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Need advices to connect new speakers with old Sony CMT HX70-BTR amp

cocoggu

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Hello there,
I own a 2008 Sony CMT HX70-BTR (specs amp & speakers) and although I love this hi-fi system (don't hate me for that please), I slightly damaged the woofers by pushing the volume a little too high.

I fixed it with some glue, but I doubt my poor repair skills will be enough in the long term. So I'm looking for replacement speakers as a first step, before updating the amp as well.
Although I really loved the warm sound of these speakers, I understand that they could be easily outmatched by other references. Besides the audio quality, I'm looking for a boost in loudness, at least once the amp has been updated as well.

As a newbie to the hi-fi world, I have several questions :
  1. First, about my old CMT HX70-BTR, the specs in my links above are quite sketchy and nothing is specified for the speakers sensitivity /1W/1m.
    I don't have the tools to measure it myself, but I'm wondering if the size of the woofer (13cm), and the material used (glass fiber) can give a rough idea of the maximal sensitivity reachable physically. I assume (perhaps wrongly) that a 17cm woofer made of the same material, will, per nature, have a higher sensitivity. Is it possible for a woofer this size to reach a 89-90dB sensitivity?
  2. Still about my old amp, it is specified in the second link above, that it has a 50 Watts power consumption. Is it possible for it to then deliver 2x 75W to the speakers? Is it made possible thanks to the 4 ohms impedance? I'm asking to make sure the 2x 75W is genuine, and not pure marketing.
  3. If I replace my 4 ohms speakers with 8 ohms speakers, does it means that only half of the power will be transmitted to the speakers? With the same sensitivity and the same volume, does it means half the loudness? If the new 8 ohms speakers have +3dB in sensitivity, will they produce approximately the same loudness with the same volume?
  4. I was interested in the Focal Aria 906, but they're 8 ohms with a sensitivity of 89.5dB. Should I prefer the Elipson Prestige 2i which are 4 ohms with a sensitivity of 91dB and a max power intake of 100W? Loudness is important to me, and the Elipson looks greater in that domain while also being cheaper, and I assume, looking at the brand reputation, that quality can only be better than the one of my original speakers.
  5. Can the speakers I linked in my previous point damage my amp because of the high recommended power when it compares to my amp output ([email protected] 8 ohms for the Focal, so I guess 60W @4? & 100W @ 4 ohms for the Elipson)

Stopping there for now, sorry for the lengthy message, I just to make sure the new speakers check all the boxes, and also I'm quite curious on how it works.

Thanks to anyone who will have the courage to answer me :)
 

AnalogSteph

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1. You can typically expect about 84-87 dB / W / m from 5" class speakers, and somewhere around 87 dB for the 6.5" class. There is a tradeoff between driver fundamental resonance (fs) and sensitivity, so basically the deeper they'll play the less sensitive they are. For example, Purifi make a 6.5" 8 ohm midwoofer that can play super low (fs = 31 Hz) but barely makes it to 86.8 dB / 2.83 V / m, while the midrange-focus version is substantially more efficient (fs = 57 Hz, 91 dB / 2.83 V / m). You can also buy 8" PA midwoofers that barely make it into the bass (fs = 90 Hz) but will get to 94 dB / W / m in the midrange.

2. Rated power consumption is not measured at full rated power output. This system seems to deliver an honest 2x 60 W into 4 ohms. That's a decent amount of power.

3. There would be a difference of 3 dB between an ideal 4 ohm and 8 ohm speaker with the same voltage input (which is indeed half the power but only somewhat lower subjective loudness). That being said, lots of speakers claim to be "8 ohms" but actually aren't. The Aria 906 for one has a minimum impedance of 4.5 ohms, so barely even qualifies as a nominal 6 ohm speaker (for a nominal N ohm speaker, impedance minima must not be lower than 80%N).

4. Sensitivity is one area where manufacturers can be quite... optimistic. Do not trust manufacturer specs, trust credible measurements. (Of which I could not find any for the Elipson.) 91 dB / 2.83 V / m is not entirely unrealistic for a genuine 4 ohm speaker though, it would be 88 dB / W / m.
If you need to be playing loud, I might be looking for something a little bigger than a 6.5" class bookshelf, although I would expect even those to be an improvement over your existing bread and butter 5"/1" speakers. Maybe something 8", or a 2x 6.5" 2.5-way floorstander. Or if you want loud, you would probably be surprised by the racket some decent 12"/15" PA speakers can make (but choose carefully, as cheap ones in particular may sound quite terrible).

5. No. For the Focals, recommended amplifier power is 25-120 W, and yours would be right in the middle of that range.

Given your speaker choices, I take it you're in France or thereabouts?
 
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cocoggu

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Thanks so much for all the explanations @AnalogSteph, it's really helpful ! Indeed, I'm french and living there :)
However, I don't have particular ties with french manufacturers, and I even found this Klipsch RP 160M pair that I found really interesting.

I'm not sure how they reach such a high sensitivity (96dB @ 8 ohms) with 6.5" woofers, but high sensitivity seems to be their trademark, and I haven't found anyone online denying it. Would you recommend this pair to me?

Based on the assumption that my original Sony speakers have a sensitivity of 87dB/W/m, when reaching 60-64W of power input into 4 ohms, it should have a theoretical loudness of ~105dB (I understand it's not a perfect science, and that it really depends on which part of the frequency spectrum we are looking at). For the Elipson at 91dB/W/m, with 60-64W of power into 4 ohms we get 109dB which would be more than double the loudness I currently have. I believe it would be more than enough for my use case. Same apply to the Klipsch which produces 110dB with 32W @ 8 ohms (I assume 32W is my amp max power output per channel @ 8 ohms).
Now, I definitely understood that manufacturers specs are often far from reality, but since I haven't found any independent measurements, that's all I can rely on for now.

Do I get it, or am I totally off the mark?

Thanks again!
 

AnalogSteph

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I'm not sure how they reach such a high sensitivity (96dB @ 8 ohms) with 6.5" woofers, but high sensitivity seems to be their trademark, and I haven't found anyone online denying it.
Klipsch sensitivity specs are routinely off by about +6 dB due to nonstandard measurement conditions. Take them with a massive grain of salt. Their stuff can be more sensitive than average, but that means a somewhat reduced low end, i.e. a sound tending towards bright. No free lunches to be had here.

An improvement of (realistically) +4 dB is by no means double the loudness. That would take about 8-10 dB on average. Combined with better resistance to damage at high levels, it would be a good start though.

But I'll say it again, 6.5" bookshelves generally still aren't the kind of thing you buy for party levels. Except for ones using the large excursion Purifi woofers perhaps, but then you'd want a bit more amplifier power than 60 watts (like 200-250 W). Playing loud either requires membrane area or high excursion with amplifier power, no way around it.
 
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