🛠️🔊 DIY Wireless Speakers: Lossless + low-latency. The HOLY GRAIL!? 🏆✨🤞
Channel: Scott Schiller
Date: 07/01/2023

“Your scientists were so preoccupied with whether they could, they didn't stop to think if they should." -- Dr. Ian Malcom (Jurassic Park)

That line of thinking, of course, does not apply here; I knew I wanted to do this the entire time. 😆 😇 I've detailed the process, just in case you might have been wondering similarly. 😉

ℹ️ OVERVIEW

This is an overview of my project to retrofit a restored pair of legendary loudspeakers from 1982—the Altec Lansing Model 14—to be wireless, self-powered, and mobile. I want classic style, with modern convenience: “Look Ma, no more cables on the floor!“

I don't want to sacrifice quality, either; I want perfect CD-quality audio if possible, and low latency - so that "lip sync" is correct with movies and video.

In this video I summarize my research, my choices for wireless, power supply and amplifiers, possible compromises, and my eventual results. I'm happy to say that this experiment has turned out quite nicely.

🤓 THOUGHTS ON DAC / ADC, “QUALITY” AND BITRATE

I should add, Avantree says "Uncompressed audio quality" on their site; it may not be technically accurate to say "lossless", because your source signal is likely transcoded or converted at least once.

I looked at the internals of the transmitter, but I don't know enough to say if there is a downgrade in audio quality from the SPDIF or 3.5mm line-inputs on the transmitter - e.g., if the ADC is 16-bit but your source is 24-bit digital via SPDIF, I think that would be considered lossy.

I believe the 2.4 GHz wireless chip can do 1 or 2 mbps data transmission rates, so I presume the audio being sent would have to fit within that bandwidth range. Audio CD (44.1 KHz stereo, 16-bit samples) bitrate is 1411 kbps - so I imagine 2 mbps (2000 kbps) bandwidth would suffice for CD-quality audio, uncompressed.

My $.02 is that 16 bits (as in CD audio) sounds great to me, and I think that's at least what is being used here. It's unclear what sort of bitstream is actually being sent over the air, but I think it's good that Avantree say "uncompressed" and don't get into the weeds on whether they use 16 or 24 bits or somewhere in-between for AD/DA conversion and the particulars of wireless transmission. Notwithstanding, it's interesting to think about.

🛒 LINKS TO COMPONENTS MENTIONED

Avantree 2403s - look for 10ms "LL" version, improved from 30ms, in 2023.
https://avantree.com/ca/audiplex-2403s-wireless-transmitter-receiver-set

TalentCell 12V LiFePO4 battery pack (may not be available in US at time of posting?)
https://www.amazon.ca/gp/product/B07YRZYLKV/ref=ppx_od_dt_b_asin_title_s03

Also, consider the less-expensive 3000 mAh version as well. Ditto on US availability.
https://www.amazon.com/TalentCell-Rechargeable-3000mAh-Lithium-External/dp/B01M7Z9Z1N/

Nobsound 100W mono amp:
https://www.amazon.com/gp/product/B07518QZ9B

"Board-only" version, notably cheaper without an enclosure:
https://www.amazon.com/Nobsound-TPA3116D2-Amplifier-Frequency-Channel/dp/B07H339BFP

Fosi Audio ZK-502T: 50W Bluetooth Stereo amp (which I chose not to use for this project):
https://www.amazon.com/dp/B087FWD6C4/
https://fosiaudioshop.com/products/bluetooth-5-0-amplifier-board-2-channel-zk-502t

ADAPTER NOTE: You will also need a DC plug adapter (or a different cable) to connect the TalentCell battery pack's 12V DC5521 (5.5mm x 2.1mm) plug output to the Nobsound amp's 5.5mm x 2.5mm, "DC5525" power receptacle. The TalentCell pack includes a DC5521-to-DC5521 power cable. Close, but not quite.

Ground Loop Isolator (3.5mm):
https://www.amazon.com/s?k=ground+loop+isolator+3.5mm

Banana plugs are optional, since you can use bare wires on the amplifier's speaker posts.

Timeline:

00:00 Altec Lansing Model 14 Speakers
00:11 Intro, Wireless Speaker Demo
00:27 Project Goals, wiring before / after
00:36 A mobile living room: "Everything on wheels"
01:02 VIP Guest approval. 🐕😂
01:10 Trade-offs: Cost, performance, features
01:32 Wireless “Holy Grail“ Requirements
01:48 Avantree Audiplex 2043s
02:11 Avantree Transmitter “teardown” - guessing at components, DAC + ADC
02:56 “Inexpensive amplifiers on Amazon.“
03:01 Douk Audio 100W mono amp
03:33 Fosi Audio 50W + Bluetooth (board / kit)
03:59 TalentCell 12V LiFePo4 Battery Pack: LF4100
04:30 TalentCell 12V Li-ion Battery Pack 
04:50 Dolly / Caddy / Cart-style Wheels
05:04 Connecting components, side-effects, and fixes
05:36 Line noise, connecting wireless RX to power pack
06:04 Workaround: Audio Ground Loop Isolator
06:15 Stereo-to-mono (L/R) splitter cable
06:25 “Finished” wiring, one minor detail
06:38 Wrap-up
07:02 “Walk?” 🐕😂