okay - that's much more clear now. looks like the best bet is the KAB unit - i'm astounded, as was the original poster, that these are not more prevalent in a nicer "audiophile" package. |
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 |
That's what I meant. The sub-sonics are still there. Your sub will be trying to reproduce whatever signal is sent to it. |
What's still there??? The thread? If that's what you're referring to, yes, I know - hence me referencing it in my question.
It's not clear to me if what I'm stating is true - that if everything below 80hz is being sent to my one sub via the "sub-out" interconnect on my Outlaw RR2150 amp that I will essentially be negating any issues with subsonics and rumble. |
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I've got a question concerning this that was actually referenced in the other earlier thread (yeah, I know I'm resurrecting an ancient thread here!)
If I'm sending everything below 60 or 80hz to ONE sub (essentially mono'ing below 60 or 80hz... probably 80) should I have no problems with "woofer pumping" and subsonics? |
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 |
I swear, you guys, I did not mean to ressurect the same discussion. On the other hand, it is good discussion. I was watching my tonearm track a record last night. Record is tightly clamped down, cartridge is moving side to side and up and down as it tracks. What is really annoying is that I have a new mfsl with the spindle hole slightly off center. It's no wonder crap gets sent down the line. Anyway, I'm pretty new to analog and I'm paying attention. I don't think there is any one set in stone solution and I'm second-guessing my solution. I've had one person, with apparently lots of expertise, tell me to reduce the values of the caps in my tube amp. I'm not doing that but it probably is a legitimate thought and it probably is another solution. I am stepping back and considering everything all over again starting with the tonearm. Thanks for the responses, and Accoustat, for the poke in the ribs. Like I don't know how to spend money....this is the money pit! |
Most of us have power amps that won't be bothered by the need to pump the woofer cones in and out, and we sure won't hear 8 Hz or whatever it is. It's the audible frequencies produced by the woofers when they are pumping that should be of concern. The pumping will mean that the driver is sometimes functioning towards the ends of its excursion where its performance is compromised. For instance, a 200 Hz signal reproduced while the cone is pushed out by 12 mm will sound different from a 200 Hz signal reproduced when the cone is near zero excursion. The change of the 200 Hz signal will vary at 8 Hz (or whatever the pump frequency is). Not good. Also, there is Dopler effect to consider. The 200 Hz tone will increase in frequency as the cone is moving out, and decrease as it pulls in. Also, not good.
Bottom line is get a rumble filter (or stick to CDs). |
Dan, let me tell you a story. I bought a pair of non-powered Hsu subwoofers a while back and was faced with a choice of crossovers -- their passive one for $50 or an active one that included a subsonic filter, at $349. The Hsu advertising material said that if you played LPs, the active crossover was essential but I figured, what do they know, so I popped for the cheaper one.
Well. I was flat astonished to hear what was down there below 15-18 hz. Not music, God knows, and nothing anyone would want to hear. And only on LPs. Buying the active crossover eliminated the problem and, I swear, really cleaned up the low end response to boot. A friend without subwoofers but with very strong main speakers suffered from woofer-pumping -- with LPs -- and a subsonic filter fixed his problems too. I'm glad you haven't experienced this sort of thing; count your blessings. Dave |
Dave, I posted in haste. I didn't mean to imply that your amps were crap. I probably should have said "if one's amps are worth a crap".
Anyway. Yes, I can hear LF signals and that's my point. I don't use subs in my 2 channel system but both speakers I use (Aerial 10t, 16Hz and LaCampanella, 20Hz) are quite capable of getting down low with a great deal of authority. But the kind of LF signals that cause the woofer dance are the result of system problems or warped records. |
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? |
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. |
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. |
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 |
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. |
Put a cover over your woofers and stop worrying. |
Eldartford....there was one basic misunderstanding in that first thread. It was that I am dealing with a subwoofer. I am not. This is a pair of stereo speakers. That is why I did not find summing to mono at 180Hz a solution. As far as the inductors are concerned, I believe I see the same inductors in the Marchand active crossovers. Are you saying my solution is flawed because it is not powered? If I sent my phono amp to someone to be modified....18Hz subsonic filter added.....would that be better? |
The ferrite inductors used in the line level passive crossover will cause more sonic degradation than any interconnect. This is particularly true for the low frequency you are talking about, and the large amount of signal at that frequency. And, how will you hook up the XM-46SB without using interconnects?
Marchand makes good crossovers, reasonably priced. You would be better off with one of their active models. Actually, you would be best served by one of the purpose-designed rumble filters that were suggested in the other thread.
Lots of luck! |
