Since I got some useful information from this forum, I also would like to contribute something here ... only a small speaker 
.
I come from Germany and so my english is not perfect!
First some background.
I was not so happy with the center speaker of my home cinema system, a Canton CD50 II.
The main problem ist not the Canton itself, but in my eyes it did not harmonize with my front speakers ("old - DIY" Dynaudio Sirius).
A center with the same drivers is not possible as Dynaudio do not sell drivers anymore. Furthermore I want a "small" center.
First I thought about a construction like the Canton, but in simulations it is clear that it is not a good idea to put so many drivers in a horizontal line - for a center!
So I thoght about a fullrange driver - ok these drivers have also some limitations - but I always wanted to build a speaker with a fullrange, why not a center.
So I searched about fullrange speakers and came across MarkAudio an this forum.
From the datasheet the CHR-70 (gen.3) seems to do quite well in a small enclosure and it is quite cheap so it is not fatal if I won't get it work like I want.
I put the driver data in BoxSim an simulate a bit. I end with a 7l / 59Hz bass-reflex enclosure.
These would fit in my shelves also, so maybe I will build 2 more as front speakers!? As I want a thin box I use "only" 12mm birch plywood and put some bracings in. This should enough for such a small enclosure. A part of the enclosure is a sandwich with sloped inside against standing waves. I am not a cabinet maker and with this method the outside is an "easy" rectangle and inside no one would see "the flub"
The outside is not finished but a first hear impression is really good. I put 0,39mH || 3,9Ohm in as it sounds very bright. But it should play same time before a final decision.
Here are 3 early pictures and planing piktures with Sketchup.
. I come from Germany and so my english is not perfect!
First some background.
I was not so happy with the center speaker of my home cinema system, a Canton CD50 II.
The main problem ist not the Canton itself, but in my eyes it did not harmonize with my front speakers ("old - DIY" Dynaudio Sirius).
A center with the same drivers is not possible as Dynaudio do not sell drivers anymore. Furthermore I want a "small" center.
First I thought about a construction like the Canton, but in simulations it is clear that it is not a good idea to put so many drivers in a horizontal line - for a center!
So I thoght about a fullrange driver - ok these drivers have also some limitations - but I always wanted to build a speaker with a fullrange, why not a center.
So I searched about fullrange speakers and came across MarkAudio an this forum.
From the datasheet the CHR-70 (gen.3) seems to do quite well in a small enclosure and it is quite cheap so it is not fatal if I won't get it work like I want
.I put the driver data in BoxSim an simulate a bit. I end with a 7l / 59Hz bass-reflex enclosure.
These would fit in my shelves also, so maybe I will build 2 more as front speakers!? As I want a thin box I use "only" 12mm birch plywood and put some bracings in. This should enough for such a small enclosure. A part of the enclosure is a sandwich with sloped inside against standing waves. I am not a cabinet maker and with this method the outside is an "easy" rectangle and inside no one would see "the flub"
The outside is not finished but a first hear impression is really good. I put 0,39mH || 3,9Ohm in as it sounds very bright. But it should play same time before a final decision.
Here are 3 early pictures and planing piktures with Sketchup.
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Hi Andy, (Guys)
Many thanks for posting your project. Its very interesting and looks very nice. Could you post the build dimensions? If you'd like to send me a dimensional drawing, I'm happy to put your plan on the new Markaudio site:
Plans | Markaudio
Looking at the pics and your text, this box design has an internal volume of around 7 litres. As a guide, box volumes from 8 to 10 litres offer closer optimisation for the Gen.3 CHR (subject to power-handling needs). There's a plate mounted from the front baffle, close to the underside of the driver (see arrow on pic). Markaudio drivers generate a large backwave (relative to cone size), so its sometimes better to avoid having this internal box feature so close to the driver. These 2 design elements could increase internal compression on the rear of the driver's power-train. Some losses in the bass output are likely. This is normal for smaller BR and vented boxes. Using an inductor in series may help to reduce the "bright" sound.
Adding bracing on box projects using under 18-mm thick walls is a good idea.
You could also experiment by adding some loose low density damping material (see pic).
Cheers
Mark.
Many thanks for posting your project. Its very interesting and looks very nice. Could you post the build dimensions? If you'd like to send me a dimensional drawing, I'm happy to put your plan on the new Markaudio site:
Plans | Markaudio
Looking at the pics and your text, this box design has an internal volume of around 7 litres. As a guide, box volumes from 8 to 10 litres offer closer optimisation for the Gen.3 CHR (subject to power-handling needs). There's a plate mounted from the front baffle, close to the underside of the driver (see arrow on pic). Markaudio drivers generate a large backwave (relative to cone size), so its sometimes better to avoid having this internal box feature so close to the driver. These 2 design elements could increase internal compression on the rear of the driver's power-train. Some losses in the bass output are likely. This is normal for smaller BR and vented boxes. Using an inductor in series may help to reduce the "bright" sound.
Adding bracing on box projects using under 18-mm thick walls is a good idea.
