I'm pretty convinced to build an F-5T V2 .
I may switch to a monoblock in the future.
I don't want to use a crossover and use a subwoofer, I prefer simple things well done.
My speakers have good frequency response I just need to find a good amp that will run class A at 2.7 impedance.
I really think I will listen to Dirk and Nelson's suggestions and start building an F-5T V2.
Any suggestions are welcome.
Thanks for your feedback, it was very helpful.
Cheers
I may switch to a monoblock in the future.
I don't want to use a crossover and use a subwoofer, I prefer simple things well done.
My speakers have good frequency response I just need to find a good amp that will run class A at 2.7 impedance.
I really think I will listen to Dirk and Nelson's suggestions and start building an F-5T V2.
Any suggestions are welcome.
Thanks for your feedback, it was very helpful.
Cheers
Hi again Giubos,
Interestingly the answers given are pretty well aligned - but many different ways of explaining it.
But just to address the 2.7ohm, especially since this is w.o. filter and thus mainly resistive you really should not worry about this at all.
While you might see some small impedance humps from the Fs tuning points of the membrane, it will overall be an easy load with negligible phase-angles.
I have had several Magneplanars and also been driving these active w.o. filter as well as the small Apogee's
On these the 50W Kl.A Threshold SA/3 was fully adequate in a slightly smaller but much harder damped room than yours. SA/1's was quite a bit more than needed. and the same actually - unsurprisingly - goes for my V4H lateral mosfet amps, a cousin to your P101's ;-)
As Nelson hinted at the V2T will give you the 100W+ in 2.7 ohm that you need.
One other thing you might want to consider also (sorry for opening up another can of worms) is actually using Exicons instead of your current lateral mosfets, these are renowened for their low end performance compared to Hitachi/Renesas versions - and while i cannot tell how these will compare to your Hitachis, these for sure have been providing the best bottom end control on the magnetostatics yet experienced - while not being lean.
Some notes, make sure you run the F5 hot, 50C, I preferred the Toshiba outputs slightly softer fluid character, but that might be negligible with a tube pre.
Wish you good fun with your build!
Interestingly the answers given are pretty well aligned - but many different ways of explaining it.
But just to address the 2.7ohm, especially since this is w.o. filter and thus mainly resistive you really should not worry about this at all.
While you might see some small impedance humps from the Fs tuning points of the membrane, it will overall be an easy load with negligible phase-angles.
I have had several Magneplanars and also been driving these active w.o. filter as well as the small Apogee's
On these the 50W Kl.A Threshold SA/3 was fully adequate in a slightly smaller but much harder damped room than yours. SA/1's was quite a bit more than needed. and the same actually - unsurprisingly - goes for my V4H lateral mosfet amps, a cousin to your P101's ;-)
As Nelson hinted at the V2T will give you the 100W+ in 2.7 ohm that you need.
One other thing you might want to consider also (sorry for opening up another can of worms) is actually using Exicons instead of your current lateral mosfets, these are renowened for their low end performance compared to Hitachi/Renesas versions - and while i cannot tell how these will compare to your Hitachis, these for sure have been providing the best bottom end control on the magnetostatics yet experienced - while not being lean.
Some notes, make sure you run the F5 hot, 50C, I preferred the Toshiba outputs slightly softer fluid character, but that might be negligible with a tube pre.
Wish you good fun with your build!
Hi Noorgard,
thanks for your very interesting feedback, I'd love to know more about the P101's cousin (schematic, power and bias and mosfets used), and to know which amp you prefer to play with since you have a lateral mosfet power amp and I assume also an F-5T.
I have almost finished for a friend an amp with Exicon so I will try the difference of Hitachi vs Exicon mosfets.
I'll tell you my intentions for the F-5T.
Dual mono configuration, with two 600VA transformers and 60kmicro on the 30+ 60kmicro on the 30- CRC.
I use a tube preamp and I like the smooth sound and I would like to know more Toshiba ( where did you get them and what initials do they have, I am in italy I have to try from local suppliers).
Thanks for your attention and if there are things I said that you think are wrong don't hesitate to tell me.
