My SRS Refurb project

markamerica

I am getting ready to begin my own SRS refurbishment project. I intend to address as many facets of these speakers as I can afford. I'm not going to spare too many expenses, although there are a few areas where I will cut here and there. What I need from other members(particularly experienced upgraders/modders) is to review my list for things I'm missing, and also to straighten me out anywhere I've departed from prudence or sanity.

Let's start with a list of things I'm going to do.
Larry's Rings - recently arrived - inspected them - marvelous work, really!
Replace all SL2000s with RDO-194s. They went on order today, along with the RDO-198s for my TLs and four more RDO-194s for my 1Cs(studio). (So yes, we ordered 20 tweeters today...LOL) I will eventually order another few pairs for the 2Bs, the Custom Center(which is sounding remarkably good as things settle out and burn-in electrically)
I've already replaced any marginal or faulty MW6503s

I will be dynamatting the MWs along with the PR, but I'm considering an alternate product, called Black FatMat. A fellow I know locally swears its better than Dynamat, but I'm wondering if you have used it or have any experience to guide me on it. Here's the product page on Amazon for reference:
http://www.amazon.com/FatMat-Self-Adhesive-MegaMat-Deadener-Install/dp/B00G8IBEKI/ref=sr_1_4?ie=UTF8&qid=1412390459&sr=8-4&keywords=fatmat+butyl
I intend to us the BlackHole5 product I've seen discussed here, in much the same fashion as described in DarqueKnight's 1.2TL upgrades/mods post.
I will be basically building new crossovers, entirely, and from scratch. I will do my best to meet specs as closely as possible throughout.

So far, I've managed to acquire Clarity ESA 630v series caps in values of 12uf, 4.4uf, and 20uf. I thought briefly about the MR series, but no, I'm not made of money. Maybe a "someday" upgrade.

For the large value capacitors, the 92uf in the HF circuit, and the pair of 130s in each speaker's LF Dimensional circuit, I will be using 400v Erse caps in values of 91uf and 130uf respectively, though I may be in for something of a wait, since the 130s had to be back-ordered.

All the inductors will be Jantzen Aircores (already acquired from VR3) although I may make provision for later installation of the large Solen 10AWG 16.0mH inductors DK used in his. Based on the approximate cost, and since I have the Jantzens on hand right now, I will defer the Solens until funding better permits.

All of the resistors will be PathAudio units. I will be using the 0.5ohm resistors in place of polyswitches, although I hope not to later regret this if my daughter house-sits again. Just as she believes the gas pedal in her car has only two possible positions, she seems to think the same of volume knobs.

I will be re-wiring with 10AWG OFC copper, and using the Molex Minifit Srs just like on the custom Center channel.

I will be doing something with the terminal cups. Whether I wind up machining my own, or perhaps buying some of VR3's nifty units, I'm not yet certain, but I'm also thinking about the SDA cable and whether Neutrik Speak-ons are the way to go.. They seem quite popular among modders here. Thoughts?

I will be using PowerBond on all of the seems and joints internally in the cabinets.
I will be replacing all of the cloth, including the side panels. I am torn(no pun intended) on this feature on several fronts. I would like to use a more transparent cloth than the stock, but durability may be an issue. Yes, we have one of those four-legged grill-cloth shredders, and my wife has assured me that my speakers will go before the cat does. Thing is, he was de-clawed before we adopted him, so he doesn't shred the cloth, but he still tries and merely abrades the cloth on his favorite corner. The cloth winds up looking like well-worn socks, if you get my meaning. Little fuzzballs of worn grill cloth all over that corner. It may be a no win situation until nature takes me or the cat out of the picture for good.

I am going back and forth on the wood. Part of the trouble is indecision because this will be the hardest to change later. I've considered several, and at one point a few years ago, was looking at some curly tiger-striped maple much like DK used, but the problem is that I need to match my Center, which is still naked, and still waiting, while I try to decide this part. Ultimately, whatever I choose will get repeated on the TLs and the Center.

One of the things I considered was an composite ebony veneer, but with all the dark grill cloth in the room, and all the black amps and so on, I worry that it ill be too dark. Then I thought: I'd seen some silvery looking grill cloth from Australia that would offset the ebony, but I don't know how acoustically transparent it really is.

As you can readily see, I'm still torn over this. After looking at the beige grill cloth on a pair somebody post in the last day or two, I know I don't want that. I am open to suggestions.

