Underpowering JBL 250TIs....??

[edgewound]

I noticed on my receiver that most of the volume comes in after 12 0'clock.I don't believe I am getting half the volume at 12 0'clock as after 12 0'clock the volume shoots up dramatically.

That reason behind that perception is that distortion is perceived as being "louder", when in fact it's filled with all sorts of nasty harmonic artifacts that hopefully tells your ears to "turn it down"...because in reality....it's just plain unpleasant to listen to.

Ironically....it's also very unpleasant for the speakers to reproduce.

Again...to reiterate....

It's not the lack of power that burns up speakers. It's the distortion level.

Again...to reiterate. If you need...or like to listen at loud volume levels....you need the power to get there cleanly.

So...if you listen loud....get more power.

Practice "Safe Sound"...or you'll eventually kill your speakers...tweeters and mids go first.

[kingjames]

That reason behind that perception is that distortion is perceived as being "louder", when in fact it's filled with all sorts of nasty harmonic artifacts that hopefully tells your ears to "turn it down"...because in reality....it's just plain unpleasant to listen to.

Ironically....it's also very unpleasant for the speakers to reproduce.

Again...to reiterate....

It's not the lack of power that burns up speakers. It's the distortion level.

Again...to reiterate. If you need...or like to listen at loud volume levels....you need the power to get there cleanly.

So...if you listen loud....get more power.

Practice "Safe Sound"...or you'll eventually kill your speakers...tweeters and mids go first.

I have always heard that more wattage meant cleaner sound and not so much more volume. I would have to say based on all I read here that is a true statement.

[edgewound]

I have always heard that more wattage meant cleaner sound and not so much more volume. I would have to say based on all I read here that is a true statement.

Actually....both are true.

Because in the end result with a given system, you can't get more sound without more power.

[johnaec]

I have always heard that more wattage meant cleaner sound and not so much more volume. I would have to say based on all I read here that is a true statement.

I think what you're referring to is the fact that doubling the input power only results in a 3dB increase in sound output.

It's long been determined that it takes about a 10dB increase in sound output for most people to perceive a sound as twice as loud. Since it takes 10 times the power input for a 10dB increase in sound output, an amp that's only twice the power will only result in a small (3dB) increase in volume.

John

[subwoof]

For a treatise on this in a consumer lingo refer to the JBL note titled: Danger: low power.

One thing that has not been mentioned at all is what happens when you clip a waveform. This is 1st year stuff in an EE program or engineering school.

Now here is yet another analogy for the "library"

You take your sweetheart on a hiking trip to a waterfall. You climb down the steep gorge and marvel at the thunderous noise when the water hits the rocks. You can't even hear your self think let alone have a conversation.

You walk back to the car and talk about the experience during the drive home.

NOW the next day you are getting a wiener from a street vendor during your lunch break and the local DPW is chopping up the sidewalk with a jack hammer the whole time you are waiting. You go back to the office and your ears ring all afternoon and you have a headache that evening.

Now BOTH of these sources were loud. BOTH were very wide range. BOTH were of the same duration but the after effects were different because the JACKAHMMER pounding the concrete was producing odd AND even harmonics while the waterfall produced only even.

....The math....

A pure sinewave of 1000hz will have just a single component when viewed on a spectrum analyzer or listened to.

When you add harmonics ( overtones for the musicians amongst us ) the "timbre" is changed and it will begin to sound like a specific instrument depending on:

(A) The level of the original note
(B) The number of Harmonics ( odd and even )
(C) The level of EACH of those harmonics.

This is why middle C sounds one way on a piano, another on a flute and yet another on a violin. Same note, DIFFERENT harmonic composition.

Now when an amplifier is fed a nice, pure signal and you run out of headroom, the output clips and for you guys ( and gals ) who got a little into advanced math, the result is a whole spectrum of odd order harmonics.

This is basic transform analysis....and when you sum a series of odd order harmonics you get a square wave. If you add up a series of even harmonics you get a triangle wave. Cause and effect - if the squared portion of a wave form is there, there HAS to be odd order harmonics.

So the bottom line is that even though you have a tweeter in a cabinet that is crossed over at 5000 hz, ANY clipping at ANY frequency below that will produce artifacts that the tweeter WILL be forced to reproduce and this is why so many tweeters die an early death while the woofers are unscathed.

