Monoprice Monolith 15" THX Ultra Review

[Danzilla31]

Sorry James, I have to disagree with that statement. A stiffer and denser material like HDF would reduce cabinet resonance! I agree that the stiffer/denser walls would result in a stronger reflected signal inside the cabinet (or more internal resonance). Speaker design has always suggested the more rigid the cabinet the better. IOW, minimize cabinet resonance and deal with the interior reflections in a different manner.

Based on your post, one might infer that the Monoliths are less well damped than MDF subs, and I doubt that is the case. I'm guessing they address the damping in a very competent way (based on the other indications of high quality design/engineering). Whether the differences are audible is an entirely different issue.
You would know! How well damped are the Monoliths?

Also, I think it is worth stating we are talking theory here. I'm not at all sure that the advantages of MDF outweigh the disadvantages in practice. Certainly it is not a feature to base a buying decision on and a thicker MDF wall/baffle would be better (more rigid) than thin HDF.

Actually, if I had to address this issue professionally, I bet you could, with some measurement, determine a conversion factor such as a thickness of 1.00" of HDF = 1.15" of MDF to establish equivalency of mechanical properties (to be clear, that is a made up number just to demonstrate what I mean).

Well everybody is talking both on reviews and with consumers and the online forums about how good they soun. So I guess HDF can't be all that bad

 

[everettT]

I've seen a couple threads here and on Avs but nothing like the hundreds of posts about the regular ID companies and even in those threads even after universal acclaim people still have doubts. I've also never seen anyone recommend a Monoprice sub in any of the 'which sub' threads.

Personally I can say that the huge size/weight is something of a blocker for me, its the same reason I rule out the monster subs from other companies, but with these a 10-12, 13=15 and 15=18 or even more.

Monoprice probably do quite well with other products, but if they got some marketing people who had a forum presence, like the founders of ID companies, and spread the word, then I bet they would sell a lot more, the product is definitely superior to almost any competitor.

For a first run product, I'd say they have gotten a lot of attention. I think your going to see Monoprice make a more active presence in audio, and I'd look at CES this year as possible introduction.

 

[Defcon]

The question is whether the increased stiffness is audible or even measurable.

For that matter, why aren't subs made using injection molded plastic? Which is much lighter and just as stiff isn't it - its used in pro loudspeakers which have stringent standards and measurements, much more than any so called 'hi fi' speaker.

It seems to me that the massive size/weight of HT subs is just used as an indicator of prestige and value - big and heavy == more valuable. And plastic == cheap.

The ID craze was started by Svs (and Hsu) using subs made out of sonotubes - certainly not wood. And there was absolutely nothing wrong with them.

 

[Defcon]

Well everybody is talking both on reviews and with consumers and the online forums about how good they soun. So I guess HDF can't be all that bad

Its certainly a selling point. However I suspect thats all it is. The designers could've used a lighter material like balsa/ply which is used in many high end subs for exactly this reason - to reduce weight.

 

[KEW]

The question is whether the increased stiffness is audible or even measurable.

Absolutely no question that the increased stiffness is measurable.
Whether it is audible (as it is used in the sub) is an entirely different question. However If the designer wants a stiffer cabinet, he has several choices. He can make the wall thicker, add bracing, add curvature to the wall, or reduce the dimensions, it just depends on which trade-offs he wants to take.
I believe the take-away should be that HDF adds nothing unique to the performance, it is one of many alternative approaches to improving stiffness!

For that matter, why aren't subs made using injection molded plastic? Which is much lighter and just as stiff isn't it - its used in pro loudspeakers which have stringent standards and measurements, much more than any so called 'hi fi' speaker.

Which Pro Loudspakers?
I have several pro studio monitors and they are all MDF. Some (like the JBL LSR305) do have plastic baffles in front and most have the metal plate of the amp spanning the back.
I believe the reason for the plastic baffle is they can economically mass produce the shape to accommodate wave guides (my Klipsh home audio speakers have a plastic baffle).
I think pro audio puts a high value on portability, so plastic (with ribs molded in to create the needed stiffness) for weight reduction makes sense. Ideally, they would use injection- molded foamed plastic with counter pressure to get sealed surfaces with plenty of air pockets inside the plastic (to keep the weight down).
That is the thing about plastic, it can have a lot of properties designed into it (including fiber glass such as the handles often used for hammers). There is cheap basic plastic, then there are highly engineered plastics!
My best studio monitors are Focal Twin 6Be and, aside from the metal plate/heat-sink on back, they are all MDF!

