Official Rythmik Audio Subwoofer thread - Page 207

how many of you here have the driver aimed and fired to the MLP?

When I get mine, hopefully later in the week, my FV15 will be directly in front of my lp. I'll let you know how it works out!

Jeff

Mine are. Conventional wisdom says it doesn't matter, but I wonder about that. Seems like the most direct path so you're not accounting for delay due to bouncing off walls and what not.

I wanted to follow up on my post awhile ago where I was comparing the distance my receiver set my subs at vs. the distance Rythmik's Subtuner calculator gives.

My theory was that if one of these was out of phase slightly, you might hear the frequencies where the crossover exists to be lower. So I finally got some time alone in the house without the wife and was able to take some measurements.

Important info:

• Rythmik calculator sets the distance at 6' 9"
• Pioneer MCACC sets the distance at 9' 8.5"
• Crossover point is 80 Hz
• Used one of the new Radio Shack SPL meters - have no idea how good it is at bass frequencies, but figured for a relative comparison it didn't matter.
• Used warble tones for my frequencies, they tended to jump around a little bit on the meter. So the degree of accuracy included me watching a moving number and trying to figure out what the overall average is. So these numbers are probably not very exact. I'd say min +/- a couple dB's error margin.

You can see the graph in the attachment. Basically in terms of pure SPL there didn't seem to be much of a difference. Maybe ever so slightly in favor of the Rythmik calculator above the crossover point.

But I spent some more time listening to music between these two. I think there is more to the story here than SPL.

Electronic dance music is a great genre to test out this type of thing because the instruments are done in a computer and perfectly aligned. So if you hear a drum beat and a bass beat or bass line, you can actually tell if they are aligned well or not.

With Pioneer's MCACC setting (which is actually very close to the real distance the subs are from listening position), bass seemed muddier and actually like there was more bass. I think I can attribute this to a longer delay than there should be on bass notes. So for instance the drum beat hits, you hear the higher frequency part of it, then slightly later the subs kick in. So the actual drum beat lasts a bit longer than it should = "more" bass that sounds muddier. When there was a very busy bassy party of a song, the bass from the subs seemed decoupled from the music and was just rumbly.

With the Rythmik Subtuner setting, the bass sounded tighter, and more controlled. It gave the perception of less bass, but it was a lot cleaner. It's obviously not less bass in terms of SPL given my measurements, so I think it's just a perception probably due to the slightly shorter time span a drum beat exists from the snap to the bass note. In the same busy bass part of the track that sounded rumbly before, now you could tell the drum beat that the bass note was attached to.

Hopefully you guys find my experiment interesting. I did. I fully expected to see more discrepancy between these two in terms of SPL. But it looks like Brian's program does a great job at making the cleanest, tightest integration between mains and subs. Thanks for taking the time to create this Brian!

Finally got moved into my new house and got a chance to snap some shots of my new FV12. This thing rocks my 2600 square foot house. I put on the Dark Knight for my brother to get a quick demo. I played the tunnel scene and he couldn't stop smiling he said he forgot where he was momentarily I love this thing guys. The bass is deep, powerful and very clean.

A few more...

That's one of my favorite demo scenes! I smile all the way through it.

Also, the pictures do not do this baby justice. It looks much better in person! I have only had it a few days now and have only watched Dark Knight and Return of the King and some shows. I need to watch more flicks to really put it through its paces.

How big is the room you have it in?

What is MLP?

Main Listening Position. Took me a few minutes to figure it out too. And as far as his question goes I do not have the sub's speaker pointing at my MLP. It doesn't matter with low bass example down firing sub.

I will take some measurements tonight.

Has anyone just bitten the bullet and put in an isolation transformer? I can't imagine that it wouldn't completely cure the problem of buzzing due to DC offset.

However, it would be important to size the transformer properly. It probably isn't necessary to use a transformer that is average-rated for the peak power that the speaker can draw--usually the peak current issue for an isolation transformer is more a matter of heating and mild ohmic flat-topping of the waveform rather than saturation. Brian could probably chime in with some safe-area operation (how much current the speakers can draw for so many cycles before they limit). Of course, you can simply get a 750 VA continuous duty isolation transformer, and not worry about that minor point.

I will probably just end up getting the Emotiva CMX-2 to solve my buzzing issue. But it isn't cheap and I'm considering just living with the DC offset. My heat sinks don't seem to be getting hot, so perhaps this is more just an annoyance than issue.

