[JLM]

89 dB/w/m is not bad, but a lot of drivers to push around, crossovers to navigate, and fairly full range bass response to handle.  And of course it depends on one's musical preferences (genres and associated sound pressure levels) and room size.  Wattage (shear numbers) can only be a guide in audio. 

I have 90 dB/w/m single driver speakers with similar frequency range (F3 below 30 Hz).  I normally listen at less than 85 dB in a 2,000 cubic foot (8ft x 13ft x 21ft) room.  Being fascinated by Class T, I first tried driving them with a 7 wpc amp (8 dB of gain) to surprisingly good results.  But 40 watt solid state and tube amps with very robust power supplies (16 dB of gain) really woke them up.  And I now run 100 solid state (class D) watts again with beefy power supplies (20 dB of gain) to match the peak wattage ratings of the drivers. 

With the substantial power supplies normally associated with class A I'd guess it could take 50 - 100 wpc (maybe more) to properly drive the RM40s.  That's expensive (way past C&C guidelines), would make your electric meter spin, and generate significant amounts of heat.

Have you asked other RM40 owners if they have experience with class A?

[JohnR]

might be a bit underpowered for my VMPS RM40s.

Seriously? You could have stated that in your OP. You won't find a Class A amp to suit RM40s in the C&C category. Try Class D.

[mlundy57]

Seriously? You could have stated that in your OP. You won't find a Class A amp to suit RM40s in the C&C category. Try Class D.

I know it doesn't help the OP with his speakers but it started a discussion which led to information about the little amp camp amps I was unaware of that should work just fine with my 95db efficient speakers that don't see anything below 160Hz (160Hz and down are filtered out between the preamp and power amp.

I ordered a kit. Should be here by the end of the week. Be an interesting experiment.

Mike

[Folsom]

My amp has been preferred over the ACA several times, but even at 15w it's only enough for a smaller room with inefficient speakers.

I'm not sure why 5w wouldn't be entertaining with 95db speakers full range.

[Folsom]

Seriously? You could have stated that in your OP. You won't find a Class A amp to suit RM40s in the C&C category. Try Class D.

I would love to see right here a list of cheap and cheerful Class A amps. Ideally, non-kit offerings.

[G Georgopoulos]

Interesting discussion ,suppose you have a 100 watt class-a from that only 25watt is converted to sound if that's not enough to drive the spk,why not convert it to class-ab or class-d and get the full 100watt,the power supply the power transistors the heatsinks are all there,most engineers face this and guess what? the second option makes sense to them.

cheers 

[mlundy57]

My amp has been preferred over the ACA several times, but even at 15w it's only enough for a smaller room with inefficient speakers.

I'm not sure why 5w wouldn't be entertaining with 95db speakers full range.

One big reason for this build is getting a little experience before building out my Folsom amps (there's quite a bit more on your boards  ). 

I have also signed up for a "Build your own amp" class at the local tech college (no idea what the amp is going to be, only that the kit cost is ~$475).  Two reasons for taking the class (if it makes); (1) more experience soldering and deslodering and (2) someone to show me how to not electrocute myself and/or burn the house down.

I should be able to build the Amp Camp Amp form the instructions and video but trying to do so with the Folsom amp and Antipole seems to be akin to when I was a kid and thought I could learn karate from a book 

Mike

[ebag4]

One big reason for this build is getting a little experience before building out my Folsom amps (there's quite a bit more on your boards  ). 

I have also signed up for a "Build your own amp" class at the local tech college (no idea what the amp is going to be, only that the kit cost is ~$475).  Two reasons for taking the class (if it makes); (1) more experience soldering and deslodering and (2) someone to show me how to not electrocute myself and/or burn the house down.

I should be able to build the Amp Camp Amp form the instructions and video but trying to do so with the Folsom amp and Antipole seems to be akin to when I was a kid and thought I could learn karate from a book 

Mike

  You won't have any problem picking it up Mike, I have a feeling you will truly enjoy it.  Good luck!

Best,
Ed

[Stimpy]

Yamaha had a number of Class A A/B power amps, that should be cheap and cheerful.  They usually outputted somewhere around 10 watts Class A, before switching to A/B.  The more affordable models would be the M-45, M-65, & MX-600.

