Re-Packaged SDA 1Bs aka SDA-1B.BS
markamerica
Posts: 203
I'm early in this process, and it began with a.) a thought I had for re-utilization of a complete set of SDA-1B guts I have sitting on a shelf, and b.) due to a space limitation for the location in which I had intended to shoe-horn them. It was a sidebar discussion to a post about my intended SRS upgrades/mods, that you can find here if you're interested:
http://forum.polkaudio.com/discussion/164220/my-srs-refurb-project
The problem is that in the location in which one of the proposed speakers would go, there isn't sufficient room for a more traditional cabinet, and it would be impossible to do the original stacked arrangement of the drivers. (Two each stereo, two each tweeter, and two each dimensional.) In the thread linked above, I carried on a conversation trying to arrive at a solution that would preserve the SDA effect, although I was only actually concerned with one seat in the room. Call it the optimum listening location, or whatever you like. I guess I'll refer to it as the OLL from here on out.
Here's a flat drawing of the back of the room, for reference, with one of my earlier baffle layouts represented:
I played around with notions of staggering the drivers, front to rear, and essentially creating a stepped front baffle. I looked at a sloped baffle, and I looked at a number of slope and step combinations. None of these were satisfactory, and I have no desire to build something that just won't work very well. Ultimately, this left me flat, because while I could easily fit a pair of 2Bs into this envelope, but that didn't represent much of a challenge.
This prompted me to go back and do some more studying. In the original design of the 1Bs, and in fact, common to all of the SDA speakers, the stereo and dimensional mid-bass drivers are spaced laterally roughly the width of a human head, ear-to-ear. This addresses the SDA effect, and the notion of using the canceling signal from the dimensional drivers to defeat "aural crosstalk," as it had been termed by Polk. This was the innovation represented by the SDA series, and it is the reason they create such great imaging and breadth of sound-stage. Those aspects of these speakers are what has made them so popular, even thirty years or so after their introduction to the market.
In the case of the 2B, or the CRS+'s, it's a fairly simple matter to arrange: One tweeter, one stereo mid-bass driver, and one dimensional driver. Placing those within the constraints needed to match the SDA effect while fitting into the envelope I have to work with would be easy to accomplish, but it is 1Bs that I'm working with, and I wanted to do something different and unique. I wanted to create the biggest SDA bookshelf speakers ever. They would serve as part of my home theater, which at present exists in a room too small for all my gear, but will be used in the room I will eventually build around my gear provided I have my way about it. It will still be a decade or so before I have that room, and I'm not getting any younger. Hearing diminishes with age rapidly, so I want to hear all of this while I am still able to hear most of its range. I'm 49yo, for reference, and in my left ear, I can barely hear frequencies approaching 14khz, and in my right ear, it's less than this, something around 13khz. Therefore, in a decade or so, I will be lucky to hear anything much over 10khz in either ear. That's part of the reason I'm interested in doing this now, rather than waiting for the room I will be able to build to accommodate any danged thing I please.
If you'll indulge me, I'll now explain where this is headed. One of the biggest problems with my various arrangements on the sloped and stepped variants of my front baffle is that they suffered from my need to find a way to stack the mid-bass drivers without having the physical height available to stack them. Referencing the thread linked above, I tried all sorts of manipulations. The two things I was trying to accomplish were:
Place the drivers to create as near as possible to a progressive point/line source for the two tweeters, stereo drivers, and dimensional drivers respectively, while maintaining the correct spacing(relative to the spacing of my ears) at the OLL. I could manipulate the volume of the cabinets to a suitable extent by varying the depth of the cabinets.
The 12inch passive could be placed either on the front or rear baffle, to the extreme inside of the cabinets. The problem was the vertical stacking of the midbass drivers, particularly the dimensional drivers, since on the extreme outside edge of the space, I have only approximately 9-1/2 inches vertically with which to work. Obviously, there will be no stacking of two 6.5 inch drivers vertically there.
Part of my problem was that I was thinking in two dimensions. I wasn't thinking in three. I went back to study the problem. It's not just the line that matters, but also the distance to the drivers. Examining the SRSs, for example, while the tweeters are aligned vertically, from the OLL, they are not perfectly in alignment. Starting from top to bottom, from the OLL, the line they're in actually represents a toe-out beginning at the top of the tweeter array and moving slightly outward from the OLL. To correct this, you would actually need to move the tweeters slightly inward, depending upon how far apart the speakers are placed, and how close or distant you are to them. The farther away you are, the less this matters. The closer to center the speakers move, the less this matters.
Now, as in all loudspeaker design, there are always compromises of some sort. There is no ideal, and the only way to approach it with respect to the SDA effect is to consider only the OLL. That said, Polk's vertical alignment of tweeters, mid-bass stereo and dimensional drivers creates the best possible average outcome for an audience > one(1).
