Can I bridge my SDA-1C speakers?

003

Hi guys, I've got an Onkyo TX-NR5007 receiver with a pair of SDA-1C speakers. The receiver specs are here:
http://www.us.onkyo.com/model.cfm?m=TX-NR5007&class=Receiver&p=f

The receiver supports bridging the front LR channels and also bi-amping. On the back of the speakers it says to never bridge them. Why is that? Can I do it if I don't use the interconnect cable? If not, can they be safely bi-amped?

Please let me know! Thanks :biggrin:

F1nut

You cannot use a bridged amp(s) with your SDA's unless you use the AI-1 isolation transformer and you can only use the AI-1 with certain 1C's.

Yes you can, but why bother? You'll basically lose half of the speaker.

You cannot bi-amp 1C's as they only have one set of binding posts. Besides, passive bi-amping is a complete waste.

Joe08867

You can't bridge SDA's because they need to cross talk with one another. It is not a good idea to use any bridged amp with them as it will cause a short between the 2 amps and the speakers.

Disconnecting the interconnect will cause an enormous loss of sound from the speakers. You will loose the use of one driver and one tweeter from each speaker. Literally cutting the sound in half.

That receiver should do a good job the way it is without trying to bridge it or bi-amp the SDA's. If you want more sound from them I suggest an external amp that has the power you are looking for.

Toolfan66

I vote ditching the receiver and getting seperates (pre amp and amplifier with good current)!!! Just my opinion!! Your ears and speakers will thank you!!

If your going to run them with out the cable then sell them IMO!!

Good luck with your set up and have fun!!!

003

F1nut wrote: »

You cannot use a bridged amp(s) with your SDA's unless you use the AI-1 isolation transformer and you can only use the AI-1 with certain 1C's.

What is this AI-1 isolation transformer you speak of, how can I tell if my 1Cs would work with it, and where would I be able to get one?

You guys don't need to tell me a separate amp/preamp would be fantastic, I am well aware of that, but I have literally no space for a single extra component. I had to ditch my Rotel CD player and have my Blu-ray player play double duty just to put in a DVR. I am also STRAPPED.

If there is anything I can do to run them in bridge mode, I'll do it! :cool:

PS: Didn't know not using the interconnect disables some of the drivers. All right that idea is out.

heiney9

003 wrote: »

What is this AI-1 isolation transformer you speak of, how can I tell if my 1Cs would work with it, and where would I be able to get one?.

See link

http://www.polkaudio.com/forums/showthread.php?t=74472&highlight=dread%2A

You would have to build one as the original sold by Polk are rare used finds these days. Polk no longer manufacture's them.

The place to start is with your SDA 1C serial numbers to find out if you can even use the AI-1 cable.

The cost to build an AI-1 is around $200-300 give or take depending on the level of finish you want. Having the parts mounted to a piece of ply-wood is about $200. I a nice case with nicer cables, etc will be closer to $300.

003 wrote: »

If there is anything I can do to run them in bridge mode, I'll do it! :cool:.

The isolation transformer is the only way if your 1C's are later production units that can use the AI-1. IMO, the cost vs. the benefit based on your gear isn't worth it. Spending $200-300 just so you can bridge a medioce receiver is a waste of money

003 wrote: »

PS: Didn't know not using the interconnect disables some of the drivers. All right that idea is out.

Good call, just leave things as they are.

H9

Schurkey

Joe08867 wrote: »

Disconnecting the interconnect will cause an enormous loss of sound from the speakers. You will loose the use of one driver and one tweeter from each speaker. Literally cutting the sound in half.

Might have been true for older SDAs, but NOT for 1B or 1C, or several other of the newer-generation SDAs.

Yanking the interconnect cable on my 1B results in a drastic change in the soundstage, but not so much change in the frequency response or "voicing". I expect the 1C to be similar--soundstage collapses to "ordinary" stereo, but the timbre remains similar with/without the interconnect cable.

Try it and see! It's not like you're going to hurt anything by disconnecting the cable.

heiney9 wrote: »

The cost to build an AI-1 is around $200-300 give or take depending on the level of finish you want. Having the parts mounted to a piece of ply-wood is about $200. I a nice case with nicer cables, etc will be closer to $300.

If he builds an AI-1 to the same specs as the OEM Polk unit, it would be about fifty bucks, maybe less. The raw transformer would be something like $20--$25 shipped, plus some cables and terminations.

http://www.polkaudio.com/forums/showthread.php?t=55888 Post #6.

