15L Bass Reflex

It was 3 years ago that I first worked on the Peerless 830874. At $50 a piece, the performance is way above the competition. So much so that I would recommend the 830874 if my budget can’t accommodate the Seas ER18RNX.

In this Cardinal, I’m mating the woofer with a Seas 27TBFC tweeter. This tweeter is the Aluminum/Magnesium diaphragm of the sister 27TDFC. She cost more than the Peerless XT25TG30-04 that I used in the Cardinal-XT2 but the price is justifiable. The 27TBFC is in a class of her own. For the quality conscious, the Cardinal-TBFC is the one you want.

Fig 1 – Peerless 830874 RAW Response • Baffle Width=8.75″

The RAW response of the 830874 is in Fig 1. This is with the woofer mounted in a 15 liters bass reflex with an over-damped alignment. Measurements below 500Hz include my room reflections. Disregard the deep suck-out at 150Hz. That comes from a floor bounce.

In the Cardinal-TBFC, my aim is to get as much bass as possible and I want to do this without destroying the midrange. That’s very important because the midrange is what the 830874 is all about. Lose that and you might as well use a cheaper woofer.

We can see the bass is at 80dB whereas the midrange is about 7dB more. If this is not attended to, the speaker will end up with too much midrange. This makes listening very tiring. 

Fig 2 – Peerless 830874 with Low Pass Filter (LPF)

The Blue plot in Fig 2 is the 830874 corrected for bass. Now the midrange is only 2dB at 800Hz. I cannot lower it more because I will lose the midrange and it will also affect the crossover to the tweeter. 

Fig 3 – Seas 27TBFC RAW and with High Pass Filter (HPF)

The Black plot in Fig 3 is the RAW response of the Seas 27TBFC. As with most dome tweeters, the TBFC must be flush mounted otherwise the diffraction will cause havoc in the response. The Red plot is with my High Pass network.

Fig 4 – Peerless 830874 Low Pass with 27TBFC High Pass

Fig 4 shows the response of the two drivers. They are crossing at about 1.8kHz. The 27TBFC has a beautiful roll-off whereas the 830874 has a slight bump at 4kHz. That is from the cone breakup. I did not notch it out as I don’t think it’ll affect the sound much.

Fig 5 – Cardinal-TBFC Passband

The Black plot in Fig 5 is the summation of the 830874 and the 27TBFC. There are no cancellations in the crossover passband which is a good sign. Note the slight cancellation at 4.5kHz. That’s the effect of the cone breakup I mentioned earlier. 

Fig 6 – Cardinal-TBFC Frequency Response

Fig 6 is the final frequency response of the Cardinal-TBFC. It is exceptionally flat except for a slight blemish at 4.5kHz. That’s the penalty I pay for not taking care of the cone breakup. During auditioning, it is not noticeable. However, if I want it gone, it’s not that difficult. It’s just a question of whether it’s worth the extra cost.

Fig 7 – Cardinal-TBFC Null

The Violet plot in Fig 7 is the Null Response. A deep notch centered close to 2kHz resulted when I flipped the tweeter wires around. This indicates the two drivers exhibit good phase alignment.

Fig 8 – Cardinal-TBFC Frequency Response with Nearfield Overlay

The Blue plot below 500Hz (Fig 8) is the nearfield response of the 830874. In this measurement, room reflections do not have the chance to be picked up by the microphone because the mic is about 1/4″ away from the cone surface. What I’m recording is the response of the pressure waves. You can see the deep notch at 150Hz is not from the woofer. It also does not take into account the output of the bass reflex port. It is obvious now why I cannot use a nearfield response when I’m tuning a speaker for bass. 

Fig 9 – Cardinal-TBFC with Nearfiled below 500Hz

For a pretty response, Fig 9 is what the Cardinal-TBFC looks like. If I want to make it even prettier, I smooth the response by 1/6th octave. Then you’ll see the treble even out. Right now, no smoothing is applied. I need to work without smoothing so that I can see exactly what is happening.

Fig 10 – Cardinal-TBFC Step Response

The Cardinal-TBFC Step Response (Fig 10) shows a smooth transient from take-off. The woofer is actually quite fast. At 90%, the woofer is at 300 microsec. In the next 10%, it slows down slightly, hitting the apex at 400 microsec.

Fig 11 – Cardinal-TBFC Waterfall

The Waterfall plot shows the Cardinal-TBFC have minimal artifacts. The 27TBFC is almost faultless above 6kHz.

Fig 12 – Cardinal-TBFC Toneburst Energy Storage

The Toneburst plot did not record any stored energy from 1kHz to 2kHz. There are some light blue slices at 5kHz but they soon die out by 5 cycles.

Fig 13 – Cardinal-TBFC Speactrogram

The Spectrogram shows a light streak at about 1.1kHz. It dissipated by 7 msec. Apart from that, the rest of the plot shows no major hot spots.

Sound of Cardinal-TBFC

The Cardinal-TBFC is all about vocals. That’s where she shines. But that doesn’t mean she’s bass shy. On the contrary, the bass is quite distinct and more importantly, it doesn’t over-power the midrange. Add in an exceptionally sweet tweeter, the Cardinal-TBFC is hard not to love.

Soul Provider (Michael Bolton) is one of those recordings that’s difficult  to reproduce properly. The bass is strong and forward. Often times, it just muffles his voice. When that happens, we turn up the volume because we can’t hear the voice clearly. We don’t need to do that with the Cardinal-TBFC. His voice cuts right through the mix. Clear as hell.

Moving on to a recording where the singer is well isolated, I played Always On My Mind by Michael Bublé. The musical accompaniment is just right, never over-riding the singer. The tonal balance is perfect, the bass is there, he can be clearly heard without sounding shouty and the treble is invisible. No harshness.

The Cardinal-TBFC has what I call a “refined” sound. Similar to the Seas ER18RNX. It’s hard to describe. Somehow, it’s very soothing when listening to this kind of speakers.

A word of caution about the Peerless 830874. The woofer doesn’t sound nice when you first hear it. The bass is hard. Run it for a few days. Once she’s broken in, you’ll find the bass sounds much better. 

Crossover is available on request. Free for DIY. Not for Commercial use.
Unless otherwise stated, all measurements were made with the mic at 36 ins, tweeter axis. Impulse Window=5ms. No smoothing applied.