UnderTow

mike_mccue


If it was a traditional passive system with a 150 watt per channel amplifier (at some rated THD etc) hooked up to 2 way speakers... The passive system would be marginally quieter because a small amount of energy would be divided out to protect the tweeter.

What would you call it?

I'm not sure I am following your line of thinking here. But anyway, see below.

I call my working class quality JBL6328P biamped 250/120 watt speakers a 220 watt system because that's what JBL rates them as.

Isn't that a difference between peak, program power and RMS power?

edit to add: Just to point out the differenet way to view this... Using Tweaks math my 220 watt system could be described as 370 watts?

Well that is what PSI says about my speakers. They call them 170 + 80 + 50 Watts or 300 Watts.

If the amps are well matched to the drivers, they should all be loaded in a similar way. I mean, all else being equal,  why have an amp for a tweeter that is, relatively speaking, twice as powerful as the amp for the bass driver? That would just be a waste. So if the load is evenly shared, why not just add up the wattages? In the end it doesn't really matter. The wattage won't tell you how loud the speakers are anyway.

Of course there could well be situations where completely different aspects affect the engineering decisions. Maybe a specific tweeter in a specific monitor only needs a 30 Watt amp but the manufacturers make three other monitors with a 50 watt amp on the tweeter so it is cheaper to just use the 50 watt amp etc... (economies of scale). Or simply availability of parts. That could go either way. It could end up being a "better" part or a "worse" part... who knows... Every work of engineering is an exercise in compromise as I am sure you well know.

UnderTow

In my example of the JBL LSR6328P the biamped 250/120 rating is a description of two amplifiers.

Bi-amplified Power System
The LSR6328P combines two high power amplifiers with an active dividing
network. Included are over 250 watts of continuous low frequency power and
120 watts for the high frequency section.

Sine Wave Power Rating: 250 watts (<0.1% THD into rated impedance)
Sine Wave Power Rating: 120 watts (<0.1% THD into rated impedance)

Long-Term Maximum System Power: 220 watts (IEC265-8)

I can't find it at the moment but I think the burst or peak rating for that speaker is 800 watts.

The cabinet has a built in "250" watt amplifier for the woofer and the tweeter has a "120" watt amplifier.

I think we are on the same page that there is no need to supply the tweeter a full 250 watts because of the sensitivity of both the tweeter and our hearing.

As a comparison when you have a 250 watt per channel amp (at similar THD) driving a speaker cabinet with a passive crossover the tweeter is protected from all the wattage with a divider network that maintains the design load impedance. It wastes energy but it works.

If you use an external rack mount active crossover... as is frequently done with large public address stacks you may split the lows and highs and dedicate a large amp to the woofer cabinets and a small amp to the tweeters. The primary reason to do this is that you do not waste the energy. This is not about being "green" conservative but rather practical logistics when good AC mains power is in short supply.

It is a type of bi amping but the practice usually manifests itself as multi amp, tri amp, or just about anything goes... you engineer a stack to make best use of your power supply while hoping to provide adequate SPL for the setting.

I have traditionally rated a system at the value that I consider is driving the woofers.

If I assemble a PA that has 4 amps capable of a clean 1000watts driving the woofers I'll call it a 4000 watt system and disregard the fact that I have 2 600 watt amps driving the upper mids and a 400 watt amp on the tweeter cabinets.

I am open to correction, but I have never summed the low and hi power because we are describing a system that is defined by the capability of the low, low-mid system.


If JBL rates their 250/120 biamped cabinet at 220 I imagine they would rate their 150/70 biamped system at 130 (they don't list that spec in the 4300 paperwork but do in the 6300 paperwork) I was being purposefully generous when I called it a 150 watt system.

best regards,
mike

UnderTow

mike_mccue
Undertow, do you believe in the idea that speakers break in? If you do... and I think to some small extent I do... how does that relate to some test result made in an anechoic chamber when the speaker is brand new?

Just curious what your take on it is.

I don't know if all speakers need breaking in... and I have read that some manufacturers do some breaking-in at the factory...

I think it's pretty obvious that speakers will eventually break down.  Thus there is some point at which they are at their peak performance and at any point in time after that they will only get worse in sound quality.

But I don't know why there is a belief out there that puts that peak in performance somewhere after the point of purchase. Yes, some manufacturers will do a factory 'break-in' and if they think it helps, then why not have them do it? But (quality) speaker designers are using quality components that are chosen to be durable (among other things). There is every reason to believe that a speaker's peak performance is at the point of manufacture and it's all downhill from there.

Why do speaker 'break-ins' always result in improved subjective performance? Has there ever been a report of a speaker worsening in performance after the break-in period? That should statistically be the case, given a large number of speaker models, manufacturers and listeners--there should at least be a few sets of speakers that come off the line sounding great but then worsening in performance during the 'break-in' period, but I have yet to see a report like that and I've never encountered such a phenomenon myself.  Could it be that it's a case of listener adaptation to a new set of speakers rather than some sort of mechanical settling in/loosening up?

Presumably, competent speaker manufacturers do all sorts of quality tests on their products. Why don't they publish their graph of performance vs. time? Maybe because it's irrelevant? Maybe because there is no appreciable difference in quality from the point of manufacture and the point where the warranty runs out? If a company did make a speaker that did have a break-in period, wouldn't they want to publish such a spec?

Yes, speakers wear out over time. No, I don't think speakers need a break in period. I do think (or more strongly, I know) that our ears do.

Ahhh, the '60s.

tarsier



I think it's pretty obvious that speakers will eventually break down.

 I do think (or more strongly, I know) that our ears do.

Hah. Next you are going to tell us we don't need 20.000$ cables and that the same files played from different hard discs sound the same!

UnderTow

Crush

Sine Wave Power Rating: 250 watts (<0.1% THD into rated impedance)
Sine Wave Power Rating: 120 watts (<0.1% THD into rated impedance)

Lol.. more misleading numbers meant for the 'think they know about speakers' market.

I'm just sitting back laughing at all this and eating popcorn. Better than a movie.

Much like one of your very very bad you tube videos then aint it Crush