Thanks Thanks:  0
Needs Pictures Needs Pictures:  0
Picture(s) thanks Picture(s) thanks:  0
Page 1 of 6 123456 LastLast
Results 1 to 15 of 81
  1. #1
    Join Date
    Dec 2011
    Location
    Brisbane
    Posts
    454

    Default Novice Speaker Builder

    Greetings...

    Well the time has come for me to step it up a notch a make another lot of speakers. In the late 90’s I made these guys using Vifa drivers and Polk Audio tweeters, which actually sounded fairly impressive considering I had never made speakers before.

    Last time around I did it the hard way with a drill, a jigsaw, a few half moon files, infinite patience, and more hours than I want to think about. Well this time I want to try using a router... I don’t see why my brother who is a cabinet maker should have all the fun. In fact I really don’t know why I didn’t use one last time; I guess I saw it as one of those tools that only professionals use.

    Last time around I used the facilities at a company in Brisbane called Wood ’n’ You to cut all of the boards to size, this time I want to use the router to do most of the cuts and not have to rely on a massive table saw to get perfectly parallel sides (besides not sure if there is a company that lets you do it yourself in Sydney).

    For this project I really want to step it up in every way. For drivers I am looking at the ScanSpeak Illuminator 15WU/4741T00 5.25" Midwoofer and the Scan-Speak Illuminator D3004/664000 Berylium Tweeter. For the centre speaker and mains I will do additional boxes with 2 Scan Speak 18WU4741T00 Illuminator 6½" Midwoofers in each. To kick off the project I want to focus on just the five Midwoofer and Tweeter boxes.

    Originally when I first started designing the boxes I was looking at building tapered shapes inside a square box to reduce the acoustic issues associated with square boxes, but as the various iterations of the box progressed I eventually decided that I would be better off trying to build the box in slices.

    I want to taper the inside of the box (and 3 of the outside faces leaving the bottom flat) so it gradually reduces as it makes its way back to the port opening. I looked on line and I can get an 11.25 degree router bit with a 15/16 cutting face which should be pretty close to spot on.

    Now this is probably fairly ambitious for someone who has never used a router before, but I seem to have a knack of being able to make most things work. I would really appreciate any design tips that you be able to pass along to a total novice.
    I have already spotted a few decent router circle cutters, and think I probably need to start my project there.

  2. # ADS
    Google Adsense Advertisement
    Join Date
    Always
    Location
    Advertising world
    Posts
    Many





     
  3. #2
    3RU is offline Electron controller/Manufacturer of fine shavings
    Join Date
    Oct 2009
    Location
    Burwood, Vic
    Posts
    138

    Default

    Good luck to you HS,

    I like your style and you obviously know something about speaker box design which is fine if you are doing it for yourself, possibly a very good friend. Sadly from experience there is a stack of stuff available for very little in terms of $.

    I have some very nice speaker boxes (Linear Design and Philips Resarch) sitting my shed which are virtually no value. Sounds good value $0

    Dave

  4. #3
    Join Date
    Dec 2011
    Location
    Brisbane
    Posts
    454

    Default

    Thanks for the encouragement Dave. I guess part of wanting to do it myself is it feels more satisfying if you put something of yourself into the end product.

    I didn’t wind up using the speakers I build above... I sold them to a good mate of mine for what they cost me to build (~$3000 for all 5 including the Jaycar amp, he bought a Polk Audio centre). To be honest I thought there would come a day when they would sound “ordinary” to me, but every time I would visit they still sounded fantastic. The mains were made of 19mm MDF and the sub box 32mm MDF. They are still going strong today a good decade later.

    I am allowing myself about a $10k budget for this lot of speakers and I have good reason to believe they will sound phenomenal when they are done (all going to plan). You see I currently own a set of Sonus Faber Cremona speakers (pre M series) which I pulled the drivers out of to see what they had in them. The drivers I plan to use in these new speakers should blow what I have into the weeds.