So here at the end of a lengthy list of proposed mods/upgrades, what say the assembled experts? Feel free to be as harsh as you like. Most of the crossover components are etched in stone, at least for now, but you may have better ideas. In any event, let me know what you think.

One last thing. I am still debating whether to do point-to-point or custom boards like I did for the Center channel. Suggestions?

Thanks!

Mark

teekay0007

markamerica wrote: »

I am getting ready to begin my own SRS refurbishment project. I intend to address as many facets of these speakers as I can afford.

Wow, Mark, that looks like one heckuva project you're undertaking there! Doesn't look like you're leaving any stone unturned.

I'll keep watching to see how this turns out. Please keep posting progress updates with pics - we need some new documentation threads around here since all the old ones are now hard to find with the new forum format.

Very exciting!!

teekay0007

markamerica wrote: »

I am going back and forth on the wood.

Yes, as I said above, "Very exciting!"

F1nut

FatMat or Dynamat Extreme will make no difference, so use either.

PathAudio resistors have my interest, but I haven't heard them yet. I read some think they are better than Duelund. Personally, I like the warmth and ultimate musicality of Mills. That said, the newer Mexican Mills are not as good as the originals. Only SonicCraft has the originals, so get'em while you can.

The thing with exotic woods, they tend to not blend well with normal furniture woods. I definitely would not go with the ebony, too dark. Mahogany, walnut and cherry are always good choices, IMO.

Neutrik, accept no substitute.

Grill cloth....I don't notice a difference with the grills on or off, so non-factor sound wise to me, but I also don't want to see the drivers through the more transparent cloth.

Trick to keep kitty away from your speakers. I accidentally hit my cat on the nose with a miniature soccer ball (golf ball size) once. She really didn't like that and wouldn't go anywhere near the damn thing, so I bought another and put them on the outside corners of the SDA's. She never went near the speakers after that.

Point-to-point or custom boards.....as long as the custom boards have heavy traces I don't think there's an advantage to P2P. Of course, custom will cost more. If using FR4 for the P2P, make sure you wear a really good mask when drilling, that fiberglass dust is nasty.

Don't forget spikes, good ones.

headrott

F1nut wrote: »

Grill cloth....I don't notice a difference with the grills on or off, so non-factor sound wise to me, but I also don't want to see the drivers through the more transparent cloth.

I think it does make a slight difference (with the original Polk cloth) if you have the grills on regarding the high end, opposed to having the grills off. To me, it makes the highs slightly more "in-your-face" with the grills of. I have not listened with them off (compared the two states, on/off) in a loooooong time, however. I am just going by memory (of about 3 years ago).

westmassguy

Mark, I vote for the custom crossover boards. The boards you did for the center were gorgeous. Anything is an improvement over the original 2nd and 3rd generation SRS boards. You could even market them.
Solen also makes a 130uf Fastcap, and since it's part of the "Sub-Bass Drive Circuit", I seriously doubt you'll hear a difference.
I use very sheer architectural grill cloth. Unlike Jesse, I like to see a hint of the drivers when the light hits them just right. Don't know how the sheer cloths will hold up with four legged creatures though

drumminman

Great and comprehensive list, Mark. Re: Fat Mat, that's what I use and I can't tell a difference between that and DynamatvExtreme. I use mainly Fat Mat Rattle Trap, which is a little thicker than the regular or Dynamat Extreme. It's also a bit cheaper.

Looking forward to pics as you go. Like a poster above said, we need some new DIY threads!

markamerica

teekay0007 wrote: »

markamerica wrote: »

I am going back and forth on the wood.

Yes, as I said above, "Very exciting!"

There's always got to be one in every crowd.

F1nut wrote: »

FatMat or Dynamat Extreme will make no difference, so use either.

PathAudio resistors have my interest, but I haven't heard them yet. I read some think they are better than Duelund. Personally, I like the warmth and ultimate musicality of Mills. That said, the newer Mexican Mills are not as good as the originals. Only SonicCraft has the originals, so get'em while you can.

The thing with exotic woods, they tend to not blend well with normal furniture woods. I definitely would not go with the ebony, too dark. Mahogany, walnut and cherry are always good choices, IMO.

Neutrik, accept no substitute.

Grill cloth....I don't notice a difference with the grills on or off, so non-factor sound wise to me, but I also don't want to see the drivers through the more transparent cloth.

Trick to keep kitty away from your speakers. I accidentally hit my cat on the nose with a miniature soccer ball (golf ball size) once. She really didn't like that and wouldn't go anywhere near the damn thing, so I bought another and put them on the outside corners of the SDA's. She never went near the speakers after that.

