The last paragraph on p.30 says the best suspension is an elastic one uniformly distributed along the perimeter. This matches the foam used above and seems to indicate damping of edge resonances is important.
The thesis uses paper faced foam core panels - same as I used orginally on post 1.
That stuff is very light but is reasonable stiff and has built in damping.
The poplar panels are now installed and up and running. Each panel is currently secured using four 'clamps' with draft proofing damping between the clamp and the panels and frame. The plan is now to add the foam suspension and then ease off on the clamp pressure.
Sensitivity is an excellent match with the Monacor 15 inch bass driver in a U frame. Currently, all I've done on the EQ front is a 4db cut in the 'honk' region centred on 700hz, plus a bit of bass cut to compensate for the bass 'hump' from the U frame.
The bottom line is that it's very listenable to before even getting down to measuring with the measurement mic. In fact, given that I'm listening to music over and above doing some measurements suggests that it's not far away at all. It's also better to listen to than the previous OB mid/tweeter arrangement.
Sensitivity is an excellent match with the Monacor 15 inch bass driver in a U frame. Currently, all I've done on the EQ front is a 4db cut in the 'honk' region centred on 700hz, plus a bit of bass cut to compensate for the bass 'hump' from the U frame.
The bottom line is that it's very listenable to before even getting down to measuring with the measurement mic. In fact, given that I'm listening to music over and above doing some measurements suggests that it's not far away at all. It's also better to listen to than the previous OB mid/tweeter arrangement.
E.g. If a tweeter is on the right on one side, it would be on the left on the other. I think.
For a DML I think the principle of mirroring is redundant as in principle the distribution of high frequency signals covers the entire surface of the panel. Perhaps there are some differences between this design and the NXT derived approach. It fascinates me that there are so many different ways this technology is being developed with good results. It suggests the basic mode of operation is very robust and amenable to tweaking.
I use suspended ply panels crossed over to subwoofers and get a fantastic performance that betters the ESL I built and have listened to for years.
I use suspended ply panels crossed over to subwoofers and get a fantastic performance that betters the ESL I built and have listened to for years.
OH ok my bad lol...That's how they were made. I don't think it matters that much as there are conventional cone speakers that are mirrored.
I don't know exactly what the brown stuff on the front of the panel but my guess is its some type of paint.
I like how this looks covered with a grille - although it looks more like a conventional speaker now.
Looks like a custom molded ribbed EPS foam is the main resonator panel. is the corner tweeter an isolated small panel of just another driver attached to corner?
Looks like the front radiator is covered with open cell foam?
I think the brown foam may actually be the both the suspension and damping material for the EPS panel, given the corrugated dovetail edges.
So open cell foam bonded to the EPS radiator panel on the face, but attached to the frame at the edges to "float" the EPS panel in 3d space.
Yup, they are basically floor standers.
Its just another driver attached to the corner as the custom mold is one whole unit.
I don't think its open cell foam. It looks and feels more like paint and I am not talking bout the one in the picture but the one I own. Only the front of the panel is painted but the edges and the back of the panel are not.
Can I just say that all the attempts to arrange the positioning of DML’s in a similar arrangement to conventional speakers is missing out the point of how these speakers propagate sound into a room. They do need to by away from a wall and have the separation necessary for stereo, but other than that feel free to experiment.
Ceiling tiles are very dead when knocked and therefore have few problematic resonances to deal with so do not need soft frame fixing at the edges, at least in my limited experience so far. The joy of hanging them, as mine are, gives one the chance to walk around the tiles whilst playing. Walk up to them, between them and then behind them to see how little the sound changes. It’s fascinating and a revelation when compared to conventional speakers
Ceiling tiles are very dead when knocked and therefore have few problematic resonances to deal with so do not need soft frame fixing at the edges, at least in my limited experience so far. The joy of hanging them, as mine are, gives one the chance to walk around the tiles whilst playing. Walk up to them, between them and then behind them to see how little the sound changes. It’s fascinating and a revelation when compared to conventional speakers
Using a frame to reduce resonance is just one aspect of many in what a frame and spine can actually do. The pros out weigh the cons. (if there are any cons)
Frame and spine is also used to prevent voice coil sag as it supports the panel material as well as the exciters weight just like a conventional cone driver. Its also used to give the exciter something to push off of so 100% of all its energy is transferred to the panel. A frame can also act as a wave guide. A frame can be used as floor standers like other conventional cone loudspeakers. With a frame you can put grills on for better asthetics.
If you feel that being able to walk around the speakers while playing out weigh what I said above about using a frame and spine then by all means do so as it is all personal preference.
I would agree with this Jerro. I have two versions of the hanging approach one set with a lot of space behind the panels and the soundstage is epic. Another set are close to a wall but using absorbent material on the rear of each panel ( 1 layer of cabinet stuffing ) which seems to cure an early reflection problem I experienced with these panels. The soundstage is not as deep as the first set but sill very acceptable. I have not felt the need to apply damping but might try it to see if I can hear an improvement. Will let you all know if I do.
Now I have improved on my panels with this simple technique. Although I have had this idea in the back of my mind for a while I did not have the funds to implement and test it out until yesterday. This technique is inspired by the Yamaha NS 20/30 loudspeakers as well as Open Baffle subs. This technique only works if you are using a frame.
