Dr. Geddes, I would not expect much more than "sounding the same", as I've said, I don't see passive crossovers as inherently bad as some others seem to. The advantage to me is the ability to add in some room correction (since we are using these as LF sources), the easy ability to upload newer designs, and more importantly, the FIR filter for transient perfect at the crossover. I'm sure this effort would offer a small improvement in sound at best, but the price isn't so great either.
There is something to be said for the efficiency loss in the midbass driver too, no? I mean, again, it's a small effect on sound, but it adds inefficiency. I'd even wonder if it would allow a slightly more sensitive system. For instance, you could setup the speakers for biwiring, then use a passive crossover on the tweeter, an active on the woofer, and better yet, an FIR correction filter as well. I haven't yet seen your 3rd order crossover, but I do believe that there is roughly a .5 to 1db loss in sensitivity from the 2nd order low pass right now on my speakers, based on the sims I ran. This is due to the resistance of about .3 ohms. And that really isn't fully accurate since that is at room temp. I've heated up these inductors under a load, and found it rose drastically to almost a full ohm, and the inductance value changed. I've pulled the Abbey's apart after using them for a bit, and the crossovers are often quite warm, especially those woofer inductors, right after use. The other parts, especially those trap filters, are far less impacted unless I run test tones or such through them.
I do think that running horns with absolutely no passive filtering is not a good idea, so ultimately even if you went to a complete active system, I would think it would be beneficial to have some passive filtering. If nothing else, in the event that a signal is sent through without the active filtering in place, then the tweeter could easily be damaged.
I've heard arguments against this view before, but another issue I have with zero passive filtering is that a speakers impedance is not constant, the load the amplifier see's is not purely resistive. The filters that a good crossover designer adds smooth out this impedance and present the amplifier with a better load to drive. Thats why i think having some passive filtering is inevitable, but you can still remove the parts with the highest losses and improve the system efficiency some, no?
There is something to be said for the efficiency loss in the midbass driver too, no? I mean, again, it's a small effect on sound, but it adds inefficiency. I'd even wonder if it would allow a slightly more sensitive system. For instance, you could setup the speakers for biwiring, then use a passive crossover on the tweeter, an active on the woofer, and better yet, an FIR correction filter as well. I haven't yet seen your 3rd order crossover, but I do believe that there is roughly a .5 to 1db loss in sensitivity from the 2nd order low pass right now on my speakers, based on the sims I ran. This is due to the resistance of about .3 ohms. And that really isn't fully accurate since that is at room temp. I've heated up these inductors under a load, and found it rose drastically to almost a full ohm, and the inductance value changed. I've pulled the Abbey's apart after using them for a bit, and the crossovers are often quite warm, especially those woofer inductors, right after use. The other parts, especially those trap filters, are far less impacted unless I run test tones or such through them.
I do think that running horns with absolutely no passive filtering is not a good idea, so ultimately even if you went to a complete active system, I would think it would be beneficial to have some passive filtering. If nothing else, in the event that a signal is sent through without the active filtering in place, then the tweeter could easily be damaged.
I've heard arguments against this view before, but another issue I have with zero passive filtering is that a speakers impedance is not constant, the load the amplifier see's is not purely resistive. The filters that a good crossover designer adds smooth out this impedance and present the amplifier with a better load to drive. Thats why i think having some passive filtering is inevitable, but you can still remove the parts with the highest losses and improve the system efficiency some, no?
Short of the FIR claims - I don'y buy that linear phase stuff - I don't disagree with anything except that its worth the cost. To me, doing something that complex and expensive that doesn't improve the sound just isn't good business. You seem to like playing with the components, thats fine. There could be some benifits in a development situation, and if the amps and filters were all custom tailored to the drivers that might be worthwhile (like Genelec does). But as individual components its just way to expensive and complex for most people.
