Input board w/rows of vias to reduce crosstalk... Good idea? Or bad idea?
- By meq123
- Analog Line Level
- 10 Replies
Attachments
DC speaker protect circuit.
- Swap Meet
- 2 Replies
150WRMS into 4 ohms or 300WRMS into 8 ohms.
Mains powered.
Uses solid state relay for longer life.
Four second power on anti thump delay.
If unit see DC for about 500mS it disconnects amplifier from speaker
£14.99 plus p+p
p+p is £4.50 to uk. £9.99 to Europe and £17.99 to rest of world.
I have 2 for sale.
Mains powered.
Uses solid state relay for longer life.
Four second power on anti thump delay.
If unit see DC for about 500mS it disconnects amplifier from speaker
£14.99 plus p+p
p+p is £4.50 to uk. £9.99 to Europe and £17.99 to rest of world.
I have 2 for sale.
35+35 watts stereo hybrid amplifier module
- Swap Meet
- 1 Replies
£20 +p+p
p+p is £5 to uk, £10 to europe and £15 to rest of world.
Use your own valve. 12au7, 12ax7 12at7
p+p is £5 to uk, £10 to europe and £15 to rest of world.
Use your own valve. 12au7, 12ax7 12at7
100 watt hybrid amplifier module
- Swap Meet
- 1 Replies
£20 + p+p
p+p is £5 to uk, £10 to europe and £15 to rest of world.
Mono.
Use your own valve 12ax7, 12au7 or 12at7.
p+p is £5 to uk, £10 to europe and £15 to rest of world.
Mono.
Use your own valve 12ax7, 12au7 or 12at7.
Non-linearities of cored inductors
I start this thread, because the subject of inductor linearity was raised in this discussion:
https://www.diyaudio.com/forums/equ...software-distortion-analyzer-post6199594.html
As I am also interested in the subject, I carried out some tests.
I tested three very different types of materials: a general-purpose manganese ferrite (grade 3H1), a VHF nickel ferrite (grade 4C4), and an iron-powder/polymer composite of unknown origin.
These are relatively old materials, but the data is still indicative, and more modern grades improve on saturation limit, temperature stability, HF behavior, losses -not on linearity-.
In the days of FDM telephony, linearity had some importance, but that's no longer the case.
I made the tests on X22 cores: they are convenient to work with, and I have plenty of them.
As I hate winding works, I used salvaged, already wound coil-formers as test windings.
This means that I didn't have the choice of the number of turns, but it doesn't really matter: the results have to be normalized anyway.
The tests were made for a zero airgap: what interests us is the core non-linearity for a given induction.
In an actual inductor, this non-linearity will become "diluted" by various factors, but by knowing the source value, it is possible to compute the non-linearity for any situation.
Here is the test-jig for the 3H1:
The 1K series resistor is calculated to be ~equal to the reactance of the inductor at the test frequency. It will be the load seen by the harmonics generated by the coil.
The test voltage was varied from 72mV to 2.2Vrms, resulting in a peak induction comprised between 1.293mT and 39.5mT.
Here are the results:
There seems to be a quasi-linear dependency of the non-linearity with the excitation level.
These raw figures will be reduced if an airgap is added.
This is the equivalent circuit with an airgap: the reluctances on the left, and the electrical equivalent on the right.
It is obvious that by making Lgap much smaller than Lcore, the THD will be reduced in the same proportion.
Lgap can be computed : n²*µo*Ae/d (Ae= effective area, d= airgap).
The distortion will also be reduced if the excitation level is reduced.
It is counter-intuitive, but adding a gap will not directly reduce the induction: the induction formula does not include any magnetic parameter.
However if the gap is increased, the inductance will decrease and if the excitation voltage and frequency are kept identical, the current will increase, and the greater H will compensate exactly the increased reluctance.
Of course, in general the coil will be adapted to keep the same value with an increased airgap: this means increasing the number of turns by √r, and this will reduce the induction.
Here is a pic of the cores tested:
The 4C4 cores are clamped by a nylon bolt, but the 3H1's have a threaded insert and require an external clamp (or the proper mounting hardware).
The iron-powder core is an horrible kludge, more on that later
https://www.diyaudio.com/forums/equ...software-distortion-analyzer-post6199594.html
As I am also interested in the subject, I carried out some tests.
I tested three very different types of materials: a general-purpose manganese ferrite (grade 3H1), a VHF nickel ferrite (grade 4C4), and an iron-powder/polymer composite of unknown origin.
These are relatively old materials, but the data is still indicative, and more modern grades improve on saturation limit, temperature stability, HF behavior, losses -not on linearity-.
In the days of FDM telephony, linearity had some importance, but that's no longer the case.
I made the tests on X22 cores: they are convenient to work with, and I have plenty of them.
As I hate winding works, I used salvaged, already wound coil-formers as test windings.
This means that I didn't have the choice of the number of turns, but it doesn't really matter: the results have to be normalized anyway.
The tests were made for a zero airgap: what interests us is the core non-linearity for a given induction.
