Announcement

Collapse
No announcement yet.

Rebuilding Akai SW180 speakers

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • Rebuilding Akai SW180 speakers

    One has 2 16ohm blown tweeters, no sound output, and infinite ohms across leads. Blown?
    The mount bracket is square on each tweeter, square, 1 and 7/8inch distance between screws.
    I may replace the woofers down the road, will tackle that after the tweeters.
    Thx, Tom

  • #2
    Sounds like they are dead. Good luck on the project. I suspect that those are really super tweeters and crossed pretty high. 16 ohm tweeters are pretty rare, especially anything that fits those holes. I would suspect that they were wired in parallel to get an 8 ohm load. I found some specs and if they are to be believed these things are supposedly 102db 1W (who knows what the distance was) and the tweeters crossed 2nd order at 7kHz. Most likely you'll need to find two 4 ohm tweeters that will fit and wire them in series for 8 ohms, Or use two 8 ohm tweeters with each one having a series 8 ohm resistor on them to make them 16 ohm each and wire them in parallel like the originals. If you do not get the load correct, the crossover function will be way off.

    2nd is finding a pair that are loud enough to do the job. If you want them to look close to original.... I would think about maybe trying to cut one of these down with a dremel to fit and using an 8 ohm (5 to 10 watt) resistor in series with each one:

    https://www.parts-express.com/3-3-8-...eeter--270-055

    or

    https://www.parts-express.com/eminen...-horn--290-532

    Other options options will probably require cutting the baffle in order to fit some other vertical rectangular horn type driver in there (domes or cones just won't get loud enough). If you thought you were going to replace the woofers too, this changes a lot of things. First you'd probably be better off designing a new crossover that will work properly with the new drivers, and secondly a new XO design opens up the door for a whole bunch of tweeter options.

    A lot of people who are resurrecting these old but neat looking speakers are replacing the baffle entirely and designing a new speaker from scratch for the enclosure volume. My suggestion is to try trimming those aforementioned tweeters down first unless you are willing to go down the rabbit hole of designing a speaker from scratch. Or you could try locating some working originals, or another set of the speakers with damaged cabinets (so you can salvage the parts from them) on ebay or something.

    Here is the specs I found on them:

    http://audio-database.com/AKAI/speaker/sw-180-e.html

    Comment


    • #3
      Yes they are 7000 hz, I am replacing everything, soofers, mid, tweets. xover too. The enclosure appears to be pretty conventional, and Morel has the MDT model that will practically drop in, has 90+ sensitivity. I know I have alot of work to do, but I succesffullyy brought a couple of Onkyo Radian 3s to life, and although flawed, musical, have a decent soundstage, and good midrange. My references are JBL L7 and L77, separated by 3 decades, but kindred.

      Why do you think they had to go with such sensitive tweeters?

      Comment


      • #4
        That is the sensitivity of the complete speaker, so the mid horn and the woofer should be close to that as well, not just the tweeters. Many speakers were designed to be very sensitive in order to get loud with little power.

        Comment


        • #5
          Glad yu brought this up... if a woofer has 90db sens., what range should the midrange and tweeter be in? 85-95?
          Also, how does one tune a box or enclosure?

          Comment


          • #6
            Well it is more complicated than that. A driver, say a woofer that is 90db 1w/M may not be that sensitivity throughout it's range and that spec is usually an average. Some have rising frequency response, some falling, some flat etc... What you need depends on your target goals and the response of the other drivers. If you like a falling response on a speaker or they will be out away from the walls and require baffle step compensation... You can sometimes get away with a mid and tweeter that isn't quite as loud. If you want flat response or they will be up against the wall, then you definitely want something the same level or louder. Since you will need to design a new XO the easiest thing is to go louder on the mid and tweeters, then use an l-pad circuit to reduce the volume of those drivers until they are in the range you need.

            On a separate note, if you want to do this.. Which is essentially designing a speaker from scratch... It is optimal to have a measurement microphone, measurement jig, and software (much of the software is free). Using these tools you can use them to create FRD and ZMA files (frequency response and impedance curves) that you can use in a piece of software like WinPCD in order to simulate/design your XO. If you use all Dayton drivers, they usually publish these files for people who do not have measurement tools.

