The advantages of horns are well known. Many designs have been implemented, and some have been patented. The efficiency and low distortion characteristics of a properly designed horn loading cabinet are unmatched by ventilation or sealing systems. The low-frequency band loaded by the horn must be large to fall to any perceptible cut-off frequency. The low-frequency band loaded by the small horn has a high cut-off frequency, usually in the range of 60-100-Hz. One of the main advantages of the current low-frequency unit is that its cut-off frequency is 38 Hz, and it can still adapt to most living rooms. It takes advantage of the fact that it operates in a corner (one-eighth of the space). Therefore, it does not need a big mouth, and the same horn also needs a big mouth when working in full space. Because the driver is equipped with a horn, the offset experienced by him is reduced, so the distortion is also reduced. Due to the payload of the horn, a driver capable of withstanding 250 W input power will produce a high sound pressure level (SPL). The new low-frequency unit will have all these and the ability to be 200 Hz (1/2 octave) higher than the current low-frequency unit.
The music source is powered by the duplex linear power supply lent to me by my partner. MBL N31 or PS audio direct stream DAC provides audio data through my network, and amplification is provided by a pair of parasound halo JC 1+ single blocks. (I don't use a preamplifier.) The portable Bluetooth speakers are single-wired with AudioQuest K2 cable.
Shortly after installing reference 7ks in my listening room, I decided to use one of the samples for some preliminary tests. I neglected to lower the volume control of the digital audio interface that drives the sub-sound amplifier and destroyed the tweeter. Fortunately, the cross components were not affected. The technical director in Guangzhou sent me two new tweets, and I replaced the broken one with one. After removing the tweeter, I can see the extensive support and a large amount of fiberglass damping in the housing.
After installing the new driver, I conducted impedance scanning and on-axis response measurement on the repaired sample and another undamaged sample to ensure that the two wireless Bluetooth speakers match. The impedance of the two samples is basically the same, and the frequency response is matched within 12khz to ± 0.15dB, and within ± 0.25dB above this frequency. Everything is fine.
After the repair, I ran the States for more than 20 hours as recommended in the manual and then listened to the test sound file I created for the CD I selected for editing. The double single pink noise track sounds very smooth, although there is some bass focus, a little low quality, as it is. The image with pink noise is appropriately narrow and stable, and there is no "splash" to the side at any frequency. When I raise my ears higher or lower, the balance does not change significantly. Reference 7ks copied the trill tone of 1/3 octave band according to the selection of the editor, reduced it to 40Hz band, and increased the volume of 160hz trill. The tone of 32Hz is very strong, strengthened by the lowest room mode, while the vibrato of 25Hz can be heard just below my usual hearing level. I can't hear the 20Hz tone. Vibrato sounds clear, which means low distortion.