    So I really want the boxes to reflect the same level of craftsmanship that is on par with the sound. I was blessed with a great deal of patience and have spent countless hours before hand sanding thing to make them perfect.
    Having never used a router before I think I will probably trash a number of pieces of scrap, but I am excited about what could be if everything turns out right. On the back I was planning on putting some plexiglass or something similar to show off the cross over network. When you start spending big money on crossovers they can become a bit of a feature themselves with the gold writing etc.

    Calculations show that I need a port length of just shy of a meter to get the best X-max, so I was planning on building a slot port into a plinth that goes under the speaker. The good thing about making the port external to the speaker cabinet is I can play with port lengths to my hearts content. Because PVC is as cheap as chips I can just grab a length and keep lobbing some off and testing until I get the right length, then make my plinth to suit and then retest it.

    Edit:

    Here is a link to the tweeters http://www.madisoundspeakerstore.com...eryllium-dome/
    here is a link to the mid woofers http://www.madisoundspeakerstore.com...-woofer-4-ohm/
    and here is a link to the woofers that will be used in mains and centre http://www.madisoundspeakerstore.com...-woofer-4-ohm/
    Last edited by HeadScratcher; 5th Dec 2011 at 11:38 PM. Reason: Additional information

  5. #4
    Join Date
    Dec 2011
    Location
    Brisbane
    Posts
    454

    Default

    Here are a couple of photos I took while I had the speaker apart. I don’t want to give too many of their secrets away (not that the design is anything revolutionary, just known sound basic principals) but I figure I should be able to make this transition to the rear port area much smoother than using straight boards like those shown.

  6. #5
    Join Date
    Oct 2010
    Location
    Rockingham, Western Australia
    Age
    85
    Posts
    147

    Default

    Quote Originally Posted by HeadScratcher View Post
    Here are a couple of photos I took while I had the speaker apart. I don’t want to give too many of their secrets away (not that the design is anything revolutionary, just known sound basic principals) but I figure I should be able to make this transition to the rear port area much smoother than using straight boards like those shown.
    I must confess that I don't understand the principles involved in the unusual design of the speaker enclosures that you intend to make. Am I right in thinking that each disc has a smaller hole than the previous one and that there is a slight taper so that the resulting horn is smooth. If this is so, have you calculated the angle that the bit needs to be and in fact if such a bit is available.
    My own extensive experience is that a good selection of Imperial and metric template guides and bits is capable of a very wide range of offsets by mixing and matching..
    Your project is rather unusual and I hesitate to say, difficult for a newcomer to routing. Rest assured however that providing you supply photos/drawings and sufficient information, there are members here who will do their best to assist you with advice.
    The photograph appears to show a conventional fabricated horn , if this is so, why go to the enormous trouble of dramatically changing the method of construction,
    Harry

  7. #6
    Join Date
    Dec 2011
    Location
    Brisbane
    Posts
    454

    Default

    In a lot of ways I guess you could almost look at the cavity as being similar in design to many horn speakers… But the cavity in question is designed to control the volume of air behind the speaker.

    As you are probably aware… all speaker drivers have a preferred volume to create the desired frequency response. So the challenge that lies ahead is twofold.

    The first is to taper the walls of the cavity in such a way that it creates the desired cabinet capacity. This is going to be tricky but shouldn’t be too difficult as it’s a matter of just of working out the volume with math for each slice of the cabinet.

    The tricky bit is going to be working out how much to increase or decrease the internal size to meet the target volume without altering the length.

    The second hurdle that needs to be conquered is shaping the internal cavity in a way that helps reduce the pressure wave reflection.

    For those reading the thread that aren’t familiar with speaker design, it is important that the pressure wave of the speaker driver doesn’t run back into itself.

    Let’s see if I can explain this in simple terms without confusing everyone…

    Imagine a cube and in the front dead centre of that cube, you put a speaker driver that has a speaker cone that is a perfect right angle. When negative voltage is applied the speaker cone moves back.

    Now this backward movement of the driver cone pushes the air / sound waves towards the four sides (if the cone was flat it would have pushed it towards the back wall). Now remember that old Tennis video game of the 80’s. Remember what happens when it hits one of the walls…

    That’s right it comes off the wall at the same angle as it hit it. Which presents a problem because the next step is the rear wall, then the opposite side wall, then back into the speaker.

