DLR Audio fix

I found a way to improve the DLR audio. I’ve noticed heavily distorted receive audio on the DLRs in certain situations and it’s still distorted after turning the volume down on receiving DLRs. The DLRs don’t process the digital audio as well as the DTRs do. When a person climbs up on the microphone on a DLR, the audio can be very distorted out of receiving DLRs but still sounds OK on the DTRs. The distortion is still there even if you turn the volume down on receiving DLRs. It’s some strange DLR behavior that doesn’t happen in the DTRs. Given that it happens at low volume levels, it doesn’t appear to be due to the DLR’s 0.75W audio output compared to the DTR’s’ 1W output and the DLR’s smaller speaker. It sounds like the audio processing could be improved in the DLRs. I don’t think it’s a mic gain issue and I have played with that. The DLR audio is good coming out of a DTR so I think it’s an issue in the DLR receive audio path. I’m using my DLRs at the default (medium) mic gain.

I found an easy fix to improve the DLR’s transmit audio so it sounds better and distorts less on receiving DLRs. Turn on the treble boost option so the transmitted audio has more treble to it. It might sound slightly tinny and not full range but it does sound more crisp and distorts much less. The treble boosted audio from a DLR still sounds good on a receiving DTR. The treble boost option is labeled TREBLE on the ADVANCED page in the DLR programming in the CPS.

I’ve also noticed distortion in the DLR Audio. Thanks for the tip, I’ll enable TREBLE and see if it sounds any better.

From careful audio testing between my DLRs and DTR650 and with my new DTR700 radios, I found out a little more of what’s going on with the DLR audio. The new DTR700 has the best audio compared to the older DTRs and the DLRs. The DTR700 has an automatic gain control (AGC) in the transmitted audio to help control the audio level. I can talk a few inches away from a DTR700 or climb up on it and it sounds about the same. The DLRs and the older DTRs don’t have any AGC to help control the transmitted audio. The DLRs sound OK when talking a few inches away from them but transmit SEVERELY distorted audio when you climb up on them. When I do the same test with my DTR650, it sounds fine when talking a couple of inches away from it and sounds much louder when you climb up on it but without the distortion of the DLRs. The DLRs definitely don’t process the transmitted audio as well as the DTRs do.

My test methodology:

[li]All audio testing was done with the mic gain at the default (medium) setting. All receiving radios (DTR650, DTR700, DLR1060) had their volume level set at 2/3 of maximum. My standard volume setting I like to use on all receiving radios is 5 steps down from maximum. Step the volume up to maximum and step it a few more times to confirm it’s at max volume and then drop it down 5 steps. All receiving radios were far enough apart from the test radio to prevent acoustic feedback. A little echo heard in the background is OK. My receiving radios were about 8-10 feet away from the test radio. One receiving radio was used at a time during testing.[/li]nr[li]Talk in a normal voice during all testing. Test with normal voice about 2 inches from the mic and then test with normal voice while climbing right up to the mic on the radio, i.e., while practically eating the radio.[/li][/ul]

During earlier audio testing, I was testing DLR to DLR, DLR to a DTR650, and DTR650 to a DLR. That’s where I found enabling the TREBLE option appears to help a bit on the DLRs. It is most noticeable when talking with a DLR to a DLR. I suspect the DLRs also don’t handle the received audio as well as the DTRs do. It does not appear to be an issue with the DLR’s 0.75W output compared to the DTR’s 1W output and a smaller speaker. Turning the DLR volume way down to a low level still sounds just as badly distorted when the transmit audio is overdriven.

I also tried dropping the mic gain down from Medium (default) to Low. Dropping the mic gain helped reduce distortion but I found the mic gain to be too low and I couldn’t drive another radio to full volume no matter how hard I tried. I ended up leaving the mic gain at the default (medium setting) and experimenting with the TREBLE option.

After doing the same audio testing with my fleet of DTR700 radios and interacting with the DTR650 and the DLRs, I found the real issue with the DLR audio is the lack of AGC in the transmitted audio. Enabling the TREBLE option in the DLR brightens the audio up but it can still distort badly when heard out of other radios. With the treble option off (default), the DLR audio provided you don’t overdrive it is like the older DTRs and the DTR700. Enabling the Treble option definitely brightens the audio up compared to the older DTRs and the DTR700. The tradeoff is a treble boosted DLR radio will sound a little tinny compared to the DTRs. How much the treble boost option really helps the DLR audio is still a “?”. The real issue is lack of AGC in the DLR transmitted audio.

I now remind users of my DLRs to be careful when talking into them to avoid blowing everybody else out of the water with distorted audio. I tell them to always hold the radio 2-3 inches away and talk in a normal voice (don’t shout). Hopefully Motorola will do a firmware update to add AGC to DLR transmit audio.

Great information David! Thanks for all the time you put in to writing up your test results and sharing your experiences and opinions. It is a big help to us casual DLR/DTR users. Aside from these, and a couple other forums, there is very little “real” information out there about these radios.


Hopefully Motorola can improve the DLR audio by adding AGC to the transmitted audio like the DTR 600/700 has. Hopefully this can be done through a firmware update.