The Journey of DIY No-Feedback Class D Amplifier (1) Subtitle: The Motivation and Story Behind It
1. The Motivation and Story Behind It
As electronic engineer and audiophile, I've always dreamed of building an amplifier that would satisfy my own standards. This would not only test my professional knowledge but also be a way to combine my hobby with my work. Though the idea sounds wonderful, the reality was far from easy. Constant interruptions and delays kept pushing back this grand plan.In truth, the delays weren't just because I was busy, but also because I was unsure of what kind of amplifier I wanted to DIY. Common designs on the market—whether tube, BJT, or MOSFET—didn't seem to be the answer I was looking for. After years of indecision, I finally made a choice in the summer of 2020: to build a no-feedback amplifier that would meet the standards of high-end amplifiers. When I made this decision, it even shocked me. As an electronics engineer, my instinct told me it was an almost impossible task. Despite countless thoughts of giving up, my competitive spirit kept bringing me back. I was too curious to know what a no-feedback amplifier would sound like. This question lingered in my mind for a long time. Out of curiosity, I asked ChatGPT, and here's the response I got (Oh, how I wish ChatGPT had been around back then):
Thus began my DIY journey, filled with challenges and joys, to experience the sound of a fully no-feedback amplifier.
Since Bell Labs engineer Harold S. Black introduced the concept of negative feedback in 1927, it quickly gained widespread application in audio amplifiers, achieving great success. For example, the Williamson feedback high-fidelity amplifier, released in 1947, used deep global feedback to significantly reduce distortion, extend frequency response, lower output impedance, and increase damping factor. These improvements made the Williamson amplifier the benchmark for high-fidelity sound systems at the time and a classic cherished by audiophiles today. Most modern amplifiers are still designed with appropriate feedback to improve measurable data.
However, humanity never lacks pioneers who dare to challenge conventions. Many engineers have been working to reduce the amount of feedback, hoping to achieve better sound through shallow feedback. Products from brands like First Watt, Pass Labs, and NAT Audio are successful examples of this approach. These amplifiers remove global feedback and only use local feedback to maintain performance, aiming to reduce the negative impact of global feedback on sound quality. Though their test data may not be perfect, they focus on sound performance and have been well-received in the market.
The success of these products greatly inspired me. I believe that following in the footsteps of earlier engineers can take me further. As an engineer, I value objective data, but as an audiophile, I also think subjective listening experience is crucial. After all, good test data doesn’t always guarantee good sound, and if the sound is pleasant, why worry about perfect data? The quality of an amplifier cannot be entirely defined by one set of parameters, at least not with today’s technology. Objective data gives engineers direction, but subjective listening remains the ultimate measure of an amplifier's quality.
So why did I ultimately choose to challenge myself with the “hell-level” difficulty of a no-feedback amplifier? There’s a small story here. I had a friend who was an audiophile. He once told me that he had listened to amplifiers without global feedback and found the sound more natural, lively, and impactful. He asked if I could build a fully no-feedback amplifier for him to try. At the time, I just smiled and didn’t give it much thought. But his words planted a seed in my mind, which eventually led me to make this decision and explore the mystery myself.
In fact, I wasn’t sure what a no-feedback amplifier would sound like either, or if it would really be as natural and lively as ChatGPT suggested. But debates in technology often have their complexities. Feedback indeed brings many benefits but can also introduce issues like transient intermodulation distortion and dynamic errors caused by feedback delay. Could these distortions negatively affect subjective listening? Perhaps building a no-feedback amplifier with excellent parameters is the best way to answer these questions.
This is the story and motivation behind my DIY no-feedback amplifier, as well as my views on audio technology and subjective evaluation. In the upcoming posts, I’ll share why I chose Class D as the main architecture, and the challenges and results I encountered during simulation, production, and debugging. This DIY journey took four years, and some details may have faded from memory, but I’ll try to consider readers of all backgrounds, using analogies and simplified technical details to help everyone understand. I hope my sharing will bring you some inspiration.
B&W Engineering - incredible
Once in awhile, a product that causes a revelation: some companies really did have outstanding engineering!
This is one of the twelve 6" midranges used in the B&W Sound System for the 2014 Primavera Sound festival (ESP)
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Project engineer and system designer was our very own @truecolour
Various reports by
Pocket Lint
AudioXpress
Igloo Dome
What Hi-Fi
This thread is a measurement/review of the custom 6” drive unit from the system. A few of us were fortunate to acquire this unicorn.
Background- the midrange unit is based on a midrange unit from the CT8LR custom-install system:
The main difference between this and the CT8 driver is that this has a yellow cone, but the similarities include a twin neo magnet, allegedly for symmetric BL(x) and Le(x).
Like the 800 series midranges, it uses the woven Kevlar cone, and dispenses with the traditional surround, instead having a thin foam “Fixed Suspension”. This surround (and spider) affords the cone only a few mm of movement, BUT perhaps because of this, reduces surround radiation distortion
So low, In fact, that the microphone was not able to accurately measure the harmonics:
Sonarworks Xref20 mic:
Incredibly, it has the sensitivity of pro-sound midranges- ie. >95dB/2.83V/1m, yet displays a smooth and extended frequency response to past 10KHz, and mild breakups only occurring past 3KHz.
B&W measurement of individual drivers in CT8 cabinet (blue trace)
When this first arrived to me in Australia, I plopped this driver into an existing test box and took some measurements, including on axis, 15, 30 and 45 degrees off axis.
The sine sweep had a gate of of 5ms (measurements good down to 200Hz) and since it is an 4 ohm nominal driver, I tested with only 2V drive at 1m.
The baffle is 8 1/4” wide; with no roundovers for edge diffraction control- this contributes at least 2dB to the peaking at 4KHz. Also the driver is surface mounted, which causes raggedness of at least +/-1dB anywhere above 2Khz. So this quick/dirty measurement on an unoptimised baffle.
Just add 3dB to figure out the 2.83V sensitivity- that’s almost 100dB /2.83V
Now, to find woofers and tweeters that can keep up!
Edit: One of the Sound System’s tweeter is measured is post #37
Edit 2: April 2025- less fiction
This is one of the twelve 6" midranges used in the B&W Sound System for the 2014 Primavera Sound festival (ESP)
Login to view embedded media
Project engineer and system designer was our very own @truecolour
Various reports by
Pocket Lint
AudioXpress
Igloo Dome
What Hi-Fi
This thread is a measurement/review of the custom 6” drive unit from the system. A few of us were fortunate to acquire this unicorn.
Background- the midrange unit is based on a midrange unit from the CT8LR custom-install system:
The main difference between this and the CT8 driver is that this has a yellow cone, but the similarities include a twin neo magnet, allegedly for symmetric BL(x) and Le(x).
Like the 800 series midranges, it uses the woven Kevlar cone, and dispenses with the traditional surround, instead having a thin foam “Fixed Suspension”. This surround (and spider) affords the cone only a few mm of movement, BUT perhaps because of this, reduces surround radiation distortion
So low, In fact, that the microphone was not able to accurately measure the harmonics:
Sonarworks Xref20 mic:
Incredibly, it has the sensitivity of pro-sound midranges- ie. >95dB/2.83V/1m, yet displays a smooth and extended frequency response to past 10KHz, and mild breakups only occurring past 3KHz.
B&W measurement of individual drivers in CT8 cabinet (blue trace)
When this first arrived to me in Australia, I plopped this driver into an existing test box and took some measurements, including on axis, 15, 30 and 45 degrees off axis.
The sine sweep had a gate of of 5ms (measurements good down to 200Hz) and since it is an 4 ohm nominal driver, I tested with only 2V drive at 1m.
The baffle is 8 1/4” wide; with no roundovers for edge diffraction control- this contributes at least 2dB to the peaking at 4KHz. Also the driver is surface mounted, which causes raggedness of at least +/-1dB anywhere above 2Khz. So this quick/dirty measurement on an unoptimised baffle.
