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AV123 / GR Research X-Voce Speaker Review

Rate this speaker:

  • 1. Poor (headless panther)

    Votes: 281 93.4%
  • 2. Not terrible (postman panther)

    Votes: 10 3.3%
  • 3. Fine (happy panther)

    Votes: 2 0.7%
  • 4. Great (golfing panther)

    Votes: 8 2.7%

  • Total voters


Staff Member
CFO (Chief Fun Officer)
Feb 13, 2016
Seattle Area
This is a review, listening tests, EQ and detailed measurements of the AV123 hybrid open/closed baffle center speaker. It sold for $499 when the company was in business. GR Research seems to be selling the same speaker as a kit ($239 for pats, $250 for flat pack you assemble/finish).

AV123 GR Research X-Voce hybrid center open baffle home theater speaker review.jpg

No, I didn't just give the speaker a bath. The reason for the towel on top will become clear in the listening test section.

Speaker has unusual configuration. The outer woofers are in rather small sealed boxes. The center three drivers are open to the back, protected by a grill with some stuffing on top of the crossover located there:
AV123 GR Research X-Voce hybrid center open baffle home theater speaker top view review.jpg

AV123 GR Research X-Voce hybrid center open baffle home theater speaker back view review.jpg

May be able to see it more clearly in the GR Research picture:

It was very easy to get the bent metal to ring or if pushed, pop. Same material is used to screw om a very stout grill to the speaker using the stand-offs you see in my picture.

Speaker is kind of imposing weighing over 60 pounds and being quite deep compared to today's center speakers.

This review has quite a story to go with it so buckle up and let's get into it.

AV123 / GR Research X-Voce Measurements
Worried that the back reflections would create a complex acoustic pattern, I doubled my usual measurement points on Klippel NFS resulting in a scan that took a painful 5.5 hours! The resulting file was some 1.4 Gigabytes. What popped out after the computational phase was quite surprising:

AV123 GR Research X-Voce hybrid center open baffle home theater speaker frequency Broken Sampl...png

What is going on in bass??? Seems like the woofers are just resonating at a frequency (between 80 and 90 Hz) and that is that. No way is it able to blend into mid-woofers that way. Searching high and low online did not result in any measurements of the AV123 X-Voce as the company is out of business and wayback machine did not capture the graphics. So I went to GR Research website and was surprised there was no measurement there either! So I lugged the ungainly and heavy speaker up two flight of stairs to listen to it and finish the review. But then I thought, maybe Danny at GR Research has the measurements for his kit so I asked him for it.

He responded saying he didn't have any as he designed the above for AV123 16 years ago and he has to build his own kit to measure. Kind of strange on both fronts. If I designed a speaker 16 years ago, I would have some electronic record of it in email, old folders, etc. Anyway, he went on to question why I was asking saying. I went ahead and shared the above graph with him (without the notations). He wrote back quickly saying the driver polarity must be wrong and that would cause that deep dip. To me that was a secondary problem to the woofer having such a narrow peak. So I shared with him my near-field measurements of each driver:

AV123 GR Research X-Voce hybrid center open baffle home theater speaker frequency Broken Sampl...png

Here, the mic was just an inch or two in front of each driver, clearly showing that the response from the woofer is wrong regardless of what the mid-woofer is doing. Danny again said that it was clear this was a wiring problem. As much as I don't enjoy ripping open a speaker on a hunch like this with no evidence, I went ahead and took out some 20 to 30 screws and got to the crossover which is behind the tweeter/MTM drivers:
AV123 GR Research X-Voce hybrid center open baffle home theater speaker Crossover wired wrong.jpg

I had my son with me and his keen eyes instantly picked up that red wire is hooked up to "LOW-" instead of LOW+. The wires though were all symmetrical from bottom to up, each being white+red so it could be that the PCB label was wrong. To verify, I took out the left woofer and it became clear that indeed, wire colors were correct and the factory installer had wired it wrong. De-soldered the wires, and corrected the mistake and lugged the darn speaker back down two flights and on Klippel NFS. Quick near-field measurement shows little improvement but I thought I do the full scan anyway, this time opting for the standard 2.5 hour one.

