Bottlehead for deaf loudspeakers

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Phippers

New member
Hi,

So, I'm enjoying my new Mainline, listening to it as I write this (Based on a True Story by Fat Freddy's Drop) .... and I really really enjoyed the build.

So I wanted to get some advice on putting some Bottlehead into my main monitoring chain.

However, my loudspeakers are pretty deaf:

nominal impedance: 4 ohm 
sensitivity: 86dB / 2.83v / 1m

They are also not negotiable, having been with me for over 20 years and travelled halfway around the planet with me (not trivial as they are the size of beer fridges and weigh 33 Kg a piece).

At the moment they have solid state monoblocks (balanced input), and a solid state preamp.

So having done a little math, am I correct in thinking things like the Kaiju and MonAmour don't really have enough grunt to drive low sensitivity speakers like mine?

Am I looking at something like a BeePre2 with balanced outputs to drive into the monoblocks?

(Just for a proof of concept, I am running the Mainline balanced out into the monoblocks and it doesn't sound half bad).

Open to suggestions.

Thanks

Paul.
 
Your understanding is correct; as a general rule your speakers would call for a minimum of 80 watts per channel, for "most audiophiles, most of the time." That's my rule of thumb, anyhow.

That said, if your need for loudness is modest or your room is small, you can get away with 6dB less, or 20 watts, and if both, maybe even as little as 5 watts. On the other hand, if you want large-scale symphonic extravaganzas, you might need 300 watts, and for live rock-concert levels maybe 1200 watts. It's not an exact science ... :^)

(Modest loudness means chamber music, jazz quartets, and the like - or for many people, quiet enough to not annoy the neighboring apartment/flat. A small room means something like 10 square meters/100 square feet or less.)

So yes, the BeePre2 with the upgrade for balanced outs would appropriate.
 
Hi Paul,

Thanks for that. No I don't think my neighbours would appreciate stadium rock concert levels  :D 

The room is about 350 sq feet and I probably want to make 80-ish dB with enough in reserve for 100-ish dB.

So yes, I was thinking around 50 - 100 Watts was where I needed to be.

OK I'll think further about the BeePre2. Thank you.


Hi Don, nice to meet you.

They are Harbeth Monitor 40pro. First generation (from 1998).
 
80dB will be no strain with a single watt on those speakers. We used 82 dB as an average level when evaluating masters and transfers at The Tape Project so that level is not unreasonable as an average. Peaks may get squashed a little if you are playing something really dynamic. But I suspect you would be pretty happy with the overall sound based upon your description.
 
Hi Doc,

Yep - I think we're on the same page.

I used to run at about 80dB average when I used to master. Some of my colleagues used to run >90dB average when they used to mix, especially rock, but then again, they destroyed their ears and were almost deaf by their mid 40's.

So: 1 Watt will be worth about 83dB on my speakers, minus a bit of loss here or there ...... ~ 82dB  I'm not going to quibble over a dB between friends  :)

And if a watt can make my average listening level, it is the average to peak ratio that I need to think about.

If I want 10dB headroom for peaks, I'll need 10W, if I want 20dB, I'll need 100W.

I'm not much of a fan of compressed audio, so a watt of squashed audio making 82dB - while sounding loud (essentially running the amp as a compressor limiter) - would (to my ears) sound pretty unpleasant.

(Not considering distortion necessarily, merely lack of dynamics).
 
As I recall, analog recordings rarely have more than 14dB headroom; digital for films wants maybe 20dB to allow for car crashes and explosions. Combined with an 82dB listening level gives 102dB peak SPL, which is my rule of thumb. I actually derived it by averaging Stereophile's reviews for several years in the nineties. It also matches the THX standard, which is 105dB peaks with both speakers running.

For what it's worth, SETs with zero feedback overload more gracefully then high-feedback solid state - more like a compressor than a clipper. I don't see much consensus on how much advantage that gives you - I've heard anything from 0 to 6dB.
 
Hi Paul,

Thanks for that. Most of my source material is digital - and dynamic range in the recording is of course all over the map depending on how the material was mastered. I have heard some truly heart breaking recordings, where an awesome performance has had all the life squashed out of it by a ham fisted mastering "engineer".

And of course, on the other hand, there are some "audiophile" labels which go out of their way to preserve dynamic range (amongst other attributes).

Interesting thought about SETs in overload behaving more like compressors. I wonder if you'd hear them pumping?

Also in that mode would you expect intermodulation products?

(Just musing really..... I think I know that I want the headroom).
 
