Double mattress listings are a minefield of vague claims, baffling layer diagrams, and spring counts that tell you almost nothing about how a bed actually feels at 2am. If you’ve ever wondered whether “adaptive pocket spring” is just a fancy way of saying “springs,” or whether “medium feel” means anything repeatable from one model to the next, you’re not alone. Australian shoppers tell us the same thing in their DMs for best firmness for side sleepers: the spec sheet reads like a romance novel, not a buying guide. This piece pulls apart the marketing layer, points at the specs that actually affect your sleep, and gives you a clear framework for choosing a mattress that suits your body, your base, and your postcode. We’ll cover spring systems, foam density, edge support, the pairing between a hinged or solid base, how motion transfer behaves for couples, and the practical bits — delivery, setup, and what to do once the box lands at your door in Picton, Wilton, or anywhere across Greater Sydney.

What the Core Specs of a Double Mattress Actually Mean

Most spec sheets hit you with three things: spring type, foam layers, and a “feel” rating. None of these mean what they appear to mean on their own.

A double size mattress built on an adaptive pocket spring system uses individually wrapped coils that move on their own. That’s important for two reasons: pressure relief at the shoulders and hips, and reduced motion transfer when your partner rolls over at 3am. A Bonnell innerspring is a different animal — it’s the older, interconnected coil design that tends to feel bouncier and is often easier on the wallet.

Then there’s the foam. Gel foam and high resilience foam are the two you’ll see most often. Gel foam draws heat away from the body, which matters in a Brisbane summer or a Perth February night. High resilience foam is the denser stuff that holds its shape longer and stops you sinking into a bowl after year two.

Finally, the feel rating. “Medium” sounds definitive, but most retailers use it loosely. Treat it as a starting point, not a verdict. Your weight, your sleeping position, and your base all shift how that medium actually presents.

1. Why Spring Count Alone Is Misleading

Pocket spring counts climb past 1,000 in some queen models. Sounds impressive, but pocket diameter and coil gauge decide whether those springs support you or just look busy on the spec sheet. Ask about gauge before you chase a number.

2. Reading Foam Density Instead of Foam Names

Density (kg/m³) tells you far more than a foam’s brand name. Higher density foams last longer and resist body impressions. If the retailer won’t quote density, that’s a flag.

Matching the Double Mattress to Your Sleep Position

Here’s where it gets personal. The best firmness for side sleepers tends to sit in the medium range — soft enough to cushion the shoulder and hip, firm enough to keep the spine roughly level. Go too firm on a side sleeper and you’ll feel pressure points within ten minutes. Go too soft and your lower back will sag by morning.

Back sleepers usually want a touch more resistance, so a medium-firm build gives the lumbar region something to push against. Stomach sleepers (rarer, but they exist) need a firmer surface to stop the pelvis dipping — though most sleep specialists will gently steer them toward side sleeping for long-term spinal health.

For couples, the calculation shifts again. A double mattress is 138cm wide. That’s tight for two adults who both move around. A pocket spring system with zoned support helps — it isolates movement and gives each sleeper their own comfort zone within that narrower footprint.

Best firmness for side sleepers depends on body weight too. Lighter sleepers often feel a “medium” as firmer than expected. Heavier sleepers compress foams more deeply and may need to edge up to medium-firm to feel supported.

1. The Pressure Point Test You Can Do in 30 Seconds

Lie on your side in the showroom or on the floor model. Slide your hand under the small of your back. If there’s a big gap, the bed’s too firm. If your shoulder jams into the surface without any give, also too firm from best firmness for side sleepers. You want gentle contact and neutral alignment.

2. Zoned Support and Why Couples Care

Zoned pocket spring systems reinforce the lumbar region where most adult bodies carry weight. For couples sharing a double mattress, that zoning keeps both sleepers in alignment regardless of their size difference.

Back Pain from Hard Bed: When Firmness Crosses the Line

Let’s be direct. Back pain situations is far more common than the marketing suggests. A surface that’s “orthopaedic” or “extra firm” can absolutely trigger or worsen back pain, especially for side sleepers and lighter-built adults.

For whom looking for the best firmness for side sleepers. Firmness has a ceiling. Beyond that point, your body stops getting pressure relief and starts bracing against the surface all night. Muscles tense, joints compress, and you wake up feeling like you’ve been beaten up. The Australian Physiotherapy Association has long noted that medium-firm surfaces generally outperform extra-firm ones for chronic lower back pain in adult sleepers (2018 position statement, APA).

If you’ve bought a hard bed and your back is complaining, the issue might not be your spine. It might be the surface. A medium-feel pocket spring or hybrid build often resolves back pain from hard bed complaints within a few weeks, especially when paired with a solid base that doesn’t add flex.

