Quad II amplifiers - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

PJL · 20th Jul 2017, 2:17 pm

I had a pair of Concerto's but they are big and need to be in a very large room to be appreciated. I replaced the crossover caps and they did sound good with plenty of dynamics and bass but got rid of them as they needed cosmetic work and the wife was never going to tolerate them.

Speakers are a very personal choice. I am currently using Castle Harlech's which have the advantage of looking good. Being transmission line they are very dependent on room position. I found them very dry when driven by a good quality solid state amp but sound brilliant with my valve amplifier.

Reviews of vintage speakers are very mixed. One of the factors will be the condition of the crossovers and drivers but there is also plenty of hype. I recently picked up a pair of 70's B&W DM4's which get generally good reviews (they were £15). They are OK compared with some of the cheap modern junk but I am not ecstatic.

ToneArm · 20th Jul 2017, 8:58 pm

I use JR149s with my quad II amplifiers and they sound lovely. Very natural, lounge/wife friendly size and appearence, and can be had for £300 or thereabouts without difficulty.

Radio Wrangler · 21st Jul 2017, 12:17 am

The quad electrostatic speakers are open-backed, so they have to be placed well out from any wall to the rear, and you definitely need a larger than average room to get reasonable results.

My big transmission lines are best not tucked right into corners, or else the bass gets over-done. They go against the wall OK, but are moved in a couple of feet from the corner.

The combination of a bass frequency and a sound pressure level dictates that a certain amount of air needs to be pumped. No speaker design, no fancy badge, no big price tag, can get around this. It is a physical property of the air between you and the speaker. Smaller speakers are faced with a compromise involving cabinet pressure versus lowest note reproducible versus sound pressure capability at low frequencies. All to often their designer conceals the lack of deeper bass by putting a bump in the frequency response at the bottom end of a limited response. The so-called one-note-bass. The illusion works quite well on drums, but it comes apart when there is a played bass theme.

Pick your speakers to suit your room - it's the best you can do in the area of the biggest compromise in reproducing music.

David

qualityten · 25th Jul 2017, 10:43 pm

Is there an impedance from the Quad output transformers to consider too? 15ohm? I have a pair of KEF 104/2 speakers that I like very much with valves, but their impedance is 4ohm.

Craig Sawyers · 25th Jul 2017, 11:03 pm

The Quad II output transformer can be wired for 15 ohms or 7 ohms

But then again the ESL57 impedance drops progressively from 5kHz (about 10 ohms) to 15kHz (2 ohms).

But I seem to recall that the 104/2 had a target design to present as close to a resistive (4 ohm) load to the amplifier, and simultaneously correct each driver for a flat acoustic response. As a result the crossover is very complex indeed.

20th Jul 2017, 2:17 pm	#21
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Quad II amplifiers I had a pair of Concerto's but they are big and need to be in a very large room to be appreciated. I replaced the crossover caps and they did sound good with plenty of dynamics and bass but got rid of them as they needed cosmetic work and the wife was never going to tolerate them. Speakers are a very personal choice. I am currently using Castle Harlech's which have the advantage of looking good. Being transmission line they are very dependent on room position. I found them very dry when driven by a good quality solid state amp but sound brilliant with my valve amplifier. Reviews of vintage speakers are very mixed. One of the factors will be the condition of the crossovers and drivers but there is also plenty of hype. I recently picked up a pair of 70's B&W DM4's which get generally good reviews (they were £15). They are OK compared with some of the cheap modern junk but I am not ecstatic.

20th Jul 2017, 8:58 pm	#22
ToneArm Pentode Join Date: Feb 2015 Location: Conwy, Clwyd, UK. Posts: 246	Re: Quad II amplifiers I use JR149s with my quad II amplifiers and they sound lovely. Very natural, lounge/wife friendly size and appearence, and can be had for £300 or thereabouts without difficulty.

21st Jul 2017, 12:17 am	#23
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,867	Re: Quad II amplifiers The quad electrostatic speakers are open-backed, so they have to be placed well out from any wall to the rear, and you definitely need a larger than average room to get reasonable results. My big transmission lines are best not tucked right into corners, or else the bass gets over-done. They go against the wall OK, but are moved in a couple of feet from the corner. The combination of a bass frequency and a sound pressure level dictates that a certain amount of air needs to be pumped. No speaker design, no fancy badge, no big price tag, can get around this. It is a physical property of the air between you and the speaker. Smaller speakers are faced with a compromise involving cabinet pressure versus lowest note reproducible versus sound pressure capability at low frequencies. All to often their designer conceals the lack of deeper bass by putting a bump in the frequency response at the bottom end of a limited response. The so-called one-note-bass. The illusion works quite well on drums, but it comes apart when there is a played bass theme. Pick your speakers to suit your room - it's the best you can do in the area of the biggest compromise in reproducing music. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

25th Jul 2017, 10:43 pm	#24
qualityten Octode Join Date: Feb 2009 Location: Wallasey, UK. Posts: 1,310	Re: Quad II amplifiers Is there an impedance from the Quad output transformers to consider too? 15ohm? I have a pair of KEF 104/2 speakers that I like very much with valves, but their impedance is 4ohm.

25th Jul 2017, 11:03 pm	#25
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 4,981	Re: Quad II amplifiers The Quad II output transformer can be wired for 15 ohms or 7 ohms But then again the ESL57 impedance drops progressively from 5kHz (about 10 ohms) to 15kHz (2 ohms). But I seem to recall that the 104/2 had a target design to present as close to a resistive (4 ohm) load to the amplifier, and simultaneously correct each driver for a flat acoustic response. As a result the crossover is very complex indeed.