AVR Frequency Response Graphs

[MACCA350]

This started from this thread.

I Thought we'd start a thread to compare the Frequency Response of different receivers/pre-amps.

Method: Basically its taking the Mic out of the loop and connecting the preamp outputs of your receiver to the inputs of your soundcard.

There are 2 ways we need to connect so we can get the measurements we are after.
1) RED line = this is for the full spectrum sweep and Mains when crossover is engaged
2) GREEN line = this is for testing what is actually getting to the sub when crossover is engaged

Note: do not connect both at the same time

Thanks to Brucek for the graph


There are 3 measurements that we can look at
1) Full spectrum sweep 2Hz -->20kHz]
2) Mains with the crossover engaged
3) Subwoofer with crossover engaged

A couple of things I did to keep things simple.
On the receiver
1) Set volume trims to 0.0
2) Set main volume to 0.0
3) Do not adjust volumes between readings(this will keep a reference for comparing)

On REW
1) Under 'Settings' Make sure No Mic calibration file is loaded
2) Under 'Settings' create a soundcard calibration file (include all cables you will use in the loop) load the file and run a sweep and make sure you get a dead flat line.
3) Under 'Measure', set measuring level(dB FS) to -10
4) Under 'Measure', set the End Freq(Hz) to 24,000
5) After the full spectrum sweep, set the 'Trace Offset'(under 'Trace Adjustments) so that the line around 1kHz is as close as possable to 0db on the graph(I had to use -84.8) This value will need to be input to the other measurements, do not change this number even if the other graphs don't line up with 0db(remember we measured at the same level so these differences are due to the crossover being in chain of processing) You can click the 'Add offset to Data' button if you like.
6) Under 'Graph Limits', set to:
Top = 12
Bottom = -12
Left = 2
Right = 20,000
7) After measurements and adjustments are taken click on the 'All Measured' tab and your ready to post

When posting add the Receiver/Pre-amp model information.
You can zoom into the graph to find -1db and -3db points.
You should end up with something like my next post.

Any suggestions are welcome,
Cheers

[MACCA350]

Denon AVR-3805

Full (Red)
-1db at 4.5Hz
-3db at 2.2Hz

Sub channel(blue)
-1db at 6.9Hz
-3db at 4.4Hz

cheers

[JohnM]

The slight ripple you see at the low end is caused by a narrower impulse response window than is needed. If you look at the Impulse Response graph you'll see a section of the response that is not being included, so extend the window duration to cover all the area above the noise floor and the low end should show a smoother curve. If you post a plot of the impulse response (with the Y axis set to dB) I can indicate exactly what should be included.

[Otto]

Hi there,

I would expect the sub and main signals to intersect at -6 dB from their nominal levels, but it appears that they intersect more around 4 or 5 dB down (yes, I see that their nominal levels are above 0 dB slightly).

If I look at where each signal actually does cross at -6 dB, it appears that the sub's -6 dB point is about 80 Hz, while the main signal's -6 dB point is about 60 Hz.

Is it possible that there are two different crossovers set up? Perhaps something else going on?

[brucek]

Is it possible that there are two different crossovers set up? Perhaps something else going on?

Of course. Most systems use a 2nd order HPF (x5) and a 4th order LPF. This then accounts for the 2nd order roll off of the mains to result in an effective 4th order.

Any suggestions are welcome

My feeling is that most receivers/processors will be perfect in their crossover execution and will have a flat line out to 20KHz without fail (your green line). The differences we're most interested in would be the low end response effect on our subwoofers. This is where you would find differences between products. I would rather see the graphs from 2Hz to 200Hz (or at least that in addition to what you're requesting), to better examine the drop below 20Hz. Certainly all the crazies aficionados of bass down to 5Hz would be extremely interested in the constraint their equipment is placing on the final sound.



brucek

[MACCA350]

brucek wrote:

My feeling is that most receivers/processors will be perfect in their crossover execution and will have a flat line out to 20KHz without fail (your green line). The differences we're most interested in would be the low end response effect on our subwoofers. This is where you would find differences between products. I would rather see the graphs from 2Hz to 200Hz (or at least that in addition to what you're requesting), to better examine the drop below 20Hz. Certainly all the crazies aficionados of bass down to 5Hz would be extremely interested in the constraint their equipment is placing on the final sound.

brucek

I agree that the majority of differences will be below 20Hz, but I would like to keep the full sweep also because you never know, we may just find some manufactures altering their response to have a "signature sound". That would be interesting

The other question is, do we adjust the second sub only graph so that the highest point is at the 0db line, even though it read higher under identical conditions(I'm leaning towards yes). I'm really wondering why the inclusion of the crossover increased the line by about 0.5db

The other thing that was interesting was the noisefloor as shown in the impulse response graphs. Both Full and Mains was -105db, but Sub was -60. I think this was due to signal being passed through above the crossover, I've zoomed out the graph, see here:


cheers

[brucek]

we may just find some manufactures altering their response to have a "signature sound".

doubtful........

