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Post by marcl on Oct 11, 2024 16:04:32 GMT -5
When you finally decided you wanted to go 'open baffle', what parameters did you look at for the woofers? Or what ratio of TS parameters makes for a good open baffle driver? Sorry I missed this last week. The simple answer is I had seen the GR Research DIY kits a long time ago, read about people building them and heard everyone rave about the results. I researched OB designs and couldn't find any reason to prefer an H or W frame. I know one guy from the Planar Asylum who built a 2x12 GR and did a lot of testing ... but then he continued to experiment with other drivers, amps and his own DSP because he was integrating them with further DIY projects. I believe he needed it to play to a higher frequency too. I also have been following the Magnepan concept that they pitched as the "30.7 for Condos" with a woofer made from eight 6 1/2" drivers mounted on a V shaped open baffle and powered with 1000 watts and tuned with DSP. I have heard this speaker three times since 2019. And ... I have a friend who does consulting for Magnepan and we discussed that design (which I did consider) as well as the GR-style design. Wendell told me at AXPONA 2023 that he was also looking at open baffle sub designs with larger drivers, since his V woofer was not actually a sub. I liked the idea of the servo amps matched to the speakers ... GR sells these drivers specifically to use in open baffle designs, and Rythmik makes a modified version of their amp with the shelf filter built in to compensate for the dipole cancelation in this specific design. So rather than go off on a fishing trip for other ways to do this I went with the GR kit. I didn't buy the cabinet kit from them just due to cost and complexity, and I was able to get them built to the GR plans locally. I could not find any actual test data on the GR subs ... no specs on exactly how low they could play (all Danny would say was "into the teens"), or the specific measurable benefits of the servo amp. So I decided I would look at this as an engineering project too ... to quantify the results ... as I have documented earlier in this thread. Here are the TS parameters for the drivers.  It was very satisfying to verify the FS when I tested with a regular amp with no servo or shelf filter. And it was interesting to back into the shelf filter parameters with my miniDSP HD. So I could have achieved the frequency response results with a miniDSP and different drivers, and I could then have used any amp I wanted to use including higher power ... but I could not have the servo functionality. |
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Post by marcl on Oct 11, 2024 16:07:02 GMT -5
Can post a video of those babies moving air? Sorry I don't have a way to post a video here. But I assure you that during testing they used all 16mm of that XMax ... and complained abruptly when I asked for more! |
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Post by marcl on Oct 11, 2024 16:18:26 GMT -5
Today I did a couple things that I would not have thought to be related but they ended up being .... First, I shut off the L/R amps so only the L/R subs would play. Then I sat on the couch with my trackball beside me and the REW signal generator up on the TV. I went though this matrix, setting the frequency and raising the level until I could hear the sine wave. The reason for the chart is that I intend to have my wife do this test so I created this semi-random matrix to use when playing the tones for her.  What I determined for myself was that I could locate the tones left, center or right down to 30Hz. Sometimes one of the tests felt inconclusive but in the next test clearly distinguishable. For example, if the center seemed skewed a bit to the left I wasn’t sure … but when I actually played the left they were clearly distinguishable from each other; or, if the right seemed skewed toward center, when I played the center it was easily distinguishable from the right. 20Hz was a bit inconclusive because some rattles gave it away. Hence the now related part of my day. At 20Hz the 180lb sub was rattling on the metal frame with spikey feet on which it was perched. So ... I laid them down and screwed the spikey feet to the bottom. And having disconnected them and moved them, I also decided to try a slight reposition closer to the side walls and a bit further from the front wall. So here they sit for further listening and testing.  |
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Post by marcl on Oct 12, 2024 10:29:05 GMT -5
