Let's look at a generally safe voltage and see the result.
36vct transformer (18+18vac) rectifies to about 26vdc rails
Here's for 8 ohm speakers with 90db efficiency:
1w, 90db
2w, 93db
4w, 96db
8w, 99db
16w, 102db
25w, 103.7db
However, if the speaker above were used in a format, such as dual woofers or MTM, it would become 4 ohms with 93db efficiency and return 106.7db. This now represents a 50w demand on the amplifier, and if it were operated at maximum for an extended length of time, it could come to harm. While generally safe for home use, it wouldn't be recommendable for PA/DJ use of continuous high power (it will quit working).
A solution:
Efficient speakers!
Here's for 8 ohm speakers with 95db efficiency
That's available as a typical "DJ" prosound woofer, popular with wedding singers and mobile DJ's.
And, they are available in 8 ohms.
1w, 95db
2w, 98db
4w, 101db
16w, 104db
25w, 105.7db
Good output running nice and cool because of 8 ohm speakers.
*The DJ speaker is larger, and with ported enclosure, may produce an additional 3db or more of bass output, as is the case with most larger speakers, thereby 108.7db may be realized from just 25 watts. Also, it is to be noted that a high-speed (high resolution lightweight cone materials) driver may produce more impact than a slow (heavy cone) driver.
One tip on the figures.
In a comparison of bass output, the textbook figures are off a bit. Let's compare LM1875 and LM3836 when considering their electronic dampening abilities (driver command). The difference between the 25w output and the 60w output can be different than expected because of the reported greater driver command of LM1875 (higher resolution bass). This is not unusual for lower powered amplifiers when compared to higher powered amplifiers.
The secret to giving LM1875 an advantage over the higher powered systems is the 8 ohm 95db prosound woofer with a light, high-speed cone. The combination of very good driver command (amp that moves woofer faster) with a naturally faster and more efficient woofer in a ported enclosure, can give a high-resolution bass with considerable output.
I think that most owners of high-end, lower power, amplifiers are usually doing a little more woofer shopping than normal; however, the results of that combo are usually high resolution audio.
See also examples of speakers that work well with the smaller Tripath (T-amp), probably over at the class-D forum--If a speaker is doing HT duty on just 7 watts, then it could do even better with your LM1875's 25 watts. We probably shouldn't tell them.
36vct transformer (18+18vac) rectifies to about 26vdc rails
Here's for 8 ohm speakers with 90db efficiency:
1w, 90db
2w, 93db
4w, 96db
8w, 99db
16w, 102db
25w, 103.7db
However, if the speaker above were used in a format, such as dual woofers or MTM, it would become 4 ohms with 93db efficiency and return 106.7db. This now represents a 50w demand on the amplifier, and if it were operated at maximum for an extended length of time, it could come to harm. While generally safe for home use, it wouldn't be recommendable for PA/DJ use of continuous high power (it will quit working).
A solution:
Efficient speakers!
Here's for 8 ohm speakers with 95db efficiency
That's available as a typical "DJ" prosound woofer, popular with wedding singers and mobile DJ's.
And, they are available in 8 ohms.
1w, 95db
2w, 98db
4w, 101db
16w, 104db
25w, 105.7db
Good output running nice and cool because of 8 ohm speakers.
*The DJ speaker is larger, and with ported enclosure, may produce an additional 3db or more of bass output, as is the case with most larger speakers, thereby 108.7db may be realized from just 25 watts. Also, it is to be noted that a high-speed (high resolution lightweight cone materials) driver may produce more impact than a slow (heavy cone) driver.
One tip on the figures.
In a comparison of bass output, the textbook figures are off a bit. Let's compare LM1875 and LM3836 when considering their electronic dampening abilities (driver command). The difference between the 25w output and the 60w output can be different than expected because of the reported greater driver command of LM1875 (higher resolution bass). This is not unusual for lower powered amplifiers when compared to higher powered amplifiers.
The secret to giving LM1875 an advantage over the higher powered systems is the 8 ohm 95db prosound woofer with a light, high-speed cone. The combination of very good driver command (amp that moves woofer faster) with a naturally faster and more efficient woofer in a ported enclosure, can give a high-resolution bass with considerable output.
I think that most owners of high-end, lower power, amplifiers are usually doing a little more woofer shopping than normal; however, the results of that combo are usually high resolution audio.
See also examples of speakers that work well with the smaller Tripath (T-amp), probably over at the class-D forum--If a speaker is doing HT duty on just 7 watts, then it could do even better with your LM1875's 25 watts. We probably shouldn't tell them.
