Hi GenericMattressShopper,
Thanks for adding the information about Small Wonders to the forum … I appreciate it.
A mattress is just a combination of materials and components used for sleeping on so anything that you sleep on could be called a “mattress” so from this perspective it would “work like a mattress” yes.
Having said that … there could be a number of differences between the DIY system you are considering and a Spindle mattress (or any similar mattress).
The first would be any differences in the firmness of the layers and how well either one of them matched your specific needs and preferences in terms of PPP. If you were to sleep directly on the latex and you purchased a 6" core of 100% natural Dunlop from latextoppers that was the same density and firmness as both of the bottom two 3" layers from Spindle and the topper you purchased was also 100% natural Dunlop and was also the same density/firmness as the top layer in the Spindle then they would feel similar (again as long as you were sleeping directly on the latex with no cover or mattress protector on either of them). If any of the layers in each mattress were different from each other then the mattresses would feel different because every layer and component in a sleeping system will affect the feel and performance of the other layers and components and the mattress as a whole.
Another difference between the two designs (again not taking into account any differences in the covers that you may use yet) would be that a support core of two 3" layers would have more flexibility of firmness choices than a single 6" core and you would have more options to customize the layers both before and after a purchase. There is more about the pros and cons of each in post #2 here.
Any differences in the zoning of the layers may also have an affect on how each of them compare in terms of PPP as well.
Finally there may be a difference in the return or exchange options you would have after a purchase with each of them which may affect the “value” of your purchase if you make a “mistake” in your firmness choices and need a different layer.
Other than any differences in the layers … the cover that you use will also make a difference (and sometimes the amount of difference can be surprising because this is often a forgotten part of a mattress design). There is a difference between a mattress cover that is meant to be used as part of the mattress (also called a ticking), a mattress protector that is meant to protect the sleeping surface of the mattress (including the cover), and a mattress encasement (or allergy encasement or bed bug encasement) that is use to protect against allergens or bed bugs. They are all different products that are designed for different purposes (although there can be some overlap between them).
A mattress cover (ticking) will tightly fit the specific thickness of the materials inside the mattress, help the mattress materials stay together without shifting, and help the mattress keep its shape. It is generally made with a higher quality material that will last for the useful life of the mattress and depending on the type of cover can also have a significant effect on the feel and performance of the mattress and with temperature regulation as well. It can also include the fire barrier of the mattress so it can pass the fire regulations. There is more about different types of covers (stretch knit and quilted) and how they can affect the feel and performance of a mattress in post #12 here and the other posts it links to.
Latex can also oxidize faster with exposure to air and ozone and ultraviolet light along with other substances that can damage it (see here) and it’s always a good idea for a latex mattress to have a dedicated cover to give it the best possible protection and to help maximize it’s useful lifetime. Outside of the fact that a mattress encasement isn’t designed to fit tightly around a mattress … many encasements use a semi breathable membrane that can affect the breathability and temperature regulation of a mattress. A mattress encasement without a membrane (such as a synthetic or natural fiber with small pore sizes) also isn’t designed to fit the mattress exactly and is generally thinner than a mattress cover/ticking and won’t provide the same degree of protection to the materials inside it or be as durable as a mattress cover/ticking. A mattress protector or encasement would offer “some” protection for the latex but it’s a matter of degree. There is more in post #3 here and post #3 here that will give you some sense of the effect of different types of covers on latex.
A mattress protector is meant to protect the mattress and the cover from accidents and stains that come from the body oils and fluids we release each night and to help keep your sleeping surface in a cleaner and more hygienic condition. Unlike a cover or a mattress encasement it is meant to be removed on a regular basis so it can be cleaned. They are generally like a fitted sheet that tucks under the mattress (although some have straps and some just lie on top of the mattress under your sheets). There is more about the pros and cons of different types of mattress protectors in post #89 here.
A mattress encasement is primarily meant to completely enclose the mattress to protect against either allergens and dust mites or against bed bugs and are generally meant to stay on the mattress on a semi permanent basis (and are often used in combination with a mattress protector which can be regularly removed and cleaned). There is more about mattress encasements in post #2 here.
The Spindle mattress uses a high quality wool quilted organic cotton zip cover with the wool acting as both the fire barrier and as a temperature regulator for the mattress. How it would compare to using a different type of cover or a mattress encasement would depend on the specifics of the cover or encasement you were using instead but the information here should give you the information you would need to compare them.
Phoenix