8mm Forum: Eumig S938 Bluetooth

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Posted by Paul Adsett (Member # 25) on September 03, 2019, 02:47 PM:

Well I have now added Bluetooth capability to my Eumig S938 Stereo and I am delighted with the results. I’ve tested it out paired to my Yamaha RX-383 A/V receiver, which has both transmit and receive capability, and the sound is every bit as good as with a wired connection. And I can also pair it to Bluetooth earphones or Bluetooth speakers (which is great for shows in another home or community hall). I think this is a great addition to any projector – just being able to plug in the projector and go, with no wires to hook up is so nice.
For the Eumig 938 I have housed the Bluetooth transmitter in the accessory compartment on the top of the projector, where it fits beautifully(how thoughtful of Eumig!). A 3.5mm plug connects to the transmitter and is run down through a hole in the floor of the plastic accessory compartment through the inside of the projector to the headphone socket on the projector. The transmitter has a built in re-chargeable battery with a life of about 5 hours. It is re-charged via a USB cable running to a USB charger . Phase 2 of this project will be to mount the USB charger inside the projector so it is always charging the battery when the projector is plugged in.

This little transmitter enables pairing with any two devices. There is a blue light on top that flashes while it is pairing and when it connects the light stays a constant blue. Once you have paired to any device you do not have to pair again as the transmitter in the projector will automatically recognize the device.

Posted by Steve Klare (Member # 12) on September 03, 2019, 03:12 PM:

Paul,

What's also nice about this is without a wired connection you can't have a ground loop. (I've been fighting that one for about 20 years now...successfully about nine!)

What's the range of this? I added a second screen downstairs. If I had a wireless connection I'd be able to use my existing audio system just by running some speaker wires.

Posted by Paul Adsett (Member # 25) on September 03, 2019, 03:26 PM:

Range on this MEE CONNECT BLUETOOTH TRANSMITTER is 30ft. Never occurred to me about the elimination of the ground loop Steve, no wonder I hear no hum!

Posted by Steve Klare (Member # 12) on September 03, 2019, 04:11 PM:

30 Feet would actually do pretty well for me!

In a lot of cases the natural projector hum is pretty low compared to ground loop hum. Once you eliminate that the audio is much better.

Ground loops are a natural topic of thought for me. First time I innocently connected a projector directly to an amp, this buzzing base tone came pouring out and sounded throughout the house!

-my wife said "WHAT are you DOING!"

(-apparently learning about ground loops!)

We were out in public last weekend in a place with a PA system. This low hum was filling up the room.

-poked my son in the arm and nodded a little:

"-ground loop!"

(What Film Collecting has done for me!) [Big Grin]

Posted by Ed Gordon (Member # 6952) on September 03, 2019, 05:25 PM:

Paul, Have you noticed any sync issues? I came across this comment on the Best Buy website:

quote:
Bought this to broadcast audio from a portable projector to a bluetooth audio system. It broadcast the audio but there was a large delay so the audio did not sync with the video. Very annoying so I returned it. Sure it would work fine for for music only.

I also found this in an article at B&H Photo:

quote:
For professional applications, a wired connection is still preferable because it will provide incomparably greater flexibility in terms of available music equipment and performance by way of the resolution of your DAC and the power available from your headphone amplifier. Additionally, a standard Bluetooth wireless connection has a latency of more than 150 ms (+/- 50 ms), which poses A/V sync issues when attempting to edit dialogue or mix sound for picture. A wired connection also suffers from latency, but is workable, provided the latency is within 1 frame (about 33 milliseconds). For reference, the threshold of lip-sync detectability according to blind tests conducted by the International Telecommunication Union (ITU) is -125 to +45 milliseconds, and the acceptable lip-sync standard for film is about 22ms in either direction. Bluetooth devices that implement Qualcomm’s aptX low-latency audio codec, combined with the advanced audio distribution profile (A2DP), claims an end-tend latency of approximately 40ms, which is far more usable for watching and possibly working with video.

At the Best Buy website the technical specs mention:

quote:
The adapter uses Bluetooth 4.0 with aptX technology to create low-latency, high-fidelity audio from up to 30 feet away.

The negative review mentioned above was about the same device you seem to have. Perhaps the negative reviewer was broadcasting to a receiver that did not support aptX?

Posted by Paul Adsett (Member # 25) on September 04, 2019, 11:25 PM:

Ed, thanks so much for that great information.Yes I do see some sync issue in the form of audio lag with respect to the picture. I would estimate this to be about 3 frames at 24fps or approximately 125ms. While I notice it only in dialog with close ups, it is not for me a major annoyance. I find the convenience of the wireless signal to be really great for a quick informal show set up, or for blutooth earphone use. Obviously if your film projector is always set up and ready to go you will be using a wired connection and have no interest in Blutooth. My digital projector is permanently mounted and aligned, but my film shows involve putting the projector up on a stand.
I am not sure yet if my Yamaha receiver is aptx , but I doubt it as I do not see it in the specs, although it does specify A2DP. Any further info that you may have to minimize Bluetooth sync issues would be welcomed. I must say again that I find the audio quality to be excellent.

Posted by Osi Osgood (Member # 424) on September 06, 2019, 12:15 PM:

Paul, you are a true credit to the film forums and Super 8 collectors in general!

It's so super cool to take this "old school" tech and bring it up to date!!

Magnifico!!

Posted by Paul Adsett (Member # 25) on September 06, 2019, 07:06 PM:

Thank's so much Osi for those kind words, much appreciated. I know you really like your Eumig 926, and sound-wise it is a great performer, same as the 938. No reason at all that this machine cannot be upgraded with a Bluetooth transmitter. I am loving the convenience of this little gadget. [Smile]

Posted by Mathew James (Member # 4581) on September 06, 2019, 08:34 PM:

Hi Paul, you may be interested in this thread we made a while back, but using the ST1200HD as our test machine just for interests sake:
http://8mmforum.film-tech.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=011077# 000000

I really like the idea of the newer transmitter and capabilities. I still have and use the one i used in that older thread, but i am sure i can get lower latencies with the updated blutooth versions if i switched up... I haven't yet tried this on the new machine since i am still drooling over the machines sound
cheers! [Razz]

maybe once that novelty wears off [Big Grin]

[ September 06, 2019, 11:46 PM: Message edited by: Mathew James ]

Posted by Paul Adsett (Member # 25) on September 06, 2019, 11:41 PM:

Mathew, thanks for the link to that post, I have not seen it before. Good to know that other people like the Bluetooth transmitter for their projectors. So far I am loving wireless on my Eumig 938, and I have tried it out on my GS1200 where it works equally as good. But I do not think that the transmitter can be mounted inside the GS1200 because of its all metal construction which would shield the RF waves, so it would have to sit on the outside, the top rear probably being the best place. The Eumig 938 has an all plastic rear cover which will not block the RF when the transmitter is mounted as shown above.

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