Additional info:

SPC Technology 81N5406 data sheet shows 1.3mA secondary output. http://www.spctechnology.com/prodinfo/specs/81n5406.PDF

It is no longer available. Crosses over to become Newark Part Number: 10M5581. Newark calls it an "exact substitute" but I can't find specs on secondary current.

Stancor 01F043 crosses over to Newark p/n 16M3806; Secondary Current Nominal:0.13A

Magnetek Triad 03F1017 crosses ("exact replacement") Newark Part Number: 78K8609; again Secondary Current Nominal:0.13A

The OEM Polk unit is good for .13 amps; and that is NOT enough...but it was good enough for Polk at that time. Any suitable isolation transformer than can handle more than .13 amps is almost certainly better than the OEM unit. Using the "Dreadnaught" style, at something like 6 or 7 amps is quite superior...but not absolutely required.

heiney9 wrote: »

The isolation transformer is the only way if your 1C's are later production units that can use the AI-1. IMO, the cost vs. the benefit based on your gear isn't worth it. Spending $200-300 just so you can bridge a medioce receiver is a waste of money

Agreed.

heiney9

I didn't give him the $50 option, because to my way of thinking that's sort of half/assing it. But then again so is bridging an average receiver. I know we are all at different levels and have different budget's and other varying factors.

I still wouldn't recommend removing the inter-connect cable on SDA's. The nature and uniqueness of the speaker is lost and in this case it would be for a few more watts and not necessarily better sounding watts. Can it be done without damage? Yes. Is it beneficial? No.

All, IMO of course.

H9

gdb

Brand new, never used AI-1 interface unit available. PM for info.

003

The serial number for my 1Cs are 12003. Will that work with the AI-1?

Also I just thought of something else. These speakers will not work without a common ground. Typically, bridging two separate amps removes any common ground that may have previously existed. Is that the reason it says to never bridge them?

Because if I do it on a receiver, won't the fact that it's all one chassis mean that even bridged, there will still be a common ground??

treitz3

Why would you want to bridge a receiver anyway? If more watts is what you want, you'll get it but with the loss of SDA and the bass will get sloppy. I see no benefit whatsoever to do what it is you are trying to do. None.

FTGV

heiney9 wrote: »

I still wouldn't recommend removing the inter-connect cable on SDA's. The nature and uniqueness of the speaker is lost and in this case it would be for a few more watts and not necessarily better sounding watts. Can it be done without damage? Yes. Is it beneficial? No.

Slam dunk.

003 wrote: »

Because if I do it on a receiver, won't the fact that it's all one chassis mean that even bridged, there will still be a common ground??

No because in bridged mode the negative half of the signal will be taken from one of the bridged channels positive or "hot" terminal and therefore is not tied to ground.In other words only the positive terminals of the 4 amp sections are used when operating in bridged mode.

003

All right... thought that wouldn't work but it was worth a shot. Well, I am going to have these speakers for the foreseeable future. The receiver was very expensive, got it for $1500 used with a 5 year warranty, it retailed for over $2000. I have very little money to spend. So new speakers or a new amp are out of the question.

Based on my serial number how can I tell if the AI-1 will work for me? Serial is 12003.

EDIT:

Wait a second. I saw a picture of the original AI-1 cable, it is just the same interconnect except with a box in the middle. If I disconnect the cable, can I bridge the speakers? I know I'll lose the SDA effect but I will be able to gauge the difference in sound using bridged vs non-bridged and be able to decide if I even need the AI-1.

heiney9

003 wrote: »

All right... thought that wouldn't work but it was worth a shot. Well, I am going to have these speakers for the foreseeable future. The receiver was very expensive, got it for $1500 used with a 5 year warranty, it retailed for over $2000. I have very little money to spend. So new speakers or a new amp are out of the question.

Based on my serial number how can I tell if the AI-1 will work for me? Serial is 12003.

EDIT:

Wait a second. I saw a picture of the original AI-1 cable, it is just the same interconnect except with a box in the middle. If I disconnect the cable, can I bridge the speakers? I know I'll lose the SDA effect but I will be able to gauge the difference in sound using bridged vs non-bridged and be able to decide if I even need the AI-1.

