Took me 3 hours listening to three DVDs to fine tune a simple 2.1 amplifier (Kentiger with TDA7297) class AB. Incredible value these chipamps offer.
Really, only by listening I needed this time although I am an experienced listener. It took this time.
And later never touch again! If someone turns the knobs.... work starts again.
Really, only by listening I needed this time although I am an experienced listener. It took this time.
And later never touch again! If someone turns the knobs.... work starts again.
To the OP: I noticed appreciations for your presentations, but perhaps not enough for your constructions—I think the woodworking is handsome, and crossovers are visually well-made. I also am aware that musicians often want something slightly different from loudspeakers than some audiophiles do. I sometimes feel that what I like is not the same as the current high-end trends.
I have found this is an informative and multifaceted thread; most other references/threads only discuss isobaric sub-woofers----so thank you all!
I recently heard a speaker with lively/accurate/musical isobaric hi-fi woofers that got me thinking about the possibilities.
Most current sub-woofer drivers that I have heard, and some HiFi woofers with highly damped cones, don't do upper bass/lower mid-range with a realistic sense of “liveliness”(I seem to really prefer this liveliness). They are soft and muffled sounding. There must be those who do not agree with me here---or else respected companies would not release dull sounding hi-fi woofers???
Being able to use “lively” and articulate hi-fi woofers (or certain pro woofers) in smaller cabinets, while perhaps reducing the cabinet's internally reflected, and time delayed, sound from reaching our ears, seems like a win.
Naturally, crossing low to a mid-driver is a requisite, but I wonder if the rear woofer in an isobaric arrangement could be additionally low-passed to reduce time smearing, if the isobaric pair were used into the lower mid-range?
There must be some wavelength threshold above which the pressure does not couple between the cones, where it could be favorable to low-pass the rear woofer, but not necessarily the front woofer?
This general scenario (producing frequencies high enough (including distortions) to be effected by a small amount of acoustic damping material) must be why the Linn patent included the acoustic curtain between the drivers?
I have found this is an informative and multifaceted thread; most other references/threads only discuss isobaric sub-woofers----so thank you all!
I recently heard a speaker with lively/accurate/musical isobaric hi-fi woofers that got me thinking about the possibilities.
Most current sub-woofer drivers that I have heard, and some HiFi woofers with highly damped cones, don't do upper bass/lower mid-range with a realistic sense of “liveliness”(I seem to really prefer this liveliness). They are soft and muffled sounding. There must be those who do not agree with me here---or else respected companies would not release dull sounding hi-fi woofers???
Being able to use “lively” and articulate hi-fi woofers (or certain pro woofers) in smaller cabinets, while perhaps reducing the cabinet's internally reflected, and time delayed, sound from reaching our ears, seems like a win.
Naturally, crossing low to a mid-driver is a requisite, but I wonder if the rear woofer in an isobaric arrangement could be additionally low-passed to reduce time smearing, if the isobaric pair were used into the lower mid-range?
There must be some wavelength threshold above which the pressure does not couple between the cones, where it could be favorable to low-pass the rear woofer, but not necessarily the front woofer?
This general scenario (producing frequencies high enough (including distortions) to be effected by a small amount of acoustic damping material) must be why the Linn patent included the acoustic curtain between the drivers?
Thanks @howardg ! 🙂
Yes. I am in this case too... 😉
Yes, on my 475L ISOBARIC, that transistion is set at 300Hz between the Bass and the Low-Mid.
I'm not sure that using the Isobaric principle for a Low-Mid frequency range offers a great interest, with or without additional low-pass... That said I never tested it, OK ? So what advantages have you in mind ? 🤔
Yes. From the litterature I have on the Isobaric subject, it seems that the isobaric coupling gently vanishes for frequencies above 300-500Hz, depending also on the speakers performance.
Well, maybe I miss something in your description, but I do not see why you would use a different LPF (or no LPF) between the front and the rear speakers. I mean : what advantages you would expect to draw from such a choice ? 🤔
T
Oh, I was thinking that if I wanted to have a passive, low order, low-pass filter, that both woofers would still be getting a significant amount of higher frequencies. I was concerned that the rear driver output might re-radiate through the front cone, out of phase with the front voice coil output at the same frequencies.
I was thinking that the front woofer might want to play higher to meet a smaller mid-range driver in a 3way. Or might it even be possible to make an isobaric-woofer 2way???