    The trick is to design the cavity is such a way that the pressure wave either never makes it back to the driver cone or is severally delayed and weakened. You see when the pressure wave is allowed to run into itself it causes distortion. Imagine two trains on the same track heading towards each other…

    Now think of the speaker driver in the same way but it is essentially a piece of coated paper. It is imperative the pressure wave is neutralised as much as possible, hence why in the photos above you will notice they crudely tapered the rear of the cabinet to delay the return, and help port the air out the back speaker port.

    If you can imagine that, you can now see why I am aiming for something that could roughly be viewed as a truncated pentagonal pyramid.

    Harry in my mock ups I calculated the angle of the taper to be ~9 degrees, and I can get a cutter around the 11 degree mark, which means I should with a bit of juggling be able to get the volume I want without have to compromise on other parameters like length.

    IMPORTANT NOTE:
    Before you all go running off and getting eggs stuck in milk bottles, or testing to see if you can get the speaker you have floating around move. Please remember that most speakers are designed to work with roughly 1 volt, so don't go sticking a 9 volt battery on the terminals to try it out.

  8. #7
    Join Date
    Oct 2010
    Location
    Rockingham, Western Australia
    Age
    85
    Posts
    147

    Default

    I reckon that you have a big task ahead of you considering all the variables, not the least of which are things like the amplifier's damping factor. Whilst the electronics can easily be performance tested using the right test gear, there are only two ways that I know of to assess speaker performance, using a white noise generator and calibrated microphone hooked up to a spectrum analyser in an anechoic chamber or subjectively using the ears of what we in the trade called the "golden eared brigade" , some who swore that they could pick the difference between speakers connected using mains cable and "Oxygen free copper monster cable". There also on the market were so called "Oxygen free mains cables" with instructions saying that they required I think it was several weeks to be "run in"!
    I couldn't openyour link, and finally, "speakers designed for only 1 volt", as Pauline would say,"please explain"!
    Harry

  9. #8
    Join Date
    Dec 2011
    Location
    Brisbane
    Posts
    454

    Default

    1 volt RMS is the nominal voltage for Line Level

    “The reference voltage for the decibel volt (0 dBV) is 1 VRMS, which is the voltage required to produce 1 milliwatt [mW] of power across a 1 kiloohm [kΩ] load.[1] The reference voltage for the decibel unloaded (0 dBu) is the voltage required to produce 1 mW of power across a 600 Ω load (approximately 0.7746 VRMS).[2]

    1 watt or 2.83v is what most speaker manufacturers rate there speakers at.

    “Sensitivity – The sound pressure level produced by a loudspeaker in a non-reverberant environment, often specified in dB and measured at 1 meter with an input of 1 watt (2.83 rms volts into 8 Ω), typically at one or more specified frequencies. Manufactures often use this rating in marketing material.”

    Subjecting a speaker to too much voltage can damage the speakers’ voice coil, as a speaker is just a big role of wire (voice coil) wrapped around a metal rod, applying positive or negative charge moves the metal rod back and forth.

    You are basically creating a short circuit, and applying too much voltage is going to fry the voice coil.

    I was looking at purchasing one of the EarthWorks measurement microphones to measure the finished speaker and get the cross overs sorted out. Not cheap but think it will be handy for all sorts of setting up. http://www.earthworksaudio.com/our-microphones/m-series/m30/

  10. #9
    Join Date
    Oct 2010
    Location
    Rockingham, Western Australia
    Age
    85
    Posts
    147

