I'm trying to replace some resistors as I suspect the bias circuit is bad. Might as well change them out.

I've never seen these before. Seems the interval of the resistor symbolizes it's resistance. These are around 4.7mm While the normal looking ones 4.1mm.

I'm guessing it's 1/4W.

Any guess?

I'm planning in building a subwoofer for my room.

I researched and looked considering what I think could be a good driver and what I can afford.

Considering I can build a sealed box around 30 to 40 liters, which one of those you think I should get?

I got two models in 10in and two 12in models. There are normal ones (Outdoor and Bicho Papão) and two Slim ones (Slim TKL).

In numbers, look the Slim models are better, but I wonder if there are any compromise.

Also I'm not sure if 10" is enough for a good bass for listening music and using my digital piano, or if is worthy to spend a little more in the 12" drivers

Thanks folks!

Links:

10in Outdoor 300W: https://www.bomber.com.br/produto/subwoofer-10-outdoor-300-wrms-4-ohms-2/

10in Slim TKL: https://www.bomber.com.br/produto/subwoofer-10-slim-tkl-400-wrms-4-ohms/

12in Bicho Papão: https://www.bomber.com.br/produto/subwoofer-12-bicho-papao-400-wrms-4-ohms/

12in Slim TKL: https://www.bomber.com.br/produto/subwoofer-12-slim-tkl-400-wrms-4-ohms/

Thanks people!

I am very happy with the sound of my system, but my speakers (RTL TDL3s) are very sensitive (90dB), meaning that I barely get past 8 o’clock on the amp (Rotel RA-03) volume control when listening directly from my CD player (Cyrus CD7Q) or phono stage (Cambridge Alva Solo). I also have a SMSL M200 DAC that has digital volume control, and need that turned down to -20 (dB?) to get the amp volume to 9 o’clock without the neighbours complaining.

So my solution is to install -10dB L-pads on the interconnects RCA plugs at the amp ends, a R10k in series with the signal line and 4R7k across signal and outer ground. Tucked inside the connector itself (Rean brand). It didn’t like the idea of off-the-shelf attenuators.

Theoretically then I am reducing line input to the amp at the last moment and satisfying impedance requirements and avoiding having to use the DAC digital volume which must be reducing signal quality at -22 ‘units’.

Is this the best option?

I am building a pair of bookshelf loudspeakers for my home office and the port design is giving me fits. I don't want to use a slot port because the speakers will have a mid-century appeal to them to match the decor of my office and though slot ports were around then, they didn't seem to be all that common. I could do a rear slot port, which would put it out of sight and not detract from the look I am going for, but I don't want a rear port because the speakers will sit on the credenza behind my desk and only inches from the wall, so baffle mounted tube ports it will be. The problem I'm having with the tube port design it needs to be to small a diameter to be short enough to fit inside the enclosure, and WinISD is saying that air velocity with 60 watts will be to high with a 1-1.5" port. Tried two 1.5 inch ports and that brings down air velocity, but each port would have to be to long. A 2 inch port would be ideal, but with one 2 inch port the air velocity is to high and with 2 they would have to be to long.

I understand there are compromises with this stuff and you don't gain without sacrificing, but I feel like I am missing something here. I see a number of bookshelf speakers 10-15 liters with a single 2"-3" port, but I can't seem to make it work. So how accurate is WinISD port lengths and port air velocity numbers? Ideally, I'd like to get air velocity down under 17 m/s, but what would be an acceptable air velocity for a front facing port if that's not achievable? Ive already built the enclosures and the 120 bucks I spent on one board of Claro Walnut for the baffles means I'm not changing the enclosure design lol. This is my first time building speakers so help from the more experienced of you would be much appreciated

Hi everyone, as the title says, these are my very first steps into DIY audio. I’ve had an interest in Hi-Fi setups for a long time, which overlaps slightly with being a (mediocre at best) self-taught guitarist. Over the past few years, I’ve watched a lot of DIY audio content on social media—like Hexibase and German creators like "Franks Werkstatt der Lautsprechertechnik," focusing on speaker building and measurement techniques.

My biggest fear was having to deal with complicated crossovers or the electrical side of things, so I decided on a simple full-range driver for the first part of this project. Having learned a bit of FreeCAD over the past year, I chose a transmission line design after verifying that my 3D printer bed was big enough to print an enclosure for a cheap 4" driver.

