Given the size of your cabs, you'll be needing large clamps to hold the pieces together after gluing. I don't think regular carpenters will have these many with them and even if they do, they may not be of the size needed.

Eight Audio in Hyderabad does custom cabinet builds. They have CNC machinery and other equipment and are specialists in speaker building. But, it'll definitely cost you a lot.

If you are keen on getting it done locally, then as someone already mentioned Mr. Murthy will be your best bet. It'll be good to send him some rough sketches and let him know the magnitude of effort needed and I'm sure he'll be able to guide you.

And if it had been me in your place, I would have got the cabs built by @sadik . Even if you account for the cost of packing and shipping from Baroda, I think it'll still be worth the effort and save you a lot of time, effort and mental agony when compared to dealing with regular local carpenters.

With regards,
Sandeep Sasi

 

[Vineethkumar01]

May the force be with you!

If only we were in the same town; I would've been more than happy to lend you a hand.

Thank you very much.
I too sincerely hope this projecr will turn out well and will add some value to me personally and the community in general, even if it is infinitesimally small.

 

[Vineethkumar01]

Two years ago, I had briefly considered getting Troels Gravesen's Faital-3WC-12 built here in Bangalore. As you mentioned, it was almost impossible to find a carpenter/CNC workshop who was willing to take this up. And a few who were willing did not instill confidence - they were trying to picture the speaker box as a regular cupboard and were tying to argue with me why the extent of bracing needed is not necessary and even advised me to use nails to hold the pieces together in place of glue.

Given the size of your cabs, you'll be needing large clamps to hold the pieces together after gluing. I don't think regular carpenters will have these many with them and even if they do, they may not be of the size needed.

Eight Audio in Hyderabad does custom cabinet builds. They have CNC machinery and other equipment and are specialists in speaker building. But, it'll definitely cost you a lot.

If you are keen on getting it done locally, then as someone already mentioned Mr. Murthy will be your best bet. It'll be good to send him some rough sketches and let him know the magnitude of effort needed and I'm sure he'll be able to guide you.

And if it had been me in your place, I would have got the cabs built by @sadik . Even if you account for the cost of packing and shipping from Baroda, I think it'll still be worth the effort and save you a lot of time, effort and mental agony when compared to dealing with regular local carpenters.

With regards,
Sandeep Sasi

Thank you for your suggestions
In fact I too don't know of anyone better than Sadik to handle these kind of speaker projects. He has helped me in the past with my smaller two way build. In fact, I have also requested requested his advice and help on part of this project. When i asked him last time for another project he had concerns regarding the shipping part with which he had bad experiences in the past. So he suggested me to enquire locally for big speaker cabinets. Hence the dilemma. But I will try.

 

[sandeepsasi]

Thank you for your suggestions
In fact I too don't know of anyone better than Sadik to handle these kind of speaker projects. He has helped me in the past with my smaller two way build. In fact, I have also requested requested his advice and help on part of this project. When i asked him last time for another project he had concerns regarding the shipping part with which he had bad experiences in the past. So he suggested me to enquire locally for big speaker cabinets. Hence the dilemma. But I will try.

Yes, shipping is indeed a concern!

If at all you end up going down this route, I would advise you to bubble wrap the cabinets, pack them in cardboard (with thermocol pieces sandwiched in between) and finally enclose them in wooden crates (with packing beans in between). If you choose a shipping partner like Agarwal Packers, chances of your package being dropped from a height is very less (though not zero). Also, if possible insure the package (a small declared value will do) and mark the item as fragile on all sides (if possible in English, Gujarati, Hindi and Kannada).

At least this was one of my plans, had the Faital-3WC-12 project gone through. The other was to drive to Baroda to pick the finished speakers up.

With regards,
Sandeep Sasi

 

[Vineethkumar01]

In the real world, Cabinet making is difficult for now.
But in the world of make-believe, here is a simulation showing the axial modes that can exist in a 100L volume cuboidal cabinet of the dimensions shown in the pic (width -red, height -green, depth-blue). The peaks tell us the frequencies which can cause standing wave issues, which need to be either taken care of by driver positioning and/or by absorption material at right places in the cabinet, if possible. modes above 1kHz are not of much concern for now as the driver will be crossed over below that.
In the pic, we also have a cabinet with a lot of construction related details specified like box width, height, depth, total volume (except the bracing, which will take away a bit more usable volume) , thickness of panels that forms the sides, front etc.

 

[Vineethkumar01]

Woofer on baffle: Diffraction response/Baffle step

In this exercise, we try to see what happens to the on-axis response of the woofer (assuming it is an ideal circular piston), when it is put on a baffle of width = 506mm and height = 850mm (almost same as what we chose for the above box simulation). Here is what happens (as seen by a mic placed 2m away pointing to the driver center on this baffle):

Above we can see that the diffraction response is smooth after 1kHz. The full diffraction step of 6dB occurs around 1kHz. Preceding this is the hump which goes to around 8 dB at the max and then gently droops downwards with an almost first order filter response (~5 dB/octave to be more specific in this case) as we go down in frequency starting around 300 Hz.

 

[Vineethkumar01]

Driver in the box: Directivity simulation

Now, let us put the driver in the 100L box of the above mentioned dimensions and see how its directivity is affected. Again, we will assume that it is a rigid circular piston on the above baffle but now attached to the 100L box. VituixCAD doesn't take into account the effect of depth of the box on the directivity response, but still this is very useful. Any more complete modeling requires BEM simulations which is beyond the scope of this project, for now.
Here is the complete set of plots:


In the above set of plots, the most noteworthy one regarding directivity is the horizontal directivity plot (3rd row, first column). We can see that the horizontal directivity (-6 dB loss in strength of radiation compared to on-axis response) reaches +45 degrees and -45 degrees (hence 90 degree coverage) around 800 Hz. Looking at the vertical directivity plot to the immediate right, similar things happen around the same 800 Hz. So I guess around this point is where we want to hand over the duties to a compression driver in a horn/waveguide (that has a horizontal coverage of 90 degrees) for a directivity-matched transition/crossover.

Unfortunately, this is where we stop with these kind of simulations for now. Anything more will make sense only if we get the drivers in at least a prototype box, measure it and make an attempt at crossover design based on the driver responses..