Hi Olaf,
If there something about the 4345’s sound that prompted the original question?
Hi Olaf,
If there something about the 4345’s sound that prompted the original question?
These things do sound better driven to a level beyond any bookshelf loudspeaker.
The sound gets bigger, not louder. It’s the inherent linearity of the eighteen inch woofer in combo with the other low distortion drivers. Those woofers really couple to the room boundaries. You don’t get the same effect with the DD67000. They have more definition but don’t reach as deep with the same effortless authority.
I have a method I use to determine ideal amplifier power for any system.Originally Posted by Dr.db
1. How sensitive is the speaker?
2. What is the maximum SPL I expect to see?
3. Is this a distributed audio system or Hi-Fi system? Distributed audio get's 3dB of headroom and Hi-Fi 10dB.
The HF section of the 4345 has a sensitivity of 98dB/watt/m
Let's say you want a max SPL at a meter of 106dB... very loud, but not quite rock concert levels.
This is a Hi-Fi system.
Therefore you need ~7 watts to hit your goal of 106dB at a meter and should use a 70 watt amp to give yourself 10dB of headroom.
With this system, I have never had clipping issues or blown drivers.
Obviously you need to match the speaker to the task. If you have a speaker with a sensitivity of 85dB/watt/m and you want 110dB at a meter, you will need ~300watts to hit 110dB and 3000watts to give yourself the headroom. This speaker is most likely not going to give you the SPL you require. At best there will be far too much dynamic compression and very likely you will have thermal failure.
Widget
@markd51:
To simplifiy it: When bassdrivers and middrivers have the same sensitivity, the bassdriver will still require a multiple of the power of the middriver for the same level?
@Ian:
I get the idea of the continuous programm power and the occasional peaks being far greater. Good point.
But how do you feel about the frequency depending power requirements? Is the difference between the bass and midregion really only the 3db in sensitivity?
You suggested a minimum of 100watts for the HF. When using these 100watts for the HF, how much do you suggest for the 2245 in this circumstance?
@ngccglp:
Nothing wrong with the sound. I was just wondering if using a little class-a amp with 20watts will work.
@widget:
Your example of 106db SPL at a meter with 10db-headroom indicates 70watts for the HF-section. Sticking to this example, this would indicate 140watts for the 2245, correct?
Yes, but I would go with 200 min as any EQ down there will drastically increase your power requirements. Not to mention 200wpc amps are pretty common.
Widget
Hi Olaf,
To answer you question we need to look at how things were done back in that era.
This range of Jbl pro monitors were targeted at the recording industry where high continuous SPL were required and reliability was important.
Those requirements are somewhat more demanding that our vintage legacy listening habits as we will see but the same principles apply.
John Eargle was consulting to JBL at the time and had considerable input on how monitors were used in the industry.
Referring to The Handbook of Recording Engineering a whole chapter is devoted to studio monitors with design examples using bi amp techniques.
I unfortunately don’t have a copy of the text to paraphrase but it was laid out like this.
See next post
To calculate power you work backwards using:
Loudspeaker driver sensitivity
Loudspeaker driver power rating
Listening distance
Available amplifier power
Crossover points
So let’s make some assumptions
The listening position back then was four metres from the monitors in a large control room (a 12 dB reduction in spl taken at 1 metre)
The mix engineer needed 103dB at the desk
The rated sensitivity of the 4345 was 95 dB ( with the Lpads at zero position)
The engineer required a 6 dB margin of dynamic headroom.
In this situation this is what we have:
95 dB @ 1 metre for 1 watt
105 dB @ 1 metre for 10 watts
115 dB @ 1 metre for 100 watts
A 10 dB increase in SPL required x10 amplifier power.
A doubling of the distance is a -6 loss in spl.
Therefore, @ 4 metres the above spl figures become:
83 dB @ 4 metres for 1 watt
93 dB @ 4 metres for 10 watt
103 dB @ 4 metres for 100 watts
See next post
The amplifier requirements back then were a limitation and Jbl was a pioneer in Biamping.
The approach taken at the time was a 300 hertz crossover point was a 50/50 split in the amplifier power rating and a 800 hertz crossover point was a 75/25 in the power rating.