The ID craze was started by Svs (and Hsu) using subs made out of sonotubes - certainly not wood. And there was absolutely nothing wrong with them.

I did not know that Hsu and SVS started out with sonotube subs - cool!
Good question!
However, it is important to understand the strength of a cylinder vs a box. This is a huge factor!
I think we intuitively understand this - consider a tube from a toilet paper roll. If you seal the far end with your hand and attempt to blow it up like a balloon, you will do nothing obvious.
If you had a similar sized (and wall thickness of cardboard) tube with a square cross section, I think you recognize that you could get the flat walls to bulge or "balloon" out!
This is why all LP gas tanks are cylindrical and truly high pressure tanks are spherical. If square, the bulging/flexing due to pressure changes would result in stress concentrations and fatigue failures at the wall edges/corners. With a cylinder the only stress is the wall being "stretched" in tension, trying to expand the circle (like a balloon expands as the rubber is stretched). That won't happen very easily, even with a cardboard sonotube. Building a box as rigid as a cardboard sonotube is no easy feat. You certainly could not expect a box made of flat cardboard the same thickness as a sonotube to be stable!

Edit: Since we are talking subwoofers, I should add that we are not just talking about pressure, but also pulling suction on the walls. However the strength benefits of a circular cross section in suction are the same as when pressurized. The important thing is that the suction is in the air so it pulls equally all the way around the periphery.
A fun demo of this (especially if you have a kid) is to take a couple of small eggs out in the yard and wrap your hand completely around them then gradually squeeze to crush them. Be sure to squeeze as evenly all of the way around the egg as you can. You will be amazed at how strong the egg shell is under this load (of course we are not very good at applying even pressure on the entire exterior of the egg). We know how easy it is to crush an egg if you press into it with your thumb, but airwaves will apply the pressure evenly.
Mechanically, pressure from the exterior is the same loading as suction from the interior. For a pressure vessel (which is much of what a sub cabinet is) it is only about the difference of pressure between the inside and the out!

 

[William Lemmerhirt]

I’ve heard some plastic speakers and it seems like they allow as much sound to pass through the sides and back as much as the drivers!

As far as equating heavy with value, I suppose that’s a natural thing. Iirc, I’ve read where some companies added weight to amplifiers to make them seem more valuable.
I don’t think though, that the point of manufacturing subwoofers with extra weight, just for the sake of it, or to seem more valuable makes any sense at all. That just seems stupid. Think about how much ID companies spend shipping to and fro.

Personally I feel that having as inert a cabinet as possible makes sense and hdf seems to be a good means to that end, although likely unnecessary, as mdf seems to have struck a great balance for a loooooooong time.

 

[snakeeyes]

Well making them heavier than necessary makes them harder to move around the room. Also shipping heavier items costs more.

 

[Defcon]

Absolutely no question that the increased stiffness is measurable.
Whether it is audible (as it is used in the sub) is an entirely different question. However If the designer wants a stiffer cabinet, he has several choices. He can make the wall thicker, add bracing, add curvature to the wall, or reduce the dimensions, it just depends on which trade-offs he wants to take.
I believe the take-away should be that HDF adds nothing unique to the performance, it is one of many alternative approaches to improving stiffness!


Which Pro Loudspakers?
I have several pro studio monitors and they are all MDF. Some (like the JBL LSR305) do have plastic baffles in front and most have the metal plate of the amp spanning the back.
I believe the reason for the plastic baffle is they can economically mass produce the shape to accommodate wave guides (my Klipsh home audio speakers have a plastic baffle).
I think pro audio puts a high value on portability, so plastic (with ribs molded in to create the needed stiffness) for weight reduction makes sense. Ideally, they would use injection- molded foamed plastic with counter pressure to get sealed surfaces with plenty of air pockets inside the plastic (to keep the weight down).
That is the thing about plastic, it can have a lot of properties designed into it (including fiber glass such as the handles often used for hammers). There is cheap basic plastic, then there are highly engineered plastics!
My best studio monitors are Focal Twin 6Be and, aside from the metal plate/heat-sink on back, they are all MDF!


