This is a review and detailed measurements of the Monoprice THX-365IW THX Ultra certified, 3-way in-wall speaker. It was kindly purchased new by a member and drop shipped to me for testing. It costs US $400 from the company direct.
This is the first in-wall speaker we are measuring so I had to go through some prep to test it. Between the owner and I, we decided to build a back box using 2x4 American studs. The THX-365IW is made to hold on to drywall or plywood so I built the latter from scraps I had in my woodshop:
As you can see, the baffle is wider than the frame I built to give it some (small) approximation of it mounting on full wall. Clearly this is a compromise as making this much bigger would make it much heavier and harder to measure. I chose to not seal the back box enclosure as in typical application of it just mounted to a well, it enjoys a very large space behind it. I figured allowing leakage would reduce the back pressure on the driver. Good or bad decision? I let you all comment. I confirmed during testing that copious amount of air was leaking around the 2x4 framing.
In addition, I made the executive decision to use the metal, magnetically attached grill as I doubt anyone would use such with exposed drivers. Speaking of which, this is a 3-way design with dual woofers:
Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors enable testing in ordinary rooms yet results that can be more accurate than an anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.
I performed over 1000 measurement which resulted in error rate of less than 1% below 10 kHz. Above that error shot through the roof so that area of the response is likely not reliable.
Reference axis was the tweeter center. I also tested it with mid-range being such but it did not make much of a difference.
Monoprice THX-365IW Measurements
Acoustic measurements can be grouped in a way that can be perceptually analyzed to determine how good a speaker is and how it can be used in a room. This so called spinorama shows us just about everything we need to know about the speaker with respect to tonality and some flaws:
The graph is pretty unsettling at first blush. The low frequency variations though I believe due to leaky back box. Actual response in room will be different both because of that and room variations. Its level is higher than the rest of the response. Company produces its own measurements which we can compare:
Alas, they don't list any conditions as to how the test was done. The low frequency response is indicated as "near-field" which tells me is not anechoic. There is decent correlation between theirs and mine in higher frequencies including the bump around 3.5 kHz and peaking at the end.
We can look at my near-field measurements for how the crossover responds (these were done WITHOUT the grill):
Overall integration of drivers seems fine to me. The main issue I see is the non-flat response of the tweeter.
Back to our spin data, my measurements are 360 degrees so we have our usual graphs even though some of it such as rear wall reflections are not appropriate here:
If we took that out, the tilt would be less. The same applies to predicted in-room response:
This looks good to me.
Impedance graph shows the issues in bass with respect to enclosure leakage:
Ignoring that, I am surprised at the very low impedance of just 2.9 ohm. I compared that to the company measurements and it matches. So whatever amp you are going to use these is going to work hard as far as current delivery and may even shut down if you use these as your fronts in home theater application.
Distortion graphs look good considering the vagaries of the backbox I built:
Beamwidth seems to be nice as delivered by the mid-range and some of the tweeter:
I don't have an explanation for heavy beaming of the tweeter above 10 kHz other than it being impacted by measurement error. Anyone has other ideas?
Note that anything past 90 degrees is of no consequence in real use which is also noted in the directivity graphs:
Figuring out what is going on in the vertical directivity plot would probably takes weeks of research.
I did not have time to listen to the thing. I got bruised up building the box in my unfinished wood shop so decided to just publish the measurements.
Conclusions
There are a ton of factors here relative to how we are testing and how the speaker will be used. If we take the approximation as presented, performance seems reasonable. Most in-wall speakers are built to a price and have horrible performance. Such doesn't seem to be the case here.
I am open to suggestions of how to vary or improve the setup for future testing. In-wall speakers are a huge category and would be good to have a standardized method of testing them that is reasonable, defensible and not very time consuming to build.
------------
As always, questions, comments, recommendations, etc. are welcome.
Getting killed around the house with various chores. The stupid dryer decided to break its own trim mount resulting in two hours of cursing to remove the trim, glue it back up to assemble later. By then it was hot but I had no choice to go in the yard and deal with all the damage done to our corn plants by rabbit or some other animal. The darn think ate the stock right at the ground and left 99% of the plant to die. Noticed racoons are going after our prized cherries so have to go out now at 8:30 pm and harvest what I can before they eat them all tonight!!!
Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
This is the first in-wall speaker we are measuring so I had to go through some prep to test it. Between the owner and I, we decided to build a back box using 2x4 American studs. The THX-365IW is made to hold on to drywall or plywood so I built the latter from scraps I had in my woodshop:
As you can see, the baffle is wider than the frame I built to give it some (small) approximation of it mounting on full wall. Clearly this is a compromise as making this much bigger would make it much heavier and harder to measure. I chose to not seal the back box enclosure as in typical application of it just mounted to a well, it enjoys a very large space behind it. I figured allowing leakage would reduce the back pressure on the driver. Good or bad decision? I let you all comment. I confirmed during testing that copious amount of air was leaking around the 2x4 framing.
In addition, I made the executive decision to use the metal, magnetically attached grill as I doubt anyone would use such with exposed drivers. Speaking of which, this is a 3-way design with dual woofers:
Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors enable testing in ordinary rooms yet results that can be more accurate than an anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.
I performed over 1000 measurement which resulted in error rate of less than 1% below 10 kHz. Above that error shot through the roof so that area of the response is likely not reliable.
Reference axis was the tweeter center. I also tested it with mid-range being such but it did not make much of a difference.
Monoprice THX-365IW Measurements
Acoustic measurements can be grouped in a way that can be perceptually analyzed to determine how good a speaker is and how it can be used in a room. This so called spinorama shows us just about everything we need to know about the speaker with respect to tonality and some flaws:
The graph is pretty unsettling at first blush. The low frequency variations though I believe due to leaky back box. Actual response in room will be different both because of that and room variations. Its level is higher than the rest of the response. Company produces its own measurements which we can compare:
Alas, they don't list any conditions as to how the test was done. The low frequency response is indicated as "near-field" which tells me is not anechoic. There is decent correlation between theirs and mine in higher frequencies including the bump around 3.5 kHz and peaking at the end.
We can look at my near-field measurements for how the crossover responds (these were done WITHOUT the grill):
Overall integration of drivers seems fine to me. The main issue I see is the non-flat response of the tweeter.
Back to our spin data, my measurements are 360 degrees so we have our usual graphs even though some of it such as rear wall reflections are not appropriate here:
If we took that out, the tilt would be less. The same applies to predicted in-room response:
This looks good to me.
Impedance graph shows the issues in bass with respect to enclosure leakage:
Ignoring that, I am surprised at the very low impedance of just 2.9 ohm. I compared that to the company measurements and it matches. So whatever amp you are going to use these is going to work hard as far as current delivery and may even shut down if you use these as your fronts in home theater application.
Distortion graphs look good considering the vagaries of the backbox I built:
Beamwidth seems to be nice as delivered by the mid-range and some of the tweeter:
I don't have an explanation for heavy beaming of the tweeter above 10 kHz other than it being impacted by measurement error. Anyone has other ideas?
Note that anything past 90 degrees is of no consequence in real use which is also noted in the directivity graphs:
Figuring out what is going on in the vertical directivity plot would probably takes weeks of research.
I did not have time to listen to the thing. I got bruised up building the box in my unfinished wood shop so decided to just publish the measurements.
Conclusions
There are a ton of factors here relative to how we are testing and how the speaker will be used. If we take the approximation as presented, performance seems reasonable. Most in-wall speakers are built to a price and have horrible performance. Such doesn't seem to be the case here.
I am open to suggestions of how to vary or improve the setup for future testing. In-wall speakers are a huge category and would be good to have a standardized method of testing them that is reasonable, defensible and not very time consuming to build.
------------
As always, questions, comments, recommendations, etc. are welcome.
Getting killed around the house with various chores. The stupid dryer decided to break its own trim mount resulting in two hours of cursing to remove the trim, glue it back up to assemble later. By then it was hot but I had no choice to go in the yard and deal with all the damage done to our corn plants by rabbit or some other animal. The darn think ate the stock right at the ground and left 99% of the plant to die.
Noticed racoons are going after our prized cherries so have to go out now at 8:30 pm and harvest what I can before they eat them all tonight!!!Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