Cheers
Giubos
thanks for your very interesting feedback, I'd love to know more about the P101's cousin (schematic, power and bias and mosfets used), and to know which amp you prefer to play with since you have a lateral mosfet power amp and I assume also an F-5T.
I have almost finished for a friend an amp with Exicon so I will try the difference of Hitachi vs Exicon mosfets.
I'll tell you my intentions for the F-5T.
Dual mono configuration, with two 600VA transformers and 60kmicro on the 30+ 60kmicro on the 30- CRC.
I use a tube preamp and I like the smooth sound and I would like to know more Toshiba ( where did you get them and what initials do they have, I am in italy I have to try from local suppliers).
Thanks for your attention and if there are things I said that you think are wrong don't hesitate to tell me.
Cheers
Giubos
Toshibas are IRFP240, with 9240s providing a sweet touch due to a midrange anomaly in those fets, giving some sugar/2. order harmonic. On newer F5T boards you can tune this with P3.
I also have a set of matched Fairchild MOSFETs from the original circuit by Papa. They will probably sound a bit cleaner but also more unforgiving wrt bad DACs and sources. They will however provide the huge amounts of current the original circuit was made to provide (unsure how the Toshibas fair currentwise, too lazy to check now but easily searchable in the datasheets).
Give me a shout if Fairchilds and F5T boards are of interest.
Also, beware of Dennis Hui’s warning. This amp can be moody 🙂
Hi Giubos,
With the F5T V2, you can get 100W into 2.7 ohms.
But if your goal is 100W into 2.7 ohms in class A, then it may be tricky getting it as-is. With only two transistors per rail you are looking at well over 50W dissipation per mosfet. And the existing source resistors/diode combo will need to be adjusted to support the quiescent current required.
A larger output stage (like the 4 mosfet per rail in Turbo V3) will be better at handling the heat, again, if 100W class A is your goal.
With the F5T V2, you can get 100W into 2.7 ohms.
But if your goal is 100W into 2.7 ohms in class A, then it may be tricky getting it as-is. With only two transistors per rail you are looking at well over 50W dissipation per mosfet. And the existing source resistors/diode combo will need to be adjusted to support the quiescent current required.
A larger output stage (like the 4 mosfet per rail in Turbo V3) will be better at handling the heat, again, if 100W class A is your goal.
Hi Cubicincher, I am planning to put a subwoofer on my hi-fi system and I would like to ask you a few things about using the sub.
My system is composed as follows:
I would like to insert a 24/db electronic crossover after the preamplifier with one output to the amplifier and one to the active sub.
Is this correct in your opinion, based on your experience?
Another question which sub are you using and which one do you recommend?
Is the sub you use active or passive?
As always there are of all prices, but considering that they only need to output frequencies below 100 Hz which are not directional I don't know if it is worth spending a lot.
What kind of crossover are you using and is the correct position after the preamplifier, or would you use it before the pre just after the converter?
In any case I should only send frequencies above 80 or 100 Hz to the amplifier.
Thank you in advance for your kind reply, and good music.
Cheers.
Giubos
Translated with www.DeepL.com/Translator (free version)
My system is composed as follows:
- "cambridge CX" cd player
- "Shiit audio GUNGNIR" converter
- "freya+" preamplifier used with tubes
- "DIY" high-polarised 235 watt class AB mosfet amplifier
I would like to insert a 24/db electronic crossover after the preamplifier with one output to the amplifier and one to the active sub.
Is this correct in your opinion, based on your experience?
Another question which sub are you using and which one do you recommend?
Is the sub you use active or passive?
As always there are of all prices, but considering that they only need to output frequencies below 100 Hz which are not directional I don't know if it is worth spending a lot.
What kind of crossover are you using and is the correct position after the preamplifier, or would you use it before the pre just after the converter?
In any case I should only send frequencies above 80 or 100 Hz to the amplifier.
Thank you in advance for your kind reply, and good music.
Cheers.
Giubos
Translated with www.DeepL.com/Translator (free version)
Hello Giubos,
I used different subwoofers over the years. My most used one is an JBL 15inch woofer (38cm diameter). I made my own cabinet for it.
I also used subwoofers with multiple 8 inch (20cm) drivers, which are faster. One of the best compromise for drivers in a sub are 12 inchers -
still pretty fast and go low in the frequency-range.
