advertisement


5-10k ish Speakers

I've just enjoyed spending the last 45 minutes reading through this thread and laughed out loud many times. I take my hat off to you! I started to thank each of you by name, but didn't want to leave anybody out. You guys are hilarious! Really, brilliant! ;>))

I humbly suggest the OP track down the following, with the caveat that they may not fill his room with thunderous sound pressure levels. But they have a contemporary appearance, sound fantastic and should be well within budget, especially if purchased used:

quad 988, 989, 2805 or 2905.

BTW, I haven't heard most of the other speakers mentioned on this thread.
 
cooky1257 said:
So Mr Physics, inverse square law beyond you is it?;-)

I'm sure the Obelisks are very nice loudspeakers, here's their specs;

Bass driver voice coil 1.5"

Power handling: 200W max

Frequency Response: -3dB/28-18,000 Hz

Nominal Impedance: 6 ohms.

Sensitivity: 89 dB

Dimensions: 15” x 13” x 30”

Finish: Oak, Walnut, Cherry, or Rosewood
Weight: 50 lbs.
Click to expand...

Hi Lend-me-your-comb,

No not at all. I did quantify that I deliberately ignored it! Firstly because it applies in an anechoic environment like being in the middle of an open field and then from actual measurements taken in my circa 250sq ft room and I also added the room 'gain' which is unknown but at least +6dB. I think you have glossed over them or perhaps didn't understand.

Those specs for the Obelisk btw haven't been changed in donkey's years and from listening I believe the new speakers far exceed them.

TBH I don't think that the inverse square law applies to speakers. It assumes fields radiated from a point source as per a sphere. However assume a simple speaker with a tweeter, squawker and woofer and the radiation pattern would more approximate to a cone. Thus there would be a lot more energy going forward towards the listener than in the 360 degree model.

Also don't forget that I actually measured the SPL from the quasi-omni directional speakers in my room and was quite frankly amazed that the isr didn't apply.

Its got nothing to do with my speakers or anything else being 'nice'. It is however about getting good and realistic music within the confines of our room and also what fits in with the rest of my family. That is one of the reasons that I have yet to upgrade my vinyl front end. Most of the very good stuff looks utterly crap. I have earmarked circa £15K but I want good performance with an acceptable WAF.

I reiterate that I am only offering the OP advice as to what he could audition based on personal experience. We all perceive things differently and my view changed dramatically in my youth once I had my own band. Since then I only want a 'live' performance 'sound'. Others may prefer the 'canned' studio sound but thats not for me.

Cheers,

DV
 
Darth Vader said:
TBH I don't think that the inverse square law applies to speakers. It assumes fields radiated from a point source as per a sphere. However assume a simple speaker with a tweeter, squawker and woofer and the radiation pattern would more approximate to a cone. Thus there would be a lot more energy going forward towards the listener than in the 360 degree model.
Click to expand...
No, that'll be because you have at least six reflective surfaces in your room.
 
James said:
No, that'll be because you have at least six reflective surfaces in your room.
Click to expand...

And thats the room 'gain'. That first hit me as a kid with my band. Suddenly we were performing in open air concerts and our Vox AC30s and Ampeg bass amps just couldn't do it..........The sound just 'disappeared!

Indoors we filled very large halls at high SPL but this was a long time before 'discos' and ear splitting SPLs.

Cheers,

DV
 
I really must put this bullshit to bed.

Dynamic drivers have motor systems that couple to moving diaphragms. The motor is capable of exerting force proportional to input voltage and current drawn. The motor and diaphragm combined has mass. F = m*a. Therefore, more force or less mass means higher acceleration. All things being equal, a driver with half the moving mass or twice the motor strength will be capable of accelerating from rest twice as fast. Just as a car with twice the power or half the weight, assuming the chassis and transmission are up to the task, will accelerate twice as hard.

Consider then a 15" woofer and a 8" woofer. Let's assume they have the same motor system, and assume that the 15" woofer has 80g moving mass and the 8", 40g (which are typical). The 15" woofer will have a radiating area of 800 sqcm, whereas the 8" has 200 sqcm. To displace the same volume of air, and therefore create the same SPL, the 8" woofer will have to excurse 4 times the distance compared to the 15".

So while the 8" woofer is capable of accelerating (and stopping) twice as fast, it needs to cover four times the distance. Doubling the acceleration halves the time needed to cover the same distance, but in this case of four times the distance, the 8" woofer actually needs to have four times the acceleration to produce the same SPL.

The limits of acceleration in a dynamic driver dictates how high in the frequency range it can go. This limit is attributable to diaphragm rigidity, moving mass, motor strength and electrical inductance, to name the obvious. To all intents and purposes, the human ear will not hear the difference in acceleration between the 8" and 15" woofers when driven properly and within their operating envelopes.

To finish off with another motoring analogy, the 15" woofer is like a car and the 8" woofer is like a motorcycle. Imagine them zig-zagging through a set of chicanes, except that the motorcycle has to zig-zag four times the width than the car. At some speed, which equates to frequency, they will reach their limits. Whilst the motorcycle can accelerate faster, it won't be difficult to imagine that the car has the easier task with much shallower chicanes, and will in, in all probability, deliver a higher terminal speed.

