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Ultima pointed out it's been 3 years...

Posted 24th August 2015 at 04:34 PM by chris661
Updated 24th August 2015 at 04:39 PM by chris661

So, three years is a long time to wait, and a lot of things have happened since the last post, some of it quite personal. I'll put it all up in sections, so if there's a bit you're not too interested in, its easy to skip.


Sound Stuff, because hey, this is an audio forum.
I arrived at Uni with my Fostex & Tang Band FAST speakers: a bi-amped setup of a FE126eN and a W6-1139 a side, 500Hz crossover. They were used for parties occasionally in the shared area of the flat in first year, and then I bought a subwoofer - JBL GTO1214 in one of those pre-fabricated car sub boxes, since that was all I could get hold of at the time. Power was a Samson Servo-550 for that.
I used that lot for a while until I realised that the Fostex drivers have a lot of distortion when you increase the volume, which throws the sound well out of balance.
Found a pair of Behringer B2031P monitors and have been using those since. Much better for what I want, though they still...
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Old

DIY Audio Analyser using CS4398 / CS5381

Posted 21st August 2015 at 05:16 AM by googlyone

Over the years I have played with measuring - well - just about everything in audio.

distortion measurement has been one of these preoccupations, not the least because it is hard to do, and using commercial gear, expensive.

I have built analogue hear to do this, used mixes of analogue and digital and of late played with using modified commercial sound cards. My efforts on the Sound Blaster x-Fi were interesting but ultimately not rewarding enough for me to leave the mods in there.

I have also been playing with using the A/D and D/A converters from my DSP crossover for this purpose. These are modular and use a common I/O plug with power MLCK, SCLK, LRCLK and Data (alone with I2S for the CS4398 and sometimes a digital volume control).

--- notwithstanding the fact that in previous tests I have shown the digital volume control is the MAJOR source of distortion - I will plug ahead with this, and likely leave that out of the test...
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Old

an economic diy sub to compliment EV ZLX12P

Posted 17th August 2015 at 07:55 PM by colossusfan
Updated 25th August 2015 at 04:17 PM by colossusfan (passive part of sub complete)

My first attempt at a blog so i hope i dont bore the pants off you all!!
I bought a 2 way so called 1Kw integrated speaker some time ago about which I have written various posts in the forums, management overview better value for money than DIY but vastly inflated specification as all similar units, actual measured output around 110dB max and LF rolloff starts at 80hZ!!
Soo it needs a sub!!
well if like me you like your low end forget the EV sub (ELX118p) and most of its compatriots for two reasons, one is rolloff starts at 40hZ or above, and 2nd is cost!!

Looks like i just use edit to add to the blog!

So to continue I used the UNIBOX spreadsheet (free) to model various drivers and box combinations, true to my namesake I started off with large Fane drivers but was scared of the price!! However I also discovered various nasties with ported or tuned enclosures most notably you tradeoff an extension in the 40-60hZ range for a much sharper cutoff...
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Old

Fountek (Rhyme Acoustic) active speaker A-100

Posted 24th July 2015 at 08:18 AM by panson_hk
Updated 28th July 2015 at 01:37 AM by panson_hk

I purchased a pair active speaker. This is manufactured by Fountek under the brand Rhyme Acoustic. The model number is A-100. It uses a 4" full-range driver with vented box. The electronic is contained in the right channel enclosure. The amplifier is LM4766 chipamp. The overall build quality is good. I just paid RMB 399.00 during its sales period. What a good deal!

Chinese product link is https://item.taobao.com/item.htm?spm..._u=od0rlto94d1 The frequency response shown in this product page does not match with that given the user's instruction of my pair. The curve shown in user's instruction does pretty much match with my initial listening impression: lack of treble.

I measured the speaker with my CLIO Pocket. Measurement shows left and right enclosure response are matched very well.

The last figure shows the left box (passive) driven by another amplifier. We can then see what filtering or EQ is...
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Old

Another incredibly cheap Taobao toy

Posted 19th July 2015 at 10:00 AM by abraxalito
Updated 10th August 2015 at 10:44 AM by abraxalito (Listening report added; chip pinout added)

When browsing Taobao I can't resist the temptation to try the very cheap stuff. This little TFcard player really takes the biscuit for the lowest price of a digital audio source - 9.9rmb. So I ordered up three, I might just order more soon.

First powering up I tried some FLAC files, these don't work but wav and mp3 work fine and it even finds files below the root directory. Power supply is nominally 12V but its using an EF fed by a zener diode, not an IC reg so almost anything from 6V will probably work. I haven't managed to find the technical blurb for the chip so far so a little reverse engineering was needed. It incorporates a 3.3V regulator to power the IR receiver and the TFcard - I have fitted an additional regulator for the first mod because I wondered if the low-level noise I was hearing was due to interference from the flash card's power draw. Turns out no as when playing .wav files this noise disappears.

Incidentally the 9.9rmb cost includes the remote...
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Old

Baffle mechained by a desktop CNC

Posted 14th July 2015 at 02:37 AM by panson_hk

I use DeskProto to generate toolpath for the CNC controlled by Mach3.
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Old

Building a cube enclosure

Posted 14th July 2015 at 01:44 AM by panson_hk

I am enjoying all the fun of building speaker enclosure. An inexpensive 2" full-range is employed. The cube is made by MDF. I have measured TS parameters of the driver and its response with a big baffle. I use Basta! and LEAP-5 to simulate the box's response and impedance. Once the box is built, I can compare actual and simulated data.

Two cubes will be built. One is sealed and the other is with passive radiator.
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Old

Measuring compliance of passive radiator

Posted 14th July 2015 at 01:32 AM by panson_hk

I am using a handheld force meter and caliper to measure compliance of passive radiators. The force meter is clamped to the caliper. Caliper is used to show the panel displacement whereas force meter displays the corresponding force. I can then obtain compliance C mm/N. I am planning to use an Arduino controlled Z-axis for automatic measurement. The force meter has a USB interface for data acquisition.

I should be able to measure BL vs displacement of a driver by adding a programmable DC supply.
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Old

Audio Op Amps

Posted 26th June 2015 at 02:59 AM by rjm
Updated 13th July 2015 at 02:23 AM by rjm

I'm often asked "which op amp sounds better".

The reply is usually a scowl and muttered "does it look like I care!?" Which is something of a lie... I do care about getting op amps to sound good. It's the phrasing of the question I dislike.

Op amps do not come in "good, better, best" flavors. All it is - and this is pretty obvious I would have thought but apparently not - all this is about is matching an op amp to the job it's going to do; the circuit it's going to be sitting in.

The op amp you'd choose to use as a DAC IV converter is different from the one you'd choose to back a 100k volume potentiometer in a preamp is different from the one you'd choose for an MC phono preamp input stage...

Why do you think there are like a gazillion different op amps to choose from in the first place? It's because there are about a gazillion combinations of op amp characteristics and properties ... not because...
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Old

From Tube CAD Journal by JRB

Posted 25th June 2015 at 08:05 PM by alexcp (My DIY projects)

For every hobbyist-built amplifier in existence there are probably one thousand amplifiers which are planned on being built and maybe one hundred amplifiers that have all their parts collected in a box waiting to be built and ten amplifiers that are partially built and collecting dust in a closet.

(see full post here)
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