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In Reply to: RE: 32 Ohm Drivers // 32 Ohm OPTs posted by maxhifi on November 28, 2014 at 12:00:31
Yes, there are three ways to wire them, and wiring them for 8ohms would be the common sense choice, but I want an answer to an esoteric question.
Jamie
Big speakers and little amps blew my mind!
Follow Ups:
If you use a 32 ohm speaker on a 16 ohm tap, it can reduce the power output from the amplifier to 25% of the rated value. If they are very efficient speakers, this may not matter. Also, if the speakers are connected in series, their impedances will have the potential to interact with each other and create anomalies in the frequency response, if they don't have exactly the same characteristics. (i.e. if one of the speakers has a higher resonant frequency than another)
"If you use a 32 ohm speaker on a 16 ohm tap, it can reduce the power output from the amplifier to 25% of the rated value."
Well that's not good. We certainly don't want that.
"Also, if the speakers are connected in series, their impedances will have the potential to interact with each other and create anomalies in the frequency response, if they don't have exactly the same characteristics. (i.e. if one of the speakers has a higher resonant frequency than another)"
Is this also true if you wire them series/parallel, so that the four 8ohm speakers present an 8ohm load?
To give a better answer to your first question. I was thinking that you would get more power with a 32ohm OPT. (I didn't think it would be as high as you said.) The power tube may see an easier load to drive at 32ohms. It also may extend tube life. I could be wrong on all these points.
Jamie
Big speakers and little amps blew my mind!
Well, first off, I made a mistake, it is actually going to reduce power to 50%, not 25%. (I was for some reason thinking we were halving the voltage rAnd it may be a little more than 50% since the higher impedance load may allow the amplifier to put out a slightly higher voltage, but it won't be significantly more than 50%, and you are certainly better off with a matched load. After all, if the amplifier would benefit from, say, a 5000 ohm output transformer instead of a 2500 ohm one (the consequence of using double rated load), then it surely would have been designed that way.Second, series parallel is better than just series, but not as good as just in parallel. Why?
Let's take four speakers, say the resonant frequencies are
1. 100 hz,
2. 105hz,
3. 101hz,
4. 103Hz.If you put them all in series, speaker 2 will see more voltage than the other three at 105Hz, because it has its impedance peak at 105 Hz. In series parallel, this peak would be in parallel with another speaker, damping this peak, but not eliminating it, meaning that the other three would see more voltage than in a pure series connection, but still not the same as speaker 2.
If you put them all in parallel (ideal), then all speakers will see the same voltage at all frequencies.
If all four speakers are really identical, of course this will be less of an issue, but putting speakers in series is definitely not an ideal practice.
I don't think I have written this in a very easy to follow way, but hopefully I have got my point across.
Edits: 11/28/14 11/28/14
The picture is what I will be wiring.
Your post was very informative if a little disheartning. How about this? What if you have attenuated the signal 24db before your driver hits it's resonant frequency? Would that make series/parallel more doable? I'm going to recheck the driver specs.
There are only two SET tube amps I know that can drive a two ohm load. And I am not wiring these as a 2ohm load, no way. Famous last words.
I will run four Decware SE84s on the mids. I will connect an EL84/6P15P directly to every driver if I have to. Yes, I mean four amps with 8 output tubes to 8 mid drivers. I'm not joking. $1600 for four amps, cheaper than most 300b amps.
Jamie
Big speakers and little amps blew my mind!
If you are not using the drivers anywhere near their resonant frequency, then it's a non-issue. They should match fairly well above this frequency, and any anomalies below the crossover frequency won't come into play.
And even if you are, it can work out if the drivers are well matched, it's more a case of something to be aware of than something to panic about. I certainly wouldn't bother getting four amplifiers to battle this issue, I was simply trying to illustrate why parallel is theoretically better than series or series parallel.
"I certainly wouldn't bother getting four amplifiers to battle this issue,"I would. I already have three of the four amps. LOL
Thanks for the posts, I learned some things I didn't know before.
When do you consider a signal to be in "electrical cutoff?" If there is such a thing. Phil Marchand says 12db down I think.
Jamie
Big speakers and little amps blew my mind!
Edits: 11/28/14
I'm not in the audio industry, I wouldn't challenge the opinion of a famous active crossover manufacturer.
My response was directed towards using the speakers full range, with resonance inside the pass band, in your case it really isn't very relevant. That said, if you have a bunch of amps you want to use, at least this way you will have four times the power of using one! This ought to be a very loud system when it's completed!
Fs of the driver is 400hz. See link below. I'm screwed. In fact, it's says the fequency response is 400hz to 4000hz. They are being used in these horns all the way down to 200hz with EQ. I was looking at 275hz to 350hz as crossover point. Putting the drivers in a compression chamber must lower the frequency response. I know it does that. The question is, does it also lower the Fs. I will have to post a question on the Redspade blog, to see about getting an answer.
"This ought to be a very loud system when it's completed!"
It's loud with one watt baby! No, four tubes at 1.8 watts per tube is 7.2 watts into a 102db efficient speaker. Not too crazy. ;)
Jamie
Big speakers and little amps blew my mind!
Far from screwed - go series parallel and if you want to be anally retentive about it measure the Fs of each driver and match them accordingly : say that A and B are in parallel, and C and D are in parallel, and AB are in series wirh CD. Match A to C as close as possible and C to D as close as posaible. With 8 drivers to work with you are sure to have success, and if one is way off just get another.My original point was just to give a reason why series connecting drivers is less theoretically perfect than a parallel or series parallel connection, but there have been many successful speakers with series connected drivers (heck the Bose 901 has nine !) so it's far from an insurmountable problem
Edits: 11/28/14
His supposed lack of knowledge is on occasion belied by his direct and inquisitive line of questioning. He doesn't seem to have any knowledge or direct experience with the circuits you were inquiring about unless it suits him so take everything with a grain of salt. Please see the related posts on HiEff Forum.