Point-to-point or custom boards.....as long as the custom boards have heavy traces I don't think there's an advantage to P2P. Of course, custom will cost more. If using FR4 for the P2P, make sure you wear a really good mask when drilling, that fiberglass dust is nasty.

Don't forget spikes, good ones.

Jesse, I've heard/read reviews of the PathAudios that swear they're better than the higher-dollar Duelands. I think that makes them worth the gamble. They're on the way, so we'll see.(Or hear) The one thing I went back and forth on was values. Let me explain: The Dueland Standards are 10%, the Dueland Cast are 5%, but the PathAudios are 1%. There was one exact value not available in the PathAudio series. The two 22.5ohm resistors(22r5). PathAudio only has 22.0ohm (22r0). Dueland makes them in both lines at 22r5. So I built a small table. At 1%, though the PathAudios don't ever have exactly the nominal value, at maximum deviation from nominal, they can get very close, 22r25 but they will never get as far from nominal as the maximum deviation of the 5% Duelands. So I played the probabilities here.

Here's the approximate ebony I had considered:
http://www.ebay.com/itm/Black-Gray-Platinum-Ebony-composite-wood-veneer-49-x-113-with-wood-backing-/121319586626?pt=LH_DefaultDomain_0&hash=item1c3f35fb42
I had thought that with some of that silver grill cloth(which I'm having trouble locating at the moment) might look okay, might even brighten up the room, but then I decided not.

I keep a spray bottle full of water that I spritz the cat with every time he gets near them. He stays away most of the time when I'm around, but the problem is when I'm not.

Spikes are on the list, though I failed to mention them, and so is armacell for the drivers(already used on the custom center, and I have five big rolls - so thanks again to the private messenger who reminded me of this.)

westmassguy wrote: »

Mark, I vote for the custom crossover boards. The boards you did for the center were gorgeous. Anything is an improvement over the original 2nd and 3rd generation SRS boards. You could even market them.
Solen also makes a 130uf Fastcap, and since it's part of the "Sub-Bass Drive Circuit", I seriously doubt you'll hear a difference.
I use very sheer architectural grill cloth. Unlike Jesse, I like to see a hint of the drivers when the light hits them just right. Don't know how the sheer cloths will hold up with four legged creatures though

Westmassguy, Thank you for the kind words on the board. To address your comment and F1Nut's about the custom boards, on that center channel board, the minimum order from the outfit I deal with is two(2) I only needed the one board, so what I did was to stack them. I purposefully designed them to place components to do all the trace hopping, so that the front side of the board could be identical to the read of the board. This meant that double-stacking them would give me 4 6.35mm(1/4") traces for every circuit instead of one, and all it took was me being patient enough to sweat enough solder at each solder joint to penetrate and electrically connect the boards. I don't know, only suspect, but I'm guessing four fat traces combined as one in this fashion makes for plenty of bandwidth so to speak.

I am in the process of designing similar boards for the SRS project. Component placement with all those big caps is proving to be hell. Think about VR3's "Monastery" level crossovers for the 1.2TLs, and you get the picture. (Minus the MRs, which are just out of my league.)

As a side note, I was experimenting with my center, and I made a few mods and now it sounds so good, I really can't imagine why I didn't begin that project a decade ago. Wish you could hear it... I'd love the impressions from a better-trained ear. It sounds so good that if I just turn on the amp that drives it, turning off the others, by itself, it is a remarkable thing, and while I'm just a novice hack compared to most of you guys here, I must admit that I am quite satisfied, in fact thrilled, with its performance. I'll be upgrading its tweeters to RDO-194s in short order.

One of the suggestions I received via PM was to use Magnepan grill cloth. Thoughts?

drumminman wrote: »

Great and comprehensive list, Mark. Re: Fat Mat, that's what I use and I can't tell a difference between that and DynamatvExtreme. I use mainly Fat Mat Rattle Trap, which is a little thicker than the regular or Dynamat Extreme. It's also a bit cheaper.

Looking forward to pics as you go. Like a poster above said, we need some new DIY threads!

I think I'm going with the Fatmat, based on comments here. As far as pictures, what I'm going to do, I think, is to have a major surgery weekend. I'll build the x-overs ahead of time, I've made a template for the dynamat/fatmat for the MWs, and I will do my best to document this.

