If you’ve already purchased the SHC SUB15 DIY Home Cinema Subwoofer Guide, you should receive an email notifying you of the update. The SUB15X plans are included with your original purchase.
Sub15X Overview:
Shortly after releasing the SUB15, we discovered a driver that could significantly Improve its original design. Recognizing this opportunity, we adapted the SUB15 to accommodate the new driver, resulting in the SUB15X.
The SUB15X is equipped with Stereo Integrity’s SQL15 Series 2 driver, which doubles the X-max of the original SUB15 to an impressive 28mm while remaining only slightly deeper. This driver can handle up to 2500W before reaching X-max in a 50L enclosure. However, it comes with trade-offs: the driver is more expensive and harder to source.
This upgrade increases the maximum SPL by up to 6 dB per driver compared to the SUB15 across the entire frequency range. This extra headroom provides flexibility: you can either push for greater output or apply heavier pre-EQ to extend low-frequency performance. With the added headroom, the risk of overloading the driver is greatly reduced. While the SUB15 requires more caution, the SUB15X is far less susceptible to damage.
To accommodate the deeper driver, the driver is front-mounted, and the back panel includes a cutout with a metal cover to improve cooling for the voice coil. These changes slightly increase the overall depth of the subwoofer but still fit within our recommended 30cm-deep enclosures.
Keeping with the theme of modularity, only the front and back panels are affected by these changes. All other panels remain the same between both the SUB15 and SUB15X.
SHC SUB15 DIY Home Cinema Subwoofer Guide
SUB15X 50L
Dimensions (WxDxH): 60cm x 26cm x 52cm / 23.6in x 10.2in x 20.4in
The SUB15X-50L is called that because it has an internal volume of 50L litres. With a near field F3 at ~38Hz and an F10 of ~22Hz. However that F3 is lowered to ~26Hz in a 5m room once pre-EQ is applied with response only being down ~-4dB around 10Hz – so usable output goes down to 10Hz. Also, because of the large power handling, it can be calibrated flat to around 20Hz with more heavy pre-EQ.
Recommended power: 1X 1000 RMS (see recommend amp in Chapter 6)
Max power: 2500W before X-max is hit @12hz.
The major changes from the base SUB 15 model include the driver now being mounted on the front face of the enclosure, which expands the overall depth to 26cm (but not the depth of the enclosure). Additionally, a hole is cut out in the back panel, covered by a metal plate to seal the box. This modification allows enough air behind the voice coil to keep it cool.
Like the SUB15, this setup is ideal for small rooms with limited space and can be paired with the half-height 30L LCR10, but offers around +6dB more headroom than the SUB15.
This box design forms the base of the SHC SUB15X system, with all other configurations offering higher output. For more details, see the room sizing section.
SUB15X 102L Dual
Dimensions (WxDxH): 60cm x 26cm x 104cm / 23.6in x 10.2in x 41in)
The 102L configuration is built from two identical 50L boxes stacked on top of each other, with the top cover removed and the two inner braces aligned. Once sealed together, this effectively doubles the internal volume.
This setup effectively doubles the X-max of the single driver subwoofer, resulting in a potential increase of +3dB to the maximum SPL if using the same power source recommended for the 50L. However, if you double the power, you gain an additional +3dB, totaling a +6dB output increase over the 50L version while maintaining a similar response curve as the 50L setup.
This configuration is ideal for larger rooms or for individuals seeking increased output, as the addition of the second driver effectively doubles the air volume moved. However, it’s important to note that since both drivers share the same internal air space, they cannot be independently controlled. If individual control over each driver is desired, the next configuration will provide that capability.
Note the absence of a single-driver 102L version. Due to the characteristics of this driver, the benefits of a larger enclosure are negated by the need for driver protection at the larger volume. Therefore, if you want to build a 1m tall baffle wall, we suggest either making one 50L SUB15X with an empty box on top or one of the dual driver configurations.
SUB15X Dual 50L:
Dimensions (WxDxH): 60cm x 26cm x 104cm / 23.6in x 10.2in x 41in)
This configuration involves two identical 50L configurations stacked on top of each other. Therefore it has the same F3 as the 50L configuration but with the benefit of being able to increase output by +6db.
Recommended power: 2X 1000 RMS
Max power: 2500W per driver before X-max is hit.
This configuration is ideal for larger rooms or for individuals seeking increased output, as the addition of the second driver effectively doubles the power and air volume. This configuration can also be used with active room treatment technologies as it gives you the ability to control each driver independently. We advise this configuration over the SUB15X 102L Dual, as it provides less versatility.
Room Sizing:
ACHIEVING REFERENCE LEVEL
Please note that reference level playback is very loud for most environments. The program level for the LFE channel required for reference playback is 85dB, while dynamic peaks (e.g., explosions) need to be played back at up to 115dB. However, if the main speakers are bass managed and there is a bass contour applied, the required SPL could increase to 122dB.
With this in mind, if you are trying to reach reference level, it is recommended that you support the baffle subs with additional subs placed inside the room. We also recommend this to help even out the bass around the listening area.
