An Improved Array
- Multi-Way
- 206 Replies
I had some time off work, so I've been trying to decipher how the Beolab 90 works. I'm looking forward to hearing it again in a couple weeks. (At CES.)
While studying the patents, I stumbled across an interesting one from Enrique Stiles. In this thread I'll take a stab at describing it.
Mr Stiles' patent is based on the work of Philips. About 35 years ago, Philips patented a novel array named 'the Bessel array.'
The concept of the Bessel array is very simple:
In a conventional line array, the elements sum constructively at low frequency, and destructively at high frequency. Specifically, they'll sum destructively when the frequencies reproduced are shorter than the center-to-center spacing, and they'll sum constructively when the frequencies reproduced are longer than the frequencies reproduced.
The reason that this happens is due to phase and amplitude. At low frequencies, all of the array elements are in phase due to the long wavelengths. At high frequencies, this is no longer true, because the wavelengths are so short. And this gets worse the further you go off axis. (Due to the phase differences.)
So the Bessel array addresses the phase and amplitude issues in two ways. First, two of the five elements are driven with a reduced amplitude. Second, the phase of one element is flipped.
The net result is an improvement in the off-axis response, at the expense of overall amplitude. The overall output of a five element Bessel array is equivalent to the output of a two element line array.
More info can be found here : http://www.diyaudio.com/forums/multi-way/38523-bessel-array.html
Arguably, nearly all attempts to improve array performance are based on attempts to manipulate the phase and amplitude of the array elements. For instance, 'shading' manipulates the amplitude. CBT arrays manipulate phase via physical placement, and also 'shade' the array. IMHO, 'log spaced arrays' are a clever method of shading an array without modifying the voltage.
Here's a comparison of a conventional five element array, versus a five element Bessel array. Note the improvement in off-axis response, at the expense of overall output. Data is source from Mr Stiles' patent, #US20060018491 A1
While studying the patents, I stumbled across an interesting one from Enrique Stiles. In this thread I'll take a stab at describing it.
Mr Stiles' patent is based on the work of Philips. About 35 years ago, Philips patented a novel array named 'the Bessel array.'
The concept of the Bessel array is very simple:
In a conventional line array, the elements sum constructively at low frequency, and destructively at high frequency. Specifically, they'll sum destructively when the frequencies reproduced are shorter than the center-to-center spacing, and they'll sum constructively when the frequencies reproduced are longer than the frequencies reproduced.
The reason that this happens is due to phase and amplitude. At low frequencies, all of the array elements are in phase due to the long wavelengths. At high frequencies, this is no longer true, because the wavelengths are so short. And this gets worse the further you go off axis. (Due to the phase differences.)
So the Bessel array addresses the phase and amplitude issues in two ways. First, two of the five elements are driven with a reduced amplitude. Second, the phase of one element is flipped.
The net result is an improvement in the off-axis response, at the expense of overall amplitude. The overall output of a five element Bessel array is equivalent to the output of a two element line array.
More info can be found here : http://www.diyaudio.com/forums/multi-way/38523-bessel-array.html
Arguably, nearly all attempts to improve array performance are based on attempts to manipulate the phase and amplitude of the array elements. For instance, 'shading' manipulates the amplitude. CBT arrays manipulate phase via physical placement, and also 'shade' the array. IMHO, 'log spaced arrays' are a clever method of shading an array without modifying the voltage.
Here's a comparison of a conventional five element array, versus a five element Bessel array. Note the improvement in off-axis response, at the expense of overall output. Data is source from Mr Stiles' patent, #US20060018491 A1
transformer sizing for 1 channel of LM3886 amp
- By mrjayviper
- Chip Amps
- 5 Replies
assuming the supply voltage is more suitable for an 8-ohm load than a 4.
This is the complete circuit for 1 channel.
Thanks a lot.
This is the complete circuit for 1 channel.
Thanks a lot.
Linn LP12 Trampolin Kit
- By wmeyer57
- Analogue Source
- 5 Replies
Hi, everybody out there,
this is my first post on this forum. I'm using a fully equipped LP12 as a main source for listening. This means: LP12, Aro, Armageddon, Cirkus-Kit, Trampolin-Kit, Benz Ruby 3 Cartridge.
I'm lookin for your experience with the Trampolin Kit. Is it useful, if one has a really rigid stand? Does it better the sound... or not...