It should be a good deal of fun, even if it's a lot of work and expense. I still have to order a few things, and that will take time since my wallet is not a bottomless pit, but this is the direction for me, and after hearing the results on my center, I am quite enthusiastic to get this under way.

Thanks to all!

Mark

markamerica

markamerica wrote: »

Jesse, I've heard/read reviews of the PathAudios that swear they're better than the higher-dollar Duelands. I think that makes them worth the gamble. They're on the way, so we'll see.(Or hear) The one thing I went back and forth on was values. Let me explain: The Dueland Standards are 10%, the Dueland Cast are 5%, but the PathAudios are 1%. There was one exact value not available in the PathAudio series. The two 22.5ohm resistors(22r5). PathAudio only has 22.0ohm (22r0). Dueland makes them in both lines at 22r5. So I built a small table. At 1%, though the PathAudios don't ever have exactly the nominal value, at maximum deviation from nominal, they can get very close, 22r25 but they will never get as far from nominal as the maximum deviation of the 5% Duelands. So I played the probabilities here.

To better illuminate that to which I was referencing here, here is the table:


As you can see, while the PathAudio 22r0 resistors will never have the exact nominal value of 22r5, I did the following math: The Dueland Cast resistors cost approximately 85% more, and the Dueland Standards cost a few dollars less (~20%). As you can see from the table, the PathAudio resistors will never deviate as much from their nominal value as either of the Duelands, so I decided for practical reasons to go with the Pathaudios, plus, to be honest, I wanted to hear if they're as good as reported, and I am always intrigued by new gadgets and so on, and having that copper jacket for shielding connected to ground was just too big a temptation for the tinkerer in me. Also, the PathAudios should take up much less real estate.

Anyway, that's the process that went into selecting the PathAudios, along with various reviews I've read. We'll see.

BKphoto

P I C S ...!



or we don't believe you...

F1nut

Mark, you could also use a 15 and 7.5 in series to make up the 22.5.

vmaxer

markamerica wrote: »

markamerica wrote: »

Jesse, I've heard/read reviews of the PathAudios that swear they're better than the higher-dollar Duelands. I think that makes them worth the gamble. They're on the way, so we'll see.(Or hear) The one thing I went back and forth on was values. Let me explain: The Dueland Standards are 10%, the Dueland Cast are 5%, but the PathAudios are 1%. There was one exact value not available in the PathAudio series. The two 22.5ohm resistors(22r5). PathAudio only has 22.0ohm (22r0). Dueland makes them in both lines at 22r5. So I built a small table. At 1%, though the PathAudios don't ever have exactly the nominal value, at maximum deviation from nominal, they can get very close, 22r25 but they will never get as far from nominal as the maximum deviation of the 5% Duelands. So I played the probabilities here.

To better illuminate that to which I was referencing here, here is the table:


As you can see, while the PathAudio 22r0 resistors will never have the exact nominal value of 22r5, I did the following math: The Dueland Cast resistors cost approximately 85% more, and the Dueland Standards cost a few dollars less (~20%). As you can see from the table, the PathAudio resistors will never deviate as much from their nominal value as either of the Duelands, so I decided for practical reasons to go with the Pathaudios, plus, to be honest, I wanted to hear if they're as good as reported, and I am always intrigued by new gadgets and so on, and having that copper jacket for shielding connected to ground was just too big a temptation for the tinkerer in me. Also, the PathAudios should take up much less real estate.

Anyway, that's the process that went into selecting the PathAudios, along with various reviews I've read. We'll see.

I am looking forward to your thoughts on how they sound when completed. I hope they are awesome.

markamerica

F1nut wrote: »

Mark, you could also use a 15 and 7.5 in series to make up the 22.5.

I thought about that, and PartsConnexion carries them in 0r5, so I could have placed that size in series and gotten the same thing. That said, I think I will make provision on my boards for that if I wind up thinking it's necessary. I thought about it real hard since I'm already buying two at that value to replace the polyswitches, but this would add two resistors to each crossover and about $140 of cost. Of course, at this point, one might ask: "Geeze Mark, you're already dropping more coin than is rational...why not the extra bucks?" See, if I take that approach, I wind up with the Clarity MRs the extra 0r5 resistors, a cat ejection seat, and a big fat divorce...

Hey, there may be some merit to this...

Anyway, the 22r0s are on order already.

vmaxer wrote: »

I am looking forward to your thoughts on how they sound when completed. I hope they are awesome.

