This is a review and detailed measurements of the Ascend Audio CMT-340 Signature Edition Center Channel Speaker. It is on kind loan from a member. The CMT-340 SE costs US $298 from the company plus $30 in shipping. It looks to be a design that was released 10 to 15 years ago but of course, speakers don't age like electronics.
The speaker is too big to put in my photo booth so here is a picture of it from the company:
This is the classic "MTM" configuration which stands for Mid-woofer, Tweeter, Mid-woofer. These quickly became popular with the advent of home theater and the need for a not so tall speaker to put under or over the TV or projection screen. The second mid-woofer was added versus a 2-way design to get increased power capability as the speaker has to keep up with the Left and Right units. MTM configuration works fine as a vertical speaker but when placed on the side this way, creates off-axis radiation which has a cancellations varying distance between the drivers and listeners. We will see this in measurements.
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. 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 anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room. All measurements are reference to tweeter axis with the grill removed.
Around 1000 points around the speaker were measured (from 20 to 20 kHz) which resulted in well under 1% error in identification of the sound field in all but the 8 to 10 kHz where the error is about 2% due to complexity of the soundfield (see the eye candy section). Final database of measurements and data is 1.4 Gigabytes in size.
Spinorama Audio Measurements
Acoustic measurements can be grouped in a way that can be perceptually analyzed to determine how good a speaker can be used. This so called spinorama shows us just about everything we need to know about the speaker with respect to tonality and some flaws:
Research says that on-axis, i.e. the sound that comes to you if you point the speaker directly at you (as would be the case in center speakers) should be as flat as possible. I have shown this in red arrow. We don't see that here with a dip in upper bass, followed by a peak around 1 kHz, then a dip and so on. Company talks about having compensated by the usually poor horizontal dispersion of MTM. I am wondering if the peak around 1 kHz is their attempt at such a fix.
We see our MTM problem clearly in Directivity Index:
Focusing on the blue dashed line, research says that should be smooth, i.e. no variations up and down. It can have some title though as I have indicated with my red arrow. We see a large deviation around 3 to 4 kHz. That says that the off-axis response varies a lot from on-axis. So the sound that bounces around the room versus the one coming at you directly have different tonality. Our poor brain then has to figure out what the sum of that mess is and likely thinks the sound is colored, with a suck out in that region. In a center channel speaker, you don't to see such a dip as that is the upper range for vocals.
This also means the speaker will have room dependence as what reflects from the environment changes it sound. Equalization cannot in theory fix any of this because it is before the speaker and whatever it does, changes both on-axis and off-axis at once so the difference between them remains (bad). Controlled listening tests though have shown that some improvement can be made by boosting that area. So you can try but best to listen before and after to make sure it did make things better.
We can put the whole recipe together and guestimate what sound you may get in your room:
Ideal response again looks more or less like the arrow I have drawn. More bass than treble but otherwise smooth graph. We have the overall tilt so this speaker should not sound too bright but we don't want the variations we see. We also have a dip in bass frequencies which may take away "warmth" from the speaker. There, I used that subjectivist word!
We are done. The rest is for speaker nerds.
Basic Speaker Measurements
Impedance graph shows that this speaker is harder to drive than the company implies:
There are also some "kinks" int he graphs that indicates presence of resonances but they are also visible in the spinorama measurements already sown.
I am trying to standardize the distortion measurements as the software always autoscales this graph:
I picked 5% as the upper limit. If I set that too low it will clip distortion peaks in other speakers. Let me know if you want something else and why.
And here is our waterfall which as noted is not anechoic measurements like spinorama is. As such, I have gated the response in time, reducing or ruining low frequency resolution.
Advanced Speaker Measurements
Notice the narrow angle after which, response falls apart horizontally:
Eye Candy Measurements
I was surprised that the measurement system had a hard time in the region of 8 kHz, sampling the soundfield despite 1000 point measurement system. So i zoomed there and found this:
Frequencies below and after show simple sound fields as we would expect. At 8 kHz though, we have countless sound sources. I suspect both woofers are still playing and we have diffraction from all corners of the speaker combining.
Conclusions
I don't expect many of you to have interest in this speaker but reviewing it is good because it shows all the classic issues with MTM speakers. There are ways to optimize them better than we see here but ultimately the (near) best solution is to add a mid-range to it. See my measurements of the Revel C52 with that addition: https://www.audiosciencereview.com/...el-c52-speaker-review-and-measurements.10934/
People normally think only the dialog comes out of the center speaker in movies but that is not so. The center channel carries vast majority of burden including sound effects as it represents the center of the image on screen where the action is. So whatever you do, don't skimp on center speaker. Get the best one you can. In the case of MTM, see if you can place them vertically. That is what I did with my first dedicated theater.
So overall, despite the reasonable price, I would not recommend this center speaker.