Your SDA's have the same serial # for both right and left? That's really not possible. They could be consecutive numbers (rare) but not the same. Since SDA's are sold as indivudual units they have the left speaker has it's own serial # as well as the right speaker.

The AI-1 cable you see has a transformer in-line to cope with the non-common ground issue.

The part I bolded in the quote above, I have no idea what you mean. If you can get a factory AI-1 from a member here for a decent price and you are dead set on trying to bridge a receiver that would be the best way. I still don't recommend it, because the payoff will be negligible, but we're always telling people to try things for themselves, so have at it if you must.

Give me a few minutes to locate my SDA bible and look up the one serial number you gave me. Please give me the other one. Is your current cable blade/blade on each end or pin/blade on each end?

FTGV

What is the impedance of the 1C's?Since when bridging the load as seen by the amp is half that of the nominal impedance therefore that reciever may have thermal issues trying to deliver high power into those speakers in bridged mode.

SDA1C

I have owned 1c's for quite a while now and trust me...you don't want to do anything that requires you disconnect the interconnect cable. From my past exp they handle less power efficiently and if you do the close your eyes test it'll almost make you vomit on how much SQ goes out the window. I find that a strong 15" or larger sub does wonders. The 1c to me is a bit shy on the bottom end (but rock **** from about 200 htz upwords). So cut the bass down on the receiver. Turn on a 15" sub and you'll get mass SP increase. Just my .02 bro but believe me its a few years trial and error to get that .02 lol.

Take care,
1c


mine are 4.0 ohm nominal. 3.5 from pos to IC and 2.3 from neg to IC I only checked the left side though.

heiney9

FTGV wrote: »

What is the impedance of the 1C's?Since when bridging the load as seen by the amp is half that of the nominal impedance therefore that reciever may have thermal issues trying to deliver high power into those speakers in bridged mode.

Fred if they are 1C's they are 6 ohm nominal. I was corresponding with Nelson Pass before I bought my Aleph 30 about the common ground issue and I sent him a couple schematics and his comment was "looks like they could put quite a strain on the negative side of an amplifier" Of course the Aleph is common ground as you know.

My point being, that sometimes it's not only the nominal impedance tha can give amps some fits, but because of the way the speakers are "cross-wired", for lack of a better term, some amps may have difficulty aside from impedance.

That's my guess as to his comment and why some amps get hot or have difficulty running SDA's even though the impedance is fairly benign.

H9

heiney9

SDA1C wrote: »

I have owned 1c's for quite a while now and trust me...you don't want to do anything that requires you disconnect the interconnect cable. From my past exp they handle less power efficiently and if you do the close your eyes test it'll almost make you vomit on how much SQ goes out the window. I find that a strong 15" or larger sub does wonders. The 1c to me is a bit shy on the bottom end (but rock **** from about 200 htz upwords). So cut the bass down on the receiver. Turn on a 15" sub and you'll get mass SP increase. Just my .02 bro but believe me its a few years trial and error to get that .02 lol.

Take care,
1c


mine are 4.0 ohm nominal. 3.5 from pos to IC and 2.3 from neg to IC I only checked the left side though.

I agree no one should run without the cable, I strongly disagree the 1C's lack bottom end. It's all about the gear you run and placement. I can rattle rafters with my 1C's when the musical content is there.

Also how are you measuring impedance? You can't just hook up a DVM to the terminals. Impedance varies greatly with frequency.

H9

003

heiney9 wrote: »

Your SDA's have the same serial # for both right and left? That's really not possible. They could be consecutive numbers (rare) but not the same. Since SDA's are sold as indivudual units they have the left speaker has it's own serial # as well as the right speaker.

The AI-1 cable you see has a transformer in-line to cope with the non-common ground issue.

The part I bolded in the quote above, I have no idea what you mean. If you can get a factory AI-1 from a member here for a decent price and you are dead set on trying to bridge a receiver that would be the best way. I still don't recommend it, because the payoff will be negligible, but we're always telling people to try things for themselves, so have at it if you must.

Give me a few minutes to locate my SDA bible and look up the one serial number you gave me. Please give me the other one. Is your current cable blade/blade on each end or pin/blade on each end?

My speakers are both pin/blade. Left speaker is 12003 and right is 11968. My receiver is set to 4ohm mode which is just a current limiter and I have the volume capped at -5dB. If I bridge them, I will still leave it in current limited mode.