Look at it this way: Clipping a floor tom drum (100hz) will create odd harmonics of 300,500,700,900,etc all the way up into your beloved tweeter. So that means ( in the example of a 250Ti ) it will impact the low mid, high mid AND tweeter....for a nice listening experience.



sub ( and I don't mean sandwich )

[JSF13]

Cool!

[Robh3606]

Some good info on this

http://sound.westhost.com/tweeters.htm


Rob

[JBLRaiser]

http://cgi.ebay.com/Mint-DYNACO-400-...QQcmdZViewItem

They come up often for around $300. I love mine.

[sourceoneaudio]

Source,

I do get it, but when another 250TI owner PM's me and tells me that he runs just fine with under 200 watts, then I am feeling more comfortable with my NAK. But thank you for the bashing, anyway's.

I don't have extra money laying around to buy another amp.


-Storm

No bashing here going on, just speaking the truth. We have all discussed this same issue with you b4. It just gets a little old repeating the same sheeet all the time. Remember the massive discussion on the 14 watt amp verses something else to run you Val's. Pretty much the same subject. Also the constant repeating on how to fix your noise issues.

I also remember discussing this same power issue with you in person.

[sourceoneaudio]

PA-5 SPECS:


Specs are as follows: Nakamichi PA-5 Stasis amplifier.

Continuous Average Power Output: 100wpc into 8ohms

Continuous Average Power Output: 160wpc into 4 ohms

Dynamic Power: 150wpc into 8ohms

Dynamic Power: 270wpc into 4 ohms

Dynamic Headroom: 1.7db into 8ohms

Signal to noise ratio: Better than 120db

Output current capability 12 amps continuous, 35 amps peak per channel...

Output Compliment: 10 transistors per channel.....

Power Consumption: 500 watts max

Approximate weight: 35lbs

Power Supply: 450 VA toroidial transformer


PA-5AII SPECS:


Specs are as follows: Nakamichi PA-5 Stasis amplifier.

Continuous Average Power Output: 150wpc into 8ohms both channels driven 20-20,000 HZ, 0.05% THD

Dynamic Power: 225wpc into 8ohms

Dynamic Headroom: 1.7db into 8ohms

Signal to noise ratio: Better than 120db

THD @ rated power 20-20,000 hz less than 0.05%

Output current capability 18 amps continuous, 70 amps peak per channel...

Output Compliment: 14 transistors per channel.....

Power Consumption: 650 watts max

Approximate weight: 47lbs

Power Supply: 470 VA toroidial transformer, 94,000 uf total filter capacitance


PA-7 Specs

Dimensions: 17-1/8 (W) X 7-7/8 (H) X 16-9/96 (D) inches Approximate weight: 59 lbs., 8 oz
Continuous Average Power Output (NEW IHF): 200wpc (8 ohms, both channels driven, 20-20,000 Hz, 0.1% THD)
Continuous Average Power Output 330wpc (4 ohms, both channels driven, 20-20,000 Hz, at no greater than 0.1% THD)
Dynamic Power per Channel: 300wpc (8 ohms)
Dynamic Power Per Channel: 550wpc (4 ohms)
Dynamic Head Room (NEW IHF): 1.7 dB (8 ohms)
Power Bandwidth (Half Rated Power, 0.1%
Damping Factor: (NEW IHF) 20 Hz/1 kHz/20 kHz: Greater than 60/60/60
Input Sensitivity/Impedance (NEW IHF): 2.0 V/ 75k ohms (rated power) 140 mV (1W output)
Frequency Response: (1 W, NEW IHF): 20-20,000 Hz + 0, -0.5 dB, 7-150,000 Hz +0, -3 dB
Signal to Noise Ratio (Input Shorted, Rated Power, IHF A-WTD) : Better than 120 dB Residual Noise Level (IHF A-WTD): Less than 25 u V/
Total Harmonic Distortion: Less than 0.1%
Intermodulation Distortion: Less than 0.1%
Stereo Separation (Input Shorted): 110/100/80 dB
Output Complement: 16 Transistors Per Channel
Output Current Capability: 18 A continuous, 50 A peak (per channel)
Power Supply: 700 W toroidal transformer, 132, 000 u F total filter capacitance
Power Source: 120, 220, 240 or 110-120/220-240 V AC; 50/60 Hz,
Power Consumption: 700 W max.