Worth noting: a single mattress mattress won’t replace physio treatment. Your mileage may vary, and a chat with a physio is never wasted. But the bed is the first variable to rule out.

A divan bed mattress setup typically pairs with a sprung-edge divan, which adds a touch of bounce and softness. A solid base mattress pairing (think platform or solid slat) lets you feel more of what the mattress is doing. For back pain sufferers, a solid base with a medium pocket spring build is often the cleanest answer.

Hinged Bed Mattress Considerations for Storage

A hinged bed mattress — typically an ottoman or gas-lift frame — needs a flexible enough mattress to bend slightly during lift. Most medium pocket spring builds handle this fine, but check the warranty terms before committing.

Double Mattress Comparison: iSLEEP EZEE vs iSLEEP DELUXE

Both Restmaker doubles sit in the medium feel range and both carry the brand’s core engineering approach — Australian-designed with support for best firmness for side sleepers, built to proprietary specs, layered for comfort and support. The differences come down to construction and budget.

iSLEEP EZEE uses an adaptive Bonnell innerspring system with a smooth top panel. It’s the lighter, more accessible build in the line — well-suited to guest rooms, kids moving up from a single, or anyone who wants a reliable medium feel without the spring count climbing higher than they need.

iSLEEP DELUXE upgrades to an adaptive pocket spring core with a Euro top panel, gel foam, and bamboo fabric cover. The pocket springs give you that independent coil action — better motion isolation for couples and more nuanced pressure relief across zones.

Tradeoff is straightforward: the EZEE wins on price and simplicity; the DELUXE wins on motion isolation, pressure zoning, and premium-feel materials. If you’re a solo sleeper on a budget, the EZEE makes sense. If you’re sharing the bed or you’ve got back pain from hard bed history, the DELUXE pocket spring build is worth the step up.

Couples and Motion Transfer on a Double Mattress

Couple mattress motion issues on a double size mattress are amplified by the narrower surface. Every movement crosses into your partner’s space. There’s no magical fix, but pocket spring systems help meaningfully.

Individual coils absorb movement locally instead of transferring it across the bed (back pain from hard bed). If your partner is a restless sleeper or you have different work schedules, that isolation matters. Bonnell systems are bouncier by design — fine for a guest room, less ideal when one of you is up at 5am.

Edge support is the other piece couples forget. A bed where you roll toward the edge and feel yourself tipping off the bed isn’t usable across its full 138cm width. Reinforced edges on a pocket spring build let you sleep right to the perimeter without losing the sense of a stable surface.

Practical advice: if you’re sharing a double, look for pocket spring construction, check edge support specs, and seriously consider whether a Queen might serve you better long-term. The 30cm of extra width changes everything about how two adults coexist at night.

The 30cm Question: Double vs Queen for Couples

If you’re regularly sharing, a Queen is the right size. Period. A mattress works for occasional guests or very still sleepers, but for nightly couple use, the elbow room matters. It’s one of the few mattress decisions where I give a straight answer without caveats.

Best firmness for side sleepers: Delivery, Setup, and the First 72 Hours

Once your double mattress arrives, the actual setup is the easy part. Here’s a quick checklist you can run through:

1. Carry the box to your bedroom before opening — much easier than dragging the expanded mattress through doorways.
2. Unroll onto your base and cut the outer plastic carefully. Don’t use a long blade near the cover.
3. Let it expand for 24–72 hours before sleeping on it. The foam needs air to fully loft.
4. Keep the room ventilated during that window, especially in summer — off-gassing is mild but real.
5. Rotate 180° after the first month once you’re sleeping on it regularly to even out early compression.

Delivery to Picton, Wilton, Macarthur, the Southern Highlands, and across Greater Sydney (South West, Western, Southern, Inner West, City, Eastern Suburbs, North Shore) is free. Use the postcode calculator on the product page for other regions — most metro and regional postcodes are covered, though some remote locations may have surcharges or longer lead times. The 100-night trial kicks in from delivery day, so you have proper time to test the feel and the support against your usual sleep patterns.

Conclusion

A double mattress decision comes down to three things: how the spring system handles your body weight and sleep position, whether the foam layers will still feel supportive in year three, and how well it pairs with your existing base. Forget the marketing layer. Look at coil type, foam density, edge reinforcement, and warranty length. If you’ve got back pain from hard bed history, lean toward a medium pocket spring build on a solid base. If you’re a side sleeper chasing the best firmness for side sleepers, medium with zoned support is your safest bet. Restmaker’s iSLEEP range is engineered in Sydney by a team with over 25 years of mattress industry experience, built to proprietary specs, and backed by a 100-night trial on every mattress. Pick the model that fits your sleep, claim the trial, and give yourself a proper month to feel it out before deciding.