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Resistance that the speaker "sees"

May 18, 2015, 2:27 pm
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If you have a 4 ohm Mid/Woof, and a 4 ohm tweeter, (let's say with a simple first order xover), is the resulting load 4 ohm (nominal) or lower, say ~2 ohm?

Let's say both drivers are full-range (run without xover) is the answer the same? In other words, do the xover components separate the loads from each other somehow?

Sorry if it's dumb. Thanks.

I meant to title this "the amp sees".
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F9530N replaces BSP372?

May 18, 2015, 3:07 pm
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Theoretically speaking: could a F9530N (100V N-channel mosfet, TO220) replace a BSP372 (60V N-channel mosfet, SOT223-3)?
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Resistor for speaker volume reduction

May 18, 2015, 3:16 pm
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Hi folks,

I have no electronics background whatsoever. I scanned links on the web, this site appears to be the best candidate for an educated response.

I have replaced the speakers in my auto with Audison units. In the corners of the front dash are 3 inch midranges. The Audison are apparently more efficient and the volume needs to be reduced a bit. A fellow in the Audi club forums indicated that a 2 ohm resistor balanced the output of the dash speakers well with the rest.

My concern is that placing anything into the signal path will impact resolution. Granted, it's a car and poor place for good sound to begin with. But after paying what I did to replace all the speakers with Audison, I'm interested in ensuring that the signal quality is true to the source as possible.

Is there a certain type of capacitor, or brand, or both that I should consider? I don't know the wattage output to the 3" dash speakers, however they are 4 ohm.

Thank you for any advice that you can offer.
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Waveform deformation and voltage drop in transformer

May 18, 2015, 6:50 pm
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Hi! I have a EE42 N87 core working at 200KHz, 200mT on a Half-Bridge power supply. Everything works great expect that I experience a voltage drop when applying load. The reason seems to be in the transformer, here are the waveforms:

With a 16 Ohm load:
Click the image to open in full size.

With a 4 Ohm load:
Click the image to open in full size.

The primary side has 9 turns with 16 wires of 0.3mm of diameter. The secondary is 4 turns with a 0.1mm copper foil, however, I couldn't find a way to easily connect the foil to the terminals so I used a high temperature cable I had soldered in the copper foil to the terminals. This is the cable used:

Click the image to open in full size.

Connected on this way (replace the copper wires with the cable):

Click the image to open in full size.

Is this termination on the secondary side responsible for this voltage drop?
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Q Acoustics 2050i

May 18, 2015, 7:07 pm
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What is Q acoustics doing to win so many awards? Anyone have any idea's?
They obviously have a step on the competition... Crazy...
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Converting 3rd order Butterworth to aB

May 18, 2015, 7:52 pm
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I am in the process of rebuilding my Barry Hughes' bookshelf (HiFi Answers July 1978). The original crossover was the Falcon Acoustics 21B. The high pass section for the Audax HD12x9D25 has the following components:

R2=2.4ohm (series dropping resistance)
L3=0.22mH
C2=4.7uF
C3=5 uF

I would like to change the HF section to acoustic Butterworth. I found some information on the KEF 104aB and the transformation equations in Martin Colloms book, "High Performance Loudspeakers", Pentech Press, 1980. The Falcon crossover is reasonably close to the KEF 104 values. But Martin left out some steps in his book, making the transformation from the Falcon 21B to acoustic Butterworth.

The C2 and C3 above is equivalent to the C1 and C2 in Fig-15 or Martin's book. Martin left out how to determine the value of C3 which is series with the coil. The aB component values in Fig-17 is possible using the equations in Fig-16 only if the C3 value in Fig-15 is negative!

Anyone can point me to a reference of acoustic Butterworth transformation that actually works? Many thanks.
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Stereo Subwoofers: How does one go about it?

May 18, 2015, 8:36 pm
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Hey, guys

I was curious as what to what your guys' thoughts were on setting up a dual/stereo subwoofer is like. Is it worth the trouble? How do you go about it? What amps would you use to integrate them with the satellites?

Essentially looking to build a 2.2 system.