Just add 3dB to figure out the 2.83V sensitivity- that’s almost 100dB /2.83V
Now, to find woofers and tweeters that can keep up!
Edit: One of the Sound System’s tweeter is measured is post #37
Edit 2: April 2025- less fiction
Attachments
Precision Matched Vishay IRFP240 IRFP9240 MOSFETs and IRFP240 MOSFETs
- By rhthatcher
- Swap Meet
- 52 Replies
Attachments
BTSB Buffer - SE/Bal to SE/Bal Buffer GB
- By xrk971
- Group Buys
- 476 Replies
Edit Feb 19, 2024: The BTSB was tested and verified to produce 49Vpp with balanced 4.9Vpp input and balanced output. This means it can easily drive 0dB amps like F4 to clipping levels. The LME49724 datasheet says that it should be able to drive 600ohm loads to 52Vpp with low distortion levels.
Edit Nov 23, 2020: Tips on videos on how to do your own SMT/SMD soldering:
BTSB Buffer - SE/Bal to SE/Bal Buffer GB
Edit Oct 22, 2020: new boards v1.3 for TH and v1.2 for SMT have corrected them layout error and verified to be working properly in all aspects.
Edit Sept. 4, 2020: Stop Press! Please note that there is an error on J36 (the phase is flipped). I am ordering new boards and will send out replacements to folks who have already purchased these. This only afftects one of the SE outputs. If you have no need for the SE output, it doesn't matter. There is a workaround to it here. So sorry about this but it was the one thing I did not check on the verification build.
Edit Aug 18, 2020: Mouser shopping carts for the BOM here. Thanks to Vunce for making these for us!
This is the Best Thing since Sliced Bread (BTSB) Buffer that I will be offering as a GB. It was designed by Jhofland to address a need that I had with my TPA3255 Class D amp which required balanced input with gain. Jhofland designed a prototype that had just balanced output with gain (selectable via jumpers) with either balanced or SE inputs. I tested it out and it works great.
Here was the v1.0 verification prototype that I built:
Member Redjr has already used the prototype version on his very nice TPA3255 amp build here.
I thought that a more universal buffer would provide a choice of either SE/Balanced input and be able to driver SE/Balanced outputs simultaneously. This might be useful for driving a subwoofer amp, for example. The topology uses a state of the art OPA1656 for the input buffers and state of the art LME49724 balanced line drivers and another OPA1656 for the SE outputs. Another OPA1656 provides a bootstrap for the input amp to allow lower distortion drive at higher drive levels close to rail voltages. The power supply is provided with a very low noise Murata isolated DC/DC converter to take 12vdc from a wall-wart to +/-15v using the DC/DC followed with a CLC filter. The BTSB is absolutely silent and adds no noise or coloration. It is very transparent and can be used as a simple signal booster in cases where you need just a little bit of extra bump in the output from your source or existing preamp.
With the ability to accept SE or balanced and to drive SE or balanced, and with your choice of 0dB, 6dB, 14dB, or 20dB gain selectable with a convenient 8-position DIP switch - you will find it an indispensible part of your electronics toolbox kit. I think that you will agree that is may be the best thing since sliced bread...
To see the schematic, please click below. It is too wide of an image to display inline.
Here is the layout:
Here is a photo of the PCB with a Neutrik XLR jack (plain Molex KK terminals are also provided if XLR is not needed):
Here is a measurement of a 1kHz low distortion signal from Victor’s oscillator and 20dB gain from SE to Bal mode and fed to XLR input of my Focusrite - the so-called loop back test with BTSB in the loop. It has noise and distortion below the measurable limit of the Focusrite.
Here is a measurement of the distortion of my TPA3255 w PFFB as driven by the BTSB in SE to Balance out with 20dB gain applied - the THD is lower than the TI factory data at the same condition. The noise baseline is very low at -130dB:
I'll post a photo of the populated board as soon as I get back from vacation.
We can get the GB interest list started. Boards will be 1.6mm thick, 1oz copper, ENIG finish, and green color solder mask. Construction is straight forward as it is mostly through hole except for the opamps. Price is $23 ea for the bare PCB. The BOM cost is about $65. Please see BOM below - I will post a Mouser shopping cart to make ordering easy (soon).
I have received questions about whether or not a version will be provided with the SMT parts pre-installed. Yes, I can do that and the cost for a BTSB with 4x OPA1656 and 2x LM47924 pre-installed will be $69 ea. The 6 opamps cost $21, and I am charging $25 for the SMT soldering service.
Also available in all SMT - 70mm x 70mm. No XLR jack. Same price as TH version (Schematic and BOM here).
Please add your name, desired boards, SMT pre-pop'd Y/N, and country below.
BTSB Buffer GB Interest List:
-----------------------------
Name No. of boards SMT pre-populated (Y/N) Country
Please place a pre-order in my shop if you add your name to the list above.
BTSB Buffer SE/Bal to SE/Bal Buffer | Etsy
There is a new panel mount version of the BTSB that has separate auto-switched RCA inputs. Anytime something is plugged into XLR/TRS, a relay automatically disconnects RCA's. This version also uses OPA1637 for balanced output driver (uses less quiescent current). Mounts directly to rear panel and no mounting standoffs needed. Very compact and conserves chassis real estate on bottom panel. Also reduces flying leads that can pick up noise.
Fit check with 3D print:
Here is panel hole template. Note that the vertical CTC distance below is for the Elecaudio RCA jacks. If you purchase the RCA jacks from my shop or the RTR BTSB Panel Mount then the distance is 7.25mm:
Board dimensions:
BTSB TH v1.3 board dimensions are 100mm wide x 88m high.
BTSB SMT v1.2 board dimensions are 70mm wide x 70mm high.
BTSB Panel Mount SMT v1.2p is 132mm wide x 45mm high.
Edit Nov 23, 2020: Tips on videos on how to do your own SMT/SMD soldering:
BTSB Buffer - SE/Bal to SE/Bal Buffer GB
Edit Oct 22, 2020: new boards v1.3 for TH and v1.2 for SMT have corrected them layout error and verified to be working properly in all aspects.
Edit Sept. 4, 2020: Stop Press! Please note that there is an error on J36 (the phase is flipped). I am ordering new boards and will send out replacements to folks who have already purchased these. This only afftects one of the SE outputs. If you have no need for the SE output, it doesn't matter. There is a workaround to it here. So sorry about this but it was the one thing I did not check on the verification build.
Edit Aug 18, 2020: Mouser shopping carts for the BOM here. Thanks to Vunce for making these for us!
This is the Best Thing since Sliced Bread (BTSB) Buffer that I will be offering as a GB. It was designed by Jhofland to address a need that I had with my TPA3255 Class D amp which required balanced input with gain. Jhofland designed a prototype that had just balanced output with gain (selectable via jumpers) with either balanced or SE inputs. I tested it out and it works great.
Here was the v1.0 verification prototype that I built:
Member Redjr has already used the prototype version on his very nice TPA3255 amp build here.
I thought that a more universal buffer would provide a choice of either SE/Balanced input and be able to driver SE/Balanced outputs simultaneously. This might be useful for driving a subwoofer amp, for example. The topology uses a state of the art OPA1656 for the input buffers and state of the art LME49724 balanced line drivers and another OPA1656 for the SE outputs. Another OPA1656 provides a bootstrap for the input amp to allow lower distortion drive at higher drive levels close to rail voltages. The power supply is provided with a very low noise Murata isolated DC/DC converter to take 12vdc from a wall-wart to +/-15v using the DC/DC followed with a CLC filter. The BTSB is absolutely silent and adds no noise or coloration. It is very transparent and can be used as a simple signal booster in cases where you need just a little bit of extra bump in the output from your source or existing preamp.
