Why FR may sound better with dedicated HF unit - diyAudio
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Old 24th May 2006, 12:53 PM   #1
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Default Why FR may sound better with dedicated HF unit

To my ears the Jordan JX92s sounds better with a dedicated tweeter in parallel - there is that extra sparkle that is missing from the FR alone.

I have a theory about this - maybe the frequency curves of such drivers are measured as simply the total volume vs frequency rather than volume of the specific fundamental frequency vs frequency, ie the unit is producing a coloured sound at higher frequencies, with a greater emphasis on low frequency sub-harmonics. The oposite may be true for the dedicated tweeters - they esentially filter out all the low frequency harmonics which are always present in sound (harmonics that are such an integral part of the main harmonic, that they cannot be redirected effectively to another driver by a crossover).

The two used in combination would therefore tend to complement each other and give a more rounded, natural sound with less filtering, particularly when listened to off-axis....?
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Old 24th May 2006, 02:03 PM   #2
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OK there's some misunderstandings here.

Harmonics are multiples of a frequency. So 10 kHz does not have any lower components, only higher ones.

The frequency response of a full range unit is assessed by playing a pure sine tone and observing the resultant SPL. Therefore a flat response means same volume level at all frequencies.

The reason you like the sound of the fullrange drive unit with added tweeter is simply because you like the rise in high frequency response (sounds like extra detail) that adding the tweeter brings. It also extends the response of the system up higher with better dispersion characteristics, again which you may be susceptible to, particularly if you listen extensively off-axis.

'Not point source enough' is not possible for a fullrange drive unit. There is only one radiating area.
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Old 24th May 2006, 02:37 PM   #3
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Wouldn't it be better to measure frequency response by using white noise and measuring the output at varying frequencies as there could be some interaction between the frequencies when more than one is reproduced and most real sounds always have more than one harmonic?
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Old 24th May 2006, 03:59 PM   #4
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Yes that is done also and is called spectrum analysis.

Also distortion measurements swept across the band would usually show up any artefacts such as you mention.
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Old 24th May 2006, 04:08 PM   #5
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Thanks richie...
So is there any spectrum analysis information on the Jordan JX92s or similar drivers and how it compares with frequency response?
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Old 24th May 2006, 04:16 PM   #6
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Not only the on-axis response determines if a driver sounds bright or dark. Off-axis respnse is important also. HF dispersion is one subject where good tweeters excel.

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Old 24th May 2006, 04:28 PM   #7
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But too-wide a dispersion can ruin the stereo image if Jordan is to be believed - maybe this rule is actually less important for these frequencies as they are inherently extremely directional and they don't reverb around the average room and the more dispersion the better.
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Old 24th May 2006, 04:52 PM   #8
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I think Jordan has some graphs on his website, but not sure if they are full spectral ones.

Don't confuse the short wavelengths of HF sounds with directionality per se. These sounds are only so directional because of the limitations of the transducers reproducing them. It's difficult to detect the source of LF sounds with their long wavelengths simply because the length of the wavelength means that it happens over a longer physical size range - this is placement/localisation rather than directionality. Suttle difference.

Regarding the dispersion characteristics argument camps: wide as possible vs directional as possible, with top guys like Linkwitz and Jordan following the directional approach there needs to be some good arguers in the opposite camp.
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Old 25th May 2006, 09:26 AM   #9
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Jordans graph is labelled 'frequency response' so I assume it is not the full spectrum analysis. Perhaps someone here has done some measurements?

I think there is an argument for fuller dispersion of sound at the high end of the spectrum to counteract the beaming as these frequencies cause little or no room resonance, little room reflection and are far less penetrative than lower frequencies. The wavelength is so small that moving your head ever so slightly (rorational or laterally) can drastically change the volume of sound in low dispersion environments. This directionality does not matter so much at lower frequencies because of the very different way the sound behaves. Loudspeakers are trying to create a natural sound and the beaming at such high frequencies is rarely found in nature.
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Old 25th May 2006, 10:56 AM   #10
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Maybe Ted himself has some measurements, just not published them to keep the site clean and easy to follow.

I'm not convinced about little reflection of higher frequencies as a generalisation, it comes down to room layout and furnishings.

That's true and a good point about having a very tight sweet spot. I'm currently deciding whether to spend loads on a full set of JX92S or mess about building some cabinets for the bunch of drivers I already have (which would need crossovers etc). I had a pair of JX92S for a while and liked them a lot, but I feel I should play around more with what I have, plus the full JX92S set is expensive!
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