A Little About JBL

[brombo]

The following link may be of interest -

https://www.keele-omholt-technologies.c ... 6-v8.1.pdf

[Cogito]

@Cogito: You might want to "tuck in" these statements, as your "knowledge gap" is starting to show -- rather than "obstructions" that cause reflections, these are shaped grates that are Patent-pending Tapered Horizontal Waveguides (notice the wide gaps that leave the woofer/mid-ranges mostly exposed), and which perform the function of steering and directing the sound-pressure waveforms.

Those are nothing new. Lot of speakers already use them. In this speaker, it applies only to the tweeters, not to the woofers behind them.

Show me one source which claims obstructing the driver is a good thing.

[brombo]

Ever see the guts of a horn's compression driver. It also depends on the wavelength at the crossover frequency. If the dimensions are small compared to a wavelength you are not in the wave propagation regime and the effects are quite different. Notice how the woofers are arranged in the Genelec 8361A speakers -

https://www.audiosciencereview.com/foru ... tor.28039/

[Cogito]

Ever see the guts of a horn's compression driver. It also depends on the wavelength at the crossover frequency. If the dimensions are small compared to a wavelength you are not in the wave propagation regime and the effects are quite different. Notice how the woofers are arranged in the Genelec 8361A speakers -

https://www.audiosciencereview.com/foru ... tor.28039/

Genelex's are not horn speakers. They are co-axials with wave guide, and bass reflex for woofers. They are not blocking the wave path like your JBLs are doing.

[tomp]

At one of the Speaker Design Competitions where I was a judge, the three judges including me gave the highest marks to one of the entries in what at that point was the under $200 category. It was shy on bass, but the rest of the performance was outstanding. Driver quality has increases dramatically in recent years and there are now drivers out there that are real values. It all about knowing what you are doing.

Tom,
Again, we have to go back to the design criteria. You DIY person should have given audio quality highest priority in the design. Can we say the same about these JBL speakers?

And in a DIY speaker, cost is calculated only for raw materials. Labor cost is not included. In real world, the $200 raw material speakers would be sold for more than $1k in retail stores, no?

Probably. The point is you don't have to have megabuck components to get good sound. Great components for anything in audio not used properly will not give good results. Good components when used properly can give very good sound.

[SoundMods]

Please just look at the review. The speakers were designed by Don Keele who wrote most of the book on speaker measurements ( https://en.wikipedia.org/wiki/D._B._Keele_Jr. )

https://www.audiosciencereview.com/foru ... cer.21469/

Keele might have designed these speakers, but without information on the design criteria he was working with, one cannot make any judgements. Afterall, contemporary JBL is not a "high-end" company anymore. They are competing in low-end mass-production speaker brands like Yamaha and Sony.

Very sad but true.

[brombo]

As near as I can determine the midrange drivers crossover to the tweeter no higher than 800Hz where the wavelength is 0.43m. I would say that the spacing of the midrange radiator and the tweeter support are less than 1/8 wavelength at the crossover frequency. I do not see that as affecting the loading of the midrange. For diffraction effects look to the measurements. The shape of the tweeter support may even have the objective of reducing horizontal beaming of the midranges at the higher frequencies.

[Cogito]

As near as I can determine the midrange drivers crossover to the tweeter no higher than 800Hz where the wavelength is 0.43m. I would say that the spacing of the midrange radiator and the tweeter support are less than 1/8 wavelength at the crossover frequency. I do not see that as affecting the loading of the midrange. For diffraction effects look to the measurements. The shape of the tweeter support may even have the objective of reducing horizontal beaming of the midranges at the higher frequencies.

Crossover points have nothing to do with the concept of eliminating reflections. Look at the woofer in BMW speaker. It has a phase plug in the center. Its purpose is to stop the sound waves generated by the cone from reaching the opposite side of the code. IOW, protect the code from reflections. OTOH your JBL, is designed to create reflections on to the cones.

[cport]

@Cogitare magis: Crossover points have nothing to do with the concept of eliminating reflections.

Non Logica. The phase plug (as you state) is designed to prevent "high-frequencies" from self cancelling [the size and positioning of the phase plug only impacts higher frequencies, reflecting them outward, and is transparent to lower frequencies] -- so your statement makes zero sense -- if the driver is not fed frequencies (via the crossover) that the phase plug could impact, then the cone will not move, and there will be no reflections that it will correct for -- so crossover points have everything to do with "maintaining linearity" of a driver.

[SoundMods]

@Cogitare magis: Crossover points have nothing to do with the concept of eliminating reflections.

Non Logica. The phase plug (as you state) is designed to prevent "high-frequencies" from self cancelling [the size and positioning of the phase plug only impacts higher frequencies, reflecting them outward, and is transparent to lower frequencies] -- so your statement makes zero sense -- if the driver is not fed frequencies (via the crossover) that the phase plug could impact, then the cone will not move, and there will be no reflections that it will correct for -- so crossover points have everything to do with "maintaining linearity" of a driver.

Would you believe that the reason for a phase plug (it is a nice marketing name) is to simply get rid of the dust cap and its attendant cavity resonance that mucks up the sound.