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Subsonic filter wish and a solution

I started a thread a while back called anyone wish they had a subsonic filter. Thanks to everyone for their input to that question, btw. I have a very mild case of woofer pumping as it is sometimes called. I can't hear it, as far as I can tell, but it bugs me because, as some of you have commented, it results in the amplifier using energy in it's effort to produce the very low frequency junk signals. I figured out quickly that I could not simply add a high pass section to the actual speaker crossover because of the huge size of the caps and inductors needed to do this. And since I like the match of my phono pre/cartridge/arm, I have been looking at either an internal modification of the phono preamp or a high quality outboard filter. It looks to me that Marchand's XM-46SB is my solution. It can be customized as to frequency rolloff. I ordered one that rolls off at 24dB starting at 18Hz. It does what I want it to do, and no more. I'm hoping that the benefits will outweigh the downside of adding two interconnects and the circuit to my system. My main objective is to solve the problem with little or no affect on the frequencies above the 18Hz, and also to avoid buying a new phono preamp. I'll post again once I get the filter, in case anyone is interested in the results.
240zracer

Showing 3 responses by acoustat6

acoustat6
357 posts
 
Hi 240z, That will work just fine and as you said it will do the minimum that you want which is get rid of the subsonics. It of course does not address the rumble. What I would do is spend a little of your money! I think your ultimate solution is a Marchand Bassis and a 3 way crossover of your choice and since you seem to know which end of the soldering iron is hot go with the either a kit or EZ kit. You will be very pleased with the flexability that you have when building and fine tuning your speakers. Also as I had mentioned before in your first post the Marchand Bassis is a great piece of equipment as is also very useful for any speaker system but especially for a home speaker builder. With the addition of this unit you get the Bassis EQ abilities ( please look and study its function carefully ) and the 20hz and rumble reduction, via summing, at your speakers Fs point which are the two solutions you are really after. This summing point would be substationally lower than the 180hz rumble filter as previously suggested which is way too high, so you dont need "lots o' luck". Also you do not want your speakers pumping so covering them is not a solution. Again if I were spending your money I would go with the Bassis first then look at the active crossover of your choice. I generally don't like when products are reccomended as I prefer ideas and leave the product selection up to the individual but I guess its necessary sometimes.
Bob
PS I would upgrade to the stepped attenuators in both the Bassis and the crossover.
acoustat6
357 posts
 
Hi 240Z, Sorry, I know you were not looking for advice in this thread, so perhaps I should have kept my mouth shut. Around here everyone, my self included, wants to spend everyone elses money, its too easy to do.
Bob
acoustat6
357 posts
 
Hello,mono-ing at at a selected freq reduces/eliminates rumble, which is different from subsonics (below 20hz). You really need both but it is system dependent. My answer is you need a 20hz filter and a rumble filter at a selected freq. With the rumble filter it is to be selected, by you, according to your systems needs. You may want as high as 60hz or 80hz but it is better to stay around 40hz with stereo subs. Since you have a mono sub your "rumble filter" has been selected for you by your crossover freq. So yes you still need a 20hz filter.
Bob
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