With the ability to accept SE or balanced and to drive SE or balanced, and with your choice of 0dB, 6dB, 14dB, or 20dB gain selectable with a convenient 8-position DIP switch - you will find it an indispensible part of your electronics toolbox kit. I think that you will agree that is may be the best thing since sliced bread...
To see the schematic, please click below. It is too wide of an image to display inline.
Here is the layout:
Here is a photo of the PCB with a Neutrik XLR jack (plain Molex KK terminals are also provided if XLR is not needed):
Here is a measurement of a 1kHz low distortion signal from Victor’s oscillator and 20dB gain from SE to Bal mode and fed to XLR input of my Focusrite - the so-called loop back test with BTSB in the loop. It has noise and distortion below the measurable limit of the Focusrite.
Here is a measurement of the distortion of my TPA3255 w PFFB as driven by the BTSB in SE to Balance out with 20dB gain applied - the THD is lower than the TI factory data at the same condition. The noise baseline is very low at -130dB:
I'll post a photo of the populated board as soon as I get back from vacation.
We can get the GB interest list started. Boards will be 1.6mm thick, 1oz copper, ENIG finish, and green color solder mask. Construction is straight forward as it is mostly through hole except for the opamps. Price is $23 ea for the bare PCB. The BOM cost is about $65. Please see BOM below - I will post a Mouser shopping cart to make ordering easy (soon).
I have received questions about whether or not a version will be provided with the SMT parts pre-installed. Yes, I can do that and the cost for a BTSB with 4x OPA1656 and 2x LM47924 pre-installed will be $69 ea. The 6 opamps cost $21, and I am charging $25 for the SMT soldering service.
Also available in all SMT - 70mm x 70mm. No XLR jack. Same price as TH version (Schematic and BOM here).
Please add your name, desired boards, SMT pre-pop'd Y/N, and country below.
BTSB Buffer GB Interest List:
-----------------------------
Name No. of boards SMT pre-populated (Y/N) Country
Please place a pre-order in my shop if you add your name to the list above.
BTSB Buffer SE/Bal to SE/Bal Buffer | Etsy
There is a new panel mount version of the BTSB that has separate auto-switched RCA inputs. Anytime something is plugged into XLR/TRS, a relay automatically disconnects RCA's. This version also uses OPA1637 for balanced output driver (uses less quiescent current). Mounts directly to rear panel and no mounting standoffs needed. Very compact and conserves chassis real estate on bottom panel. Also reduces flying leads that can pick up noise.
Fit check with 3D print:
Here is panel hole template. Note that the vertical CTC distance below is for the Elecaudio RCA jacks. If you purchase the RCA jacks from my shop or the RTR BTSB Panel Mount then the distance is 7.25mm:
Board dimensions:
BTSB TH v1.3 board dimensions are 100mm wide x 88m high.
BTSB SMT v1.2 board dimensions are 70mm wide x 70mm high.
BTSB Panel Mount SMT v1.2p is 132mm wide x 45mm high.
Attachments
Hybrid P3A - Tube differential input stage - ECC88
- By Ciro82
- Tubes / Valves
- 6 Replies
Me and my friend we are thinkering about this:
What do you guys think?
What do you guys think?
Measuring Distortion on the Cheap
- By tomchr
- Equipment & Tools
- 240 Replies
So, you have a burning desire to measure harmonic distortion and other audio parameters but don't have $40k burning a holes in your pockets so you can buy an APx555B. I have news for you: There are cheaper options.
I just finished testing three such options:
Unfortunately ultrasonic noise limits the maximum usable frequency for THD+N vs frequency sweeps on the Scarlett sound cards. Basically the noise renders the 192 kHz sampling rate useless for audio measurements. 96 kHz works fine, but then you're limited to a maximum test frequency of 15 kHz if you want two harmonics (H2 and H3) included in the THD measurement.
I've included the loopback plots below. I have tons more measurements available here: https://neurochrome.com/pages/measuring-distortion-on-the-cheap
I also yap about it here:
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QA403:
Scarlett 2i2 (4th Gen):
Scarlett Solo (3rd Gen):
Tom
I just finished testing three such options:
- QuantAsylum QA403 Audio Analyzer ($600)
- Focusrite Scarlett 2i2, 4th Generation ($200)
- Focusrite Scarlett Solo, 3rd Generation (Refurbished from Focusrite: $80)
Unfortunately ultrasonic noise limits the maximum usable frequency for THD+N vs frequency sweeps on the Scarlett sound cards. Basically the noise renders the 192 kHz sampling rate useless for audio measurements. 96 kHz works fine, but then you're limited to a maximum test frequency of 15 kHz if you want two harmonics (H2 and H3) included in the THD measurement.
I've included the loopback plots below. I have tons more measurements available here: https://neurochrome.com/pages/measuring-distortion-on-the-cheap
I also yap about it here:
Login to view embedded media
QA403:
Scarlett 2i2 (4th Gen):
Scarlett Solo (3rd Gen):
Tom
4P1L Headphone amp
- By VT-52
- Tubes / Valves
- 39 Replies
Hiya,
Been posting some pictures here and there of a new project I have started on, might as well share the whole thing. The idea started in 2018 for a regular amp (speakers), but life happened and I lost track of audio once more. The good thing is that I already have some parts that I can re-use, so in today's thinking "they are free".
Goal:
Tubes:
As I want to tinker with the driver tube a bit, the power supplies will be setup to be universal for a 250V output tube and a 200V driver, current for each tube can be up to 50mA with headroom left.
4P1L will run at 225V/30mA/-19V initially (245V/30mA B+)
6E6P will run at 200V/30mA/-3.4V, 2P29L will be 6mA/-20V, so we have 30mA/-20V as worst cases for the PSU (225V/30mA B+)
As I am betting on the 2P29L, the rest of the info will focus on this combination so as not to have two projects in one.
Supply Chassis:
Signal Chassis:
Iron:
signal path
eTracer loadline on one of the 4P1L I have tested. 1.2W max with 10K.
Step 1: Concept
Step 2: Design PCBs for test setup
Step 3: Test
Step 4: Build chassis and integrated PCBs
Been posting some pictures here and there of a new project I have started on, might as well share the whole thing. The idea started in 2018 for a regular amp (speakers), but life happened and I lost track of audio once more. The good thing is that I already have some parts that I can re-use, so in today's thinking "they are free".
Goal:
- Headphone amplifier, 35 ohms
- Tube, single-ended,1000-1500mW of raw power power
- Daily beater, so no rare tubes, nothing end-game, just good music and a cool looking piece of kit
- Must fit on desk and desk must not collapse
Tubes:
- 4P1L
- 2P29L or 6E6P, might also look at other wee tubes like 6Z49, 6C4S, 5842 etc
As I want to tinker with the driver tube a bit, the power supplies will be setup to be universal for a 250V output tube and a 200V driver, current for each tube can be up to 50mA with headroom left.
4P1L will run at 225V/30mA/-19V initially (245V/30mA B+)
6E6P will run at 200V/30mA/-3.4V, 2P29L will be 6mA/-20V, so we have 30mA/-20V as worst cases for the PSU (225V/30mA B+)
As I am betting on the 2P29L, the rest of the info will focus on this combination so as not to have two projects in one.
Supply Chassis:
- Separate chassis for raw DC supplies to conform to the "must fit on desk" rule
- PCBs
- B+ will be SiC diodes, eChoke and MKP caps
- Filaments with SiC diodes and FW/KW caps
Signal Chassis:
- Filter for DH filaments, then Coleman regulator (current source) for DHTs
- LDO voltage regulator for IHT
- Passive B+ filter with RCRC to tune for both stages
Iron:
- 2x SE OPT 10K/50mA
- 2x Lundahl LL2763AM-40mA interstage
- 2x Toroid 250-210-0-210-250V/330mA, 12V/4A, 12V/4A
signal path
eTracer loadline on one of the 4P1L I have tested. 1.2W max with 10K.
