Subsonic Rumble Solutions

Acoustat6...What you describe is ideal. All we could quibble about is the frequencies.

So I think I'm hearing what I kind of feared - that, given very good isolation, the final solution to subsonics lies in the signal path via a filter of some kind. I fear this because I would prefer to keep things as clean as possible. I fear this because I just know I will hear something missing in the top end, or the soundstage, or something like that that bothers me more than a little subsonic rumble once in a while.

I guess the only way to know is to try it myself. Well, I'm a DIY kind of guy, and the filter can probably be built for about $50 and a little time. I've got a few questions out to Elliott Sound Products about their filter and how I can implement it. I will share those on this thread when they reply.

Thanks,
The First Bob (#1 I guess, since I started the thread :-)

I received a reply from Rod Elliott on my questions about his filter (see below):

My question about using a lead acid battery or a laptop power supply: "The circuit is specifically designed to operate from a split (+/-) supply. While a single 12V supply could be used, I don't recommend it."

Op-amp related questions: "All the signal runs though the opamp all the time - there's no other way to do it. You can use any dual opamp that you like - despite its age, the NE5532 is a good choice, as is the OPA2134."

Gain related question: "The circuit is unity gain."

Thanks Rod. I will have to reassess after the holidays are over. I may try a few other things in the meantime. Maybe an experiment with resonance damping in the headshell just to make sure it's not a mechanical issue I'm having.

Thanks for everyone's replies,
Bob

Hi Bob#1, Keep us informed. Many times, people report a increased clarity to the music, as a result of removing unwanted cone movement (equals noise, wasted power from you amp and loss of control of the driver). And your amp will be happier.

You appear to have only one sub, so you are in mono at your crossover point. That would be your "rumble filter".
You now need to try a 20hz filter for the subsonics.

Albert had kindly offered to speak to me over the phone regarding this issue, but I think we should keep it in this thread so everyone can benefit. Albert if you have any suggestions or comments please post them here.

Bob#1, you are probably limiting your system if this is a problem in your system. It needs to be eliminated for your system to shine (if it is disturbing/loud enough). How you do it is up to you. Whether you can find a mechanical solution, adding a filter or roll off of your speakers low freq extension. All of these have benefit in not hearing rumble or subsonics. If you can live with a little "rumble" that is an option that is up to you.
My guess is it is not rumble (since you have a mono sub, OR it may be rumble that is above your crossover point!) so it is probably subsonics ie: below 20hz. And filters work very well for this.

You never did mention when you have this problem, is it at certain volume levels, LPs with low bass, certain records that otherwise appear quiet?

Of course there is one other problem that is not system related which I mentiond above, which is rumble pressed into the record. Some of this rumble can even be above 100hz. This you just have to live with, knowing that it is in the lp and not your system. But even this can be eliminated, with a filter. The problem with this is that you want to keep it stereo down to as low as you can. I think this means stereo down to at least 50hz or better yet 40hz. And these freq will do a very good job of elimininating most rumble.

Bob#2
We are not men , we are Devo

Hey Buddy-Bob 2,

I can say with some certainty that the woofer pumping is there on most LP's to one extent of the other. But my ears feel like they are popping on some, but not all, LP's. If I turn the sub off on these I don't get that annoyance (my regular speakers probably drop down to about 30hZ). It is most noticeable on the lead-in groove and 1st song or two, and less at the end of the record, but still there.

You are correct about the amp - less low frequency need means a more efficient presentation overall, helping both speakers and amp.

I don't have time for a new project right now, but I will probably get itchy after New Years and look at this possibility again. It also means adding another interconnect into the mix, since there's no room to incorporate this into an existing box.

Bob #1