Thanks Vmaxer! I hope so too or that divorce may come true.

markamerica

One of the things I've considered is leaving the cosmetic treatment for last/later. The SRSs are not too bad despite the feline pest, and I'm beginning to look at another project. This one has been back-burnered for a long, long while, but after the success of the center channel, I'm getting my gumption up. I KNOW some of you will disapprove, and will accuse me of creating SDA-FrankenPolks or some such, but it won't cost me that much to try it out.

At present, I have a full set of the guts of a pair of 1Bs. All the MWs, the tweeters, the passives, and even the crossovers along with terminal cups. They just need a cabinet.

Here's where I offend some sensibilities, no doubt. I am considering making the world's largest SDA bookshelf speakers ever. In my living room, at the rear of the room, nestled between the 1.2TLs is a German shrank(like a big wall unit with cabinet doors, bookshelves, a center glass-front curio cabinet section, etc) Above it is empty space, but the ceiling slopes, following the roofline of my abode, toward the outside wall leaving about only 9.5 inches overhead, and at the center of the shrank, only about 16 inches overhead. So here was the idea, in illustrated form:

I put the outline of the shrank in red, the 1.2TLs in blue, and the proposed frankenpolks in orange. By the way, I've fittingly dubbed them SDA-1B.BS, the BS standing for "BookShelf" or perhaps the obvious alternative if you happen to disapprove. In order to try to show what I expect to happen at the best listening position in the room, I've drawn an overhead view with a brown circle at a green cross to represent my fat head in the second picture.

In order to attempt to compensate for the broad horizontal layout of the MWs, what I've done is place both stereo inboard and both dimensionals outboard. Using the cursed toed-out front baffles, I'm hoping (although the third dimension isn't represented here) that this will give the aural illusion of the point of origin for the mid signal to be approximately between the MWs and that the slightly increased delay in the arrival of the dimensional canceling signal won't be too drastically noticeable. I'm also hoping that with a slight offset of the tweeters, I can essentially place their signals in a straight line to the optimal listening position in the room.

That's right, I don't care what anybody else hears...LOL I'm the only one who will appreciate it anyway.

The thinking is to maintain the volume of the cabinets at parity with the 1Bs from which these guts came, and one thought I had was to place the PR rear-facing essentially behind the MWs, eliminating the large squarish boxy section toward the center, though I'd probably use some sort of internal baffle arrangement.

Here are the hastily prepared .jpgs of the idea. (I can just hear the cringing.)



Okay, this is what happens when one has a free Saturday morning to relax for a bit. Don't hate me...

markamerica

BKphoto wrote: »

P I C S ...!



or we don't believe you...

Sorry BKphoto, at this time, all I can show you are the parts on hand:

BKphoto

those caps look as big as a can of soup...

markamerica

BKphoto wrote: »

those caps look as big as a can of soup...

Not quite, BKphoto, but the 20uf units are nearly as big as a can of tomato paste. For scale:

TNTsTunes

markamerica wrote: »

One of the things I've considered is leaving the cosmetic treatment for last/later. The SRSs are not too bad despite the feline pest, and I'm beginning to look at another project. This one has been back-burnered for a long, long while, but after the success of the center channel, I'm getting my gumption up. I KNOW some of you will disapprove, and will accuse me of creating SDA-FrankenPolks or some such, but it won't cost me that much to try it out.

At present, I have a full set of the guts of a pair of 1Bs. All the MWs, the tweeters, the passives, and even the crossovers along with terminal cups. They just need a cabinet.

Here's where I offend some sensibilities, no doubt. I am considering making the world's largest SDA bookshelf speakers ever. In my living room, at the rear of the room, nestled between the 1.2TLs is a German shrank(like a big wall unit with cabinet doors, bookshelves, a center glass-front curio cabinet section, etc) Above it is empty space, but the ceiling slopes, following the roofline of my abode, toward the outside wall leaving about only 9.5 inches overhead, and at the center of the shrank, only about 16 inches overhead. So here was the idea, in illustrated form:

I put the outline of the shrank in red, the 1.2TLs in blue, and the proposed frankenpolks in orange. By the way, I've fittingly dubbed them SDA-1B.BS, the BS standing for "BookShelf" or perhaps the obvious alternative if you happen to disapprove. In order to try to show what I expect to happen at the best listening position in the room, I've drawn an overhead view with a brown circle at a green cross to represent my fat head in the second picture.