Today I did a couple things that I would not have thought to be related but they ended up being .... First, I shut off the L/R amps so only the L/R subs would play. Then I sat on the couch with my trackball beside me and the REW signal generator up on the TV. I went though this matrix, setting the frequency and raising the level until I could hear the sine wave. The reason for the chart is that I intend to have my wife do this test so I created this semi-random matrix to use when playing the tones for her. View AttachmentWhat I determined for myself was that I could locate the tones left, center or right down to 30Hz. Sometimes one of the tests felt inconclusive but in the next test clearly distinguishable. For example, if the center seemed skewed a bit to the left I wasn’t sure … but when I actually played the left they were clearly distinguishable from each other; or, if the right seemed skewed toward center, when I played the center it was easily distinguishable from the right. 20Hz was a bit inconclusive because some rattles gave it away. Hence the now related part of my day. At 20Hz the 180lb sub was rattling on the metal frame with spikey feet on which it was perched. So ... I laid them down and screwed the spikey feet to the bottom. And having disconnected them and moved them, I also decided to try a slight reposition closer to the side walls and a bit further from the front wall. So here they sit for further listening and testing. View AttachmentFollowup .... I did the test with my wife today and results were substantially similar. She had to listen through the 120Hz test to get her bearings ... then from 110 down to 50 she correctly identified each test case ... Left, Right or Center. 40 and 30Hz were inconclusive. And at 20Hz there was still a small rattle that gave away the left channel ... have to make a little adjustment somewhere. |
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Post by marcl on Oct 14, 2024 8:44:11 GMT -5
Here's the final schematic of the system. Surrounds and tops are not shown, but they connect to various amps, and Bass Management crossovers are listed here. I find that after each Dirac calibration I sometimes have to tweak the crossovers a bit  I had a strange anomaly though ... is it just me, or is it because I measure everything so I know?  Somehow Dirac flipped the phase of the bass frequencies of the right channel in Saturday's calibration. This totally screwed up Bass Management which is summed to the front L/R. The issue was not a result of PEQ or Phase settings on the plate amps, because it was only with THAT Dirac set of measurements and filters ... not with the previous Sept 24 Dirac, nor with User settings and no XMC-2 PEQ. So I set Phase to 0 anyway ... and turned off the plate amp PEQ anyway ... remeasured, and let Dirac deal with the huge 40Hz peak. This is a good Dirac measurement with the peak at the same level for L/R and Center Sub (all playing through the dipole subs).  It seems that pulling down that 40Hz peak (whether I do it with PEQ in the plate amp, or let Dirac do it) results in a phase issue at 40Hz and causes a "glitchy" response right there - especially in the right channel - when viewed with no smoothing. IIR filters do affect phase!  But with Psychoacoustic smoothing it looks nice!  |
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ttocs
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Post by ttocs on Oct 14, 2024 9:35:58 GMT -5
Here's the final schematic of the system. Surrounds and tops are not shown, but they connect to various amps, and Bass Management crossovers are listed here. I find that after each Dirac calibration I sometimes have to tweak the crossovers a bit View AttachmentI had a strange anomaly though ... is it just me, or is it because I measure everything so I know? :D Somehow Dirac flipped the phase of the bass frequencies of the right channel in Saturday's calibration. This totally screwed up Bass Management which is summed to the front L/R. The issue was not a result of PEQ or Phase settings on the plate amps, because it was only with THAT Dirac set of measurements and filters ... not with the previous Sept 24 Dirac, nor with User settings and no XMC-2 PEQ. So I set Phase to 0 anyway ... and turned off the plate amp PEQ anyway ... remeasured, and let Dirac deal with the huge 40Hz peak. This is a good Dirac measurement with the peak at the same level for L/R and Center Sub (all playing through the dipole subs). View AttachmentIt seems that pulling down that 40Hz peak (whether I do it with PEQ in the plate amp, or let Dirac do it) results in a phase issue at 40Hz and causes a "glitchy" response right there - especially in the right channel - when viewed with no smoothing. IIR filters do affect phase! View AttachmentBut with Psychoacoustic smoothing it looks nice! :D View AttachmentThis kind of stuff is good for all to know so when folks say it doesn’t sound good with a Dirac filter, they may want to check to see why that might be. Without actual measurements for verifying what’s going on, how would one know why it sounds bad or odd? |
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Post by marcl on Oct 14, 2024 10:25:12 GMT -5
Here's the final schematic of the system. Surrounds and tops are not shown, but they connect to various amps, and Bass Management crossovers are listed here. I find that after each Dirac calibration I sometimes have to tweak the crossovers a bit View AttachmentI had a strange anomaly though ... is it just me, or is it because I measure everything so I know? Somehow Dirac flipped the phase of the bass frequencies of the right channel in Saturday's calibration. This totally screwed up Bass Management which is summed to the front L/R. The issue was not a result of PEQ or Phase settings on the plate amps, because it was only with THAT Dirac set of measurements and filters ... not with the previous Sept 24 Dirac, nor with User settings and no XMC-2 PEQ. So I set Phase to 0 anyway ... and turned off the plate amp PEQ anyway ... remeasured, and let Dirac deal with the huge 40Hz peak. This is a good Dirac measurement with the