You could also experiment by adding some loose low density damping material (see pic).
Cheers
Mark.
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I'm a big bracing advocate, but one does need to consider the build material... 12mm BB is approx as stiff as 20mm MDF so they would require similar bracing on that basis, higher mass with MDF means even more bracing required to push panel resonances up to where they become innocuous,
dave
Many Thanks!
If I find some time I will create a (good) dimensional drawing and send it to you.
First a quick dimensional Sketchup export. The hollow space of the sandwich part is filled with quarz sand.
I put this plate at the same distance than the top and side walls so that the "pressure" to the driver should be consistent!?
I know the driver is (to?) close to the walls but I want a thin Box to put it in my TV Rack. The front wall around the driver is beveled.
With the 0,39mH || 0,39Ohm in series it seems quite good, the "bright" sound was without any part in it.
As I cover the Box with wood stain and wax the next listinig has to wait a bit.
Of course I put some damping material (Sonofil) inside
Andreas
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Hello Andreas,
Great, put your name on it and email me as a PDF if possible: support@markaudio.com
Cheers
Mark.
As there is some discussion about power handling
http://www.diyaudio.com/forums/markaudio/193247-alpairs-arent-woofers.html
some notes to my box. Even if this is a small Box, it is a bass-reflex!
So frequencies around fs and < fb are critical.
I attach a simulation from BoxSim.
With damping (red line vs black) the fs can be controlled.
To be safe, frequencies under fb shoud be controlled by a filter.
With a simple 1 order passive filters you may not get the desired effect.
Either the filter frequency is to high or the effect is to low. (50Hz - blue line).
As I use it as a center (or front) with an AV receiver (aktiv filter) a 3. order even at 40Hz should be ok (green line).
http://www.diyaudio.com/forums/markaudio/193247-alpairs-arent-woofers.html
some notes to my box. Even if this is a small Box, it is a bass-reflex!
So frequencies around fs and < fb are critical.
I attach a simulation from BoxSim.
With damping (red line vs black) the fs can be controlled.
To be safe, frequencies under fb shoud be controlled by a filter.
With a simple 1 order passive filters you may not get the desired effect.
Either the filter frequency is to high or the effect is to low. (50Hz - blue line).
As I use it as a center (or front) with an AV receiver (aktiv filter) a 3. order even at 40Hz should be ok (green line).
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Hello Andreas, Guys,
If you have a filter design, would be useful to post your idea.
Re filters in general. Much depends on each individual Diyer, his/her needs, preferences and system operation. Personally, I err on the side of purist so rarely apply filtering, taking care when running drivers. All said, I appreciate that for others, protective filtering might a sensible practical option.
Cheers
Mark.
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For Hifi(Stereo) Music I personally don't like filters either.
My stereo amplifier has only a volume control.
As center or front at the home cinema system the AV-receiver calibrate
the room and uses DSP so here I have no problem to use the digital filter
of the receiver. BluRays uses heavy dynamics with very low frequecies so
here I like to be save for the speaker.
I have no expert knowledge in filter design!!!
If someone really want a passiv filter I tried a simulation with BoxSim.
As the filter is seeing the "whole box" (to my knowledge) a impedance correction is needed.
To use "standard" devices I get a 2. order filter at ~43Hz.
My stereo amplifier has only a volume control.
As center or front at the home cinema system the AV-receiver calibrate
the room and uses DSP so here I have no problem to use the digital filter
of the receiver. BluRays uses heavy dynamics with very low frequecies so
here I like to be save for the speaker.
I have no expert knowledge in filter design!!!
If someone really want a passiv filter I tried a simulation with BoxSim.
As the filter is seeing the "whole box" (to my knowledge) a impedance correction is needed.
To use "standard" devices I get a 2. order filter at ~43Hz.
Attachments
Yes, for such a low frequency (40Hz) you need these values.
Of course no air-coils. I do not know US shops and parts.
Here are e.g. Mundorf coils quite commen.
http://www.mundorf.com/english 1.1/spulen-kern.htm
FERRIT-core coils > 10mH are about €10.
Of course no air-coils. I do not know US shops and parts.
Here are e.g. Mundorf coils quite commen.
http://www.mundorf.com/english 1.1/spulen-kern.htm
FERRIT-core coils > 10mH are about €10.
Hi Andreas, Guys,
Many thanks to Andreas for making the time to design this filter.
Looking at the values on Andreas's drawing, the pricing for this filter component set will be mighty expensive. I checked the Erse site and a 15mH solid core is US$35 (US$50 with the shipping - see screen pic). 2 of these would be needed to get close to one of the values on Andreas's drawing. Add in the cost of the other filter components, the project costs shoot through the roof.
Being a purist, I've not put much time into filter design (busy working on drivers), so other members will likely have more experience.
I get nervous when seeing so many components on a filter. Markaudio driver cones are very micro-resonant sensitive. What filters of this size and type do the input signal............ummmmmmmph. Having listened to several multi-way systems recently, I personally remain planted in the "minimalist" audio camp. But I also appreciate for others, designing and making filters is an interesting part of the hobby.