BWRX said:
That comment was "in general" and of course that leaves room for exceptions. However, quite often when amplifiers are reviewed in actual performance conditions, its the lesser amplifiers that perform greater on controlling the woofers (electronic dampening).
EDIT: Consider the tiny difference in decibels between 25w and 60w, and then consider how largely any difference in dampening could close that gap--mostly for 45hz area signal (the typical lower pitches of popular music as indicated by the O.P.). In fact, this was demonstrated and reproducable errata.
This was offered as a (very generalized) explantion to help understand the people who declare that they prefer the lower powered amplifiers over the higher powered amplifiers as a matter of quality. Although there's a variety of reasons, the "why" will basically relate to speakers, which are required.
Both concerns were mentioned by the O.P. and I quote: "can't leave it when love it"
It has little to do with the amplifier itself, but rather relates to the use of it. Do please bear in mind that we're talking about an "audio" amplifier for music, and, necessarily, music has not been amplified (circuit is not complete) until the job is done, as in the signal has reached an ear.
Testing model:
You have the opportunity to try it for yourself. Just select very underdamped speakers, sealed box type, and play music with very low notes. That should make driver command more-easily observable during testing. Try different amplifiers. Check out the difference in performance.
Documentation:
Review Peter Daniels discussions on "difficult to drive" speakers versus perceived bass output with relation to differences in amplifiers. He doesn't mention power ouput as a factor, but does mention that the issue exists as a difference in amplifiers.
A trick:
And, yes, there was a trick involved. Here it is. By shopping for highy efficient drivers from the prosound market, the only selections available are very well dampened speakers. Of course the efficiency will help the small amplifier; however, the well dampened speakers will work very well on the higher powered amplifier. So, both problems turn up missing.
Either way, it seems that some efficient prosound woofers (8 ohms) will be a nice solution.
Documented application:
As the requirement is high output for popular music with a concert-realist rendering, it is well documented that there is no better solution than to use authentic performance speakers.
So, my answer does have an application. If you have a better answer, now is a good time for it. That would be quite welcome.
Daniel, I'm not sure why you feel the need to come up with an explanation for general observations. This leads you to make false claims and is counterproductive.
Damping factor (driver command as you keep mentioning it) is amplifier and load dependent, not power dependent. You keep generally stating it's the "lesser amplifiers that perform greater on controlling the woofers (electronic dampening)" BUT you are incorrectly assuming that higher power amplifiers have worse damping factors. The higher powered amp in question could very well have a higher damping factor than the lower powered amp which could result in you hearing tighter, more controlled bass. My point is that you need to look at specific amps if you want to derive any kind of meaningful results.
You don't need a big test setup to test this out for yourself. All you need to do is place a low value power resistor (usually less than the impedance of the speaker) in series with the output of your amplifier. Viola, you have just drastically lowered the damping factor of the amp. Keep in mind this is nothing new and there should be plenty of information about amplifier damping factor around here and the web in general.
Your proposed "trick" is nothing new either. Of course highly sensitive speakers will play louder with less power, that's just physics. The thing about pro sound drivers is that they are meant to play very loud AND handle a lot of power. Most hifi drivers were not designed with the same goals in mind.
Damping factor (driver command as you keep mentioning it) is amplifier and load dependent, not power dependent. You keep generally stating it's the "lesser amplifiers that perform greater on controlling the woofers (electronic dampening)" BUT you are incorrectly assuming that higher power amplifiers have worse damping factors. The higher powered amp in question could very well have a higher damping factor than the lower powered amp which could result in you hearing tighter, more controlled bass. My point is that you need to look at specific amps if you want to derive any kind of meaningful results.
You don't need a big test setup to test this out for yourself. All you need to do is place a low value power resistor (usually less than the impedance of the speaker) in series with the output of your amplifier. Viola, you have just drastically lowered the damping factor of the amp. Keep in mind this is nothing new and there should be plenty of information about amplifier damping factor around here and the web in general.
Your proposed "trick" is nothing new either. Of course highly sensitive speakers will play louder with less power, that's just physics. The thing about pro sound drivers is that they are meant to play very loud AND handle a lot of power. Most hifi drivers were not designed with the same goals in mind.
BWRX said:
Yes, that's it. The difference does exist. When its mentioned, its generally (very generally) often in favor of lower powered amplifiers. Hmm. . . The data is shoddy at best, but its the data that exists.
