What are some really good values in speakers?

S

shkumar4963

Audioholic
Yesterday I listened to my LS50 at 0 degree till 90 degrees. I could hear a timbre difference at about 75 degrees and above. With two way design (crossed over to sub at 80), shouldn't I be able to hear a timbre difference at lower angles for all the reasons of directivity discussed above? Or is this not a good experiment?

@yepiamonfire and others, Thanks.

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D

DubPlate

Audioholic Intern
Not exactly, in a three way design, a large woofer for the bass and low midrange, and a smaller woofer for the midrange/lower treble, would do so, at least for the midrange. The problem one runs into is that something like a 4” midrange driver will still begin to beam at about 2500hz. A 1” dome tweeter will still beam at 8khz. If you were to design a 4 way speaker with a 12” bass driver, an 5” upperbass/lower mid driver, a 2” dome midrange, and a 1/2” tweeter for the harmonics, using xover points of 120hz, 1700hz, and 4khz, directivity would be matched fairly well. A 1/2” tweeter wouldn’t start becoming directional until about 17khz. The issue of varying directivity is still a problem though. Each driver will be very wide at the low end of their operating range, and get slightly more narrow as frequency increases.

This is why I personally think waveguides/horns are a good solution instead. You can achieve matched directivity easily with a 2 way or three way design, since the horn allows a much lower xover than if the tweeter were direct radiating, and the waveguide will control the directivity across most of the bandwidth. A 5.25” woofer can be run up to about 1800hz before beaming becomes an issue. A 1” titanium driver can be crossed over as low as 1000hz if the horn is large enough. A three way system with midrange and high frequency horns gives even more directivity control of the lower midrange, down to about 500hz.

The problems associated with timbre and imaging from uneven dispersion and room reflections of that uneven response occur mostly above 1khz according to Tooles findings. Considering this, a horn that controls directivity above 1khz, should solve these problems. It doesn’t matter if the dispersion is narrow or wide, as long as the directivity is uniform up to at least 10khz. Wider dispersion allows more reflections, narrower allows less, Geddes suggests narrow dispersion speakers (60 degrees comical) to greatly reduce room reflections. Toole suggests wider dispersion speakers. I personally think a middle ground is best. +-45 degrees seems just about perfect for most home audio setups. All seats fall into the pattern, and most room reflections fall on the outside edge of it, reducing their level compared to direct sound, but ensuring they’re of the same timbre as the direct.


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Thanks for you detailed reply. I find the subject matter very interesting, and I hope be that more knowledgeable with regard to future purchases.

The RP-150m, which I believe you mentioned earlier, has 5.25 woofer, and a one inch tweeter with horn/waveguide. The RP-150m is crossed over at 1500hz.

However the RP-280f, having the the same 1 inch tweeter, but bigger woofer, two 8 inch, is crossed higher, at 1750hz.

It would appear the reverse should be the case, i.e., the the RP-280f with the bigger woofer should be crossed over at a Lower point than the RP-150m. That is why I enquired about whether having 2 woofers, as does the RP-280f, helps mitigate beaming and permit a higher crossover.

It would also appear that the RP-280f is crossed over above the point at which the woofers beam, two 8 inch at 1750hz. But independent testing show a pretty flat of axis response.

Does the folks at klipsch have some magic workaround?
 
killdozzer

killdozzer

Audioholic Samurai
B

Beave

Audioholic Chief
Installing yes, but much more than that. Acoustic analysis of listening space, consulting on acoustic treatments, their need (or not), their placement, speaker placement, eq, etc.
 
Steve81

Steve81

Audioholics Five-0
This is an excellent article (among the rest of their series on directivity/off axis response) on driver diameter and matching directivity. http://www.acousticfrontiers.com/speaker-off-axis-ka-and-driver-diameter/
Keep in mind, that link is talking about the actual cone diameter, not the nominal size of the driver. That leads to a pretty big difference in the XO numbers being discussed per their rule of thumb (not that exceeding it by a small amount is immediately going to lead to their "ugly graph" either).

A few examples from the Scanspeak Revelator line:

4.5" Unit : ~2.9" cone diameter
5.5" Unit: ~3.9" cone diameter
7" Unit: ~4.8" cone diameter

Those figures suggest the 4.5" unit would ideally be crossed at or below 3kHz, the 5.5" unit at 2.2kHz, and the 7" unit at 1.8kHz.

So how does that align with reality? Well, Dennis uses a 5.5" Revelator in his Philharmonitor crossed up at 3kHz, and there's still no meaningful sign of beaming even on the 60 degree off axis graph:
http://www.philharmonicaudio.com/New Philharmonitor.html
 
killdozzer

killdozzer

Audioholic Samurai
Coaxial drivers in theory have high levels of IM distortion, however, with the amount of engineering and research kef has done, they may have found a solution to it. Never heard them and never seen measurements so I can’t comment.


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What I'm about to write is just some unfounded common sense, so have some patience, please.

I'm always amazed when I see forum people taking it as definitive that; coaxial drives are inherently flawed, ClassD amps can't filter what they need to filter sufficiently enough, ribbons are superior etc. (I'm not saying this is you) and then you have all these companies, even the ones that are highly trusted, that hold on in there with all these designs. Not only KEF, but Tannoy makes point source for ages now, Fostex has some models and so on. NAD sticks with ClassD, even Cyrus, only recently everettT gave me a light scorn about some ATI amps that are ClassD.

So, how come all these companies stick with what we all know is bad. I know many companies stick with what sells even when it's not really better. But CalssD is not a selling point. As far as point source goes, If you know what it is, you know enough to have probably heard of its "inherent flaws".

Are these still considered inferior for home audio or are we past that? If point source is inherently inferior, how come guys at Tannoy haven't heard about that?

You see what I'm saying?
 

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