So let us start by admitting that a progressive point source is possible, and achievable, with arrays of stacked drivers, but that it can really only be "perfectly accomplished" with respect to one listening position in the room. The moment you move to a different listening position, the ideals are something different, and you've compromised.
After all, the idea of a progressive point source is to create the aural illusion that the sound of the tweeters, for instance, is coming from exactly one direction relative to the soundstage. The SDA effect relies on the proper spacing of the mid-bass drivers(ignoring earlier models with a dimensional tweeter for the sake of this discussion) in order to cancel out aural crosstalk. You can read DarqueKnight's very good SDA Compendium for more technical information, and it's well worth the read. It contains several good illustrations of the SDA effect's fundamental principles.
The more I thought about this, and the more I played with front baffle designs, all in an attempt to create one that would work for this project, preserving the SDA effect, preserving the progressive point source, and preserving time/distance-induced synchronization between all the drivers, I started to realize my problem was that thinking in 2D was my worst enemy. Sound from your loudspeakers is traveling to your ears in 4D, with the three spatial dimensions, plus one of time. Ordinary diagrams of the SDA effect, progressive point sources, and other factors are almost always drawn in two dimensions, and don't represent one dimension or another very well. Whether drawn from overhead, or drawn flat, looking at the speakers' faces, neither can actually represent what's happening in full detail.
Continued below:
http://forum.polkaudio.com/discussion/164220/my-srs-refurb-project
The problem is that in the location in which one of the proposed speakers would go, there isn't sufficient room for a more traditional cabinet, and it would be impossible to do the original stacked arrangement of the drivers. (Two each stereo, two each tweeter, and two each dimensional.) In the thread linked above, I carried on a conversation trying to arrive at a solution that would preserve the SDA effect, although I was only actually concerned with one seat in the room. Call it the optimum listening location, or whatever you like. I guess I'll refer to it as the OLL from here on out.
Here's a flat drawing of the back of the room, for reference, with one of my earlier baffle layouts represented:
I played around with notions of staggering the drivers, front to rear, and essentially creating a stepped front baffle. I looked at a sloped baffle, and I looked at a number of slope and step combinations. None of these were satisfactory, and I have no desire to build something that just won't work very well. Ultimately, this left me flat, because while I could easily fit a pair of 2Bs into this envelope, but that didn't represent much of a challenge.
This prompted me to go back and do some more studying. In the original design of the 1Bs, and in fact, common to all of the SDA speakers, the stereo and dimensional mid-bass drivers are spaced laterally roughly the width of a human head, ear-to-ear. This addresses the SDA effect, and the notion of using the canceling signal from the dimensional drivers to defeat "aural crosstalk," as it had been termed by Polk. This was the innovation represented by the SDA series, and it is the reason they create such great imaging and breadth of sound-stage. Those aspects of these speakers are what has made them so popular, even thirty years or so after their introduction to the market.
In the case of the 2B, or the CRS+'s, it's a fairly simple matter to arrange: One tweeter, one stereo mid-bass driver, and one dimensional driver. Placing those within the constraints needed to match the SDA effect while fitting into the envelope I have to work with would be easy to accomplish, but it is 1Bs that I'm working with, and I wanted to do something different and unique. I wanted to create the biggest SDA bookshelf speakers ever. They would serve as part of my home theater, which at present exists in a room too small for all my gear, but will be used in the room I will eventually build around my gear provided I have my way about it. It will still be a decade or so before I have that room, and I'm not getting any younger. Hearing diminishes with age rapidly, so I want to hear all of this while I am still able to hear most of its range. I'm 49yo, for reference, and in my left ear, I can barely hear frequencies approaching 14khz, and in my right ear, it's less than this, something around 13khz. Therefore, in a decade or so, I will be lucky to hear anything much over 10khz in either ear. That's part of the reason I'm interested in doing this now, rather than waiting for the room I will be able to build to accommodate any danged thing I please.
If you'll indulge me, I'll now explain where this is headed. One of the biggest problems with my various arrangements on the sloped and stepped variants of my front baffle is that they suffered from my need to find a way to stack the mid-bass drivers without having the physical height available to stack them. Referencing the thread linked above, I tried all sorts of manipulations. The two things I was trying to accomplish were:
Place the drivers to create as near as possible to a progressive point/line source for the two tweeters, stereo drivers, and dimensional drivers respectively, while maintaining the correct spacing(relative to the spacing of my ears) at the OLL. I could manipulate the volume of the cabinets to a suitable extent by varying the depth of the cabinets.
The 12inch passive could be placed either on the front or rear baffle, to the extreme inside of the cabinets. The problem was the vertical stacking of the midbass drivers, particularly the dimensional drivers, since on the extreme outside edge of the space, I have only approximately 9-1/2 inches vertically with which to work. Obviously, there will be no stacking of two 6.5 inch drivers vertically there.
