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Onkyo SR701 - Bass Below 250 Hz

 

New member
Username: Chris_d

Post Number: 1
Registered: 01-2004
I have a question about bass on my new Onkyo SR701 home theater receiver compared to older stereo receivers such as my existing receiver (JVC RX-309TN, 2 channels, 100W / channel, ~ 10 years old), but first I wanted to thank all of the people who post on ecoustics.com. I have just purchased some home theater equipment and your posts helped me choose the equipment I choose to purchase.

I hooked my new Onkyo receiver up to my CD player and my two existing speakers (Fisher ST-515, 15" woofer, 3 way, 120 W, ~10 years old). I configured the receiver to match my existing setup by selecting Front L/R as the only speakers that I have and that they are "Large" speakers. The manual (available at the Onkyo website http://home.houston.rr.com/dillweb/onkyo/figure1.gif).

I also tested the crossover that is in the speaker configuration menu to make sure this was not what I was experiencing. I setup the Onkyo receiver in four ways. The first way was with the front speakers set to "Large", no SW. The second way was with the front speakers set to "Small", with a SW (necessary to set the front speakers to "Small", but no SW was connected to my system), and a crossover of 40 Hz. The third way was identical to the second, but with a crossover of 100 Hz. The fourth way was identical to the second, but with a crossover of 150 Hz. I compared the last three ways to the first way as a baseline. I could easily see the effect of the different crossover points in Figure 2 (http://home.houston.rr.com/dillweb/onkyo/figure2.gif). The important item to note is that there was no difference above the crossover point between the "Large" setting and "Small" setting with a crossover point. The bass was still missing.

The manual also states on page 78 that tone control is at 50 Hz adjustable by +/- 10 dB. I plotted the difference between the Onkyo and the JVC in Figure 3 (http://home.houston.rr.com/dillweb/onkyo/figure3.gif ). I noticed on the plot that at 50 Hz the difference was about 10 dB. I adjusted the bass setting on the Onkyo receiver to +10 dB. This audio adjustment is available in the "Stereo" mode, but it is not available in the "Direct" or "Pure Audio" modes. The result is also shown on Figure 3. Increasing the bass setting to +10dB gave me a flat response! This means that the amplifier is perfectly capable of driving my large speakers. This is the way the receiver should perform. There is no reason why I should have to adjust the bass setting because the signal coming out of the amplifier is wrong. This also means that the "Direct" and "Pure Audio" modes will not have the correct amount of bass, as they do not allow audio adjustments. Perhaps something is not wired correctly in the receiver.

Everything in the manual leads me to believe that low frequency sounds are designed to be sent to the "Large" speakers. There is even a setting to enable the low frequencies to go to both the subwoofer and the large speakers when a subwoofer is connected. The feature is called "Double Bass." It is described in the manual on page 57. The manual seems to be consistent in that the low frequency part of a signal is intended to be sent to speakers that are designated as "Large."

I called the Onkyo support line and explained the situation. The support person basically said this behavior is by design. He said that home theater receivers are designed to be connected to a 5.1 speaker system. He said that home theater will not work well with big tower speakers in this regard. He said the amplifier was not designed for tower speakers like the amplifiers on stereo receivers were. The impression that I got was that he did not fully understand what I was experiencing. I think I can understand what he was trying to explain. I understand about the crossover for the subwoofer and how 5.1 speaker systems are designed to work. What I understand and the manual states again is for the small satellite and subwoofer setup is that the bass below the crossover point goes to the subwoofer and the high frequencies go to the small speakers. The manual also states that if you select "Large" for the speaker type that all frequencies go to those speakers. Furthermore, the crossover point I am seeing in Figure 2 is more in the 250 Hz area, not in the 40 Hz to 150 Hz user selectable crossover points that the receiver allows to be selected. The stated frequency response on the Onkyo website and user manual for the SR-701 amplifier is 10 Hz to 100 kHz +1 dB/-3 dB (http://www.onkyousa.com/model.cfm?m=TX-SR701&p=s&class=Receiver).

Since, I did not get the help I was looking for on the phone, I sent an email describing the problem to Onkyo. It has been 5 days and there has been no response.

In summary, there seems to be a drop off in bass below 250 Hz on my Onkyo SR-701 receiver compared to my older receiver. The setting of "Small" versus "Large" speaker seems to have no effect with respect to this problem, i.e. the missing bass is not sent to the speakers in the range between the crossover point and 250 Hz. The difference at 50 Hz is about 10 dB. The 10 dB amount is the same as is stated in the manual is the lower limit of what can be adjusted by the tone control. Adjusting this bass tone control setting up by +10 dB seems to make the response flat. I think there is something wrong with my receiver. I think this problem would be masked somewhat in a 5.1 speaker system setup so it might not be noticed by most people, but I still believe the receiver is not meeting its specifications.

My question is whether anyone else has noticed this behavior in this or other home theater receivers before or is something wrong with my receiver? To me, regardless of what the person on the support line at Onkyo said, it seems totally unreasonable for a receiver that costs $800 USD to not have a frequency response in the 20 Hz to 20 kHz range of +/- 2 dB. I took the receiver back and exchanged it for another SR701 and the same problem exists on the new one. I don't know if this behavior is by design or if I have just gotten a bad batch. I am now considering a Denon AVR-2803.

Thanks,
 

Anonymous
 
Chris:
You're really an engineer. I like what you wrote and I appreciate your findings. I was looking to buy the SR701 as well. After reading your comment, I am turning to other rx. Have you tried HK 525? It is about the same price range but lower power than 701?
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