3.5" would be ideal (same distance as the TV from the wall), 5.5" or thereabout would be acceptable
@ddlooping My guess is that you would get best results by splitting it into 4-5 plates with an exciter on each. 8" might be a bit narrow in shortest dimension regardless.
Spedge, the idea was to build a b&o beoplay a9. So the size of the stereo DML would be 70 cm/ 27 inch. with a compact TL-woofer (duo voicecoil) on the backside. Additionally maybe some tweeters on the side to support the highest frequencies.
I'm assuming 90dB sensitivity (given 2Vrms @1khz into approx 3.5Re per driver)
I've added sketches for clarity where necessary. Loads highlighted in red are not a good idea. Numbers are as follows:
- 2 units only in parallel = 94.6dBSPL, 1.6r load, 2 x 25W = 50W nominal power handling.
- 3 units in parallel = 97.6dBSPL, 1.1r load, 3 x 25wW = 75W nominal power handling.
- 4 units in series-parallel = 93.8dBSPL, 3.5r load, 4 x 25W = 100W power handling.
- 2 string of 3 units in SERIES, = 93.5dBSPL, 5.4r load, 6 x 25W = 150W power handling
- 3 strings of 2 units in series = 97.1dBSPL, 2.4r load, 6 x 25W = 150W power handling
The most efficient is obviously the last one which delivers 97dB/W and can handle 150W
The "power handling" tell you what size amp you would use IF you were driving pure sine-waves into whatever load your configuration presents. But a music signal, driven at maximum output power, will only deliver about half that wattage into the driver. Therefore, you can safely double the size of the amplifiers AS LONG AS YOU DO NOT CLIP THEM.
Does this help?
ddlooping.
On pages 179 to 180 I made some recordings of my very old and cheap surround sound setup in my front room , but replaced the normal little speakers with small card panels.
For some reason, I noticed the speed of the blade runner is a little fast ?
But big Ben sounds OK.
To give you an idea of what to expect.
Use headphones to listen, no download needed on these recordings.
Steve.
On pages 179 to 180 I made some recordings of my very old and cheap surround sound setup in my front room , but replaced the normal little speakers with small card panels.
For some reason, I noticed the speed of the blade runner is a little fast ?
But big Ben sounds OK.
To give you an idea of what to expect.
Use headphones to listen, no download needed on these recordings.
Steve.
On page 304 post #6073 I explain how I made my center channel DML's to go along with my right and left DML's. The 2 centers are 8" x 14", over-under TV. The thin stretchy material I used to cover them to quell the highs a bit could be of any color or design of your choice. I made two short ones instead of one long because it just worked out best for mounting in my situation and it allowed me to wire my two 4ohm into a single 8ohm. I always wanted to try that over-under configuration anyway. Working great so far, voices sound very clear.Hi all
This has probably been asked before but I couldn't find an answer:
- Could a long and narrow DML be used as a center speaker, placed horizontally under a 65" TV?
Edit : ... with a subwoofer
On this post by unaHm he talks about his experience with the distance from the wall , while using the canvas panels.Well, this is another project that I've finally been able to get around to!
So this became a fun family project, where my daughter offered to paint the canvases with acrylic paint. We sealed it with Gesso, and then she went to work with her designs.
I noted in the thread that 'drum tight' was ideal, so I jammed sticks in between the frame and the canvas, and made sure that both were 'tuned' the same.
I also noted that they sounded best, I think, 6-7 inches from the wall. Initially, I had them mounting on picture hooks, and as one can imagine they sounded a bit strange, so fortunately for me my wife let me get a pair of 6"x8" shelf brackets that I could hang them from. In this case, 6" still wasn't right, but flipping the bracket to allow the speaker to hang 8" from the wall gave the best response.
They're perfect for a living room. Great voice intelligibility, and Bass that makes you think there's a sub tucked away somewhere. I'm using one of the Lepai LP2020A (if I remember correctly) amplifiers, so there's nothing special driving them. I'd highly recommend these for a listening room, and the WAF is very high...to the point that, dare I say, my wife was excited!
The only place in the build I used silicone was for mounting the wooden disc to the centre of the canvas. I'd been working on another speaker project, and so had a hot glue gun to hand. I used two layers of craft sticks on the back to brace the exciter, and added a little semi-triangular brace between them and the frame.