Hi all I am new to the site and this is the first post. I just ordered a pair of Abbey 12a speakers from Dr Geddes and am looking very forward to the day when I can go pick them up, but in the mean time here is my first question. I will be trying sub woofer locations and building stands for the Abbeys while they are being built. Should I build the stands to a height that puts the center of the waveguide at ear level? That seems to be logical but just wanted to make sure.
If you only have one sub, it's a good time to take advantage of the Polk PSW 10 power subs (recommended by Dr. Geddes) for $101.88 each so you can do the Geddes' multi-sub setup.
polk psw10 - Vanns.com Search
I got mine in Cherry-finish for $99.88 last week.
How long do you have to wait for your 12As?
polk psw10 - Vanns.com Search
I got mine in Cherry-finish for $99.88 last week.
How long do you have to wait for your 12As?
A few months for the Abbeys. And right now I have 4 subs that I am experimenting with location and levels using a behringer dcx 2496. I have two Thor subs 12" sealed from the Linkwitz Orion system and I also have two powered velodynes 10" ported. Until I get the Abbeys in the system I am using Definitive Technology Mythos speakers as my fronts and rears. Just "tuning" the subs by ear has made a huge difference in the overall bass of the system in either 2 channel or 5.1, and this is using 3 of the 4 subs for the time being. Thanks for the suggestion though, that is a great price for the subs.
Welcome. You are going to enjoy those speakers! Earl's original recommendation was to put the speaker centers at ear height, but many users prefer to have the waveguide centers at ear height (17-18" stands, depending on your height and seating arrangement). Personally, I didn't hear much difference when I tried several different heights, and ended up putting mine on 20" stands, which places the waveguide centers around 3" above ear height. You might want to experiment a bit to see what you prefer.
-Doug
Quite frankly, setting up subwoofer (doesn't matter if it's one or multiple) without measuring equipment will only yield substandard results. Automated solutions that work well are DSpeaker Anti-Mode 8033 or REW/BFD (Room EQ Wizard Home Page).
Earl offers calibration when you buy his subs - he might be able to help you calibrating your subs too. Just ask him.
Best, Markus
Thanks for the info Doug, I am about 3/4 of the way through the 36 page post on Audio Circle and it is a great read. Doug are you still using the stands that was pictured (beautiful job on those) in the post and did you ever put the base on them that you were talking about or did you leave them as pictured. I am going to do something very similar for stands, are those cherry wood?
Hi Markus yep I will have to do measurements on the room, I do realize that, right now I am just basically playing around with placements. I would have never believed that you could put a sub behind your listening position and not be able to tell it is there but I did and you can't tell its there. So I am just kind of familiarizing my self with the theory basics. I can see this is going to be a lot of fun setting this up, seems like a good bunch of people here. And I will certainly need assistance as I am NOT a technical expert in any way shape or form.
Hi Markus yep I will have to do measurements on the room, I do realize that, right now I am just basically playing around with placements. I would have never believed that you could put a sub behind your listening position and not be able to tell it is there but I did and you can't tell its there. So I am just kind of familiarizing my self with the theory basics. I can see this is going to be a lot of fun setting this up, seems like a good bunch of people here. And I will certainly need assistance as I am NOT a technical expert in any way shape or form.
I have mine on a 24" stand which places the center of the speaker every so slightly above ear height. Then I tipped them down to reduce the amount of ceiling they would reflect off of. My hope was to reduce early reflections without adding absorption or diffusion to my vaulted ceilings. I find this a great position for staging, response, etc.
I did try other heights, including the mapleshade recommended floor tipped up method, and feel going too high is better than too low. However, these speakers are not like other speakers, they are CD, and aiming is crucial. I think a lot of people are thrown off by the idea that the speakers have the smoothest response when aimed to cross well infront of the listener. The idea that aiming them down would reduce early ceiling reflections and aiming them in would reduce sidewall reflections isn't true of other speaker designs.
I'll be moving sometime in August and likely will have a very different room for my setup. This may change my tipped down approach, but I suspect not. I'm looking for a place with a basement I can finish, and in this case, the low ceiling may make this option even more important.