Step 2: Design PCBs for test setup
Step 3: Test
Step 4: Build chassis and integrated PCBs
Attachments
Single to Dual for Headphones Amp
- By franziscko
- Power Supplies
- 6 Replies
Hi, I want to use this schema for an Headphone Amplifier
I have a little 12V transformer and I want to use it.
Wich of these two schemas is ok?
I hope all!!
Thank you!!
I have a little 12V transformer and I want to use it.
Wich of these two schemas is ok?
I hope all!!
Thank you!!
Safely lowering transformer secondary voltage output
- By Hiten
- Power Supplies
- 23 Replies
Hi,
I have a salvaged EI transformer from old boombox. AC voltage details are as follows
My questions are
1) Can I buck the transformer by using one of the isolated secondary winding of lower voltages (A or B) ?
2) What if I discard the center tap of winding B shown in middle (10.7/13 v ) and short two 10.7 v points to use as center tap ? See pic below ... What voltage I will be getting ?
thanks and regards.
I have a salvaged EI transformer from old boombox. AC voltage details are as follows
- 235 AC input at primary
- There are three isolated secondary windings (0-5 v) (13/10.7 -0- 10.7/13 v) (40.7-0-40.7 v)
- The middle one has multiple voltage with common center tap
- I need approx 25-0-25 or any range between 20 to 30 v center taped for example 30-0-30 will also do.
- When I measure secondary voltage by connecting multimeter prongs to output shown in two cyan color dots I get 0-23.7 v
My questions are
1) Can I buck the transformer by using one of the isolated secondary winding of lower voltages (A or B) ?
2) What if I discard the center tap of winding B shown in middle (10.7/13 v ) and short two 10.7 v points to use as center tap ? See pic below ... What voltage I will be getting ?
thanks and regards.
Son of HF - Big Flower
Big Flower - the logical sequel to Horn Flower.
Initial design concept study outcome - the stands in the top picture is what I will end up with.
I have had a lot of fun and learnt much from HF. Some things with them are really desirable and I wanted to see if they could be improved on... and a reason to get a 3D printer 😉
Positives: Great clarity, resolution and timing.
Negatives: Small(er) stage (but very precise), limited low bass and som midrange anomalies (comb filtering) due to that the 4 woofers plays quite high (1400 Hz)
Also the bild quality of the "box" was pretty sketchy and despite the cool "hair", it probably generated quite a lot of diffraction.
So to keep the positives and remedy the negatives, enter the Big Flower.
Same concept but with improvements (finger crossed):
Potential new negatives:
The way they where designed and realised was by 3D modelling, molds printed from PETG and casting in concrete. I like concrete - its a varm, nice and strong material 🙂
It was obvious from the beginning that I could not get a printer to make the horns in one cast so it had to be divided and later glued together. I used Sikaflex 291 for this as it had proven very stable and strong when I built my concrete baffle Line Source. All drives were glued to the concrete and still sits there safely.
I did some simulation on speaker level for the Horn FLower which gave some hints that it could work and I think the result mimic'd the simulations quite well. Therefore I didn't do any for the BF because I don't think it is needed - concept works and I feel the new dimensioning can only be better. And then there is CamillaDSP 🙂
Recipe (for a pair):
So these will be prototypes and have a number of known "errors" already. They where identified during the path of design, both in modelling, casting and dry assembly but half way in I decided to go ahead with these "less perfect" aspects as I realised that it will take one round before I get them "perfect" (never!) anyways.
So what are these problems:
- It was harder than I could imagine to make a mold for a 60 degres part when it came to rotate a profile, make 6 of them and assemble them to a full circle unit. Sketchup could not do it. I got a plugin that was better but then I made som assumptions about how to get some room for the glue which I overestimated and got 5mm instead of 1. Next time, calculate please! 🙂 But I didn't find out until I had made 5 and then I decided to continue anyways.
- Perhaps I have made the concrete goods a little to thick - they have been called tanker stoppers 🙂 and they will be heavy - 40kg+ - a challenge for me to handle. Better have some help during first trials.
- and several minor improvements...
To date, I have all components ready to be assembled except the stands but they are waiting order confirmation.
I will continue posting about the assembly process, measuring and dialling in.
Tnx for reading - comments welcome.
//
Initial design concept study outcome - the stands in the top picture is what I will end up with.
I have had a lot of fun and learnt much from HF. Some things with them are really desirable and I wanted to see if they could be improved on... and a reason to get a 3D printer 😉
Positives: Great clarity, resolution and timing.
Negatives: Small(er) stage (but very precise), limited low bass and som midrange anomalies (comb filtering) due to that the 4 woofers plays quite high (1400 Hz)
Also the bild quality of the "box" was pretty sketchy and despite the cool "hair", it probably generated quite a lot of diffraction.
So to keep the positives and remedy the negatives, enter the Big Flower.
Same concept but with improvements (finger crossed):
- 260mm diameter horn -> 520mm
- 4pcs of 4" bass driver -> 6pcs of 5,5
- XO@1400 -> 800 (hopefully, 900/1k still ok)
- Larger volume per driver - > improved lows
- ATH G2 inspired horn at full width should decrease diffraction
- Lower XO should mean less LF drivers c-c distance interference
- Thanks to bass driver placement and stands/mount design, the LF drivers will be much closer to wall and with less c-c despite being larger,
Potential new negatives:
- Only one cavity so now the actual horn is a pressurised surface of the closed/infinite baffle - vibration?
- Using a 1,4" CD instead of a 1" might have impact on top octave
- Increased depth (5cm) gives a longer distance between LF drivers and horn mouth... integration...
- Heavy
The way they where designed and realised was by 3D modelling, molds printed from PETG and casting in concrete. I like concrete - its a varm, nice and strong material 🙂
It was obvious from the beginning that I could not get a printer to make the horns in one cast so it had to be divided and later glued together. I used Sikaflex 291 for this as it had proven very stable and strong when I built my concrete baffle Line Source. All drives were glued to the concrete and still sits there safely.
I did some simulation on speaker level for the Horn FLower which gave some hints that it could work and I think the result mimic'd the simulations quite well. Therefore I didn't do any for the BF because I don't think it is needed - concept works and I feel the new dimensioning can only be better. And then there is CamillaDSP 🙂
Recipe (for a pair):
- Qidi Q1 Pro
- PETG 4-5 rolls (quite some trails, mistakes and re-thinking done - 3rd time a charm...)
- 2x HF SB ROSSO-65CDN-T
- 12x LF SB15nac30-4
- 3,5 x 20kg bags of fibre reinforced floor levelling concrete: Weberflow 120 Reno DR
- 2 tubes of Sikaflex 291
- Div metal parts for the hanger force distribution box
- Rubber mat for horn/basket gasket
- 2x stands out of iron and concrete (of course! 😉)
- 1 pcs of 1977837 ATH A520G2 from Cults3D - even if I wasn't planning to print this exact horn I wanted to contribute to @mabat fantastic project and products. The profile was modified and simulated in ATH/VACS to give a bit wider dispersion.
- Dedicated electronic in one box - 230V in, wifi/eth and 2 pairs / ch of cabling. TBD...
So these will be prototypes and have a number of known "errors" already. They where identified during the path of design, both in modelling, casting and dry assembly but half way in I decided to go ahead with these "less perfect" aspects as I realised that it will take one round before I get them "perfect" (never!) anyways.
So what are these problems:
- It was harder than I could imagine to make a mold for a 60 degres part when it came to rotate a profile, make 6 of them and assemble them to a full circle unit. Sketchup could not do it. I got a plugin that was better but then I made som assumptions about how to get some room for the glue which I overestimated and got 5mm instead of 1. Next time, calculate please! 🙂 But I didn't find out until I had made 5 and then I decided to continue anyways.
