In this blog post I look at a design study which directly compares simulation results between my 15" BLH No.2095 cabinet against a proposed 18" version. I look at the simulation results along with some computer renders to see how this would visually look.
Rationale
By increasing the cabinet size from 15" to 18" there is a potential to increase overall sensitivity along with bass extension. The increased size also allows use of the ES290 Biradial which is 67cm wide. The existing 15" BLH No.2095 uses the ES450 biradial which is 52cm wide. This allows for a lower crossover point as well, improving coherency through the vocal range. Also, by increasing the radiating area then distortion would be correspondingly reduced as well. Cone velocity would be reduced (for the same SPL) and so dynamics should see a improvement as well.
Hornresp
I use Hornresp to simulate the 15" version (No.2095) which was built last year. Hornresp does not take into account the continuation of the horn path into the room which adds about 25% to the horn path length. This extends the bass from 50Hz to 40Hz.
Below is the hornresp simulation for bass cabinet No.2095 using the Beyma 15LX60V2.
This results in the following simulated response.
Basically this corresponds to my own actual measured frequency response in terms of bass extension and sensitivity. I was able to get bass extension to 40Hz with a sensitivity of 105dB (in-room) at 80Hz.
Don't Be Alarmed!
The Hornresp simulation does not represent the actual response, but gives us an indication of what we can expect in terms of bandwidth and sensitivity. To highlight this, I've shown my as-measured frequency response of the 15" BLH cabinet No.2095 using the Beyma 15LX60V2.
The focus of this blog is to look at what a scaled up version would look like using the 18" version of the Beyma woofer (Model 18LX60V2).
I first had to make the design changes in Solidworks to see what the new hornresp parameters become. I've created a table below to highlight the changes when increasing from 15" to 18".
| Description | Throat Area | Mouth Area | Horn Path Length | Add 25% | Sensitivity at 80Hz (in-room) | Bass Extension F3 |
| BLH Horn No.2095 15" | 343 | 2584 | 247 | 308.75 | 105 | 40 |
| BLH Horn No.2564 18" | 378 | 2445 | 288 | 360 | ??? | ??? |
The physical cabinet width needs to increase from 520mm to 574mm which is an increase of 54mm (2.1"). The depth of the cabinet increases from 630 to 680 which is an increase of 50mm (2").
Below is a render of the 15" bass cabinet No.2095.
Below is a render of the 18" bass cabinet No.2564.
Taking our new 18" cabinet dimensions and simulating this in Hornresp yields the following result.
At 80Hz the we don't see any increase in sensitivity. Bass extension improves from 40Hz to 35Hz.
Conclusion
Increasing the cabinet size to 18" increases bass extension to 35Hz. The sensitivity is unaltered but we should see a corresponding improvement in distortion and dynamics with the larger driver. The larger woofer is better suited to the ES-290 Biradial which offers a larger sense of scale to the perceived soundstage. The lower crossover point will provide a little more coherency by having the biradial cover more of the vocal frequency range.