The Linkwitz Transform link is from the MiniDSP site, actually a community contribution. Checkout the spreadsheet first.
(the AD site hosts the excellent book on DSP).
Indeed. Worth spending time on these forums here at diyaudio.com for selecting the proper kits
As I remember, Kgrlee -a respected speaker expert- was one of the first here to advocate the advantages of FIR filters in speaker and room correction sw.
George
George,
You gave me plenty of homework to do, reading all that and understanding it is going to keep me busy for awhile.
Demain,
The TPA3116D2-Q1 seems to be one of the new power amps that can be run in bridged configuration. I'll take a look at the TAS5756M
You gave me plenty of homework to do, reading all that and understanding it is going to keep me busy for awhile.
Demain,
The TPA3116D2-Q1 seems to be one of the new power amps that can be run in bridged configuration. I'll take a look at the TAS5756M
I want to correct myself before someone else notices. The Linkwitz transform is really only for a sealed enclosure but my design is for a reflex design. So it isn't really Linkwitz design but a similar idea using EQ to bring up the bass without needing the massive power that this takes in a sealed enclosure. Kgrlee was against the idea of going with the closed air suspension idea for this simple reason but said we could do this with an IIR filter.
In a sealed box you need voltage, not power. It's more complex.
Sent from my SGH-M919 using Tapatalk
Sent from my SGH-M919 using Tapatalk
Demian,
A lot more voltage at that down low to get the excursion up in a sealed box. Kgrlee nixed that idea rather quickly to seal the box. I even proposed adding mass and he said no.
A lot more voltage at that down low to get the excursion up in a sealed box. Kgrlee nixed that idea rather quickly to seal the box. I even proposed adding mass and he said no.
For what its worth I have built woofers and subwoofers for a long time and unless the box is too small (and that would be pretty small) it has not been a problem. I have never been too excited by ports or passive radiators. However design constraints are what we all work within.
What you find in amps are single chip solutions like the TI I referenced that typically can drive 4 Ohms and run from up to 28V. These usually have I2S in and a full on board DSP. Usually you can configure a crossover and eq drivers pretty successfully. I think the chip has 4 20W amps or 2 80W amps but I have not looked at the datasheet in months. That product is out for bid at this point.
There are higher power solutions (usually for subwoofers) that use external output devices. You can get those with analog or digital in. Unless you need a lot of power they are not worth the effort.
Trying to pick from the Semi vendors parts yourself can be really hard. If you think the amps are bad check out the TI MSP430 microprocessor variations. There are hundreds (813 per the web site).
Here is the reality check- To make a self powered speaker today with "modern interfaces" you usually need the following skill sets-
1) hardware engineer to connect all the blocks, make sure they all operate within ratings, make sure the power supply is adequate, that you will meet the safety requirements and FCC/CE regulations etc.
2) a software engineer to program the microprocessor you need to run the thing. Make sure you can do field firmware upgrades. Its really painful to trash thousands of products because the firmware has a bug.
3) PC layout to get all this on PCB's that can be made reliably and meet the FCC etc. requirements
4) Mechanical engineer to fit all the pieces together and make sure it won't break and can be assembled (both not common qualities). Extra points for being serviceable.
5) RF/Bluetooth/WiFi wizard to get that module working if there are any issues. Usually they are software but antenna tuning can be a bitch.
I think this is why the audiophile world doesn't get close to this type of product and its mostly done in Asia where the shops and skills are more available.
What you find in amps are single chip solutions like the TI I referenced that typically can drive 4 Ohms and run from up to 28V. These usually have I2S in and a full on board DSP. Usually you can configure a crossover and eq drivers pretty successfully. I think the chip has 4 20W amps or 2 80W amps but I have not looked at the datasheet in months. That product is out for bid at this point.
There are higher power solutions (usually for subwoofers) that use external output devices. You can get those with analog or digital in. Unless you need a lot of power they are not worth the effort.
Trying to pick from the Semi vendors parts yourself can be really hard. If you think the amps are bad check out the TI MSP430 microprocessor variations. There are hundreds (813 per the web site).
Here is the reality check- To make a self powered speaker today with "modern interfaces" you usually need the following skill sets-
1) hardware engineer to connect all the blocks, make sure they all operate within ratings, make sure the power supply is adequate, that you will meet the safety requirements and FCC/CE regulations etc.
2) a software engineer to program the microprocessor you need to run the thing. Make sure you can do field firmware upgrades. Its really painful to trash thousands of products because the firmware has a bug.
3) PC layout to get all this on PCB's that can be made reliably and meet the FCC etc. requirements
4) Mechanical engineer to fit all the pieces together and make sure it won't break and can be assembled (both not common qualities). Extra points for being serviceable.
5) RF/Bluetooth/WiFi wizard to get that module working if there are any issues. Usually they are software but antenna tuning can be a bitch.
I think this is why the audiophile world doesn't get close to this type of product and its mostly done in Asia where the shops and skills are more available.
Nice check list Demian. I'm sure this would be much less expensive to create in China, I am already working there on other aspects of the manufacturing. A very interesting situation always.
Well, in that same China you have your pick (and thrn some) of modula power amps. Many are not worth the trouble, but there are some which area really very good on their own. And comparing prices, they are unbeatable. What you do have to be caredul about is that many are illegal rip-offs of other people's work, like Nelson Pass, Levinson, etc.
I remember seeing them before, nice, I want some.
If you want some PCB work, I can refer a good layout guy and put you in touch😉
dvv,
That is always the trepidation with doing business there, your product being sold out the back door to someone else. On the amplifier end of things I'm not looking for a custom amplifier design, more a competent design using a known class D chip. I'll really have to find someone who is comfortable designing a board that combines all these disparate IC's, the class D amp, and class AB small chip amp, the Analog Devices ADAU1701 chip and the X mos USB chip and the Libre wireless. I'm leaving things out but the general idea is to use proven designs and not reinvent any of this. I am not trying to produce a sota audiophile level design with many discrete parts, that would just raise the cost to high to make this all practical. I'm not looking for the cheapest solution either, I don't want something mediocre that would ruin the sound. As Scott would say the object is to optimize what already exists, not more and not less. Finding the person who can integrate all of this is where I am at this point. I have a friend who sells millions of connectors into the world market, perhaps he can help me out finding that person. That certainly isn't me.
That is always the trepidation with doing business there, your product being sold out the back door to someone else. On the amplifier end of things I'm not looking for a custom amplifier design, more a competent design using a known class D chip. I'll really have to find someone who is comfortable designing a board that combines all these disparate IC's, the class D amp, and class AB small chip amp, the Analog Devices ADAU1701 chip and the X mos USB chip and the Libre wireless. I'm leaving things out but the general idea is to use proven designs and not reinvent any of this. I am not trying to produce a sota audiophile level design with many discrete parts, that would just raise the cost to high to make this all practical. I'm not looking for the cheapest solution either, I don't want something mediocre that would ruin the sound. As Scott would say the object is to optimize what already exists, not more and not less. Finding the person who can integrate all of this is where I am at this point. I have a friend who sells millions of connectors into the world market, perhaps he can help me out finding that person. That certainly isn't me.
I think somebody already suggested this, but a safe bet would be one chip amps by National, for improved performance two in parallel delivering twice the currrent. As long as they are not driver too near their limits, they will provide good performance for the money.
Althought frankly, I'll stick to discrete designs of the vintage class AB type.
Althought frankly, I'll stick to discrete designs of the vintage class AB type.
Kindhornman ---- there are so many "plate" amps and the like from China sources, you should not have to make much of anything... assembly only. Evaluate... some with dsp. Look and shop around first.
Unless, you have a company to back the DSP hardware/software stuff, it is too long to learn it all yourself. PS -- you should have your drivers back in a few days... I shipped them before I left... I am at my condo in Bangkok at this time. Just flew in at 2am. I have come to see my little girl who I have supported her education since 1st grade and tomorrow she is 18. Going to see her in Kathmandu asap. Love that girl (woman now).