- Perhaps I have made the concrete goods a little to thick - they have been called tanker stoppers 🙂 and they will be heavy - 40kg+ - a challenge for me to handle. Better have some help during first trials.
- and several minor improvements...
To date, I have all components ready to be assembled except the stands but they are waiting order confirmation.
I will continue posting about the assembly process, measuring and dialling in.
Tnx for reading - comments welcome.
//
Attachments
Looking for more gain from my tubelab SE
- By dch53
- Tubes / Valves
- 52 Replies
Hi. The plan for my tubelab SE was to fill the role of HF amp in my 3-way tri-amped system. The amp sounds great but unfortunately, the gain is 7.5dB less than my LF and MF amps.
Rather than continuing to sacrifice 7.5dB of gain in the LF and MF in my crossover, I’ve been looking at ways of increasing the gain of the tubelab SE.
Any alternative needs to be a single 9-pin noval tube so I don’t have to go changing the metal work.
I’ve done some modelling in LTSpice with a 12AX7 running at 1mA, parallel 12AX7s with 1mA each, and with the 12AX7s configured as a mu follower. Ignore for now that 1mA would require a different CCS.
Here’s the gains and distortions for 0.1W out and 1W out.
According to the simulation at least, the 12AX7 mu follower looks to be a good option, apart from the upper stage needing heater elevation.
Is there anything I'm missing? As a high-transconductance tube, I suspect the 5842 was used in the first stage for good reason.
Any other suggestions?
Thanks!
Rather than continuing to sacrifice 7.5dB of gain in the LF and MF in my crossover, I’ve been looking at ways of increasing the gain of the tubelab SE.
Any alternative needs to be a single 9-pin noval tube so I don’t have to go changing the metal work.
I’ve done some modelling in LTSpice with a 12AX7 running at 1mA, parallel 12AX7s with 1mA each, and with the 12AX7s configured as a mu follower. Ignore for now that 1mA would require a different CCS.
Here’s the gains and distortions for 0.1W out and 1W out.
According to the simulation at least, the 12AX7 mu follower looks to be a good option, apart from the upper stage needing heater elevation.
Is there anything I'm missing? As a high-transconductance tube, I suspect the 5842 was used in the first stage for good reason.
Any other suggestions?
Thanks!
Panasonic RAMSA WP9110e repair
- By Andz
- Solid State
- 7 Replies
I have a Panasonic RAMSA 9110e amplifier that came into my possesion some time ago. As far as I can tell channel B functions normally. Channel A however does not. When channel A is connected to a speaker there is noise. Sounds kind of like white noise, but grainy and not quite as dense in nature if that makes sense. Unfortunately I don't have an oscilloscope to see the waveform of it.
I found a video where somebody else had a Ramsa with a channel A problem. Turned out that corrosive glue had done a number on a component or two.
Like the Ramsa in the video mine also had glue that didn’t look all that great so I pulled the 3 caps with glue under them. Came out real easy. 😅
I've cleaned off the glue now. Some of the glue was on diode legs so I checked the diodes with a multi-meter, but they were fine.
While I was at it I checked the 3 caps that I pulled and they read C120 - 460uf (100V, 470uf spec.), C121 - 460uf (100V, 470uf spec.) and C116 - 550uf(10V, 470uf spec.). The first two are pretty close to spec. Not sure what to think about the 10V one. 470 * 1.2 = 564. I suppose if it is a part with a +/-20% or so manufacturing tolerance and serves it’s purpose in the circuit then it’s fine too. But what is the manufacturing tolerance of an electrolytic capacitor anyway? I googled that and apparently it is typically 20% (source). Same source says that capacitance drifts over time. Would you change this cap for one closer to spec?
Small components around big caps with the glue aside what looked suspect was IC101 - MC-8134.
It’s outer shell had some crystals on it. I cleaned them off with some toilet paper and now it visually looks the same as the IC below it. No holes on it, but the crystals must have come from the inside of it?
I’ve turned the amplifier on and played some music with it 2 times before disassembly:
1)The first time the noise disappeared for a while and then reappeared when I turned it up.
2)The second time the noise was there from the start and followed the level of how high I turned up the amp.
If the noise gets amplified based on how high up the amplifier is turned, then it must be coming from somewhere early in the signal path before attenuation. Thinking this I traced the early signal path from signal input to attenuation.
And what do you know? IC101 or MC8134 sits between the two. (page 31, service manual WP9110c, download link) Haven't seen a difference between the WP9110e I have and the WP9110c service manual yet, btw.
I’ve not seen a part like this before and have only some basic knowledge of how some of the stuff in electronics works. Would you think that IC101 is probably damaged? What was that crystal formation on it? What happened to it?
I wasn’t able to find information on what MC-8134 does so I turned to my last resort - ChatGPT. This was the answer I got: “It functions as a voltage-controlled amplifier (VCA), which allows for adjustable gain control in audio signal paths. This IC is typically employed to manage audio signal levels dynamically, providing features such as automatic volume adjustments, noise gating, or signal mixing in professional audio equipment.” ChatGTP couldn't provide a source, said something like answer derived from general knowledge, but it seems like it might be an accurate one.
Not much else jumps out at me on these boards. There is some brown stuff on the undersides of the boards - old flux residue? (see the 3 images attached to this post) If not IC101 what else could be the culprit?
I found a video where somebody else had a Ramsa with a channel A problem. Turned out that corrosive glue had done a number on a component or two.
Like the Ramsa in the video mine also had glue that didn’t look all that great so I pulled the 3 caps with glue under them. Came out real easy. 😅
I've cleaned off the glue now. Some of the glue was on diode legs so I checked the diodes with a multi-meter, but they were fine.
While I was at it I checked the 3 caps that I pulled and they read C120 - 460uf (100V, 470uf spec.), C121 - 460uf (100V, 470uf spec.) and C116 - 550uf(10V, 470uf spec.). The first two are pretty close to spec. Not sure what to think about the 10V one. 470 * 1.2 = 564. I suppose if it is a part with a +/-20% or so manufacturing tolerance and serves it’s purpose in the circuit then it’s fine too. But what is the manufacturing tolerance of an electrolytic capacitor anyway? I googled that and apparently it is typically 20% (source). Same source says that capacitance drifts over time. Would you change this cap for one closer to spec?
Small components around big caps with the glue aside what looked suspect was IC101 - MC-8134.
It’s outer shell had some crystals on it. I cleaned them off with some toilet paper and now it visually looks the same as the IC below it. No holes on it, but the crystals must have come from the inside of it?
I’ve turned the amplifier on and played some music with it 2 times before disassembly:
1)The first time the noise disappeared for a while and then reappeared when I turned it up.
2)The second time the noise was there from the start and followed the level of how high I turned up the amp.
If the noise gets amplified based on how high up the amplifier is turned, then it must be coming from somewhere early in the signal path before attenuation. Thinking this I traced the early signal path from signal input to attenuation.
And what do you know? IC101 or MC8134 sits between the two. (page 31, service manual WP9110c, download link) Haven't seen a difference between the WP9110e I have and the WP9110c service manual yet, btw.
I’ve not seen a part like this before and have only some basic knowledge of how some of the stuff in electronics works. Would you think that IC101 is probably damaged? What was that crystal formation on it? What happened to it?
I wasn’t able to find information on what MC-8134 does so I turned to my last resort - ChatGPT. This was the answer I got: “It functions as a voltage-controlled amplifier (VCA), which allows for adjustable gain control in audio signal paths. This IC is typically employed to manage audio signal levels dynamically, providing features such as automatic volume adjustments, noise gating, or signal mixing in professional audio equipment.” ChatGTP couldn't provide a source, said something like answer derived from general knowledge, but it seems like it might be an accurate one.
