Tim Mackey Posted July 31, 2011 Share Posted July 31, 2011 Theres a few posts already over HEREPlease continue here. TY Quote Link to comment Share on other sites More sharing options...
Dusty Posted July 31, 2011 Share Posted July 31, 2011 Ta Tim, amazing what the Gods can do Ok so pictures tell many words? The first out of 2 speakers i have decided to mount on the underside of the cowling, many reasons for this! I had proposed the wings as the main platform for the housing of the speakers, I turned away from this option as to the internal structure of the DBSpit wings as to not induse any weakness into the internal structure. Thinking back now I could have used smaller speakers but it's to late now, so I hope other's can help me on this journey of achieving satisfactory sound out of a model this size! exhaust outlets opened up to hopefully expell some of the sound as well as the warm air from the motor, esc and sound system amplifier...? This is how the 10cm speaker looks like under the cowl, I have actually mounted the speaker to the inside of the cowling and baffled the inside area with depron, this wont probably make any sence until you see a image of the inside cowling. As building progresses I will remove the cowling so we can see! Quote Link to comment Share on other sites More sharing options...
Dusty Posted July 31, 2011 Share Posted July 31, 2011 Under the rainbow of wires and motor lies the speaker! The chosen power train (after selling a model or 2, is the Hacker A60-18M with a dedicated mount to support the motor shaft via a ball bearing at the firewall end. This is to have a secure motor mount but also to have the motor as quiet as possible I hope... More photos and detail to follow... Dusty More to follow, any ideas and suggestions are welcome! DJ's are welcome! Dusty Edited By Dusty on 31/07/2011 20:15:43Edited By Dusty on 31/07/2011 20:21:51 Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted July 31, 2011 Share Posted July 31, 2011 Hi Dusty, If this is of any help I sometimes make boxes with about 25mm sounders inside to warn that a video camera mast is still extended wnen the vehicle it is installed in tries to move. I found that with these fitted to a 2mm thick box with multiple holes drilled gave just a squeak instead of a loud blast. The face of the sounder needs to be flush with the external surface to work, so the sound plate needs to be the surface of the model as I see it. A speaker inside say a cowl would do nothing as the outlet area would be minimal compared to the surface area of the speaker itself. A bit like trying to play music indoors and expecting your guests out on the patio to be able to hear it properly. Best of luck with your experiments as I think that we could eventually get some realistic sounds from electric models. Martin Quote Link to comment Share on other sites More sharing options...
Dusty Posted July 31, 2011 Share Posted July 31, 2011 Thanks Martin, Interesting you say to get the external suface to work, do you mean by using a external surface to "bounce" distribute the sound waves to achieve a acceptable volume? Point taken... Dusty Quote Link to comment Share on other sites More sharing options...
Malcolm Fisher Posted July 31, 2011 Share Posted July 31, 2011 I am probably an "old fart", but why do this at all? Electric flying is promoted as being quiet. If you want noise, why choose an electric power plant with the complexities of a sound system instead of a good IC motor? Malcolm Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted July 31, 2011 Share Posted July 31, 2011 Yes. the sounders we use need to be almost totally exposed (a large hole) so I would have thought that using a wing skin as a sound plate should work although, not having a model sound unit myself, this is only theory. If in the above example you put the speaker cone against a window pane then the sound would be transmitted to the patio. MartinEdited By Martin McIntosh on 31/07/2011 21:34:35 Quote Link to comment Share on other sites More sharing options...
Dusty Posted July 31, 2011 Share Posted July 31, 2011 Martin, Ok maybe we need to start testing, right the speaker is mounted as close to the surface of the cowling as possible, obvioulsy the cowling is of a curved nature and the speaker is flat, so the mounting lugs of the speaker are screwed into hardened balsa blocks glued into the inside of the cowlng acting as "dampers" to absorb any vibaration/distortion? How would a speaker react to being placed near a electric motor, another tech question? Malcolm, its a quest, I fly petrol, glow, electric etc and want to give this a go!! Its got a volume control if all is too loud so hey ho!! It wouldnt work well with a IC engine so the idea is to use the "quietest as possible" power train to achieve the hoped for results of a realistic engine sound, quite a vast hobby these days IMO! Cheers Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted July 31, 2011 Share Posted July 31, 2011 Hi Dusty, there has been a great deal of work started by Pete Nichols, carried on by John Ranson into developing sound systems for the models. John as you know helped develop (and still does, with Thomas Benedini) the TBS sound system.John has done a lot of research into speakers and has spent a considerable amount of time and money on searching for the best speakers for this. I myself sent some rather promising Blaupunkt's to him for analysis, only to find they are only capable of 101db which is a good couple of db down on the current best he has found (Visaton)I am still optimisitc however on the Blaupunkts, becuase I feel if the speaker can handle lower frequencies better, then it may not be down to shear power. Another friend in Norway (Stian) posted this, and I hope he doesn't mind his thoughts being re-produced here, but he explains better than I could why the better speaker may be loader on the lower notes than the Visatons which have a much higher Q rating. Making sound is the art of moving air, you need a movable surface and some travel.So a speaker with a given size is limited by some physical laws. two speakers with the same surface area will power wise be fairly equal. Separated by its abilty to travel. Each driver