I did not know that Hsu and SVS started out with sonotube subs - cool!
Good question!
However, it is important to understand the strength of a cylinder vs a box. This is a huge factor!
I think we intuitively understand this - consider a tube from a toilet paper roll. If you seal the far end with your hand and attempt to blow it up like a balloon, you will do nothing obvious.
If you had a similar sized (and wall thickness of cardboard) tube with a square cross section, I think you recognize that you could get the flat walls to bulge or "balloon" out!
This is why all LP gas tanks are cylindrical and truly high pressure tanks are spherical. If square, the bulging/flexing due to pressure changes would result in stress concentrations and fatigue failures at the wall edges/corners. With a cylinder the only stress is the wall being "stretched" in tension, trying to expand the circle (like a balloon expands as the rubber is stretched). That won't happen very easily, even with a cardboard sonotube. Building a box as rigid as a cardboard sonotube is no easy feat. You certainly could not expect a box made of flat cardboard the same thickness as a sonotube to be stable!

Edit: Since we are talking subwoofers, I should add that we are not just talking about pressure, but also pulling suction on the walls. However the strength benefits of a circular cross section in suction are the same as when pressurized. The important thing is that the suction is in the air so it pulls equally all the way around the periphery.
A fun demo of this (especially if you have a kid) is to take a couple of small eggs out in the yard and wrap your hand completely around them then gradually squeeze to crush them. Be sure to squeeze as evenly all of the way around the egg as you can. You will be amazed at how strong the egg shell is under this load (of course we are not very good at applying even pressure on the entire exterior of the egg). We know how easy it is to crush an egg if you press into it with your thumb, but airwaves will apply the pressure evenly.
Mechanically, pressure from the exterior is the same loading as suction from the interior. For a pressure vessel (which is much of what a sub cabinet is) it is only about the difference of pressure between the inside and the out!

A cylindrical, or arch, shape has much higher structural integrity and strength. This is well known and in fact the use of arches by the Romans was a key innovation that allowed them to construct a lot of their famous architecture.

The question is why are subs, for who the only concern is cabinet volume, made using square cabinets and not cylinders, esp sonotubes, which are so much lighter, cheaply available as they are used in construction everywhere so you can get one in literally any length/size/thickness, and is so well suited. There is no flexing, no joints, not even much bracing needed, just mount a driver and some ports and you're done - which is exactly the design of the cylinder subs.

I believe the answer is obviously that a tall cylinder doesn't look as premium as a big imposing square box weighing 100lb.

 

[Defcon]

I’ve heard some plastic speakers and it seems like they allow as much sound to pass through the sides and back as much as the drivers!

As far as equating heavy with value, I suppose that’s a natural thing. Iirc, I’ve read where some companies added weight to amplifiers to make them seem more valuable.
I don’t think though, that the point of manufacturing subwoofers with extra weight, just for the sake of it, or to seem more valuable makes any sense at all. That just seems stupid. Think about how much ID companies spend shipping to and fro.

Personally I feel that having as inert a cabinet as possible makes sense and hdf seems to be a good means to that end, although likely unnecessary, as mdf seems to have struck a great balance for a loooooooong time.

Why would wood have better sound properties? I can understand that its needed for musical instruments because e.g in a violin, the reverberations are critical and wood can do that properly. For a speaker/sub, the goal is to have an inert cabinet. I'm sure plastic can be made with any property needed so if insulation is a goal that can be done. e.g. you can have 2 layers of plastic with a air gap between them for ideal sound insulation. All this is impossible with wood.

w.r.t shipping - consider e.g. if adding 30lb adds 10% to shipping cost but doubles sales volume, its a pretty simple business decision. I don't think its out of the question at all. Its the same reason companies offer fancy finishes like a veneer, which aren't cheap by any means but increase sales.

 

[William Lemmerhirt]

A cylindrical, or arch, shape has much higher structural integrity and strength. This is well known and in fact the use of arches by the Romans was a key innovation that allowed them to construct a lot of their famous architecture.

The question is why are subs, for who the only concern is cabinet volume, made using square cabinets and not cylinders, esp sonotubes, which are so much lighter, cheaply available as they are used in construction everywhere so you can get one in literally any length/size/thickness, and is so well suited. There is no flexing, no joints, not even much bracing needed, just mount a driver and some ports and you're done - which is exactly the design of the cylinder subs.

I believe the answer is obviously that a tall cylinder doesn't look as premium as a big imposing square box weighing 100lb.

I’m going to disagree with the premium look statement. 2/3 of my subs are cylinders and although i would love a custom finish such as gloss black, or beech, or something, I love the form factor much more than a boring old box. I’m surprised they’re not more popular, but I can see where they might seem imposing due to the height taking up airspace.

