Marantz sr7012 flat bass

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This Prime Tower speaker was reviewed in 2015 and its impedance goes down to 3 ohms at around 120 Hz and that is rather low for an AVR.

IMO, to properly drive those speakers, external amplification would be required.

SVS Prime Tower and Center Loudspeaker Review

The SVS Prime Tower and Center loudspeakers offer compact size, yet perform with homage paid to SVS’s sub roots. Our review reveals wide sweet spot, brisk dynamics and extended bass at budget pricing.

www.audioholics.com

I read that review and made my observations on the impedance characteristic. However, you keep forgetting that it depends on other key factors such as the specific AVR model, distance, listening habits etc. It is not automatic that if you see impedance dip below 4 or even 3 ohms you would need external amps.

That being said, obviously one can't go wrong with using external amps whether it is needed or not, as long as the external amp is in fact more powerful than the AVR.

 

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Yes, I agree. Those speakers are 4ohm, but they at 3 ohm in the bass and at 200 Hz the phase angle is significantly negative.

In addition 3 db. at 30 Hz is stretching to the spec. If you look at the FR and take the customary datum between 500 and 1000 Hz, those speakers are at least 5 db. down at 30 Hz if not 6 db. In addition the turnover frequency is actually 65 Hz. So they are not deep bass speakers. With those numbers if the OP pushes any receiver hard into that load, he won't soon own it. He definitely needs an external amp for those speakers if he wants to drive them hard, or use a sub. I think at this time designers are expecting sub use with their speakers, and deigning for increased sensitivity and sacrificing low frequency extension, as you can't have both.

Those speakers are essentially below four ohm impedance until 350 Hz, so less than four ohms over most of the power band demand. So unless played at low volume, those speakers require a robust four ohm stable, amp and actually below that.

Take a look of the reality he presented in recent post:

Revisiting this again. Wonder if anyone has discovered over the last year why the Marantz SR7012 requires all this work to sound decent without a sub. No amount of tweaking without a sub can produce a nice dynamic sound. Not trying to rattle the house here. Just want to hear the bass at times. Maybe get the woofers to move a little air. See them move a bit, which is required to get any noticeable bass at a medium volume.

I am not saying an external amp can't help but is the SR7012 really the reason in this particular case? I really don't think so. As you alluded to, those speakers are at least 5 dB down at 30 Hz, you also said.. "turnover frequency is actually 65 Hz....So they are not deep bass speakers.." So I think your first post is probably right on but your second post is, not so much.

Either it is his room, or he expect too much from the prime towers, or may be a combination both. Forcing the situation with say, a powerful external amp may kill those speakers in the long run while before that he may be able to enjoy more, albeit distorted (over driven woofers that would let him see the pumping action lol..) bass.