Halo Ax1 Balanced Inputs Level Question

[wildfire99]

This may be an Anthem issue or a Parasound one, but I'm thoroughly confused about it. Here's the question:

I recently switched my interconnects for my system (Anthem AVM30, Halo A21 and A51 amps, plus Behringer BFD for the sub) from RCA to XLR. I dutifully switched the amps to 'Balanced' using the toggle switches on both when I swapped the cables.

I now notice that the audio coming from the Halo amps is 6dB hot. That's unsurprising, as the Anthem manual clearly states that output from the XLR jacks is 6dB over RCA outputs.

I went through a whole ugly thing with my BFD earlier where I figured out that I needed to set it to studio-level inputs (+4dbV) to keep it from clipping using the XLR output of the Anthem. No problems there, it's what I would expect.

However, now that the Halos are using balanced/XLR inputs, I find that switching them to 'Balanced' on the rear makes them too loud in comparison with the sub. This is using a Radio Shack SPL meter to verify. I need to push the sub-out level to +6-7dB to equalize it with the main speakers to level match. Setting the Halo amps to the 'Unbalanced' position keeps everything at the same level. But that freaks me out, because I'm not using unbalanced inputs. Can anyone shed any light on this? Why would the Halo amps need to be attenuated with the XLR out from the Anthem, but the BFD wants the outputs (and works properly only if used) to be studio level? These are the same jacks! I already spent a ton of time with the BFD via the same XLR outputs from the Anthem to ensure it wasn't clipping, so I know it's set right.

Is there any problem with just leaving the Halo amps switched to unbalanced mode, would I lose any dynamic range? Or is there something weird going on possibly with the BFD, even though I already tested it to ensure it was getting proper levels (it only clips with a -1db input signal: sine wave 40hz).

[Peter Nielsen]

I now notice that the audio coming from the Halo amps is 6dB hot. That's unsurprising, as the Anthem manual clearly states that output from the XLR jacks is 6dB over RCA outputs.

In the Halo line, the gain difference between balanced and unbalanced is 4dB

However, now that the Halos are using balanced/XLR inputs, I find that switching them to 'Balanced' on the rear makes them too loud in comparison with the sub. This is using a Radio Shack SPL meter to verify. I need to push the sub-out level to +6-7dB to equalize it with the main speakers to level match.

Difference between speaker level settings is normal. It depends on the speaker efficiency, the speaker distance, etc.

If increasing the sub level is a problem, then the obvious solution is to decrease the levels of all other speakers. (Are you calibrating this to THX reference levels?)

FWIW, my mains are +2dB, center +8dB, surrounds +0dB, rears +2dB, subwoofer -8dB.

Is there any problem with just leaving the Halo amps switched to unbalanced mode, would I lose any dynamic range?

Yes. That is a problem. I'm using balanced interconnects and when I accidentally flipped the input switch to "Unbalanced", I got a noticable hiss! (This is on the JC-1 though). The switch is intended to be in the position that corresponds to the input used.

Peter

[wildfire99]

It's not calibrated to reference, since I don't like getting blasted with pink noise. I simply turn it to something reasonable (which is usually about 65-70dB) to level match with the processor's test tones, though that doesn't "calibrate" the volume control on the receiver, I know (nor does it verify that the DVD input is matched).

I do have some noise on all of the speakers (except sub), which isn't a hiss but an electrical buzzing, and it's noticeable from a few feet away. My cabling is, in a word, atrocious so I'm not concerned about it until I separate out the interconnects, speaker wire, and power leads. It could be ground issues but everything's plugged into the same outlet.

All my speakers are identical and roughly equidistant so they're all within +/- 1dB for pink noise according to the meter, hooray.

I'll just leave the Halo amps at 'balanced' then and adjust the sub level and BFD to fit. I have enough headroom on the sub out to compensate but I don't like to play with the levels that much (+7db), since that usually means something isn't set right. The BFD also seemed to be set up just right with regards to levels once I set the hat switch on the back to studio level (+4dbV), so it clips at -1dB input signal with both the BFD and the receiver levels set to 0dB adjustment, which is why I kind of trust that more than the input levels of the Halo amps. But the sub is easier to adjust, so eh.

The difference in volume is also scary. I was used to (with RCA interconnects) turning the receiver to 0dB (reference-ish) for films, and felt that it needed more 'oomph'. Using XLRs and the 'Balanced' switch setting, things start to get uncomfortably loud at around -14dB, so it's definately driving things harder. I know my new DIY speakers HAVE to be less efficient than the Klipsh there before. Heck, maybe I'm still doing something wrong. I'll have to play with it.

Maybe I'll just whip out the voltmeter and check output voltages, including off the pro gear I have sitting around. Maybe the Anthem is sending different voltages for the LFE channel and the mains. I've never used XLR interconnects before in a home system, so this is all (un)delightfully new.

Option B is also to adjust the gain control on the back of the amps, though that shouldn't be necessary should it?

[Peter Nielsen]

The difference in volume is also scary. I was used to (with RCA interconnects) turning the receiver to 0dB (reference-ish) for films, and felt that it needed more 'oomph'. Using XLRs and the 'Balanced' switch setting, things start to get uncomfortably loud at around -14dB

The XLR/Balanced setting sounds just about right! My C2 is calibrated to THX levels, and I usually watch movies @ -15dB. That IS pretty loud. With some movies it gets uncomfortably loud and I end up going down to around -20dB.

"0dB" pretty much means STOP in my system. Anything louder than that and there's a chance that the speakers start bottoming out :B

Peter

[Chris D]

I too calibrate to THX standards, and then just watch and listen to material at volumes that seem appropriate. Depending on the material, time of day, how clearly I want to hear detail, etc, this can vary from -30db to -10db sometimes. I rarely go -9db or higher unless I'm doing reference demos.