Not much else jumps out at me on these boards. There is some brown stuff on the undersides of the boards - old flux residue? (see the 3 images attached to this post) If not IC101 what else could be the culprit?
Attachments
Fosi ZD3 with Burson Audio V7vivid pro dual and a lead-gel battery as power supply
- Digital Line Level
- 113 Replies
I was absolutely surprised by how the sound changed for the better. The Fosi Audio ZD3 plays like a top-class DAC.
Mini current dumping
- By stigigemla
- Solid State
- 9 Replies
I got an idea that i can´t get loose.
What if we apply current dumping to reduce crossover distortion in an ordinary amplifier.
With an internal feedback of 850 ohms it puts some considerations of the input stage but that can be a later discussion.
Has someone seen a similar idea?
What if we apply current dumping to reduce crossover distortion in an ordinary amplifier.
With an internal feedback of 850 ohms it puts some considerations of the input stage but that can be a later discussion.
Has someone seen a similar idea?
Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 KHz
- By soekris
- Vendor's Bazaar
- 11053 Replies
Attachments
Case for Discussion - Would a Single driver Manifold/MTB be better than Tapped Horn?
- By LORDSANSUI
- Subwoofers
- 263 Replies
Attachments
Desktop remote interface for Exogal Comet Plus DAC
- By MichRT
- Digital Line Level
- 11 Replies
Hi!
After trying a handful of DACs, I found love with the Exogal Comet Plus. However, it's user interface.... barely exists. It has a small silver LCD screen that can be a bit difficult to read and is primarily controlled via a BT remote or a depreciated app (Android 9 or lower only). Either remote option can be unreliable at times, so I set out to create a better solution.
My idea was to use an Arduino to directly send the remote commands, removing the need for wireless shenanigans, or to use a Raspberry Pi to operate the DAC from a web portal. I probed the DAC Bluetooth chip output but hit a dead end. Thanks to Bob (from Exogal) backing up some dealer info, there is enough documentation to use the TTL serial port on the back for firmware updates. Huge help and starting point. I reached out to Jeff (also from Exogal) who was immensely helpful as well, and helped me get the ball rolling.
Turns out you can control the DAC via the serial port! Using a USB-to-serial adapter cable, I wrote an app that interfaces with Comet! Written in Python since it’s what I’m familiar with. It’s a simple button-based GUI app that currently allows you to select which COM port to use, power on/off, select input and output, mute/half-mute/unmute, increase/decrease volume, or enter a specific volume value. All through the desktop app!
But I want hardware. Ran out of pro micros so I grabbed a few $5 Raspberry Pi Pico micro controller boards to try. MircoPython is great!
Login to view embedded media Login to view embedded media Login to view embedded media So far I've got most of the code sorted between a rotary encoder and a display. More work to be done but progress feels good. I plan to use 2x of those displays since I have a few already: 1x for big font Input/Output/Power, the other for Volume/Mute. Next up is to add an IR receiver to handle desktop volume adjustment and living room IR remote use.
Huge thanks to Jeff, Bob, and others for helping keep this DAC alive and well. Not sure how many people care about this, but I'd like to share it with those that do. Been waiting on solutions like this for a long while - long enough to try to do it myself. Thanks!
ESP Project 97 preamp scratchy volume pot noise
- By delverboy
- Analog Line Level
- 5 Replies
I was told this design could cause scratchiness in the pot because of loading and after about 4 months of use it seems that may be the case.
I'm seeking advice on two changes I was considering.
Replace the conductive plastic Alps RK27 (from Ebay so probably a knockoff) with this Vishay cermet, and swapping out the LM4562 with a FET input OPA2134 to reduce the pot load. I know an OPA1642 would be a better choice but it's not available in DIP8.
Output stage shown.
VR4 is 50K so R112/212 is 6k8 and R113/213 is 15k, per Rod's instructions.
I'm seeking advice on two changes I was considering.
Replace the conductive plastic Alps RK27 (from Ebay so probably a knockoff) with this Vishay cermet, and swapping out the LM4562 with a FET input OPA2134 to reduce the pot load. I know an OPA1642 would be a better choice but it's not available in DIP8.
Output stage shown.
VR4 is 50K so R112/212 is 6k8 and R113/213 is 15k, per Rod's instructions.
Lowther's New Premium Range
- By ghemml
- Full Range
- 77 Replies
Just got them delivered from the UK. Doing up a Lowther Acousta Enclosure for them pretty soon
Introducing "KRONOS" a vintage inspired 2-Way.
- By zeltergiest
- Multi-Way
- 17 Replies
Hello everyone!
I've recently finished my vintage inspired 2-way design and figured I'd share the journey here for any fellow members who may be interested in the concept or even building it for their self.
Soooo. Let's see it! What is it? Kronos is a sealed 2-way design utilizing the SEAS A26RE4 10inch Woofer and the Visaton FRS 5x-8 2inch in a WG.
Wait, isn't that Visaton driver a full range? Isn't this more of a "WAW" design? Yes, the Visaton is in fact a full range driver but it's actually being utilized as a tweeter in this design. It's mounted in the Visaton WG and integrates perfectly here with the SEAS woofer.
Isn't there already a similar design for this woofer? The A26? Yes, there is. However the tweeter for that design is rather pricey at $350+ each, while the cost here is $14 for each driver and around $19 for each WG currently on Parts Express. (Other options available as well, see below)
Okay okay, enough with the Q&A, let's get into how this came about and details of the design.
Introduction:
The Kronos speaker build was born from a sense of nostalgia—rooted in childhood memories of sitting in front of my dad’s hi-fi system, mesmerized by the towering loudspeakers that filled the room with sound. Those classic designs, with their large woofers and cone tweeters, left a lasting impression. They had a presence—both visually and sonically—that felt larger than life. With Kronos, I set out to pay homage to that era and those experiences, blending the soul of vintage loudspeakers with the clarity and control of modern design. It’s a tribute to the sound that sparked a lifelong passion.
Driver Selection:
To bring the Kronos concept to life, I carefully selected a driver lineup that reflects both the spirit of vintage design and the performance of modern components. For the low end, I chose the SEAS A26RE4, a 10" paper-cone woofer known for its rich tone, effortless bass, and smooth upper response. It’s a direct nod to the classic wideband woofers of the past—capable of anchoring the system with warmth and authority.
For the top end, I went with a more unconventional approach: the Visaton FRS5X, a small full-range cone driver, paired with the Visaton WG 148 R round waveguide. This combination offers a controlled dispersion and a pleasantly natural tone that echoes the voicing of vintage paper cone tweeters, but with improved focus and clarity. To mount the FRS5X, I simply centered it on the waveguide and drilled my own holes—an easy but effective way to create a tweeter solution that stays true to the DIY spirit and captures the character of old-school designs.
Worth noting: With the rise of 3D printing and modern fabrication techniques, custom waveguides for drivers like the Visaton FRS5X are now readily available. For those looking for a more refined or drop-in solution, Heissmann Acoustics offers a purpose-built 3D-printed waveguide specifically designed for the FRS5X. It's a great option for builders who want to simplify the mounting process while maintaining the same compact format and controlled directivity.
Enclosure Details:
The SEAS A26RE4 woofer is housed in an approximately 85-liter (about 3.0 ft³) sealed enclosure, giving it ample volume to breathe and deliver deep, full-bodied bass with natural roll-off—true to the character of classic hi-fi systems. This generous internal volume helps the woofer operate efficiently without excessive low-end boom, maintaining a balanced and effortless presentation.
The Visaton FRS5X is isolated in its own 1-liter (0.035 ft³) sealed chamber. This small compartment ensures that the mid/tweeter remains unaffected by pressure changes from the woofer, allowing it to perform cleanly and consistently.