Part of my problem was that I was thinking in two dimensions. I wasn't thinking in three. I went back to study the problem. It's not just the line that matters, but also the distance to the drivers. Examining the SRSs, for example, while the tweeters are aligned vertically, from the OLL, they are not perfectly in alignment. Starting from top to bottom, from the OLL, the line they're in actually represents a toe-out beginning at the top of the tweeter array and moving slightly outward from the OLL. To correct this, you would actually need to move the tweeters slightly inward, depending upon how far apart the speakers are placed, and how close or distant you are to them. The farther away you are, the less this matters. The closer to center the speakers move, the less this matters.
Now, as in all loudspeaker design, there are always compromises of some sort. There is no ideal, and the only way to approach it with respect to the SDA effect is to consider only the OLL. That said, Polk's vertical alignment of tweeters, mid-bass stereo and dimensional drivers creates the best possible average outcome for an audience > one(1).
So let us start by admitting that a progressive point source is possible, and achievable, with arrays of stacked drivers, but that it can really only be "perfectly accomplished" with respect to one listening position in the room. The moment you move to a different listening position, the ideals are something different, and you've compromised.
After all, the idea of a progressive point source is to create the aural illusion that the sound of the tweeters, for instance, is coming from exactly one direction relative to the soundstage. The SDA effect relies on the proper spacing of the mid-bass drivers(ignoring earlier models with a dimensional tweeter for the sake of this discussion) in order to cancel out aural crosstalk. You can read DarqueKnight's very good SDA Compendium for more technical information, and it's well worth the read. It contains several good illustrations of the SDA effect's fundamental principles.
The more I thought about this, and the more I played with front baffle designs, all in an attempt to create one that would work for this project, preserving the SDA effect, preserving the progressive point source, and preserving time/distance-induced synchronization between all the drivers, I started to realize my problem was that thinking in 2D was my worst enemy. Sound from your loudspeakers is traveling to your ears in 4D, with the three spatial dimensions, plus one of time. Ordinary diagrams of the SDA effect, progressive point sources, and other factors are almost always drawn in two dimensions, and don't represent one dimension or another very well. Whether drawn from overhead, or drawn flat, looking at the speakers' faces, neither can actually represent what's happening in full detail.
Continued below:
SDA SRS, SDA SRS1.2TL, SDA-1C,SDA 2B, Soundcraftsmen Amplification (A5002s, MA5002s, MA5002As)
Comments
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With that in mind, I decided to rethink my baffling problem in at least three dimensions. What this led me to was a new configuration for my front baffle that I believe has some chance of working as expected. Remember, I want to preserve the SDA effect, and have progressive point sources that won't confuse my hearing, and I want to use SDA-1B gut shoehorned into a small, sloping vertical space. I would like your impressions of this idea.
Here is an image representing this new front baffle:
What should be apparent right off is that I'm trying to represent a third dimension in this drawing. You will notice that the drivers all appear squashed. That's because I tilted the front baffle forward about 35 degrees. This gave me more vertical placement space on the face of the baffle. The red lines represent the direct to my left and right ears, and the middle between them in the case of the tweeters. This should eliminate the dispersion problem Westmassguy had pointed out early on in my meanderings on this subject, because I am no longer sloping the front baffle away, left to right, instead keeping that in a flat plane, but tilted downward.
My first concern is this: I know it's a bad thing to place a passive radiator in anything but a vertical plane because the moving mass will tend to damage the surround, and it will be dramatically unequal loading of the surround. I assume the same is true with mid-bass drivers, although the moving portion is of much lower mass, and so my question is: Tipped forward at ~35degrees, is this going to cause a problem for my mids?
In other respect, I manage to keep a progressive point source for the tweeters, at the OLL, and with respect to the mids, they are also in roughly parallel lines with respect to my ears. Remember, the bottom edge of this baffle will be sitting roughly 7-1/2 feet off the floor, so it's well overhead, and several feet to the rear. Not well-represented in this drawing is the fact that adding dept to it, you would see that at around 35 degrees, this would put the drivers almost in the same diagonal plane as my head while seated at the OLL. Probably 6-8 inches over my head, but pretty close.
So, have I theoretically proposed a design that should accomplish my stated goals? Again, remembering that I care only about the OLL, am I likely to preserve the SDA effect and maintain a progressive point source for the tweeters? Do you think it's a good enough idea to bother with? Will the angle (35 degrees from vertical)of the mid-bass drivers be a problem, mechanically? Obviously, the PR moves to the rear baffle in this iteration of my speculative design. Any drawbacks?
I actually modeled it briefly with a foam front baffle, extending strings in a line to a dummy head(appropriately representing my own) at the OLL. In three dimensions, it seems to work, at least prospectively.
Thoughts? Criticisms? I can take it. Am I fundamentally failing to grasp something here?
Thanks!
