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Home » Audio » Speaker » Futzing with vibration control
| Futzing with vibration control [message #92514] |
Sun, 25 October 2020 16:12  |
Barryso
Messages: 204
Registered: May 2009
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Master |
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Another interesting tweak. Did something similar with the 2 pi towers a while back but now it's with the 4 pi's.
Used cheap rubber isolation feet under the subs and speakers. These are the feet that will prevent washers and dryers from walking around the floor and are available at hardware stores. They are somewhat like large vibrapods but tend to only cost a dollar or two each.
The living room has a suspended wood floor with some parts of it being worse than others. Long story, just know that the floor is the biggest sonic issue in the room.
Added a set of these rubber footers to a sub and listened. The footers removed some interaction with the floor, some sort of smearing, and made a very nice improvement. Added footers to another sub and it got even better so it continued until all three subs were isolated. Even the subs that are on the "good" part of the floor sound a lot better.
The 4 pi's are also on the floor and have felt on their feet for some modest vibration control. More rubber footers were ordered. The results were pretty similar to what happened with the subs, it cleaned up bass smearing and resonances.
It is not a subtle improvement. There's more clarity, cleaner tone and a whole lot of wow moments.
It changed things enough that some mediocre recordings are now sounding pretty good. That floored me as they just seemed to be bad recordings rather than something going on with the system. Who knew? Good recordings are better than ever.
If you have a wood floor it's worth a try. In my room it's equal to, or greater than, a big ticket gear upgrade.
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| Re: Futzing with vibration control [message #92594 is a reply to message #92593] |
Fri, 13 November 2020 16:36  |
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Wayne Parham
Messages: 18786
Registered: January 2001
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Illuminati (33rd Degree) |
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It's an interesting observation, isn't it Barry?
You know, in the 1980s and 1990s, I used only solid-state amps. I was quality conscious, so I used good equipment but none of it was tube gear. So I was familiar with these speakers on amps that could deliver 100 watts easily. Some of my gear went as high as several thousand watts - and the speakers could handle it - but it was silly power for home hifi or even home theater. It literally damages the house. Drywall shakes loose, exposing the fasteners and built-in cabinetry becomes loose too. It's just nuts.
Still, a good 100 watt amplifier sounds great on these speakers. It's more than enough, so dynamic range is great. And as you said, the woofers really "wake up" when you give 'em a little juice.
Now you're seeing something about the 2226 that we've talked about, but not lately. You may remember a few discussions that we've had over the years. The 2226 actually changes its electro-mechanical characteristics when it's used at power levels over a few watts. All speakers do this, but the 2226 is noticeably so. It was made to be used at several hundred watts, after all.
So it's not just the damping factor here. In fact, in this case, it's mostly not the damping factor but the electro-mechanical parameter shift. The loudspeaker system was designed with this in mind, and it uses an alignment that prevents the thermal shift from going into an underdamped condition at extended full-power periods. It is slightly overdamped at moderate power levels, and a little more overdamped at low power levels. It doesn't shift far enough to be underdamped even at full power, so you can throw hundreds of watts at it and it won't get a peaky underdamped curve. But it is much more overdamped under a watt than it is over a watt.
This is one of the handful of reasons why flanking subs are so nice for these speakers. Even with moderate to high power levels, flanking subs provide extension and baffle step correction and mitigation of SBIR and higher-frequency room modes. But when low-power tube amps are used, it is even more helpful because we're not just facing baffle step but also the overdamped alignment.
Anyway, all that to say I can understand your impressions here. I'm really familiar with these speakers at higher-power levels and the effortless impact and punch they give. You don't ever get there on just a watt or even ten watts. They're much more polite with SET power. Hit 'em with fifty or a hundred watts though and they show their other side. They remind you of all the best and most powerful concerts you ever heard. I kinda like to give the knob a twist every so often to get 'em back there. 
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| Re: Futzing with vibration control [message #92626 is a reply to message #92621] |
Tue, 17 November 2020 11:25 |
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Wayne Parham
Messages: 18786
Registered: January 2001
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Illuminati (33rd Degree) |
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There are definitely differences between amps, and one of the things to watch for is low-level behavior. Amps that are designed to run higher-power levels sometimes aren't as clean at very low power levels. That's what the headphone amp guys watch out for in their amps. Tube amp guys often do too.
Some artifacts aren't as noticeable at higher levels as they are at low levels, because the anomaly is proportionally lower at higher power levels. An example is crossover distortion, and by "crossover" here I don't mean the filters used to distribute various frequency bands to appropriate subsystems, but rather the circuit behavior as the input signal waveform passes from positive to negative and back again.
The zero-crossing region is a potential place for error, because active device characteristics shift as the signal level goes lower than their turn-on bias level. They go from linearly conducting with an output signal that's proportional to the input signal to simply shutting off. This effectively loses the lowest level signal, that which is below the turn-on bias level. That's why push-pull amps are never purely (Class B) push-pull when used for audio - each section is biased so it stays conductive through the zero crossing line, which is called class AB.
As for the line splitter for your subs, I've seen this before. Pretty often, actually, and if we've discussed it before forgive me for talking about it again now.
You're definitely right that the output impedance of the preamp or source - whatever is driving the line being split - has an influence on the signal when the load is shifted. If the output impedance is really low and the drive level strong, then the load can be shifted pretty drastically without much effect. But if the output impedance isn't all that low, then the drive signal isn't strong and the load can swamp it. Sometimes a higher load (from splitting or whatever else) just causes a drop in amplitude but sometimes it even changes the response. If the load or the source aren't purely resistive, then a changing load will alter the response.
And resistive attenuators can cause fits too. Most have an input and an output, with the input being across a fixed resistance and the output being across the potentiometer wiper and a common lead. If the resistive attenuator is connected backwards, then the source output has a changing load which is dependent on the position of the attenuator. If the attenuator is set for high attenuation, then the source is pretty much shorted. So if a preamp output is split, and a passive attenuator is placed on the mains line - to match SPL with the subs, for example - then there is a possibility of this occurring. If the attenuator is installed backwards, it will give the source equipment an increasingly excessive load as attenuation is increased. It will be very difficult to get the levels matched and often times sounds will just plain sound weird.
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