using both a and b speakers

[samuel r]

might sound silly, but does listening to two seperate sets of speakers, one set on "speaker a" and the other on "speaker b", at the same time ruin the amp or overwork it more? for example, on my denon 4800, i can choose to listen to a dedicated set of rears for music(a), and another set of rears for theater(. now if i have them (both a+ running simultaneously will that wear down or overwork the amp? it says on the manual that it may damage the amp. but with some manuals, i'm not sure if they could mean putting to speakers on one wire(linking). i had two seperate rears at one time(set a and set , but now i'm back to just one set(a) for music and movies.

[bensilb]

I am not sure if this will damage your amp, but you will not get the same power to both sets as if you only had one set on. For example, if your amp is 100w, you may only get 75w per set. I also have an old Sony receiver in my second room with speakers in the living room and kitchen. I quite often play them both at the same time. There seems to be no damage. There is a significant drop in sound quality when on set is turned off. I don't know if this will help.

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Sony Trinitron 27" TV

Yamaha RX-V1000

JVC HR-S3800 Super VHS VCR

Sony DVP-S530D DVD Player

Sony Tape

Sony CDP-CE345 Cd player

RF-3

RC-3

Synergy Rear surounds

[WMcD]

Samuel,

It is not a silly question. There are no silly questions. This is particularly so when the manual is unclear. My guarded answer is that you don't have much to worry about.

My understanding of your situation is that you have a concern about whether running multiple speakers off the amp at the same time is going to do any harm in the short run, or the long run. The amp manufacturer give some non-specific warnings.

Your question alludes to some setting on your amp about one set of rear for music and another for music. Yet it seems you can run them both by some switch settings. That is a bit of a puzzlement. Let us know more. Others on the bbs may be able to advise.

Amplifier manufacturers are probably not going to give you any advice about what is absolutely safe. They might have to honor a guarantee.

My understanding of modern consumer amplifier design is that they typically have two types of protection.

The first is an insantaneous current overload. This is when the user inadvertently, perhaps because of miswiring, shorts the output. The current protection circuit takes over and shuts things down before the output transistors get fried in a few milliseconds.

The second is a thermal cut out. In our hypothesis, if the two speakers are causing too much current, things heat up over a period of time, usually minutes or hours. A thermisor (temperature sensing device) recognizes that this is dangerous, and shuts things down.

As you can appreciate, these are circuits which are placed in the design of the amp to protect against two different situations. The first is analagous to "blow the fuse right now, we have a short" the the second is "overheating, working too hard."

If you haven't had a problem so far, it is probably safe to keep on doing it. Usually, rear speakers are not playing very loud and they're not a challenge to the design parameters of the amp.

The above is independant of whether it will sound "good". Designers are just trying to keep things protected.

I'll throw this up for discussion. Has anyone brought an amp to the shop after a melt down blamed on parallel speaker connection? I have not heard of such.

Samuel has a ligit concern which has intuitive merit. If the transistors are pulling more current, isn't the mean time to failure going to be lower? Sure. But is this a matter of minutes, days, weeks, months, years, decades?

My experience is the same as Mr. "bensib". We have some very old transistor amps which haven't conked out despite parallel connections and years of service.

Regards,

Gil

[boa12]

i studied the 4800 manual when i was shoppin for receivers, & i've seen many on here using A+B surronds w/ their denons.

the 4800 has hookups fot two sets of surrounds (A&. you can set either A, B, or A+B for each of the sound modes. f.e., you could preprogram A+B for a movie mode & use just B for 5 channel stereo(music).

though denon used that as an ideal - like A only for movie mode & B only for music, i thought they said it was a-ok to use A+B. that may tax the amp a lil more & like ben said it would split the power to each surround, but i don't think it would do any more harm to the amp than running A+B fronts on any receiver/amp.

it must have been talking 'bout hooking 2 speaks to the same terminals either in series &/or parallel (something dif than using the denon's electronics, or why would they make A+B available?).

------------------

Klipsch KLF 30 (front), KLF C-7, Cornwall I (rear)

Velodyne HGS-18 sub woofer

Monsterbass 400 sub interconnects & Monster CX-2 biwire & Z-12 cable

Marantz SR-8000 receiver

Sony DVP-C650D cd/dvd player

Sony Trinitron 27" stereo tv

Toshiba hi-fi stereo vcr

Technics dual cassette deck

Scientific Atlanta Explorer 2000 digital cable box

Boa's Listenin Lounge:

Klipsch RF-3 (front), RC-3, cheap little Technics (rear)

Monster MCX Biwires

Sony STR-DE935 a/v receiver

Kenwood KR-9600 AM/FM stereo receiver (vintage 1975)

Russound AB-2 receiver switch to RF-3

Teac PD-D1200 5-disk cd changer

Technics SL-1950 turntable/AT LS500 cartridge

Sega Genesis game player

Sub: None yet

rock on!

[shoemakc]

In most cases, the A + B terminals of most recievers are wired in parallel. Two 8 ohms speakers in parallel present a 4 ohm load to the amplifer. Most amps can drive a 4 ohm load at generaly does cause problems.