I'm very keen to read about your experiences.
Have a nice time.
Wolfgang
this is my first post on this forum. I'm using a fully equipped LP12 as a main source for listening. This means: LP12, Aro, Armageddon, Cirkus-Kit, Trampolin-Kit, Benz Ruby 3 Cartridge.
I'm lookin for your experience with the Trampolin Kit. Is it useful, if one has a really rigid stand? Does it better the sound... or not...
I'm very keen to read about your experiences.
Have a nice time.
Wolfgang
Low Power Subwoofer Modeling
- By MalVeauX
- Subwoofers
- 26 Replies
Hi all,
Forgive me if some of this is not correct, I'm new to designing loudspeakers and subs but I'm really eager to learn more. I've been dabbling with modeling software for about a week now and playing around with various drivers and enclosures to get a better idea of things.
The application is home theater with my primary interest, from a subwoofer duty being 20hz to 80hz. I'm not looking at this time to hit reference at 15hz or less or anything.
Anyhow, I got really interested in the awesome VBSS design (by MTG) and then went down the rabbit hole of looking for ways to build either efficient or sensitive speakers, or both really, and then use DSP to limit the driver. So I started modeling with inexpensive drivers in various cabinets and came up with my own variation of the idea with similar hardware, but instead of using high powered amps, I'm looking at it from the perspective of... could this run off 50 watts at 8ohms? This makes amplification a breeze. To build SPL, it would be done with several units. This may be flawed thinking, so please, let me know where I'm falling off the cliff if I am!
Here's what I'm currently thinking about and modeling:
Slot vented MDF based enclosure, 24" x 22" x 18.45" with a 20hz tuning frequency. Net internal volume is 4 cubic feet (taking into account the driver displacement, etc, maybe a little more for bracing). I originally had a larger cabinet but the driver excursion was getting out of hand. 20hz is chosen to get that high SPL output with minimal excursion from the driver, so that the woofer is only really having to stress around 30~35hz with its excursion (if I modeled it correctly).
I'm modeling with the GRS 18PT-8 18" Pro Driver (8ohm). It's only $70.
Here's the driver excursion relative to xmax:
I applied a few filters to control the driver. A highpass filter at 17hz. A lowpass filter at 200hz, but this could be at 110~120hz, it won't matter much as I will crossover. PEQ +15db at 20hz with Q of 0.75 to boost the near port output without asking the driver to have high excursion while doing it (I think?). PEQ -8db centered on 55hz with Q of 1.4 to smooth out the peak that was there and further drop excursion. The resulting excursion model in this box at the intended signal input is graphed below, so that the driver doesn't exceed xmax until well under port tuning frequency which I will cut off.
For the slot vent, it's 1.0" x 20.74" x 29.74" in this enclosure to produce the 20hz tuning frequency, but also to limit air velocity from the slot at the intended input signal so that it doesn't exceed 18, conventional wisdom being this will eliminate the chuffing sound.
Those models and filters in place, the following is the SPL graph result.
This is where things get sketchy maybe. I'm modeling this based on a 10 foot distance from the driver face to the listening position and an input of only 50 watts at 8 ohms. I know this is nothing outstanding, but for me this is interesting because for just 50 watts, I'm looking at a nice curve to start working with from just one sub and only 50 watts of power that will be very stable to run. The goal will be to build several of these, 4 of them to start. So the idea is that if I'm getting potentially 96db at 20hz and up, when I add the 2nd sub, I could expect to be close to 100db at 20hz, and add two more and get closer to 105db potentially at 20hz, before room gain (sealed room).
I already have a miniDSP HD 2x4 that I use, so I would use that to align the subs and produce the summation virtual sub and then EQ that for a gentle house curve, based on whatever the 20hz performance ends up at.
I already have an AudioSource AMP100 amp that does 50 watts into 8ohms, two channels, with a nice big power supply. These are inexpensive and pretty solid. I could add another for the 2nd pair of subs. I probably could get way cheaper amplifiers for this, but I'm not certain of quality in tiny class D amps around 50 watts into 8ohms out there with good quality output down to 20hz. I'm totally open to suggestions if you have them!
So end result would be 4 of these enclosures, each running at 50 watts max, for a very low total power draw running full tilt at all times if wanted, stable. Again, from the standpoint of 10 feet distance to the subs (they would be in a sealed room 10 feet from the listening position area) in the home theater room.