MarkSDA SRS, SDA SRS1.2TL, SDA-1C,SDA 2B, Soundcraftsmen Amplification (A5002s, MA5002s, MA5002As) -
I would be tempted to recap the low pass of the SDA1B crossovers to match SDA1C's crossover. It looks like you might be able to stack the two mw6511 stereo drivers on one side, position the tweeters stacked right next to them and run a single mw6511 for the dimensional array. Two mw6510's have the same ohm rating as one mw6511. The SDA2B's use a single MW6511 with the same crossover components as the SDA1C uses. This should allow the stereo drivers and tweeters to be stacked directly above each other and the single dimensional speaker could be placed between the centerline of the other drivers. Your drawing look like it would accommodate this arrangement. I think this would be closer to the line array SDA's use. Having the PR firing out the front next to each other should be fine, just don't angle them
I don't think I would angle the drivers either but I might consider angling the tweeters down some.
I have used SDA1C's in SDA2 speaker cabinets before with the speakers separated by about 8 feet with good results using a single dimensional driver like I suggested above."Make a man a fire and he'll be warm for a day. Light
a man on fire and he'll be warm for the rest of his life." -
SDA mods sure keep you working late on a Saturday nite/Sunday morning..
My New Year's resolution is 3840 × 2160
Family Room| Marantz AV7704| Usher Dancer Mini - 2 DMD Mains |Usher Dancer Mini-x DMD's Surrounds | Usher BE-616 DMD Center | SVS Ultra Rear Surrounds | Parasound Halo A21 | Parsound Halo A52+ | MIT Shotgun S3's | Dual SVS SB 4000 Ultras | Oppo UDP 203 | Directv Genie HD DVR | Samsung 75" Q8 QLED | PSAudio Stellar GCD | Mytek Brooklyn DAC+ | Lumin U1 Mini | HP Elite Slice PC | ROON'd for life |
ManCave: HT:Polk LSiM 706VR3 LSiM 703's LSiM 702's|| Marantz AV7002 AV PrePro Sunfire TGA-7401| Sony PS4 Pro| Sony PS4 Pro|SVS PB13 Ultra| Oppo UDP 203 | Music Hall MMF 5.3se TT w/ Soundsmith Carmen | Samsung 55" SUHD TV | Sony PS4
Patio | Polk Atrium 8's | Yamaha R-N303BL |
Office BlueSound Node| KEF LS50 | Peactree Nova 125SE |
Bedroom | Focal 905's | Chromecast Audio |
Garage | Polk Monitor 5B's
Closet Yamaha M80 | 2 Polk MP3K subs| Yaqin MC100B with Shuguang Treasures KT 88's & CV181Z's | Tesla E83CC's | Marantz 2252B | Marantz 2385 |Polk SDA SRS 2.3 | LSiM 705's | -
Unfortunately TNTsTunes, what I have is 8each MW6509s. The whole idea here was to re-use the SDA-1B guts I already have. If I don't angle the face, I couldn't stack the two stereo drivers anyway. Tilting the front baffle forward (toward the listener) at the top edge is the only way I get near enough vertical space. Can't afford to move the drivers inward (toward the centerline between the speakers)much further, or would destroy any SDA effect anyway. That German shrank on which they will rest is almost precisely 3 meters wide, or just about 10 feet.
Oh, and the idea for tilting the front baffle isn't mine, strictly speaking. Some years ago, I think it was perhaps DarqueKnight who posted a link to an external site on which a gentleman had shown his own literal home-theater, complete with tiered, theater style seating. As a center, he was using one CRS+, mounted below the screen, and angled upward facing basically into the same line as the heads of the audience that would be seated in the tiered seating. If I'm remembering right, he may have been using the other as a rear center, angled downward from the top back of the room, basically hitting his audience in the tiered seating in the back of the heads. So that's the source of the tilted front baffle I adapted into this particular lay-out.
MarkSDA SRS, SDA SRS1.2TL, SDA-1C,SDA 2B, Soundcraftsmen Amplification (A5002s, MA5002s, MA5002As) -
Hey, any time is a good time... LOL Besides, while I'm working on all of this, I'm enjoying my RDO-194s freshly installed on the SRSs and the center channel, and that gives me reason to smile.Mikey081057 wrote: »SDA mods sure keep you working late on a Saturday nite/Sunday morning..
Besides, the truth is that I'm always working on something. I'd go stir crazy otherwise. I have to keep my mind busy, always have.SDA SRS, SDA SRS1.2TL, SDA-1C,SDA 2B, Soundcraftsmen Amplification (A5002s, MA5002s, MA5002As) -
markamerica wrote: »
Hey, any time is a good time... LOL Besides, while I'm working on all of this, I'm enjoying my RDO-194s freshly installed on the SRSs and the center channel, and that gives me reason to smile.Mikey081057 wrote: »SDA mods sure keep you working late on a Saturday nite/Sunday morning..
Besides, the truth is that I'm always working on something. I'd go stir crazy otherwise. I have to keep my mind busy, always have.
Just finished putting my 2.3's back together... "idle hands are the devil's workshop"...
My New Year's resolution is 3840 × 2160
Family Room| Marantz AV7704| Usher Dancer Mini - 2 DMD Mains |Usher Dancer Mini-x DMD's Surrounds | Usher BE-616 DMD Center | SVS Ultra Rear Surrounds | Parasound Halo A21 | Parsound Halo A52+ | MIT Shotgun S3's | Dual SVS SB 4000 Ultras | Oppo UDP 203 | Directv Genie HD DVR | Samsung 75" Q8 QLED | PSAudio Stellar GCD | Mytek Brooklyn DAC+ | Lumin U1 Mini | HP Elite Slice PC | ROON'd for life |
ManCave: HT:Polk LSiM 706VR3 LSiM 703's LSiM 702's|| Marantz AV7002 AV PrePro Sunfire TGA-7401| Sony PS4 Pro| Sony PS4 Pro|SVS PB13 Ultra| Oppo UDP 203 | Music Hall MMF 5.3se TT w/ Soundsmith Carmen | Samsung 55" SUHD TV | Sony PS4
Patio | Polk Atrium 8's | Yamaha R-N303BL |
Office BlueSound Node| KEF LS50 | Peactree Nova 125SE |
Bedroom | Focal 905's | Chromecast Audio |
Garage | Polk Monitor 5B's
Closet Yamaha M80 | 2 Polk MP3K subs| Yaqin MC100B with Shuguang Treasures KT 88's & CV181Z's | Tesla E83CC's | Marantz 2252B | Marantz 2385 |Polk SDA SRS 2.3 | LSiM 705's | -
Mikey081057 wrote: »
Just finished putting my 2.3's back together... "idle hands are the devil's workshop"...
Amen. And idle minds are the devil's playhouse. I have been idle long enough now. I need to get back to work on a Soundcraftsmen MA5002A I picked up for peanuts, the only significant problem it has being its DC offset is way too high on one channel. A new front differential pair of transistors ought to fix that right on up.
There's nothing quite like some late night soldering to get the creative juices flowing...LOL Or something like that...
SDA SRS, SDA SRS1.2TL, SDA-1C,SDA 2B, Soundcraftsmen Amplification (A5002s, MA5002s, MA5002As) -
Random thought...
Just use the 4 MW6509's in a row wired in series/parallel using the stereo crossover, center the tweeters between the 4 drivers and recap the SDA crossover for a single SDA driver to add to the outside end."Make a man a fire and he'll be warm for a day. Light
a man on fire and he'll be warm for the rest of his life." -
TNTsTunes, No, that won't work. Wiring them in series parallel would half the resistance presented to the circuit, meaning I'd need to change both the inductance value of the stereo coil, and the capacitor's value. Chances are, I'd need to halve the one and double the other, more or less. And that would destroy the line array of the stereo drivers, with respect to my OLL. No, I don't think that's a plausible solution at all. Then of course, adding a fifth mid-bass driver would necessitate a change in cabinet volume, and so on.
Thanks!
Mark
SDA SRS, SDA SRS1.2TL, SDA-1C,SDA 2B, Soundcraftsmen Amplification (A5002s, MA5002s, MA5002As) -
I was just messing with ya. They are in parallel now I believe. Wiring two in series and the other two in series then connecting both sets in parallel should equal the same resistance."Make a man a fire and he'll be warm for a day. Light
a man on fire and he'll be warm for the rest of his life." -
My head hurts trying to follow all this. Suppose I should take an electronics course at some point so I can better understand some of this. "Science is suppose to explain observations not dismiss them as impossible" - Norm on AA; 2.3TL's w/sonicaps/mills/jantzen inductors, Gimpod's boards, Lg Solen SDA inductors, RD-0198's, MW's dynamatted, Armaflex speaker gaskets, H-nuts, brass spikes, Cardas CCGR BP's, upgraded IC Cable, Black Hole Damping Sheet strips, interior of cabinets sealed with Loctite Power Grab, AI-1 interface with 1000VA A-L transformer -
TNTsTunes, No actually, the stereo drivers are in series, as are the dimensionals.I was just messing with ya. They are in parallel now I believe. Wiring two in series and the other two in series then connecting both sets in parallel should equal the same resistance.
Don't worry Drumminman, this thread may not be worth following...LOLdrumminman wrote: » My head hurts trying to follow all this. Suppose I should take an electronics course at some point so I can better understand some of this.
SDA SRS, SDA SRS1.2TL, SDA-1C,SDA 2B, Soundcraftsmen Amplification (A5002s, MA5002s, MA5002As) -
markamerica wrote: »
TNTsTunes, No actually, the stereo drivers are in series, as are the dimensionals.I was just messing with ya. They are in parallel now I believe. Wiring two in series and the other two in series then connecting both sets in parallel should equal the same resistance.
I was going by the schematics that show them in parallel.
cdn.vanillaforums.com/polkaudio.vanillaforums.com/attachments/1/8/5/1/1/31011.pdf
Series seems wrong to me... The ohm rating of the speakers would be too high that way.
I could be wrong though.
"Make a man a fire and he'll be warm for a day. Light
a man on fire and he'll be warm for the rest of his life." -
TNTsTunes, I stand corrected. You're quite right. They're in parallel. Placing two parallel pairs in series would double the resistance. I don't know what I was remembering.
SDA SRS, SDA SRS1.2TL, SDA-1C,SDA 2B, Soundcraftsmen Amplification (A5002s, MA5002s, MA5002As) -
That's ok since I'm wrong too...
Your resistance would still double.
I blame not having enough sleep.
I was thinkin about how I swapped my 2 MW6511 stereo drivers in my 2.3's to 4 MW6503's. The MW6511 have half of the resistance the MW6503's have. Basically I duplicated the 1.2 crossover/driver low pass arrangement. I ran the mid bass circuit to the dimensional circuit also.
They have never sounded better.
"Make a man a fire and he'll be warm for a day. Light
a man on fire and he'll be warm for the rest of his life." -
I don't have an issue with either an above or below the screen speaker custom made using SDA sourced drivers. My question is what signal are you going to send to the new "center"? Will it be center channel only or are you trying to get some type of SDA signal present in that speaker from L and R.
If you are trying to preserve SDA signals in two sets of SDAs running the same signals in different positions, you may experience strange anomalies, especially if you don't maintain dimensional spacings.
HT Optoma HD25 LV on 80" DIY Screen, Anthem MRX 300 Receiver, Pioneer Elite BDP 51FD Polk CS350LS, Polk SDA1C, Polk FX300, Polk RT55, Dual EBS Adire Shiva 320watt tuned to 17hz, ICs-DIY Twisted Prs, Speaker-Raymond Cable
2 Channel Thorens TD 318 Grado ZF1, SACD/CD Marantz 8260, Soundstream/Krell DAC1, Audio Mirror PP1, Odyssey Stratos, ADS L-1290, ICs-DIY Twisted , Speaker-Raymond Cable -
Dennis,
Good question. What is going to my custom center is center-channel signal only. The front pair of speakers are the SRSs, I have the 1.2TLs in back, and 1Cs as the surrounds. This pair(the proposed SDA1B.BSs) would go high rear.
I see absolutely no need for additional subwoofers, as the SRSs do just fine in that part of the range.
MarkSDA SRS, SDA SRS1.2TL, SDA-1C,SDA 2B, Soundcraftsmen Amplification (A5002s, MA5002s, MA5002As) -
If the new center channel speaker is getting only the center channel from the AV processor, how can you have an SDA effect since there is no L-R signal?"Science is suppose to explain observations not dismiss them as impossible" - Norm on AA; 2.3TL's w/sonicaps/mills/jantzen inductors, Gimpod's boards, Lg Solen SDA inductors, RD-0198's, MW's dynamatted, Armaflex speaker gaskets, H-nuts, brass spikes, Cardas CCGR BP's, upgraded IC Cable, Black Hole Damping Sheet strips, interior of cabinets sealed with Loctite Power Grab, AI-1 interface with 1000VA A-L transformer
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Sorry Drumminman, maybe I'm doing a bad job of 'splainin'. Center channel is strictly center channel. The main front speakers are the SRSs. The SDA effect is still very much present and in play via those mains, left and right.SDA SRS, SDA SRS1.2TL, SDA-1C,SDA 2B, Soundcraftsmen Amplification (A5002s, MA5002s, MA5002As)
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No disrespect intended Mark, but I see absolutely no reason for dual rear centers when you are already using the largest speakers that I have ever heard of anyone using for rears, 1.2TLs. Seems like you have some ADHD creeping into your late night thinking and you simply feel the need to fill every nook and cranny with speakers because you own them. I like the idea of SDA theater, but improvements in some other area have got to rank higher on the needed list than dual rear centers next to 1.2TLs. You have yet to post what are you running for your front center that I can see?
I would steer my thoughts into what Dolby Atmos will mean once that takes off over the rear center ideas. dolby.com/us/en/technologies/dolby-atmos.htmlHT Optoma HD25 LV on 80" DIY Screen, Anthem MRX 300 Receiver, Pioneer Elite BDP 51FD Polk CS350LS, Polk SDA1C, Polk FX300, Polk RT55, Dual EBS Adire Shiva 320watt tuned to 17hz, ICs-DIY Twisted Prs, Speaker-Raymond Cable
2 Channel Thorens TD 318 Grado ZF1, SACD/CD Marantz 8260, Soundstream/Krell DAC1, Audio Mirror PP1, Odyssey Stratos, ADS L-1290, ICs-DIY Twisted , Speaker-Raymond Cable -
Dennis Gardner wrote: »No disrespect intended Mark, but I see absolutely no reason for dual rear centers when you are already using the largest speakers that I have ever heard of anyone using for rears, 1.2TLs. Seems like you have some ADHD creeping into your late night thinking and you simply feel the need to fill every nook and cranny with speakers because you own them. I like the idea of SDA theater, but improvements in some other area have got to rank higher on the needed list than dual rear centers next to 1.2TLs. You have yet to post what are you running for your front center that I can see?
