At other positions, U2 (1) becomes an underdamped high pass filter.
In the FLAT position, U2 (1) becomes a second order (12 dB/oct.) high pass filter. S2, the LF EQ switch, controls the cutoff frequency. This is how the high pass filter and boost work according to the service manual: The one op-amp is for the 18 dB/octave low pass section and the other is for the high pass section. The filter for the low pass section is made up of a single-chip dual op-amp. This is what I learned while looking over the schematic.
#Subsonic filter diy how to
The service manual has the schematic for the unit which is key into figuring out how to adjust the high pass circuitry. They had a link to both the manual and the service manual. I found it in an unlikely place – someone’s eBay auction that had ended months ago. The first thing I needed to find was the service manual for this unit. The EV XEQ-2 is the perfect crossover for achieving this.
#Subsonic filter diy driver
An ideal subsonic filter is achieved by setting the cutoff frequency to be low enough to have a negligible impact on the acoustic response of the driver/enclosure while still maintaining just the right amount of safety margin below tuning for the driver so that it does not exceed xmax. It is either too high, in which case it negatively impacts the natural frequency response of the driver/enclosure, or it’s too low and still allows the driver to exceed its rated excursion capability. However, the problem with most rumble/subsonic filters is the cutoff frequency is arbitrarily chosen and usually does not represent the ideal cutoff frequency for the subwoofer to which it is connected. Any vented subwoofer will essentially unload below tuning which can cause the driver to exceed its rated xmax (or even xmech) causing potential damage to the driver. And this is how I did it.įirst off, why put a high pass filter on a subwoofer at all? Commonly referred to as a rumble filter or subsonic filter, the idea is to remove frequencies below that which you can’t hear or those frequencies below where your sub can adequately produce, in an effort to reduce driver excursion and reduce stresses put on your amplifier. What I really wanted was to do was adjust the filter for a predetermined cutoff frequency that corresponded exactly to the maximum excursion capability of my new Audiopulse vented subwoofer. Definitely not optimized for HT and certainly not for a subwoofer that is, by design, flat to 20 Hz. Each click of the switch adds +6 dB boost at varying frequencies from 29Hz to 60Hz. Worse than that, the options for adjusting this filter don’t offer any solutions. The one thing I always disliked about this EQ was the 30-Hz built-in high pass filter. Using cartridges that use very low tracking pressures always seemed to me to be the most prolific in causing resonances using the wrong tone arm.I’ve got an old XEQ-2 active crossover made by EV that I’ve been using for the crossover on my subwoofer for my home theater. Rek-okut and Thorens 124, 121 and 111 were real freight trains and why I bought my TD 125 when they first appeared.
Thats why the little AR turntable became so popular, no rumble and great pricing.
#Subsonic filter diy mac
Mac and AR speakers were famous for flopping when turntables were noisy. You might increase your tracking pressure to the highest recommended and see if the noise either decreases or increases, If there is any change you may have found the real issue. I would see if the arm and cartridge are compatible first. So you need to check that possibility also. It could also be the cartridge and tone arm don't match up their resonant frequencies causing unwanted low freq noise also. Now that you know the issue you are pre-pared to cruise the internet to make the correct choice for you. Fortunately my pre-amp for the phono has the built in filters. Some audio philes have scared manufacturers away from installing subsonic filters in their gear and the consumer has to suffer the consequences.
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