I don't mean to hijack this thread, though it seem like the OP is in good hands - it raises this question in my mind.  Has anyone played with solid-state "booster" amps after tube power amps?  The idea is that the tube character is retained, and the input impedance of the booster amp (with a parallel resistor) makes an easy load for the tube amp. 
Some seem to think it's a great solution when one needs more power, but I wonder if the solid-state amp character would ruin things.
Any experience?
 
Pete, the easy solution is a tube preamp ahead of a SS amp.
Back to the headroom question, the overload characteristic of SE amps is that they get more strained sounding before they clip badly. So if you are running loud but below that hard clipping point the thing you will notice is the music getting more compressed, then more harsh. It's a different kind of degradation - I find more tolerable - than SS because the harmonic spectrum is dominated by even order harmonics as you go into the region of distortion coming on.
 
Thanks for that Doc,

So one more question about characteristics, or "sound signature".

My experience of tubes is limited to just one amp - my Mainline. It has around 30 - 40 hours on it now (so I'm guessing that there is quite a lot of burning in still to come).

I'm considering the BeePre2 - and so I have just spent an extremely pleasant evening experimenting with the Mainline as a preamp, balanced out to my SS monoblocks into the Harbeths.

Lots of things are sounding very nice indeed: Suzanne Vega, Jennifer Warnes, Dire Straits (Brothers in Arms), Marc Cohn, Afro Celt Sound System, and finally Runnin' from Live at the Matterhorn by Fat Freddy's Drop.

Midrange - brass in particular, is sounding sooo smooth. The sax on Runnin' was just jaw dropping.

Anyway... there was a question - and here it is  :)

Given that the Mainline is my only tube "reference" - in terms of sound signature, how would the BeePre2 compare to the Mainline, in this application?  And does the balanced output upgrade for the BeePre2 change its sound? if so how?

(actually that was 3 questions all at once - just like buses eh?  you wait and wait and then 3 come at once).

thanks

Paul
 
The BeePre is going to bring a bit more body to the sound compared to the Mainline, where the Mainline will tend to sound a bit more neutral.

The balanced output upgrade on the BeePre isn't a significant alteration to the sound signature.
 
Phippers

I believe Harbeth Monitor 40 can be bi-wired/bi-amp?

If so, you can go crazy and use 4 Kaiju wired in monoblocks. They will give you 32W/channel (+15db).

It will cost a lot and require lots of space though.
I can see Doc is smiling in the corner.. ;)
 
Hi Triode,

Heh!  nice thought ! 

My Monitor 40s have a single speakon connector, and IIRC it is wired as a single pair, i.e.not bi-wireable / bi-ampable "out of the box", however the crossover panel is easily accessible and so I daresay it wouldn't be too difficult to make a mod.

Even so, I fancy that 32W a side is still a bit on the low side......  not to mention me not having won the lottery :)

So sorry Doc,  as you were  ;)

Right now, I'm still Mainlining my SS monoblocks into the M40s  -  and it is all sounding pretty sweet.

Ironically, the Mainline is getting more pre duty than headpone duty.... but I'm enjoying the music so hey!

 
PB is right here as you are still only running 16W thru the woofer, which eats the power. That said, you might buy a bit of clarity from the tweeter as you push the level since the tweeter would still be driven cleanly by its amp as the woofer amp went into distortion. I'm thinking another possibility with four amps and thus 32 wpc would be to not biamp but rather wire each output transformer for 8 ohm output and connect the secondaries of two amps (hence four output transformers) in series/parallel. Hmm, do I have enough Kaijus around to try this?
 
Maybe it's time for the BIG single ended amp that was mentioned a couple of years ago, as a possible new product, on the survey.

 
I should also point out that the Harbeth Monitor 40 is a 3-way design.... so tri-amp ?  :D

But yes, the woofer would probably still not be (as) happy (as the mid and tweet) with just 16W.

Out of interest, the Harbeth Monitor 40 was designed as a drop in replacement for the Rogers LS5/8 in BBC studios. The LS5/8 was a 2-way design and was driven by a BBC modded QUAD 405 to bi-amp the LS5/8, with frequency splitting and eq performed at line level as part of the BBC mod.

IIRC, Harbeth went on to use QUAD 405's to demo the Monitor 40, one 405 per loudspeaker - I think these would have been wired as monoblocks with the standard crossover in the Monitor 40.

I like the series / parallel idea though Doc ! - the big Kaiju monoblock :)
 
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