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Old 29th January 2008, 07:48 AM   #1
rinx is offline rinx  Estonia
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Default Speaker vs. amp

Hej all!
Hows going?! Nice to be here back after a while...
Ok, lets go to the point. I am planning to do 2xDayton 8ohms parallel, so its gonna be together then 4ohms. But what i discovered is that my amp is for 8-16ohms (Marantz PM80). What are the options?!

Thanks for all opinions.
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Old 29th January 2008, 10:05 AM   #2
sfreak is offline sfreak  Australia
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You could always run the speakers in series, would amount to 16 ohm.

http://www.marantzphilips.nl/index.a...pe=Marantzpm80

I assume that is your amp, I cant find any detail on it, you sure it can't do 4 ohms? From what I am reading, the latter PM80s do 4ohm quite easily. Does it say 8-16 on the rear near the speaker terminals?
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Old 29th January 2008, 04:14 PM   #3
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Well, you could try and find some woofers that were 16 ohms each, then the total would be 8 ohms. Or you could use 4 ohms woofers and put the in series.

While I can't say with absolute certainty, it seems unlikely that any modern amp would not handle 4 ohm to 16 ohms TOTAL load per channel. Since most stereo amps of the type you have, have an A, B, and A+B speaker switching feature, it would be right to say 8 ohms was the minimum. Meaning, 8 ohms on the 'A' connector and 8 ohms on the 'B' connector for a TOTAL load of 4 ohms.

It's always annoying when amp manufacturers don't come right out and say this in plain English. But over all, it is very rare for any modern amp (meaning after the invention of the transistor) to not be able to support total speaker loads in the range of 4 ohms to 16 ohms. That is a virtual standard in the Hi-Fi industry.

Steve/Bluewizard
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Old 30th January 2008, 04:02 PM   #4
rinx is offline rinx  Estonia
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Well, I am sure I am going to use those Dayton Rs225 8ohms. They are pretty good.

Yes my amp shows 8-16 ohms.
But what happens when i use 4 ohms spekeakers with amp. Does it goes too hot and transistors can just burn out or what.


Ringo
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Old 30th January 2008, 04:03 PM   #5
rinx is offline rinx  Estonia
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You see it from here
http://members.home.nl/ll0ll/audio/p...t/IMG_0245.jpg
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Old 30th January 2008, 06:52 PM   #6
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How about a direct quote of what it says -

It seems to be --

Bi Wire Speaker System
System ????: ???~??? ohms
System A+B: ????? ohms
?? ?????


At any rate, Current is the problem. Two things affect current, low impedance and high signal levels. Either one of those can cause your amp to run out of current. Current causes heat, current causes the output voltage to drop; as long as your current demands are within reason your amp should handle it.

However, this brings up the very problem we all face, how low an impedance is too low, and how loud is too loud, and I don't think that is an answer we can give you with absolute certainty.

I still say any amp can handle the virtual standard load range of 4 ohms to 16 ohms TOTAL per channel impedance. But I have no way of proving it for your specific amp.

Steve/bluewizard
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Old 30th January 2008, 08:42 PM   #7
jnb is offline jnb  Australia
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If you have a reason to use two in parallel, do you have a reason to use 4 in series/parallel for 8 ohms?

BTW, 4 ohms will probably be OK, especially for normal listening levels, but if you abuse the amp the 4 ohms could damage it so be careful.
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Old 31st January 2008, 04:31 PM   #8
rinx is offline rinx  Estonia
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No, I cant use 4 serises/parallel. Its making boxes way too BIG.
So, but if I will put 2 series and get 16 ohms, thats kind a rare in soundarea. I have ever seenn 16 ohms speakers. Is that crazy idea?!
My amp need to work a lot harder to get the same soundpressure level?!
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Old 31st January 2008, 06:14 PM   #9
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Rinx,

Now you are getting to a very tricky part. First keep in mind that it only takes 1 watt to push your speakers to their rated sensitivity. Typically sensitivity rating are in the form 90db at 1 watt at 1 meter.

Two speakers in Parallel receive the same voltage, but the total current is divided between them. Two speakers in Series divide the total voltage, but they both get the same amount of current.

When you turn the Volume Control, you are not applying watts to the speaker, you are applying signal or voltage, and the resulting watts are what ever they are based on the load.

If you apply 16 volts signal to 8 ohms, the resulting power is

P = (E^2)/R
P = (16^2)/8
P = 256/8 = 32 watts

16v to 4 ohms

P = 256/4 = 64 watts

16v to 16 ohms

P = 256/16 = 16 watts

Notice that while each example above consumes a different amount of power, they all have the same signal voltage applied to them.

So power and perceived sound are not linear. One nudge upward of the volume control does not result in one nudge upward of the power.

When you turn your Volume Control up one very very small amount, just enough to hear a change in the sound level, that is about 3 db. Three DB represents a doubling of applied power.

So, in the above case, the perceived volume (what you actually hear) from an 8 ohm speaker relative to a 4 ohm speaker is one very tiny nudge of the Volume Control. A 16 ohm speaker relative to a 4 ohm speaker is two tiny nudges upward of the volume control. In either case, you are always going to be well within the normal turn of the Volume Control; that is, still in the normal listening range.

All that said, I still say your amp shouldn't have a problem with 4 ohms, but obviously, I can't actually promise that.

Another question, is this speaker design a known design that you are copying or basing your speakers on, or is this an original design created by you?

If it is a known design, and there are lots of them out there, then you should be able to get information on those designs and get some sense of the impedance response curve. This does sound like a fairly standard design.

Exactly what Dayton speakers are you looking at, and have you actually purchased them yet? It is possible that you might be able to find the equivalent Dayton in a 16 ohm version and that would solve your problems.

Still, in the end, the world is full of 4 ohm and 6 ohms speakers, I can't imagine that any good amp would have a problem with that.

One thing you could do, is when your cabinets are rough ready, temporarily install your woofers without the crossover, and listen to them in both parallel and series at modest volumes (25% to 30% turn of the Volume Control), and see if you hear a real difference in them.

It's a tough decision to make, but it is one that all speaker designers face.

Sorry, the was probably a lot of talking that adds up to not much help.

Steve/bluewizard
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Old 31st January 2008, 06:58 PM   #10
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Sorry, I just realized that you DID tell us the exact Dayton model number, but a quick search showed that that exact model Dayton woofer is available in 4 Ohms.

Dayton RS225-4 8" Reference Woofer 4 Ohm
http://www.partsexpress.com/pe/showd...number=295-376

For what it's worth.

Steve/bluewizard
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