The other question is, do we adjust the second sub only graph so that the highest point is at the 0db line

I would say no. You'll see in my graph that I am below 0dB since the crossover at 60Hz never hits 0dB before the response starts to drag the line back down. The proof is in the fact that at 60Hz it is exactly at its proper -6dB target.... if I had used 80hz cross, then it would have hit zero....

brucek

[MACCA350]

JohnM wrote:

The slight ripple you see at the low end is caused by a narrower impulse response window than is needed. If you look at the Impulse Response graph you'll see a section of the response that is not being included, so extend the window duration to cover all the area above the noise floor and the low end should show a smoother curve. If you post a plot of the impulse response (with the Y axis set to dB) I can indicate exactly what should be included.

I'm not sure I understand how to make those changes. Here are the Impulse Response graphs.

Full


Main


Sub


cheers

[MACCA350]

brucek wrote:

doubtful........


I would say no. You'll see in my graph that I am below 0dB since the crossover at 60Hz never hits 0dB before the response starts to drag the line back down. The proof is in the fact that at 60Hz it is exactly at its proper -6dB target.... if I had used 80hz cross, then it would have hit zero....

brucek

This doesn't explain my graph, since mine reached over 0db and the -6db line crosses at about 84Hz instead of the 80Hz crossover as set in the AVR. adjusting to 0db brings the -6db point to 80.9Hz. Any ideas why there was an overall increase when the crossover was engaged?

I'll hookup my Denon 1603 in the morning and see what that does.

cheers

[JohnM]

Macca,

Click the IR Windows button in the REW toolbar then adjust the Right Window value until the dotted line is out where the impulse response dispappears into the noise level. For the blue trace that is about 650ms for the response you captured (but see the noise floor comment that follows), for the red trace about 1200ms. After you adjust the value, hit the Apply Windows button to apply it. You will then find the responses roll off more smoothly at low frequencies.

The noise floor is high for the sub (blue) trace because you did a full range sweep but there is no useful output above a few hundred Hz, so the captured signal just has noise for much of the swept range. Do a sweep to 500Hz or so for the sub and you will see a much lower noise floor.

[MACCA350]

JohnM wrote:

Macca,

Click the IR Windows button in the REW toolbar then adjust the Right Window value until the dotted line is out where the impulse response dispappears into the noise level. For the blue trace that is about 650ms for the response you captured (but see the noise floor comment that follows), for the red trace about 1200ms. After you adjust the value, hit the Apply Windows button to apply it. You will then find the responses roll off more smoothly at low frequencies.

The noise floor is high for the sub (blue) trace because you did a full range sweep but there is no useful output above a few hundred Hz, so the captured signal just has noise for much of the swept range. Do a sweep to 500Hz or so for the sub and you will see a much lower noise floor.

Understood, and adjusted, thanks. I also noticed that increasing the window lowered the -1db and -3db points on the graph for the Full range plot. I'll remember to cut the sweep for the Sub plot next time, I may redo the above Sub plot in this way and see if it makes any difference to the -1db and -3db points.

Do you opinion on the issue of the different trace levels as stated above. I'll add a second graph for the Sub plot, but I'm still not sure whether to set the highest point to 0db for reference purposes, because this will affect the -1db and -3db points(I think these points should be compared to the highest point on the plot, but then again )

I'm about to run some tests for the Denon AVR-1603, so those graphs should be up soon.

cheers

[MACCA350]

Ok I've got an interesting one here.
This is the Denon AVR-1603 with 80Hz crossover

Red = V.AUX input and CDR output
Purple = EXT. input and SUB output
Green = V.AUX input and SUB output with speakers set to LARGE(LFE+MAIN on/pff didn't make any difference) set to both STEREO/DIRECT(this trace is also the same with speakers set to SMALL but with prologic cinema or DIRECT enguaged)
Blue = V.AUX input and SUB output with speakers set to SMALL set to STEREO

Something really screwy going on there I even reset the microprocessor but it didn't make any difference.