Up until yesterday I thought that a 4inch width frame was all that was needed to increase bass but I was wrong. The wider the frame the more it focuses the bass. This is the reason why certain open baffle subs use 12inch or wider frames and why the Yamaha speakers use a deep cabinet. Without the use of wider frames the bass escapes to the sides of the frame instead of being focused straight out. The wider frames focus bass energy like a wave guide so that it does not escape from the sides therefore it sounds more pronounced. I am always experimenting so I am always learning something new to improve on my panels.
Now I will have to rebuild my panels using wider frames in which it cost more money but I will have much more desirable bass response from my panels.
Up until yesterday I thought that a 4inch width frame was all that was needed to increase bass but I was wrong. The wider the frame the more it focuses the bass. This is the reason why certain open baffle subs use 12inch or wider frames and why the Yamaha speakers use a deep cabinet. Without the use of wider frames the bass escapes to the sides of the frame instead of being focused straight out. The wider frames focus bass energy like a wave guide so that it does not escape from the sides therefore it sounds more pronounced. I am always experimenting so I am always learning something new to improve on my panels.
Now I will have to rebuild my panels using wider frames in which it cost more money but I will have much more desirable bass response from my panels.
My comments are totally in reference to using ceiling tiles as I have not tried anything else except for some hardboard, which was totally inferior to the tiles. I’m sure that other materials that exhibit any degree of resonances will need edge damping. A frame acting as a wave guide though? You do not want to ‘guide’ the sound from a DML. I do agree with anchoring the exciter to promote complete energy transfer to whatever material you are using, however I’ve not found an issue so far but will try this soon. I first need to try a second exciter in the same position but on the reverse side, as mentioned previously, to act as an equal but opposite inertial mass for the tile to move between.
Please tell me why you do not want to guide the sound from the DML? What are the legit reasons or cons? Ive told you a fact about using frames as wave guides makes the bass sound more prominent. This technique is used in open baffle subs as well as Yamaha's NS 20/30 loudspeakers. Its tested tried and true. I take techniques from things that actually are tested and PROVEN to work instead of techniques that lead nowhere which is why I cant fathom how people blindly follow tech ingredients advice to hang panels from strings like he is the guru of DML technology. Maybe because he is a physics professor with a degree? I don't get it. I give out facts like voice coil sag and the exciter needing something to push off of and people still want to hang panels because tech ingredients said so without any legit reasoning or proof to back it up. LOL If one does not have the BASIC FOUNDATIONS to begin with your whole design will crumble and or you are satisfied with mediocre sound quality.
I am trying to steer you guys in the right direction. If I didn't care I wouldn't give out any advice and tell yawl to follow Tech Ingredients design to a T. LOL
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Nobody is ignoring you DMLBES. You helped me learn a lot. I suspended mine first time round because it was quick and cheap. I might well try frames and spines a bit later given time and money. In the meantime I for one are just reporting what I find as I go.
Bare in mind my panels are large and I cross over to subs. I am not trying for bass from my panels so I cross over at 100hz.
Bare in mind my panels are large and I cross over to subs. I am not trying for bass from my panels so I cross over at 100hz.
That reply was specifically towards Jerry as he specifically questioned my (in which its not really my technique) wave guide technique in which he stated that you do not want to guide the sound from a DML.
I mean to make such a adamant statement like that there must be a legit logical reason behind it with some actual testing right? I want to know his reasoning with actual testing examples of why you do not want to guide the sound from a DML panel even though that method has been tried and proven (by the use of open baffle subs and Yamaha ns20/30 speakers) to work by improving bass response in which I tested it myself yesterday to further prove the authenticity of that technique.
Listen to these Yamaha ns-20 speakers and tell me if your panels bass sound similar like these Yamaha speakers. The Yamaha cabinet seems to be at least 12inches deep with some type of DAMPING around the inner cabinet. Once I utilized wider panels the bass response increased. Not as loud as these Yamahas because there bass transducer is huge compared to most exciters BUT it did make a vast improvement on bass response. Hence why I know it works. YouTube
This is one of the papers I read before making my MAPs. It reassured me MAPs work so I went ahead and ordered the actuators. I'm not sure if panel geometry is as important anymore with inexpensive DSP, the paper was written in 2008.
The author also used a fairly homogeneous panel. If you use a panel material that isn't homogeneous you might not need edge damping.
On the other hand, there's nothing wrong with building the panels the way he describes. At least you'll know they'll work when you finish them.
Similar to my approach with panel plus bass unit. In my case, I use a 15 inch Monacor SP-382PA bass driver in a U frame. I also use a miniDSP for crossover and DSP duties, so can easily make adjustments on the fly.
By relieving the panel of bass duties with an XO set at anything from 150 to 300hz, I can concentrate on mid & treble performance from the panel. From what I've read, an elastic boundary leads to a more even response in this region and also helps with unwanted panel resonance.
More later after the rugby final...
😀 ...now you can focus on those DML panels again – it’s probably more satisfying in the end. Looking forward to your findings.
Congratulations to South Africa! A fine performance and well deserved winners. Must do some ironing first before getting the measurement mic out later today.