Throughout the cabinet, adequate internal bracing was incorporated to minimize panel resonance and structural flexing. The result is a rigid and acoustically inert enclosure that supports clean, undistorted output even at higher playback levels.
Crossover Details:
The Kronos crossover began as a theoretical layout, designed with target values based on driver behavior and desired voicing. From there, it was refined entirely by ear, with countless hours of listening and adjustment until the final values locked into place. This process allowed the system to reach a balance that felt natural, dynamic, and emotionally engaging—true to the character I set out to achieve.
The SEAS A26RE4 woofer, a modern version of the W26 used in classic designs like the Dynaco A25, has a naturally smooth roll-off that doesn’t strictly require filtering. That said, I chose to add a small 0.33 mH series inductor to gently tame the upper midrange, making the speaker more forgiving and enjoyable at higher volumes—reducing the risk of harshness or “shouting” without robbing it of presence.
For the FRS5X tweeter, mounted in a waveguide, no series resistor was needed. The waveguide not only improves sensitivity and dispersion control but also helps the FRS5X blend naturally with the woofer. Without the waveguide, I would have added around 1 ohm of series resistance to balance its output. The high-pass network is essentially first-order, using a capacitor for the main roll-off. A parallel inductor was added to keep the tweeter’s upper resonance from bleeding through—simple, but effective.
While a textbook solution might call for an RCL (resistor-capacitor-inductor) network for perfect impedance correction, I found that in practice, a single coil did the job just fine. An optional overall impedance compensation network was included for the sake of completeness, but it's more a nice-to-have than a necessity in this build.
In the end, the crossover reflects the spirit of the whole project—minimalist, purposeful, and guided by listening above all else.
CROSSOVER PCB:
To make this project more accessible for others—especially those new to DIY loudspeakers—I went a step further and designed a dedicated PCB for the crossover network. Rather than relying on point-to-point wiring or a perfboard layout, this custom PCB ensures clean, repeatable assembly and proper part spacing, helping reduce the chance of wiring errors and making the build experience more enjoyable.
The board is laid out with component footprints matched to the actual values used in the final design, and it includes clear labeling for easy reference. Whether you're a first-time builder or a seasoned DIYer, this PCB simplifies the process and makes it easier to achieve consistent results.
I’ll be including a download link at the end of this presentation with everything needed to build your own pair of Kronos speakers—including crossover schematics, PCB files, enclosure plans, and additional notes gathered throughout the build.
Finished Speaker:
Here’s a look at the finished Kronos speaker. Aesthetically, I realize this look might not be for everyone—but that was never the goal. I wanted the finish to reflect the spirit of the project: cheap, fun, and bold. The result is something unique, eye-catching, and artistic.
I’ve had a few people ask how I achieved the finish, so here’s a quick breakdown:
It’s not a high-end veneer or mirror-gloss lacquer—but for a fun, rugged speaker with personality, it gets the job done. Cheap, effective, and satisfying to see come together.
Final Measurements:
Below you can see the final measured response of the Kronos design. The results highlight just how well the Visaton FRS5X in a waveguide and the SEAS A26RE4 woofer integrate—especially considering the simplicity of the crossover network.
The response is impressively smooth, with excellent tonal balance and a natural transition between drivers. The waveguide not only improves the FRS5X’s efficiency and dispersion but also allows it to blend seamlessly with the larger woofer, avoiding the typical disconnect you might expect from such different-sized drivers. The minimal crossover does just enough to shape the response where needed, while preserving the raw, engaging character of the drivers.
This measurement validates the listening impressions—a coherent, dynamic speaker that stays true to its vintage inspiration while performing with modern finesse.
Listening Impressions:
The final implementation of the Kronos exceeded my expectations. While I didn’t build these to be the ultimate reference monitor or the “end-all-be-all” speaker, the result is something that sounds exceptionally good—better than I had originally imagined.
The bass performance is particularly impressive, with deep, full extension that's further enhanced by room gain and proper placement. The SEAS woofer really shines here, delivering weight and authority without muddiness.
Tonally, the speaker holds up well across a wide variety of genres. So far, I've enjoyed everything from Rock, Jazz, Pop, Hip-Hop, EDM, to Classical, and the system has handled them all with confidence. The highs are clean without being harsh, mids are clear and natural, and the overall balance feels cohesive and engaging.
Even at very high listening levels, the speaker maintains its composure, with no sense of strain or collapse—perfect for those nights when you just want to crank things up and let loose.
I’ve also had a few friends over to hear them, and the reactions have been consistently surprised and impressed. There’s something satisfying about watching someone sit down with no expectations, and then light up the moment the music starts.
In Conclusion:
The Kronos has accomplished everything it was designed to do—and then some. It’s a speaker that brings together nostalgic inspiration, modern performance, and hands-on DIY fun in one cohesive package. I’m genuinely proud of how it turned out, and I know I’ll be enjoying these speakers for many years to come.
For those interested in diving deeper into the design—or even building a pair yourself—I’ve put together a comprehensive resource link below. This presentation has only scratched the surface, and the download includes detailed plans, crossover files, PCB layout, measurements, and more.
If you have any questions or run into issues, don’t hesitate to reach out. I’m always happy to help fellow builders in any way I can.
Thanks for taking the time to check out my project—I hope it inspires you to build something of your own.
LINK TO KRONOS BUILD PLANS: https://drive.google.com/drive/folders/1Kpa-w3JEGQmEdG6RKKRCQnM0pMenjgjl?usp=sharing
I've recently finished my vintage inspired 2-way design and figured I'd share the journey here for any fellow members who may be interested in the concept or even building it for their self.
Soooo. Let's see it! What is it? Kronos is a sealed 2-way design utilizing the SEAS A26RE4 10inch Woofer and the Visaton FRS 5x-8 2inch in a WG.
Wait, isn't that Visaton driver a full range? Isn't this more of a "WAW" design? Yes, the Visaton is in fact a full range driver but it's actually being utilized as a tweeter in this design. It's mounted in the Visaton WG and integrates perfectly here with the SEAS woofer.
Isn't there already a similar design for this woofer? The A26? Yes, there is. However the tweeter for that design is rather pricey at $350+ each, while the cost here is $14 for each driver and around $19 for each WG currently on Parts Express. (Other options available as well, see below)
Okay okay, enough with the Q&A, let's get into how this came about and details of the design.
Introduction:
The Kronos speaker build was born from a sense of nostalgia—rooted in childhood memories of sitting in front of my dad’s hi-fi system, mesmerized by the towering loudspeakers that filled the room with sound. Those classic designs, with their large woofers and cone tweeters, left a lasting impression. They had a presence—both visually and sonically—that felt larger than life. With Kronos, I set out to pay homage to that era and those experiences, blending the soul of vintage loudspeakers with the clarity and control of modern design. It’s a tribute to the sound that sparked a lifelong passion.
Driver Selection:
To bring the Kronos concept to life, I carefully selected a driver lineup that reflects both the spirit of vintage design and the performance of modern components. For the low end, I chose the SEAS A26RE4, a 10" paper-cone woofer known for its rich tone, effortless bass, and smooth upper response. It’s a direct nod to the classic wideband woofers of the past—capable of anchoring the system with warmth and authority.
For the top end, I went with a more unconventional approach: the Visaton FRS5X, a small full-range cone driver, paired with the Visaton WG 148 R round waveguide. This combination offers a controlled dispersion and a pleasantly natural tone that echoes the voicing of vintage paper cone tweeters, but with improved focus and clarity. To mount the FRS5X, I simply centered it on the waveguide and drilled my own holes—an easy but effective way to create a tweeter solution that stays true to the DIY spirit and captures the character of old-school designs.
Worth noting: With the rise of 3D printing and modern fabrication techniques, custom waveguides for drivers like the Visaton FRS5X are now readily available. For those looking for a more refined or drop-in solution, Heissmann Acoustics offers a purpose-built 3D-printed waveguide specifically designed for the FRS5X. It's a great option for builders who want to simplify the mounting process while maintaining the same compact format and controlled directivity.
