Hi all, first post on this forum!
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 Fostex lab studio monitor 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 or B&C 250)
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 as per the original design - to the horn then run a super tweeter from 7k up, (Fostex FT17H?). Does my design look suitable for this?
Not confident in crossover design but have used lots of DSP in live sound scenarios, but would rather run passive from one amp rather than active with DSP on 3 amps so need to work that out. The original crossover plans for the H400/Wa3002 combo are available, how much would it cost to get give someone a list of the drivers I am using and the old crossover plans and get them to make a passive crossover? Thinking Crown macro tech amp(s).
Thanks in advance!
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 Fostex lab studio monitor 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 or B&C 250)
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 as per the original design - to the horn then run a super tweeter from 7k up, (Fostex FT17H?). Does my design look suitable for this?
Not confident in crossover design but have used lots of DSP in live sound scenarios, but would rather run passive from one amp rather than active with DSP on 3 amps so need to work that out. The original crossover plans for the H400/Wa3002 combo are available, how much would it cost to get give someone a list of the drivers I am using and the old crossover plans and get them to make a passive crossover? Thinking Crown macro tech amp(s).
Thanks in advance!
It will not work, look at the acoustical differences in the raw drivers and it should say itself already.
Noone can make a well working crossover from a list of drivers, and a old crossover schematic for different drivers.
The W300A2 has a very different set of parts, parameters and behavior.
It has been designed to give a smooth and easy to handle rolloff with a passive xo.
The Le is 1/5th? of the B&C, the power handling is even less.
Suspension parts are much softer. FS is half of the B&C,. VAS is 3 times higher.
Cone and surroundhas been extensively treated to give a smooth and resonance free/damped response.
the W300A2's can be found in Japan but they will set you back about 3000$ for a pair in excellent condition.
Very different then a high efficiency PA mid bass with a stiff suspension optimized to go loud in a small box with a lot of power.
DSP is likely your friend here.
As for modern 1" drivers, BMS 5530ND, 18S ND1095N are all good examples.
They outperform the DE250. And 800hz is a stretch for most 1" drivers.
Thanks for the response Arez! Thought the crossover idea might be a bit ambitious, will probs start on the dsp route.
I went for the B&C 12NDL76 as it had similar t/s parameters when I used an online comparison tool but looking at the actual specs they are way off!
Have you got any suggestions for a modern affordable driver that is closer to the fostex?
I went for the B&C 12NDL76 as it had similar t/s parameters when I used an online comparison tool but looking at the actual specs they are way off!
Have you got any suggestions for a modern affordable driver that is closer to the fostex?
For a 1" CD, have a look at Radian. I have a 650B (an older model) and it works fine at 850Hz where I cross over at 24db/oct. They are built like tanks. I doubt you could damage it in a domestic application.
Most of the drivers with "similar" parameters (higher vas, lower fs, less stiff suspension, lower Le etc.) are not super modern, easy to come by or affordable.
TAD 1102, JBL 1200FE, Davis acoustics AL-1102, Acoustic Elegance 12", GPA 414 etc.
There is a good selection you can look through and try to source, not all are modern far from it.
From modern PA manufacturers the Beyma 12BR70 is probably as close as you will come.
Faital 12RS430 possibly.
This could be a little dangerous and an untested deep dive, but why not something like...
The Eminence Alpha 12 (extreme) or Beta 12 (looks more versatile), or a similar bass guitar-oriented woofer. Use it sealed instead of vented. Look for parameters like low cone mass, small coil, low Xmax, high VAS, non-conductive VC former and minimum power.
Mate that with a Pass F1 or F2, or something similar with a high output impedance. The woofer's impedance peak will likely get a slight bass boost from that kind of amplifier, so this is the right time to keep that option in mind: before you've built the box, and avoiding confusion later! Most simulators default to something close to zero ohms output resistance, but if it's actually several ohms, you'll see how it changes the relative bass levels.
There's also a Pass designed active filter, probably in the DIYAudio store, which could be a good starting point for modding to get the filter slopes that you need. You could design a passive crossover, but the different speaker sensitivity is just another unwanted variable added to the mix.
The Eminence Alpha 12 (extreme) or Beta 12 (looks more versatile), or a similar bass guitar-oriented woofer. Use it sealed instead of vented. Look for parameters like low cone mass, small coil, low Xmax, high VAS, non-conductive VC former and minimum power.
Mate that with a Pass F1 or F2, or something similar with a high output impedance. The woofer's impedance peak will likely get a slight bass boost from that kind of amplifier, so this is the right time to keep that option in mind: before you've built the box, and avoiding confusion later! Most simulators default to something close to zero ohms output resistance, but if it's actually several ohms, you'll see how it changes the relative bass levels.
There's also a Pass designed active filter, probably in the DIYAudio store, which could be a good starting point for modding to get the filter slopes that you need. You could design a passive crossover, but the different speaker sensitivity is just another unwanted variable added to the mix.
Thanks all for your comments, it is hugely helpful. I am still leaning towards a ported box to keep it similar to the 80s Fostex design at the moment. I think the Faital is looking like a good option?
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 out of interest but 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...
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 out of interest but 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...
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