In order to attempt to compensate for the broad horizontal layout of the MWs, what I've done is place both stereo inboard and both dimensionals outboard. Using the cursed toed-out front baffles, I'm hoping (although the third dimension isn't represented here) that this will give the aural illusion of the point of origin for the mid signal to be approximately between the MWs and that the slightly increased delay in the arrival of the dimensional canceling signal won't be too drastically noticeable. I'm also hoping that with a slight offset of the tweeters, I can essentially place their signals in a straight line to the optimal listening position in the room.

That's right, I don't care what anybody else hears...LOL I'm the only one who will appreciate it anyway.

The thinking is to maintain the volume of the cabinets at parity with the 1Bs from which these guts came, and one thought I had was to place the PR rear-facing essentially behind the MWs, eliminating the large squarish boxy section toward the center, though I'd probably use some sort of internal baffle arrangement.

Here are the hastily prepared .jpgs of the idea. (I can just hear the cringing.)



Okay, this is what happens when one has a free Saturday morning to relax for a bit. Don't hate me...

I don't get offend by FrankenPolks, but I will say the tweeters shouldn't be angled IMO. Other the that it might work pretty well.

I have a few different creations in mind for some surround sound speakers....

drumminman

Mark, given your success with your center and your willingness to experiment it's an intriguing idea. A couple of questions:

Why the toe out? That's counter to SDA placement requirements.

Also, given that you're using 1.2's for the front L-R mains, would an SDA center produce conflicting audio information causing the soundstage to be a little confused? I'm wondering if more SDA effect is not better in this situation.

Of course there's only one way to answer both of these questions. If the answers go against your plans, corrective mods would be easy to implement: repositioning for the first, reworking the Xover for the 2nd.

westmassguy

The Dome Tweeters have about a 120 degree dispersion if memory serves, but still beam above a certain frequency, depending on who designed them. The way you have them angled, you may end up with a hole in the middle. Maybe a stepped slope would mitigate that. Time alignment will suffer, but the drivers will all be parallel.

BKphoto

markamerica wrote: »

BKphoto wrote: »

those caps look as big as a can of soup...

Not quite, BKphoto, but the 20uf units are nearly as big as a can of tomato paste. For scale:

wowie...!

markamerica

TNTsTunes wrote: »

I don't get offend by FrankenPolks, but I will say the tweeters shouldn't be angled IMO. Other the that it might work pretty well.

I have a few different creations in mind for some surround sound speakers....

TNTsTunes,

To answer this, one of the things I was looking at was an interrupted slope, sort of what I think Westmassguy mentions with a "stepped slope", where the space between the mids on the front baffle resumes a flat orientation. It would be a bit harder to build, but then, that's half the fun.

drumminman wrote: »

Mark, given your success with your center and your willingness to experiment it's an intriguing idea. A couple of questions:

Why the toe out? That's counter to SDA placement requirements.

Drumminman,

The reason SDA's don't work toed-out or toed-in is because of the spacing between the mid relative to the listener's ears. With SDAs of the factory construction, the mids are place to be approximately where center-to-center, the stereo drive and its corresponding dimensional driver are spaced the width between our ears. On factory SDA speakers, toe-in makes that separation greater relative to our ears, and toe-out narrows it. What this pair of SDA-1B.BS speakers I propose is to use that narrowing function of toe-out because I've place the two stereo drivers inboard and the two dimensionals outboard. On a flat baffle(parallel to the wall or the back of the cabinet,) this arrangement would tend to make that separation much greater, more than a foot, because I have the stereo and dimensional drivers side-by-side in the vertical positioning, rather than stacked, like on factory SDAs. More like a fat 16". By giving the front baffle significant toe-out, the notion is to intentionally narrow the spacing between the Stereo and Dimensional pairs, relative to the optimum listening position in the room, bringing the apparent perceived signals from the pairs of stereo and dimensional drivers much closer to parallel lines.

drumminman wrote: »

Also, given that you're using 1.2's for the front L-R mains, would an SDA center produce conflicting audio information causing the soundstage to be a little confused? I'm wondering if more SDA effect is not better in this situation.

Of course there's only one way to answer both of these questions. If the answers go against your plans, corrective mods would be easy to implement: repositioning for the first, reworking the Xover for the 2nd.

