So as a quick life update, I'm graduating from my program with my Masters, and have decided to take a job at the University of Illinois Urbana Champaign as a data analyst. This obviously necessitates a move on my part, and with 3 Abbey's, 2 Bandpass Subs, 2 ULF subs, 4 surrounds, and numerous other bits of electronics (including a projector and 100" screen), I'm finding a need to be creating in moving all this stuff. I've been boxing up the Abbey's and subs. The Subs were easy, I bought a 20x20x20 doublewall box, wrapped the sub in plastic wrap, used 8 foam corners, and that seems good enough to protect those. The abbey's are a lot tougher. Besides the fact that they weight a good 70lbs or so, they are an akward size and shape. The heavily radiused front baffle makes it so that normal foam corners don't really stay on it in the same way. Second problem, they are just big enough that normal boxes aren't really available to hold them. I specially ordered 3 boxes that are 30x20x18. This was as close as I could get. I've then cut the box down slightly to make it only 15" deep, but the length and width is about 1" less than I would have preferred. Problem three, the weight of the speakers is enough to actually cause these double wall heavy duty boxes to weaken. They have a 500lb burst weight, but I'm not seeing it. I'm probably going to need to get those reinforced fiber corners to reinforce the boxes.
My silly plea that will have no immediate impact to Dr. Geddes: Find a way to make the enclosures about 30lbs lighter and 1" shorter and narrower.
On a more serious note, do you think that removing the woofers from the enclosures would make them better protected in shipping, or worse? It would reduce the weight of the speakers by a good 10 or 15lbs or so, but then I would need to pack the drivers well. Still, I feel like a contributing factor to a product being damaged in transit is it's weight, heavier items are harder for movers to handle, and are more likely to be thrown, dropped, smashed, etc.
I also have my own home made ULF subwoofer which has a total weight tipping the scale at more than 200lbs. What was I think?????? I think the only sane way to move this is to remove the drivers and amp, remove the floor spikes, wrap it in a moving blanket, and treat it like a big heavy table or something. It probably should be crated and palletized at it's weight and size for safest moving, but at that point it would be cheaper for me to make a new enclosure. Maybe one out of Styrofoam and carbon fiber.
My silly plea that will have no immediate impact to Dr. Geddes: Find a way to make the enclosures about 30lbs lighter and 1" shorter and narrower.
On a more serious note, do you think that removing the woofers from the enclosures would make them better protected in shipping, or worse? It would reduce the weight of the speakers by a good 10 or 15lbs or so, but then I would need to pack the drivers well. Still, I feel like a contributing factor to a product being damaged in transit is it's weight, heavier items are harder for movers to handle, and are more likely to be thrown, dropped, smashed, etc.
I also have my own home made ULF subwoofer which has a total weight tipping the scale at more than 200lbs. What was I think?????? I think the only sane way to move this is to remove the drivers and amp, remove the floor spikes, wrap it in a moving blanket, and treat it like a big heavy table or something. It probably should be crated and palletized at it's weight and size for safest moving, but at that point it would be cheaper for me to make a new enclosure. Maybe one out of Styrofoam and carbon fiber.
Matt
When I ship them I combine two 20 x 20 x 20 double weight boxes. This gives me four layers arround the middle and lots of room for padding. I have shipped them a long ways in this packaging. Leave the woofers in place - they will be fine. Pad the box not the speakers. Glue, or paste, padding to the box and let the speaker float a little, maybe 1/4 on all sides.
When I ship them I combine two 20 x 20 x 20 double weight boxes. This gives me four layers arround the middle and lots of room for padding. I have shipped them a long ways in this packaging. Leave the woofers in place - they will be fine. Pad the box not the speakers. Glue, or paste, padding to the box and let the speaker float a little, maybe 1/4 on all sides.
Thats not a bad idea, but I'm honestly not sure where to get padding. I can get packing materials around here, but foam seems to be hard to get. I can order it, but the shipping was astrinomical. One place quoted me 80 dollars to ship 100 dollars worth of foam.
I just picked up a huge role (250') of bubble wrap with the large 1/2" bubbles. I believe this could take the place of foam, I could use two layers on the walls. Between that, the wrap, and the foam corners, I think it might be well protected, no?
I just picked up a huge role (250') of bubble wrap with the large 1/2" bubbles. I believe this could take the place of foam, I could use two layers on the walls. Between that, the wrap, and the foam corners, I think it might be well protected, no?
A trip is a seriously good idea. I visited Earl when I lived in Cleveland. I've got a wife and 2 kids. Make up an excuse. I said to my wife that I am visiting a well published doctorate in acoustics, somebody who could SAVE me money in the long run with my audio hobby.