Any ideas?

cheers

[MakeFlat]

MACCA350 wrote:

Blue = V.AUX input and SUB output with speakers set to SMALL set to both STEREO/DIRECT

Something really screwy going on there I even reset the microprocessor but it didn't make any difference.

Any ideas?

cheers

I'll comment on the blue curve. Your result is consistent with my REW runs for the Stereo Mode on the Denon 1604. There is one difference: In the Direct Mode, the SUB response appears to roll off at 8Hz on my 1604's SUB output. So I guess Denon changed the design. Why they decided to roll off Stereo at 40Hz on the Denon 160x, it stumps me

Also, on my REW runs, in Stereo Mode, the mains and sub appear to be quite a bit lower in level when compared to all other modes: PL2, 5 Ch, Direct. The level is consistent with what you find on the sub's level.

[MACCA350]

MakeFlat wrote:

I'll comment on the blue curve. Your result is consistent with my REW runs for the Stereo Mode on the Denon 1604. There is one difference: In the Direct Mode, the SUB response appears to roll off at 8Hz on my 1604's SUB output. So I guess Denon changed the design. Why they decided to roll off Stereo at 40Hz on the Denon 160x, it stumps me

Also, on my REW runs, in Stereo Mode, the mains and sub appear to be quite a bit lower in level when compared to all other modes: PL2, 5 Ch, Direct. The level is consistent with what you find on the sub's level.

You're right. I just redid the DIRECT and STEREO measurements with speakers set to SMALL, and the DIRECT line is identical to the green plot(I've changed the previous post to add these changes).

So it seems that with speakers set to SMALL and in STEREO mode the SUB channel is seriously attenuated, yet setting the speakers to LARGE gives you full output on the SUB channel(and the LFE+MAIN feature makes no difference), to me this is backwards.

It seems to be only the STEREO mode when speakers are set to SMALL that cuts the SUB channel output. I ran a sweep with the crossover set to 120Hz and comparing both it looks like there is a subsonic filter engaged in this mode around 40Hz or so(as you suggested)

But the question is why, If you tell the receiver your mains are small and you have a sub, why is it cutting off the sub channel like this ONLY in stereo mode, really doesn't make sense

cheers

[Otto]

Hi MACCA,

I will agree that that seems strange in both cases. The way I think it should work is that there wouldn't be a difference between the LPF crossover between small and large -- the small and large settings should only affect the mains. I guess I should that that this is true as long as you have the "LFE+Main" feature set. But you already know that, which is why you're complaining about the seriously attenuated sub output in the "Small & Stereo" case above.

Unfortunately, I don't have any reasoning for its behavior, but I can offer a few other comments.

While I tend to agree with brucek that we are frequently concerned with the subwoofer band, I do believe there's some value in keeping the mains sweep in there. I would imagine that most of the time it will be correct. However, as you may have seen in my thread here, I was able to detect a problem with the HPF of my Outlaw 990 (I notified Outlaw, and after a bunch of discussion, they have indeed acknowledged that this is likely a real problem). I only measured the listening position response, but you can clearly see a HPF engaged on the mains when it should not be (in DIRECT mode, of all things!?!?!). So, I'd like to see the mains signal in there in addition to the others. I think that the upper frequency of 200 Hz is good.

Here's another thing. I don't know how many receivers you have access to, or how much trouble it might be, but the Outlaw discrepancy taught me something: the behavior of the different "modes" may be different, even though one would expect it to be the same. I don't think you started this thread/project as an effort to find bugs in these products, but as long as you have one "on the bench" you might consider scrolling through as many modes as possible. I didn't go through all the modes on the 990, but I did hit all the 2-channel modes. Anyway, just a suggestion.

Wow! All this talk of modes reminds me of "Direct Mode" a.k.a. "Bypass Mode". I tend to think of this mode as applying zero change to the original signal, so you might see some different behavior here. It was "Bypass Mode" in which I found the Outlaw was applying a rolloff to the mains when set to Small (though it had nothing to do with the actual crossover frequency selected). Do you know how the Denon is supposed to behave? I would somewhat expect that there would be no LPF on the sub out in Direct/Bypass mode. I do believe the implementation of "Direct Mode" could vary from manufacturer to manufacturer.