This picture is the rear of the room only. The 1.2TLs are my rear channel speakers. The custom center and the SRSs are at the opposite end of the room, not represented in this drawing. The Center does NOT use SDA technology, having been talked-down off that ledge by wiser minds(thanks guys) a year or so ago, for exactly the muddling tendency you describe. The Center is instead just a straight-up loudspeaker, but my hope was to be able to reinforce the center of the virtual sound-stage, particularly for strong vocals performances, and it has done exactly that. I watched the movie "We Were Soldiers," with this room in full effect. With the 1.2TLs at the back of the room, and the complement on the front wall(SRSs and Center,) it sounded right, which is to say when the helicopter comes into the hot LZ from the left and moves slightly over head and to center, I guess my Outlaw Preamp does a decent job of getting the Surround effect right, because at the optimum listening position in the room, I momentarily felt the pressing need to duck.

westmassguy wrote: »

The Dome Tweeters have about a 120 degree dispersion if memory serves, but still beam above a certain frequency, depending on who designed them. The way you have them angled, you may end up with a hole in the middle. Maybe a stepped slope would mitigate that. Time alignment will suffer, but the drivers will all be parallel.

Westmassguy, I had worried about that very thing, and one of my baffle layouts includes an interrupted slope, I think probably conforming to your "step slope." I had also considered that this would place the tweeters at a bad angle relative to the adjacent stereo driver, and I wondered if that wouldn't be problematic. I agree that time alignment will suffer marginally, but the narrowing function of the toe-out should keep the lines approximately parallel. I'll play with it some more. Like I said, this is what happens when I get left with a few hours of unscheduled free time.

Thanks all!

Mark

markamerica

Westmassguy, Here's the general idea of a stepped slope or interrupted slope, again not to precise scale or angles:

markamerica

Westmassguy, that's one of the troubles in designing with parts on which I don't have all the specifications. It would be good to know the exact dispersion of those tweeters. At 120 degrees, I might not have to bother with the step, but as you suggest, that 120 degrees probably narrows substantially above a certain frequency, and that would be good info too. Like I said, this(SDA-1B.BS) is something that's been rattling around in my head for years. Part of me would like to do it just to see, but then again, those resources could be expended on things I know will work. I may do this after I get the SRS mods/upgrades complete, just to satisfy my curiosity and give me something to do while I save up for the 1.2TL mods/upgrades I hope will come about late next summer.

westmassguy

Mark the vocal range extends from 200Hz to 6-7KHz approximately. That means a lot of it is being handled by the woofers. You may have to do the steps for the Stereo Woofers too. You'll want to factor in lobing with things pointing in different directions.

markamerica

Drumminman,

I've created two quick and dirty drawings to illustrate what my words may not have successfully conveyed. In the first drawing below, a pair of factory SDA speakers, whichever type you prefer, and all I'm concerned with here is the midwoofers, specifically, the stereo and dimensional drivers. So I guess, imagine this is a pair of SDA-2Bs, for the sake of argument. In the flat against the wall alignment, the cabinets drawn in black, the blue lines represent the sound you will hear at the ears of the listener, represented by the gray circle. You can see that these lines are and should be very nearly parallel. (The blue line from the Stereo and the blue line from the Dimensional, per side.)
The green cabinet with the red lines represents a toed-in configuration. Notice that the red lines are nowhere near parallel with respect to each side. Relative to the listener, what this has done is increase the spacing between the stereo and dimensional drivers.
The orange cabinet represents a toed-out configuration, and the purple lines go with these. Again, note that the lines are no longer approximately parallel, but that what has happened is that by rotating the cabinets outward, the spacing between the stereo and dimensional driver has been substantially narrowed.
In either the toed-out or toed-in configuration, the SDA effect is being demolished.



However, with the toed-out configuration, the narrowing is what I am after in the second picture, below. In the second picture, the orange cabinets obviously have a flat face. From the perspective of the listener, because I have the two stereo drivers side-by-side(not stacked vertically,) the sound will seem to originate from a mid-point between the two stereo drivers, and the same with the outboard dimensional drivers. On the orange(flat-baffled) cabinet, you will note the lines to the ears of the listener are nothing like parallel because with the horizontal pairings, the spacing between the apparent origination of the signals will be overly broad.




