ProSoundWeb Community

Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => Wireless and Communications => Topic started by: Joseph D. Macry on December 04, 2015, 10:03:00 am

Title: Wireless analog point-to-point: oddity in the specs
Post by: Joseph D. Macry on December 04, 2015, 10:03:00 am
I've been considering using Listen Technology's assistive listening components to do point-to-point audio. Specifically purpose is to send a mix from a portable audio cart into an installed system in a Gym. There are no mic/line jacks so trying a wireless solution that is cheaper than Shure P9T-to-UR4+.

The oddity: Listen Tech's LT-800 transmitter and LR-100 receiver are available in 72MHz and 216MHz varieties. I assumed the 216MHz would have better specs. BUT: frequency response specs say
216 MHz - 60Hz to 10KHz (+/-3dB)
72 MHz - 50Hz to 15KHz (+/-3dB)

Whadya make of that?

Link to transmitter: http://www.listentech.com/shop/product/stationary-rf-transmitter-72mhz/
Title: Re: Wireless analog point-to-point: oddity in the specs
Post by: Scott Helmke on December 04, 2015, 10:17:51 am
Neither one is going to sound especially hifi - emphasis is on low cost and reliability, not sound quality. 
Title: Re: Wireless analog point-to-point: oddity in the specs
Post by: John Sulek on December 04, 2015, 10:24:07 am
I've been considering using Listen Technology's assistive listening components to do point-to-point audio. Specifically purpose is to send a mix from a portable audio cart into an installed system in a Gym. There are no mic/line jacks so trying a wireless solution that is cheaper than Shure P9T-to-UR4+.

The oddity: Listen Tech's LT-800 transmitter and LR-100 receiver are available in 72MHz and 216MHz varieties. I assumed the 216MHz would have better specs. BUT: frequency response specs say
216 MHz - 60Hz to 10KHz (+/-3dB)
72 MHz - 50Hz to 15KHz (+/-3dB)

Whadya make of that?

Link to transmitter: http://www.listentech.com/shop/product/stationary-rf-transmitter-72mhz/
more deviation allowed in the fm band would be first guess
Title: Re: Wireless analog point-to-point: oddity in the specs
Post by: Tim McCulloch on December 04, 2015, 12:04:57 pm
I'd contact Listen and ask them.  As to any technical reasons, I'll leave that to Henry or the manufacturer but I'd guess that for listening assistance bottom and top octaves can be sacrificial as they don't significantly contribute to intelligibility.
Title: Re: Wireless analog point-to-point: oddity in the specs
Post by: David Sturzenbecher on December 04, 2015, 12:08:02 pm
I am pretty sure what you are trying to do is also illegal. Those frequency bands are specially reserved for ADA hearing assistance. Proceed with caution.


Sent from my iPhone using Tapatalk
Title: Re: Wireless analog point-to-point: oddity in the specs
Post by: Joseph D. Macry on December 04, 2015, 12:53:08 pm
I am pretty sure what you are trying to do is also illegal. Those frequency bands are specially reserved for ADA hearing assistance. Proceed with caution.


Sent from my iPhone using Tapatalk

Interesting thought, David. Must look into that.
Title: Re: Wireless analog point-to-point: oddity in the specs
Post by: Tim McCulloch on December 04, 2015, 04:25:22 pm
I am pretty sure what you are trying to do is also illegal. Those frequency bands are specially reserved for ADA hearing assistance. Proceed with caution.


Sent from my iPhone using Tapatalk

Have receivers available for the intended use. So long as signal distributed contains the full program  I don't think the subsequent additional use infringes on the assistance.
Title: Re: Wireless analog point-to-point: oddity in the specs
Post by: Cailen Waddell on December 04, 2015, 06:35:04 pm

Have receivers available for the intended use. So long as signal distributed contains the full program  I don't think the subsequent additional use infringes on the assistance.

We use our assisted listening receivers with a small powered speaker when odd rooms become dressing or production offices at our PAC.  That said, there are laws about the minimum percentage of receivers required to be available vs number of seats - if you pull receivers in a system and don't have the minimum available you could open yourself to liability (unlikely) if you ran out of receivers. 


Sent from my iPhone using Tapatalk
Title: Re: Wireless analog point-to-point: oddity in the specs
Post by: Keith Broughton on December 05, 2015, 08:55:24 am
I've been considering using Listen Technology's assistive listening components to do point-to-point audio. Specifically purpose is to send a mix from a portable audio cart into an installed system in a Gym. There are no mic/line jacks so trying a wireless solution that is cheaper than Shure P9T-to-UR4+.

The oddity: Listen Tech's LT-800 transmitter and LR-100 receiver are available in 72MHz and 216MHz varieties. I assumed the 216MHz would have better specs. BUT: frequency response specs say
216 MHz - 60Hz to 10KHz (+/-3dB)
72 MHz - 50Hz to 15KHz (+/-3dB)

Whadya make of that?

Link to transmitter: http://www.listentech.com/shop/product/stationary-rf-transmitter-72mhz/
You are sending the sound to a GYM  :o ...what difference are those relatively minor differences going to really make?
Title: Re: Wireless analog point-to-point: oddity in the specs
Post by: Henry Cohen on December 05, 2015, 12:47:34 pm
I've been considering using Listen Technology's assistive listening components to do point-to-point audio. Specifically purpose is to send a mix from a portable audio cart into an installed system in a Gym. There are no mic/line jacks so trying a wireless solution that is cheaper than Shure P9T-to-UR4+.

The oddity: Listen Tech's LT-800 transmitter and LR-100 receiver are available in 72MHz and 216MHz varieties. I assumed the 216MHz would have better specs. BUT: frequency response specs say
216 MHz - 60Hz to 10KHz (+/-3dB)
72 MHz - 50Hz to 15KHz (+/-3dB)

Whadya make of that?

It's a result of FCC rules regarding occupied channel bandwidth limits. More band width for deviation is (was, actually, as only legacy certified products can still be manufactured in 72MHz IIRC) available for 72MHz systems compared to newer 216MHz systems. Since these assisted listening products are manufactured under the permitted use rules for "auditory assistance communications" ( 47CFR Part 95.1009(a) ), it's only the voice frequency range that's of interest, thus the narrower frequency band.
Title: Re: Wireless analog point-to-point: oddity in the specs
Post by: Henry Cohen on December 05, 2015, 12:49:49 pm
I am pretty sure what you are trying to do is also illegal. Those frequency bands are specially reserved for ADA hearing assistance. Proceed with caution.

47CFR §95.1009:
(a) Auditory assistance communications (including but not limited to applications such as assistive listening devices, audio description for the blind, and simultaneous language translation) for:

                  (1) Persons with disabilities. In the context of the LPRS, the term “disability” has the meaning given to it by section 3(2)(A) of the Americans with Disabilities Act of 1990
                       (42 U.S.C. 12102(2)(A)), i.e, persons with a physical or mental impairment that substantially limits one or more of the major life activities of such individuals;
                  (2) Persons who require language translation; or
                  (3) Persons who may otherwise benefit from auditory assistance communications in educational settings.

A creative interpretation of these rules might include that getting the audio signal to a remote set of speakers assists those with hearing difficulties. That said, I think there is legitimate justification if the event were an educational conference. (Obligatory disclaimer: I am not an attorney. Consult yours for more prudent guidance.)
Title: Re: Wireless analog point-to-point: oddity in the specs
Post by: Henry Cohen on December 05, 2015, 12:58:41 pm
You are sending the sound to a GYM  :o ...what difference are those relatively minor differences going to really make?

I like my poor STIPA values full bandwidth.