PA-7AII Specs

Dimensions: 17-1/8 (W) X 7-7/8 (H) X 16-9/96 (D) inches Approximate weight: 62 lbs. 13oz

Continuous Average Power Output (NEW IHF): 225W x 2 (8 ohms, both channels driven, 20-20,000 Hz, 0.05% THD)

Dynamic Power per Channel: 340 W (8 ohms) Dynamic Head Room (NEW IHF): 1.7 dB (8 ohms) Power Bandwidth (Half Rated Power, 0.05% THD Damping Factor: (NEW IHF) 20 Hz/1 kHz/20 kHz: Greater than 60/60/60

Input Sensitivity/Impedance (NEW IHF): 2.0 V/ 50 k ohms (rated power) 140 mV (1W output)

Frequency Response: (1 W, NEW IHF): 20-20,000 Hz + 0, -0.2 dB, 7-150,000 Hz +0, -3 dB

Signal to Noise Ratio (Input Shorted, Rated Power, IHF A-WTD) : Better than 120 dB Residual Noise Level (IHF A-WTD): Less than 25 u V/

Total Harmonic Distortion: Less than 0.05% Rated Power 20-20,000 Hz

Intermodulation Distortion: Less than 0.1%

Stereo Separation (100 Hz/1kHz/1okHz) (Input Shorted): 120/105/90 dB

Output Complement: 18 Transistors Per Channel

Output Current Capability: 20 A continuous, 90 A peak (per channel)

Power Supply: 700 W toroidal transformer, 132, 000 u F total filter capacitance

Power Source: 120, 220, 240 or 110-120/220-240 V AC; 50/60 Hz,

Power Consumption: 900 W max

[opimax]

Storm,

I wrote you a pm om my opinion which was the same as i said here publically and you responded.

2 things from your response struck me as ...different

the last you thing you wrote was "So I am I perfectly fine w/my Nak ? Do I need more power"

I then said to myself why did I write this ? a waste of time...

And lastly you also said something "I don't like startring a feud."

maybe not but I begining to think you really enjoy all this attention...

I'm done

Mark
And yes I could have pm'ed this but I think it should be here

[majick47]

Getting back to the 250ti that I had an opportunity to listen to, I forgot to mention that they were biamped, 420 watts for the low end and 250 watts for the top end for a total of 670 watts, both were Yamaha Pro amps. After 5 pages on this issue from what I'v read the majority opinion stated that you will benefit in many ways with a much larger amp. Even the few that were on the fence and didn't originally see the need for a larger amp have seen the light and now agree in principal if not practice.

[clmrt]

Maybe he needs less speaker.

[JSF13]

Even the few that were on the fence and didn't originally see the need for a larger amp have seen the light and now agree in principal if not practice.

I've always been a true believer of that principal. Unfortunately not always as easy as one would like,to put into practice.$$$

[jblnut]

That would be me . Sorry I'm late to this party but I don't seem to have a lot of free time these days. I no longer have the dual Yamahas powering my 250Ti's. I am now using some real sweet Dynaco Mark III's on top with the smaller Yamaha (260w) powering just the LE14H-1s. The move from transistor to tube was just what the doctor ordered. The max SPL might be down a few DB but the overall sound is smoother and more listenable, especially at higher volumes (which rock seems to demand).

I have tried smaller amps on the 250's and have always come away wanting more. I tried the Mark III's by themselves (full range) and the bass just withered and died. I have tried other transistor amps in the 65-120w range and also didn't feel they controlled the lows anywhere as well as the big Yamahas do.

I've still got the huge PC4002M gathering dust in my living room if someone wants to come over here, give me $400 for it and cart (wouldn't recommend carrying) it away. It'll rock your 250Ti's and your world like few other amps ever will.

jblnut

Getting back to the 250ti that I had an opportunity to listen to, I forgot to mention that they were biamped, 420 watts for the low end and 250 watts for the top end for a total of 670 watts, both were Yamaha Pro amps. After 5 pages on this issue from what I'v read the majority opinion stated that you will benefit in many ways with a much larger amp. Even the few that were on the fence and didn't originally see the need for a larger amp have seen the light and now agree in principal if not practice.