peak at the same level for L/R and Center Sub (all playing through the dipole subs). View AttachmentIt seems that pulling down that 40Hz peak (whether I do it with PEQ in the plate amp, or let Dirac do it) results in a phase issue at 40Hz and causes a "glitchy" response right there - especially in the right channel - when viewed with no smoothing. IIR filters do affect phase! View AttachmentBut with Psychoacoustic smoothing it looks nice! View AttachmentThis kind of stuff is good for all to know so when folks say it doesn’t sound good with a Dirac filter, they may want to check to see why that might be. Without actual measurements for verifying what’s going on, how would one know why it sounds bad or odd? There have been times when Dirac did something unpredictable and the solution was just to remeasure. One thing I could try is to use the plate amp PEQ to just knock 3-4db off the top of the peak and then let Dirac do the rest. Maybe the issue is going to the extreme of like -12db cut with a high Q. |
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Post by marcl on Oct 16, 2024 17:17:26 GMT -5
Broke in? I think my subs are broke in! Listening today there's like a whole 'nother layer under the Vivaldi. Makes sense, of course ... they are mechanical devices and I've been playing them now for around 3 weeks. But wow it does sound different. So guess what ... tomorrow I'll see if it's ... MEASURABLE! |
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ttocs
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Post by ttocs on Oct 16, 2024 18:33:34 GMT -5
Broke in? I think my subs are broke in! Listening today there's like a whole 'nother layer under the Vivaldi. Makes sense, of course ... they are mechanical devices and I've been playing them now for around 3 weeks. But wow it does sound different. So guess what ... tomorrow I'll see if it's ... MEASURABLE! :D I've never been able to measure it, and I've tried. I think the issue is that it's so subtle, but noticeable, just a bit more life after mechanically loosening up. |
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Post by leonski on Oct 16, 2024 19:07:06 GMT -5
People's perception of what comes in the ear is not just a 'duplicate'.......There is some software in between. It is very likely that changes in speakers from 'new' to 'broken in' are changes in YOU.
The only exception to this I've noted is when I played my Maggies for the first from New In Box.....For the first couple hours, I'd hear a very short duration drop out. That has not happened since and
only a few times at that....
My thought was that the crossover caps were 'forming'. If my model is right, that may account for the wide variety of speakers producing pleasant Music for the owner....
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Post by marcl on Oct 16, 2024 19:09:59 GMT -5
Broke in? I think my subs are broke in! Listening today there's like a whole 'nother layer under the Vivaldi. Makes sense, of course ... they are mechanical devices and I've been playing them now for around 3 weeks. But wow it does sound different. So guess what ... tomorrow I'll see if it's ... MEASURABLE! I've never been able to measure it, and I've tried. I think the issue is that it's so subtle, but noticeable, just a bit more life after mechanically loosening up. I'm sticking with "visceral immediacy" ... becoming more evident, it seems. Like the music has a bit more of a layer under it ... but not louder. |
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Post by fbczar on Oct 16, 2024 19:18:08 GMT -5
I've never been able to measure it, and I've tried. I think the issue is that it's so subtle, but noticeable, just a bit more life after mechanically loosening up. I'm sticking with "visceral immediacy" ... becoming more evident, it seems. Like the music has a bit more of a layer under it ... but not louder. I’ve heard great subwoofers described as delivering “articulate” bass. I have heard some great, musical subwoofers, that provide layering as you describe, but never an OB subwoofer. OB subs are absent the problems of SBIR and yours have Rythmic power. They must be addictive. |
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ttocs
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Post by ttocs on Oct 16, 2024 20:02:08 GMT -5
People's perception of what comes in the ear is not just a 'duplicate'.......There is some software in between. It is very likely that changes in speakers from 'new' to 'broken in' are changes in YOU. The only exception to this I've noted is when I played my Maggies for the first from New In Box.....For the first couple hours, I'd hear a very short duration drop out. That has not happened since and only a few times at that.... My thought was that the crossover caps were 'forming'. If my model is right, that may account for the wide variety of speakers producing pleasant Music for the owner.... When I received my Martin Logan Expression 13A speakers I kept a running log during break-in. The woofers didn't need long to resolve into where they sounded like they would from then on, about 50 hours. But the panels exhibited some traits that just didn't sound good until after 130 hours, with the most notable being a very shrill sounding guitar note on a Santana recording, Moonflower album. That shrill note was PIERCING until after 130 hours, so that note would have been picked up in a RTA measurement, but when using REW sweeps it wasn't. So sweeps don't replicate a listening experience. These speakers needed lots of time at higher volume levels to shake out the demons, of which there were few, but they were there. At lower volume levels it takes a lot longer for this to happen, which is why there are so many different stories of how long it takes. In my case I noted that all of the break-in process was at 90-95dB, which was easily accommodated in my house, but would be tough for someone in an apartment with close neighbors. |