In an actual inductor, this non-linearity will become "diluted" by various factors, but by knowing the source value, it is possible to compute the non-linearity for any situation.
Here is the test-jig for the 3H1:
The 1K series resistor is calculated to be ~equal to the reactance of the inductor at the test frequency. It will be the load seen by the harmonics generated by the coil.
The test voltage was varied from 72mV to 2.2Vrms, resulting in a peak induction comprised between 1.293mT and 39.5mT.
Here are the results:
Code:
^B(mT) k(%)
1.293 0.023
3.95 0.062
12.93 0.175
39.5 0.45There seems to be a quasi-linear dependency of the non-linearity with the excitation level.
These raw figures will be reduced if an airgap is added.
This is the equivalent circuit with an airgap: the reluctances on the left, and the electrical equivalent on the right.
It is obvious that by making Lgap much smaller than Lcore, the THD will be reduced in the same proportion.
Lgap can be computed : n²*µo*Ae/d (Ae= effective area, d= airgap).
The distortion will also be reduced if the excitation level is reduced.
It is counter-intuitive, but adding a gap will not directly reduce the induction: the induction formula does not include any magnetic parameter.
However if the gap is increased, the inductance will decrease and if the excitation voltage and frequency are kept identical, the current will increase, and the greater H will compensate exactly the increased reluctance.
Of course, in general the coil will be adapted to keep the same value with an increased airgap: this means increasing the number of turns by √r, and this will reduce the induction.
Here is a pic of the cores tested:
The 4C4 cores are clamped by a nylon bolt, but the 3H1's have a threaded insert and require an external clamp (or the proper mounting hardware).
The iron-powder core is an horrible kludge, more on that later
Attachments
Help identifying Altec cabinet/model/plans
Long time listener, first time caller...
I've been looking to start an Altec project.
These cabinets have really gotten my attention.
They claim they're 820's, but the only info on 820's I can find is about corner loaded 821 or 820a/c. Those were driven with 2x803 for LF and 802/H808 for HF. Nothing about this style cabinet. They say the dimensions are Cabinet Dimension(each): 29 3/4" x 23 3/4" x 48"(inches), and the ~24" depth is very appealing to me.
Anyway, I'm looking for any info on these as I'd consider building a pair if I had more to go off of. Maybe this cabinet could benefit from reflex porting like the 817? Has anyone seen cabinets like this? Or similar plans?
If any of you are familiar with these, would you search for 803LF drivers? Would 416s or 515s "work"?
Thanks!
z
Here are the photos from the ad
![URL]](/community/proxy.php?image=http%3A%2F%2F%5BURL%3D%22https%3A%2F%2Fwww.lajazz.jp%2Fimages%2FAudio%2FDH%2FAltec_820%2FAltec_820_Obi1.jpg%22%5Dhttps%3A%2F%2Fwww.lajazz.jp%2Fimages%2FAudio%2FDH%2FAltec_820%2FAltec_820_Obi1.jpg%5B%2FURL%5D&hash=7864bc75ef3032bd711beda5c5430f4e)
I've been looking to start an Altec project.
These cabinets have really gotten my attention.
They claim they're 820's, but the only info on 820's I can find is about corner loaded 821 or 820a/c. Those were driven with 2x803 for LF and 802/H808 for HF. Nothing about this style cabinet. They say the dimensions are Cabinet Dimension(each): 29 3/4" x 23 3/4" x 48"(inches), and the ~24" depth is very appealing to me.
Anyway, I'm looking for any info on these as I'd consider building a pair if I had more to go off of. Maybe this cabinet could benefit from reflex porting like the 817? Has anyone seen cabinets like this? Or similar plans?
If any of you are familiar with these, would you search for 803LF drivers? Would 416s or 515s "work"?
Thanks!
z
Here are the photos from the ad
can this type of coil be used on the output of amplifier ?
- By Bernhard
- Solid State
- 10 Replies
Attachments
Rate my 2-way horn speaker + subwoofer
Hi,
I recently finished my very first project that I want to share with you. Maybe you find some things I can improve. Parts I used:
-Faital Pro HF10AK in 12“ tractrix
-B&C 12PE32 in ~20L cb
-4x Beyma 12BR70 as subwoofers in ~70L (2x) and 80L (2x) cb
-DSP with 8 channels
Unfortunately I don’t have proper pics on my computer. But maybe you get the idea from my profile picture. Every driver has its own box. The speakers are placed in the corners of the room. You can find a sketch down below.
This is how the final measurements looks like:
Crossed @1,1kHz with LR 36db filter. This filter was the best sounding and also the best in the measurements. The compression driver is delayed due to the bigger distance to the mic. It was done by trial & error. With a delay of 0,6ms and an inverted midbass I got the biggest dip at the xover frequency. Not a single band of the EQ is left for the CD. But the final FR is pretty flat.
It was measured 1m from the baffle with an calibrated mic on the level of the CD (ear height). Because of the low height I get the reflexions from the ground prette early. I placed an absorber in front of the speaker. You can see the impulse with the window set here:
The off axis response looks like this:
The narrow dispersion of the horn works well with corner placement imo.