She was all for it. The rest is history.
I think Earl is being a bit conservative with his Abbey max SPL estimates, but it should be plenty for most folk. Even with peaks, most of the time the Abbey will be pumping out 110-115dB at 1 meter which translates to be about 100-105 dB for the audience. You feel like you are IN the performance.
Anand.
Am looking for an "enthusiastic" owner where I might be able to hear one of these Geddes loudspeakers and even better run a few test. Test are not necessary. St. Louis Missouri, Omaha Nebraska, Kansas City Missouri, Tulsa Oklahoma, and Denver Colorado are all possible with the center of those locations being closest. It would be great if I could bring an amp and a pair of speakers to hear side by side for something familiar. Anyone interested and nearby?
Back when I was a manufacturing used to ship equipment around everywhere on a deposit check but I know those days are long gone. This is the next best thing and could be a little fun!
Thanks,
=SUM
Back when I was a manufacturing used to ship equipment around everywhere on a deposit check but I know those days are long gone. This is the next best thing and could be a little fun!
Thanks,
=SUM
I'm south east of Denver and have a pair of Abbeys. My listening room is in the basement, so if you want to bring speakers keep that in mind. 
I'll be home on a much needed vacation the week after Memorial Day, 5/31 - 6/4 if that will work. PM or email me.
mike
I'll be home on a much needed vacation the week after Memorial Day, 5/31 - 6/4 if that will work. PM or email me.
mike
With Mike's room and experience you are in for a treat.
By next year or so, then I will wear that hat, when I have my dedicated room,built from the ground up for best acoustics only
, but I am way near the eastern seaboard.Anand.
Anand,
Congratulations! Let us all share your excitement; give us a preview of your dedicated room--is it a HT or music-only room, what's the ratio and size, what kind of construction for the walls and floor. Are you using RPGs or other acoustic treatments? I'm sure you are getting lots of inputs from Dr. Geddes. Last but not least, are you upgrading to the Summas and use the Abbeys for surround channels
John
Congratulations! Let us all share your excitement; give us a preview of your dedicated room--is it a HT or music-only room, what's the ratio and size, what kind of construction for the walls and floor. Are you using RPGs or other acoustic treatments? I'm sure you are getting lots of inputs from Dr. Geddes
. Last but not least, are you upgrading to the Summas and use the Abbeys for surround channels John
Ha, I've given thought to the idea of replacing my Abbey's with the Summa's at some point, and using my Abbey's as surrounds. It's such overkill that I would probably be better off selling them to someone else, and buying a few sets of the Harpers.
Anand, if you haven't talked with Dr. Geddes about your dedicated room, I would highly recommend it. It is my opinion that a lot of so called acoustic experts have gotten it wrong with regard to low frequency room acoustics in typical theater rooms, with attempts to some how defy the laws of physics. He is also quite astute at finding ways to overcome acoustic limitations very inexpensively (his CLD method for instance).
To get on my high horse for this again, I don't see how a company can argue that their bass absorbers are effective at imparting low frequency dampening by showing no more than a 2-3% improvement, maybe as high as 10% improvement after filling a room with their bass traps. To me, that is a small if not inconsequential improvement (Given that a 10% improvement in low frequencies cant exactly equate to an overall 10% improvement in a perception of sound quality).
Conversely (Dr. Geddes has far better real world data than I do), I have shown through room models that using his method of multiple LF sources along with utilizing the walls as the means of LF dampening can show huge improvements, in the neighborhood of over 50% improvement. I drew this conclusion through a mixture of true in room measurements for the multiple subs, and adding this data to room models, then calculating the improvement in average deviation from a reference point as a percentage.
If I actually sold products or had a company, I would use a different statistical method for representing the improvement. If you total the deviation from the refrence point it compounds the improvement, and can show things like 500% or 1000% improvements. Astrinomical and really unrealistic numbers that don't really tell the whole story. Add eq to the final measurement and you can create a response that is within +/- 1 or 2db's from 10hz to 300hz, and when room modes can be as large as 30+db's, that can create exaggerated improvements. I point this out because it shows how manufacturers, even well meaning ones, can really misrepresent the amount of improvement their product can produce. Another bad method of showing improvement is through the Cumulative Spectral Decay waterfall plot. The appearance of "ringing" is always related to the level of the initial tone at that frequency. If there is a peak, there will inevitably be a peak in the decay as well, unless something is selectively suppressing that frequency. If you add a bunch of bass traps and some eq, and you reduce the initial peaks, then the decay will also be reduced proportionately. This however doesn't mean that the bass traps and eq improved the room dampening (At least this is my rough elementary understanding). What needs to be examined to see if actual room dampening is improved would be the rate of decay relative to the level of the initial tone level. I know of ways to do this statistically from the raw data, and have even developed my own way of representing this in a single number (Let's call it Matt's Bass index), but I don't believe waterfall plots are good ways of representing it. The only way I could see a plot properly representing it would be to set the first line to a flat zero point, and have every other line be the relative deviation from that zero point. However, I don't believe this is done (stereophile may, I'm unsure of how the put together their polar data and SDP's), and I believe that the average consumer would misread these graphs and thus misunderstand what the data is telling them.