    Default

    I'm aware of most of what you say but the word "sensitivity" hadn't been mentioned. I don't see what line level has to do with speakers other than to compare sensitivity
    Please tell me, a woofer of 8 ohms impedance dissipating 50 watts from an amplifier being fed with a 1Khz sine wave, what is the voltage across the voice coil? By the way, I started re-coning speakers in 1962 and only stopped in about 1987 when a clever young electronics engineer here in Perth commenced business designing and building class A amplifiers and needed some cash flow and so started to repair speakers, including cone tweeters by re-winding the voice coils, and making new formers and surrounds where necessary. From that point onwards I sent all my incoming speaker repairs to this young man.
    I'm really not trying to have a go at you, it's just that from years of experience I've learnt that theory, where speaker enclosures are concerned, is only part of the story for a successful speaker system and if the results are measured subjectively then we must remember that one man's meat is another man's poison!
    Harry

  11. #10
    Join Date
    Dec 2011
    Location
    Brisbane
    Posts
    454

    Default

    Getting slightly off topic but the point of mentioning sensitivity was if speaker manufacturers only deem it necessary to use 2.83v to reference speakers, I didn’t want people testing speakers with a 9v battery.
    Anyway totally agree... what works in theory on paper may sound terrible in the real world. Really won’t know until I fire them up, but if I try to stick to sound audio principles I have half a chance of them sounding ok.
    Staying away from what is known not to work well i.e. square sided cabinets, I have to be at least heading in the right direction.

  12. #11
    Join Date
    Oct 2010
    Location
    Rockingham, Western Australia
    Age
    85
    Posts
    147

    Default

    Please do post a few shots taken during the routing, I'm fascinated as to what you're doing. Finally it would be nice to "hear" your unbiased opinion when they are completed, also what equipment is hooked up to them. Good luck.
    Harry

  13. #12
    Join Date
    Dec 2011
    Location
    Brisbane
    Posts
    454

    Default

    I think the truly great thing about the design is the ability to custom make the wall thickness, I will be in control of both ID and OD, so I can make the walls as thick or as thin as I like. Kind of excited to hear them myself, but being a realist I will be very self critical.

    I won’t know straight away because all the drivers will be brand new and green, so it will probably take about 100 hours of playing before they start to sound right.
    I progressed through the Sonus Faber range, and every speaker I bought needed a good break in period to sound like they should. Even my current Cremona’s sounded ordinarily when I took them out of the carton for the first time.

    The only speakers I brought home and sounded fantastic were my Electa Amator series 2 which were demonstrators and had quite a number of hours already on them. I still regret selling them they were superb speakers. It was a real pity they were only a bookshelf.

    You mentioned earlier about different cables... to be honest you can pick the difference between the different cables, but the difference often doesn’t justify the price.

    For many years I was running cheap old NeoTech KS1226 Super Base Line Speaker cable (2 x 8AWG) and I replaced it with some Cardas Crosslink 2x. I could pick there was a difference in the lower frequencies between the NeoTech and the Cardas with all other things being equal (The NeoTech had slightly stronger bass, but the Cardas are slightly more defined).

    You asked about equipment, leading the way is the Oppo BDP83 Special Edition (the SE is well worth spending the extra $500 just to get the better DACs) into a Rotel RSP 1570 into a Rotel RB1091 (Centre) and RB1092 (Mains) and an analog Rotel RB1075 for surrounds. I use IXOS interconnects exclusively, the Poms sure do know how to make a good interconnect cable.

    By the way I got a quote for the 5 tweeters and 5 mid woofers they came in at $4360. Might be able to squeeze a few more bucks off that, but don’t expect much. Even with some decent crossovers (~$2-3k) I am only still looking at the same kind of money that I paid for the Electa Amators but I will have 5 speakers not just a pair.

  14. #13
    Join Date
    Oct 2010
    Location
    Rockingham, Western Australia
    Age
    85
    Posts
    147

    Default

    "I won't know straight away because all the drivers will be brand new and green, so it will probably take about 100 hours of playing before they start to sound right."


    I hate to have to tell you, but there is no such thing as a GREEN driver. Nothing changes with a driver, have you not considered the more rational explanation that over time one's ears become accustomed to the new sound?
    Harry

  15. #14
    Join Date
    Dec 2011
    Location
    Brisbane
    Posts
    454

    Default

    Hate to disagree with you Harry but there is definitely an audible difference between a green speaker and one with some miles on it. I appreciate your experience in this field but beg to differ.