If this is modeled properly, and will work (I have my doubts, which is why I'm asking!) the break down is:
Driver x 4 at $70 each, so $280
MDF, glue, screws, terminal binding posts, typical wire, x 4 - $200
Amp x 2 at $150 each, $300
About $780 for this project, unpainted. I would probably just black paint it matte or duratex type look, utilitarian.
Do you all think this is plausible?
Are the models ok or is something horribly wrong?
I do realize there are limits here, and that asking this system to do more than its max is not going to go anywhere. I modeled it for its max use and distance in the room for its purpose.
Any input appreciated.
Very best,
Forgive me if some of this is not correct, I'm new to designing loudspeakers and subs but I'm really eager to learn more. I've been dabbling with modeling software for about a week now and playing around with various drivers and enclosures to get a better idea of things.
The application is home theater with my primary interest, from a subwoofer duty being 20hz to 80hz. I'm not looking at this time to hit reference at 15hz or less or anything.
Anyhow, I got really interested in the awesome VBSS design (by MTG) and then went down the rabbit hole of looking for ways to build either efficient or sensitive speakers, or both really, and then use DSP to limit the driver. So I started modeling with inexpensive drivers in various cabinets and came up with my own variation of the idea with similar hardware, but instead of using high powered amps, I'm looking at it from the perspective of... could this run off 50 watts at 8ohms? This makes amplification a breeze. To build SPL, it would be done with several units. This may be flawed thinking, so please, let me know where I'm falling off the cliff if I am!
Here's what I'm currently thinking about and modeling:
Slot vented MDF based enclosure, 24" x 22" x 18.45" with a 20hz tuning frequency. Net internal volume is 4 cubic feet (taking into account the driver displacement, etc, maybe a little more for bracing). I originally had a larger cabinet but the driver excursion was getting out of hand. 20hz is chosen to get that high SPL output with minimal excursion from the driver, so that the woofer is only really having to stress around 30~35hz with its excursion (if I modeled it correctly).
I'm modeling with the GRS 18PT-8 18" Pro Driver (8ohm). It's only $70.
Here's the driver excursion relative to xmax:
I applied a few filters to control the driver. A highpass filter at 17hz. A lowpass filter at 200hz, but this could be at 110~120hz, it won't matter much as I will crossover. PEQ +15db at 20hz with Q of 0.75 to boost the near port output without asking the driver to have high excursion while doing it (I think?). PEQ -8db centered on 55hz with Q of 1.4 to smooth out the peak that was there and further drop excursion. The resulting excursion model in this box at the intended signal input is graphed below, so that the driver doesn't exceed xmax until well under port tuning frequency which I will cut off.
For the slot vent, it's 1.0" x 20.74" x 29.74" in this enclosure to produce the 20hz tuning frequency, but also to limit air velocity from the slot at the intended input signal so that it doesn't exceed 18, conventional wisdom being this will eliminate the chuffing sound.
Those models and filters in place, the following is the SPL graph result.
This is where things get sketchy maybe. I'm modeling this based on a 10 foot distance from the driver face to the listening position and an input of only 50 watts at 8 ohms. I know this is nothing outstanding, but for me this is interesting because for just 50 watts, I'm looking at a nice curve to start working with from just one sub and only 50 watts of power that will be very stable to run. The goal will be to build several of these, 4 of them to start. So the idea is that if I'm getting potentially 96db at 20hz and up, when I add the 2nd sub, I could expect to be close to 100db at 20hz, and add two more and get closer to 105db potentially at 20hz, before room gain (sealed room).
I already have a miniDSP HD 2x4 that I use, so I would use that to align the subs and produce the summation virtual sub and then EQ that for a gentle house curve, based on whatever the 20hz performance ends up at.
I already have an AudioSource AMP100 amp that does 50 watts into 8ohms, two channels, with a nice big power supply. These are inexpensive and pretty solid. I could add another for the 2nd pair of subs. I probably could get way cheaper amplifiers for this, but I'm not certain of quality in tiny class D amps around 50 watts into 8ohms out there with good quality output down to 20hz. I'm totally open to suggestions if you have them!
So end result would be 4 of these enclosures, each running at 50 watts max, for a very low total power draw running full tilt at all times if wanted, stable. Again, from the standpoint of 10 feet distance to the subs (they would be in a sealed room 10 feet from the listening position area) in the home theater room.
If this is modeled properly, and will work (I have my doubts, which is why I'm asking!) the break down is:
Driver x 4 at $70 each, so $280
MDF, glue, screws, terminal binding posts, typical wire, x 4 - $200
Amp x 2 at $150 each, $300
About $780 for this project, unpainted. I would probably just black paint it matte or duratex type look, utilitarian.
Do you all think this is plausible?
Are the models ok or is something horribly wrong?
I do realize there are limits here, and that asking this system to do more than its max is not going to go anywhere. I modeled it for its max use and distance in the room for its purpose.
Any input appreciated.
Very best,
Any tips for designing/building low noise preamps ?
- By Ivna
- Analog Line Level
- 48 Replies
I have been working on a diy audio mixer based on ne5532 opamps with auxiliary output/input, panning and baxandall tone control.
Here is the circuit of one of the inputs:
(+-12v supply, 100nF on each Vpin of the opamps) (this "input module" will be duplicated for each chanel I make and all chanels get mixed in other circuit).
I made the PCB and everything worked fine (except the tone pots where inverted whoops
). However the preamp adds to much noise to the signal and makes it pretty unusable for instrument-level inputs.
The noise (hiss) gets amplified when i raise the gain. And gets worse When treble pot is boosted... It also has some hum but i think thats because i havent shielded it yet.
Maybe you, the opamp-gurus, could give me some design tips on how to improve signal/noise ratio on the preamp. Or modifications to improve the rest of the circuit??
Here is the circuit of one of the inputs:
(+-12v supply, 100nF on each Vpin of the opamps) (this "input module" will be duplicated for each chanel I make and all chanels get mixed in other circuit).
I made the PCB and everything worked fine (except the tone pots where inverted whoops
). However the preamp adds to much noise to the signal and makes it pretty unusable for instrument-level inputs.The noise (hiss) gets amplified when i raise the gain. And gets worse When treble pot is boosted... It also has some hum but i think thats because i havent shielded it yet.
Maybe you, the opamp-gurus, could give me some design tips on how to improve signal/noise ratio on the preamp. Or modifications to improve the rest of the circuit??
WARNING: About the DUST!
- By wiseoldtech
- Construction Tips
- 82 Replies
Administrator really should make this thread a "sticky"
My "high-end" neighbor likes to bring me his new found treasures that require servicing.
It's not always a pleasant job of course.
And this one job I'm currently doing is the focus of this thread.
It concerns vintage equipment that has a known, dangerous, and deadly element known as Cadmuim.
It was used in many things as a plating on metal parts, and perhaps you've seen a white or yellowish powder on old equipment.
Chassis, speakers, and other components are all affected.
It MUST be CAREFULLY removed.
Cadmuim is as bad as Asbestos if you breathe it.
A mask, gloves, and eye protection is mandatory.
And it has to be done OUT-doors, carefully.
I won't go into the whole procedure, you can look it up for yourself.
This is a close-up photo of the 1964-ish Thorens TD 124 motor assembly on my bench that was seized-up but serviceable.
It's gonna be a messy job, most of the turntable's parts are also contaminated with the white powder too.
My "high-end" neighbor likes to bring me his new found treasures that require servicing.
It's not always a pleasant job of course.
And this one job I'm currently doing is the focus of this thread.
It concerns vintage equipment that has a known, dangerous, and deadly element known as Cadmuim.
It was used in many things as a plating on metal parts, and perhaps you've seen a white or yellowish powder on old equipment.
Chassis, speakers, and other components are all affected.
It MUST be CAREFULLY removed.
Cadmuim is as bad as Asbestos if you breathe it.
A mask, gloves, and eye protection is mandatory.
And it has to be done OUT-doors, carefully.
I won't go into the whole procedure, you can look it up for yourself.
This is a close-up photo of the 1964-ish Thorens TD 124 motor assembly on my bench that was seized-up but serviceable.
It's gonna be a messy job, most of the turntable's parts are also contaminated with the white powder too.
