Hi All,


I really need some help. I have currently ceiling speaker Bose FreeSpace DS 40F, that I want to connect to amplifier HK AVR70 (specification below).

Each speaker is connected directly with the cable to amplifier, on each speaker transformer is set on 8 Ω variant. Here are my questions:

  1. Is it safe to connect these speaker to this amplifier? (Does it have enough power?)
  2. Should I use transformer as 8 Ω on the speakers or can I use 100W.
  3. Can I use amplifier Onkyo TX-NR686 to connect these speakers? (Is this safe?)


Bose FreeSpace DS 40F:

Frequency Response (+/-3 dB)   80 Hz - 17 kHz

Frequency Range (-10 dB) 70 Hz - 19 kHz

Recommended High-Pass Filter 70 Hz high-pass filter

Loudspeaker EQ Recommended

Overload Protection    PTC/Resistor

Long-Term Power Handling 40 W (160 W peak)

Sensitivity (SPL / 1 W @ 1 m) 87 dB SPL

Maximum SPL @ 1 m 103 dB SPL (109 dB SPL peak)

Nominal Impedance    8 Ω (transformer bypassed)

Transformer Taps (70/100 V)   70 V: 2.5 W, 5 W, 10 W, 20 W, 40 W 100 V: 5 W, 10 W, 20 W, 40


Amplifier Harman Kardon AVR70:

Multichannel power: 75W per channel, two channels driven @ 6 ohms, 20Hz – 20kHz, <0.1% THD; 100W per channel, two channels driven @ 6 ohms, 1kHz, <1% THD

Input sensitivity/impedance: 200mV/47k ohm

Frequency response: 10Hz – 100kHz

High instantaneous-current capability (HCC):  ±25 amps


Please help!

Original Post

Hello MiniJack,

Thank you for reaching out to us.

How many DS40 F do you need to connect.
If on each channel, 1 loudspeaker, you are fine.

If you need to connect multiple loudspeakers to an output channel, then the impedance (speakers in parallel) and the output power will be to low for the amplifier.

Because it is a low impedance amplifier you should indeed tap the DS40 F to 8 ohm and connect it to the 8 ohm terminal.

I hope this helps you with your system, otherwise do not hasitate to contact us.




Thank you very much for your replay Arno. I am connecting 1 speaker to each channel (in to total 5 speakers to 5 channels).

I noticed, that I need to use around 75-80% of volume if I want to have some "more sound", is this mean that this amplifier has not enough power for these speakers?

I have 1 additional speaker so in total 6, that is why I am thinking of buying new amplifier to be able to connect all 6 of them. Could you tell me, if this amp, will be ok with 6 of Bose speakers, all of them connected separately to the individual channels:


  • Supports 5.2.2-channel Dolby Atmos® and DTS:X® playback
  • 165 W per channel
  • HDMI® 7 in (1 front*1) / Main Out, and Sub Out*2 supporting 4K/60 Hz, HDR10, HLG, Dolby Vision™, BT.2020, and HDCP 2.2 pass-through
  • Dynamic Audio Amplification with 4-ohm speaker-driving capability
  • 384 kHz/32-bit DAC and VLSC™ filtering for superior clarity


  • 165 W/Ch (6 Ω, 1 kHz, 1% THD, 1 Channel Driven, IEC)
  • Dynamic Audio Amplification delivers thrilling multichannel and stereo performance
  • High-current power drives large speakers with 4-ohm resistance
  • H.C.P.S. (High Current Power Supply) customized transformer
  • VLSC (Vector Linear Shaping Circuitry) high-frequency noise removal (for front L/R channels)
  • Non-phase-shift amplification circuitry for clarity and detail
  • Discrete output stage circuitry for low distortion


For the Harman Kardon AVR70 is not specified how the power is measured, like RMS or peak power.
So it could be that it can deliver not enough power.

If you use a "surround" amplifier, you probably only get signal on the L and R channel, unless the content includes multiple channels.


Hi MiniJack,

As said, I do not know if it will send audio to all channels. Probably it will depends on the content. Or there is some kind of setting you can send L / R to all channels. Please check with Onkyo.

They indicate 165 W/CH (one channel driven).
I do not know what the power will be if all channels are driven.

But 165 W would be more than enough!!


Hi Tony,

In general, you'll want to look at the amplifier's output power rating. These speakers will operate in low impedance (8 ohm) mode if wired correctly to the 8 ohm (+) and common (-) terminals on the DS40, and the speaker tap must be set to 8 ohm (on the front). Do you have no sound at all? What amp are you using? 



Add Reply

Likes (0)
Having trouble signing in?

We recently updated our sign-in procedure and if you have old sign-in data cached, this can create a problem. Please:

  1. Clear your browser cache and cookies
  2. Then close the browser (not just the window)
  3. Open the browser and try again
Thank you

Please make sure that your profile is up to date