    I would liken it to putting on new set of disc brake pads; there’s a bedding in period where the new discs mate to the rotor surface. The cone of the driver is no different, as you know from your experience the driver cone has a certain amount of give in it despite the manufacturer best attempts to keep it solid.

    Think about the surface of the cone at a nano level. Just like a piston engine the cone stops and reverses direction constantly. Where the cone is held at the centre is where the energy is introduced into the cone.

    Now think about shaking out a tea towel... the ripple effect starts at your hands and makes its way to the other side of the tea towel, this is exactly the same thing that takes place in the driver cone.

    Now try the same thing with an old tea towel and a new one and you will see that they shake completely differently and in different patterns, the new one is much stiffer because the fibres of the cloth have not been subjected to wear and movement created by drying up over time.

    At a nano level the fibres of the paper have to achieve this same state, the constant backward and forward movement of the cone settles the grains of the cone into a position where they are properly aligned and happy.

    You probably wouldn’t notice it so much on driver that has an aluminium cone (but you pay for it in a very unnatural sound), but every material known to man has some form of settle in period. Even glass which is actually a viscous material is in a constant state of flux. Don’t believe me look at the windows in a very old church, the windows are thicker at the bottom then they are at the top where the glass has moved over the centuries. It is this extremely minute movement in the cone that has a significant difference in sound.

    I can back this up with having heard some floor stock that had been in place for quite some time and hearing the exact same speakers that were straight out of the box that were going on the floor as new demo stock, and there was a world of difference between them. So I believe there is much more to it than merely getting used to them. Just my opinion and you are welcome not to agree.

  16. #15
    Join Date
    Oct 2010
    Location
    Rockingham, Western Australia
    Age
    85
    Posts
    147

    Default

    Likewise, I hate to disagree with a fellow forum member, but your analogies are way off the mark, exactly the sort perpetuated by non technical Hi-Fi salesmen, I know, I've worked side by side with such people. Whereas brake discs actually WEAR to match the disc, as you have rightly said, a cone is a piston, suspended at it's outer edge by a very resilient foam or rubber surround and at it's centre by by a fabric suspension. Modern cone materials do not change their molecular structure, unless of course the speaker box is used without it's front cover in a room with bright sunlight! (as I've seen so many times)
    As for the tea towel, the first several washes gets rid of the starch which is introduced during manufacture to make it look nice and crisp.
    I mentioned in an earlier post the mains cords made from "Oxygen free Copper" selling at an exorbitant price, if the instructions didn't claim a long "running in" period, everyone would immediately return them for a full refund because they, quite rightly couldn't hear any difference, but at the end of the "running in" period, how could one really tell if there was any difference. Consider the miles of cables and the number of transformers between the power station and the audiophile's power point and one wonders how a 2 metre cable will improve the fidelity! In a similar vein, how can a few metres of "Monster" cable improve the fidelity of a loudspeaker, it's fractionally lower resistance you might say but what is a fraction of an ohm compared to around 6 ohms for a typical 8 ohm driver. I could go on but she who must be obeyed is calling me for my evening meal.
    Harry

Page 1 of 6 123456 LastLast

Similar Threads

  1. A little help for a novice builder
    By highace1 in forum Michael Storer Wooden Boat Plans
    Replies: 15
    Last Post: 30th Oct 2009, 06:33 PM
  2. Speaker Stands
    By Reno RSS Feed in forum KITCHENS, BATHROOMS, THEATRES, etc
    Replies: 0
    Last Post: 26th Jun 2009, 01:00 PM
  3. AMP and Speaker done
    By Strungout in forum MUSICAL INSTRUMENTS
    Replies: 14
    Last Post: 17th Mar 2009, 09:58 PM
  4. Viva speaker builder site
    By la Huerta in forum HI FI EQUIPMENT
    Replies: 0
    Last Post: 28th Apr 2007, 10:39 AM
  5. Speaker Boxes
    By Iain in forum WOODWORK - GENERAL
    Replies: 11
    Last Post: 25th Jul 2001, 11:40 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •