New to me SDA CRS+
Coastsider
Posts: 9
I recently came into possession of a pair of SDA CRS+ Polks in a package deal. These are my first Polks and I am in new territory. I discovered that both tweeters are blown and upon pulling the midrange drivers, found that one of the crossovers had broken loose from it's mounting on the large choke. So the mids are good and the crossover back in place and I am wondering if I should spend the $120+ for a pair of BD194-A replacement tweeters. Not being able to judge the speakers in their present condition, I am soliciting opinions as to whether or not the investment to restore them is a good one.
Thanks in advance for any opinions offered.
Thanks in advance for any opinions offered.
Post edited by Coastsider on
Comments
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Sal, the crs+ are the last crs made hence 1 tweeter.
In regards to these crs +, they're worth a full upgrade (tweeters,crossovers).SRT For Life; SDA Forever!
The SRT SEISMIC System:
Four main satellite speakers, six powered subs, two dedicated for LFE channel, two center speakers for over/under screen placement and three Control Centers. Amaze your friends, terrorize your neighbors, seize the audio bragging rights for your state. Go ahead, buy it; you only go around once. -
Welcome to the forum where information and help is always available
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Not sleeping - just having a late dinner.
Just one tweeter per speaker - correct. These are the smallest model of the SDA line and I only know that because included with everything else I got was a great full color Polk brochure from 1988 with Matthew Polk on the cover standing next to an SDA SRS and surrounded by the rest of the line.
At $48 each I'll probably go ahead and get them operational again and I understand that the RD0194's are an improvement over the original tweeters as well. I'll probably wait until I have a chance to do some listening before I dive into recapping the crossovers, which I might say are pretty impressive for such a small speaker. I'll have to search for a schematic.
Anyhow - thanks for the welcome and the feedback. I'll get on the phone to Polk in the morning and order the tweeters. -
You can find a mod for the crs+ here. It will convert the crs+ to the 4.1 tl
just use the search feature.SRT For Life; SDA Forever!
The SRT SEISMIC System:
Four main satellite speakers, six powered subs, two dedicated for LFE channel, two center speakers for over/under screen placement and three Control Centers. Amaze your friends, terrorize your neighbors, seize the audio bragging rights for your state. Go ahead, buy it; you only go around once. -
Thanks. I'll look for it in the morning.
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IMO, you should hold off on ordering the RD0194-1's. The 4.1TL upgrade is well worth doing, but uses the RD0198-1 tweeters in addition to adding a 5.8uF cap to each crossover.
Have checked the polyswitches? If they have failed, you'll get no sound from the tweeters.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
IMO, you should hold off on ordering the RD0194-1's. The 4.1TL upgrade is well worth doing, but uses the RD0198-1 tweeters in addition to adding a 5.8uF cap to each crossover.
Have checked the polyswitches? If they have failed, you'll get no sound from the tweeters.
Polyswitches . . . . . hmmmm - I haven't but it sounds like they are some sort of fuseable link in the tweeter circuit and apparently not fast enough to save them and I suspect located on the crossover circuit board. I guess I need to spend some time in here this morning researching all of this new information and looking for a schematic. Upgrading sounds good too as long as I'm replacing both tweeters with non-original drivers anyway and assuming that the RD0198's are not much more expensive than the RD0194's since the cost of a couple of capacitors is not likely to break the bank..
And here I thought I was getting a great set of bookshelves for basically free. -
Glad I was putting off upgrading my CRS+ till after I move - I hadn't read about the 4.1TL upgrade yet.
Also
Does anyone know how many watts a tube amp needs to be to power these?
With 92Db efficiency - will a 10Watt Tube amp power them? -
Coastsider, I highly recommend the RDO 4.1TL upgrade. I fully rebuilt mine with Sonicaps and Mills, and they are outstanding speakers. If you have any questions about the process, feel free to shoot me a PM; and welcome to the club.
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clarknova_666 wrote: »Does anyone know how many watts a tube amp needs to be to power these? With 92Db efficiency - will a 10Watt Tube amp power them?
Is that 10wpc or 10 total, thus 5wpc? If it is a 10 watt amp and 5wpc, that will not be enough for sure. However, 10wpc might sound fine in a smaller room, but I might worry a little about balancing that with correct SDA placement. I run my Monitor 5Jrs with a 16wpc tube amp and love the sound; and my monitors are only about 90db efficient. At that amount of power, you won't be getting "everything" out of the speakers like you could with a high current amp, but I like mine.
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The RD0198's are the same price. Just call Polk Customer Service and mention that you are a club Polk member and you will pay $48 each with free two day shipping.
The polyswitches are either mustard colored or blue, they are usually round and about 0.25" diameter
You can jump them to test if they are blown, if they are blown your tweeters may come back to life if you jump them.
I do not use them at all, I took mine out and installed a small jumper. You should only do this if you know that you have huge reserves of clean power.
On my system I know that if I go beyond 84 on the volume dial that I will be frying some tweeters.
Lasareath, is there any possibility of eliminating the polyswitch with a jumper and going "old school", by installing a fuse holder in the jumper loop ? I like the protection idea in case unauthorized people Eff with the volume control, and a fuse is simple and sure.Geoff:) -
Las/Sal, thanks, I wonder if it's just the switch that affects the sound,or does the small conductor of a fuse also do bad things ? I will ask Ben about this too, I'm hoping to have him do upgrades on several sets of XOs for me soon. Geoff:)
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If you are really worried, I would just get the new ones from Polk like Sal was saying. The protection can be worth more than the coloration that if may provide. (I think Polk gives them out for free, but don't quote me on that
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The RD0198's are the same price. Just call Polk Customer Service and mention that you are a club Polk member and you will pay $48 each with free two day shipping.