I drive it with powerful classAB amps (professional amps for PA) or I use one of my PASS BA-3 classA-amps. What I wouldn't have believed-
the BA-3 drives the JBL-sub with ease to pretty loud levels (it is a 4 Ohm driver with 97dB/W/m).
Active crosssovers also changed over the years ( DBX, Behringer, self-built-AXOs based on OPAmps). For me one of the best sounding active crossovers
is the 6-24 AXO from Nelson Pass. Especially at this pricepoint! A real gift / present from Mister Pass!
My preferred crossover frequency (between sub and mainspeakers is around 80 - 100 Hz).
I use my Audiostatic ESLs and also a fully active 2-way-speaker (AirMotionTransformer and 6 inch midbass actively driven by PASS-amps and a second
6-24 AXO).
I hope this helps a bit for further decisions...
Cheers
Dirk 🙂
I used different subwoofers over the years. My most used one is an JBL 15inch woofer (38cm diameter). I made my own cabinet for it.
I also used subwoofers with multiple 8 inch (20cm) drivers, which are faster. One of the best compromise for drivers in a sub are 12 inchers -
still pretty fast and go low in the frequency-range.
I drive it with powerful classAB amps (professional amps for PA) or I use one of my PASS BA-3 classA-amps. What I wouldn't have believed-
the BA-3 drives the JBL-sub with ease to pretty loud levels (it is a 4 Ohm driver with 97dB/W/m).
Active crosssovers also changed over the years ( DBX, Behringer, self-built-AXOs based on OPAmps). For me one of the best sounding active crossovers
is the 6-24 AXO from Nelson Pass. Especially at this pricepoint! A real gift / present from Mister Pass!
My preferred crossover frequency (between sub and mainspeakers is around 80 - 100 Hz).
I use my Audiostatic ESLs and also a fully active 2-way-speaker (AirMotionTransformer and 6 inch midbass actively driven by PASS-amps and a second
6-24 AXO).
I hope this helps a bit for further decisions...
Cheers
Dirk 🙂
Hi Dirk,
Thank you for your reply.
I want to read up on Mr Pass' 6-24 AXO before deciding .
I have not found much on electronic crossovers. I have seen the Behringer and the dbx, but I have the RCA amp input not XLR. I think I will get a 12 inch passive sub and use one of my DIY amps. How many watts for the 12 inch subwoofer .
Do you have any info on the construction of the 6-24 AXO I don't know them, and is the output in stereo or mono.
Thanks again for the support.
Giubos
Translated with www.DeepL.com/Translator (free version)
Thank you for your reply.
I want to read up on Mr Pass' 6-24 AXO before deciding .
I have not found much on electronic crossovers. I have seen the Behringer and the dbx, but I have the RCA amp input not XLR. I think I will get a 12 inch passive sub and use one of my DIY amps. How many watts for the 12 inch subwoofer .
Do you have any info on the construction of the 6-24 AXO I don't know them, and is the output in stereo or mono.
Thanks again for the support.
Giubos
Translated with www.DeepL.com/Translator (free version)
Hello Giubos,
the 6-24 AXO is a 2-way-stereo-active - crossover. Offered in the DIYaudioStore - Design by Nelson Pass.
But you have to decide in which frequency range has to be your crossoverpoint. The shop offers the pcb and matched J113-JFets.
Oh, sold out at the moment!
I posted so much in the 6-24 AXO-thread with different recipes. I would ask you to have a look there.
https://www.diyaudio.com/community/threads/diy-biamp-6-24-crossover.357657/
How many Watts for a 12 inch sub? It always depends on the driver / subwoofer. If you have one with a pretty good efficiency - lets say above 94 dB/W/m or higher- 40 - 50 W in ClassA can be a lot.
Cheers
Dirk
the 6-24 AXO is a 2-way-stereo-active - crossover. Offered in the DIYaudioStore - Design by Nelson Pass.
But you have to decide in which frequency range has to be your crossoverpoint. The shop offers the pcb and matched J113-JFets.
Oh, sold out at the moment!