------------
As always, questions, comments, recommendations, etc. are welcome.
Don't make me tell you another bad joke to get you to donate money. Do it on your own by using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
The speaker is too big to put in my photo booth so here is a picture of it from the company:
This is the classic "MTM" configuration which stands for Mid-woofer, Tweeter, Mid-woofer. These quickly became popular with the advent of home theater and the need for a not so tall speaker to put under or over the TV or projection screen. The second mid-woofer was added versus a 2-way design to get increased power capability as the speaker has to keep up with the Left and Right units. MTM configuration works fine as a vertical speaker but when placed on the side this way, creates off-axis radiation which has a cancellations varying distance between the drivers and listeners. We will see this in measurements.
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. 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 anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room. All measurements are reference to tweeter axis with the grill removed.
Around 1000 points around the speaker were measured (from 20 to 20 kHz) which resulted in well under 1% error in identification of the sound field in all but the 8 to 10 kHz where the error is about 2% due to complexity of the soundfield (see the eye candy section). Final database of measurements and data is 1.4 Gigabytes in size.
Spinorama Audio Measurements
Acoustic measurements can be grouped in a way that can be perceptually analyzed to determine how good a speaker can be used. This so called spinorama shows us just about everything we need to know about the speaker with respect to tonality and some flaws:
Research says that on-axis, i.e. the sound that comes to you if you point the speaker directly at you (as would be the case in center speakers) should be as flat as possible. I have shown this in red arrow. We don't see that here with a dip in upper bass, followed by a peak around 1 kHz, then a dip and so on. Company talks about having compensated by the usually poor horizontal dispersion of MTM. I am wondering if the peak around 1 kHz is their attempt at such a fix.
We see our MTM problem clearly in Directivity Index:
Focusing on the blue dashed line, research says that should be smooth, i.e. no variations up and down. It can have some title though as I have indicated with my red arrow. We see a large deviation around 3 to 4 kHz. That says that the off-axis response varies a lot from on-axis. So the sound that bounces around the room versus the one coming at you directly have different tonality. Our poor brain then has to figure out what the sum of that mess is and likely thinks the sound is colored, with a suck out in that region. In a center channel speaker, you don't to see such a dip as that is the upper range for vocals.
This also means the speaker will have room dependence as what reflects from the environment changes it sound. Equalization cannot in theory fix any of this because it is before the speaker and whatever it does, changes both on-axis and off-axis at once so the difference between them remains (bad). Controlled listening tests though have shown that some improvement can be made by boosting that area. So you can try but best to listen before and after to make sure it did make things better.
We can put the whole recipe together and guestimate what sound you may get in your room:
Ideal response again looks more or less like the arrow I have drawn. More bass than treble but otherwise smooth graph. We have the overall tilt so this speaker should not sound too bright but we don't want the variations we see. We also have a dip in bass frequencies which may take away "warmth" from the speaker. There, I used that subjectivist word!
We are done. The rest is for speaker nerds.
Basic Speaker Measurements
Impedance graph shows that this speaker is harder to drive than the company implies:
There are also some "kinks" int he graphs that indicates presence of resonances but they are also visible in the spinorama measurements already sown.
I am trying to standardize the distortion measurements as the software always autoscales this graph:
I picked 5% as the upper limit. If I set that too low it will clip distortion peaks in other speakers. Let me know if you want something else and why.
And here is our waterfall which as noted is not anechoic measurements like spinorama is. As such, I have gated the response in time, reducing or ruining low frequency resolution.
Advanced Speaker Measurements
Notice the narrow angle after which, response falls apart horizontally:
Eye Candy Measurements
I was surprised that the measurement system had a hard time in the region of 8 kHz, sampling the soundfield despite 1000 point measurement system. So i zoomed there and found this:
Frequencies below and after show simple sound fields as we would expect. At 8 kHz though, we have countless sound sources. I suspect both woofers are still playing and we have diffraction from all corners of the speaker combining.
Conclusions
I don't expect many of you to have interest in this speaker but reviewing it is good because it shows all the classic issues with MTM speakers. There are ways to optimize them better than we see here but ultimately the (near) best solution is to add a mid-range to it. See my measurements of the Revel C52 with that addition: https://www.audiosciencereview.com/...el-c52-speaker-review-and-measurements.10934/
People normally think only the dialog comes out of the center speaker in movies but that is not so. The center channel carries vast majority of burden including sound effects as it represents the center of the image on screen where the action is. So whatever you do, don't skimp on center speaker. Get the best one you can. In the case of MTM, see if you can place them vertically. That is what I did with my first dedicated theater.
So overall, despite the reasonable price, I would not recommend this center speaker.
------------
As always, questions, comments, recommendations, etc. are welcome.
Don't make me tell you another bad joke to get you to donate money. Do it on your own by using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
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