Studio Monitor Tweeter Hiss (JBL LSR305, KRK Rokit 5 G3, Etc.)

[JCJR]

I get a little confused because I tend to be looking at amplifier classes as school grades.
The benefits of type D sound actually pretty nice (weight/heat/etc.) but if they are only benefits for larger wattage amps as @annode I believe is mentioning, then that would mean that those amps are chosen for more cost issues, that is disappointing, slightly understandable, but still disappointing.

Hi Mike

I don't know one way or the other whether class D advantages are only for high power applications.

When factoring cost, and going super-cheap-as-possible on a product, it would be possible to cut so many corners on Class AB that the amp would suck as bad or worse than a badly-made Class D.

JBL is a good company. I think if the engineers thought they could make a better product at that price point with class AB amps, then they would probably have used class AB amps.

The price of LSR 305 and 308 is insanely low. I auditioned 305, 308 and HS7 a couple of years ago at a music store. I couldn't say for sure unless I could spend a month or three with the speakers at home. The acoustics were bad in the store and the salesman was annoying and I didn't want to take up too much of his time because it was a curiosity audition rather than intention to buy.

However based on that quick audition, I liked the 308 best and suspect that there were good odds that it would sound at least as good as my old 8" passive JBL 2-way speakers with the old JBL-Urie power amp. Maybe at home, AB compared against the old passive JBLs, the 308 might sound lots better. Or maybe it would sound noticeably worse, but I doubt that.

There was no way to know without installing 308's at home to find out. The price is insanely low for the audio quality, but I figured that if the 308s would only be "about the same or somewhat better" than what I already had, then it wouldn't be worth the money to me even if the price/quality ratio is fantastic.

At that price and fidelity, if the tweeters hiss a little bit it wouldn't bother me in the least, so long as the hiss isn't "niagra falls" loud. Everything in the audio chain hisses, so it wouldn't be completely silent in practice even if the speakers happened to be dead-quiet with a shorted input plug.

This is not a "low power class D" example, but Barefoot Sound uses class d on many of their powered speakers. Maybe all of em, haven't studied on it. Some of the models use Hypex class D amps, but maybe some models use other-brand class D, dunno.

http://barefootsound.com/

Just sayin, if I was gonna buy a pair of powered speakers at the price of a new car, it is real likely I'd buy some barefoots. If Mr Barefoot happened to think that some other amp design would sound better, then with that "who cares about the price" design attitude, he would probably have picked class A tube or class AB mosfet or whatever he thought would be better.

But just because there are some nice class D doesn't mean all of them would be nice.

[BertKoor]

As far as using two passive speakers and amp, I looked around and oddly couldn't seem to find any 5" passive studio monitors.

That's odd... I visited bax-shop.nl (one of the local web shops with musicians gear) searched for passive monitors and the first result was the Behringer 1C-BK which has a 5" woofer. Some other interesting finds in that category:
* JBL Control 1 Pro
* Avantone Pro MixCubes (Passive Buttercream v1)
* KRK R6 G3 (passive, slightly larger)

Note that personally I'd set the minimum size at 6.5" instead of 5". Simply because I don't trust 5" to deliver enough bass.

Also I wouldn't know how to pair an amp with the speakers and would imagine that between the monitors and a pretty good amp, it would probably be pretty expensive for me.

It depends on your budget. I think you can get a simple but decent stereo amp for around $100. That is also roughly the price difference between active and passive monitors.

Ahem, just looked up price difference between the passive KRK R6 and active RP6: difference of €32 a piece, so €64 for the pair. Big bonus for a seperate amp for me is: just one volume knob and one thing with mains power.

Also active monitors also I believe power the speaker and the tweeter separately, not sure how a separate amp would handle it.

Active monitors are usually indeed bi-amped. Passive monitors have a passive cross-over mounted inside. Just feed it a hundred watts full range, and the cross-over will split it in a signal for the tweeter and for the woofer.

[JCJR]

BertKoor gives good advice.

I'm prejudiced toward "at least 8 inch woofers" but tis a matter of taste.