...Or is it not wholly worth the trouble of setting them up and integrating them with the mains



Many thanks in advance/Much love everyone
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2-way speakers for old radio mod with TA2024

May 18, 2015, 10:38 pm
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Hello! I have been requested to mod an old radio to work on 12v sla battery and class T(D) amp. I have made something like the boominator before, but I used fullrange speakers. Now in this project I was asked to use 2-way speakers and we agreed to make as few visible and/or permanent mods to the old radio chassis. I was thinking to make an enclosure for the speakers to be put inside the radio chassis and use some kit from the internet. But I can't find any to match my criteria.

The radio is about 59cm wide, 32cm tall and only 23cm deep (outer measurements). Also the radio controls take up some space in the front panel like this. Now this means that the speakers would need to be mounted horizontally and near each other to have room for both elements. I said that fullranges would be easier...

Anyway, this means that the speakers should be 25cm tall at maximum (and then mounted horizontally) and around 18cm wide and <23cm deep. Also I want them to be 4 ohm to get the most out of the amp. And not too expensive, max. 200eur for parts for both, including crossovers. See why I have not found them....

Is it easier to select budget speakers and use some simulator to calc dimensions and crossover or to keep looking for ready plans? Help would be appriciated, if anyone knows something like I described above that would be nice :)

I have found these but the elements are a bit too expensive.
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Need help with DWM1216 driver board

May 19, 2015, 12:12 am
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So outputs on this Hifonics Brutus 2608 were shorted. Found Q7 (2d) on driver board to be shorted. Replaced both 2D's (Q7 and Q19) as well as 1d's (Q11,Q22). Also found R24 (180ohm) to be bad, and replaced it as well. Checked all driver transistors (AG and DK) and all tested good. Checked all 470 ohm resistors and those as well were good.

When I power up the amplifier it powers on and does not seem to draw any excess current, but I get no square wave on the outputs gate pads, and the 2d transistors on the driver board are getting hot enough to slightly smoke after just a few seconds It's hard to tell exactly where the smoke is coming from because it's very very faint. The driver transistors also seem to get warm.

There are no output FETs installed.
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Audison LRX2 with no sound

May 19, 2015, 1:44 am
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Hi guys,

new day, new problem :-)

Audison LRX2 150.

It turns on (green light on, red lights off); the power supply is ON with +27 V, -27 V, +12 V, -12V but there is no sound on the speakers. I think there is some kind of protection on the sound signal (mute), but I don't have any schematics or instructions.

Could you help me ?

Thanks

Giovanni
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ir remote, control signal, or audio input power on circuitry?

May 19, 2015, 2:11 pm
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I'm wondering if anyone knows of somewhere I can buy a already designed and troubleshot circuit board that controls power on - ideally via IR remote, audio input signal detection, or an external control source like a pre-amp output signal. If I don't find anything already done I can probably breadboard something together, at the very least for the external signal, but given the level to which the rest of this amp is going to be done I'd like something that is better that what I know I'll probably come up with left to my own devices :)

Thanks!
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Building a decent input switcher

May 19, 2015, 2:21 pm
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Hi,

Thanks for reading! I want to make an input selector since my active speakers have only one input and using my surround processor degrades the sound of my dac (which has a built in preamp). The dac direct connected to the speakers sounds a lot better but switching cables all the time is not convenient for me.

The only requirements are: 2 inputs, one output with the best soundquality possible.

I looked at commercial available equipment like the dodocus (but it degrades the sound) or manley skipjack (too expensive and to many options I don't use).

I do want to keep things rather simple and have something like this in mind:
Click the image to open in full size.

Since I want the input selector to be as transparant as possible I am looking for recommendations of parts I should use.

Does something like a DACT CT3 degrade the sound? Should I use another kind of switch? What kind of bindingposts and internal cables are recommended?
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Mono blocks for woofers: Ncore, AMS or ?

