Forums Forums CQ Forums CQ General Discussions CQ18T IEM MONO MIXES ISSUES


This topic contains 10 replies, has 5 voices, and was last updated by Profile photo of gabo gabo 2 months, 1 week ago.

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    Profile photo of Val

    Hey there!

    Apologies for the lengthy post; English isn’t my first language, and condensing ideas isn’t my strong suit, haha.

    I’m the MD and drummer of a 5-member cover band. We perform regularly at small venues, bars, and events. Previously, we used a couple of Zoom L20s, one in our rehearsal space and a second one in our portable rack. They served us well but felt somewhat limited in terms of fine-tuning sound, mixes and effects. Excited by the possibilities offered by the CQ line, we replaced our L20s with two CQ18Ts.

    Most of the time, we handle our sound ourselves. I’m usually the one playing and controlling the mix, including everyone’s IEM mixes.

    After a week of experimenting with the mixer and setting everything up, our first show with the new equipment arrived. Unfortunately, it didn’t meet our expectations, mainly due to monitoring issues. My bandmates and I struggled to hear our mixes properly. We thought switching from stereo monitoring to mono wouldn’t be a big deal, but it turned out to be much worse. For some reason, every AUX out sounded flat, lifeless, and overly compressed. There was also a noticeable lack of low-frequency response compared to the Main LR out, which sounded great. Each bandmate complained about how thin and flat their mixes sounded, which really ruined the mood of the show.

    We tried troubleshooting by bypassing everything on our mixes — no limiter, no EQ, nothing. We turned off everything post-fader, but the sound still came out thin and compressed.

    I also switched my monitors (AUX 5 & 6 linked) from stereo to mono to see what they meant. Immediately, I noticed how the same mix I was hearing perfectly in stereo deteriorated significantly once in mono. It’s not just a panning issue; there are also problems with frequencies. What was perfectly balanced in stereo suddenly became muddy and unbalanced in mono. You can hear how some frequencies cancel each other out, it’s not good. We didn’t encounter these issues with our previous L20s. While it wasn’t the greatest mixer, at least my band was able to perform decently.

    I’m not sure if we’re doing something wrong. Do you guys have any pointers on how to improve things for my performers?


    Profile photo of Area51drones

    I too have a similar experience and still have my Zoom L-20. I’m still in my return window and have decided to return my CQ-18T and buy again once a sufficient firmware update is released.

    Profile photo of KeithJ A&H
    KeithJ A&H

    How are you connecting to the IEM system?
    I ask as the TRS outputs of the CQ-18T (and CQ-12T) are balanced mono, so if you connected them to a stereo TRS input of a headphone amplifier you’d get all kinds of phase weirdness and cancellation going on.
    You hopefully already know from the getting started and user guides too, that the outputs are line level, so you cannot connect headphones directly.


    Profile photo of Val

    Thank you, Keith.

    Appreciated the input here. The problem happened with two different setups, at our home studio we don’t use wireless, so we connected the headphones directly to the AUX outputs, yes, it is line level but we checked the output power and it was enough to drive the IEM headphones, is that an issue? Can that mess with the phase and frequencies or just the output level?

    The other scenario we had issues was live, connecting from each AUX output to 2 PHENYX PRO PTM-10 units to feed 4 performers, for example: AUX 1>left input and AUX 2>right input of each unit, the transmitter is working as dual mono, so each performer gets a different mono mix. As I get to do double duties, drumming and mixing, I have a wired connection to the mixer, using the Headphones B, listening to the outputs AUX 5 & 6 linked in stereo. I usually replicate the main LR mix to my mix so I can have an idea of what is going on generally but with the added click track.

    So based on our case, what would you say is the best way to connect our IEMs wired and wireless in each scenario? do we need 4 headphone amplifiers to go wired at our studio? Not sure if a multi mono input/output amplifier exits, can you give me an example of such device?

    Is our wireless connection wrong? What can we do to improve our wireless sound coming from the mixer?

    Coming from the Zoom L20 we didn’t have these problems, our system worked and sounded just ok.

    Thanks again for your reply, I’m proficient with these things, but not an expert, so any guide can help us to take advantage of our 2 CQ18Ts.

    Profile photo of willmodelisme

    A mono signal is send via TRS, the 3 wires are used:
    -1 for the GND,
    -1 for a signal (a mix of the L and R done inside the console)
    -1 for an invert of this signal.
    In normal situation dephasing of the inverted signal is done at the end device (end amplifier).
    But not for a stereo stereo headphone and it is obvious that you will have phase cancellation.
    To get a proper mono AUX into stereo headphone you need to use mono personal monitor device that allow to plug stereo headphone.
    To get one proper stereo OUT from AUX, uses 2 auxes.