Doug, I was planning on going 12 inches wide, do you think that will be wide enough to remain very stable? Or do you think 14 inches would be better. As far as off axis listening, yes I can imagine that doesn't seem right with some people, I understand it and have heard it so I am fine with it. One question is, and this will pertain more when I get the speakers is, how far in front of the listening position are people crossing the speakers, if I place the speakers 3' out from the wall my listening position will be 14' from the speakers. Obviously 4' out 13', 54" is probably the max I can come out from the wall.
Using two intersecting 14" boards with cutouts the way I made them gives ~10" point-to-point spacing at the top and bottom and ~5.5" cross braces at the center. This fits the speakers well (they are ~11" deep not counting the roundover) and provides good stability and strength. I wouldn't feel comfortable going any narrower than that (and they need to be on a solid foundation to avoid any rocking - a wood floor in my case). I just picked up a couple of 7" boards at Home Depot and glued them together before making the cutouts (the wood was ~$70 or so, which is a lot less than it would have been to buy full width boards). I rough-cut the shapes with a jig saw and trimmed them flush using a router and 1/4" lexan template attached with screws along the center line - 1/2 of the screw holes get removed when the center cut is made (table saw) and the others are hidden when the pieces are glued together. Make sure the template is attached securely if you decide try this. PM me and I'll send you a powerpoint with the exact shapes I used.
I have my speakers set up ~13' apart and also ~13' from the main listening position, with 45 degree toe in and the woofer centers ~2' from the (front) wall. The response is approximately flat with 2 subs, optimized and EQ'd using a DCX.
While it will end up being that the speakers are pointed to cross so many feet infront of you, the more accurate and better way to do this is to consider the triangle the speaker to listener makes. Consider that the direct on-axis response is a laser beam pointing right at you (when the speakers are angled as such). Because these speakers are CD and the slightly off-axis response is the smoothest, you want that "beam" to be what points at you. So from that stand point, 10-15 degrees of toe-in more than pointing right at you would be enough.
However, per Dr. Geddes directivity paper, 22 degrees is what you want. Again, because these are true CD with a falling response as you get farther off-axis, you can maintain the L-R balance as you move around within the listening plane, making for a more stable stereo image and soundstage. It's something that is only possible with speakers like Dr. Geddes, i.e. true CD.
In order to do this correctly, I took measurements from the wall, and created a box, in which the inner-corner was the point where I wanted the front of the speakers to be. Then I measured from that the angle of the speaker necessary to create the axis from on-axis to listener to be 22 degrees. The box I created was with masking tape, and this helped me. I highly recommend using physical markers like this to make it easier.
If you have trouble conceptualizing what the angle would be on your floor, take a piece of graph paper and draw the triangles. http://www.gedlee.com/downloads/directivity.pdf Page 9 of this paper has the drawing you want to copy. Dr. Geddes can correct me if I have this wrong, but what I believe you want to do is look at the Left speaker to mark B and Right speaker to mark C. If you drew another line from the left speaker to listener at point A, then the angle made by the triangle of the left speaker and point A and B should be 22 degree's at it's vertex. Then look at the triangle made between the right speaker and point's A and C, this angle should also be 22 degrees. This then gives you the proper amount of toe in.
p.s. I'm about to watch Avatar on Bluray through my Abbey's. I was one of the ten people in the world who did not see this movie in the theater, so nobody ruin it for me. My dad actually liked it, and he normally hates these kind of films, so I figure it might be better than I expected it to be. Given the extreme graphics and sound, I expect them to give the Abbey's a run for Dr. Geddes.
However, per Dr. Geddes directivity paper, 22 degrees is what you want. Again, because these are true CD with a falling response as you get farther off-axis, you can maintain the L-R balance as you move around within the listening plane, making for a more stable stereo image and soundstage. It's something that is only possible with speakers like Dr. Geddes, i.e. true CD.
