Does my box for B&C 12NDL76 look right??

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   Hi all,
Firstly, I know this might be suited to DIY audio forum or other hifi sites but I thought I would ask here first!

I am embarking on on a new project with a friend who is a skilled cabinet maker with access to cnc etc to build some speakers inspired by this series.
https://www.preservationsound.com/2013/09/fostex-laboratory-series-pro-audio-monitors-c-1980/
The plan is to use the plans for the h400 horn available here: Here is construction plans for Fostex Type of H400 wooden horns - Techtalk Speaker Building, Audio, Video Discussion Forum  make out of Sapele and match with a modern 1 inch comp that is suitable (any suggestions welcomed - thinking BMS 4550) 

and build a LF box inspired by this matching cab from the 80s:

https://www.fostexinternational.com/docs/speaker_components/pdf/recom_enclose/w300aII_encl.pdf

but modify for B&C 12NDL76 rather than the original Fostex driver, which I have done here = Subwoofer Box B&C Speakers 12NDL76 | Ported Box | Slot . 

Planning to run as low as possible and cross at 800hz - to the horn then run a slot tweeter from 7k up. Does my design look suitable for this?

Still have some questions around passive/active crossovers etc but designing a suitable bass cab to match the horn is the first stage. 

Thanks in advance!

Edit - Links sorted

Edited by sarsen1 - 11 December 2024 at 5:01pm

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sarsen1 Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 01 January 2016 Location: Bristol Status: Offline Points: 130	Post Options Post Reply Quote sarsen1 Report Post Thanks(0) Quote Reply Topic: Does my box for B&C 12NDL76 look right?? Posted: 11 December 2024 at 3:09pm
	Hi all, Firstly, I know this might be suited to DIY audio forum or other hifi sites but I thought I would ask here first! I am embarking on on a new project with a friend who is a skilled cabinet maker with access to cnc etc to build some speakers inspired by this series. https://www.preservationsound.com/2013/09/fostex-laboratory-series-pro-audio-monitors-c-1980/ The plan is to use the plans for the h400 horn available here: Here is construction plans for Fostex Type of H400 wooden horns - Techtalk Speaker Building, Audio, Video Discussion Forum make out of Sapele and match with a modern 1 inch comp that is suitable (any suggestions welcomed - thinking BMS 4550) and build a LF box inspired by this matching cab from the 80s: https://www.fostexinternational.com/docs/speaker_components/pdf/recom_enclose/w300aII_encl.pdf but modify for B&C 12NDL76 rather than the original Fostex driver, which I have done here = Subwoofer Box B&C Speakers 12NDL76 \| Ported Box \| Slot . Planning to run as low as possible and cross at 800hz - to the horn then run a slot tweeter from 7k up. Does my design look suitable for this? Still have some questions around passive/active crossovers etc but designing a suitable bass cab to match the horn is the first stage. Thanks in advance! Edit - Links sorted Edited by sarsen1 - 11 December 2024 at 5:01pm

ceharden Members Profile Send Private Message Find Members Posts Add to Buddy List The 10,000 Points Club Joined: 05 June 2005 Location: Southampton Status: Offline Points: 11851	Post Options Post Reply Quote ceharden Report Post Thanks(0) Quote Reply Posted: 11 December 2024 at 8:27pm
	While a very good driver for PA mid-tops, it wouldn't be my first choice for something to go all the way down into the bass region properly. I also wouldn't recommend a very narrow slot port because you'll get a lot of air resistance against the internal surfaces and the tuning could end up a lot different to the simulation. Maybe try to reduce the difference between width and height if you can. Theoretically round ports are ideal (minimum internal surface area vs cross sectional area), square ports are good etc.

sarsen1 Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 01 January 2016 Location: Bristol Status: Offline Points: 130	Post Options Post Reply Quote sarsen1 Report Post Thanks(0) Quote Reply Posted: 11 December 2024 at 9:12pm
	Thanks for the response, very helpful! That does make sense re the B&C, any suggestions for a suitable 12 inch driver that could get low and maintain some midrange articulation in such a box? It will not need to go PA loud, more listening bar style.

