L1 Model II

Let's talk about the L1® Portable Line Array Systems

Using proprietary Bose® technology, L1 systems combine  PA and monitors into a single, highly portable unit. The  loudspeaker can be positioned behind or to the side —and you hear what the audience hears.

Highly portable PA and monitor combined for solo performers, DJs and general-purpose use. Fixed vertical control with 180° horizontal coverage Reduced vulnerability to feedback.

Three systems to choose from (Compact, Model 1S, Model II)
Two passive bass module options (B1 or B2)
Consistent coverage and tonal balance, portability and easy setup.

Static or hum on higher volumes

Hi, just trying to find out why the Bose LI can't be turned above 1/2 volume without a loud hum or static coming out of the speaker. I attempted to use a mini-mixer with it and the hum increased. If playing at a large venue, the volume would need to be higher, but it can't be turned very high without the loud hum. (I'm plugging a Dean Markley transducer into it.) How do I resolve the loud hum? Thanks.

Original Post

Hi Harper!

Welcome to the Bose Portable PA Community.

I'm sorry you're having a problem with hum and static from your L1.

This has to be said - directly from Bose.

Safety Note

NEVER use a cheater plug or cut the ground plug off an ac power cord.

From the Owners Manual

Do not defeat the safety purpose of the polarized or grounding-type plug. A polarized plug has two blades with one wider than the other. A grounding-type plug has two blades and a third grounding prong. The wider blade or third prong is provided for your safety. If the provided plug does not fit into your outlet, consult an electrician for replacement of the obsolete outlet.
Please see this article about Audio System Noise and the L1.
Harper posted:

Hi, just trying to find out why the Bose LI can't be turned above 1/2 volume without a loud hum or static coming out of the speaker.

What model L1 do you have?

I attempted to use a mini-mixer with it and the hum increased. If playing at a large venue, the volume would need to be higher, but it can't be turned very high without the loud hum. (I'm plugging a Dean Markley transducer into it.) How do I resolve the loud hum? Thanks.

Ideally, the mini-mixer will have balanced output. If so, then use a balanced cable to the L1. That most likely means you'll use an

XLR to 1/4 inch (6.3mm) Tip-Ring-Sleeve cable

OR

1/4 inch (6.3mm) Tip-Ring-Sleeve  to 1/4 inch (6.3mm) Tip-Ring-Sleeve cable.

If you need help with the details, please give us a link to the manual for your mixer.

Thanks,

ST

Hi Harper,

Your link is broken.

 Please try again.

Also, please give us a link to your "analog reference microphone cable".  Are you connecting to channel 1 or channel 2?

Do you hear the hum when you turn up the volume controls separately?

Note: Channel 1 should not be turned up unless you have a microphone connected.

ST

I used to have hum issues with my prior PA system which is likely AC hum. I bought a hum-x plug in and used it by pluging it into the wall and then plugging a power strip into the hum-x. All items going into the PA plugged into the power strip. I had no isses after that including a room with all flouresent fixtures 

Hi, here is the link for the cable - all they have are the specifications.

http://www.mogamicable.com/cat...ional_configuration/

I attached the manual below.

I only used channel 1 - the volume was on 0 on channel 2. I did try Line 2 alone to see if it had the same issue, and it did. Even without adding a mixer, there is a loud hum coming from the speaker when even 1 channel is engaged. Again, the mixer enhanced the hum.

Thanks.

 

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As ST said, NEVER defeat the "LIFE SAFETY GROUND" on any piece of AC equipment. It's there for a reason, to save YOUR life.

Regarding the Ebtech Hum-X, nationally noted Acoustical Consultant/Designer/Integrators Dale Shirk and Ray Rayburn have this to say about it:

Dale: "Never lift or disconnect an AC safety ground, not even with a Hum-X.
This product is a lawsuit waiting to happen. It has no safety agency
rating, such as UL, and it never will, because it adds impedance in
series with the ground. It consists of a couple of diodes in series with
the ground wire as well as a small capacitor. Can you guess what will
happen when a hot-to-ground power fault occurs and several thousand
amperes flow through those diodes? Which blows faster, a circuit breaker
or a semiconductor device? These offer a false sense of security, are
unsafe, and will fail when an incident occurs."

Ray: "The concept of the Hum-X is to try to do a electrical ground lift in a
"safe" way.  It has a pair of diodes in parallel but polarized in
opposite directions between the 3rd prong ground connection of the
device and the power line ground.  In concept the diodes do not
conduct for small voltage differences (up to about 0.7 volts) and do
conduct for voltages higher than that.  Sounds like a very clever
solution to at least certain types of hum problems.