Also, plenty of single ended Class A 4/6/8/10 watt Chinese tube amps on ebay.  Many are simple integrated amps, but no reason that they couldn't be used with your preamp, for adding more inputs and volume control.

[Folsom]

Vintage class A receivers might be in the budget.

[OzarkTom]

My buddy Rex, who likes to try many amps is thinking about a set of these. Last month he bought a pair of Glow DIY speakers for $238 pr. and loves those. If I did DIY, I would buy a set also. Just think, Glow speakers and amp camp amps for $500.

The Glow speakers has no x-overs, so 5 watts would work great.

At 89db, these 5 watt amps will play your speakers loud enough to blow out your hearing.

[maty]

You need maths and a sonometer.

SPL (Sound pressure level) calculator

-> http://www.doctorproaudio.com/doctor/calculadores_en.htm#calc_spl

[JLM]

You need maths and a sonometer.

SPL (Sound pressure level) calculator

-> http://www.doctorproaudio.com/doctor/calculadores_en.htm#calc_spl

Enjoy playing with the calculator, but don't see anything to account for the room (size/surface materials).

[maty]

You can calculate the worst case.

I have a pair of KEF Q100 5.25" coaxial speakers. 86 dB SPL and 4.7 Ohms (min).

Worst case: 84 dB

* 84 dB, 80W, 2 speakers, random phase, 3m => 96.5dB

* 84 dB, 80W, 2 speakers, random phase, 10ft => 96.4dB

With these great vinyl rip

Karajan, Berliner Philharmoniker - Tchaikovsky - Symphony No. 6 (1972) (Vinyl) {24-96} [FLAC]

DR12      -1.60 dB   -20.21 dB     10:07 04-Finale (Adagio lamentoso - Andante)

95 dB peak, centered 2m, sounding too strong!

With current commercial music, we have maximum DR8 and much lower peaks, so that less power is required to reach the peaks of 95dB (peaks that are much closer to the average value and have a crash).

[Spanish] -> http://aficionados.foroactivo.com/t300-parallel-86-amplifier-con-chipamp-lm4780-mas-op-amp-lme49710-control-y-opa2277-dc-servo-disenado-por-tom-christiansen#15044

[Spanish] -> http://aficionados.foroactivo.com/t342-kef-q100-uni-q-bookshelf-speakers-5-25-coaxial-with-front-bass-reflex

[maty]

More useful links:

Locating areas of first reflections

-> http://www.acoustic.ua/forms/calculator4.en.html

Speaker Placement Calculators

-> http://noaudiophile.com/speakercalc/

Speaker Box Enclosure Designer / Calculator

-> http://www.diyaudioandvideo.com/Calculator/SpeakerBoxEnclosure/

[JohnR]

Until today I owned a pair of Q100s and I just don't see how it's possible to compare. You can in theory work out power from efficiency figures, but a speaker that is capable of handling power is going to get driven with a lot more of it. It's just the way it is. It's like putting a lawnmower engine into a racing car, in theory you can drive at the speed limit around town, but... why would you?

[maty]

KEF Q100 is just an example. With any other boxes must be entered sensitivity (removing 2dB to ensure, as it is usually more than measured).

The more important: with a good recording of an orchestral mass and great dynamic range (DR12), I had 95dB peaks and it is not supportable long time!


PD: the KEF Q100 sound very bad at first, they need a long burning (I assume it is because the rigidity of speaker suspension). And with my cheap tweaks the sound is much better.

-> https://www.amazon.com/KEF-Q100B-Bookshelf-Loudspeakers-Black/product-reviews/B0047K3X1M/ref=cm_cr_arp_d_viewopt_srt/163-6528262-9098548?ie=UTF8&showViewpoints=1&sortBy=recent&pageNumber=1

[JohnR]

I think I understand what you mean, but the experience is totally different. They are different classes of speaker. You don't sit in front of something like RM40s and listen quietly. That, at least, was the lasting impression I had from my audition. Anyway, I can't help feeling the OP's question would be better posed in the VMPS owners's circle.