Tips on Driving Speakers to High Volume Levels.

[FR500C]

I have a pair of 300B Paramounts.  I love them.  90% of the time they drive my ~88db speakers just fine (Titanium Gallo Roundsound).   Once in a while, though, I want to listen to music at very loud levels and my preferred setup just runs out of gas.  So, I switch to a 30W per channel push-pull based amp and am able to get that extra bit of live concert experience I'm looking for at the expense of some detail and imaging.  So, my questions are:

(1)  If i find a used pair of say Klipsch La Scalas, is it safe to say I'll be able to enjoy fairly loud volumes with the Paramounts?
(2)  I just don't have the time to build a set of horn speakers from scratch.  Is there a horn speaker kit available where the enclosure has been precut that includes horns, crossover sound deadening material etc. that you folks can recommend?  I am fine with finish and assembly, but just am not setup to do the cutting/routing/etc. on the enclosures.
(3) or can I buy another pair of 300Bs and somehow bridge them to drive my existing speakers.(apologies if this is just a dumb idea) but am curious how/when bi-amping etc.works.

Thanks.

[Len]

I think Pi Speakers still makes kits. I know some people here have them and are very happy with them.

I use pi cornerhorns, with only the 15" bass drivers installed, with 2a3 paraglow II's for bass duty. They go pretty loud.

Maybe someone who is using complete pi's can chime in.

[Paul Joppa]

I think more efficient speakers are indeed worth exploring. However, be aware that they will sound different, especially if they have horns. They will have both virtues and vices that are different from what you have now, and it may take some time to decide where the better balance is. If possible, try to find a club or group near you; in any case listen to as many varieties as you can. And, much as I appreciate the virtues of single-driver systems, very very few of them can be cranked really loud without cone-excursion-limited distortion.

It seems from your post that you need 30 watts (6dB more than 8 watts) to obtain satisfactory loudness when you want to crank it. That's not surprising; 6dB is subjectively "twice as loud" according to the psychoacoustical scholars. Two tube amps bridged or otherwise acting in tandem will only give you twice the power, i.e. +3dB. To get +6dB you'd need four amps.

My preferred method of multiplying amps is to wire the output winding in series. This raises the impedance linearly:

Two 8-watt amps using the 8 ohm tap in series gives 16 watts into an 16 ohm load.
Two 8-watt amps using the 4 ohm tap in series gives 16 watts into an 8 ohm load.
Four 8-watt amps using the 4 ohm tap in series gives 32 watts into a 16 ohm load.
Two 8-watt amps using the 1 ohm tap in series gives 16 watts into a 2 ohm load.
Four 8-watt amps using the 1 ohm tap in series gives 32 watts into a 4 ohm load.

The Paramount has taps at 4, 8, and 16 ohms but can be wired for a 1-ohms load with a slight sacrifice in copper losses. Doc B uses four of them to drive the 4-ohm midrange in the big system now in his living room. We could probably have a special run of transformers made with 1, 2, and 4 ohm taps if there were a big enough market for this approach, but it hasn't happened yet.

[dth31]

I can't speak for Klipsch La Scalas, but I use 300B SETs on Klipschorns, and they will get REALLY loud--way louder than anyone would ever want to listen.  It isn't too hard to find Klipschorns for around $1500, depending upon the year and condition.

[ssssly]

You can get speaker kits for several of the fostex full range drivers delivered as flat packs and you just glue them together. I have a pair of 108E Sigmas that I built the fostex recommended rear loaded cabs for and in my smallish listening room they will definitely get way loud driven by my Paramours. I have never personally heard any of the kits but they might suit your purpose.

[Grainger49]

In general terms your speakers are not the best match for SET amps.  I didn't like my previous speakers on SETs when I first tried them.  There was magic there but it ran out of steam.  Your experience is the same as mine.

I think speakers are the answer for you.  Doc used to have a list of SET friendly speakers but I can't find it.  The Cain & Cain, Horn Shoppe, Pi, Klipsch, and many of the Triangle as well as Fostex based systems are good candidates.  

So to 1) yes, to 2) yes, see the list, there are a number, and to 3) I think that is the most awkward way but it can be effective.

[FR500C]

Thanks for your helpful replies.

I'll try your suggestions on horn based kits.

Generally, to run the Paramount mono blocks in tandem, using the right channel driving an 8 ohm speaker as an example, I would use the 4 ohm taps on the output transformers, connect +tive output of Amp A to the -tive output of Amp B, and connect the -tive output of Amp A to the -tive terminal of the speaker, and the +tive output of Amp B to the +tive speaker terminal?

Do I split the right channel signal coming out of the preamp and connect one to Amp A's input and the other Amp B's input?  Don't I have to invert one of the signals to get the differential signal that makes this work, or is that handled on the output side by virtue of connecting in series?

I think that I have the output side figured out for 2 amps, but really clueless on the input side.

Apologies for what I'm sure is torture for the folks who do this sort of thing routinely.

[Paul Joppa]

Your first guess is correct - just parallel the inputs. Reversing phase at teh input, and again at the output, would create a kind of push-pull which might be interesting but will not sound like SET. Also, you'll have to un-ground the output transformer secondary on at least one amp to do this.

[Follow the white rabbit]

Hi , I have found a pair La Scalas (1979) in Berlin ... and they rock with my Paramount 2A3 monos ...

Greets

[Paully]

I have played 2 watts on a pair of LaScalas and they went to ear blistering (damaging) levels.  A pair of Paramount 300B will drive them no problem, if memory serves.  Other options to consider are Klipsch Cornwall and the Chorus II.  Also some nice Altecs (I just bought the 846A) can be had in the same price range.

Another option, since you can solder, is to rebuild a Dynaco or some such for those moments when you want to play your 88db speakers and play them loud.  Enjoy!

Paul