Anand, if you haven't talked with Dr. Geddes about your dedicated room, I would highly recommend it. It is my opinion that a lot of so called acoustic experts have gotten it wrong with regard to low frequency room acoustics in typical theater rooms, with attempts to some how defy the laws of physics. He is also quite astute at finding ways to overcome acoustic limitations very inexpensively (his CLD method for instance).
To get on my high horse for this again, I don't see how a company can argue that their bass absorbers are effective at imparting low frequency dampening by showing no more than a 2-3% improvement, maybe as high as 10% improvement after filling a room with their bass traps. To me, that is a small if not inconsequential improvement (Given that a 10% improvement in low frequencies cant exactly equate to an overall 10% improvement in a perception of sound quality).
Conversely (Dr. Geddes has far better real world data than I do), I have shown through room models that using his method of multiple LF sources along with utilizing the walls as the means of LF dampening can show huge improvements, in the neighborhood of over 50% improvement. I drew this conclusion through a mixture of true in room measurements for the multiple subs, and adding this data to room models, then calculating the improvement in average deviation from a reference point as a percentage.
If I actually sold products or had a company, I would use a different statistical method for representing the improvement. If you total the deviation from the refrence point it compounds the improvement, and can show things like 500% or 1000% improvements. Astrinomical and really unrealistic numbers that don't really tell the whole story. Add eq to the final measurement and you can create a response that is within +/- 1 or 2db's from 10hz to 300hz, and when room modes can be as large as 30+db's, that can create exaggerated improvements. I point this out because it shows how manufacturers, even well meaning ones, can really misrepresent the amount of improvement their product can produce. Another bad method of showing improvement is through the Cumulative Spectral Decay waterfall plot. The appearance of "ringing" is always related to the level of the initial tone at that frequency. If there is a peak, there will inevitably be a peak in the decay as well, unless something is selectively suppressing that frequency. If you add a bunch of bass traps and some eq, and you reduce the initial peaks, then the decay will also be reduced proportionately. This however doesn't mean that the bass traps and eq improved the room dampening (At least this is my rough elementary understanding). What needs to be examined to see if actual room dampening is improved would be the rate of decay relative to the level of the initial tone level. I know of ways to do this statistically from the raw data, and have even developed my own way of representing this in a single number (Let's call it Matt's Bass index), but I don't believe waterfall plots are good ways of representing it. The only way I could see a plot properly representing it would be to set the first line to a flat zero point, and have every other line be the relative deviation from that zero point. However, I don't believe this is done (stereophile may, I'm unsure of how the put together their polar data and SDP's), and I believe that the average consumer would misread these graphs and thus misunderstand what the data is telling them.
pjpoes, good post. I'm also an Abbey owner and have built 3 dedicated audio rooms over the years and am getting ready to do a 4th within the next couple of months. In my first two rooms I used heavy tube trapping and fell into the trap (pun intended) of overdamping the room in the process. In my 3rd room I used an on-wall system of diffusion, diffraction and absorption panels called ARS will great success. The acoustician who helped design the room used RT60 as a key metric for tuning the room (among other measurements).
My latest room will be a mixed use room - my other rooms were dedicated closed/sealed rooms for music only. I think Earl's multi-sub approach will help me get the flat LR response I want without trapping. My plan is to use broadband absorption on the wall behind the speakers and, if I absolutely need to, a couple of corner traps.
My latest room will be a mixed use room - my other rooms were dedicated closed/sealed rooms for music only. I think Earl's multi-sub approach will help me get the flat LR response I want without trapping. My plan is to use broadband absorption on the wall behind the speakers and, if I absolutely need to, a couple of corner traps.