THx-RNMarsh
Unless, you have a company to back the DSP hardware/software stuff, it is too long to learn it all yourself. PS -- you should have your drivers back in a few days... I shipped them before I left... I am at my condo in Bangkok at this time. Just flew in at 2am. I have come to see my little girl who I have supported her education since 1st grade and tomorrow she is 18. Going to see her in Kathmandu asap. Love that girl (woman now).
THx-RNMarsh
dvv,
My preference would have been a discrete class ab amp but the reality is that heat generation and a massive power supply are real issues when you place an amp inside the speaker and it puts out real output power. A linear power supply is just big, no way around that and the idle power consumption is a real issue with the rules you have to follow today. Not sure you could even get an external smps that could drive a 100 watt class ab amp plus another small amp for the tweeter. Costs and practicality are the issue. If I was trying to make a $10,000 speaker then things could be different.
My preference would have been a discrete class ab amp but the reality is that heat generation and a massive power supply are real issues when you place an amp inside the speaker and it puts out real output power. A linear power supply is just big, no way around that and the idle power consumption is a real issue with the rules you have to follow today. Not sure you could even get an external smps that could drive a 100 watt class ab amp plus another small amp for the tweeter. Costs and practicality are the issue. If I was trying to make a $10,000 speaker then things could be different.
Richard enjoy yourself while your over there. Sounds like you've done a nice thing for someone, an education in that part of the world will change her life forever. It isn't easy to deal with Asian sources, Alibaba is not your friend, it is a real pain to separate the real from the illusions from those sources.
KIndhornman, I respectfully suggest you investigate, for your own sake and info, what has been done on the subject so far. Specifically, I refere to Philips/Grundig Motional Feedbac series in the late 70ies, I'm sure they faced just as many problems then as you do now. If memory serves, they also used 60W amp arrays, however they operated at 4 Ohms nominal impedance, so the power supplies had to be just as hefty. Also, if any info can be found on Klein & Hummel active speakers, I worked with those in the late 90ies and can vouch for their sound and build quality
I'll look up my own log, I seem to remember having some Philips NGB service schematics, who knows, they might come in handy.
For triamping, a countryman oif mine, Dr Borivoje Jagodić, put up some schematics on the web for the DIY crowd. I spoke with him on the phone a couple of times, but have not met him in person. He worked for an Italian audio company for 10+ years, so he's firmly in the field. Look his site up, it's free and very informative.
I'll look up my own log, I seem to remember having some Philips NGB service schematics, who knows, they might come in handy.
For triamping, a countryman oif mine, Dr Borivoje Jagodić, put up some schematics on the web for the DIY crowd. I spoke with him on the phone a couple of times, but have not met him in person. He worked for an Italian audio company for 10+ years, so he's firmly in the field. Look his site up, it's free and very informative.
Use AB/B amps with a small light weight SMPS... amp heat sink on the outside of cabinet. Ported enclosure assures some air flow over the input/driver inside cabinet. The DSP add-on is the hard part. Maybe just buy the guts of the miniDSP from DIYaudio. I am all for not reinventing things. Buy subsystems and assemble. Test. Adjust as needed.
-RM
I have supported the whole family and educating all of them. Started with a TV. Later a computer/Internet access. Then trip out of the country to a big modern city - Bangkok. Then to island resort....ocean. Over the years I have slowly brought them into the 21st century. Insisted they learn English -- now can read, write and speak in English. Lots of fun and reward. WAY better than donating money to a charity. The first time I took the family to a restaurant in Bangkok is where i learned the children had never used a fork and knife before. Nor saw an English toilet. Get personally involved in helping a family. Now they are up on the latest in everything and so much fun to mentor... so receptive and polite. The 'girls' look like 10's now too.... real woman bodies. Turned into butterflies. Leave for Kathmandu Friday.
PS... thanks for the call(s) John C. I was just too busy to get back to you before taking off.
Enjoy --- Richard
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