Impedance Matching Loudspeaker Selector Switch

[haraldd]

Hello

I am considering to purchase a 4 way selector switch from Legend LE412 (C$40). It is can handle up to 150 watts RMS per channel and has an impedance matching circuitry with non-inductive 50 watt resistors with aluminum finned heat sinks.

I have a Sony MHC-GX450 with 2 speakers and a subwoofer. With 6 ohm loads, both channels driven from 120 - 10,000 Hz, rated 140 watts per channel minimum RMS power.

Question: will the switch allow me to connect that 3 piece speaker set with a second 2 piece speaker set (100 W peak power, 4 Ohm) that is in my infrared sauna and a third 2 piece floor speaker set (20 year old) rated at 45 watts and 4 ohm?

If I decide to get a newer pair of floor speakers should I look for one that is rated at 4, 6 or 8 ohm? Will the impedance matching switch handle speakers with different impedances and are there other drawbacks with connecting pairs of speakers that have different impedances to the switch? I do not need a volume control on the switch.

Thank you in advance.

haraldd

 

[j_garcia]

A speaker selector will usually tell you in their documentation (online?) what the minimum impedance you can use on all channels should be and what wattage and impedance capability of the receiver/amp you will need to effectively drive the resulting loads. If you want to be safe, I'd say use an external amp to power all the other speakers connected to the switch.

 

[haraldd]

Impedance Matching Loudspeaker Switch

Hi j_garcia

Thank you for your advice. I have not been able to find the specs you had mentioned on the internet. The only info I could find is here:
http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&rd=1&item=9717263107&ssPageName=STRK:MEWA:IT

I am not sure I understand your suggestion about using an external amp. I have no other external amp other than the Sony mini-component system mentioned. I was going to use that to power the switch that connects to the 3 pairs of loudspeakers: a 3-piece set 125W 6 ohm, a 2-piece set 70 W 8 ohm and a 2-piece set 70 W 4 ohm.

Cheers

Harald

 

[annunaki]

If that is a mini component system, it will not last very long running a 4 ohm load. I would say a couple minutes at best. The amplifiers in mini component systems are usually very cheaply made, only designed to run the inexpensive speakers they come with and no more. I would suggest a separate two channel amplifer capable of running a 4 ohm load for powering the additional speakers. The ever popular Behringer A500 comes to mind as a great solution.

 

[jcPanny]

Whole house system

I agree with the amp recommendation. Does the mini system have a line level stereo output?

 

[j_garcia]

The A500 can be found at Parts Express .com for ~$180.

 

[haraldd]

I do not have a line level stereo output, only a headphone jack and the terminals for the loudspeakers. I do have RCA input jacks and video in and output (for games).

Would it work if I wired a 2 ohm resistor in series with the 4 ohm speakers? The speaker then would appear to the receiver like a 6 ohm load isn't it? And if I added a toggle switch to the positive speaker wire I could then turn the modified 4 ohm sauna speakers on or off as needed. Please advise.

Cheers

Harald

 

[j_garcia]

I looked up your system, and I can pretty much guarantee you that it will not have enough power to do what you are trying to do. Impedance isn't the only factor; no matter what you make the impedance look like to the amp, you will still be drawing more current than that system will realistically be capable of delivering to multiple speakers, IMO.

 

[davee70]

Would it work if I wired a 2 ohm resistor in series with the 4 ohm speakers? The speaker then would appear to the receiver like a 6 ohm load isn't it? And if I added a toggle switch to the positive speaker wire I could then turn the modified 4 ohm sauna speakers on or off as needed.

I'd have to do the math but my experience with the Adcom GFS-3 speaker selector is that a noticeable degradation in sound quality can be heard when the speaker protection switch is engaged (which is just a resistor). You may not notice it depending on the quality of the remote speakers you're listening on but I would not want to use it on my main speakers.

 

[annunaki]

The only way you will be able to get a separate amplifier to work on the system would be to use a line output converter. They are usually used in the car audio world. Essentially, it converts a speaker level signal to RCA level (low voltage).

Ideally, in this situation one should replace the unit with a high quality stereo receiver with a pre-out. The HK3380 would work, as would a decent unit from Denon, perhaps a DRA-395.

 

[j_garcia]

There is a guy selling a nice Denon stereo integrated in the classified ads here. No remote though.

 

[haraldd]

The loudspeaker in the sauna is pretty basic: Pyramid 526DC. It is a double cone speaker 50W RMS per channel rated at 100 - 18,000Hz. I realize the sound will not be that great, but it is still better than listening to my mini system through a peekhole of the sauna door.

Based on what you all said maybe I should just forget about the third loudspeaker pair and wire the sauna speakers in series with a 2 ohm resistor and expect some degradation on these speakers (but hopefully not on the 3-piece Sony loudspeaker set?).

Following Annunaki's suggestion, could I use a line output converter to power the 2 way version of the Legend switch mentioned above? Could I play both speaker systems at the same time or better only one? Would that be connected to the Sony speaker terminals or the headphone jack?

If I replaced the sauna speakers, do you know of a reasonably priced 5" car type speaker system (needs to fit the opening in the sauna ceiling) that is powered? If there was such a system how would I connect it to the Sony mini component system?

Thanks for all your help.
haraldd

 

[jcPanny]

Sauna speakers

For the humidity and temp levels of a sauna, you weather resistant outdoor type speakers. Many of these include an inclosure and mounting bracket, but some will probably accomodate your ceiling mounting.

 

[haraldd]

Hi again

I have tried a number of things and ended with using my Yamaha YST-M20DSP powered stereo computer speakers (about 10 years old). The specs are: Output power: 10 W/ch (1 kHz, 4 ohm at 10% T.H.D, Input sensitivity 230mV, Input Impedance 25 kohm, Output Impedance 900 ohm, Output Level 0.6 V (at 230 mV Rated Input).

If I connect the headphone jack from my Sony Mini System to the input on the Yamaha speakers and connect the headphone jack on the Yamaha speakers to the inbuilt 4 ohm sauna speakers I get a decent sound but it is not very loud. The volume control on the Yamaha speakers is all the way up. If I increase the volume control on the Sony more than 50 % will that damage the Yamaha speakers?

If there is a chance of damaging the computer speakers I will install them inside the sauna. It is an infra red sauna and as such there is no humidity. Temperture goes up to about 53C (127F) for about 30 minutes. If the inbuilt car speakers can take that heat without a problem can I assume that shielded computer speakers would work in that environment?

Thank you for any suggestions you may have.

Harald