 

[William Lemmerhirt]

Why would wood have better sound properties? I can understand that its needed for musical instruments because e.g in a violin, the reverberations are critical and wood can do that properly. For a speaker/sub, the goal is to have an inert cabinet. I'm sure plastic can be made with any property needed so if insulation is a goal that can be done. e.g. you can have 2 layers of plastic with a air gap between them for ideal sound insulation. All this is impossible with wood.

w.r.t shipping - consider e.g. if adding 30lb adds 10% to shipping cost but doubles sales volume, its a pretty simple business decision. I don't think its out of the question at all. Its the same reason companies offer fancy finishes like a veneer, which aren't cheap by any means but increase sales.

I’m not saying the properties of wood are automatically better than plastic, but over the years it seems like I’ve read that manufacturers that did dabble in plastic cabs found it more complicated and more costly. I mean there must be a few reasons why everyone is still using wood right?
Plastic probably can be used but it’s hard to say off hand if you could make a cabinet inert enough and still keep it light. Who knows, by the time you’ve used enough plastic in the design it might end up weighing more than wood! Also, a double walled cabinet would be fairly complicated and again, two layers of plastic wouldn’t necessarily be lighter. It might also, but there are a lot of factors.

So are you saying that by simply making a heavier subwoofer, xyz subwoofer company could double its sales because people would perceive it to be more valuable? I’ve been involved in manufacturing and shipping for 15 years, and that just doesn’t make sense.

 

[Defcon]

I’m going to disagree with the premium look statement. 2/3 of my subs are cylinders and although i would love a custom finish such as gloss black, or beech, or something, I love the form factor much more than a boring old box. I’m surprised they’re not more popular, but I can see where they might seem imposing due to the height taking up airspace.

Same here. I rather like the look of a sleek cylinder covered in nice black mesh.

In the early days of Svs when cylinder subs is all they sold, people used to complain about the WAF of these and started demanding more 'traditional' subs. This was before the days of monster boxes and 15/18/24" drivers, 8/10/12" drivers were all that was used. As the company became more successful they started offering box subs which took off and became much more popular because they were seen as more traditional, and I'm sure had a higher profit margin, which is why the cylinder designs were phased out, and more importantly, no one else has bothered to make them.

 

[Defcon]

I’m not saying the properties of wood are automatically better than plastic, but over the years it seems like I’ve read that manufacturers that did dabble in plastic cabs found it more complicated and more costly. I mean there must be a few reasons why everyone is still using wood right?
Plastic probably can be used but it’s hard to say off hand if you could make a cabinet inert enough and still keep it light. Who knows, by the time you’ve used enough plastic in the design it might end up weighing more than wood! Also, a double walled cabinet would be fairly complicated and again, two layers of plastic wouldn’t necessarily be lighter. It might also, but there are a lot of factors.

So are you saying that by simply making a heavier subwoofer, xyz subwoofer company could double its sales because people would perceive it to be more valuable? I’ve been involved in manufacturing and shipping for 15 years, and that just doesn’t make sense.

I don't know what the reality is but things don't make sense to me. What I do know is that home audio, esp the high end, is extremely subjective and is based almost entirely on marketing and impressions rather than data and facts.

There is very little reason for a manufacturer to invest in R&D and try to explore lighter/better materials. At the low end of the consumer market, people just want cheap bluetooth soundbars and speakers for highly compressed mp3 tracks with no dynamic range.

At the high end, its all about looks, which is why all the high end companies go to great lengths to boast about their manufacturing processes using rare grains of woods or exotic materials and all that crap, most of which makes absolutely no difference sonically.

Its the same logic you see in high end smartphones which use glass/metal, the 2 worst materials you can use in a phone vs plastic, which is much more crash resistant and doesn't block signals, simply because they are more 'premium'.

When digital amps came out, they were much lighter and the reviewers all said they just didn't have the 'heft in the sound' which is of course total nonsense, and that they lacked quality construction because they didn't need massive heat sinks and metal plates.

This kind of thing is very common in audio.

 

[William Lemmerhirt]

Same here. I rather like the look of a sleek cylinder covered in nice black mesh.

In the early days of Svs when cylinder subs is all they sold, people used to complain about the WAF of these and started demanding more 'traditional' subs. This was before the days of monster boxes and 15/18/24" drivers, 8/10/12" drivers were all that was used. As the company became more successful they started offering box subs which took off and became much more popular because they were seen as more traditional, and I'm sure had a higher profit margin, which is why the cylinder designs were phased out, and more importantly, no one else has bothered to make them.