So, MACCA, I just want to say that this is an awesome thread -- very educational. Keep up the good work! I will be working to post this information for my Outlaw 990.

Thanks!!!

[clubfoot]

MACCA350 wrote:

You're right. I just redid the DIRECT and STEREO measurements with speakers set to SMALL, and the DIRECT line is identical to the green plot(I've changed the previous post to add these changes).

So it seems that with speakers set to SMALL and in STEREO mode the SUB channel is seriously attenuated, yet setting the speakers to LARGE gives you full output on the SUB channel(and the LFE+MAIN feature makes no difference), to me this is backwards.

It seems to be only the STEREO mode when speakers are set to SMALL that cuts the SUB channel output. I ran a sweep with the crossover set to 120Hz and comparing both it looks like there is a subsonic filter engaged in this mode around 40Hz or so(as you suggested)

But the question is why, If you tell the receiver your mains are small and you have a sub, why is it cutting off the sub channel like this ONLY in stereo mode, really doesn't make sense

cheers

Could it be that in LFE+large mains, the design thinking is that you are driving mains that are wired to the sub and using the sub xover instead of the processor xover? And when small is selected the processor is "thinking" it has to protect the small speakers from damage so it adds subsonic protection!.....regardless of a sub being connected?!

This could also be designed to not over drive the power amp section of receivers.

My question is, I set my processor to stereo, small + sub and use REW to do calibrations,...wouldn't this mode introduce "errors" in what I see on plots without knowing there is a roll off to compensate for, I will have to try it with mains set to large.

[brucek]

Any ideas?

That drop off in the response in stereo doesn't make a lot of sense. Try just feeding one channel and not two channels from REW into the receiver. The REW signal is mono, and should only be sent to one channel to do the testing....

brucek

[Otto]

I had an opportunity to measure my Outlaw 990 today, and there are some interesting results. I know that I used a -30 to +12 range on the X axis, but I liked it because I find it gives better resolution as to crossover slope (I went back and forth for a while, and settled on this). My apologies that it's different than previous posts.

Here is "Stereo Mode". I believe that this is the most correct one. However, I believe that the mains are employing a 4th order filter where it should only be a 2nd order filter. I determined this by looking at the mains signal from 80 Hz down to 40 Hz. In that range, it has dropped 24 dB. Each "order" of filter should cause a drop of 6 dB per octave, so 24 dB per octave is a 4th order filter. I think this is wrong to have a 4th order filter on the mains, as described by brucek above, and also because the 990 is spec'd in its manual as having a 2nd order filter on the mains.

As I understand it per brucek, the mains, with their 2nd order filter, should intersect the crossover point(in this case 80 Hz) at -3 dB. In this case, the mains having a 4th order filter causes them to intersect with 80 Hz at approximately -6 dB. I believe this is incorrect.

The sub signal crosses 80 Hz at -6dB with what appears to be a 4th order filter. This seems correct, although the response itself does hump up a bit from 20 to 50 Hz, likely as a result of imperfect filters (none of them are "perfect"). All in all, the sub response seems OK.

The "Large" signal for the mains seems OK.



I also measured "Upsample Mode". From time to time, I get a very annoying static/crackling sound when using "Upsample Mode". This weekend is "one of those times" (started on Thursday night). I can't seem to get rid of it at this point, so I thought I'd measure it. Yes, it sounds as good as it measures. Interesting that the noise doesn't seem to affect the sub. "Upsample Mode" also seems to be afflicted by the 4th order filter on the mains. I opened a trouble ticket with Outlaw yesterday about the crackling, but have not yet received a response (understandable since it was submitted on a Saturday -- The Outlaws are generally very responsive to user issues, and have excellent customer service, product support, and warranties). EDIT: Two things -- first, the graph should be labeled "Upsample" mode at the top, not "Bypass". Second, this phenomenon of crackling in "Upsample" mode has gone away after a week or so. The Outlaw was out of my system (unplugged from all AC power) for about a week, and when reinserted, it didn't do this anymore. I had unplugged it for ~30 seconds in the past to try to get rid of this problem, and it had persisted across at least a couple power cycles.