One bit of info that would go against my whole line of thinking here is something that the designer of a successful isobaric 3way told me: that he needed to be very careful in matching the woofers' parameters in an isobaric pair, but he did not elaborate on what parameters were especially important. Filters would definitely change the electrical characteristics that are seen by the amplifier, so if the electrical parameters need to be matched, then having different filters for each woofer might cause problems. This would not keep me from trying though!
Like many patents in the Audio world, think of Ripole or CANTON DC (putting a large capacitor in series with a woofer of a vented cabinet), they are just some well known principle, decorated with some complicated stuff. Aimed to make it seem like something unique. Otherwise no patent office would except this as a patent worthy invention. Often such patents are only filed to keep others from producing a similar product and give the marketing departement something to chew on.
There also is a lot of scamming going on, where people patent old stuff and stop a large company selling their already produced products. It is less cost for such a company to pay the scammers instead of waiting, sometimes years, for a judge to throw the patent out, while the sale is halted.
With LINN isobaric, the felt curtain is nothing important to the result, just some kinky decoration. Anyone can measure this, something the patent office doesn't do.
There also is a lot of scamming going on, where people patent old stuff and stop a large company selling their already produced products. It is less cost for such a company to pay the scammers instead of waiting, sometimes years, for a judge to throw the patent out, while the sale is halted.
With LINN isobaric, the felt curtain is nothing important to the result, just some kinky decoration. Anyone can measure this, something the patent office doesn't do.
When I omni-clamshell-iso'ed Peavey Scorpions ("stealth bomber") the treble extended so high and strong I wandered about bleed-through interference and whether to add some in-between fill. Next time I work on them (to add a bowl-hat-horn) I'll pay attention and experiment a bit.
Good to know.
I have wondered if there has been experimentation with anything like a flared port end attaching to each driver, and a narrower part in-between. "Intuitively" it seems the velocity would increase in the middle, and also the overall volume of the coupling space would be smaller. Whether changes in velocity (and impedance?) would be a net plus is beyond my knowledge.
I see @howardg. Yes, your thoughts are indeed sensed.
I must confess that I haven't been so far about the amount of remaining higher frequencies, simply considering that out-of -phase would cancel enough those frequencies, and help a low-order crossover, assuming that the FC is low, located at the upper frequency limit of the Isobaric principle (which is roughly the same as the piston working area frequency limit). At least, that's what I can observe and listen with my 475L ISOBARIC where the woofers are paralleled and cut at 300Hz.
For a 2-way Isobaric enclosure, it could be different, though, as there's a need to reach higher FC. I know that there's a brand of Isobaric 2-ways speakers : https://monacoustic.us/product/the-supermon-isobaric/?v=11aedd0e4327 , so it's feasible with success. Maybe then the front speaker is cut at the required FC to match the tweeter, and the read speaker is cut at the Isobaric or Piston frequency limit, to avoid any loose cancellation on upper frequencies ? Why not...
On the 475L I admit that did not matched particularly the woofer pairs... My choice criteria was that they were suitable for a Sealed enclosure operation, since it is an Isobaric Sealed one. I guess that for a Bass-Reflex enclosure, you would obviously choose speakers suitable for BR operation.
A point that I considered when designing the chamber, is that the air flow always met at least the back SD of one speaker, to avoid any additional air flow surface reduction between the two speakers.
T
I must confess that I haven't been so far about the amount of remaining higher frequencies, simply considering that out-of -phase would cancel enough those frequencies, and help a low-order crossover, assuming that the FC is low, located at the upper frequency limit of the Isobaric principle (which is roughly the same as the piston working area frequency limit). At least, that's what I can observe and listen with my 475L ISOBARIC where the woofers are paralleled and cut at 300Hz.
For a 2-way Isobaric enclosure, it could be different, though, as there's a need to reach higher FC. I know that there's a brand of Isobaric 2-ways speakers : https://monacoustic.us/product/the-supermon-isobaric/?v=11aedd0e4327 , so it's feasible with success. Maybe then the front speaker is cut at the required FC to match the tweeter, and the read speaker is cut at the Isobaric or Piston frequency limit, to avoid any loose cancellation on upper frequencies ? Why not...
On the 475L I admit that did not matched particularly the woofer pairs... My choice criteria was that they were suitable for a Sealed enclosure operation, since it is an Isobaric Sealed one. I guess that for a Bass-Reflex enclosure, you would obviously choose speakers suitable for BR operation.
A point that I considered when designing the chamber, is that the air flow always met at least the back SD of one speaker, to avoid any additional air flow surface reduction between the two speakers.
T