I won't claim that this is true, only what I have been told, but I have heard that RT-60 was developed for use in large room acoustic environments and this is inappropriate for small rooms like home theaters. However, I would agree that, if nothing else, RT-60 is a method that follows the same approach and is used by many acoustician. The question here is whether the method of calculation fits small room acoustics appropriately. However, I've never seen an acoustics manufacturing company indicate improvement of their devices via the RT60 method.
By the way, I don't think there really is such thing as too much LF dampening, but if you follow what is commonly recommended and use a lot of broad band absorption, you could end up with too much broad band dampening in that there is too much mid and high frequency absorption.
I haven't had the luxury of building a dedicated room for myself yet. In stead I rent and will for some time to come, so what I've done is transform pre-existing rooms into spaces dedicated to my purposes through add-ons. This means I have not yet been able to use Dr. Geddes CLD approach myself, I recommend it based on the underlying theory of it's operation. It's basically like a giant panel trap, which is exactly what you need/want. Small pre-made traps simply can't offer enough low frequency absorption, and velocity absorbers are so inefficient at frequencies below 100hz that I think they are the worst option.
I'm in the process of moving, so things may/probably will change in my new room, but I have built all of my own acoustic treatments. My bass absorption consists of panels that are created from 24"x48" pieces of CLD 1/2 inch drywall, rigid rockwool that is 6 inches thick adhered to the CLD panel with the same dampening material, and flexibly suspended within a wooden frame. These are then mounted to the wall using z-clips. The Front panels are 8 inches thick because they have 2" of rockwool on the front of the panel and 4" on the rear. They were previously mounted right against the wall, but I will experiment with increased air gap for further LF dampening. I have other panels using the same basic approach by without any front rockwool so as to minimize the amount of mid/high frequency absorption. I'd like to rebuild these so that the front offers scattering/diffraction instead of simply reflection. I don't consider this ideal, but its as good as I can do for now. I'm looking into those frabric mate systems, to see if I can't modify them to fit my needs, while allowing me to cover far more of the room with these treatments.
I don't recall exactly where Dr. Geddes posted this, just that he has talked about it. I think its in his book on home theater design. I'm sure he will post and can speak for himself on this.
I recall that the method involved taking two sheets of drywall and adhering them together with dampening compound. The current popular method is to use Green Glue, and if cost isn't a big deal, this isn't a bad option. It probably works better than Dr. Geddes preferred compound. Dr. Geddes uses the casting urethane that he uses for his speakers, I believe. I know that Green Glue is primarily composed of Urethane as per it's MSDS, but I'm sure it has additives, and these may be crucial to the performance, I don't really know. There are different kinds of casting urethane as well, and again, I don't know which of these is best. The standard best method is to then attach the drywall to hat channels, with insulation behind them. While you will have far better than average performance by using any sort of insulation here, if money is no object, there are insulations with better bass performance, it just costs a lot more. All of this is standard practice, the biggest difference between what Dr. Geddes does and what is most common is the CLD approach, and this is no longer unique to him, as this is what Green Glue proposes (among others). This method also offers extremely high STC ratings as well, which helps keep your sound out of the rest of the house. I believe that if you use steel stud construction in conjunction with all of this, you could be looking at STC ratings in the high 60's to low 70's quite easily.
That is true, and its also true that the concept of RT-60 requires a statistical sound field, in other words it isn't applicable to LFs in small rooms. You will get a number, but what does it mean? At LF were the modes are discrete damping and Q of the resonance are the same thing, just different numbers, but they measure the same thing. So if you looked at the change in Q of a resonance that would be the change in the damping or sound absorption. But this gets tough with multiple low Q modes like my room has. There RT-60 might work, but its ill defined in that situation.
Its in my book. If I get the time I'll review it here, but I'mm swamped at the moment.
Dr Geddes, this was my understanding as well, I re-reviewed the articles I had previously read, and basically state the same thing that you do. I have heard some argue that an RT-60 can still be used for relative measurements in a room (i.e. initial RT-60 vs treated room RT-60). However, this assumes that the number is going to be accurately and consistently measuring something (even if it is ill defined). I have pretty darn good measuring equipment, and as you have stated many times before, it doesn't even take very good equipment to accurately measure LF's, but I don't get consistent results down there. I mean, if I setup my rig, mark off my measurement location, set my stand up in a very specific way, take a measurements a few times, I will get relatively similar results. If I turn off the computer and turn it back on, then run these same measurements again, I may see something that looks generally similar, but often I will see 6+ db's difference in some of the deep nulls. This even can happen if I just keep pressing "measure" over and over again over long periods of time. Again, they share a high correlation with each other, but when people start looking for improvements of 6db's less in a null, and I see that just by accident, I no longer trust any of this.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.