Here is a measurement of "Bypass Mode," which is intended to be just the true analog signal as it comes from the source. No digital to analog conversion, no bass management on the mains or the sub, regardless of speaker "size" (large/small) or crossover frequency; none of those controls should make a difference to the output signal. Note that some type of filtering is applied to the mains signal when the mains are set to "small". This measurement was the same as shown, regardless of crossover frequency, as long as the mains were set to small. This is unacceptable in my opinion. It also leads me to ask: is this filtering going on in the digital domain? If so, why are we sampling (performing an analog to digital conversion) on bypass mode? And finally: if the Model 990 is doing those types of operations on the simplest input "mode" what else is going on that we still don't know about? I have opened a problem ticket with Outlaw, and I do acknowledge that they are considering this an actual problem. Kudos to Outlaw in that regard. My other thread is here.

Also notice the slight discrepancy between main and sub levels in the full range measurements. I would think that a true bypass mode would be able to get those levels dead on.



Finally, there have been some complaints on the Outlaw Forum ("The Saloon") about the Model 990 applying bass management to the LFE signal. Indeed, Outlaw has described the bass management's crossover points such that they define the transition point between the bass material in a given speaker group ("fronts", "center", "surrounds" and "rears") and the subwoofer. The LFE channel is an independent channel as defined by the DD/DTS specs, and should not be filtered. If it is filtered, where does that information go? Apparently in the trash can... The LFE channel is spec'd to 120 Hz (for DD, at least, IIRC), and should be allowed its full bandwidth through the system. Since REW doesn't have the ability to output a discrete 5.1 signal, I opted to use the 7.1 channel analog inputs on the Model 990. Actually, I only used the "sub" of those 7.1 inputs, but that's all I'm really interested in for this test. Now this is where I make a small leap -- I'm going to assume that just like the discrete LFE track coming down a digital connection, the Model 990 should NOT apply bass management to any "sub" channel that comes in via the 7.1 inputs. My reasoning is twofold. First, some (all?) DVD players implement their own bass management. Therefore, any subsequent bass managment in the processor would not only be undesirable, it would be mucking with an already filtered signal. Second, the same reasoning as before -- why apply bass management to a signal that is, by definition, passed to 120 Hz and has no where else to go when filtered? You're just dumping content down the drain. This is unacceptable to me as well, and another member at the Outlaw Forum has submitted a trouble ticket for this issue. I believe that Outlaw will fix this issue as well, as theyhave been very helpful in the past, and have already provided at least two firmware upgrades. Anyway, here's the trace (sorry about the X-axis range, I didn't notice that till I was done):

[MACCA350]

brucek wrote:

That drop off in the response in stereo doesn't make a lot of sense. Try just feeding one channel and not two channels from REW into the receiver. The REW signal is mono, and should only be sent to one channel to do the testing....

brucek

Yeah, no sense at all. All testing was with REW feeding the Right channel input only. Maybe I'll try it with REW driving the Left channel only.

I'll have another play shortly. I also want to recheck with the Large setting engaged because that should cut the sub channel completely.

Found some info in the Denon AVR-3805 manual about the Direct and Pure-Direct functionality(I couldn't find much in the 1603 manual)

DIRECT mode
Use this mode to achieve good quality 2-channel sound while
watching images. In this mode, the audio signals bypass
such circuits as the tone circuit and are transmitted directly,
resulting in good quality sound.(says nothing about bypassing the A/D processing or bass management)

PURE DIRECT mode
In this mode, the music is played with an extremely high level
of sound quality.
When this mode is set, all the video-related circuits are turned
off so that music signals can be reproduced with high quality.
When an analog mode is selected, the digital processing
circuitry is also turned off to achieve analog sound with even
higher purity. (See NOTES)

NOTES:
• The system setup function cannot be used when the PURE DIRECT
mode is set. To use the system setup function, cancel the PURE
DIRECT mode.
• The ZONE2 video output is not output in the PURE DIRECT mode.
• The channel level and surround parameters in the PURE DIRECT
mode are the same as in the DIRECT mode.
• When the PURE DIRECT button is pressed while in the PURE
DIRECT mode, the PURE DIRECT mode is cancelled.
• The subwoofer’s channel level must be set to “OFF” in order to
turn off the digital circuit in the PURE DIRECT mode.

Explains why bass management is occurring in Direct and Pure Direct mode with Denon models, maybe we should take our own advice......moo baby moo

Otto, Interesting stuff there especially what's happening with the upsampling, and you're External inputs, as you can see the 1603 is not modifying it's External inputs(although it has other issues). Was there anything abnormal above 200Hz? Good to hear Outlaw are taking things on board.

cheers

[Chrisbee]

The effect you see in "stereo" may be simply be a rumble filter for turntables.
Most music (except organ and electronic) lacks anything useful under (say) 40Hz anyway.
Though a bypass option would be nice.
I'm glad I don't use an AVR for my stereo organ music listening!
In fact I still don't own an AVR.