May 19, 2015, 3:07 pm
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I am using the digital crossover of my Devialet amp for my DIY speakers. Mid/highs are fed by the Devialet amp but for the woofers I am using the low pass analog out (RCA) and using Kharma MP150 amplifiers to drive the woofer. The woofers are Accuton S280 rated 93dB/2.83V 6.6Ω 150W max and I am quite happy with their sound in my large room.
The Kharma MP150 are Hypex UcD based and where much better than the Hypex UCD 180 when I tested these almost a decade ago. But the MP150 are getting noiser and they are really noisy when they are not connected to the preamp (Devialet off). So I am thinking to replace them with a newer and better digital amp and would like to get some recommendations for mono blocks:
Option 1: Hypex N-core400 + SMPS600
Option2: Anaview AMS0100 or AMS100 either of them in bridged mode. The AMS0100 has somewhat better measurements and might have enough power (100W) but which sounds better?
Option 3 any other suggestion?
Both Hypex and Anaview are primarily designed for balanced input (but allow also single ended) but the pre out (analog) of my Devialet is single ended only. Are there any sound quality issues by not using balanced connctions(especially noise which I want to eliminate)?
Thanks for any input!
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reparing old amplifier tectronic sa 535

May 19, 2015, 3:07 pm
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Hello everyone,

I'm trying to repair an old amplifier named tectronic SA 535. More for the challenge than for the sound but yeah also for the sound (curiosity)!

From what i understood, the schema is the same as scott A417.

The problem remains is about an output dc offset really high (-37v ) on the right channel. The power transistors (and drivers...) was checked using diode mode of dmm and nothing different from the left channel that works.

So, I would like your opinion in order to identify the cause.

I suppose that one of transistor (power pnp ?) is fully closed, so the based should be saturated. right ?

My first idea is to replace electrolytic capacitor that should have near 40 years old now. Maybe one is in short circuit ?

In the past, i saw a resistor cause problem on an old metrix multimeter. So , checking resistor is the second idea.

And finally, checking all the others transistors, maybe for found one that is "blocked".

maybe there is better way (shortcut ?) to indentify the problem ?
What could you recommend to do ?



thank you for your help.
by a noob!
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FS:rare Tribute Audio output transformers pair

May 19, 2015, 3:10 pm
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Hello,
I'm selling my Tribute output tranformers for 300b used but in perfect conditions. They weight about 4Kg each and sound super.
I bought from Pieter some years ago.
I'd like to get 300eur+paypal fees (in Europe bank transfer is also ok) and shipping.
Regards
Guglielmo

Attached Images
File Type: jpg IMG_0326.jpg (1.05 MB)
File Type: jpg IMG_0322.jpg (771.8 KB)
File Type: jpg IMG_0323.jpg (744.7 KB)
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Next Project Suggestions - ff85wk?

May 19, 2015, 3:49 pm
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Been a lurker here for a long time and wanted to get opinions on my next build. Just finished my first project with Fostex drivers, a BLH with the FF125wk and I like it but am thinking my next project will be something smaller.

Is the Lance about the best enclosure for the FF85wk? I was thinking of ordering a pair to try them out.
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DIY woofer wave guides, They work!

May 19, 2015, 4:11 pm
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Hey everyone,

I just wanted to share this one. I was looking into ways to improve dispersion of large diameter woofers to increase the crossover frequency. I have a set of Cerwin Vega 300 SE speakers for playing around with. They are perfect because the woofers are run full range.

I used a piece of 3/8 cast acrylic, cut it out with a jigsaw. Flame polished the edges and used a propane torch to bend the middle in. I'll post the template.

The results are better than I expected. The waveguides completely removed the 7db peak at 1.5k. the speakers sound much more open and the sweet spot has changed from about 12" to several feet. I didn't do much off axis measuring, since I was using my laptop for the tone generator and it just didn't have enough output to get any consistent results.

I thought the results where pretty amazing so I had my wife come in, and do a blind A-B comparison. She said the one sounded richer, so the wave guides have 2 positive votes. I think these could be the answer for a lot of problems.

Jordon

Attached Images
File Type: jpg cerwin vega waveguide diy (2).jpg (478.8 KB)
File Type: jpg cerwin vega waveguide diy (1).jpg (536.3 KB)
Attached Files
File Type: pdf 12 woofer wave guide.pdf (4.3 KB)
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Air bearing tonearm problem

May 19, 2015, 4:16 pm
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I built my 1st air bearing arm and love it so much that I decided to build 2nd one. The construction of 2nd arm is similar to Walker Audio’s. Please see attached image.