In the text reference is made ( and documented elsewhere) that two 50 watt amplifiers in Biamp operation deliver the equivalent of a 200 watt amplifier.
Why is this?
A 200 watt amplifier must deliver 40 volts rms into an 8 ohm load to deliver 200 watts
A 50 watt amplifier must deliver 20 volts rms into an 8 ohm load to deliver 50 watts.
The voltage crest factor of 6 dB or 20+20 volts =40 volts is the reason behind this calculation.
A doubling of voltage gives four times or a 6 dB increase in rms power to the load.
So taking the above figure of
103 dB @ 4 metres for 100 watts
Therefore,
103 dB @ 4 metres for 2 x 25 watts (crossover 300 hertz) will deliver equivalent output of a 100 watt amplifier.
Then Biamp using two identical 100 watt amplifiers would give a 6 dB headroom factor.
109 dB @ 4 metres for 2 x 100 watts ( crossover 300 hertz)
112 dB @ 4 metres for 2 x 200 watts (crossover 300 hertz)
115 dB @ 4 metres for 2x 400 watts (crossover 300 hertz)
L pad adjustment to max on mid, +3 dB on horn and slot will
reduce the mid high array amplifier power to 200 watts
Note these outputs are far above the capability of a typical hifi loudspeakers regardless of price from 30-20,000 hertz.
See next post
So it’s a matter of looking at your maximum desire spl at your listening position and scaling your amplifier power rating from there.
The thing to remember is that if your looking to go louder your power amplifier rating will go up very quickly. 6 dB is a noticeable increase in loudness. 10 dB is considered twice as loud. That would require 4 x and 10 x the amplifier power rating respectively.
A few things to note:
Turning up the Mid Lpad to full and the horn and slot to + 3 dB will increase the mid high array sensitivity to 98 dB. So your amplifier power requirement is half in that scenario. But you loose adjustment of the L pads.
Modern recordings are more dynamic than older analogue recordings. So the 6 dB headroom factor is a reasonable allowance.
High power digital amplifiers are relatively inexpensive. So you can put a 300 watt or 400 watt digital amp on the 2245H and then use your nice HIFi amplifier on the mid high frequency array. There are numerous high quality hifi amplifiers out there in the 100 watt range.
IMHO you are going to subjectively notice a high power amplifier more on those woofers.
My suggestion is use the best power amplifier or integrated amplifier you can afford on the mid high frequency array and you will be well rewarded. The mid high frequency array is analytical enough to be able to discern subtle differences in amplifiers and signal path electronics not to mention the source.
I currently use an Ortofon Black and a Purple Heart mc cartridge on my VPI Prime with a Parasound JC3 and JC2 with an AC23+ power amp rated at 160+160 watts and it’s superb. My digital Yamaha pro power amp rated at 800+800 watts is on the woofers.
There could be the odd error in my calculations. Let me know if you spot any.
Buyers Guide Comments on power amplifiers
I am not here to plug Parasound but the A23+ does have useful features such a independent level controls and balanced/unbalanced inputs on the rear. I think it’s the equal of my Pass X250.5 and more neutral sonically. If you want to hear how your recordings were recorded as intended by the producer the Parasound 23+ is your amplifier. That is what l hear when l play some re released albums. The combo of the 4345 and the Parasound 23+ brings you closer to the original recording. The Pass 250.5 is nice and refined but it’s warmth and zing are best left out if you want to experience the evolution of recordings over the last five decades.
Meaning the Parasound is very good value for money and a great match for this genre of loudspeaker.
https://www.soundstageaccess.com/ind...mono-amplifier
And then I'll share my opinion on such speakers as all the 4300's, 4400's, and so many other great JBL Speakers that have been made over the last 60 years.
And that's why fix what isn't broken? For all the work the designers-engineers and the end testing and adjusting, aneoic chambers, hosts of JBL critics listening, and here you smarter folks have to split the shit out of the work they did, thinking you'll break on through to the other side.
Will you?
But like earlier, and not fussing with bi-amping, tri-amping, using a mixture of who knows what Amps to get a job done, maybe just go buy yourself a good high quality Amp, be it a Stereo, an Integrated, or a pair of Monoblocks?