Here are the second set of measurements: (original test was with the grill; this one without).
AV123 GR Research X-Voce hybrid center open baffle home theater speaker frequency response mea...png

We see that the dip is filled in more but the narrow, peaky response of the woofer remains. As I had guessed, the crossover fix didn't deal with the major issue but admittedly that was wrong as well. By this time, the conversation with Danny had gotten ugly with him claiming that my measurements are not high resolution, and that I was wasting my time spending more than 5 minutes on it. What to do now?

I wanted to verify the PCB wiring so googled out there and by accident, landed on a very interest thread on Audiocircle that is "home" to Danny as far as talking to his customers, etc. https://www.audiocircle.com/index.php?topic=162372.0

The owner there had a bunch of GR Research speakers which he liked but found his X-Static speakers boomy. X-Static is similar to X-Voce in that it seems to use the same set of drivers but with the open baffle being on top instead of the middle:


Unfortunately Audiocircle website doesn't allow linking to their images. :( So I am going to describe that he compared X-Static against X-Omni (former sealed, latter ported) shows a peak incredibly similar to my measurements! And like mine, it had a dip afterwards. Danny chimes in quickly blaming the room, placement, etc. :

"The X-Statik's use a sealed box for the lower woofers. So the natural roll off is pretty smooth and gradual. It doesn't look anything like your in room response.

You'll need to work with placement and room treatments to knock that peak out of it. Your room reflections are out of phase in the dipped area and in phase in the peaked area. So it is possible that if you absorb some of those room reflections you can knock down that peak and at the same time you might bring up that dipped area too."

He didn't know who he was up against as the owner showed in measurement after measurement how this is a property of the speaker and not the room. He eventually narrowed the problem to the drivers being out of spec, experimenting with adding some mass to them and improving things. The thread ends there with no more responses from Danny or the owner. This was in 2019 so would have had to been fresh in Danny's mind. Why he didn't volunteered to me that he had seen this exact problem before is troubling.

Back to our speaker, the owner had purchased this as a back up so had another X-Voce. I asked him to measure it in his room and he got nearly the same response as the poster in the above thread:
AV123 GR Research X-Voce hybrid center open baffle home theater speaker owner sample frequency...png

In absence of measurements like this, one could have blamed this on room modes and such but now that we know the anechoic response of the speaker, it is clear that his sample suffers from the very same problem. Hard to know if he has a crossover wiring issue as well but again, that is a minor problem compared the peaky response of the woofer.

Given all this data that two different productions of AV123 have this problem and so does a sample of similar design in X-Static doing the same years later in 2019, it seems to me that this is a huge production issue. Who knows how many bad speaker kits Danny has sold between these two models (and wherever else he uses the same driver).

Anyway, going with what we have, here is our early window frequency response which naturally looks pretty poor:
AV123 GR Research X-Voce hybrid center open baffle home theater speaker early reflections freq...png

Notice how the rear reflection is mostly coming from the mid-woofer. Naturally predicted in-room response is poor even though our model is not for rear firing speakers:
AV123 GR Research X-Voce hybrid center open baffle home theater speaker predicted in-room freq...png

Directivity is poor of course, making the speaker highly room dependent:
AV123 GR Research X-Voce hybrid center open baffle home theater speaker Horizontal Beamnwidth ...png

We have a classic "MTM" configuration which leads to narrowing of the response as the two mid-woofers cancel each other at some frequencies and angles. Fortunately the problem is not too severe so if you sit back far enough, it may be OK for a few seats. Directivity plot shows the same:
AV123 GR Research X-Voce hybrid center open baffle home theater speaker Horizontal Directivity...png

Vertically we don't have that problem although it is still best to sit at tweeter axis:

AV123 GR Research X-Voce hybrid center open baffle home theater speaker Vertical Directivity m...png

Doubling up the woofers and mid-range always results in low distortion which I like:
AV123 GR Research X-Voce hybrid center open baffle home theater speaker relative THD Distortio...png

AV123 GR Research X-Voce hybrid center open baffle home theater speaker THD Distortion measure...png