I posted so much in the 6-24 AXO-thread with different recipes. I would ask you to have a look there.
https://www.diyaudio.com/community/threads/diy-biamp-6-24-crossover.357657/
How many Watts for a 12 inch sub? It always depends on the driver / subwoofer. If you have one with a pretty good efficiency - lets say above 94 dB/W/m or higher- 40 - 50 W in ClassA can be a lot.
Cheers
Dirk
Hi Dirk, the 6-24 axo die crossover board has arrived, and next week I will start assembling the components.
I have some doubts whether I should buy a finished sub or build my own?
I see a model Klipsh r- 121sw 12 inch woofer but I have some doubts about class D amplification.
Another choice is to self-build a 12-inch subwoofer, but closed or reflex enclosure? I have a 120 watts class AB amp that I could use, but I have my doubts.
I go out of the pre amp and into the 6-24 AXO I go out with frequencies above 100 HZ into the planar amp and in with frequencies below 100 HZ into the sub amp. The outputs are stereo the sub works in mono, then does one have to consider phase rotation? If yes I have no idea how to do phase rotation . I think I will do both , buy one ( Klipsh r- 121sw or similar ) and build one so I can compare them .
How did you solve the switch from stereo to mono on your DIY sub? Keep in mind that I would like to opt for choices without compromising sound quality.
Thank you for your kind reply and for any experiences you would like to share. Enjoy your music.
I have some doubts whether I should buy a finished sub or build my own?
I see a model Klipsh r- 121sw 12 inch woofer but I have some doubts about class D amplification.
Another choice is to self-build a 12-inch subwoofer, but closed or reflex enclosure? I have a 120 watts class AB amp that I could use, but I have my doubts.
I go out of the pre amp and into the 6-24 AXO I go out with frequencies above 100 HZ into the planar amp and in with frequencies below 100 HZ into the sub amp. The outputs are stereo the sub works in mono, then does one have to consider phase rotation? If yes I have no idea how to do phase rotation . I think I will do both , buy one ( Klipsh r- 121sw or similar ) and build one so I can compare them .
How did you solve the switch from stereo to mono on your DIY sub? Keep in mind that I would like to opt for choices without compromising sound quality.
Thank you for your kind reply and for any experiences you would like to share. Enjoy your music.
Hello giubos,
transferring a stereosignal to a monosignal can be done in a few different ways - but I don't know one without any compromise.
The most simple is a passive solution looking like this:
The second solution coming to my mind is active - a summing amplifier after stereo - sub - outof the AXO. But most often realised with opamps.
Could also be realised with discrete parts like the J113 - JFets used in the 6-24AXO.
The third solution: audio-transformer after the stereo-sub-out of the AXO 6-24
The fourth solution: and perhaps the most pleasant one for you? You want to build a subwoofer - buy a bass - driver / chassis with 2 voicecoils.
You would use your sub-out from the AXO6-24 in stereo to the amplifier (sub/bass - channel). The output from your poweramp goes in stereo to the subwoofer-chasssis with 2 voicecoils. Left channel to voice coil1 / right channel to voice coil2 of the subwoofer.
One chassis with dualvoicecoil I know very well is from INTERTECHNIK the MDS12DVC.
A 12 inch woofer with double voice coil (DVC). Check the internet. You will find many infos and possible configurations (Bassreflex, closed cabinet,...).
But there are other bass drivers with double voice coils on the market. I have used this one a few times. For subwoofers at home and car-stereo with
fantastic results. I don't know if it is still in production, but you can still find some.
Cheers
Dirk
transferring a stereosignal to a monosignal can be done in a few different ways - but I don't know one without any compromise.
The most simple is a passive solution looking like this:
The second solution coming to my mind is active - a summing amplifier after stereo - sub - outof the AXO. But most often realised with opamps.
Could also be realised with discrete parts like the J113 - JFets used in the 6-24AXO.
The third solution: audio-transformer after the stereo-sub-out of the AXO 6-24
The fourth solution: and perhaps the most pleasant one for you? You want to build a subwoofer - buy a bass - driver / chassis with 2 voicecoils.
You would use your sub-out from the AXO6-24 in stereo to the amplifier (sub/bass - channel). The output from your poweramp goes in stereo to the subwoofer-chasssis with 2 voicecoils. Left channel to voice coil1 / right channel to voice coil2 of the subwoofer.