The polyswitches are either mustard colored or blue, they are usually round and about 0.25" diameter
You can jump them to test if they are blown, if they are blown your tweeters may come back to life if you jump them.
I do not use them at all, I took mine out and installed a small jumper. You should only do this if you know that you have huge reserves of clean power.
On my system I know that if I go beyond 84 on the volume dial that I will be frying some tweeters.
My forum searches this morning turned up lots of valuable info on the 4.1TL upgrade and how to ID the polyswitches and so on. I actually initially pulled the tweeters and checked them for continuity and found none so they are fried but I'll probably get some new polyswitches just for the sake of argument as they are likely also blown. Are they socketed on the Xover board?
As I mentioned, I may just buy the RD0198's and the caps for the upgrade and hold off going for the full recap until I hear how they sound since I am as yet uninitiated and also undecided as to where these new Polks fit into the scheme of things.
I really do appreciate all of the interest and help. Pretty active forum you've got here. -
I think you will be best off doing the caps and resistors together also replacing the polyswitchs while your soldering.
Drew -
Armed with schematics and phillips head screwdriver I just determined that my CRS+ Polks are the 1989 version as they have the 6510/6511 combination of drivers, and since the crossovers are pretty accessible, I'll probably go for the whole deal with the 4.1TL upgrade and a full recap. I may as well see just how good these speakers can sound right out of the gate. But is it really necessary to replace the resistors as well?
One last quick question: If the polyswitches are blown, do they look like they are blown? Mine still look nice and blue and all pristine.
Anyhow, I've got my work cut out for me with this unexpected new project so we'll see how it goes. -
Do not replace the poly's with a fuse. Neither poly or fuse will color the sound, rather they are a choke point. Resistors make a huge difference. Poly's don't blow up, they just fail to work properly.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Thanks Jesse, good to know!! If a polyswitch fails, will it endanger the tweeters, or just stop supplying them with power, and provide the ultimate protection? Geoff
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A polymeric positive temperature coefficient device (PPTC, commonly known as a resettable fuse) is a passive electronic component used to protect against overcurrent faults in electronic circuits. They are actually non-linear thermistors, however, and cycle back to a conductive state after the current is removed, acting more like circuit breakers, allowing the circuit to function again without opening the chassis or replacing anything. These devices are often used in computer power supplies, largely due to the PC 97 standard (which recommends a sealed PC that the user never has to open), and in aerospace/nuclear applications where replacement is difficult.[1]
These devices are sold by different companies under various trademarks, including PolySwitch (Tyco Electronics), Everfuse (Polytronics), Polyfuse (Littelfuse) and Multifuse (Bourns).
A PPTC device has a current rating. When the current flowing through the device, (which has a small resistance in the on state) exceeds the current limit, the PPTC device warms up above a threshold temperature and the electrical resistance of the PPTC device suddenly increases several orders of magnitude to a "tripped" state where the resistance will typically be hundreds or thousands of ohms, greatly reducing the current. The trip current can be anywhere from 20 mA to 100 A.
A polymeric PTC device comprises a non-conductive crystalline organic polymer matrix that is loaded with carbon black particles to make it conductive. While cool, the polymer is in a crystalline state, with the carbon forced into the regions between crystals, forming many conductive chains. Since it is conductive (the "initial resistance"), it will pass a given amount of current, called the "hold current". If too much current is passed through the device, the "trip current", the device will begin to heat. As the device heats the polymer will expand, change from a crystalline state into an amorphous state. (Since the device physically expands, it must be given some empty space on the PCB.) The expansion separates the carbon particles and breaks the conductive pathways, causing the resistance of the device to increase. This will cause the device to heat faster and expand more, further raising the resistance. This increase in resistance is sufficient to substantially reduce the current in the circuit. A small amount of current will still flow through the device and is sufficient to maintain the temperature of the device and keep it at the high resistance level ("latching" functionality).
When the power and fault are removed, the PPTC device will cool. As the device cools, it contracts to its original shape and returns to a low resistance level where it can hold the current as specified for the device. This cooling usually takes a few seconds, though a tripped device will retain a slightly higher resistance for hours, slowly approaching the initial resistance value. -
The stock resistors are crap comparred to mills.
You might as well do the job correctly, it's very easy once you start going.
Where are you located?, There might be a polkie near by that can help you.
What will you power the speakers with?, if you have a lot of clean power you may not even need the polyswitches.
Sal
I'm on the California Coast about 25 miles south of San Francisco.
I'll probably source everything out this weekend and get what I need on order so all of the bits will be on hand when I have the time and energy to attack this.
I've been working in IT off and on for a good part of my adult life beginning way back in the mid-late '60's before IT was called IT when soldering was a required skill, so I'm good to go in that respect. It's just a matter of familiarizing myself with the hardware and I've managed to get a good head start on that thanks to information on this forum and a surprisingly enthusiastic response to my post.
Right now I'm using a Soundcraftsmen MA5002 in my office at home to power whatever speakers I happen to have on hand and that's what I'll use for the Polks once I get them done. It's a backup for the MA5002 that I use to power a pair of amp-eating Infinity RS 2.5's in my main setup.
As far as the polyswitches go, I'll feel more comfortable having some sort of protection for the tweeters so I'll probably ask Polk to throw a couple in with the RD0198's and I'll see if that vendor who's having the 15% off sale right now has the rest of the components I need.
I'll post updates when I get started.
