Speaker System No.2800 -- Initial Testing

Speaker system No.2800 is a recent development stemming from the desire for a more compact solution that doesn't compromise on sensitivity or low distortion bass. The idea of a more compact form factor came from my discontentment on the visually imposing presence of the 2095 speaker, which I didn't feel was a completely homogenized design language between the horn and bass cabinet. It felt like two different design philosophies in terms of appearance. 

How Insensitive 

I've tabled a typical woofer's sensitivity along with what happens when we double up the woofer in either parallel or series wiring configuration. 

We see that the parallel wiring wins at 98.5dB sensitivity (green) however it pulls 2.54W (red) from the amplifier to achieve this. Not really ideal for a low power tube amp.

If we change the table and fix the output power to 1W then both the series and parallel win the day. But is there one better than the other for your tube amp?

If we add in the load variable we can see the series wiring will require less demand on the tube amp in terms of windings on the output transformer...hence lower distortion. In other words, it now affords us to use the 16ohm taps if available.

This is a key insight into Speaker No.2800 which uses dual ten inch woofers in series to hopefully achieve our goal of low distortion. But what should be the benchmark for low distortion? 

Let's look at some other great woofers that we can benchmark against. 

Below is the distortion performance of the Beyma 15LX60V2 at 95dB SPL for 1m. Generally we see just shy of 1% for the bass region.

Below is the Purifi PTT8.0X04-NAB-02 at around 0.50%.

Below is the JBL 2226J 15" woofer, again almost cresting the 1% barrier. 

So very generally it would be reasonable to set our target at less than 1%. 

Actual Measurements 

Speaker System No.2800 uses dual SEAS CA26RFX (H1305) wired in series in a 111l Bass Reflect enclosure tuned to 38Hz. We can see that distortion for the 50Hz region is 0.63% for H2 and 0.23% for H3. Wonderful!

There also appears to be the same ladder affect that I see consistently with great sounding equipment, even electronics. 

The other aspect to consider is that we are getting much more deep bass output compared to the 15" woofers shown earlier. 

 Subjective Listening 

For the subjective test I decided it would be great to test my new multicell horn design No.2567. 

Playing Daft Punk's Tron soundtrack produced bass extension to 20Hz. The bass was well defined in terms of pitch definition. I am very happy with the overall bass quality and it seems to check off all the boxes... small size format, deep bass, low distortion, and high efficiency. I will continue to publish test data and listening impressions as I develop speaker system No.2800 further.