    Profile photo of Area51drones

    Good posts regarding knowledge of outputs 1-6 of the CQ-18T. What is the solution for using headphones and / or IEM’s on outputs 1-6? Thank you for your patience with new customers to the Allen and Heath ecosystem. 🙂

    Profile photo of willmodelisme

    As I said, mono personal IEM system (generally the small cabled ones) can deal with STEREO headphone out of a MONO input.
    They have only one XLR input and a single jack stereo headphone out.
    But you wont’ get STEREO in the headphone, only 2 times the same mono signal.
    Those little pieces can also deal with real stereo, but only if the input is stereo.
    For the CQ, the only native stereo OUT are the headphones OUT.
    If you want to ear STEREO form the AUX, you need to use 2 AUX OUT from the console, by linking them in the CONFIG/INPUT tab.

    Make it simple, for most console,all XLR and combo jack IN/OUt = symmetric signal, witch mean that Tip and Ring share the same signal but one is phase inverted (long distance interferences protection),
    that mean no stereo.
    For a stereo signal (USB, BT or ST input), if you send it to one AUX, L and R are mixed and this mix is transported the same way:
    -one mix in the Tip
    -and the same mix but inverted in the Ring.

    Profile photo of gabo

    This is a problem these days with all the 1/4″ TRS devices.

    The problem is that a 1/4″ TRS looks like a stereo, but it’s not. It’s a balanced mono signal, where a stereo (like headphones) is an unbalanced stereo.

    – TRS balanced mono – Tip to positive, Ring to negative, and Sleeve to ground.
    – TRS unbalanced stereo – Tip to positive of one channel, Ring to positive of other channel, sleeve to negative/ground.

    So a TRS cable plugged into a balance mono on one end and an unbalanced stereo on the other end doesn’t work. Even if you’re device has a “mono/stereo” switch it may not work due to the TRS cable making connections to two different place inside the device. It may also work, it depends on how the device is wired.

    – Another point, to convert from a TRS balanced mono to a TS unbalanced mono, you connect Tip to Tip, Ring and Sleeve on the TRS is connected together and connected to Sleeve of the TS. This is actually the same as just plugging a TS cable into the TRS jack. Since there is no break between sleeve and ring, it joins those two together creating an unbalanced TS signal.

    So your best solution to try first, is just plug in a TS cable into the CQ18T’s 1-6 output and connect that to your IEM amp. Since the device now sees an unbalanced mono cable, the mono/stereo cable switched to mono might work correctly.

    If it doesn’t then you need to create a balanced mono TRS to and unbalanced mono TRS cable. It’s hard to find a picture of how to make one of these, but there are plenty of examples of balanced mono XLR to unbalanced mono TRS cables. Here’s a picture of one of those.


    To translate that picture into a TRS instead of an XLR… pin 1 to sleeve, Pin 2 to tip, and pin 3 to ring is the standard XLR to TRS unbalanced mono.

    – I’ll define a TRS cable with two ends, end1 and end2.
    – Connect Tip of end1 to two 470 ohm resistors.
    – Connect one of the 470 ohm resistors to Tip of end2
    – Connect the the other 470 ohm resistor to ring of end2
    – Connect ring and sleeve of end1 to sleeve of end2.

    Hope that helps..

    Profile photo of gabo

    I’ll add that this is called a “summing cable” and you can find XLR To TRS summing cables for sale. If you can’t build one of these look for a TRS to TRS summing cable, there are a few for sale although you might only find short ones, but you can use a female to male TRS cable to extend it.

    Profile photo of Val

    Wow! Thank you all for sharing your knowledge here, this is definitely a topic that I didn’t know was this complex, and from what I see, it is not well understood by most of us. I mean, the whole TS, TRS balanced or unbalanced vs stereo stuff is kind of confusing since they share a couple of connectors, but I’m trying to figure it out.

    So, I ended up buying a Behringer HA8000 to send 5 individual headphones mixes in our rehearsal space. I haven’t received yet, but I’m planning to connect each AUX output from the CQ18T to the AUX inputs of the corresponding HA8000 channel using a TS (mono) cable and then select the mono option in it.

    Now, Keith mentioned that the CQ18T aux outs are mono balanced, right? Will I miss anything frequency, noise, quality wise connecting both devices with a TS (mono) cable? What will be the best approach in this situation?

    Profile photo of gabo

    Ah, now you’re getting fancy with an HA8000! hahaha..

    Actually the HA800, I believe the “direct in” connections are balanced TRS mono connectors. So I think you can use a TRS to TRS cable to that input, so that makes it really easy. But you can also use a TS cable too and it should work just fine.

    The difference between TRS and TS… You won’t lose any frequencies or anything like that. The only difference is possibly a bit of noise. But it’s not guaranteed that you’ll get more noise with a TS cable, it depends on what type of noise interference you have (if any). So give it a try with a TS cable, most likely it will work fine. But with the HA8000 you can also try a TRS cable and see if you have any difference.

    The HA8000 takes care of doing the Mono to Stereo headphone conversion and let’s you set the headphone levels and let’s multiple headphones use the same mix, etc. etc. So that’s a good choice for all your in ears and will probably resolve all your problems.

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