JBL 4343 Amplifier Recommendations for Bi-Amp Application. I am new to this site

[Sasquatch]

Evening,

I have decided to build a vintage audio system. I just purchased a pair of JBL 4343B’s and plan to bi-amp them. I have the JBL 5234A Crossover with 4343 cards. My preamp is a pristine 1963 McIntosh C22 and a 1963 McIntosh 240 tube amp I plan for the highs runs at 40watts per channel. I would like to get recommendations for a vintage McIntosh solid state amplifier for the low frequency’s. I’ve been told to run a minimum of 200 - 300 watts per channel for the lows. This seems really high but wanted to get opinions. Any suggestions would be incredibly helpful. Thank you

[BMWCCA]

Can't be of much help to you on Mac stuff but I bi-amp my 4345s using a Crown PS400 on the bottom and PS200 on the top. Never have I ever seen a hint of the IOC lamps which would indicate over-driving the amps. The PS400 is roughly 200WPC. My only Mac is a C20 pre-amp that gets little use

Welcome to the group. When you have the time, tell us what you think of the 4343 and how you got interested in them. There's always a story behind these great speakers.

[Riley Casey]

The original spec sheet from JBL for the 4343 calls out 75 watts max power handling for low and high pass. A 150 watt per channel amp would assure you of having a 3db crest factor but would out run the capacity of your tube amp by 3db so a 75-80 watt amp would be adequate given your lower power high amp. Either one works. Just check the input sensitivity of the new amp and adjust to match your existing amp.

[rusty jefferson]

Phil, your mailbox is full. Please make a little room, I'm trying to send you a pm.

[Ian Mackenzie]

In bi amp mode the mid - high frequency array L pads can be advanced to the +3 db marker on the foilcal. This will increase the sensitivity of the mid - high array by 3 db which is equivalent to doubling the power of your Tube amp with the 8 ohm tap.

The woofer has a sensitivity of about 93-94 db.

The rms power rating of the original 2231 voice coil was thermally limited by adhesives used. The 2235 voice coil has double the thermal power rating.

In use with a correctly tuned enclosure the original 2231A responds well with a 150 watt rms (8 ohms) per channel power amplifier and up to a 350 watt rms (8 ohms) per channel power amplifiers.

In terms of system acoustic output in bi amp - mode, John Eargle refers to maximise SPL output level increase of + 6 db with a bi - amp crossover frequency of 300 hertz using these JBL components. This allows a + 6 db increase headroom over the use of single stereo power of the same rms power output rating. When JBL first introduced the Pro 4350 monitor which featured the earlier Pro 2230 extended bass woofer the key benefits of this driver over the LE 15 were increased power handling and extended low frequency output in a modest enclosure volume. The Pro 4350 monitor was the forerunner to apply bi amp mode operation.

The full story on the pioneering developments in JBL’s legacy studio monitors can be found in Don McRitchie’s Stereo Sound article.

Unfortunately l think the link is down on the forums but the article is available for download on Guido’s excellent JBL webpages.

https://s7a63f2c46e250b22.jimcontent.com/download/version/1521654259/module/9029655786/name/stereo_sound_story_of_jbl_english.pdf

You can find this information in this book.

https://www.amazon.com/Handbook-Recording-Engineering-John-Eargle/dp/0442005539/ref=mp_s_a_1_4?qid=1665345819&refinements=p_27%3AJohn+Eargle&s=books&sr=1-4

[Triumph Don]

If you want to stay with a vintage power amp from McIntosh, the MC2200 is rated at 200WPC, as well as the version with the classic blue meters the MC 2205. Next up the line is the MC2250 and MC2255 at 250 WPC without/with meters. I have owned 3 pairs of 4343's bi amped with a McIntosh MC2125 rated at 120 WPC, an Ashley crossover, and a few different Crown amps for the woofers. Bi amping does provide the 4343's with a vast upgrade over a single amp for sure so you are on the right track! I currently have a fantastic pair of 4345 clones powered by the MC2125 on top and a Crown K1 rated at 375WPC for the 18 inch woofers, all vintage and has sounded great for years. Happy hunting!