Some older, bigger 3 way speakers might have a 12" woofer, a 4" or 5" midrange, and tweeter. If a person intends to use one or two subwoofers which are capable of working good a little higher than usual-- Then in that case a nice 5" two way monitor, when working with the subwoofer, might be a similar configuration to such as the old JBL 3 ways. The most recent JBL 3 way in that family being LSR 6332-- http://www.jblpro.com/ProductAttachment ... SR6332.pdf

Uses 5 inch midrange crossed over at 250 Hz (tweeter crossed over at 2.2 kHz). Over the decades JBL typically used 3" to 5" mid speakers on that kind of product. Maybe it is "superstitious thinking" but for a three-way monitor, if JBL thought a 6" or 8" speaker would have worked better on mids, they wouldn't have used smaller speakers.

Was just thinking that a nice enough 5 inch two-way monitor could POSSIBLY be "the best pick" if one intends to pair them with front-firing subwoofers capable of working up to 250 Hz or whatever. Maybe the 5 inch monitor could have "better mids" than 6 or 8 inch monitors, if we don't expect the speaker to carry bass?

The most typical "home theater" subwoofer crossover is 80 Hz. I suppose 80 Hz would work good enough with decent 5 inch monitors, but maybe with the proper subwoofer it would work better crossed-over a bit higher?

"Theoretically" I've been concerned with doppler intermodulation distortion when a woofer is expected to carry both bass and mids (as with most two-way monitors). For instance if we feed the woofer a mix of 2 sine waves at 50 Hz and 500 Hz-- The 50 Hz makes the cone move forward-back 50 times per second. The 500 Hz moves the cone forward-back 500 times per second. So the 500 Hz tone moves the speaker forward-back 5 times while the 50 Hz moves the cone forward, then the 500 Hz tone moves the speaker forward-back another 5 times while the 50 Hz moves the cone backward.

The doppler effect is the reason a train or car horn is high-pitched moving toward us, and low-pitched moving away. And the reason spinning leslie speakers create vibrato.

So the high tone gets pitch-shifted up half the time and gets pitch-shifted down the other half of the time, and the pitch shift direction changes 100 times per second.

That doppler intermodulation must not be "ridiculously unpleasant" or nobody would be able to tolerate listening to 2 way speakers. On the other hand, a three or four way system would have less doppler intermodulation than a 2 way system.

When I was daydreaming about possibly trying a 5" monitor with subwoofers, the 5" monitors I'd have been willing to pay for, seemed POSSIBLY a bit too under-powered to keep up with 12 inch or 15 inch subwoofers.

Usually if you set out to build a three-way system, you make the tweeter strong enough to keep up with the big woofer. But if you set out to build an "affordable" 5 inch two way, not wanting to waste money installing more tweeter than necessary, one would only need a tweeter strong enough to keep up with a small woofer. So maybe with affordable mainstream small monitors, it wouldn't work so great in practice.

OTOH, with the LSR 305 vs 308-- Maybe the 305 tweeter is a different part than the 308 tweeter but I'd wildly guess it might be the same part. Economies of scale and easier inventory management. The 305 tweeter amp is 41 watts and the 308 tweeter amp is 56 watts. If both speakers have the same tweeter, then the 305 tweeter's max clean output ought to only be -1.35 dB less than the 308 tweeter. So maybe coupled with a sub, there would be not much noticeable difference between 305 and 308, except that the 305 might have cleaner mids than the 308, after being relieved of the task trying to reproduce bass.

[VitaminD]

I'm going to up this thread knowing it's old. I am discovering something now I never considered.. some monitors hiss.

I bought some Kali LP-6 monitors that arrived today and have noticed the tweeters hiss pretty loudly. My previous budget monitors from a different brand did not in the same setting. I know the LP-6 was designed by former JBL staff, so I'm guessing they're "enhanced" LSRs (which also seem to hiss from the posts here). I guess it is cheap amps on the tweeters?

That sound is driving me nuts. Constant but soft chhhhhhhhhhhhhhhh sound.

[annode]

When inputs are removed you shouldn't hear anything really.

[BertKoor]

When inputs are removed you shouldn't hear anything really.

Well, with inputs disconnected you only hear the noise generated by the amp, inherent by its design. "Shouldn't hear anything" assumes it's design is optimal (which it more often is not)

[annode]

Yes. I see it uses a class 'D' amp design. I'm no engineer but it seems to me after reading about them @ Wikipedia, internal noise is dealt with through a low-pass filter by design.Just a guess, but it's 25khz upper end may be a clue that the filter is letting noise through.