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Post by KeithL on Oct 17, 2024 8:20:09 GMT -5
When it comes to electronics I would be inclined to agree with you... most of what most people attribute to "break-in" is simply use becoming "used to" what a piece of ear sounds like. (And things like modern capacitors really shouldn't change much past the first few minutes at most.) However, when it comes to speakers, and especially dynamic drivers, the opposite is true. I very much doubt that the capacitors in a crossover are going to change much in the first few hours, or the first few hundreds of hours. And, likewise, the mass of the moving parts (the cone) isn't going to change much. However the springiness and squishiness of the suspension will definitely change - possibly significantly. This will shift the free-air-resonance... probably a bit lower... and may also affect the mechanical damping of the driver. When you see published specs, on both complete speakers and separate drivers, they are assumed to be taken "after at least some break-in" or "when broken in". And this will affect different types of speakers differently as well. For example, it will probably affect bass reflex speakers more than sealed speakers, because their cabinets are actually tuned to the driver... (And, if the tuning of the cabinet doesn't match the parameters of the driver, then the system will act somewhat differently.) Whereas, while a sealed speaker will be directly affected by the change in spring constant, with a softer spring allowing a bit more low bass extension, there is no specific "tuning" involved. And, in the case of open baffle drivers, where all of the drivers' mechanical damping is provided by the driver's suspension, I would expect that to change the sound as the damping changes. (This is one reason why, if you're actually measuring brand new woofers, it's recommended that you play test tones for a day first, so the moving parts "get fully loosened up" before you take measurements.) People's perception of what comes in the ear is not just a 'duplicate'.......There is some software in between. It is very likely that changes in speakers from 'new' to 'broken in' are changes in YOU. The only exception to this I've noted is when I played my Maggies for the first from New In Box.....For the first couple hours, I'd hear a very short duration drop out. That has not happened since and only a few times at that.... My thought was that the crossover caps were 'forming'. If my model is right, that may account for the wide variety of speakers producing pleasant Music for the owner.... |
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Post by KeithL on Oct 17, 2024 8:36:44 GMT -5
One important thing to look for, first and foremost, is high power handling and as much VMax as possible. In very simple terms the actual drivers in an open baffle sub have to move a LOT more air to get the job done. For one thing, in a tuned cabinet with a port, at the tuned frequency the port is providing almost all of the output. The port actually acts to reduce the movement of the driver itself at the tuned frequency. And, with a tuned passive radiator, the passive radiator is often larger, and or has more range of motion, than the actual powered driver itself. In contrast, with an open baffle, not only do the drivers have to do all the work, but there is a 12 dB/octave LOSS below what would otherwise be their tuned frequency. So, for every octave below that, you have to feed in more power, and the drivers have to move more air, for a given amount of acoustic output. This is significant for a regular woofer and a LOT more significant for a sub that may be asked to go a couple of octaves lower. So, for an open baffle sub, you need a lot of movement, with low THD over that range of movement, and plenty of power handling to drive it. In contrast, with a sealed or tuned cabinet, you may be feeding the driver as much, or even more power, but it won't have to move as far. You also want a driver that has a reasonable amount of mechanical damping of its own... This is even more significant if you're NOT using amplifiers with their own servo stuff built in. And, if you do plan to use an amp with servo circuitry in it, then you need a driver with that separate feedback coil... which is NOT something most drivers have. I would be inclined to stick with drivers recommended as working well with a particular amp if that's an option... since "servos" are by no means all the same in how they work. When you finally decided you wanted to go 'open baffle', what parameters did you look at for the woofers? Or what ratio of TS parameters makes for a good open baffle driver? |
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Post by PaulBe on Oct 17, 2024 8:50:22 GMT -5