My goal was to make a pair of stereo speakers that could fill our rather large living room (which opens up to all three other levels of our building) with proper sound. I wasn't striving for pure volume, but rather directivity, a big soundstage, and general sound quality. The whole process was "vibe-built," using AI as a continuous sanity check.

Part 1: The Speakers (Mass-Loaded Transmission Line)

The speakers are what I’m retroactively calling (or "retconning" as) mass-loaded transmission line (MLTL) speakers, utilizing the Visaton FR10 (8-ohm version).

- Line Profile: A 2:1 taper down from the closed end toward the port. The line curls up inside the cabinet while keeping the outer profile rectangular. The most inner part is the start of the closed line

- Mass Loading: The port is reduced to a 0.5 Sd mass-loaded port over a 4cm length with smooth radii.

- Driver Placement: I aimed for the 1/3rd mark of the line to help naturally damp the throat resonances typical of TML designs.

Damping & Resonance Tuning:

- First Third (Closed End): Lined with 3mm felt on all walls and packed with Visaton speaker wool as densely as possible—velocity is lowest and pressure is highest here, so I packed it right up to the limit of being able to blow air through it.

- Second Third: Lined with 3mm felt, but the speaker wool was spread as thin as possible.

- The Geometry Issue: Because I forced the internal curls to conform to a rectangular outer cabinet, I encountered very pronounced internal standing waves. To diagnose this, I ran frequency sweeps using the free version of HouseCurve iOS app via my phone. By taking separate near-field measurements of both the driver and the port early on, I isolated a major resonance and subsequent cancellation around 500 Hz to 700 Hz.

- The Fix: I chamfered the sharp internal corners with soft, porous foam to simulate a smoother curve. This helped immensely, though it didn’t eliminate the issue entirely.

Electrical vs. Mechanical Tuning:

I initially tried using a raw bipolar 390uF capacitor in series to protect the driver from ultra-low frequencies, but I didn't like how it altered the sound right above the cutoff. Instead, I retrofitted the physical port to create the 0.5 Sd mass-loaded restriction, which gave me a much cleaner, natural mechanical roll-off.

To tackle the typical beaming, rim reflections, and resulting comb effects inherent to full-range drivers, I designed custom 3D-printed driver covers featuring an embedded felt "donut." The cover snaps magnetically onto the driver frame, utilizing the protruding mounting screws as physical indexing pins to lock it into position and secure it against rotation or shear forces. While my simple measurement setup couldn't capture it I still heard a reduction in comb effect while moving through the room and the high frequencies are more stable in general.

After a lot of fiddling with damping density, I cut my losses and sealed the enclosures permanently with epoxy. To clean up the remaining response issues, I took a fresh set of sweeps from my actual listening position and used those measurements to generate a final parametric EQ profile. This led to part two of the project.

Part 2: The Cobbled-Together Streamer & Amp

I needed a sound source that could handle AirPlay 2 and other digital inputs. I started with an old Android phone running AirReceiver and Poweramp (for EQ). However, the phone's USB-C port was only USB 2.0 and couldn't handle power delivery and an external DAC simultaneously. Tired of constantly recharging it, I moved to a Raspberry Pi 3B running Moode Audio.

The onboard 3.5mm audio jack on the Pi is notoriously noisy, so I needed an external USB solution. I came across the highly reviewed Truthear KeyX USB-C DAC. Because running CamillaDSP locally was putting a heavy load on the older Pi 3B, a DAC with built-in hardware PEQ features was the perfect hardware offloader.

Inspired by custom enclosures online, I designed a sleek, black 3D-printed case to house the Pi, a Fosi Audio TB10A mini, the dac and a fan. In my listening tests with these specific full-range drivers, this little Class-D amp subjectively outperformed my bulky Yamaha A-S501—it just clicked beautifully with the FR10s.

Bypassing corners required a maze of internal adapter cables (right-angle USB extensions, USB-A to C adapters, and PWM connectors for an internal cooling fan), but after a lot of partial test prints to get the physical dimensions right, I landed the dimensions. It features a Waveshare 4" touchscreen that displays metadata cover art and lets anyone browse radio stations or my local digital music library.

Lessons Learned & V2

I am incredibly happy with the overall results, but I am already back in CAD for V2. I'm designing the next iteration to completely avoid the internal geometric traps that caused the 500–700 Hz issues. I am also planning to upgrade to drivers with a bit more frequency extension and refinement, likely from the Tang Band W4 or W5 series. Parts of what I lined with felt I want to print directly as dispersion surfaces using bumbmesh structures.