[MACCA350]

Chrisbee wrote:

The effect you see in "stereo" may be simply be a rumble filter for turntables.

That would be fine except that this happens on all inputs, eg. DVD, CD, etc.

Most music (except organ and electronic) lacks anything useful under (say) 40Hz anyway.
Though a bypass option would be nice.

Thats beside the point, and I've got plenty of music that digs well below 40Hz.

Basic stereo mode with bass management applied should operate correctly and it's not, to make it work correctly I need to put it into direct mode.

The other thing to note is that this attenuated sub output(blue line)only occurs when in STEREO mode, speakers set to SMALL and subwoofer set to YES. And when you change the speakers to LARGE(and keep everything else the same) you end up with full sub output(green line), in fact every mode with speakers set to LARGE gives you full output on the sub channel.

This is definatly not right because the signal is being input on the Main L or R channel and if speakers are set to LARGE and LFE set to NORM you should get nothing on the sub channel. Only when LFE is set to +MAIN should you get output on the sub channel in this case, and with the 1603(and 1604, thanks to MakeFlat) this is not the case.


cheers

[MACCA350]

I re-measured everything trying both V.AUX and DVD Left channel input and came up with the same results.

I might have another play with the 3805 and see if it does anything funny(although I highly doubt it, but you never know)

Cheers

[Otto]

MACCA wrote:

Was there anything abnormal above 200Hz? Good to hear Outlaw are taking things on board.

Didn't notice anything weird above 200 Hz. Yeah, I really tried to credit the Outlaws because they do such a good job -- my commentary is somewhat critical, but I don't want to bash the Outlaws, really. I'm just reporting what I'm finding...

[MACCA350]

Ok, I did some more testing on the 3805. Here's a couple of things to note.

1)the sub output is correct for all modes. eg. no attenuated funny stuff like the 1603.

2)the sub output can be turned off in the volume trims(when DIRECT or PURE DIRECT is engaged) as noted in the manual. This setting is global for DIRECT and PURE DIRECT. eg for all inputs(not sure about DD or DTS signals) but does not affect any other modes(eg STEREO, etc). so you can have it either way for DIRECT and PURE DIRECT.

3)the LFE - LFE+MAIN setting makes no difference for 2channel material in STEREO, DIRECT, PURE DIRECT and some DSP simulated modes including 5/7.1 STEREO mode.

4)the LFE - LFE+MAIN setting only operates on 2channel material when PLIIx, DTS NEO:6 and most DSP simulated modes. Going on this I'd assume proper operation on DD and DTS multichannel tracks.

The manual explains 3) and 4) on page 37

Selection of the “LFE ” play mode will play the low frequency signal range of the channel selected with “LARGE” from that channel only.
Therefore, the low frequency signal range that are played from the subwoofer channel are only the low frequency signal range of LFE (only
during Dolby Digital or DTS signal playback) and the channel specified as “SMALL” in the setup menu.
• Select the play mode that provides bass reproduction with quantity.
• When the subwoofer is set to “Yes”, bass sound is output from the subwoofer regardless of the subwoofer mode setting in surround modes
other than Dolby/DTS.
• In surround modes other than Dolby Digital and DTS, if the subwoofer is set to “YES”, the low frequency portion is always output to the
subwoofer channel. For details, refer to “Surround Modes and Parameters”. (See page 83)

BTW, I suggest disconnecting ALL speakers when testing DSP simulations, I near cr@pped myself on one of those:raped:

cheers

[Hakka]

Denon 3803

First graph is Stereo

Red = small/main
green = large/main
purple = small/sub

My sub trim was set at +0.5 for the test, not sure why the level is up that much over the mains.

Second graph is Pure Direct

Green = Sub
Brown = main large/small

The mains show the same signal regardless of the speaker size setting.

The third graph shows stereo(green) vs pure direct (blue) main/large.

The fourth graph shows stereo(purple) vs pure direct(green).

Notice the high freq boost in stereo mode.


I tried to do a measurement using the optical output of my soundcard but my receiver shutdown as soon as I started the sweep. :holycow:

Harry.