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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
eldartford
4,262 posts
 
Marchand active crossovers (all the ones I have used) use no inductors.

Summing to mono at low frequency is perfectly appropriate for stereo speakers. In fact, in producing LPs, it is commonplace to do this. You should not be so upset by the 180 Hz number. The reduction of separation is a gradual thing, not an abrupt change at 180 Hz. At 20 Hz there is no musical signal separation on the LP to be lost. Just rumble, which you want to loose.

But you seem to have your mind made up. As I said, lots of luck.
dopogue
1,767 posts
 
Yeah, put a cover over the woofers. What you don't see can't hurt, huh? Personally, I wouldn't be without a subsonic filter. Let us know how the Marchand works out. Dave
dan_ed
2,451 posts
 
Dave, you're the first person I've heard say they wouldn't be without a subsonic filter. If your amps are worth a crap you will not have any problems. Why apply that filter to records that don't exhibit LF issues? If it's happening with all of your records then the problem is with the table or what/where it is sited. What ever floats your boat.
dopogue
1,767 posts
 
My amps are worth a crap, including the subwoofer amp which fortunately has a subsonic filter built in. EVERY LP exhibits LF issues -- if your amps and speakers go deep enough. There's a lot of LF garbage down there You never heard it?
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.
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