Have you considered one of these?:
http://www.tripplite.com/en/products...xtSeriesID=825

I use Euro-4 mostly for it's mains switch but it also provides a bit of protection as well. Perhaps one of the IsobarXUltra products might be what you need. Not as expensive as Emotiva solution.

Is it designed to block dc offset?

Yeah, I can't tell by its description. At least the Emotiva one is very obvious that it will do what I want it to.

My living room is 14Wx16Dx14H and is completely open to the kitchen, dining room and upstairs loft.

I don't trust surge suppressors. I have had a sub amp, an AVR and various computer peripherals taken out by lightning strikes. All were plugged into good surge suppressors. Most surge suppressors will only take one hit, but will keep working and you think you are protected but you are not the second hit fries your equipment. The warranties are a joke they make you jump through so many hoops you'll never get them to pay up. I now only use battery backups with power conditioning. I have never had anything struck that was connected to a UPS. I'm not sure if they block dc offsets though.

Re the Isobars mentioned by Iain:

These look like high quality surge suppressors. They don't look big enough to contain simple iron transformers, so I'd be surprised if they have any effect on DC offset.

As an aside to someone who has the buzzing--and possibly Brian--has anyone ever placed a current clamp and 'scope over a buzzing transformer? The current waveform would be obviously spiked if the transformer was being driven into saturation.

My Panamax isn't even listed in their website! But, to be fair it is 18 years old give or take! I bought it for my C-Band Satellite system and I lived in the lightening capitol of the U.S. in Sarasota, FL. And I have had NO issues, even out here in AZ. When I get the new sub hopefully I won't get a "buzz" so to speak!

Jeff

Tripp Lite also make isolation transformers:
http://www.tripplite.com/en/products...xtSeriesID=839

Every product they make in this class is industrial quality. I would recommend at least 1 kVa model for Rythmik subs though.

How about this one for the humming buzzing subs...cheap.

Jensen

Specs

We're talking about humming on the AC line, not the RCAs. So the filter needs to be between the wall and the power supply.

I follow this thread carefully. In fact, I intend to buy a CI version of the FV15HP in a matter of a few weeks. When I hear all this talk about how to make these subs perform in a way that they should to begin with, I am concerned. One of these devices to reduce hum will set me back $400ish and that is after I just spent $800 + shipping + taxes on the sub kit. Soooo....questions

1.) Is this hum something that is inevitable?

2.) If not, how common is it?

3.) Can I somehow anticipate if my sub will suffer based on what I am running on electricity in my home?

4.) Are there any other brands of sub that suffers from this malady?

Thanks for your help.


Jono

Google - Ground Loop

or read this = http://www.epanorama.net/documents/g...oop/index.html

this may be helpful also - http://www.rane.com/note110.html

The discussion is about dc offset not ground loop hum. DC offset has to do with your home wiring or neighborhood power grid. Brian has said that it is less than 1 in a 100 (thats me ) that has had problems with this. Ground loops are fairly easy to find and fix. My dc offset is coming from an out side source so its not so easy...However the cmx2 has for the most part solved it.

1.) Is this hum something that is inevitable?

No, in fact it is rather rare. There are two types of hum mentioned in the last few posts. The common one is hum pickup by the various pieces of the electronics. It is often due to poor shielding or multiple ground connections between the various pieces of equipment.

The topic that this discussion started on is buzzing of the subwoofer's power-supply transformer due to DC offset on the line. That is a problem in the power not being all AC--having a small "offset" so it is not symmetrical. This current can push a transformer's operating point (in B-H, or induced flux vs. applied magetization space) up on the B-H curve so it saturates during a brief part of the power cycle. I've dealt with transformer saturation in electrical designs, but I've never had a DC offset problem that I'm aware of in any home. My E15 is dead quiet, even with my ears next to it, and I didn't have to anything extra to get it that way.

Fingers too quick. In my above post, I meant "I didn't have to DO anything to get it that way."

Mine is dead quiet all the time unless my wife uses one particular curling iron. That thing introduces the DC offset into my AC line.

So I would assume it is a rare occurrence caused by random other equipment on your same power circuit. With the exception of the one guy earlier who said it was coming from outside his house, I bet most of the time you could trace it down to something in your house if you hear it.

One thing to take note is that it doesn't necessarily mean the Rythmik amps are poorly designed. Take Emotiva for instance. They introduced the CMX-2 to get rid of this problem on their own amps. So it sounds like something that just might be common to all types of amps that have this sort of transformer in them if subjected to a DC offset in the AC line.