This can be a good full range panel if mounted and designed properly.
Steve.
This and the previous post shows a picture of my small panels in action on vocals.
They have a very clean and rich sound.
This is a joy to listen to.
Steve.
This is also a very good sounding recording, even though I am walking around the room.
Steve.
I made a very loud torture track to show how loud the small panels could go without sounding stressed.last tom waits
xrk971.
on the first recording ,take it with me ,i had to lower the volume of the veneer panel as the piano was setting off the problems with splitting and cracking surfaces .
but then i noticed that something else was also distorting , the low frequency from the TLS was causing at least 2 items in the room to start buzzing (still not located ).
so ive had to lower the TLS which only run below 300hz,so his voice does not sound as deep(would you believe )as it would, which i think is much nicer and gives more warmth and closeness ?
the second recording, filipino box spring hog,i recorded to show that i wasnt just playing soft music , because the panel could not handle it.
i had one finger in one ear and turned my head to one side when playing this, and i was well back in the room, as it was quite painfully loud
obviously you do not have to listen to it this loud
sorry they are in the wrong order, i had to change ,take it with me , to 128 , as it was too large, even though at my end it said it was not ?
steve.
Steve.
Late last night I suddenly decided to make up a thin sheet aluminium panel ,it is approx 10x13inches and less than 1cm thick.
I glued 2 sheets together with Evo-stik as the spray mount had gone off over the years .
The Evo-stik was getting pretty old as well and was not as thin as it used to be.
But it did the job.
I used it to glue on the exciter too, as I was in a hurry, it was getting late.
Pic 1 is the panel.
Pic 2 is the response at 3m.
Pic 3 is with the TLs xo at 220hz.
Pic 4 is the panel at 1m.
The panels will be xo at 90hz as this exciter has problems with rubbing coils.
You could get away with a 160hz sub roll off, I think.
In my room anyway.
Steve.
I glued 2 sheets together with Evo-stik as the spray mount had gone off over the years .
The Evo-stik was getting pretty old as well and was not as thin as it used to be.
But it did the job.
I used it to glue on the exciter too, as I was in a hurry, it was getting late.
Pic 1 is the panel.
Pic 2 is the response at 3m.
Pic 3 is with the TLs xo at 220hz.
Pic 4 is the panel at 1m.
The panels will be xo at 90hz as this exciter has problems with rubbing coils.
You could get away with a 160hz sub roll off, I think.
In my room anyway.
Steve.
Attachments
The response is not as smooth as the large sheet I used to have , but I guess there is more dml action going on on this smaller panel ?
I will hopefully get time later on to make a recording.
At the moment I have this panel running next to the graphite eps, with the eps turned down 15db on my digital xo to match the sound output.
Steve.
I will hopefully get time later on to make a recording.
At the moment I have this panel running next to the graphite eps, with the eps turned down 15db on my digital xo to match the sound output.
Steve.
Hello Drkmatr,
Are you refering to post 6394 ?
I like spectrogram that are based on wavelet. The delays are quite easily visible and the need of damping also. I am not used to extract group delay. If you think it has an interest, it might be possible to extract it from different measurements made with REW.
I don't think DML speakers have much issue with group delay. There are no ports with alternative paths for different frequencies and less crossovers.
However, when analysing responses, DML does have an issue with decay times, which is not surprising due to the modal aspect. A highly dampened material would give a more accurate impulse response with reduced decay, but hardly no sound.
So I would disagree that the goal is to get the panel to return to zero as quickly as possible. If DML could be made to have an accurate impulse response it would sound like a regular speaker.
With regular speakers any modes or time domain smearing are issues one would like to cure, but with DML it is features of how the speakers works, and something to control instead of avoid.
However, when analysing responses, DML does have an issue with decay times, which is not surprising due to the modal aspect. A highly dampened material would give a more accurate impulse response with reduced decay, but hardly no sound.
So I would disagree that the goal is to get the panel to return to zero as quickly as possible. If DML could be made to have an accurate impulse response it would sound like a regular speaker.
With regular speakers any modes or time domain smearing are issues one would like to cure, but with DML it is features of how the speakers works, and something to control instead of avoid.