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Post by marcl on Oct 17, 2024 8:53:32 GMT -5
When it comes to electronics I would be inclined to agree with you... most of what most people attribute to "break-in" is simply use becoming "used to" what a piece of ear sounds like. (And things like modern capacitors really shouldn't change much past the first few minutes at most.) However, when it comes to speakers, and especially dynamic drivers, the opposite is true. I very much doubt that the capacitors in a crossover are going to change much in the first few hours, or the first few hundreds of hours. And, likewise, the mass of the moving parts (the cone) isn't going to change much. However the springiness and squishiness of the suspension will definitely change - possibly significantly. This will shift the free-air-resonance... probably a bit lower... and may also affect the mechanical damping of the driver. When you see published specs, on both complete speakers and separate drivers, they are assumed to be taken "after at least some break-in" or "when broken in". And this will affect different types of speakers differently as well. For example, it will probably affect bass reflex speakers more than sealed speakers, because their cabinets are actually tuned to the driver... (And, if the tuning of the cabinet doesn't match the parameters of the driver, then the system will act somewhat differently.) Whereas, while a sealed speaker will be directly affected by the change in spring constant, with a softer spring allowing a bit more low bass extension, there is no specific "tuning" involved. And, in the case of open baffle drivers, where all of the drivers' mechanical damping is provided by the driver's suspension, I would expect that to change the sound as the damping changes. (This is one reason why, if you're actually measuring brand new woofers, it's recommended that you play test tones for a day first, so the moving parts "get fully loosened up" before you take measurements.) People's perception of what comes in the ear is not just a 'duplicate'.......There is some software in between. It is very likely that changes in speakers from 'new' to 'broken in' are changes in YOU. The only exception to this I've noted is when I played my Maggies for the first from New In Box.....For the first couple hours, I'd hear a very short duration drop out. That has not happened since and only a few times at that.... My thought was that the crossover caps were 'forming'. If my model is right, that may account for the wide variety of speakers producing pleasant Music for the owner.... I know for a fact that Magnepans are specifically designed with over-tension in the diaphragm that is intended to relax a specific amount over time, or with some encouragement by playing them. There are actually Sharpie marks on the tension crank for each speaker model. The bass gets a little deeper and the mids and highs less harsh. My 3.7s are getting on 13 years old and I asked a dealer if the ribbon tweeters ever degrade. He said that Magnepan says they settle out after a year and a half, but then in time they can lose tension and shift a bit and the tiny drops of glue suspending the aluminum foil can break down. I can have a local dealer replace them for me for a reasonable cost and I'll be doing that when he gets his shipment. It's interesting about cone drivers like a big heavy woofer. Yes the typical design has the surrounds kind of massive and stiff to control the "rebound" and stop the cone. And it makes sense that after some break-in this will become predictably more compliant. My drivers for the dipoles have an interesting twist though. They are intentionally made to be used with the servo amp, and so they can be lighter and more compliant to start with because the amp contributes to actively driving them back to stop. I absolutely am aware of my cranial software changing day to day - including dependency on sinus and Eustachian tube congestion. I remember a couple days after I got the second sub built they sounded astonishingly good. Then a few days later I was not as surprised by how they sounded. I expected to get used to them. But this week there is a clear difference since I made some adjustments, reran Dirac, and continued to listen a lot more. I really like how it's most evident at lower listening levels. And ancient history ... I had to specify some kind of elastomer to rest under the keys of a synthesizer back in the late 80's and I needed a specific consistent compression and rebound ... and it had to be consistent over some years of use. Poron was the perfect choice ... compressed 50% with moderate pressure and continued to rebound for many many hours of use. So I'm sure speaker surround materials are chosen for predictable behavior ... until they inevitably crumble to dust, as they are wont to do after 20 years or so. |
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Post by KeithL on Oct 17, 2024 9:26:46 GMT -5
