ohm's issue

[Tylerb]

Hope I'm in the right forum as this is my first thread.

I'm putting together a sound system for my backyard. I have 4 Proficient AW650's and 2 impedance matching volume controllers. The speakers are 89db and 4 ohm rating. I'm obviously splitting the 2 pairs of speakers for 2 different listening areas. I purchased a cheap Sherwood amp to drive the speakers and that was my first mistake. ( other than buying 4 ohm speakers). It would play fine for a while and then shut off. The protection feature kicked in.

I had no idea how drastic a difference a 4ohm load put on an amp. The Sherwood is an 8 ohm model. I've since returned the Sherwood and purchased an Onkyo TX-8255. The salesman told me it was 8 ohm switchable to 6 ohm and would be fine if used with impedance matching volume controls. These speakers aren't going to be blaring and all 4 will rarely be on together. I guess I'm just looking for feedback on what I might expect from this set-up with this better amp. It's at the top of my budget.

I can even set the maximum volume level on the Onkyo to keep people from getting careless. If anyone knows what the safest impedance setting is that would be great. I'm coming up with 4. Thank you and sorry for such a long thread.

[Tylerb]

I meant to say Onkyo TX-8555, the next step up from the TX-8255.

[Nelson Pass]

Since you have two pair, perhaps you should consider running the speakers
in series to make 8 ohms instead of parallel making 2 ohms.

[EWorkshop1708]

Series sounds better too, less load, less distortion.

[Tylerb]

I'm not sure if I explained my installation properly. Channel A- L&R goes to impedance matched volume controller and then on to each speaker individually. (parallel? ) Channel B does the same. I had to perform minor miracles to get the wire to some of these speakers neatly. Any significant redo isn't happening.

I'm still thinking using Onkyo's volume limiter could be a useful tool. Find a reasonable volume and that's it. I'm almost positive my volume controllers should be set at 4x. I could try 8x and see if I get enough volume. That's safer for the amp. My last thought is a fan. Walmart has these neat 5" personal fans that are square and pivot to lay flat. I could plug it into the switched outlet and I presume draw hot air out or blow cool air in. That couldn't hurt.

I'm installing the amp on Thursday and I'll check in with results. Thanks again.

[AndrewT]

Fit two stereo amplifiers, each capable of driving a 4ohm speaker load.
Don't parallel your speakers.

[Original Burnedfingers]

I don't suggest using this setup at all unless the impedance matching controls are set to a 2 ohm load (that would be the three pair setting on the jumper pins). Impedance controls at least the good ones have the capability to run 1pr,2pr,3pr, or 4 pr of speakers. The three pair setting should provide a working environment. One pair being 8ohm, two pair =4ohm, and three pair = 2ohms.

This would work except for the fact that the impedance will change. Unfortunately unless you happen to have an impedance meter on hand you cannot be assured the impedance of the speaker since it will vary with frequency. I believe that you will find that the impedance will be half or less of the nominal impedance when low frequencies are present.

The correct and only way to make things live would be to read what Mr. Pass has to say.

Quote:
Since you have two pair, perhaps you should consider running the speakers
in series to make 8 ohms instead of parallel making 2 ohms.


This is an excellent answer here. Put two speakers in series for each channel. Set the control at 1X. The amplifier then sees a load it is more comfortable with. ..+ ..--...+...--

Unfortunately your choice of gear isn't very stout and when you mention having to consider fans to cool I start shaking my head.

Put them in series.

[Tylerb]

Originally Posted by 6BG6GA

I don't suggest using this setup at all unless the impedance matching controls are set to a 2 ohm load (that would be the three pair setting on the jumper pins). Impedance controls at least the good ones have the capability to run 1pr,2pr,3pr, or 4 pr of speakers. The three pair setting should provide a working environment. One pair being 8ohm, two pair =4ohm, and three pair = 2ohms.

This would work except for the fact that the impedance will change. Unfortunately unless you happen to have an impedance meter on hand you cannot be assured the impedance of the speaker since it will vary with frequency. I believe that you will find that the impedance will be half or less of the nominal impedance when low frequencies are present.

The correct and only way to make things live would be to read what Mr. Pass has to say.

Quote:
Since you have two pair, perhaps you should consider running the speakers
in series to make 8 ohms instead of parallel making 2 ohms.


This is an excellent answer here. Put two speakers in series for each channel. Set the control at 1X. The amplifier then sees a load it is more comfortable with. ..+ ..--...+...--

Unfortunately your choice of gear isn't very stout and when you mention having to consider fans to cool I start shaking my head.

Put them in series.

I'm going to have to find my speaker boxes. 90% of the sources list the Proficient AW-650's as an 8 ohm speaker. However the most important source, the website lists them as 4 OHMs. So be it. The acid test will be tomorrow. The Onkyo is no dog, so I may raise the setting to 8x and see what my volume response and overall sound is like. As I said the fan was a no cost help to cool the amp. I thought heat was part of the issue with the amp driving the 4 ohm speaker. Otherwise it goes on my desk.

I don't doubt anything you guys are telling me. Unfortunately I didn't research this enough so now I'm working in reverse. The Bottom line will be the Onkyo's performance. All 4 speakers will rarely be on. But I realize you have to treat the installation as if they will be. I'm usually more tech savvy than this, it has me nuts. Thanks

[EWorkshop1708]

Dude run them in series! You don't have to be "Tech" savvy just to wire speakers in series.

ALL my speakers are 4 ohm, run two speakers in series it is like 1 speaker to the amp.

Positive from amplifier on positive of first speaker
Negative from amplifier on negative of second speaker
Connect negative of first speaker to positive of second speaker.

It's EASY.

[Original Burnedfingers]

Quote:
I'm going to have to find my speaker boxes. 90% of the sources list the Proficient AW-650's as an 8 ohm speaker.

However the most important source, the website lists them as 4 OHMs. So be it.

I think your missing what I am telling you here. A speaker manufacturer can and does list a speaker as 8 ohm for example if it generally runs in that impedance. The impedance does change when there is low frequency signal as it will go down most generally it will be around 4 ohms or lower. By the same token the impedance rises when frequency rises. Therefore when setting up ANY system one must look at the lowest or worst case scenario.

My suggestion would be this....take a speaker to your nearest Hi Fi stereo shop and ask them to do an impedance test on the speaker at say 100hz,330hz,1k,5k,10k,20k and write down the readings. Look at the lowest impedance reading and then set up your system to handle the worst case impedance or follow the advice given about putting your speakers in series.