ceharden Members Profile Send Private Message Find Members Posts Add to Buddy List The 10,000 Points Club Joined: 05 June 2005 Location: Southampton Status: Offline Points: 11851	Post Options Post Reply Quote ceharden Report Post Thanks(0) Quote Reply Posted: 11 December 2024 at 11:37pm
	You're going to need to do some simulations in WinISD or similar to get an idea of the low frequency response. The 12NDL76 won't be happy in a large box, it's designed to be used in a much smaller one. It might be going a bit the other way but if you want low extension but aren't so bothered about high efficiency, then something like the Faital Pro 12RS430 could be worth considering: https://www.bluearan.co.uk/index.php?id=FTP12RS430AP Since you're only going to 800Hz, there's a lot of drivers which will be comfortable doing that.

sarsen1 Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 01 January 2016 Location: Bristol Status: Offline Points: 130	Post Options Post Reply Quote sarsen1 Report Post Thanks(0) Quote Reply Posted: 12 December 2024 at 8:39am
	Thanks, yeah I need to get WinISD but on a Mac so struggling at the moment. Someone else suggested that Faital Pro 12RS430 so seems like a good choice, also the Beyma 12BR70. I think one of those will be the way to go. If one of those was happy up to 1000hz or even 1.2khz it would open up my options for a compression driver too. Will try and get WinISD going and should hopefully be fairly easy to get a suitable box designed for one of these drivers. Cheers!

sarsen1 Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 01 January 2016 Location: Bristol Status: Offline Points: 130	Post Options Post Reply Quote sarsen1 Report Post Thanks(0) Quote Reply Posted: 12 December 2024 at 11:20am
	Okay so I managed to get WinISD going and gave it my first go, the blue is the OG Fostex driver in a 100ltr 28hz tuned box, 1w 1m showing SPL. The blue is the the Faital driver and the green is the Beyma all in the same box. The response for the Faital looks to be very close to the Fostex but just quieter(?), but am I right in thinking this fine because the Fostex driver is a 50 watt driver and the Faital is a 400w driver that I could just just give the driver more power and get a similar response? Also looks good to me up higher, will come down to some testing and playing with gains and x/over points I guess. And I did put the B&C driver in but as predicted it looked like a rollercoaster so took it out for clarity Also The Faital vs Fostex air port velocity below, both with round ports 80mm/130mm do I need to do some tuning for the Faital here? It only shows data for rear port not front even though the image shows the port at the font... [Edit did not change the signal input for these so not valid] Edited by sarsen1 - 12 December 2024 at 12:13pm

ceharden Members Profile Send Private Message Find Members Posts Add to Buddy List The 10,000 Points Club Joined: 05 June 2005 Location: Southampton Status: Offline Points: 11851	Post Options Post Reply Quote ceharden Report Post Thanks(0) Quote Reply Posted: 12 December 2024 at 5:20pm
	I would definitely go for the Faital Pro over the Beyma which is more of a HiFi driver really. I don't think you're likely to have issues with the port air velocity in this design unless you go for some very small ports. I'd be more worried about the shape of your ports as previously mentioned.

sarsen1 Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 01 January 2016 Location: Bristol Status: Offline Points: 130	Post Options Post Reply Quote sarsen1 Report Post Thanks(0) Quote Reply Posted: 14 December 2024 at 6:58pm
	Have taken your advice and gone for round ports and the Faital, Subwoofer Box FaitalPRO v1.3 \| Ported Box around 300mm seems to sim about right, but does that seem quite long for a box this size? Thinking about making them out of rings of hardwood glued together. Edited by sarsen1 - 14 December 2024 at 7:00pm

ceharden Members Profile Send Private Message Find Members Posts Add to Buddy List The 10,000 Points Club Joined: 05 June 2005 Location: Southampton Status: Offline Points: 11851	Post Options Post Reply Quote ceharden Report Post Thanks(0) Quote Reply Posted: 16 December 2024 at 11:31am
	Use drainpipe, you can use a few rings of ply on the back of the panel to support it and/or make it less obvious. Two 50x50 square ports in the corners or a rectangular port 100x50 would be the alternatives. The issue with the original design was just that going the full width made the port very narrow.