In order to do this correctly, I took measurements from the wall, and created a box, in which the inner-corner was the point where I wanted the front of the speakers to be. Then I measured from that the angle of the speaker necessary to create the axis from on-axis to listener to be 22 degrees. The box I created was with masking tape, and this helped me. I highly recommend using physical markers like this to make it easier.
If you have trouble conceptualizing what the angle would be on your floor, take a piece of graph paper and draw the triangles. http://www.gedlee.com/downloads/directivity.pdf Page 9 of this paper has the drawing you want to copy. Dr. Geddes can correct me if I have this wrong, but what I believe you want to do is look at the Left speaker to mark B and Right speaker to mark C. If you drew another line from the left speaker to listener at point A, then the angle made by the triangle of the left speaker and point A and B should be 22 degree's at it's vertex. Then look at the triangle made between the right speaker and point's A and C, this angle should also be 22 degrees. This then gives you the proper amount of toe in.
p.s. I'm about to watch Avatar on Bluray through my Abbey's. I was one of the ten people in the world who did not see this movie in the theater, so nobody ruin it for me. My dad actually liked it, and he normally hates these kind of films, so I figure it might be better than I expected it to be. Given the extreme graphics and sound, I expect them to give the Abbey's a run for Dr. Geddes.
Thanks a lot fellas for the info, it will be extremely useful. Doug I will PM you when I get started on the stands. I live a couple of miles from an excellent source for wood (Armstrong Millworks) so I'm sure I'll be like a kid in a candy store when I get to picking out the wood. And pjpoes thanks for the info I will read the paper and btw I am one of the 10 who didn't see Avatar in the theater also, I am going to buy it tomorrow on blu-ray and watch it.
Yes, wife and son like to go to IMAX and I have to admit that I can't compete with that. But honestly, I get a little dizzy at IMAX and I understand that this is not all that uncommon. I'm concerned about the 3D as well since these have given me headaches in the past and I've heard that even the new technologies, like used in Avatar, are not immune from that.
dwr,
Basic measuring equipment is very cheap. A Behringer ECM8000 mic and Xenyx 502 mixer are a good start. Get them and download REW for free and you have a simple system to help with multi sub setups. You can set up one sub in the listening position, then move the mic to all the positions you might use - that way you get a lot of measurements very quickly. If you want to do multiple positions, you can move the sub and go again. Depends on how many sub and seating positions you want to try. Also interesting to try different heights, especially in corners where you can make the sub at any height with a diy sub (especially bandpass).
Were you referring to a really long thread on multi subs? I went through one of those (can't remember on which forum) and distilled the useful and informative posts into one word document. If anyone wants the concise version, mostly with posts by Earl, and a few others I thought were useful, shoot me a PM.
About the vertical issue - looking at the polar response of the Abbey speaker and considering the waveguide is symmetrical, doesn't it make sense to listen a little off axis vertically as well? Then again, if toed in as recommended, perhaps it doesn't matter. The small variations caused by different heights probably don't mean that much change.
Basic measuring equipment is very cheap. A Behringer ECM8000 mic and Xenyx 502 mixer are a good start. Get them and download REW for free and you have a simple system to help with multi sub setups. You can set up one sub in the listening position, then move the mic to all the positions you might use - that way you get a lot of measurements very quickly. If you want to do multiple positions, you can move the sub and go again. Depends on how many sub and seating positions you want to try. Also interesting to try different heights, especially in corners where you can make the sub at any height with a diy sub (especially bandpass).
Were you referring to a really long thread on multi subs? I went through one of those (can't remember on which forum) and distilled the useful and informative posts into one word document. If anyone wants the concise version, mostly with posts by Earl, and a few others I thought were useful, shoot me a PM.
About the vertical issue - looking at the polar response of the Abbey speaker and considering the waveguide is symmetrical, doesn't it make sense to listen a little off axis vertically as well? Then again, if toed in as recommended, perhaps it doesn't matter. The small variations caused by different heights probably don't mean that much change.
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