See the top of the second page of this thread to see what I have for a center.
There've been a few mods since the pics there. The MWs are 6510s, and the SL2000s have been replaced by RDO 194s.
http://forum.polkaudio.com/discussion/153945/planning-a-project-with-sda-crs-guts/p2
Mark
SDA SRS, SDA SRS1.2TL, SDA-1C,SDA 2B, Soundcraftsmen Amplification (A5002s, MA5002s, MA5002As) -
I recall that custom center........I didn't realize that that was your project. Great job on it!!
I still think using the same center channel signal may cause issues, but no more than SDA1Cs being run on opposing sides I guess.
Good luck with it!
HT Optoma HD25 LV on 80" DIY Screen, Anthem MRX 300 Receiver, Pioneer Elite BDP 51FD Polk CS350LS, Polk SDA1C, Polk FX300, Polk RT55, Dual EBS Adire Shiva 320watt tuned to 17hz, ICs-DIY Twisted Prs, Speaker-Raymond Cable
2 Channel Thorens TD 318 Grado ZF1, SACD/CD Marantz 8260, Soundstream/Krell DAC1, Audio Mirror PP1, Odyssey Stratos, ADS L-1290, ICs-DIY Twisted , Speaker-Raymond Cable -
Dennis,
Thanks for the compliment on the center. One of these days, I'll put some skin on it, but I'm being fairly indecisive about what sort of cosmetic treatment to apply to my various SDAs. (What wood finish, what grill cloth, etc...)
I also think I've managed to botch fairly well in my communications here what it is I'm trying to accomplish. The speakers I'm proposing here are not center channel. The SDA-1B.Bs would be effectively a rear high surround, left and right. Also, I don't have the 1Cs crossfiring across the room at one another. Strictly speaking, I'm using left and right surround channel signal, but I have them slightly forward of my OLL(optimum listening location) but otherwise oriented like normal SDAs. Think of it like having a pair of SDA-1Cs as your front channel speakers, spread out 18 feet or so, and sitting four or five feet from the front wall between them. The largest problem there is that the high frequencies suffer at the OLL because of the dispersion issue Westmassguy and I discussed elsewhere. The other problem is that relative to the OLL, the spacing between the stereo and dimensional drivers is narrowed substantially due to the angles. I have contemplated placing something like RTA 11s in their place. I've also contemplated something somewhat more radical, but that's me. Everybody here probably thinks I'm two steps from dead-crazy anyway, so what the hay? I had considered briefly repackaging the 1Bs for use as left and right surrounds, by making "end table speakers" out of them, broadening their front baffles to allow a greater spacing of the stereo and dimensional drivers, and basically canting the tweeters toward the OLL for the sake of combating the dispersion issue.
I realize that many of these seemingly half-baked ideas are probably that, and nothing more, which is why I try to vet some of these ideas here first. I also recognize that for SDA purists, my tinkering around with baffle layouts and so on is not necessarily going to make me any friends. I get it. I guess if I could say anything, it would be that my intention is to try and create a system that provides me the various elements I'm looking for, which is best described as an enveloping listening experience that provides a virtual sound-stage that is broad and detailed from the OLL, and is three dimensional. I want that sound-stage to seem as though it's right out in front of me, but also coming at me from behind, overhead, and the sides, as well as from the front and front center. I'm probably putting way too much thought into this for far too little yield, but that's the part of it I enjoy almost as much as the end product, if ever I obtain it. I like to experiment with different things, try new ideas, but still abide by the general constraints of my goal, the equipment I have to work with, and the inherent constraints of said gear.
The real question of this thread is whether the proposed SDA-1B.BSs are worth pursuing, which gets back to those fundamental questions: With the baffle layout I've specified, will the SDA effect be preserved? Will the arrays of stereo, and dimensional drivers along with the tweeters still sound like a pint or line source from the aspect of the OLL? Will the angle of the baffle(35degrees), while eliminating the dispersion issue with the tweeters, also represent a problem in performance or long-run health of the mid-bass drivers? Ultimately, having answered these, are these proposed speakers worth the experiment? These are really the questions I was trying to answer in this thread, and I fear my poor communications have muddled them.
Perhaps it would be better if I provided a layout of the room that offered a better picture of the situation. Naturally, as I've said elsewhere, the current room isn't ideal either, but I have long-run goals to remedy that problem.(New room!) In the mean time, I want to have my gear figured out, so that I can design the room around what I'm trying to accomplish, so that when the room finally materializes, I will be able to occupy that space with the aforementioned gear and fully enjoy it until my dying day.
Again, thanks for the kind words on the center project. If you have any suggestions on finishes, etc, don't be afraid to share them. I am so thoroughly conflicted about what to do in that regard that it may be some time before I settle upon a solution I think I can live with in the longer run.