That is an excellent point... and one that most people tend to overlook... and one that also affects recordings significantly. Attend a small performance ... at a bar or night club. Sit your favorite high quality self contained stereo recorder on the table in front of you. Take normal precautions... put something soft on the table... make sure nothing is blocking the microphones... Record the performance... You would think that you're going to get "an exact copy of what you were listening to"... Now listen to your recording... with no processing and no editing... You'll find that your "direct to file recording" often sounds nothing like what you heard sitting there... In fact, it takes a lot of editing, and processing, and a considerable amount of skill... To make a recording that "sounds like nothing was done to it"... And that "sounds just like you were sitting right there"... If it's even possible at all... Similarly, with speakers, the actual mechanisms involved are very different than the way what you're listening to was produced... For example, with a piano, or a violin, you have different harmonics, coming from different parts of the instrument, and going off in different directions... A lot of that "information" isn't in even the best recording... and your speakers couldn't reproduce it accurately if it was... So, at best, what you're hoping for is "a good enough simulation to fool your ears and your brain"... People's perception of what comes in the ear is not just a 'duplicate'.......There is some software in between. It is very likely that changes in speakers from 'new' to 'broken in' are changes in YOU. The only exception to this I've noted is when I played my Maggies for the first from New In Box.....For the first couple hours, I'd hear a very short duration drop out. That has not happened since and only a few times at that.... My thought was that the crossover caps were 'forming'. If my model is right, that may account for the wide variety of speakers producing pleasant Music for the owner.... |
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Post by leonski on Oct 17, 2024 16:31:08 GMT -5
Here are some properties of Mylar. I don't see it as being THAT stretchy...... www.matweb.com/search/datasheet_print.aspx?matguid=981d85aa72b0419bb4b26a3c06cb284dOther data sheets online for other 'versions' of mylar. When put to the test, I would expect SOME deformation which is permanent followed by an abrupt failure as more tension is applied.... Mylar doesn't hold much energy. What does Magnepan use? 1/4mil? 1/2mil? But I DO agree with choice of materials. We used elastomers designed to be Extremely Chemical Resistant......And in some cases needed to be replaced during periodic maintenance...... I think that was Kalrez, which have the addtional advantage of being $$$$. Metal seals work but would deform once when compressed than replace if the seal is broken. Spark Plugs on your auto may have a washer which is actually compressible ONCE. I had a jar of washers used to replace IF I had to pull a plug than replace. I'd expect, for example, that a speaker surround breaks in rapidly....a matter of an hour or so at some level....80 to 85db? Than remain good for a LONG time.....Unless left out in the sun or exposed to high temps or other 'abuse'.....Cold might be OK, if the speaker is NOT being used.... As for the rest of Keiths beef? You lost me at 'microphone'...... But I might add that to capture an orchestra? You can go either of 2 ways....... Put a L / C / R microphone out in the 'audience'......Rely on the constructed acoustics to 'blend' the sound. I think Sheffield labs did this back in the 80s and I have some Telarc which are superb recordings. Or you can go nuts and close-mic each instrument or have some kind of large array of mics. I could see this turning into an engineering disaster. Or just drive you NUTS... As an aside? When I experimented with the original '4 channel' system....a phase thing.....I would recover a LOT of ambiance and on a select few recordings, (vinyl in those days!). QS / SQ and other matrix schemes ultimately failed, but it WAS an interesting experiment. |
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Post by marcl on Oct 29, 2024 2:01:59 GMT -5
I wanted to see how the subs perform aimed straight into the long length of the room perpendicular to the side walls, vs 30 degrees toed in. I was hoping to see a positive change in how much they engage the length resonance mode, potentially reducing the decay time. What I found was at 30 degrees there is a rise in level of about 3db from 60-100Hz. That would be nice, though it doesn’t buy me much because Dirac flattens that range just fine. But, I also found that the decay time of the resonances at 40Hz and slightly below were extended on the waterfall and decay plots … like 60ms longer. That’s not good … I was actually hoping for the opposite. So I put them back to aiming straight down the length. Acoustic centers around 3ft from the side walls and 7 1/2ft from the front wall.   |
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Somehow Dirac flipped the phase of the bass frequencies of the right channel in Saturday's calibration. This totally screwed up Bass Management which is summed to the front L/R. The issue was not a result of PEQ or Phase settings on the plate amps, because it was only with THAT Dirac set of measurements and filters ... not with the previous Sept 24 Dirac, nor with User settings and no XMC-2 PEQ. So I set Phase to 0 anyway ... and turned off the plate amp PEQ anyway ... remeasured, and let Dirac deal with the huge 40Hz peak. This is a good Dirac measurement with the peak at the same level for L/R and Center Sub (all playing through the dipole subs).