Impedance and phase don't show much other the speaker impedance being above average making it an easier load for an amp (although you may get less power):
AV123 GR Research X-Voce hybrid center open baffle home theater speaker Impedance and phase re...png

Danny is in the business of modifying other company speakers and routinely complains about "stored energy" in waterfall displays. It is kind of ironic that there is enough of that in X-Voce to power a few houses:
AV123 GR Research X-Voce hybrid center open baffle home theater speaker CSD Waterfall measurem...png

AV123 / GR Research X-Voce Listening Tests and Equalization
I wasn't about to lug the speaker upstairs again so opted for living room to listen to it as you see in the review picture. Upon power up, I thought something was seriously broken. Not in bass initially but in how the voices were so recessed. The sound seem to come from behind the speaker as if you were listening to your favorite singer in a public bathroom and you being next door! The back reflections were clearly pulling the perceived image behind the speaker but not a in a good way. Once I got past that I could hear singular bass notes that would come go, and once gone, there was little real bass there.

I thought I deal with tonality first so dialed in a couple of filters in bass:
AV123 GR Research X-Voce hybrid center open baffle home theater speaker eq equalization parame...png

Tuning bass response of a speaker in room is tricky as we are dealing with a mix of what the speaker is doing and the room. Still, after 20 minutes of trial and error, I settled on what you see above. The first two filters give you tight and correct bass response but there wasn't enough of it so I put in the shallow band 5. That acted as a sloping down room curve bringing very good bass response. Prior to that, i had put in the correction at 9 KHz which was also fixed some brightness.

This should have been it but wasn't. I couldn't put my finger on it but the voices and broad regions of the music just didn't sound right. I went to check to see if the mesh grill was the problem. It was resonating but I wasn't sure how audible that was. I went closer to listen to it and immediately found the reason culprit: the rear radiation from those drivers was so distorted! Moved my head in front of the speaker and sound was beautiful. Move to the top close to the mesh and you heard mid-frequencies that were distorted and unpleasant. Clearly the driver was not designed for open baffle application. As a quick solution, I grabbed that white towel and put it on top and back. The difference was remarkable! Speaker now not only sounded right but that phasey, distant effect I had observed was gone. The sound was now anchored to the speaker but without it being a point source.

I went through a number of reference tracks and almost all sounded quite nice. Overall there was a constant signature of speaker sounding spacious which may get boring with music that is not supposed to sound that way. But with the towel on top, it is probably livable.

On tracks with sub-bass, X-Voce would play them at around 20 to 30% with modest amount of distortion -- much better than majority of small ported speakers.

Clearly we have a design/manufacturing issue here. If the poster is right on the other forum, the design was based on one set of drivers, then speakers were/are being manufactured with drivers with different response, resulting in a speaker that is clearly broken. You could get lucky that your room modes kind of compensate for the errors but you will never know. Automatic EQ is likely to remedy most of the problem as well as did my manual EQ.

The notion of letting out random radiation out of the back is just wrong to me. If you are going to do that, you better make sure the response of the speaker is clean. Danny never measures distortion so this would be a lesson to start now. And to test the drivers being shipped to customers. And oh, while he is at it, he needs to measure down to 20 Hz, not gated measurements that are cut off at 200 Hz.

On crossover being miswired, the back of the speaker has a sticker saying the speaker was tested at the factory. Clearly even rudimentary frequency response was not performed to catch a) the wiring problem and b) driver issue if if is indeed the problem. Either way, it is a big mistake and likely responsible for some number of customers not being happy with the sound of their speakers.

At end, this all boils down to not doing proper things in designing and building speakers. Proper testing is a requirement and clearly that is missing seeing how you can't even get a measurement of this speaker from GR Research.

Needless to say, I can't recommend the AV123 or the kit version of X-Voce from GR Research. Danny needs to test his drivers and build a sample of this speaker to figure out what is going on. Assuming our investigation is right, he owes a lot of people fixes for speakers/kits they have bought from him.

