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I’ve been on the lookout for a midwoofer with outstanding midrange. The best I have is the Audax HM130C0 but it’s a pretty expensive driver. The next best is my Peerless 830870. These two drivers have ruler flat frequency responses coupled with excellent bandwidth. The RS125P-8 is a 5″ midwoofer from Dayton’s Reference Series. I’ve never heard this midwoofer before so I’m testing it out with an open mind. Since my main aim is midrange, I mounted the RS125P onto a 6 liters sealed box. In this configuration, it will be the midrange in a conventional 3-way.
Fig 1 above is the Raw frequency response of the RS125P-8. No smoothing is applied. Mic is at 36 ins, on axis. The RS125P-8 is not as flat as the Audax HM130C0 and the Peerless 830870. There is a bit of a bump at about 1,300Hz which will add some presence. At the top end, there’s a peak at 8kHz after which it rolls off. A good crossover frequency would be 2.5kHz. Maximum would be 4kHz. I dislike crossing so high but sometimes you just have to because a tweeter like HiVi RT1C-A cannot be crossed lower than 4kHz.
The bump at 1,300Hz is clearly visible in the Waterfall plot (Fig 2). The 8kHz peak is even hotter. It would be wise to use a tweeter so that this peak is removed.
Fig 3 is the Toneburst Energy Storage plot. We can see the excess energy at 1,300Hz and the bunch at 8kHz. They correspond with the hotness in the waterfall plot.
The Spectrogram (Fig 4) shows a hot spot at 1,300Hz with a second one at 8kHz. I doubt you can hear them because they don’t last more than 3 msec. All three plots show hotness at 1,300Hz and 8kHz, just presented differently. Tonal QualitySurprisingly, the RS125P-8 sounds fine as a full range. I couldn’t pick up the bump at 1,300Hz. As for the hotness at 8kHz, it resulted in some brittleness in the treble but that’s expected. What is most important is there’s no muddying of the vocals. Bass is kept well away from the midrange. This can be seen in the frequency response in Fig 1. Bass is about -10dB down. That’s with the natural acoustic roll-off from a sealed box. In a 3-way, I would cross it at 250Hz to the bass driver. That will improve the power handling of the RS125P-8. At the treble end, 2.5kHz would be the highest I would cross to the tweeter. That is a very comfortable frequency for most 1″ dome tweeters. The issue I have with this RS125P-8 is the price. At $42, I expected a flatter frequency response. The Peerless 830870 is a much better buy at only $32. To be fair, I need to test out this RS125P-8 in a bass reflex. Maybe that’s where I can justify it’s higher price. As it stands now, there are other drivers that are better and cheaper in a sealed box. Now that I know what the RS125P-8 sounds like, I would really like to hear it in a MTM. If I can get the vocals to project, then the price is worth it. Lastly, I should mention that the RS125P-8 is more of a 4″ midwoofer rather than 5″ that is presented in their literature. The frame is 5″ but the woofer radiating surface is closer to a 4″. In fact, the piston diameter measured from the center of the surround is only 3.25″. Blending in the BassHaving ascertain the tonality of the RS125P-8, it’s time to hear how it sounds with the bass added in. After thinking it over, I decided on the Toucan-SF. This 8″ Silver Flute Bandpass is one of the most detailed subs I have. I used an external crossover set at 250Hz (24dB/oct) to cross the Toucan-SF to the RS125P-8. As I had hoped, the bass not only blended well but the clarity in the vocals is not compromised. Now, the bandwidth extends down to about 50Hz (-3dB). The RS125P-8 sounds more palatable now. Once I add in the tweeter, the system would be complete. Unless otherwise stated, all measurements were made in Full Space (4 pi) with the mic at 36 ins, tweeter axis. Impulse Window=5ms. No smoothing applied. |
May 16, 2022Drivers Evaluation, HIFI DRIVERS
Fig 1 – Dayton RS125P-8 Frequency Response • Baffle Width=8-1/2″
Fig 2 – Dayton RS125P-8 Waterfall
Fig 3 – Dayton RS125P-8 Toneburst Energy Storage
Fig 4 – Dayton RS125P-8 Spectrogram