"The problem with this is that the ground needs to conduct enough
current so if there is a short inside your audio device the breaker
will pop, remove the power, and potentially save your life.  The
current needed to pop a 15 or 20 amp breaker (typical branch circuit
breakers here in the USA) can be many times the rated current of the
breaker.  The catch is that the diodes used in the Hum-X can't carry
enough current to trip the breaker.  So if there is a short in your
audio device the diodes in the Hum-X might blow out before the breaker
pops, leaving full mains voltage on the case of the audio device.  I
suspect this is why the Hum-X does not have a UL rating."

 

(Me again): If you are simply plugging the L1 Compact into a wall outlet with nothing plugged into it, and are getting distracting hiss and static at half volume, you either have dirty power in the venue or something is wrong with the L1-C. I have a pair of L1-C's that I run off of a Mackie ProFX8 (3 vocal mics, boundary mic in a cajon, and acoustic-electric via various guitar processors: G-natural, POD X3 Live, or IK Multimedia Amplitube Acoustic). I regularly run them at 1/2 volume or more at home and in multiple small venues with no issues with hum or hiss (not attributed to the cheap-ish mixer electronics at least).

Hope this helps,

Jeff

Hi Harper,

Thanks for the added information.

Let's do a little more trouble shooting.

  • Connect only power to the L1® Compact 
  • Channel 1 - turn the volume all the way off
  • Channel 2 - turn the volume to 12:00 o'clock
  1. Do you here a hum now?
  2. Do you still hear the hum you move the unit to a completely different location (different building)?

If the answer to 1 and 2 is "yes" then please call Bose Support. They will help you.

Bose® Product & Technical Support at (877) 335-2673
(U.S. and Canada only)
Monday-Friday: 9:00 AM - 9:00 PM ET

If the answer to 1 is yes, but 2 is no - then we've isolated to problem to the power or something in the environment in the first location.

Back in a minute...

ST

Edit: I wrote this before I saw Jeff's post above. 

Hi Harper,

Harper posted:

Hi, here is the link for the cable - all they have are the specifications.

http://www.mogamicable.com/cat...ional_configuration/

Those look like speaker cables. If you use those to connect to the inputs of the L1® Compact this is like an antenna for line noise. That's why we did the tests in my post above with nothing connected.

For connections to the inputs of the L1® Compact use an instrument cable for instruments (typically 1/4 inch (6.3mm) Tip-Sleeve plugs on both ends). Instrument cables - a common example is an ordinary guitar cord.

If you are connecting your mixer to the L1® Compact you have a couple of choices.  Pan your inputs hard Left and then use the Left XLR output OR the Left 1/4 inch (6.3mm) output.

Yamaha MG06 mixer outputs



I attached the manual below.

Thanks. I used it to make the picture above.

Use a cable like this for the XLR option

Tisino XLR Female to 1/4 Inch (6.35mm) TRS Jack Lead Balanced Signal Interconnect Cable Quarter inch to XLR Patch Cable - 3 Feet

or this for the 1/4 to 1/4 option

C2G 40073 Pro-Audio 1/4 Inch TRS Male to 1/4 Inch TRS Male Cable, Black (6 Feet, 1.82 Meters)





I only used channel 1 - the volume was on 0 on channel 2. I did try Line 2 alone to see if it had the same issue, and it did. Even without adding a mixer, there is a loud hum coming from the speaker when even 1 channel is engaged. Again, the mixer enhanced the hum.

Thanks.

You should connect a mixer to L1 Compact Channel 2

Note: Channel 1 volume should be off.

How did it go with the test?

ST

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"I'm plugging a Dean Markley transducer into it."

I have two instruments that have "workable" issues with piezo electric transducers. My Traveler Guitar Ultra-Light Acoustic-Electric Travel Guitar, with a Shadow piezo electric transducer gave me similar symptoms brand new out of the box. Since it was the only one they had in stock, I took off the access panel and immediately noticed two balled up cold soldered joints on the endpin jack attached to the pickup. The solution was to remove the old solder and resolder the wires with fresh rosin core solder, which ended the hum and the passive pickup was then and still is stronger without noticeable hum plugged straight into an amp/board.

 

My Ovation Applause Soprano Acoustic Electric 'ukulele has a passive (no battery or preamp) and not enough output to properly drive most amps/boards. I usually mic it, but do boost it through an LR Baggs Para Acoustic DI or a much less expensive Behringer ADI21 using their preamplifiers and EQ. This also gives a stronger signal without noticeable and corrects the output impedance for a more natural sound. Here I am performing with it right next to Bob Marley, John Lennon, Jimi Hendrix, Jerry Garcia and The Beatles!

 

RicBobMarleyJimiHendrix

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