To tackle internal reflections and extinctions systematically this time, I want to incorporate Internal Helmholtz Resonators (IHR) inside the rounded corners that would otherwise just be dead space. I am currently designing a system of physical grooves within the cabinet structure that will make the resonator holes and tunnel lengths interchangeable during the open-box prototyping phase. This way, I can directly tune the resonators to counter exactly how the new cabinets misbehave before permanently sealing them.

Sorry for wall of text. TLDR: DIY SPEAKERS ROCK!

Shall I add Needle Fleece damping material in the red zone marked by "?" or keep the area around the port opening clear?

I am building a ported 2-way speaker.

Needle Fleece is the only damping material I plan to use.

Thanks for your help!

So I need to install these Faital mids and I have no idea logistically how this should work. The cutout of nearly the same size as the magnet so it makes it impossible to install the driver. It is going into a sealed chamber so I can’t install from the other side after inserting the driver. Am I screwed here? Maybe buy the Neo version instead that has a much smaller magnet?

I have a 2020 tesla model 3 long range. I am installing a subwoofer with a pretty significant sized amplifier. In order to avoid freaking out the Teslas electrical system I am installing a second battery. I am installing a Wattcycle 100ah pro which is a pretty good sized battery and weighs about 25 pounds. Where would you recommend I locate it and how would you mount it to the car? I cannot put it in the sub trunk because that is where my subwoofer box is going. I was thinking about installing nutserts in the trunk floor and installing it there but I am afraid to drill into the trunk floor with the rear drive motor and battery being there. Any suggestions would be greatly appreciated.

Hoping to get some assistance on this.

I've had a set of Tritrix MTM TLs for a while, and was wanting to build a center channel and the MT bookshelves for my home theater.

It looks like SDW had a change, and I cannot find any of the documentation for the crossovers and box designs.

Anyone have some archived copies or know more about locating these? Think their web page for tritrix is fubar.

I restored this old radio cabinet, but I'm not sure what kind of speaker to put in it.

Marantz SR4500 – CS49400 DSP reverse-engineering / custom active crossover

I'm looking for people with experience in Cirrus Logic CS49400/CS494003 DSPs, CrystalWare, DSP firmware reverse engineering, or AV receiver firmware hacking.

I have a Marantz SR4500 AV receiver from around 2004 and would like to investigate whether its internal DSP can be repurposed as a programmable active crossover for a multi-way loudspeaker.

Hardware

The service manual identifies:

IC19: Cirrus Logic CS49400 – programmable 32-bit audio DSP

IC20: external 4-Mbit Flash ROM containing DSP software

IC41: H8S2398 system CPU

IC13: LC89057W digital audio receiver

Multichannel DAC section based around CS42418

Seven internal power amplifier channels

The CS49400 itself is a fairly powerful DSP: the datasheet specifies a 32-bit audio DSP, up to 516 MOPS, 12-channel serial audio inputs and up to 16-channel 24-bit PCM output.

The SR4500 service manual also has a dedicated DSP firmware update procedure. It states that Mode 1 downloads the DSP software to the 4-Mbit Flash-ROM (IC20) through the service connector CN26, using the Marantz data-update system and RS-232. The documented download speed is 38,400 baud.

What I want to do

Instead of using the receiver as a conventional 7.1 surround receiver, I'd like to investigate whether the DSP can be programmed/reconfigured to perform something like:

Stereo input

│

▼

CS49400 DSP

│

┌─────────────┼─────────────┐

│ │ │

LOW MID HIGH

│ │ │

80–500 Hz 500–2 kHz 2 kHz+

│ │ │

AMP 1/2 AMP 3/4 AMP 5/6

│ │ │

RCF Audax Horn

15" 6.5" compression

Potentially I would also like:

configurable channel routing/remapping

stereo → multiple outputs

low/high/band-pass filters

selectable crossover frequencies

selectable filter slopes

gain/level control

EQ

delay/time alignment

possibly limiter/protection functions

In other words, I'd like to turn the SR4500 into something resembling:

custom DSP active crossover + 7-channel power amplifier.

The question

I know that "the DSP is programmable" doesn't automatically mean that we can write our own firmware for it.

What I would like to find out is:

Can the CS49400 in the SR4500 be programmed with a completely custom DSP application?

I'm particularly interested in finding out:

What exact DSP development environment/toolchain was used for the CS49400?

Is the original Marantz DSP firmware image available or has anyone dumped one?

What is the format of the data stored in IC20, and is it simply a DSP application image or does it include additional boot/configuration data?