That's also why bigger drivers tend to be more efficient.
 
Fast and slow woofers - can you tell which one's "fast" if you feed them through a 400Hz low-pass filter?
 
fox said:
Yes but you don't have the sizes of room being discussed; taking a post out of its original context isn't really going to work here.



You forget to mention room height. Which is kinda important when determining room's air mass and volume displacement -- depending on the SPLs needed -- also not mentioned.
Click to expand...

I left details out because I wasn't really commenting on the OP's situation so much as mine;-)
 
NIce post James.

The summary is that good speakers tend to have a constant (large) volume velocity output characteristic.

- but basic physics might get in the way of a good bunfight...
 
Darth Vader said:
Well this thread has been well and truly crapped upon and a lot of rubbish has been spouted forth by the most vocal. Some of you lot ought to be in marketing or politics........

Back on topic.

Lets work backwards. Here are some SPLs of different types of music:-

New age: 60-70 dB
Folk: 75-90 dB
Jazz: 80-95 dB
Classical: 100 dB
Pop: 90-95 dB
Rock: 95-110 dB
Heavy metal: 110 dB

The SPL meter was set to C-weighting, slow response.

Assuming that you want 110dB and with speakers of 85dBwm then that equates to 160w amp per channel. Music also has transient peaks of circa 6-25dB. So if you want to be able to handle say a 10dB peak then you'll need 1600wpc. Thats what I use for my speakers.

I haven't included a calculation for a distance greater than 1m because there will also be room gain due the reflected waves (reverberation) that may add 6dB or with glass even more.

In addition although I have only taken qualitative measurements in my room I have found that with these quasi-omni directional Shahinian speakers that the SPL is rather uniform but noticeably increases close to the walls.

Also note that I do not mention speaker size as it is rather irrelevant in such a small room of 1000sqft. If the speakers are well designed with a flattish and well extended frequency response and can take the input power needed then they will work well and fill the room.

I don't see the 'volume' of air as that important for home use. Sound waves are compression waves travelling through a fluid. I used to demonstrate this with a Slinky spring. Get someone to hold the far end and give the other end a push. You will see the compressed wave travel up the spring and then reflect back down. Also standing waves can be formed in the Slinky by pushing one end at the correct frequency so that reflected waves are in phase.

Cheers,


DV
Click to expand...

Presumably these figures relate to live performance?

Few people want to reproduce music in their living rooms at 'live' levels - particularly for the stuff at the higher end. For the few that do, eviction beckons.
Within the confines of a listening room, and given the close listening proximity, such levels can be extremely uncomfortable and even damaging to hearing.

The vast majority of hi-fi buyers on this forum and others will have spent their lives enjoying music played on loudspeakers rated at around 86dBw driven by by amplifiers ranging between 25-100w - with no problem whatsoever.

If you want to squeeze the concert hall into your 14"x20" listening room at truly realistic SPLs then go buy a kW amp or 100+dBw loudspeakers.
Most people simply don't want or need this.
 
James said:
Doubling the acceleration halves the time needed to cover the same distance
Click to expand...
Assuming no starting velocity, d(istance)=a(cceleration)*t(ime)*t(ime)

Doubling the acceleration reduces the time by a factor of sqrt(2), i.e. by 30 percent.
 
The vast majority of hi-fi buyers on this forum and others will have spent their lives enjoying music played on loudspeakers rated at around 86dBw driven by by amplifiers ranging between 25-100w - with no problem whatsoever.
Click to expand...

Erm, no problem if they're listening exclusively to compressed music (heavy metal, e.g.) at a modest average level at three meters or less with those 86 dBw (at 1 m) speakers.

But lots of music has very significant dynamic range, and 100 watts won't cut it with 86 dBw efficient speakers at common listening levels and listening distances. A measured crest factor for recorded music of 20 dB is not unusual, and 30 dB is possible with live acoustic music.

A 20 dB crest factor means that the 100 watt amplifier is clipping badly at an 80 dB average listening level at 3 meters into those 86 dBw speakers. A 30 dB crest factor and those speakers need over 2 KW at a 3 meter distance for an 80 dB average.

People listening to little, inefficient speakers often fail to realize just how badly their system is compressing their music, until they hear the full dynamic range properly reproduced on large, efficient speakers.

However, I completely agree that just listing SPL levels for different music types is meaningless. In fact, I'd say that the list Darth Vader posted is nearly inversely correlated with speaker efficiency and power requirements. Rock and heavy metal is heavily compressed, with a crest factor as small as 3 dB, while classical music can approach 30 dB and is hence much more demanding on a system (unless you listen at very low average levels. 25 watts is just enough at a 70 dB average level (which means the quiet bits are significantly lower) with a 20 dB crest factor at 3m with 86 dBw efficient speakers).
 
You must log in or register to reply here.


advertisement


Back
Top