Except they never were phased out, and they still make them today. Also, during the same time the cylinder sales were hot, they also made some huuuge box subs with dual 12’s rivaling some of today’s larger subs.
I’ve also built sonosubs and I highly doubt that a box sub has a higher profit margin.

 

[William Lemmerhirt]

I don't know what the reality is but things don't make sense to me. What I do know is that home audio, esp the high end, is extremely subjective and is based almost entirely on marketing and impressions rather than data and facts.



At the high end, its all about looks, which is why all the high end companies go to great lengths to boast about their manufacturing processes using rare grains of woods or exotic materials and all that crap, most of which makes absolutely no difference sonically.



This kind of thing is very common in audio.

You don’t really believe that high end audio is all about looks so you?
Fwiw, I see nothing wrong with a gorgeous finish on speakers, and although it costs more that’s to be expected. It’s like buying super nice travertine tile for you kitchen, instead of vinyl. Works(walks) the same, but looks more elegant.

 

[KEW]

The question is why are subs, for who the only concern is cabinet volume, made using square cabinets and not cylinders, esp sonotubes, which are so much lighter, cheaply available as they are used in construction everywhere so you can get one in literally any length/size/thickness, and is so well suited. There is no flexing, no joints, not even much bracing needed, just mount a driver and some ports and you're done - which is exactly the design of the cylinder subs.

I believe the answer is obviously that a tall cylinder doesn't look as premium as a big imposing square box weighing 100lb.

As an engineer, cylinders are definitely the way to go! They always should offer better performance for less money (or at least should if companies are being "honest" with their pricing)!

Obviously SVS knows exactly which shape of subs sells better since they can directly compare essentially identical PC (ported cylinder) and PB (ported box) subs.
I'm not sure about which is more imposing or looks more powerful, but it doesn't matter, in the end it is an issue of "beauty is in the eyes of the beholder".

It is curious that I have never seen a sealed cylindrical sub!

 

[ryanosaur]

Talking to one of the SVS cats the other day, he mentioned their pres shooting down any possibilty of turning their ultra line into a PC version... it would just be too huge! (I'm envisioning an 18-20"dx66"h tube!). But if you could get that in candy apple red, blackberry pearl, or just piano black... Damn! That would be a statement to have four of those anchoring your room! @Danzilla31, C'mon, I know you'd be there!

Regardless, I like downfiring, and I really want the PC's from SVS. I wish I could still consider a cylinder from Hsu. But the output from the pc's are a little lower than their pb brethren.

 

[William Lemmerhirt]

Talking to one of the SVS cats the other day, he mentioned their pres shooting down any possibilty of turning their ultra line into a PC version... it would just be too huge! (I'm envisioning an 18-20"dx66"h tube!). But if you could get that in candy apple red, blackberry pearl, or just piano black... Damn! That would be a statement to have four of those anchoring your room! @Danzilla31, C'mon, I know you'd be there!

Regardless, I like downfiring, and I really want the PC's from SVS. I wish I could still consider a cylinder from Hsu. But the output from the pc's are a little lower than their pb brethren.

Iirc the ultra cylinders were 46” tall. Not too bad in my estimation. How bout these...

 

[ryanosaur]

Iirc the ultra cylinders were 46” tall. Not too bad in my estimation. How bout these...

That's what Im Talkin A-Bout!!

A sexy polished veneer instead of the worlds most expensive cat-scratcher!

Hell! turn that into a Roman column, Doric or Corinthian styled with custom Capital. *architecturalspazdrool

 

[Defcon]

You don’t really believe that high end audio is all about looks so you?
Fwiw, I see nothing wrong with a gorgeous finish on speakers, and although it costs more that’s to be expected. It’s like buying super nice travertine tile for you kitchen, instead of vinyl. Works(walks) the same, but looks more elegant.

It kind of is all about looks. I believe the point of diminishing returns is far earlier than most people think and there's no way the $100-300k speakers are 100x or even 10x better than a $1k speaker. Many of the ultra high end components also measure horribly and fare poorly in any blind test. There's a reason almost no company in home audio and esp high end will ever list measurements or even specs and their entire marketing/sales is based on selling to people based on their name/status and salesmen pushing the product.

Theres nothing wrong with premium finishes, these are furniture as much as speakers, as long as people understand it does nothing for the sound. I don't want to pay for any of that. Many of the high $$$ speakers contain cheap drivers and gorgeous finishes.