Monoprice THX-365IW Review (In-wall Speaker)

[amirm]

ASR stands for excellence in measurement, and in most product categories you've provided state of the art measurement and analysis. This particular one does not really meet the standard; it's somewhat revealing if you really know what to look at but I don't think a layperson could use it to decide what to buy.

You are doing a good job of shaming me to spend more to do better. Question is though, to the extent I don't spend more, do we give up on the category? Surely this level of data is far, far better than nothing. In-wall speakers are where major acoustic crimes are committed. Even a less than ideal spin will be very revealing. Here is an example of an offering from a "high-end" speaker company:

Pretty sure current system is capable of showing this level of flaws.

 

[Newman]

Why show a graph and not name the product or tester?

 

[amirm]

Why show a graph and not name the product or tester?

Neither is necessary to make the point I was trying to make. How many places do you know that generate this type of spin data???

 

[GXAlan]

I am surprised at the very low impedance of just 2.9 ohm.

In the old Lucasfilm era when THX became THX Ultra and then Ultra II, I recalled the multichannel amps/receivers were all supposed to be 3.2 ohm stable. I wonder if the current THX spec still has that requirement and potentially may be a reason why this speaker is designed that way. Movies are all about headroom and if your THX everything setup can eek out more power for a given sensitivity, why not?

 

[johnk]

I have a pair of Q Acoustics QI65RP in wall speakers for my kitchen. I need to find time to measure them, but they seem very light on the bass. They look great. I wonder if adding a box or more insulation will help with the bass

 

[Francis Vaughan]

Surely this level of data is far, far better than nothing. In-wall speakers are where major acoustic crimes are committed.

In principle, done right, in wall offers significant advantages over any box or baffle design. But our modern life and houses are rather limiting in making use of this. Measuring in-wall speakers is important.

But indeed, I agree, we can learn pretty much everything we need to know with the existing tests. There are no baffle step problems in a correct installation, and the bass response is easily obtained by an appropriate allowance for half space radiation. The baffle step existing in the test fixture can be corrected for as well. What is arguably needed is a well characterised and blameless test fixture. That is, blameless except for the known baked in baffle dimension related disturbances.

Blameless is why I keep harping on building the fixture solidly, sealed, and in addition, removing the cavities on the edges, given they can be blamed for additional oddities in the response.

The rear of the fixture is the interesting question. House walls have all manner of construction. An interior wall is likely to be dry-wall or plywood on both sides. so that would a reasonably representative thing to do. But external walls may be almost anything, from flimsy board to brick, Hebel, concrete. So a rear face of something much more soild and resonance free would be reasonable in the fixture. However in order to avoid any further confusion of the measured response, a solid rear face would likely be the better choice.

If best practice is to add some fibreglass, that should probably be included in the test protocol.

In the end, the test should give the speaker the best chance, and avoid acusations that the test protocol is the cause of anomalies.

 

[Helicopter]

This is an important category. The suite we have here is not just 'better than nothing;' it is adequate and will work fine for informing consumers about the product.

If good sound or great sound can be had, the advantages are very strong in the category.

Sometimes a picture is worth a thousand words:

(Pro tip: tell contractor to put tweeters at ear height while seated.)

The measurement suite here is flawed only compared to nearly perfect cabinet speaker measurements. If you were to have a handful of comparable measurements like this in the category, it could be incredibly useful. It would be great to see what the consumer gets at a few price points and configurations with Revel, JBL, and Focal.

Obviously Erin's setup with a cutout in the garage wall resolves most of the issues, but I don't really understand what is needed to make your NFS play nice with a speaker in the wall. If you were to spend even $2k or so, seems the money would be better spent on speakers and shipping to test.

I am really looking forward to that TOTL Revel speaker.

 

[Bear123]

On the *general* topic of in wall speakers, I have in room measurements of Revel W263 speakers full range without eq, along with crossed to subs with Audyssey full range correction. Don't want to post them here in the Monoprice thread, but if it would further the discussion, I'll be glad to start a separate thread if anyone is interested. Revel does have spin data for this speaker. These are Revel's cheapest entry level in walls. Due to the fact that I found it difficult to justify spending more for their higher tier products based on spin data other than some of the highest level offerings, and the fact that I won't be in this house long, I felt these were an adequate choice for surround duty.

 

[Helicopter]

On the *general* topic of in wall speakers, I have in room measurements of Revel W263 speakers full range without eq, along with crossed to subs with Audyssey full range correction. Don't want to post them here in the Monoprice thread, but if it would further the discussion, I'll be glad to start a separate thread if anyone is interested. Revel does have spin data for this speaker. These are Revel's cheapest entry level in walls. Due to the fact that I found it difficult to justify spending more for their higher tier products based on spin data other than some of the highest level offerings, and the fact that I won't be in this house long, I felt these were an adequate choice for surround duty.

