[/quote]The article was written 12 years ago. Hearing aid DSP technology has progressed very significantly since then, but this quote is very misleading: "Also, hearing aids are by no means HiFi. The pair of $6000 hearing aids you're thinking of buying will make your Hi-Fi stereo sound worse than a $25 table radio." That's a very polarized, black vs white statement. The reality is, there are many degrees and types of hearing loss. When the loss reduces your quality of life, you go for correction, which if done properly, improves your quality of life. Today's DSP hearing correction is quite deep and detailed, with many features that even audiologists don't understand. If you google a bit you'll find an entire community of hearing aid patients that have "hacked" their own devices to make intelligent adjustments on their own. It's important to realize that if the corrective device doesn't improve life, then you go back to the audiologist and make adjustments. And while every hearing aid can be instantly removed if you don't want to use it, maximum benefit is only achieved by full adaptation to the device by wearing it full time.
Hearing loss is not a black/white condition any more than vision loss, it's fully variant from slight to severe, and with many different types of losses and response curves. There's no way to accurately state the quality of the correction as equal to a $25 table radio (if there is even such a thing), and that just indicates both primitive technology, lack of proper adjustment, and adaptation. If they don't benefit you, pull them out and go back to the audiologist. Thats what you're paying $K for.
I'm talking about integrated systems, like tabletop "hi-fi" all in one units that sell for around $100 in big box stores like Walmart. I've reverse engineered several dumpster units (it's always the CD player that goes out and the amplifiers work) and they all used hard wired equalizers to pump up the sound of the speakers. The speakers are small and always bass deficient. A custom equalizer curve will vastly improve the performance, with the obvious tradeoff being loss of headroom (max spl).
Since these equalizers cut in at relatively high frequencies (250-300 Hz in my batch) they will make the bass of a decent hi fi speaker sound boomy and exaggerated. Decent speakers usually only need a little help below 100 Hz or 60 Hz, if they even need that. This is typical of air suspension systems. It is by no means universal.
Simple shelving equalizer: + 3 dB @ 60 Hz, + 6 dB @ 30 Hz, max boost about 10 dB, switched by a relay.
It only boosts what needs to be boosted. It does not add any boom to male voices; you can switch it in and out while a male voice is talking and there is no audible difference. But with program material with bass it boosts the lower frequencies just enough to compensate for "typical" air suspension speakers. You can change the turnover frequencies, max boost, etc. by changing a few parts.
Shelving equalizer. See above.
I still recommend you get a cheap DSP. You can change it on the fly and it's a lot less daunting than designing analog filter circuits. In fact you can use one to get you in the ballpark before you commit to building an analog circuit.
It's great that you have recycled discarded units, the sheer volume of throw away electronics is disturbing, and even more disturbing is where they end up, polluting the county they get dumped in. Mountains of e-waste, and what's more there be gold in them mountains.
About these hard wired equalizers, the TEA 2025 circuit I have seems to include a filter of some sort, is this the kind you mean?
There may be some instruments and musical sounds that move across the boundary of the filter in a song, what happens then? Is there a smooth roll-off?
Also, what about software equalizers? The Android ones seem to cut everything, and I already am stuck with low power so it is not really very effective as a solution.
I get some good parts from it. I've even got a few decent chassis for free.
There's no sound shaping filter in that circuit.
It's pretty seamless in practice. Remember it complements the speaker's response. It's unobtrusive but makes a big difference when needed.
It's sure a lot smoother than turning the bass control up, which invariably boosts too wide of a range of frequencies.
I haven't messed with them yet. I'm doing analog circuits. But a lot of people here have done stuff with them. Maybe ask around.
Eddie:
Recycling: just wondering if you think there is any value in a government program to subsidize recycling and repairing of discarded audio equipment? I know your government believes in free market economics but just thinking about the idea. Even where I live, they say 'that cannot be repaired' or 'not worth repairing', or genuine parts are difficult to obtain. But I digress. My best listening experience so far has been on discarded equipment.
What about loudness switches? I like those a lot.
Recycling: just wondering if you think there is any value in a government program to subsidize recycling and repairing of discarded audio equipment? I know your government believes in free market economics but just thinking about the idea. Even where I live, they say 'that cannot be repaired' or 'not worth repairing', or genuine parts are difficult to obtain. But I digress. My best listening experience so far has been on discarded equipment.
What about loudness switches? I like those a lot.
"Government programs" are usually horribly inefficient, administered by morons, and subject to special interest influence and outright corruption. Never hold your breath while government applies its "solutions" to a problem.
Recycling and reuse is very important in my opinion. Today's electronics becomes obsolete in typically a few years. Recycling costs money but if there's money to be made, then it will happen. Precious metals are typically recovered from laptops and PCs which results in a modest profit of a couple dollars. The rest is distributed for metal and plastic recycling, and finally some real nasty stuff goes to the landfill.
Best is reuse but except for people like me that's not going to happen in the US of A. People must keep buying their cheap crap to keep the economy chugging along. Companies that make things that last more than say ten years won't be in business long.
But some old PCs are shipped to Africa, where people make a living assembling refurbished PCs from mountains of electronic junk. There are shops with the shelves stuffed with refurbished PCs, laptops, screens, printers, etc. There it makes economic sense to do this labor intensive stuff. Here you have to make so much money right up front just to pay all your government fees, licenses, bribes, taxes, fines, insurance, etc. The government gets the biggest cut and the businessman gets only a tiny sliver of revenue, unless he operates a "scab" business (and there's a whole lot of those). So there's no incentive to open a business unless you're going to generate considerable revenue.
"Loudness" controls evolved from the old Fletcher-Munson compensation circuits from the 1950s. Most of them sound absolutely horrible to me, and consumers of today have no clue what it's really for. They boost the bass way too much and just introduce lots of distortion. They are nothing like the compensation circuits of old, which at least tried to address a real problem; even if they didn't always work that well.
If you follow this forum,then you know that many of us have revisited this issue. I've been working on it for months myself, making small changes to improve performance. OP275 to drive low impedance network?
I have experimented with EQ for my hearing losses, the usual HF hearing loss and a noise induced hearing loss causing a dip around 6kHz. I conclude that jaddie is correct, I have hearing aids, they help a little with my tinnitus, but I tend not to wear them much. They are no use at all with music due to the processing delay. I have adjusted to my hearing loss and when I try anything other than a little HF boost the sound is too harsh.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.