The green cabinets use the premise of the orange cabinets in the first drawing, which is to narrow the apparent spacing between the stereo and dimensional signals relative to the listener's ears. Notice that the green cabinets in the second drawing, by having sloped-away faces(toed-out), this narrows the apparent spacing between the inboard stereo drivers and the outboard dimensional drivers. Notice that the lines come much closer to parallel with respect to the listener's ears on the green cabinets in the second drawing. In this way, a toed-out condition should create the same sort of dimensional field intended by the factory SDAs, but as Westmassguy and I have discussed above, there may be a marginal time-delay issue created by the fact that the dimensional drivers are now so much further away from the listeners. Essentially, while I've managed to make the lines more parallel, I've dramatically increased the length of the line to the dimensional pair. That additional length represents additional time, very small, naturally, and my gamble would be that this would be very very subtle. This is not the sound of thunder from sources, one 8 miles away and one 9 miles away, respectively, but the sound of woofers 8 feet away and 9 feet away, respectively. At 8 versus nine miles, there would be an approximate five second difference in the arrival of the sound of thunder. At 8 versus 9 feet, the difference, I'm hoping, will be negligible.

Anyway, that's the logic I'm using here, and I hope with the drawings, it does a better job of helping to explain my thinking. Sometimes, I'm not too eloquent, and I don't convey things well, so pictures help. The other piece, the notion of stepping the front baffle, is to address the dispersion of the tweeters. Toed-out, at higher frequencies, what Westmassguy and TNTsTunes correctly point out is that the sound from the tweeters might well disappear at my optimum listening position. By essentially negating the toe-out for the tweeters only, it should cancel that tendency.

I hope this helps. Like I said, I'm not always the best at describing what I can see in my mind's eye(or hear in my mind's ear).

Mark

markamerica

Drumminman,

I should mention that the only reason I'm considering this particular configuration is because of the limited vertical space available at the back of the room due to the slope of the ceiling and the height of the large German shrank(wall unit) at the back of the room. Otherwise, if overhead clearance were available, I'd simply stack the Stereo and Dimensional drivers respectively, the front baffles could be flat because the spacing of the dimensional and stereo drivers would conform to standard SDA layout, and call it a day. This is strictly to address the limitations of the room, which is why it's a problem that's been rattling around in my head for years.

I should mention that this room will hopefully not be the final resting place of me and my gear. This house is a temporary accommodation, I hope anyway, as the wife and I pay off things and close in on retirement, we'll be saving to build the retirement house at which time I will design the room unencumbered by my current limitations. If things go reasonably well, I hope that in a decade, we'll be in a structure more conducive to my listening pleasure, though the reason I may go forward with this experiment is because I worry that a.)I may never survive to hear it, and b.) my hearing may be degraded to the point that even if I build it, I won't be able to appreciate it any longer. My stop-gap SDA-1B.BS idea is to make it possible to do what I want in the here and now, before nature takes this source of pleasure from me, or diminishes it to an extent that will be frustrating.

I hope that makes plain my motive with this experiment, even if my logical approach seems flawed to you or others.

Thanks!

Mark

markamerica

westmassguy wrote: »

Mark the vocal range extends from 200Hz to 6-7KHz approximately. That means a lot of it is being handled by the woofers. You may have to do the steps for the Stereo Woofers too. You'll want to factor in lobing with things pointing in different directions.

Were you thinking an arrangement like this? See below:

I thought about that too, but I had nightmares about building that front baffle...LOL

On the other hand, would I need the separate step for the tweeters at all, or could I just put them on the same plane as the dimensionals, or even the stereo drivers, effectively removing a step?

Of course, as I said in an earlier post, I have considered making the PR wall-facing, much in the style of the CRS, or half the 6.5 passives in my Center.

Mark

westmassguy

markamerica wrote: »

westmassguy wrote: »

Mark the vocal range extends from 200Hz to 6-7KHz approximately. That means a lot of it is being handled by the woofers. You may have to do the steps for the Stereo Woofers too. You'll want to factor in lobing with things pointing in different directions.

Were you thinking an arrangement like this? See below:

I thought about that too, but I had nightmares about building that front baffle...LOL

On the other hand, would I need the separate step for the tweeters at all, or could I just put them on the same plane as the dimensionals, or even the stereo drivers, effectively removing a step?

Of course, as I said in an earlier post, I have considered making the PR wall-facing, much in the style of the CRS, or half the 6.5 passives in my Center.

Mark

I'd make the tweeter and stereo drivers on the same plane

markamerica

westmassguy wrote: »

I'd make the tweeter and stereo drivers on the same plane

Westmassguy, so basically like this:


I'd just need to be careful to not make that step slope steeper than the dispersion of the dimensional mids, or essentially obscure them, at least the one closer to the slope of the step. Still the time issue, but that's unavoidable in this kind of arrangement, I think.

Mark

westmassguy

Won't know till you try it