[Mr. Widget]

If you want to stay with a vintage power amp from McIntosh, the MC2200 is rated at 200WPC, as well as the version with the classic blue meters the MC 2205. Next up the line is the MC2250 and MC2255 at 250 WPC without/with meters. +1

Years ago I had a beautifully restored C22 and the MC240. Using these as you describe should be a great. The MC240 has a low end bloom that I am not fond of, but the mids and polite highs are quite nice. By using it in a bi-amped system you will definitely get the most from it. Using a vintage Mac on the woofers might be a challenge, but the MC2205 would probably give you a reasonably controlled bottom end. Many of the newer Macs may do a better job, but they won't be vintage Mac.


Widget

[Ian Mackenzie]

I had a Marantz 140 power amp that had nice blue meters. It did however subjectively…. Suck.

l have seen excellent feedback on this range of power amplifiers.

https://www.behringer.com/behringer/product?modelCode=P0A37

In the low frequency range the digital amps have edge these days over conventional class AB linear audio power amps. They are more efficient and more dynamic when designed properly (not a cheap Chinese plate amp). You might find them more fun and energetic than a hifi power amp with the 4343.

https://www.behringer.com/behringer/product?modelCode=P0A37

[speakerdave]

Those speakers are built to take some drive and will perform, if you supply it.

I wouldn't recommend an early auto former McIntosh on those woofers. I used the MC2200 on my 4333A's and it clearly gave up something to higher current solid state amps. Later autoformer amps might be better. I don't know.

The problem is that the original C22 may be looking for higher impedance than most other solid state amps will have, even McIntosh non-autoformer ones.

Strictly speaking, the C22 MC240 are not a period match for the 4343B, and it matters, because your electronics are from the old tube era of high impedance power amps (MC60, 500k) and 105dB speakers; your speakers' 93 dB woofers are designed for modern direct-coupled high damping factor solid state amps, which are low impedance, usually 10-20K ohms.

If you want to use a tube preamp, one from Audio Research of the 4343B era would tolerate the low impedance of a solid-state bass amp, as would the re-issued C22.

Edit: Found the user manual for the original C22, though I think late in the series. It is spec'd OK at 50k load impedance, which the crossover specs at, so maybe OK. I would want a lot more.

[jbl4ever]

Being these are the 4343B version as the OP said the woofers are 2231H’s. They have a rating of 200 watts continuous program. Not 100 or 150. I found they work best with amplifiers in the 250-300 watt range. Threshold S500II, Eagle 7A or the Krell KSA 250. These give you lots of dynamics in the loud passages and do not run out of drive

[Shlobeck]

I have a pair 4340s which preceded the 4343s but have the same drivers. Same speakers different cabinet. I’m running a 4 way active system with a vintage restored 4 way sansui crossover. I’m running 4 restored marantz amps; 3 250s for the High frequencies and a 510m for the low frequency, the Alnico 2231. After the 510 was rebuilt the unit puts out over 300wpc. The 2231 has no problem with the 510 at very high SPL levels, it’s a wonderful combination. I’ve played this system at high volumes for hours on end with no issues. I personally don’t think 40wpc is enough for your high frequencies.

[Ian Mackenzie]

I re read this thread again and one thing that stood out was using the 5234A solid state monolith chip active crossover with valve based components. Read on.

In theory you would think it will work and yes it does. But l for one found the 5234A scrubbed the sound leaving an electronic glare that l found fatiguing to listen to. The Ashly analogue crossover is a bit better. But neither are a clean transparent window to hi fidelity if you want the best out of your system. You can attempt chip rolling with these crossovers but in general it’s not a cure.

I was involved in prototype testing of these active crossover kits and they are brilliant if you can solder. The design is very simple using discrete Jfet buffers with zero feedback. The kit can be set up for specific crossover characteristics as desired. Best of all it’s a really inexpensive avenue to a transparent active crossover if you using valve equipment or consumer hifi components elsewhere in the signal path.

https://diyaudiostore.com/collections/kits/products/diy-biamp-6-24-crossover?variant=31765939322953

On the power rating question size matters on the woofer and l would be looking at a digital power amp these days. They deliver high power and high current efficiently to the load.

For the mid high frequency array my tip is turn the mid cone Lpad up full and adjust the horn and slot L pads to match. This will make the mid high frequency array more sensitive and more dynamic.

A descent 50+50 watt - 8ohm hifi power amp will get you going with the above adjustments. You might have a nice valve power amplifier in the 40-50 watt / 8 ohm rating. My understanding is Quicksilver power amplifiers go well with JBL horns. It will work fine and you might be surprised just how good these 43XX systems sound. As l have said before trust your ears.