Thanks!
Mark
SDA SRS, SDA SRS1.2TL, SDA-1C,SDA 2B, Soundcraftsmen Amplification (A5002s, MA5002s, MA5002As) -
I think I get your setup now, Mark. In this type of setup using SDA speakers all around, I would use inverted/swapped L/R CRS+ models hanging overhead from the ceiling to be less obtrusive angled to your seating in the forward surround placement and another set inverted on the back wall would work in the center rear too. Inverting them would help with tweeter's reflection from the ceiling and get the Main/Dim. drivers in the proper places.
This would yield less bass response, but I personally don't put sub 20hz explosions through my SDAs anyway as I use a custom built Dual Adire Shiva EBS tuned to 17hz for HT use.
I like your approach so far......keep us posted.HT Optoma HD25 LV on 80" DIY Screen, Anthem MRX 300 Receiver, Pioneer Elite BDP 51FD Polk CS350LS, Polk SDA1C, Polk FX300, Polk RT55, Dual EBS Adire Shiva 320watt tuned to 17hz, ICs-DIY Twisted Prs, Speaker-Raymond Cable
2 Channel Thorens TD 318 Grado ZF1, SACD/CD Marantz 8260, Soundstream/Krell DAC1, Audio Mirror PP1, Odyssey Stratos, ADS L-1290, ICs-DIY Twisted , Speaker-Raymond Cable -
Dennis,
Before I go any further, let me show you where I am at now.
So right now, of course, the SDA-1B.BS are a drawing board item, and I placed them here merely to show you where they'd go.
At present, the 1Cs get toed in slightly(over-represented in the drawing, it's really only about 20 degrees). It's contrary to SDA norms, but that's because they're so wide apart and so close to the OLL, front to rear. Turned straight toward the back of the room, I wouldn't hear the tweeters at all(Westmassguy pointed out the dispersion factor) and the spacing between the mids would be much too narrow(relative to the OLL). So the toe-in is my way to compensate for this.
I had also thought about just going with some RTA 15TLs as surrounds, replacing the 1Cs in this role. That's more problematic, however, because not represented in this drawing is just rearward from the right side 1C(heading downward on the drawing) is a break in the wall that runs about 8 feet. (Causes a little problem for the 1.2TL on that side because I don't get matching reflection off the absent wall on that side.) These are issues specific to the room, and as I said, this won't always be the room, which is far from ideal.
Anyway, that's what I'm playing with. To use 15TLs as the surrounds, I'd need to repackage them. Probably something taller, a little more than half as deep, moving the second passive to the front baffle, keeping the same width up front, but making the back baffle wider, keeping the same internal volume. That would permit me to place them against the side walls, on the right side, basically where the wall ends before the break.
SDA SRS, SDA SRS1.2TL, SDA-1C,SDA 2B, Soundcraftsmen Amplification (A5002s, MA5002s, MA5002As) -
I know this is kinda an old thread already but I did find it interesting in so many ways. We've had many a person here throw out trying to redesign SDAs to no avail or just forgot about the project. I do like Dennis G. idea of just hanging CRS ala dare I say Bose 901s instead of trying to make something. You already have a very impressive collection of Polk originals. You yourself admitted to hearing loss and god forbid it does deminish,then what all that work you put into this project that may or may not work I don't see it. Good luck to you. I have 1 set of 2Bs and it's plenty for me besides my other minor collection.2-chl-Adcom555-NAD 1020a pre--JVC QL-200TT--Grado FT+cart--Denon1941cdp--Samson surge pro--Yamaha RX-V665avr-ysd dock-i-pod---Toshiba au40'' flat
'87Polk Audio SDA 2b(modded)--DCM TF 350s-- ADC-303AX--AAL2way--JBL-2060
Nikko 6065 receiver--Sony ns300cpd---JBL g-200 bookies -
I reconsidered the hanging issue. At 1st blush early in the morning it sounded good. If you have a sheet rock 1st floor ceiling it's almost impossible to hide the wires especially the interconnects if hung. Generally floor joyeces run front to back for 3 main reasons, strength, anti sag, and cost and meet at a central micro lam. If it's a basement w/ a drop ceiling then it would an easy job.I seriously doubt you would want exposed wires all over after either attempting what want to do or formulate some other combo of speakers.If using floor standers you could either remove baseboard mouldings or snake along carpet tackless if it's a carpeted room, I've done both w/ good results.2-chl-Adcom555-NAD 1020a pre--JVC QL-200TT--Grado FT+cart--Denon1941cdp--Samson surge pro--Yamaha RX-V665avr-ysd dock-i-pod---Toshiba au40'' flat
'87Polk Audio SDA 2b(modded)--DCM TF 350s-- ADC-303AX--AAL2way--JBL-2060
Nikko 6065 receiver--Sony ns300cpd---JBL g-200 bookies