Enclosure Details:
The SEAS A26RE4 woofer is housed in an approximately 85-liter (about 3.0 ft³) sealed enclosure, giving it ample volume to breathe and deliver deep, full-bodied bass with natural roll-off—true to the character of classic hi-fi systems. This generous internal volume helps the woofer operate efficiently without excessive low-end boom, maintaining a balanced and effortless presentation.
The Visaton FRS5X is isolated in its own 1-liter (0.035 ft³) sealed chamber. This small compartment ensures that the mid/tweeter remains unaffected by pressure changes from the woofer, allowing it to perform cleanly and consistently.
Throughout the cabinet, adequate internal bracing was incorporated to minimize panel resonance and structural flexing. The result is a rigid and acoustically inert enclosure that supports clean, undistorted output even at higher playback levels.
Crossover Details:
The Kronos crossover began as a theoretical layout, designed with target values based on driver behavior and desired voicing. From there, it was refined entirely by ear, with countless hours of listening and adjustment until the final values locked into place. This process allowed the system to reach a balance that felt natural, dynamic, and emotionally engaging—true to the character I set out to achieve.
The SEAS A26RE4 woofer, a modern version of the W26 used in classic designs like the Dynaco A25, has a naturally smooth roll-off that doesn’t strictly require filtering. That said, I chose to add a small 0.33 mH series inductor to gently tame the upper midrange, making the speaker more forgiving and enjoyable at higher volumes—reducing the risk of harshness or “shouting” without robbing it of presence.
For the FRS5X tweeter, mounted in a waveguide, no series resistor was needed. The waveguide not only improves sensitivity and dispersion control but also helps the FRS5X blend naturally with the woofer. Without the waveguide, I would have added around 1 ohm of series resistance to balance its output. The high-pass network is essentially first-order, using a capacitor for the main roll-off. A parallel inductor was added to keep the tweeter’s upper resonance from bleeding through—simple, but effective.
While a textbook solution might call for an RCL (resistor-capacitor-inductor) network for perfect impedance correction, I found that in practice, a single coil did the job just fine. An optional overall impedance compensation network was included for the sake of completeness, but it's more a nice-to-have than a necessity in this build.
In the end, the crossover reflects the spirit of the whole project—minimalist, purposeful, and guided by listening above all else.
CROSSOVER PCB:
To make this project more accessible for others—especially those new to DIY loudspeakers—I went a step further and designed a dedicated PCB for the crossover network. Rather than relying on point-to-point wiring or a perfboard layout, this custom PCB ensures clean, repeatable assembly and proper part spacing, helping reduce the chance of wiring errors and making the build experience more enjoyable.
The board is laid out with component footprints matched to the actual values used in the final design, and it includes clear labeling for easy reference. Whether you're a first-time builder or a seasoned DIYer, this PCB simplifies the process and makes it easier to achieve consistent results.
I’ll be including a download link at the end of this presentation with everything needed to build your own pair of Kronos speakers—including crossover schematics, PCB files, enclosure plans, and additional notes gathered throughout the build.
Finished Speaker:
Here’s a look at the finished Kronos speaker. Aesthetically, I realize this look might not be for everyone—but that was never the goal. I wanted the finish to reflect the spirit of the project: cheap, fun, and bold. The result is something unique, eye-catching, and artistic.
I’ve had a few people ask how I achieved the finish, so here’s a quick breakdown:
- I started with a roll-on bedliner called "Total Coat" to create a tough, textured surface.
- After that, I applied a Rust-Oleum yellow paint as the main color.
- For added visual interest, I used Rust-Oleum Black Marbling spray, which creates a random web-like texture and gives the surface a more dynamic, artistic feel.
- Finally, I sealed everything with a Rust-Oleum matte clear coat, which helps protect the finish and reduce glare.
It’s not a high-end veneer or mirror-gloss lacquer—but for a fun, rugged speaker with personality, it gets the job done. Cheap, effective, and satisfying to see come together.
Final Measurements:
Below you can see the final measured response of the Kronos design. The results highlight just how well the Visaton FRS5X in a waveguide and the SEAS A26RE4 woofer integrate—especially considering the simplicity of the crossover network.
The response is impressively smooth, with excellent tonal balance and a natural transition between drivers. The waveguide not only improves the FRS5X’s efficiency and dispersion but also allows it to blend seamlessly with the larger woofer, avoiding the typical disconnect you might expect from such different-sized drivers. The minimal crossover does just enough to shape the response where needed, while preserving the raw, engaging character of the drivers.
This measurement validates the listening impressions—a coherent, dynamic speaker that stays true to its vintage inspiration while performing with modern finesse.
Listening Impressions:
The final implementation of the Kronos exceeded my expectations. While I didn’t build these to be the ultimate reference monitor or the “end-all-be-all” speaker, the result is something that sounds exceptionally good—better than I had originally imagined.
The bass performance is particularly impressive, with deep, full extension that's further enhanced by room gain and proper placement. The SEAS woofer really shines here, delivering weight and authority without muddiness.
Tonally, the speaker holds up well across a wide variety of genres. So far, I've enjoyed everything from Rock, Jazz, Pop, Hip-Hop, EDM, to Classical, and the system has handled them all with confidence. The highs are clean without being harsh, mids are clear and natural, and the overall balance feels cohesive and engaging.
Even at very high listening levels, the speaker maintains its composure, with no sense of strain or collapse—perfect for those nights when you just want to crank things up and let loose.
I’ve also had a few friends over to hear them, and the reactions have been consistently surprised and impressed. There’s something satisfying about watching someone sit down with no expectations, and then light up the moment the music starts.
In Conclusion:
The Kronos has accomplished everything it was designed to do—and then some. It’s a speaker that brings together nostalgic inspiration, modern performance, and hands-on DIY fun in one cohesive package. I’m genuinely proud of how it turned out, and I know I’ll be enjoying these speakers for many years to come.
For those interested in diving deeper into the design—or even building a pair yourself—I’ve put together a comprehensive resource link below. This presentation has only scratched the surface, and the download includes detailed plans, crossover files, PCB layout, measurements, and more.
If you have any questions or run into issues, don’t hesitate to reach out. I’m always happy to help fellow builders in any way I can.
Thanks for taking the time to check out my project—I hope it inspires you to build something of your own.
LINK TO KRONOS BUILD PLANS: https://drive.google.com/drive/folders/1Kpa-w3JEGQmEdG6RKKRCQnM0pMenjgjl?usp=sharing
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Attachments
Wide Directivity 2 way compact Speaker T34A Waveguide and Purifi 6.5 Aluminium
I have posted some simulations of the Bliesma T34A in a waveguide designed for wide directivity to very high frequencies, and some renderings of possible cabinet configurations using the Purifi 6.5 Aluminium driver in some other threads.
I am now making a concerted effort to actually build something that I can listen to 🙂
Finding time to finish the CNC I have been building (for a long time already) is proving hard and apart from aesthetics, I can make something simpler in appearance that performs pretty much as well with the already working tools I have. So a basic box with roundovers and a 3D printed removable waveguide will be the starting point.
Something more like this apart from the colour.
In case it is not obvious to anyone, I should mention that Ath from @mabat was used in the design process for the waveguide.
I am now making a concerted effort to actually build something that I can listen to 🙂
Finding time to finish the CNC I have been building (for a long time already) is proving hard and apart from aesthetics, I can make something simpler in appearance that performs pretty much as well with the already working tools I have. So a basic box with roundovers and a 3D printed removable waveguide will be the starting point.
Something more like this apart from the colour.
In case it is not obvious to anyone, I should mention that Ath from @mabat was used in the design process for the waveguide.