Edits: 11/28/14
"His supposed lack of knowledge is on occasion belied by his direct and inquisitive line of questioning. He doesn't seem to have any knowledge or direct experience with the circuits you were inquiring about unless it suits him so take everything with a grain of salt. Please see the related posts on HiEff Forum."
That's not a very nice thing to say.
Max was a part of the first thread you reference, and in fact I mentioned him and his post by name, because I said I was giving "the other side of the coin" from his post. I assume he read the rest of that thread, but I may be wrong.
"He doesn't seem to have any knowledge or direct experience with the circuits"
I am self taught, and people who are self taught have huge gaps in their knowledge base. I didn't start learning high-end or electronics till later in life, when you have a lot of competition for your free time. I apologize to the learned people here for asking newbie questions. I know just enough to be dangerous, and I have the imagination to turn that into very dangerous.
The sad fact is, I know there are a lot of very knowledgable people reading this who I bet have an opinion about running a SET amp with a 32ohm OPT, but they will never post it, because of people like you.
That's a crying shame.
"take everything with a grain of salt."
To be sure!!!
Mr. James Steady
Big speakers and little amps blew my mind!
If I had 32 ohm speakers or if I was trying to take advantage of that transformer's ratio to load an odd tube I would use it.
Otherwise your posts sound like a troll. You try to re-word the same statement (not question) in order to advance your theory. Troll-like behavior. If that's not the case and you are just trying to get info then ask questions and enjoy the answers you get.
The sad fact is that you have received opinions from some knowledgeable people here (I'm not counting myself in that group)and give the impression that you know differently. Good luck with that.
"you have received opinions from some knowledgeable people here ... and give the impression that you know differently."
That's become a common theme on the DIY forum as well. Many good people have left as a result of the confrontations it causes.
--------------------------
Buy Chinese. Bury freedom.
Kingdom of the Triodes,
""you have received opinions from some knowledgeable people here ... and give the impression that you know differently."
That's become a common theme on the DIY forum as well. Many good people have left as a result of the confrontations it causes.""
I don't think our friendly banter about the Chinese has ever risen to confrontation. I don't see the problem.
I did write a diatribe, but that is because some people say things very glibly, that I take deadly seriously, because I actually have had someone try to destroy me. A couple of times I've had punk 18 yr old white kids say, "I'll shoot you in the face motherf@#$er!" They don't know how close they come...
Chip seemed to think it was okay.
Jamie
Big speakers and little amps blew my mind!
Kyle,
Here is another fairly simple question for you. You said I reword things to make a point, but let us consider this the Socratic Method.
If you had a free built to spec 2a3 SET amp, and a free built to spec paper wide range driver. What impedence would you choose?
I would choose 16ohm into 16ohm. If you ask me to justify that I could give you my reasons, but I'm not saying I could quote chapter and verse out of an engineering manual. I tell you my choice up front, so you don't think I'm BSing you.
Big speakers and little amps blew my mind!
I get it. You think I started this thread to win an argument on the HE forum? You think I'm stupid?
This is the subject that has been on my mind. I could care less about Tannoy Reds and 16ohm wide range drivers. I was trying to help the OP of that thread, which I guess I failed at.
Big speakers and little amps blew my mind!
"If I had 32 ohm speakers or if I was trying to take advantage of that transformer's ratio to load an odd tube I would use it."
Oh, that's a simple answer to a fairly simple question. Which is what I was looking for.
Thanks.
Big speakers and little amps blew my mind!
"The sad fact is that you have received opinions from some knowledgeable people here (I'm not counting myself in that group)and give the impression that you know differently. Good luck with that."
This is a public forum right? I certainly do have my opinions about things. Just because someone is an engineer, doesn't mean they have better taste than me. Then again they might, and be an EE. That would be cool. I appreciate every response I've gotten to all of my posts. I very much appreciate Max for killing a day explaining wiring to me. I hope I use some of his information in my project. I know I will. I hope his project goes well.
The sad fact is, that I've had eight years of reading this forum and not responding to anything bottled up inside me, and now I joined, and I'm afraid I'm going to spew out all the crazy, esoteric, minutae that I've always wanted to know about, but was too afraid to ask. That's a literary reference.
When I spew it, the floor may get messy. You may want to watch your shoes.
I really intend to just ignore trolls, but since you are my first, I thought I'd give a little explanation.
Mr. Steady
Big speakers and little amps blew my mind!
See, I had thought this before.
These drivers were a group buy direct from the factory. If Paul Spencer had specified 32ohm drivers then paralleling them would have brought them to 8ohms, and everybody would be home free.
Dammit.
Jamie
Big speakers and little amps blew my mind!
Max,
I hate to keep bothering you. Just sign off when you want to.
I'll read up on how to measure the Fs of a driver. I have 12 and only require 8. The instructions you gave on matching is priceless to me. Thank you. That is, if I want to be anal rententive, which I never am.
Really you've got the wheels turning on how to go parallel. Like breaking up the quad into two pairs run parallel, that is, two pair at 4ohms each. Then you could use a 2a3 amp on the 4ohm tap to run the quad of two pairs. One amp per horn. Getting way way back to the origins of this thread, I don't think running a 2a3 on the 4ohm tap is a good idea for various reasons, but options are always limited.
The Decware SE84 strapped mono can give about 4 watts into a 1 ohm load, and drive the hell out of it.
Max, thanks for helping me see my options more clearly.
Jamie
Big speakers and little amps blew my mind!
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