However, the O.P. experienced this very same errata on identical builds between LM1875 and LM3886. And, so did I.
Hey, did you ever buy one of those little Tripath from Sure? Although they do vary in manufacture, it really made quite a lot of bass from sealed-box speakers that had never been able to output clarity at the lowest pitches. I had the Sure on 14v. Even so, its a weakling. My 80w amp could blare so much louder, but couldn't touch the Sure for very low bass. So, there's another of many examples.
This relates directly to the Fletcher-Munson tables, because the ear has great difficulty with the lowest of pitches. Thus, even a slight improvement. . . if that's enough to cross the threshold. . . will be seen as incredibly dramatic although not typically addressed by electronic measuring equipment.
This is often (generally) realized when the woofer moving faster--not dropping bass detail.
See attached chart.
Really, any of the lower power examples that demonstrate this are somewhat of a cruelty. I say that it sounds fantastic, so you want to REALLY turn them up. . . and its a no-go.
This was also mentioned by the O.P.
Is Hypex one of the exceptions?
A last example is my mistaken treatment of a high-efficiency woofer in adding a resistor to it (to level the mids). The LM1875 didn't fail to maintain the electronic dampening, so I was unware that the resistor was a mistake. . . until I plugged in a different amplifier. EDIT: Perhaps I should have added a large 20ga inductor to that resistor, as in a BSC. What do you think?
On reviews, they are typically hi-fi genre, and they are typically without equalizations. As the chart below demonstrates, any relief from that very large error, is seen as dramatic.
Attachments
danielwritesbac said:
Shoddy is an appropriate description for the "data" (more like anecdotal evidence).
danielwritesbac said:
What does O.P. stand for?
Identical builds? You seemed to have some sort of oscillation problem with one of your amps if I remember correctly. Doesn't sound like it was properly implemented at all, leading to a less than fair evaluation.
I have an insanely dumb question here. but what qualifies as identical builds for those two chips???? Do you mean that you used the same circuit topology? This would, of course, not product "identical builds" since you would most likely use different components and/or different circuit boards that, according to your (Daniel's) makes a HUGE difference, at least regarding PSU caps!
IMHO, in order to qualify as an "identical build," one would have to use EXACTLY the same parts in both, have as similar PCB layout as possible (which gets dicey in a hurry, but let's run with that for a second), use the same physical layout in the chassis, and have exactly the same operating environment. Did all of this happen for the "identical builds" in question?
All of this begs the further question, why in the world would you ever build circuits around each of those chips with identical parts?!
IMHO, in order to qualify as an "identical build," one would have to use EXACTLY the same parts in both, have as similar PCB layout as possible (which gets dicey in a hurry, but let's run with that for a second), use the same physical layout in the chassis, and have exactly the same operating environment. Did all of this happen for the "identical builds" in question?
All of this begs the further question, why in the world would you ever build circuits around each of those chips with identical parts?!
BWRX said:
O.P. Original Post'er
Hi Brian! I think that we're on the same "station" albeit slightly different viewpoints. I'm saying "mostly agree" and I have great respect for you.
I too, have some trouble with hifi reviews, and its because there are no room/ear accomodations in the audio chain, so that the end result is compromising clarity by performing many component selections based on frequency response--and that most certainly isn't high fidelity as claimed.
Avoiding the use of an RC against the path of an audio signal is understandable, but surely there are equalizations that don't harm resolution?
However, the "driver command" topic is more firmly grounded than usual for a hifi topic. OMG!! No pun intended!!
Anyway, in this, we can witness a loudspeaker otherwise unable to produce significantly loud and clear 45hz output. . . suddenly doing exactly that, depending on the amplifier used.
I think that it explains the O.P.'s preference for the smaller amplifier--because, if that's not the case, there would be no other easily-verifiable reason to choose LM1875 over LM3886 for playback of loud techno.
And, no I don't currently have an inappropriate amplifier except for the one that I emailed you about. That crazy little circuit (an unfamilar equalization) is currently on a TDA7294, and currently causing it to "mimic" the low bass output of LM1875, via an unrelated means.
Although that little unknown circuit is an "effect," its that same "must crank it up" sound--great impact at the lowest pitches, while the signal remains clear. The difference is that there's an easy 100 watt application for TDA7294, which is currently rocking down the house at this moment.