SDA1C

Fair enough. I wasn't to say I dislike the bottom end just to say that with a receiver vs. pre/amp it seems to me the lower SQ isnt quite as good. My ohm readings were static. I understand it varies with frequency but as a general rule... Curious thing though as we're on the same general topic. When I first purchased mine they were 6.1 nominal. Actually I was a bit surprised a moment ago to read 4.0. Is this any point of concern? Not to derail just thought I'd throw it out as a bit more info for myself and the the op.

Whad u think of them m4's eh?...lol

1C

heiney9

SDA1C wrote: »

Fair enough. I wasnt to say I dislike the bottom end just to say that with a receiver vs. pre/amp it seems to me thre lower SQ isnt quite as good. My ohm reading were static. I understand it varies with frequency but as a general rule... curious thing though as were on the same point. when i first purchased mine they were 6.1 nominal. Actually I was a bit surprised a moment ago to read 4.0. Is this any point of concern? Not to derail just thought I'd throw it out as a bit more info for the op.

Whad u think of the m4's eh?...lol

1C

I agree separates will almost always give you a better presentation than a receiver, but there are some high end receivers that do a good job, too.

I can't say for sure as I've never taken those kind of measurements. Perhaps your x-overs are starting to show their age. Those electrolytic's weren't the best to begin with. That's why so many, including myself, have recapped the x-overs with modern film caps with stunning results.

I have a pair of modded M5's in my office/computer rig that sound absolutely fantastic............listening to them right now in fact. Monitor 4's are nice but a little small. They made a couple different versions over the years. They would be nice for surrounds too.

H9

FTGV

heiney9 wrote: »

... if they are 1C's they are 6 ohm nominal.

Thanks, so effectively each of the 4 amp sections will see 3 ohms.
The potential thermal issue is applicable to non SDA's as well.The lowered impedance (as seen by each section)means increased current demand (thus more current through the output devices) added to the >3 fold increase in output potential equates to alot of extra heat to be disipated.

SDA1C

Guess its time to consider the local ring/xover upgrade that is so highly spoke of here. Another point of interest might be the sub as its tuned to 20-24 htz. it'll make a set 301's sound like they have a pair lol (and thats saying something hehe). Sort of unfair to compare a radiator to a powered 15" in a 6cf enclosure.

My reference to the m4 was the link in the other thread. (about the Shengya) check em out. It's rather comical.

I still would hang the idea of eliminating the IC on the 1c. If for no other reason...it'll sound like s@#t. Others have certainly a more technical reason lol.

1C

treitz3

The technical reason is real simple. You lose the SDA.

heiney9

003 wrote: »

My speakers are both pin/blade. Left speaker is 12003 and right is 11968

I can't find my SDA bible known as the Compendium which has the info in it. I just moved and still don't have everything unpacked and in it's place. I'll keep looking but others have the same info, hopefully they will chime in.

H9

003

heiney9 wrote: »

I can't find my SDA bible known as the Compendium which has the info in it. I just moved and still don't have everything unpacked and in it's place. I'll keep looking but others have the same info, hopefully they will chime in.

H9

Thanks... please let me know if you find it! Seems like something like that should be uploaded to this site! :biggrin:

heiney9

003 wrote: »

Thanks... please let me know if you find it! Seems like something like that should be uploaded to this site! :biggrin:

It was an endeavor put together by our SDA guru Darqueknight. It's about a 90 page color/black and white publication about SDA's. A history, photo's, step by step upgrades, tweeter analysis, production runs with part numbers, etc. They are long sold out.

I'll find it here somewhere. It has a list of 1C and 2B serial numbers that can use the AI-1 cable.

H9

SDA1C

treitz3 wrote: »

The technical reason is real simple. You lose the SDA.

Since were being "technical" you done loose the array or the stereo you loose the dimension. just sayin lol

SDA1C

heiney9 wrote: »

It was an endeavor put together by our SDA guru Darqueknight. It's about a 90 page color/black and white publication about SDA's. A history, photo's, step by step upgrades, tweeter analysis, production runs with part numbers, etc. They are long sold out.

I'll find it here somewhere. It has a list of 1C and 2B serial numbers that can use the AI-1 cable.

H9

No chance of DK rerunning a printing session of said compendium is there? Guess I should be asking the source as it were.

heiney9

Nope, that question has been asked and answered atleast a dozen times.

H9

003

Can't someone that has a copy just scan the pages and upload it?