EDIT: here is a video review:

As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/


  • AV123 GR Research X-Voce Frequency Response.zip
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Staff Member
CFO (Chief Fun Officer)
Feb 13, 2016
Seattle Area
GR Description and Specs (kind of):

The X-Voce speaker is another model that was designed for AV123. It is the matching center channel to the very popular X-Statik speakers. And the X-Voce is now available in kit form.

The X-Voce uses the highly acclaimed T26SG tweeter with four of the M-165/16 woofers. The two inside woofers are used as mid-bass drivers are are in an open baffle center section. The two outer woofers are true woofers and are in sealed boxes.

The X-Voce combines a smooth and transparent mid-range with high sensitivity (91db) and dynamics. It is an ideal center channel speaker for medium to large sized rooms. And the stable 8 ohm impedance makes it an easy load to drive for any receiver or amplifier.

The Sonicap upgrade improves clarity and detail.

The X-Voce can also be improved by upgrading the binding post cups to the Electra Cable Tube Connectors. The tube connectors are the highest quality connectors currently on the market. They offer improved clarity across the board and are extremely easy to install. The tube connector upgrade is extra.

Additional information​

Weight20 lbs
Dimensions13 × 10 × 10 in
Capacitor UpgradesStock Capacitors, Sonicaps ($117)
Connector UpgradeTube Connectors, Standard Binding Post Cup
Last edited by a moderator:


Senior Member
May 28, 2020
French, living in China
Here is my take on the EQ

Please report your findings, positive or negative!
The following EQs are “anechoic” EQs to get the speaker right before room integration. If you able to implement these EQs you must add EQ at LF for room integration, that is usually not optional… see hints there: https://www.audiosciencereview.com/...helf-speaker-review.11144/page-26#post-800725

The raw data with corrected ER and PIR:

Score no EQ: 1.0
With Sub: 3.6

AV123 GR Research X-Voce No EQ Spinorama.jpg

Spinorama with no EQ:
  • pff..
pff again.:

AV123 GR Research X-Voce 2D surface Directivity Contour Only Data.png

AV123 GR Research X-Voce LW data.png

EQ design:
I have generated two EQs. The APO config files are attached.
  • The first one, labelled, LW is targeted at making the LW flat
  • The second, labelled Score, starts with the first one and adds the score as an optimization variable.
  • The EQs are designed in the context of regular stereo use i.e. domestic environment, no warranty is provided for a near field use in a studio environment although the LW might be better suited for this purpose.
  • These EQ might not be suited for this king of speakers...
Score EQ LW: 4.3
with sub: 6.9

Score EQ Score: 5.3
with sub: 7.8

AV123 GR Research X-Voce APO EQ LW 96000Hz

Preamp: -6 dB

Filter 1: ON PK Fc 86.19,    -8.86,    3.87
Filter 2: ON PK Fc 176.73,    6.78,    1.16
Filter 3: ON PK Fc 276.15,    -3.00,    3.30
Filter 4: ON PK Fc 418.27,    2.65,    4.67
Filter 5: ON PK Fc 480.54,    -2.91,    1.13
Filter 6: ON PK Fc 928.06,    5.72,    1.78
Filter 7: ON PK Fc 958.75,    -5.58,    4.06
Filter 8: ON PK Fc 2009.91,    -1.95,    4.08
Filter 9: ON PK Fc 4207.36,    -1.40,    4.31
Filter 10: ON PK Fc 7382.39,    -1.09,    1.90
Filter 11: ON PK Fc 12608.44,    -1.98,    3.96

AV123 GR Research X-Voce APO EQ Score 96000Hz

Preamp: -5.9 dB

Filter 1: ON PK Fc 86.13,    -8.90,    3.61
Filter 2: ON PK Fc 172.17,    6.93,    1.17
Filter 3: ON PK Fc 278.81,    -3.43,    3.37
Filter 4: ON PK Fc 417.72,    2.79,    3.71
Filter 5: ON PK Fc 433.21,    -4.07,    1.32
Filter 6: ON PK Fc 906.63,    4.04,    2.55
Filter 7: ON PK Fc 939.69,    -3.79,    4.54
Filter 8: ON PK Fc 2273.70,    -3.37,    1.89
Filter 9: ON PK Fc 4089.57,    -1.99,    2.49
Filter 10: ON PK Fc 7934.53,    -2.81,    0.79
Filter 11: ON PK Fc 12973.59,    -2.29,    3.48
AV123 GR Research X-Voce EQ Design.jpg