The tables below lists both the program SPL and the Max SPL each different sub configuration for both the SUB15 and SUB15X can reach, as well as when 2 sub stacks are placed in the baffle wall.
NORMAL LISTENING LEVELS
People tend to listen to soundtracks at home at least 5-10dB below reference. 4-5dB below reference is also close to Dolby’s recommendation when listening to movie soundtracks mixed to standard in a smaller home cinema as it is equally LOUD to Reference played in a large auditorium. Keep this in Mind when deciding how much bass SPL you need.
ROOM GAIN
Room gain is especially beneficial for sealed subwoofers like the SUB15 and SUB15X. Unlike ported subwoofers which have a sharper drop-off in low frequencies, sealed subwoofers typically roll off at a slower rate, around 12 decibels per octave in the case of the SUB15 line. This characteristic allows the room’s natural boost at low frequencies to have a more significant impact. Even though the SUB15X line specifications might list a low-end extension (F3) in mid 30s Hz, the room gain will extend the bass response much lower in reality.
The tables on the next page provides an estimate of how much lower the in-room bass extension might be for the SUB15 and SUB15X based on room size.
F3 estimates are made using our suggested EQ settings and no low end boost, see SHC SUB15 DIY Home Cinema Subwoofer Guide for more details
It’s important to remember these are just estimates. The actual amount of room gain can vary depending on several factors such as room construction, room shape, subwoofer placement and listening position. Experimenting with subwoofer placement in your specific space is crucial to finding the sweet spot that maximizes the positive effects of room gain and minimizes any unevenness in the bass response.
Estimated In-room Response:
SUB15X Build Guide Now Available
Thank you for your continued support of our DIY Home Cinema Subwoofer lineup. We’re excited to announce that the SUB15X Build Guide is now available!
If you’ve previously purchased the SHC SUB15 DIY Home Cinema Subwoofer Guide, you’ll automatically receive access to the updated SUB15X plans at no additional cost—just check your email for the download link.
The SUB15X brings more power, flexibility, and low-frequency performance to your home cinema. Whether you’re upgrading your current setup or starting fresh, this guide will help you create a subwoofer that delivers reference-level bass with ease.
We’d love to see how your SUB15X projects turn out! Feel free to share your builds and experiences with us, and don’t hesitate to reach out with any questions along the way.
SHC SUB15 DIY Home Cinema Subwoofer Guide
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Hi Tyler, I was about to purchase everything for the LCR10 build and was then planning on moving into the SUB15s. This update provides a “significantly” improved performance, but having looked online for the newly specified driver, it is not available at all. I know you say that it is harder to source…but this stops this build from being simple. Does this mean the old design is flawed somehow or sub optimal and I shouldn’t build the SUB15s? The LCR10s are also being updated according to another of your articles – should I stop building the LCR10s as well? Feeling slightly disheartened!
Hi Nigel,
Thanks for reaching out and for your interest in building the LCR10s and SUB15s! I completely understand your concerns, and I’ll do my best to clarify and put your mind at ease.
First, let’s talk about the SUB15 and the SUB15X with the SQL 15 Series 2 driver. It’s likely out of stock right now due to a recent holiday promotion from Stereo Integrity, which probably sold out their inventory. However, the SQL 15 driver tends to restock fairly regularly, as it’s one of their most popular offerings.
The original SUB15 design isn’t flawed or suboptimal in any way. The SUB15X update simply offers a performance boost for those looking to push things further. Both designs are excellent. I actually use both in my own theater!
To help with your decision, the guide includes plans for both the SUB15 and SUB15X, so you can decide based on driver availability. One option could be to start building the SUB15 box now, and if the SQL 15 driver becomes available during your build, you can easily switch to the SUB15X design. This is possible because the only physical differences between the two designs are the front panels and a cutout in the back panel. By holding off on attaching the front panel until the end, you keep your options open.
Now, regarding the LCR10s: While there’s a roadmap for future updates, we haven’t started implementing any changes yet. The current design is reliable, high-performing, and fully capable. The core 0.5m box design is staying the same throughout all the talked about updates, so moving forward with the LCR10 build is a safe and solid choice.
We’re exploring some potential updates, such as modifying the 30L extension to support an optional second 10″ driver for increased sensitivity, creating a custom crossover for better frequency response, and experimenting with different compression drivers. However, these updates are still in the early discussion phase and won’t be implemented for some time. The good news is that they should be relatively easy to incorporate into existing builds if you choose to upgrade later, so you won’t need to rebuild the entire design.
If you’ve already started building the LCR10s, you’re absolutely good to continue. We’re committed to ensuring the current design remains relevant and compatible with any future updates.
I hope this helps ease your concerns! If you have any additional questions or need further guidance, feel free to reach out—I’m always happy to assist.
Best regards,
Tyler
Hi there
Would this be suitable sub(s) if ipaired this with KEF in walls kef ci4100ql ? cheers!
Yes, the Sub15X will pair very well with the KEF Ci4100QLs. They’ll add the low-end impact the in-walls can’t reach, and for larger rooms we’d suggest going with two or more for the best results.