Hi swassbac,
The two mattresses you are mentioning are a classic case of “buyer beware” and an example of how misleading various descriptions can be. I’ll break down the description of both of them to highlight what I mean and to show that both of them use low quality/density memory foam. Both of them are sourced in china and are not certified by anyone that I know of in terms of chemicals or offgassing which means that their “safety” is also unknown.
Dynasty Mattress 12":
This uses 5" of memory foam over 7" of poyfoam.
The King size weighs 114.7 lbs (and for the sake of ease I’ll exclude the cover in these calculations which if it was removed would make the shipping weight even lower).
5" x 76" x 80" = 17.59 cu. ft. (cubic ft of the memory foam)
17.59 x 5 lbs/cu.ft = 87.95 lbs. (weight of the memory foam if it was really 5 lbs)
114.7 lbs (total weight) - 87.95 = 26.75 lbs (should be the weight of the base polyfoam)
7" x 76" x 80" = 24.63 cu ft (base polyfoam layer)
26.75 lbs (remaining weight) / 24.63 cu. ft. = 1.09 lbs which should be the density of the base layer if the rest of the stats are correct. This is clearly not the case (or if it was it would be complete “junk” form and a base layer should be at least 1.8 lbs density or at least 1.5 lbs in a lower budget mattress with higher quality comfort layers).
If the memory foam was 4 lbs … then the base layer would work out to 1.8 lbs which is far more likely.
In addition to this … the durability of memory foam is determined by its polymer density. Many lower quality manufacturers will add filler materials to their memory foam to lower the cost and also raise the density of the material so it looks to be higher quality than it is. This addition of particulates (like sand) actually lowers the durability of the memory foam it is added to while also making it firmer.
So this mattress is likely to be a 4 lb memory foam which could be even lower density memory foam with some type of filler added to it (typical of some cheap Asian manufacturers) which would give it the quality/durability of sub 4 lb memory foam which was over a 1.8 lb base layer also of unknown quality. In other words … it is a roll of the dice becaue they don’t disclose which Chinese manufacturer is making their foam. The absolute best case is that it is a basic 4 lb memory foam over a basic 1.8 lb polyfoam. In addition to this … if it really is high quality memory foam … then 5" is a very risky construction (some people would be out of alignment with this much “pure” memory foam depending again on what was in it)
SilverRest Luxury Grand 14":
This is also imported from China.
It uses 6" of memory foam over 8" of polyfoam and weighs 120 lbs.
6" x 76" x 80" = 21.11 cu. ft. (cubic ft of the memory foam)
21.11 x 5 lbs/cu.ft = 105.55 lbs. (weight of the memory foam if it was really 5 lbs)
120.0 lbs (total weight) - 105.55 = 14.45 lbs (should be the weight of the base polyfoam)
8" x 76" x 80" = 28.14 cu ft (base polyfoam layer)
14.45 lbs (remaining weight) / 28.14 cu. ft. = .5 lbs which should be the density of the base layer if the rest of the stats are correct. This also is clearly not the case or it too would be “junk” foam and I doubt they even make foam of this low quality.
This mattress would “work out” if it used about 3 lb memory foam (the base layer would then be about 2.0 lbs) or 3.5 lb memory foam (the base layer would be about 1.6 lbs). Of course the cover looks fancier and is probably more expensive and the mattress is “thicker” overall which means that a higher price can be “justified” even though it may use even lower quality materials than the Dynasty.
Bottom line … these are not the “deal” they appear to be.
Are they “worth” the prices they are charging?
To me the answer to this would depend on many things but one of the most important would be how comfortable someone is with unknown materials that are also unknown in terms of how suitable a particular mattress construction is for their own circumstances (height/weight/body shape/sleeping positions/ preferences) and the cost of returning a mattress if the layering isn’t suitable for you regardless of the quality of the foam.
These two examples are typical of the type of misleading advertising and low quality materials that are flooding the market and people are still buying it because they don’t have the “reference points” to check the claims that are being made.
So hopefully this answers what I “think” of these types of mattresses and “deals”.
I personally would not take the chance either from a perspective of long term safety of from the perspective of using 5" of lower density memory foam for someone who was over 200 lbs. Even someone smaller would likely do much better with a thinner layer of memory foam or at least a different type of layering.
I personally would avoid both of these both because of the quality of the materials, the unknown suitability of the layering, and because I would not want to support any business which represents their product as being something other than they are … regardless of how many people are “happy” because they think they received such a deal, were blinded by the price they paid, and had no way to really know the quality of what they purchased. Even cheap materials can feel good … for a while … especially for someone who is already subjectively predisposed to like it because they think they found such a “bargain”.
Before considering any memory foam mattress … I would make sure it fits the four criteria listed in post #10 here.
Phoenix