I sure wish you'd check your email
danielwritesbac said:
This is what I have a problem with. If you hear a really noticeable difference then the two amps have different frequency responses or some other difference that may not necessarily be attributed to the chip the amp is based around. You need to compare apples to apples. I'll give you an example. I have my LM3875 based amps and a 41hz amp3 both on my desk with ~90dB@1W/1m 8ohm 2-way speakers. I've switched between the two amps and they sound pretty similar when keeping the volume within the limits of the amp3. The LM3875 has equally good "driver control" (if not better, actually) even though it is capable of quite a bit more output power. The LM3875 is DC coupled and the Tripath amp is AC coupled but the high pass cutoff should be around 4Hz which is well below what my monitor speakers can do.
Does this mean your "theory" is out the window? No. It means your observations are only valid for specific amps, which in your case would be LM1875 and LM3886 based. You should dig further to find out why you're getting those results instead of declaring (and with a lot unfounded assurance I might add) that lower powered amps like the LM1875 have better "driver control" than higher powered amps like the LM3886.
dfdye said:[sarcasm]Wait, you mean that "Class D Disciple" moniker didn't just magically appear after you posted your 3000th post??[/sarcasm]
The original SI T-amp is actually what got me interested in learning more about audio electronics.
eketehe said:can not do that daniel, can't leave it when love it
Good news!
Thanks to Brian, BWRX, we now have twice as many options as before.
He has compared his LM3875 at www.transientharmony.com to the venerable Tripath inside a competitive observation. To me, that means that his amplifier will provide the sound you're looking for, with the additional power you're looking for as well. And it is a complete amplifier, not just a power amp module by itself.
He also has a similar LM1875 in development.
Answers:
Efficient, 95+db, 8 ohm speakers for your LM1875
and/or
Amplifier, LM3875 with preamp, at http://www.transientharmony.com
Thanks guys!!
P.S.
Any of the topic of "sounds like" is a bit of a guess for me, but I'm fine with that as long as the heading is forwards, in the general direction of progress.
However, in Brian's case, you can bet that there was no guesswork whatsoever.
dfdye said:
Identical builds were compared by two seperate people (four amplifiers total--both LM3886 and LM1875 per each person). One was an "open wire" and the other was a "E-board" (phenolic with pads). In both cases, textbook examples were tried, and exact same components were tried; and then later, the power circuits were fine tuned for individual amplifier requirements, which helped somewhat. As for myself, I have not used an LM3886 since after this experiment.
A re-visit to that chip, for me, is planned after I re-locate my shop and after the rest of my preamp materials arrive. Its probably going to be a few weeks, and I need to be well-prepared.
[-------- <cat typing.
danielwritesbac said:
How do you know it will provide the sound he's looking for without even having heard it? Maybe someone with better ears could hear differences I couldn't. I don't know but what matters is that it sounds good to me! My comparison of Tripath vs LM3875 was pretty quick and not very thorough, so don't go taking it as gospel.
BWRX said:
Your LM3875 is differential input with preamp, is it not?
On the test for driver command, you did compare the 45 hz (or so) output with sealed box speakers. Is that right?
The Tripath are hard to beat on driver command, that just happens to give the required help to popular music. So, if your LM3875 was anywhere close. . . then its quite probable.
Its a case of whatever is closest to meeting the requirements, and your design contains several other aspects that I believe to be helpful.
There is a question, though. Did you use them (yourself) as monoblocs (two transformers) or a stereo pair (one transformer)?
Dear All,
i have read em' all,
Sorry for so much riots. i'm a 'zero zero ufo' audio and electronic back ground
. lets stop more anecdotal evidence.
there's a bad 'technical subtittle' problem, since only less thing i understand.
However, i'm having somuch fun and experience, thank you,
since i start this thread, seems i become have a lot of 'audio bussines and intend to what related, here and my place.
after office hour will be my audio audio hour
i did so much hearing, there was some friends, some family, with their hi - fi, which i was also sitting in their listening room, enjoy the music. and i shows my project.
their impression become a spririt. i'm not saying i'm at their level, but the last little LM project 'winking' low cost really make em' jealous.
the econominal reason just making easy to edging this chipamp with some experimental, unlike my previous lm3886, burn some of em' won't make me too much poorer.
please don't misunderstand, i'm not a 1875 fanatics, i still have 4 3886 ( 2 in the pcb ), they will be my next bigger project, maybe for outdoor activities their just too big for home usage ( i think )
'i'm achieving a better hearing'
here is my post few weeks ago,
thats was a different person.
i still runs for more better hearing, and my the also 'best' project left, theres a lot of things i intend to collect.
i also have other thing in urgent within this weeks
Thanks all, and for daniel goodluck with the new shop, see you guys later.
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