Second, this design relies heavily on internal feedback looping for several reasons. This means to me, a way of developing hiss in the signal.
If the speaker generates the hiss without being connected to a source, you can expect this is in the design.

[VitaminD]

Yeah it is just the design - I emailed support for Kali they responded, saying it is 'normal.'

Trying to RMA them right now.

[VitaminD]

Yes. I see it uses a class 'D' amp design. I'm no engineer but it seems to me after reading about them @ Wikipedia, internal noise is dealt with through a low-pass filter by design.Just a guess, but it's 25khz upper end may be a clue that the filter is letting noise through.

Second, this design relies heavily on internal feedback looping for several reasons. This means to me, a way of developing hiss in the signal.
If the speaker generates the hiss without being connected to a source, you can expect this is in the design.

This is the lesson. Class D amps seem to be prone to hissing. At least on the lower end monitors.

Class A/B designs seems to be less prone to hissing.

https://www.soundonsound.com/techniques ... cation#top Sound on Sound article goes into the details a bit.. as well as laying out a few of the flaws of Class D amps.

Looking at reviews for sub $500 monitors now and directly focusing on hissing/hiss as keywords I see a trail of complaints on the Class D amp using monitors and none on the A/B style.

The LP6's were so hissy to me at 2 feet away that I literally thought it was raining outside before I realized it wasn't -- it was the tweeters hissing! haha

[EnGee]

I'm still very happy with the Yamaha HS7. If they fail/get damaged for any reason, I would buy them again or HS8.

Recently I noticed they even reduced the price in general here in NZ (maybe in other parts of the world!). So, now the HS8 cost the same as the HS7 when I purchased them, so for me, I would go even with more bass than HS7 if possible

[annode]

VitaminD wrote;

The LP6's were so hissy to me at 2 feet away that I literally thought it was raining outside before I realized it wasn't -- it was the tweeters hissing! haha

I can hear that in my mind's ear from that description. With any common audio receiver you don't get that until you crank it up to 6 or 7.With a music signal input at 6-7, it would be considerably louder then 85db, (the average RMS of the LP6) I am guessing. That hiss from common audio amps cranked half way up or more, is from the transistors becoming more and more saturated with bias current. This effect increases the gain of the upper-midrange as if you had a peaking bell curve in an EQ upper-mid.
This of course isn't what's going on in the LP6 since the signal out remains flat.

It's really strange to me Kali (and other same designs) don't make note of this effect. It is noise (SNR - signal to noise ratio) no? If the noise doesn't follow the signal gain, then what is it?

[AlesisVi61]

If anyone else has any more monitors to comment on please do so, also still looking for people to comment on the Presonus and KRK 4s. I would imagine if the KRK 5s and 8s hiss then the 4s would be no different but still interested in hearing what people have to say.

Again I know this is not a huge deal, just something to discuss a little.

Thanks Again to everyone that has commented.

I recently bought a Presonus 2.1 set up(a pair of Eris E44's and a T10 sub) and it's dead quiet!Very impressed with my purchase(finally,a full range monitoring system that's super clean,with impeccable clarity....all for only $734!)
In fact,this set up beats out my old pair of Adam Audio A7's and those were $1,000 for the pair!

[Johnny!]

My Adam Audio T5V monitors hiss just a little bit too, but it's unnoticeable in unless you put your next to tweeter.

BTW - I recently went to my local music shop to get a listen and possibly buy KRK RP6 G3, they've got also RP5 G3 in the test room and those Adams, and T5Vs totally blew me away. They sound better without the need to crank the volume up. Got the Adams instead

[annode]

Presonus 2.1 set up(a pair of Eris E44's and a T10 sub) and it's dead quiet!

The amplifier technology appears to be conventional Class A/B, with traditional linear power supplies. ("S on S") That explains the lack of hiss.

I wrote just above;

It's really strange to me Kali (and other same designs) don't make note of this effect. It is noise (SNR - signal to noise ratio) no? If the noise doesn't follow the signal gain, then what is it?

This turns out to be called 'self noise'.
https://www.sweetwater.com/insync/self-noise/