One of the mark of higher quality amps is that they can drive low impedance loads, 3.5...perhaps even 2 ohms. They need to be able to both provide the additional current necesary, as well as not exceed the ratings of any of their internal componants.

If they exceed their current driving ability, clipping occurs. If componants exceed their power ratings...POOF.

If you keep the volume relatively low, the amplifer should be able to provide the additional current, without breaking anything. Just don't push it.

-Chris

[maxg]

On my old Yamaha 595a you also had the option to connect 2 sets of speakers. THere was a warning in the manual however about the impedance. There was a switch on the back of the amp to select between impedance settings.

The instructions were something like:

1. Single set of mains - 8 ohm speakers. 2 sets of mains - 16 ohm speakers.

2. Single set of mains - 4 ohm speakers. 2 sets of mains - 8 ohm speakers

No idea if the Denon has a similar function. Seems doubling the speakers halves the impedance. I left the system on setting 2 for safety and never hada problem.

[DwK]

Wow.. keep posting guyz.

This is something I could know more about.

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Living Room:

Yamaha Natural Sound A-500 Stereo Amplifier

2 Klipsch Heresys on A switch

2 Fisher STV-873 on B switch

My Room:

Klipsch Pro Medias

2 Fisher Surrounds

[Steve Phillips]

Don't know if this will answer the question or not,but in my bedroom system I have my Heresy's on the B side and KSB 2.1's on the A side.More than once have I come home to find that my wife has had the Denon 2800 cranked for hours with A&B on in 5 channel stereo with the unit in a closed cabinet.No air supply at all and playing just fine.I have had no problems with any of my Denons in this area(knock on wood).I have my Denon POA-2800 amps in the living room running with a 4ohm load on one and and on with a 4ohm load on one channel and 2ohm loud on the other,not even warm.But they are made to drive 1ohm loads.

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Main HT:'77 Klipschorns w/ALKs,'75 Heresy center,modified with,K-Horn sqauwker & AA network.

KSP-S6 at sides 2 KSP-S6's rear.

Denon AVR-3801

2 Denon POA-2800 200X2

1 driving the Horns

1 driving the bi-wired Heresy center.

2 DIY 12"4ohm subs,Carver A500x 400 watts per ch.feed.

1 12" powered sub(behind the couch)feed from the surrounds pre-outs.

Sony DVP-C650D.Dish Echostar 4700 w/DD

JVC S7600U S-VHS

Pioneer CDL-D501 laser

Music in "Direct"only!

DH Labs T-14 speaker wire to the front 3.

Bed room HT:KSB 2.1 mains,SC-1,SS-1's,2 SW 8 II subs.

2 Heresy's for music.

Denon AVR-2800,Dishnetwork,Sony SLV-975HF VCR,Panasonic DVD-RV31.

[mace]

DwK,

My NAD manual (which I forgot I had and I've actually asked about this very question elsewhere on this board) states that if two sets of speakers are hooked (A and B channels) that the 4 ohm setting should be used. NAD also recommends if you aren't sure which ohm setting to use on the amp (4 or 8) that you should use the 4 ohm setting. They state that "in many 8 ohm loudspeakers the minimum impedance is from 4 to 6 ohms, and in 4 ohm speakers the minimum is typically 3 ohms. If you connec ttwo sets of speakers to the amplifier, their combined impedance is approximately half the impedance of either."

So, when in doubt, use the 4 ohm setting. You may sacrifice some power if the speakers are truly 8 ohm but you won't damage the amp. By setting the amp at 8 ohm and loading it up with speakers with mimimum impedance of 4-6 ohm (or two sets of 8 ohm speakers) you can potentially overheat and damage the amplifier.

As the old song from Kraftwerk goes... "Ohm sweet Ohm"

Mace

This message has been edited by mace on 07-03-2001 at 10:58 PM

[slfierbaugh@gmail.com]

I have the Kenwood KA-7100 Integrated Amplifier , specs below

Specifications

Power output: 60 watts per channel into 8Ω (stereo)

Frequency response: 0Hz to 100kHz

Total harmonic distortion: 0.02%

Damping factor: 50

Input sensitivity: 2.5mV (MM), 150mV (line)

Signal to noise ratio: 80dB (MM), 110dB (line)

Output: 150mV (line), 30mV (DIN)

Speaker load impedance: 4Ω to 16Ω

I have advent 4 0hm speakers on the B channel and 8 0hm Polk speakers on the A Channel.... Is there any Issues with playing A/B together?

Edited August 9, 2020 by slfierbaugh@gmail.com

[JohnA]

Wow!  You really drug up an ooold post.

 

My answer is it depends.  It depends on heat basically.  Lower impedance draws additional current from the amp at a given volume knob setting.  More current makes more heat.  Keep the volume reasonable and the heat will less than the amp's heat sinks can dissipate, protecting the output transistors.  Crank it hard and you'll let the magic blue smoke out. 

 

I had a KA-7100 with Kenwood KT-5300 tuner in college, driving Marantz Imperial 7 speakers.  I liked it.  Might like one again.