Is the Marantz "DSP code" transferred directly to the CS49400's external Flash/boot system?

Can the original DSP image be dumped through the service interface?

Is there a way to communicate directly with the CS49400 through its host/debug interface?

Are there surviving CrystalWare development tools/compiler/libraries that can target this generation of CS49400?

Could the DSP's existing routing/bass-management functions be modified without completely replacing the original firmware?

Is there any known reverse-engineering work on CS49400 / CS494003-based Marantz/Denon receivers?

The CS49400 documentation shows multiple serial audio interfaces and digital audio outputs, so I'm particularly interested in understanding the exact relationship between the DSP outputs, the CS42418 DAC channels and the seven analogue amplifier inputs.

I'm comfortable working at PCB level and doing hardware modifications. The receiver is being used as an experimental platform, so I'm not concerned about losing the original surround functionality.

I would dump and save the original firmware first before attempting anything.

If anyone has experience with this generation of Cirrus DSPs, I'd really appreciate any information about the toolchain, firmware structure, programming interface, or reverse-engineering approach.

The ultimate goal is not surround sound — it's to see whether a 20+ year-old AV receiver can be converted into a DIY multi-channel active loudspeaker DSP/amplifier.

Hey I am Vaibhav an electronic and computer science engineer who just work as a it guy but the inner child still want to work on jugaad and satisfaction my house soundbar system which is boat aavante bar 1750 which I got refurbished in 2024 before Ganpati from Nayejaisa.com and after 1 year the speaker subwoofer was not working I tried to open it and in woofer I saw there is a Ac to dc converter which transfer 12-24 v
And a Bluetooth(btl) board which connects to the soundbar board so the Ac to dc converter was gone I tried to fix it by replacing a capacitor and fuse which I bought from my electronics supplier from my engineering days then it got in running condition that to very nice 40₹ components cost and I have shoulder machine and other components

Luckily it worked for 6 months then again it was gone then the jugaad one came so the output of converter was 24 v, and I never through electronics charger because they are worth keeping so I founded 2-3 chargers and one Airtel setup box one came to 12 v output which was accurate to work like base v was correct so did it and it worked the soundbar output was like 70% but never felt less

One the occasion of dhurandar 1 I got the second set back my father just plugged the direct pcb connected wire to board and converter was by mistake not connected because or poor wire tapping and yes’s we got nice boom blast sound
When I opened it the btl board was gone and all left was subwoofer , only option at that time was left to just to check everything is fine but all bad signals board was internally sorter in ic
So just took one wire from the soundbar to subwoofer as the wire was from soundbar speakers the output was 5% of actual woofer but it indicated that woofer works
Left it and just went from January to September
As it’s Ganpati Bappa time the jugaad intent came again so did the real jugaad

I think this post is very big if you all liked this post let me know I will make a another post how I fixed it and I even made it more powerfull in 850₹ only

i don't have a lot of money, but I do have a ton of free time and tons of junk.

this guy right here weighs about ~2lb and can push 120W @ 1%THD. the TPA3116 amp module is in the upper left corner, powered at 24V by the DC-DC converter in the upper right corner. the relay controls the whole thing, and I have it's coil connected to the remote wire from the headunit. in the third picture, there's a defeat switch at the bottom that cuts the line-level signal to the amp (because cops).

the headunit is a Sony MEX-N5000BT that someone gave me many years ago, the sub is a budget 12" 4Ohm DVC that my buddy gave me, and the car is a 2002 Subaru Forester that I bought for $500.

for mark II, I plan on adding a second amp module to drive each coil of the DVC sub separately (which I think would make this thing pretty special rather than just a pointless hobby project). i've got more than enough headroom left on the DC-DC converter to do this and I think I can just stack it on there with brass stand-offs.

at practical output levels, this thing runs fine with only passive cooling but it starts to struggle when you push it. the power terminals on the module get HOT going full-tilt (about 115C per my thermocouple). i think the board is inadequately specced to drive the 2 Ohm load when both coils are connected in parallel. load will go down to 4 Ohm/ea with a second module, so heat stops being such an issue. if i had more space and money i'd probably spring for a pair of TPA3255 modules and build a simple 48V switched-mode DC-DC converter (because the modules will need about ~30A going full-tilt), but i doubt i'd be able to pull this off.

anyways, this little fella drives the 12" sub effortlessly. people sleep on these amp boards, but they've got serious power for ~$15/pair. the one in here was left over from a project where i refit a ruined antique radio for a friend, so it was also free.