One chassis with dualvoicecoil I know very well is from INTERTECHNIK the MDS12DVC.
A 12 inch woofer with double voice coil (DVC). Check the internet. You will find many infos and possible configurations (Bassreflex, closed cabinet,...).
But there are other bass drivers with double voice coils on the market. I have used this one a few times. For subwoofers at home and car-stereo with
fantastic results. I don't know if it is still in production, but you can still find some.
Cheers
Dirk
One possibiity to get the MDS12DVC:
https://www.hifisound.de/de/Lautspr...Tieftoener/Gradient-MDS-12-DVC-2-X-4-OHM.html
Cheers
Dirk
https://www.hifisound.de/de/Lautspr...Tieftoener/Gradient-MDS-12-DVC-2-X-4-OHM.html
Cheers
Dirk
Also a double voice coil bass - and in my opinion one of the ten best 8inch (20cm diameter) woofers (for hifi) - still today. Although the design is
a bit older. Oldie but goldie...
https://www.hifisound.de/de/Lautspr...oener/Visaton-GF-200-2-x-4-OHM-Glasfaser.html
Cheers
Dirk
a bit older. Oldie but goldie...
https://www.hifisound.de/de/Lautspr...oener/Visaton-GF-200-2-x-4-OHM-Glasfaser.html
Cheers
Dirk
Thanks Dirk,
the two channels can influence the quality of the emission, as
that at certain times there may be two signals in the coils that
would tend to push the membrane in different directions.
At this point it might be better to have two subs, one for the right channel and the other for the left, with the advantage of being able to raise the cutoff frequency a bit and position the subs better because above 100 or 150HZ the bass starts to be directional.
What do you think?
I would like to be ready by the end of May because I have a listening session with a journalist from an audio magazine who will do an article on the system.
Thanks Dirk.
Translated with www.DeepL.com/Translator (free version)
the two channels can influence the quality of the emission, as
that at certain times there may be two signals in the coils that
would tend to push the membrane in different directions.
At this point it might be better to have two subs, one for the right channel and the other for the left, with the advantage of being able to raise the cutoff frequency a bit and position the subs better because above 100 or 150HZ the bass starts to be directional.
What do you think?
I would like to be ready by the end of May because I have a listening session with a journalist from an audio magazine who will do an article on the system.
Thanks Dirk.
Translated with www.DeepL.com/Translator (free version)
Hello giubos,
I always prefer a stereo subwoofer over a mono-solution. If you have the space, money, time to build it - for sure do / build the stereo version.
My absolute preferred crossover-frequency from mainspeakers to subwoofer is below 100Hz. In most situations I ended up at 80 Hz.
Phase isn't that much of a problem. You can move the subwoofer more to the front or the back to compensate for transit time difference.
My experience.
Cheers
Dirk
I always prefer a stereo subwoofer over a mono-solution. If you have the space, money, time to build it - for sure do / build the stereo version.
My absolute preferred crossover-frequency from mainspeakers to subwoofer is below 100Hz. In most situations I ended up at 80 Hz.
Phase isn't that much of a problem. You can move the subwoofer more to the front or the back to compensate for transit time difference.
My experience.
Cheers
Dirk
Hi Dirk,
If we could use the 6-24 cross to come out on the low frequencies directly in mono it would be perfect.
Do you know if anyone has done that?
Thanks Dirk
If we could use the 6-24 cross to come out on the low frequencies directly in mono it would be perfect.
Do you know if anyone has done that?
Thanks Dirk
Hi giubos,
then you would have to go for the solution with an active summing amplifier stage after the sub out.
It is not implemented on Nelson Pass' board (AXO 6-24 pcb), as you know.
And I was never reading about it (remember it) in the thread about the AXO 6-24. Hmmm? 🤔
Cheers
Dirk
then you would have to go for the solution with an active summing amplifier stage after the sub out.
It is not implemented on Nelson Pass' board (AXO 6-24 pcb), as you know.
And I was never reading about it (remember it) in the thread about the AXO 6-24. Hmmm? 🤔
Cheers
Dirk