Cheers
Mark.
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Hi Einric,
Not recommended. I guess you're looking at the "sub-sonic" part of the device, but there's no advantage that I can see in using this device as signal boost is not the challenge in this case. I'm very weary of devices such as this one. They are rarely get close to being "audiophile" grade.
Thx
Mark.
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If someone is unsure about the values, at
2-Way Crossover Designer / Calculator
Crossover Design Chart and Inductance vs. Frequency Calculator(Low-pass)
you can calculate a 2nd order Butterworth around 40Hz.
(Here you need the Highpass!)
It is clear that a passiv filter is not good choice
I think the only solution, if someone really wants a filter, is an activ filter in front of the power amplifier.
I think some information can be found at the "Digital Line Level" part at this forum?
2-Way Crossover Designer / Calculator
Crossover Design Chart and Inductance vs. Frequency Calculator(Low-pass)
you can calculate a 2nd order Butterworth around 40Hz.
(Here you need the Highpass!)
It is clear that a passiv filter is not good choice
I think the only solution, if someone really wants a filter, is an activ filter in front of the power amplifier.
I think some information can be found at the "Digital Line Level" part at this forum?
also note this appears to be an automotive system black box - (the inline fuse holder kinda gives it away) - this is an environment in which for the vast majority of listeners the deleterious effects such gadgets might bring to the table are likely swamped by the environment
I mean, I've heard some wonderful sounding "car audio" when the vehicle's standing still - but unless it's a Rolls Royce or other such mobile cocoon, once underway, the finer subtleties can be buried under a noise floor that can easily exceed 70dB SPL.
So, after >50 hours operating I think could say a few words
First, as you can see, I'm not a professional cabinet maker
Talking about the sound quality is a bit difficult, as, till now, I only used it as center, and I have only one speaker.
As center it really fulfill (beats) my expectation, the voices are "clear" and "full" !!!
It seems that the sounds get more "potent" "stronger" (don't know the right english word) the longer it operates. Maybe I can reduce the resistance of the filter a bit!? But I will wait some hours of operation.
When I have some time I will put it at the Hifi amplifier ... but with one speaker I don't think that I have a lot to say.
First, as you can see, I'm not a professional cabinet maker
Talking about the sound quality is a bit difficult, as, till now, I only used it as center, and I have only one speaker.
As center it really fulfill (beats) my expectation, the voices are "clear" and "full" !!!
It seems that the sounds get more "potent" "stronger" (don't know the right english word) the longer it operates. Maybe I can reduce the resistance of the filter a bit!? But I will wait some hours of operation.
When I have some time I will put it at the Hifi amplifier ... but with one speaker I don't think that I have a lot to say.
Attachments
Yesterday I had some time and so I test the speaker with music.
First, I think its nothing complete wrong with the speaker (Well I have no measurment equipment)
I test with all kind of music, even ACDC
With "small" sounds - few instruments/vocals - I find it really great!
With "complex" sound I find it a bit to "cold/thin ?!?"
I think the 200-500Hz is a bit to gentle - or around 1000Hz a bit to much - I have to test it.
The bass is really "incredible" for the small chassis/enclosure.
Ok no deep bass of course (with 59Hz reflex) but there is a clear fine bass!
Mids and highs sound really good, especially the highs are "airy".
(didn't thought that FRs are so good at the highs! And as I read, the Alpairs shoud be better)
With total cost less than €70 (incl. wood, filter components, ...) I am really satisfied with the result!!!
If I find time (and money) I will build a pair of FR speakers.
First, I think its nothing complete wrong with the speaker
(Well I have no measurment equipment)I test with all kind of music, even ACDC
With "small" sounds - few instruments/vocals - I find it really great!
With "complex" sound I find it a bit to "cold/thin ?!?"
I think the 200-500Hz is a bit to gentle - or around 1000Hz a bit to much - I have to test it.
The bass is really "incredible" for the small chassis/enclosure.
Ok no deep bass of course (with 59Hz reflex) but there is a clear fine bass!
Mids and highs sound really good, especially the highs are "airy".
(didn't thought that FRs are so good at the highs! And as I read, the Alpairs shoud be better)
With total cost less than €70 (incl. wood, filter components, ...) I am really satisfied with the result!!!
If I find time (and money) I will build a pair of FR speakers.
Spec,
Arbitrarily lower port tuning for a certain design doesn't usually yield the best results - it can very well result in a spikes in the overall frequency response. Playing around with WinISD I've noticed that if I lower the tuning frequency, usually there is a dip in the 80-200 Hz area, which is not ideal, especially if you are listening to rock/metal. You can maybe do a correction via DSP, but that can sometimes lead to more cone excursion and distortion.
There's a bigger box called the "Half Towers" which is tuned to the mid 40s IIRC:
http://homepage.mac.com/tlinespeakers/FAL/downloads/microTower-maps-150909.pdf
There is a folded version of the half tower that is shorter in height - you can probably find that under "CHR-70 Application Thread" in the forum.
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