First air bearing arm link.

http://www.diyaudio.com/forums/analo...inear-arm.html

Although I still have a technical problem, I managed to play it. The sound from 2nd one is even better than 1st one. It is free of artifacts. The sound is so smooth and full 3D with the authority in bass. It even changes my impressions of some of my cartridges.

However, I still have a problem to solve.

I use two .5 inch Oav air bushings. The shaft is 11 inches long 2024 aerospace aluminum tubing. It weighs 30 grams.

The first construction I did is A in the attached image. But it bonus back and forth. I attached a video to show you that.

YouTube Video.

https://youtu.be/pEWht49wbT4

So, I tried the construction B. In construction B, I can play but there is still a tiny force to pull the shaft inwards at most outer groove. Once the needle passes certain point, there is a tiny force to push the shaft out. I had to raise the rear end of the arm a little higher to compensate the pushing force.

I have no idea what causes this. The shaft is pretty straight. Its tolerance in roundness and diameter is about .05 mm.If anyone had built similar kind of tonearm or you have the experience with air bushings, I need your advice how to solve this problem. Otherwise, I have to be very careful when I play the records. It also makes me feel uncomfortable to know there is tiny force is pulling the needle at beginning of playing.

Attached Images
File Type: jpg 2nd air bearing 1.jpg (552.8 KB)
File Type: jpg 2nd air bearing 2.jpg (227.7 KB)
File Type: jpg 2nd air bearing 3.jpg (411.0 KB)
File Type: jpg air-bearing-problem.jpg (137.2 KB)
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Board mount SMPS for a preamp or active crossover

May 19, 2015, 6:35 pm
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Question about using small "potted" board mount SMPS with low power audio circuits like preamps or active crossovers.

I've been playing with this circuit: 12dB / Octave Linkwitz Riley Crossover, and I quite like the result. For power it needs +/- 12v at order of magnitude 100mA current.

I am thinking of using a supply like Digikey p/n 945-2097-5-ND or the like because I can fit the entire lot into a small box.

I would escape the supply rails with (say) parallel 100n film + 1n ceramic caps and maybe series inductors if need be. I think this would keep the voltage clean.

Question is whether I can expect problems with radiated EMI or noise from the SMPS?

Thanks in advance!

BTW - attached pics of the power amp I'm using, some of you might know it well!

Attached Images
File Type: jpg DSC_0087.jpg (711.3 KB)
File Type: jpg DSC_0089.jpg (601.3 KB)
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In search of the snap

May 19, 2015, 6:56 pm
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I've heard the snap while listening to only a few home speakers. I want my speakers to snap!

"snap" here is being defined as being able to "accurately" reproduce the sound of a small diameter drum, a finger snap or a clap. I'm looking for that tight tactile character. The kind that almost hits you in the forehead.

Pro audio horn loaded systems seem to be able to reproduce it very well. The best reproduction of it that I've heard came from a three way all horned loaded pro audio system. That was a large speaker not suitable for the home environment.

I've also heard the snap while listening to a few speakers in the near field (1.5ft from speaker to my ear). Those same speakers lost the snap when I listened to them at the typical (for a home system) distance of 6-7ft.

Some earbuds can reproduce the snap quite well and much better than many speakers.

How does one design a home speaker with this snap?

Should the design criteria include:

- high sensitivity? no in my experience because I've heard good snap from small satellites with 3.5" woofers and low sensitivity

- lack of early reflections? earbud, horn loaded system, and nearfield snap seem to indicate that this could be a requirement but I've also heard it from speakers with good dispersion in a small room

- acoustic suspension bass? heard snap from ported speakers so my vote here is no

- limited low frequency extension? All the speakers I've heard with good snap didn't have excess LF output and some had very little output below 80Hz.


Can anyone share a proven formula for the snap or thoughts about what may be required to achieve it? thanks to all contributors!
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