Hi RickNY,
All the layers of a mattress compress simultaneously not sequentially and they will each compress to different percentages of their thickness depending on their position on the mattress, the firmness of each layer, the compression modulus of the material, the thickness of each layer, and the compression force that they are exposed to (which depends on the weight and surface areas of the part of the body in contact with the mattress and the surface area that is bearing that weight which is constantly changing as you sink into the mattress more or change sleep positions). The layers closer to the top will generally compress more than the deeper layers and softer layers will compress more than firmer layers but what you are feeling would be a combination of all the layers and the “mattress as a whole” more than the effects of a single layer. The properties and firmness of materials and components that are closer to the top surface of a mattress will tend to have a bigger effect on the overall “feel” and firmness of a mattress than materials that are deeper in the mattress.
While it’s not possible to “diagnose” mattress comfort issues on a forum with any certainty because there are too many unique unknowns, variables, and complexities involved that can affect how each person sleeps on a mattress in terms of “comfort” and PPP (Posture and alignment, Pressure relief, and your Personal preferences) or any “symptoms” they experience … there is more about the most common symptoms that people may experience when they sleep on a mattress and the most likely (although not the only) reasons for them in post #2 here.
There is also more about primary or “deep” support and secondary or “surface” support and their relationship to firmness and pressure relief and the “roles” of different layers in a mattress in post #2 here and in post #4 here that may also be helpful in clarifying the difference between “support” and “pressure relief” and “feel”.
These posts are the “tools” that can help with the analysis, detective work, or trial and error that may be necessary to help you learn your body’s language and “translate” what your body is trying to tell you so you can identify the types of changes that have the best chance of reducing or eliminating any “symptoms” you are experiencing (at least to the degree that any symptoms are from your mattress rather than the result of any other circumstances or pre-existing issues you may have that aren’t connected to a mattress).
Having said that this type of analysis can be very complex and in the end the only way to know whether any mattress or combination of materials or layers will work well and will be a good “match” for you in terms of PPP with any certainty will be based on your own careful testing or personal experience anyway no matter what type of analysis you have done on the design of a mattress because “theory” doesn’t always predict how well you will sleep on a mattress. The advantage of the simplified choice mattresses (and other online mattresses that have good return policies are that they allow you to test a mattress in your bedroom instead of a showroom with little risk outside of the time you spend sleeping on it or returning/donating it.
While the firmness of your mattress is certainly inside the range that would be suitable for a large percentage of people in your weight range … not everyone is inside the averages that works for other people that have a similar body type or sleeping positions.
It would also be well worthwhile to call talk with Brooklyn Bedding since they would be the best source of guidance about their mattresses and different firmness levels than anyone else and may also have some suggestions that would be helpful based on their experience and feedback from other customers that are similar to you.
Phoenix