# Convolution Reverb Surround Issue **URL:** \ **Category:** FMOD Studio\ **Created:** [January 11, 2022, 11:02am UTC](https://qa.fmod.com/t/convolution-reverb-surround-issue/18205 "2022-01-11T11:02:57Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![mattiapersico94](https://avatars.discourse-cdn.com/v4/letter/m/9fc348/32.png) [@mattiapersico94](https://qa.fmod.com/u/mattiapersico94)\ **Post date:** [January 11, 2022, 11:02am UTC](https://qa.fmod.com/t/convolution-reverb-surround-issue/18205/1 "2022-01-11T11:02:57Z")
I’m on a 5.1 game project and I noticed a weird issue with the convolution reverb (with 5.1 impulse responses). Everytime I open the Fmod Studio Project the return tracks where the reverbs are, generate a stereo output even if the convolution reverb meters shows a 5.1 signal out. The return’s out channel meter (the last one on the extreme bottom right after the panner) shows a stereo modulation. And it’s not only a graphical issue, the signal is definitely stereo. The workaround I found is to deactivate and reactivate the LINK option on the convolution reverb, but seems I have to do it everytime I open the project and I really don’t know if this thing reflects in the banks. Screenshot attached ![fmod convolutionreverb bug](https://canada1.discourse-cdn.com/flex036/uploads/fmod/original/2X/e/ebb43498948bcbdde8759b3e025fe4b5d4b39419.png) ---
**Author:** ![joseph](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/joseph/32/264_2.png) [@joseph](https://qa.fmod.com/u/joseph)\ **Post date:** [January 18, 2022, 5:34am UTC](https://qa.fmod.com/t/convolution-reverb-surround-issue/18205/2 "2022-01-18T05:34:49Z")
How many channels does your impulse response file have? The output format of a convolution reverb effect depends on the number of channels in the impulse response; if the channel format of the impulse response isn’t the same as that of the signal, the signal will be downmixed or upmixed accordingly. ---
**Author:** ![mattiapersico94](https://avatars.discourse-cdn.com/v4/letter/m/9fc348/32.png) [@mattiapersico94](https://qa.fmod.com/u/mattiapersico94)\ **Post date:** [January 18, 2022, 8:24am UTC](https://qa.fmod.com/t/convolution-reverb-surround-issue/18205/3 "2022-01-18T08:24:22Z")
The IR has 6ch (5.1 L,R,C,Lfe,Ls,Rs), the input signal has 6ch (as you can see in the screenshot) ---
**Author:** ![mattiapersico94](https://avatars.discourse-cdn.com/v4/letter/m/9fc348/32.png) [@mattiapersico94](https://qa.fmod.com/u/mattiapersico94)\ **Post date:** [January 24, 2022, 2:14pm UTC](https://qa.fmod.com/t/convolution-reverb-surround-issue/18205/4 "2022-01-24T14:14:56Z")
@joseph any news about the issue? ---
**Author:** ![joseph](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/joseph/32/264_2.png) [@joseph](https://qa.fmod.com/u/joseph)\ **Post date:** [January 24, 2022, 11:31pm UTC](https://qa.fmod.com/t/convolution-reverb-surround-issue/18205/5 "2022-01-24T23:31:59Z")
Unfortunately, I haven’t been able to reproduce the issue, and so haven’t been able to identify a cause or solution. When I test here, a 5.1 channel impulse response results in the convolution reverb effect outputting a signal in 5.1 channel format. Is the impulse response a 16 bit pcm file? Are you able to send us the impulse response file that you’re using? There may be some feature of it that is causing this behavior; having it on hand would allow us to examine it in more depth. ---
**Author:** ![mattiapersico94](https://avatars.discourse-cdn.com/v4/letter/m/9fc348/32.png) [@mattiapersico94](https://qa.fmod.com/u/mattiapersico94)\ **Post date:** [January 27, 2022, 8:27am UTC](https://qa.fmod.com/t/convolution-reverb-surround-issue/18205/6 "2022-01-27T08:27:03Z")
Yes I tried with 16bit pcm and 24bit pcm. Same problem with both. Attached the IRs wetransfer (make sure to set the thing as in the screenshot, save and close the session and then re-open it before the test) > **[Archive.zip](https://wetransfer.com/downloads/f7a5f6cd4e8f139440af42e9cbacd60820220127082627/a0a5b6)** > > 1 file sent via WeTransfer, the simplest way to send your files around the world ---
**Author:** ![joseph](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/joseph/32/264_2.png) [@joseph](https://qa.fmod.com/u/joseph)\ **Post date:** [January 31, 2022, 6:49am UTC](https://qa.fmod.com/t/convolution-reverb-surround-issue/18205/7 "2022-01-31T06:49:56Z")
I’ve been able to reproduce this issue using the impulse response files you provided, and have added this issue to our bug tracker. I’ll be fixed in an upcoming release of FMOD Studio. In the mean time, you should be able to work around the issue by adding an FMOD channel mix effect to the right of the convolution reverb effect in the signal chain, and setting the effect’s grouping property to 5.1. This forces the track to correctly output all six channels of the 5.1 channel format without changing the signal. ---
**Author:** ![mattiapersico94](https://avatars.discourse-cdn.com/v4/letter/m/9fc348/32.png) [@mattiapersico94](https://qa.fmod.com/u/mattiapersico94)\ **Post date:** [January 31, 2022, 9:12am UTC](https://qa.fmod.com/t/convolution-reverb-surround-issue/18205/8 "2022-01-31T09:12:52Z")
Thank you very much @joseph !