And I'm not talking some cheapo D class that weighs 4.5 lbs, a pair of Mac 601's, you want a very nice integrated, go for the Gryphon Diablo, Bryston 14B3, or 7B3 Monos, or there's multiple dozens more, Parasound, etc.
I'll save space, but as I touched upon, quality power will be the key to getting the best sound from JBL. Are there better speakers out there than a pair of 4345's? You bet there are. Don't ever think the 18" can go so low, and be so authorative. Dynaudio has made 6" Bass Drivers that can handle 300 watts.
And a pair of $45K-$65K pair of Dynaudios? Yeppers I've heard them, world class speakers.
Hi Moe,
Nicely put.
What l would say is that Greg Timber’s has endorsed a number of small but important changes to these systems that collectively offer real improvements. That’s simply because Jbl marketing compromised the execution of the designs.
So your argument is with Greg. When l last met Greg we were messing with Biamping and we decided to set up an original 4331 in Biamp mode. Once correctly adjusted and placed up on crates with some room correction we compared the DD67000 to the 4331.
This is the thing. We got the 4331 to sound way better than it had any right to with high quality bi amp crossover and some careful measurements and adjustments to the response. So it was a line ball comparison to the DD67000.
That my boy is not screwing with the design. We simply were getting more out of those vintage drivers by using our smarts.
What my last few posts were about was an attempt at a layman’s explanation of how much power do you need.
Time for some pancakes and maple syrup.
You all enjoy your weekend.
I can understand that....somewhat! LOL
Here it came, charged coupled X-overs, and of course today, we have more in the way of better Caps, Inductors, and other electro parts than Carter has pills. Or do we?! LOL
I'm sure somebody out there has a design and might build me 4 Charged Coupled X-overs for my 4 L65's. I'm sure they'd lighten my bank account too.
No doubt my 4430's pale in comparison to a pair of 4345 Monitors in some aspects, but then again, maybe they have qualities that they don't too, but I'm not about to hack them to ribbons to try making them something they aren't.
Before I do something like that, I'd rather dig down, and look into other speakers, other designs. Would I be stupid to have a pair of B&W 802D3's in house, Wilson Sophias, big Magnepan's, Martin Logans, no of course not.
All of them hole great merit. Just loan me $20K, will ya?! LOL
I am aware that this is what a clean pair of 4345's will cost as well, a good $20K give or take a few cents or so. Truly a speaker that sure would be nice to see JBL re-issue, but at what cost? Probably $70K.
I remember once trying to fit a pair of different bass drivers in my Jubals. They might've been 2216? Or 2212?
Beautiful looking driver, might've fit the front baffle, had not the L-shaped Port tube been in the way interfering with the driver's huge magnet.
Those drivers were on free loan, but I brought them back. Wasn't about to take a hatchet to a very clean pair original bought pair-quad of L-65;s just for kicks. They still have their 126A's, LE5-5, and 077's stock.
Moe,
You can build up a 4345 clone for around $5,000 (estimate)
The 4430 is a very good loudspeaker.
But newer updated woofer like the 2216nd would significantly improve the midrange clarity.
Adding a Radian Be one inch driver would also improve its performance. When l get a chance l might try that....Lol
I think I once posed these same questions about an upgrade to Bass Drivers in the 4430, and pin-pointed the 2216nd as a possible upgrade replacement?
I'm not up to a lot of the technical jargon such as cubic foot cab size requirements, damping-porting and whatever else required physically, but gathered that such could be a hit or miss unknown swap without further enhancements-adjustments and mods made electronically to the Crossover Networks?
Yeah, beautiful looking drivers those 2216nd's are! Look massive.
Yep, maybe one day someone will delve into such a project with hard core measurements to back up such mods and them being worthy ones and not too complicated.
I don’t have a definitive answer for the OP, but I do use a choice one of three pairs of monoblocks:
Mark Levinson No. 434, 125 Watts.
DIY KT120 based 100 watt tube amps.
DIY 6L6GC based 18 Watt tubes amps.
They all work just fine for me.
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