A Karlson Compendium - Part One - "A New Approach in Loudspeaker Enclosures"
- By freddi
- Full Range
- 32 Replies
Attachments
GM70 SE amp project
- By dave123
- Tubes / Valves
- 52 Replies
Hey guys
Actually two of my friends and I are working on a single ended integrated amplifier so we thought why not to write about it here in order to use group wisdom.
OPT and power transformers are made by a friend whos job is pretty good in building tube amplifiers:
he suggested to use 6n6/6H6 as input tube and two 6E5P Russian tubes do drive one GM70 but without any further details. here are PSU and amplifier schematic I got so far:
I'm not sure about using 6N6/6H6 and 6E5P. I may consider other tubes if I have access to. any idea is much appreciated.
Actually two of my friends and I are working on a single ended integrated amplifier so we thought why not to write about it here in order to use group wisdom.
OPT and power transformers are made by a friend whos job is pretty good in building tube amplifiers:
he suggested to use 6n6/6H6 as input tube and two 6E5P Russian tubes do drive one GM70 but without any further details. here are PSU and amplifier schematic I got so far:
I'm not sure about using 6N6/6H6 and 6E5P. I may consider other tubes if I have access to. any idea is much appreciated.
A little passive crossover design help (GRS woofer & tweeter)
Hi,
I'm learning slowly about how to design and then build passive crossovers and I'm practicing on two drivers I'm interested in potentially building a loud speaker with eventually.
GRS 12PT-8 12" Driver
GRS PT6825-8 8" Planar Mid/Tweeter
I was thinking of using them to build a high sensitivity loud speaker focusing on the 70hz to 20khz range (to then crossover with subs at 80hz or so). I have no modeled the enclosure yet, due to still learning how to even cross these over and as I understand it the enclosure design will be more about the woofer than the tweeter anyways. I'm not sure if I want sealed or ported yet, but I think I may do sealed for this one since I do not need low frequency output below 70hz basically.
I've been learning to use XSim for the crossover circuit and analyzing the graphs. I'm still very new to this. I at least got to the point where I could input the FRD/ZMA data and at least build a simple circuit to show the simulated results in the graph windows. But when it comes to actually producing a nice crossover, I am not there yet.
I'm mostly having trouble with picking a crossover point and then targeting that and then I'm not sure how to target specific places within the graph (such as targeting treble from 8khz to 12khz and dropping only that range a little, etc). I was thinking I wanted to try to crossover somewhere around 1~2khz since this particular planar tweeter has a lot of range and let the woofer pound out the rest down to 70hz. It looks like from the info that maybe 2khz would be ok. But I can't get it to line up for the of life me yet, knowing I know little at the moment.
I'm attaching the FRD/ZMA information on these two drivers to this post if anyone is willing to look at it.
Edit: I attached my XSim project file to simplify things now that I know that can make it easier.
And I'll post my disaster of a design thus far. Again, just trying to understand what I'm doing and what everything does.
I'm trying to just get a fairly flat response from 70hz to 20khz, I'm ok with some things being higher than flat as they can be EQ down with room correction. Any suggestions or help appreciated. I already know that 47uF cap is just pointless, I was just adjusting value to see how the graph would respond. After looking at parts, I realize I do not want to fool with expensive caps.
Thanks!
Very best,
I'm learning slowly about how to design and then build passive crossovers and I'm practicing on two drivers I'm interested in potentially building a loud speaker with eventually.
GRS 12PT-8 12" Driver
GRS PT6825-8 8" Planar Mid/Tweeter
I was thinking of using them to build a high sensitivity loud speaker focusing on the 70hz to 20khz range (to then crossover with subs at 80hz or so). I have no modeled the enclosure yet, due to still learning how to even cross these over and as I understand it the enclosure design will be more about the woofer than the tweeter anyways. I'm not sure if I want sealed or ported yet, but I think I may do sealed for this one since I do not need low frequency output below 70hz basically.
I've been learning to use XSim for the crossover circuit and analyzing the graphs. I'm still very new to this. I at least got to the point where I could input the FRD/ZMA data and at least build a simple circuit to show the simulated results in the graph windows. But when it comes to actually producing a nice crossover, I am not there yet.
I'm mostly having trouble with picking a crossover point and then targeting that and then I'm not sure how to target specific places within the graph (such as targeting treble from 8khz to 12khz and dropping only that range a little, etc). I was thinking I wanted to try to crossover somewhere around 1~2khz since this particular planar tweeter has a lot of range and let the woofer pound out the rest down to 70hz. It looks like from the info that maybe 2khz would be ok. But I can't get it to line up for the of life me yet, knowing I know little at the moment.