can be tuned differently, if you want lowfrequencies, sensitivty and max power suffer, but could sound better and "richer". A tweeter for instance can play really loud, but only if the lowfrequencies is filtered away. An earplug can go really low in frequency, but only if you put it in the ear and power demand is low.So if I want a speaker to go lower in frequency I need more travel. This will bring with it more distortion and require more sophisticated magnet design.Then theres the problem of measuring sound pressure level. If all frequencies are considered equally important its fairly easy, but thats usually not the case. The standard of dBA is an attempt of giving a number on how "stressful" the noise is on our ears(guessing a little here now), they are fine tuned on human voice and natural sounds, because evolution tells us those sounds are important. Perfomance in low and high frequencies are downvalued and the midrange is made important. Look at these curves:http://en.wikipedia.org/wiki/A-weightedIf you have a sound at 1000Hz at 100dB, the dBA meter will show 100dB,but if you have a sound at 50Hz at 100dB, the dBA meter will show 70dB.. (or something like that) Point is, measuring with a dBA meter, extra power in the range 100-200Hz won`t show up much, especially compared with extra power in the midrange.In a high quality speaker system however a flat frequency respons and a widest possible frequency range is desired over high dBA rating.I don`t yet know what performs the best in models, but I know I am sceptical to the high Q of the Visaton and I want the low frequency respons more than a few dB extra. With only one speaker I think it will be too weak to hear over the noise of the prop and plane at distance anyway so I am trying to get it to sound right more than loud for taxiing, take off and landing. The criterias of a Hifi speaker still float around my head. Anyway, if nothing else listening to a Merlin cough into life on the bench at 101db before throttling up to a solid neighbour annoying roar, is awesome I never get that same feeling listening to a Zenoah or an OS 4 stroke, its either a Merlin or silence for me. And I think it really is worth all the effort Will be really interested in seeing how you get on, and how effective the sound is in the air. The link to Stians Spitfire build thread. This is the 101db Blaupunkt, in my Mustang, the sealed sound box runs from the behind the cockpit to a couple of inches in front of the fin, nearly full depth. CheersDanny Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted July 31, 2011 Share Posted July 31, 2011 Just spotted I had put Pete Nichols, someone i used to work with , the guy that did a lot of Model sound pioneering was Pete Nicholson, sorry bout that lapse in concentration.... Note the date is June 2006 its come along even further since.... CheersDanny Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted July 31, 2011 Share Posted July 31, 2011 These are from Petes build blog on RCGroups CheersDanny Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted August 1, 2011 Share Posted August 1, 2011 Dusty (& Co.) I understand your reply to Malcolm explaining your reasoning and the sound of a Merlin (or a Wright radial, Gypsy Major, Napier Sabre etc. etc. or even a Lycoming) is music to my ears but talk of 101 dB speakers (no distance quoted and I do appreciate how meaningless this figure is in isolation) and the quest for ever louder and more realistic sound has got one or two alarm bells ringing. Is there any possibility of the status of electric flight being referred to as silent flight and largely exempt from planning controls being jeopardised by these activities? I must say that some electric models (and I'm not referring solely to EDF) are getting very loud and in some cases are worse than quieter IC models - and in the case of an F5b model, by far the noisiest model at our club! (in < 2 second bursts) The video above is really impressive and the best I've watched - in most of the ones I've heard the whine of the motor is audible above the sound system although I admit to never hearing one live. Has anyone thought to take a noise reading at 7 Metres of a comparable example? I'm playing Devil's Advocate here - I think anything that improves the realism of a scale model is great from the standpoint of a modeller but the general public may not share the same feelings... Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted August 1, 2011 Share Posted August 1, 2011 A workmate was recently repairing an I-pod amplifying system which consisted of a couple of very tiny speakers fed into a circular, tubular horn. The lower frequency sounds were truly amazing and the whole assembly was around a large model fuselage cross section size. May be worth a look at. Martin Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted August 1, 2011 Share Posted August 1, 2011 Just brainstorming but how about a different approach... Using telemetry, onboard GPS (currently available from several radio systems) information fed back to a CPU which relates model position/vector to pilot/flightline in a ground based sound system (as good and heavy speakers/amplifiers as you like) and uses throttle position and airspeed information to provide sound as would be heard at the flightline including simulated doppler effects. Resulting in realistic sound to the user but little annoyance to the neighbours! Possible use of headphones if the other members objected to the sound - although flightline communication would be an issue but not insurmountable with a microphone input. And it might be rather effective at shows via the PA system!Edited By Martin Harris on 01/08/2011 01:49:31 Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted August 1, 2011 Share Posted August 1, 2011 Hi Martin H, I am pretty sure, but was trying to find the note I have, that we are talking 102db at 1 metre, so not as loud as an IC engine. It is also a lower pitch.That speaker sounds very strange, have you tried it with a Merlin sample file from the TBS web site? Got to be worth a try CheersDanny Quote Link to comment Share on other sites More sharing options...
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