Plese do start a thread. Maybe post your measurements and the Harman spin chart. That will be useful, even moreso once Amir has measured the TOTL Revel in-wall speaker so we have a baseline to compare Harman info to Amir's.

 

[somebodyelse]

Could the scanner

View attachment 137445

be placed in front of any baffle? Not having seen it in action—maybe a timelapse video—does the mic move strictly along the orthognal axes or does it described an arc around the DUT?

https://www.audiosciencereview.com/...-on-with-the-klippel-nearfield-scanner.24440/

 

[Stu Pidasso]

Looks like you forgot to take a green sharpie and mark the edge all the way around for better clarity and nuance. ;-P

 

[Stu Pidasso]

Genelecs can be installed inside a wall and there’s a calibration method for that. What more can one need?

Just the cash to buy them!

 

[Thomas_A]

In-between wall-speakers, there are many speakers designed to be placed near-wall or near a damped wall.

In theory, it should be possible for software to recalculate the spin data that includes nearby close-boundaries based on current spin data.

 

[alex1berg]

To a pisher, it might seem that way. For the rest of the people, there is plenty of proper information here.

My temporary teacher in elementary school said, "every classroom needs a clown; don't you try to be the one!" So think hard before you throw out an insult with zero content.

Now I have to google pisher.

 

[hyfynut]

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:

View attachment 137272

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:

View attachment 137273

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:

View attachment 137274

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:

View attachment 137275

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):

View attachment 137277

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:

View attachment 137278

If we took that out, the tilt would be less. The same applies to predicted in-room response:

View attachment 137279

This looks good to me.

Impedance graph shows the issues in bass with respect to enclosure leakage:

View attachment 137280

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:

View attachment 137281

View attachment 137282

Beamwidth seems to be nice as delivered by the mid-range and some of the tweeter:

View attachment 137283

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:

View attachment 137284

Figuring out what is going on in the vertical directivity plot would probably takes weeks of research.

View attachment 137285

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/

Grrat to see a review of an inwall. My biggest suggestion would be to build a much bigger wall to measure them in. I'm assuming they'll measure different in a cavity closer to 16" X 96" with a flange (the drywall) closer to 4 feet. Could be challenging to find a spot for this but that is how they'd be installed and how Ive seen them tested in the past.

 

[Thomas_A]

You are doing a good job of shaming me to spend more to do better. Question is though, to the extent I don't spend more, do we give up on the category? Surely this level of data is far, far better than nothing. In-wall speakers are where major acoustic crimes are committed. Even a less than ideal spin will be very revealing. Here is an example of an offering from a "high-end" speaker company:

View attachment 137470

Pretty sure current system is capable of showing this level of flaws.

As mentioned previously, the spin data should contain all data to simulate or recreate the response of in-wall mounting. If not in the Klippel SW, perhaps someone in the forum could develoo an algorithm?

 

[nathan]

Revel has open back in wall speakers and in reading about their installation recommendations, they make the somewhat reasonable assumption the back will be open to a single bay in a traditional north american house (ie, 3.5" deep, 18" to 24" wide, 8' tall), ie, a 3 to 4 cubic foot space.

They also make an assumption about the minimum baffle size (wall) it will be in, but I can't recall what that was, something like at least 12" in each direction, though their higher end models include EQ switches to compensate if its closer to a corner than that, etc.

I'm not sure how realistic that is for a testing setup since it would effectively mean you have a speaker + enclosure that is 2 feet wide and eight feet tall and sealed on all sides.

But maybe it also means you could construct a backer box of 3 cubic feet that is a more management layout....

 

[nathan]

Well, this is not far from the Revel guidelines (guess that shouldn't be a surprise). Thanks for posting.

Well, the 2034 spec explicitly states how to test an in-wall speaker, which I mentioned earlier but will link again below. It seems they also talk about in-wall speakers that contain enclosures but I'm not 100%. Point being, I don't see the point in Amir reinventing the wheel. The issue is the size of the baffle. But maybe making a scaled down version is OK, and using the NFS template for "baffle" (as I illustrated in an above post) to do the processing.

 

[nathan]

Glad to see this! I mean, Revel publishes spinorama data for these but as a way to perfect Amir's testing approach, yeah!

I just purchased 4x Revel W990's and would be happy to ship one over. They're Revel's top of the line in-wall with a 9" woofer.
https://www.revelspeakers.com/produ...W990-_color=Black-GLOBAL-Current&cgid=in-wall

View attachment 137404

 

[nathan]

2: I remember reading on Monoprices site with questions and reviews they were telling customers you shouldn't build a back box for these as these were designed to be open in the wall they said building a back box would change how the speaker performs. So a sealed box might not be a good idea?

They don't want you to build a back box because they are assuming the 3 to 4 cubic feet of a normal US stud bay.....which is sealed (though not water/air tight, but very close since it is 2x4 framing on all sides and drywall front and back.