I'm attaching the FRD/ZMA information on these two drivers to this post if anyone is willing to look at it.
Edit: I attached my XSim project file to simplify things now that I know that can make it easier.
And I'll post my disaster of a design thus far. Again, just trying to understand what I'm doing and what everything does.
I'm trying to just get a fairly flat response from 70hz to 20khz, I'm ok with some things being higher than flat as they can be EQ down with room correction. Any suggestions or help appreciated. I already know that 47uF cap is just pointless, I was just adjusting value to see how the graph would respond. After looking at parts, I realize I do not want to fool with expensive caps.
Thanks!
Very best,
Would these Focals be worth trying in an open baffle DIY?
- By omnivor
- Full Range
- 11 Replies
Attachments
Audible Illusions M3A and excessive hiss
- By mahalomac
- Tubes / Valves
- 18 Replies
Hello,
i have a preowned AI 3 convertetd with a M3A board and John Curl Boards. I like this Amps and the MC pre sound delicious. I bought it 1.5 years ago with a quad set of
6H23p tubes. As they become "hissy" (sounds like the wind blows through your speaker), i have changed them to a new quad EH6922 (gain switch is low).
After 25 hours of listening in 3 months I got the hissy stormy sound again in the left speaker. I unscrewed the topplate, the sound was good for 30 minutes, than the hiss (or like waves - volume is changing) on the left speaker was back.
Questions:
- If the tube will get burned out by the AI...will the hiss be permanent?
- 6922 EH not so stable as 6H23p?
- What is better for the tubes - switch to high or low gain?
- Should i replace the electrolytic caps?
- Is there a way to change the filament or anything to stop valve eating? (I read it in another thread but I would need a part list an exact guided way what to change from somebody who had done it)
Thanks for feedback.
Marcus
i have a preowned AI 3 convertetd with a M3A board and John Curl Boards. I like this Amps and the MC pre sound delicious. I bought it 1.5 years ago with a quad set of
6H23p tubes. As they become "hissy" (sounds like the wind blows through your speaker), i have changed them to a new quad EH6922 (gain switch is low).
After 25 hours of listening in 3 months I got the hissy stormy sound again in the left speaker. I unscrewed the topplate, the sound was good for 30 minutes, than the hiss (or like waves - volume is changing) on the left speaker was back.
Questions:
- If the tube will get burned out by the AI...will the hiss be permanent?
- 6922 EH not so stable as 6H23p?
- What is better for the tubes - switch to high or low gain?
- Should i replace the electrolytic caps?
- Is there a way to change the filament or anything to stop valve eating? (I read it in another thread but I would need a part list an exact guided way what to change from somebody who had done it)
Thanks for feedback.
Marcus
SL1210 plinth adventure
- By peppennino
- Analogue Source
- 54 Replies
Hi All,
My friend Mauro (mauro2098) and I, after Jim's mods on PSU, decided, inspired by Ken's superb work, to follow his path.
We started buying a cheap SL1200 top plate chassis:
Next step, filling the holes and make all borders square with alu-like epoxy plaster:
And finishing with epoxy car plaster:
Mauro has done a very nice work 🙂
Time to choose the veneer:
Mahogany, walnut or ash burl?
My friend Mauro (mauro2098) and I, after Jim's mods on PSU, decided, inspired by Ken's superb work, to follow his path.
We started buying a cheap SL1200 top plate chassis:
Next step, filling the holes and make all borders square with alu-like epoxy plaster:
And finishing with epoxy car plaster:
Mauro has done a very nice work 🙂
Time to choose the veneer:
Mahogany, walnut or ash burl?
10 watt class AB valve amplifier.
- Swap Meet
- 1 Replies
Valve amplifier 10 watt. Uses PSU transformers but sounds fine.
12AX7 front end and pair EL84 push pull drivers.
Yes, I messed up with too small a transformer and bigger one is glued to pcb.
Open to offers. £15 postage and packing. UK only.
12AX7 front end and pair EL84 push pull drivers.
Yes, I messed up with too small a transformer and bigger one is glued to pcb.
Open to offers. £15 postage and packing. UK only.