Spinorama EQ LW
AV123 GR Research X-Voce LW Spinorama.jpg

Spinorama EQ Score
AV123 GR Research X-Voce Score Spinorama.jpg

AV123 GR Research X-Voce Zoom.jpg

Regression - Tonal
AV123 GR Research X-Voce Regression.jpg

Radar no EQ vs EQ score
Nice improvements?
AV123 GR Research X-Voce Radar.jpg

The rest of the plots is attached.


  • AV123 GR Research X-Voce APO EQ Score 96000Hz.txt
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  • AV123 GR Research X-Voce APO EQ LW 96000Hz.txt
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  • AV123 GR Research X-Voce 2D surface Directivity Contour Data.png
    AV123 GR Research X-Voce 2D surface Directivity Contour Data.png
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  • AV123 GR Research X-Voce 3D surface Vertical Directivity Data.png
    AV123 GR Research X-Voce 3D surface Vertical Directivity Data.png
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  • AV123 GR Research X-Voce 3D surface Horizontal Directivity Data.png
    AV123 GR Research X-Voce 3D surface Horizontal Directivity Data.png
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  • AV123 GR Research X-Voce Normalized Directivity data.png
    AV123 GR Research X-Voce Normalized Directivity data.png
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  • AV123 GR Research X-Voce Raw Directivity data.png
    AV123 GR Research X-Voce Raw Directivity data.png
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  • AV123 GR Research X-Voce Reflexion data.png
    AV123 GR Research X-Voce Reflexion data.png
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Major Contributor
Apr 26, 2020
I - wow. I can't believe anybody would design this and go "yeah, that sounds right". Even if you were just tuning by ear, That kind of peak and dip is going to sound seriously wrong, never mind everything else.

norman bates

Active Member
Forum Donor
Sep 29, 2022
Iowa, US
that lump at 2khz will help intelligibility, but guitars would be annoying on rock & roll or perhaps upper violin/piano ?
Then again, this is a center channel mainly for intelligibility..............

distortion looks good.
Directivity horizontally too tight up 700hz to almost 3khz..........
at 7', I don't think it would cover a couch wide..............

Bass rolls at 300hz then lumps up ? eek.
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Active Member
Jan 18, 2021
Bay area
I have never seen ski slope bass like that. On one hand it looks like it could perform, there is a lot of volume in the cabinet for deep bass. On the other hand the open mesh makes no sense. Did someone have an idea that that would be good, so they built it but did not actually test it? Since I have never seen that open mesh design in any other speaker it seems like they went out on a limb. Odd....Wasn't this the company where the owner went to prison for fraud? Fraudulent lotteries?


Oct 9, 2021
Is this what happens when a ”designer” is not an EE or has no acoustic design education?


Major Contributor
Forum Donor
Jun 3, 2019
New York City
Is there a “Panther in a Blender” option?

Prana Ferox

Addicted to Fun and Learning
Feb 6, 2020
I'm not at all familiar with what placement rules apply to a speaker like this with the top? side? of the speaker open to the drivers but the bottom side not? I'm surprised the spins aren't more vertically messed up. What would happen if you stood it up on its 'side'?

Every other open baffle speaker I've seen either literally has nothing but the front baffle and non-acoustic support structure, or some sort of tunnel diverting the backwave 180 degrees aft (and usually padded in some way to reduce radiated HF), not randomly out the side like this. The whole design has a very "I wanted to copy Jim Holtz without understanding what I was doing" vibe.

Deleted member 48726

No panther was willing to pose with this speaker....

I understand. PETA would take him away if they saw what filth you made him participate in.

This speaker could be designed by a twelve year old enthusiastic (but stupid) me.

What makes it even worse is the absolute arrogance and toxicity of the designer when someone even dares to question him. :confused:
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