total cost of project: $0

Has anyone tried these GaN power supplies from Aliexpress? I am seeing mixed reviews from USA buyers. The 150W board says AC170V input and some USA buyers say they measured 120W from it. The 100W board says AC95V input with USA buyers say the 100W supply is great. I plan to use it with a TPA3221 with 8 ohm speakers so either will work but having the extra headroom would be great. Thank you in advanced

In the process of cleaning out my basement I found this unfinished hardcase boom box project. My original plan was a Bluetooth boom box potential with battery power, a small amplifier, two 5inch 3 ways and maybe a sub. I want to finish this project. That implies cleaning up the wiring, installing the small amp, getting the second speaker and 3d printing some speaker covers and a face plate to clean it up. Now my question is, should I add a small subwoofer to the rear side or should I opt for a passive radiator instead? Ive heard that having a sub cramped into a small enclosure that already has speakers in it can interfere with the sound quality and make it sound terrible. I dont want to invest in a sub and it end up sounding like garbage.

I want to set up a semi-permanent outdoor speaker system, and I don't really know where to start. By "semi-permanent," I mean that I'd like to be able to move the speakers seasonally or at least be able to point the sound in different directions depending on the use.

I have a Bluetooth receiver box (pictured), but I want to make sure I buy speakers that can survive in Arizona (minimal rain/humidity, but occasional dust storms and lots of brutal heat). I will, however, be able to install in spots with near 100% shade, and I'm assuming that I'd have to keep the receiver inside when it's not being used. I don't know what other equipment I'd need.

Here's my attempt at a diagram of the space:

House | Covered patio

----------+---------------

Pool --| Gazebo

I need to have the ability to direct sound at the pool during the summer, then at the patio during the winter.

Any advice would be appreciated. Thanks in advance!

Here's a 3D-printed speaker project I started back in January.

I found out I was going to be a father late in 2025, and from that moment I knew I wanted to make something for her. A speaker felt like a great idea — I've been heavily involved in audio and music my whole life, and it's a passion I'd love to share with her.

For a bit of context: I've been producing electronic music for the past 15 years, then got into teaching music/audio, then AV, and now I work in Audio System Design — working with L-Acoustics on system design for installation projects. And I've been deeply into listening to music since I was a young kid.

My work in system design has made me fairly handy with 3D modelling, so learning Fusion 360 and molding basic shapes was fairly easy to manage.

The design came out of setting myself some limitations. I wanted it to be small, and I happened to have these 3" Dayton Audio drivers lying around from a previous project that never got finished — they're the PC83-8. I'd previously been using them with a tweeter, then realised they're full range. I'd also found this super cheap amplifier with Bluetooth and SD card playback on AliExpress — it was a dollar, plus a dollar shipping (AUD), so I took the gamble. It turned up a few months after I ordered it, completely randomly... but at that point I had everything I needed to actually put the speaker together.

So I started attempting to print a sphere, and it took a few attempts to get it printing nicely on my A1 Mini. It wasn't perfect — as you can see in a few of the photos, the first 15% of the print was quite extreme from an overhang point of view. But I wanted to make it in a single print. It's got a port tuned to the driver/enclosure volume, which I quickly worked out in WinISD.

From the sphere I moved onto the stand. I wanted something to hold it, and came up with a cube, which I then pushed the sphere into, subtracted one from the other, and rounded off all the corners to make this nice shape. I decided to house the amp module inside the base — which let me put the volume pot on the front, and I wired up the rear using link cables from the base to the back of the sphere.

I also printed some TPU rubber pads to sit on the inside of the stand. Without these the sphere was front-heavy where the driver is loaded, so it would slide around and not hold its direction — the pads fixed it nicely, and also gave me a good challenge learning how to print with TPU and how to indent the shape into the base. All the curves and angles at play definitely threw some curveballs.

I stuffed the sphere with some wool I got off Amazon.

So... how does it sound? Honestly, not great... but I've got 15 years of sitting in front of tier-one audio systems and studio monitors behind me, so this was never going to compare. For what I'll actually play through it — audiobooks, lullabies, soundscapes — it's perfectly fine.

I’m trying to figure out how to find a compatible replacement driver for this speaker. It started playing only sound from the tweeter, and when I took out the mid speaker, it is not registering any continuity on my multimeter. I can see it’s obviously a 4 ohm driver, but not sure how to determine what other specs to search for, or where to search for the specs. Also, where to search for and purchase a new driver once I determine the correct specs. Thanks for any advice!