Low frequency integration was a bit tricky. With 1m distance to the mic the measurements go down to about 350Hz. Nearfield measurements are only valid up to 200Hz. But the nearfield measurement (and also the simulation) shows that FR of the 12PE32 is not flat at all:
Below 200Hz it’s loosing energy. First I crossed the subs at 80Hz with LR filters. But the measurements on the listening position with mic at 90° showed that the range of ~80-200Hz is lacking. This was audible too. I could try to push the low frequencies on the midbass. But since the xmax is limited (2,8mm) I decided to cross the subs higher.
The front subs are connected to same channel of the DSP & amp. And the back subs are connected to one channel as well. This is because I only have three stereo amps at the moment. So I can’t EQ and delay every single sub seperately. Here is a sketch of the room before I show you the measurements at the listening position.
The main speakers are placed on top of the front subs in the corner. I marked my listening position. The sub in the right back corner stands under a desk. I pulled it out of the corner a bit due to the legs of the desk. And I think this is one reason why got this response at the listening position:
The mains got a hp at 120Hz with Bessel 12dB. The front subs are crossed at 120Hz with Bessel 18dB. The back subs are crossed at 100Hz with Bessel 18dB and delayed a little bit. This was done by trial & error. With this filter setup I get pretty flat response from 20-200Hz. What I mean is that the sub frequencies and the kick bass are on the same level. Of course on every other position in the room the bass gets worse because of the eq settings and modes.
What was surprising to me is that I got this kind of bass response near the center of the room. In my first tests with every sub in the corner (especially the one in the right back corner) the bass was best sounding in the back of the room. Towards the center it got worse. But with pulling one sub out of the corner a bit the situation switched.
Here are some more measurements. The red curve is withouth EQ.
Things I didn’t measure or focus so far:
-Impedance
-Group delay
-Phase settings in the DSP (I just used delays to compensate physical distance)
What do you think about my project? Is the subwoofer integration done well? Or is it worth to try Geddes approach with different placement?
I recently finished my very first project that I want to share with you. Maybe you find some things I can improve. Parts I used:
-Faital Pro HF10AK in 12“ tractrix
-B&C 12PE32 in ~20L cb
-4x Beyma 12BR70 as subwoofers in ~70L (2x) and 80L (2x) cb
-DSP with 8 channels
Unfortunately I don’t have proper pics on my computer. But maybe you get the idea from my profile picture. Every driver has its own box. The speakers are placed in the corners of the room. You can find a sketch down below.
This is how the final measurements looks like:
Crossed @1,1kHz with LR 36db filter. This filter was the best sounding and also the best in the measurements. The compression driver is delayed due to the bigger distance to the mic. It was done by trial & error. With a delay of 0,6ms and an inverted midbass I got the biggest dip at the xover frequency. Not a single band of the EQ is left for the CD. But the final FR is pretty flat.
It was measured 1m from the baffle with an calibrated mic on the level of the CD (ear height). Because of the low height I get the reflexions from the ground prette early. I placed an absorber in front of the speaker. You can see the impulse with the window set here:
The off axis response looks like this:
The narrow dispersion of the horn works well with corner placement imo.
Low frequency integration was a bit tricky. With 1m distance to the mic the measurements go down to about 350Hz. Nearfield measurements are only valid up to 200Hz. But the nearfield measurement (and also the simulation) shows that FR of the 12PE32 is not flat at all:
Below 200Hz it’s loosing energy. First I crossed the subs at 80Hz with LR filters. But the measurements on the listening position with mic at 90° showed that the range of ~80-200Hz is lacking. This was audible too. I could try to push the low frequencies on the midbass. But since the xmax is limited (2,8mm) I decided to cross the subs higher.
The front subs are connected to same channel of the DSP & amp. And the back subs are connected to one channel as well. This is because I only have three stereo amps at the moment. So I can’t EQ and delay every single sub seperately. Here is a sketch of the room before I show you the measurements at the listening position.
The main speakers are placed on top of the front subs in the corner. I marked my listening position. The sub in the right back corner stands under a desk. I pulled it out of the corner a bit due to the legs of the desk. And I think this is one reason why got this response at the listening position:
The mains got a hp at 120Hz with Bessel 12dB. The front subs are crossed at 120Hz with Bessel 18dB. The back subs are crossed at 100Hz with Bessel 18dB and delayed a little bit. This was done by trial & error. With this filter setup I get pretty flat response from 20-200Hz. What I mean is that the sub frequencies and the kick bass are on the same level. Of course on every other position in the room the bass gets worse because of the eq settings and modes.
What was surprising to me is that I got this kind of bass response near the center of the room. In my first tests with every sub in the corner (especially the one in the right back corner) the bass was best sounding in the back of the room. Towards the center it got worse. But with pulling one sub out of the corner a bit the situation switched.
Here are some more measurements. The red curve is withouth EQ.
Things I didn’t measure or focus so far:
-Impedance
-Group delay
-Phase settings in the DSP (I just used delays to compensate physical distance)
What do you think about my project? Is the subwoofer integration done well? Or is it worth to try Geddes approach with different placement?