            Some folks use tracing software to trace the graphs that a manufacturer publishes in order to create files. These are usually close enough for horseshoes for many and better than nothing... But measuring in cabinet to create your files (or use dayton drivers and their files) is usually a little better. There are a few of these tracing programs out there, one is called SPL Copy. I haven't used any of them, so I cannot say which is easier to use or better etc..

            Tuning an enclosure in the case of a bass reflex enclosure requires knowing the enclosure volume and some math to determine the appropriate port diameter and length to allow it to resonate at the desired frequency. The smaller the diameter the port is, the shorter it needs to be in order to achieve the desired tuning. But if the port is too small in diameter, it will make noise due to turbulence.. Often referred to as chuffing. Sometimes port size becomes a balancing act of enough diameter vs. how long of a port you can fit in the enclosure, especially if it is small. In the case of your Akai's, they are probably big enough to use whatever port you need. The first thing I would do is measure the internal dimensions of your enclosure to find out it's volume. Once you know that, then you can use a program like WinISD in order to plug in the parameters of a woofer and the enclosure volume, then play with tuning to see if a woofer will work adequately in your enclosure volume.

            If you're new to this stuff, it might seem a bit overwhelming... But with a bit of study and dedication most people can do all of this. At the top of the tech-talk forum is a sticky for "The Speaker Building Bible". It would be a good read for you. Here is a direct link:

            http://techtalk.parts-express.com/fo...building-bible

            This is also a good rabbit hole to venture down after you read the bible:

            https://www.calsci.com/audio/X-Overs.html

            Comment


            • #7
              Also, "SpeakerBuilding 201" is a really great addition to your (reference) library!

              Comment


              • #8
                Thanks you guys, I am biting off enough to hang myself here, ha ha. There is also a midrange horn on these, midrange horn 270mm x 95mm flange, 280mm deep. So far the Pyle PH391 4" x 10" Horn Tweeter
                Brand:Pyle Audio
                |Model: PH391|Part # 292-2624 looks like it will fit.
                I bought a microphone some time ago from PE to go with these software packages mentioned above, but don't understand how to interface them to a laptop. Just through the MIC input? Or a USB?

                Comment


                • #9
                  Depends on the microphone. Which one did you get?

                  As far as the midrange... If the factory ones work, I would keep using them. For one, they are crossed in your speakers at 700hz with a 2nd order crossover which means they go low enough to match a large woofer. While many big woofers might have usable frequency at 1K or higher, the radiation pattern isn't very good and the frequency response up there often gets kind of choppy unless it's a high end driver.. Above a certain frequency the cone starts to act like a horn and beam the sound at you. The smaller the cone the higher you can go before it is beaming. With that said a horn mid and horn tweeters are already beaming a bit so it may be a moot point. Taking that into consideration, you can probably get away with a mid horn that can cross in the 1500hz region so long as the woofer you choose is fairly smooth to that point.

                  Secondly, while the Pyle mid/tweeter says it goes down to 1k there is no published Fs spec for it. Often with cheap tweeters, the lowest frequency that it can play listed in it's specs is often Fs. While this is technically correct (It probably can put out a 1k tone) it is also misleading. There is a difference between what it can play, and what is usable. Generally with most tweeters you want to crossover at twice the Fs at a minimum in order to not blow the tweeter up and to minimize distortion. Both of which are caused by feeding it a lot of signal near and below Fs. It is possible to crossover at or near Fs, but it takes a super steep crossover such as a 4th order which is a ton of parts and costs more to accomplish than the cheap tweeters cost. It's easier and better to buy a higher grade tweeter and need less crossover parts for the same amount of money as a cheap tweeter and a ton of parts. I would assume you wouldn't want to cross that Pyle any lower than 2k. But without measuring one to see what it's Fs is, it would be hard to say.

                  As you can see, it is often hard to find stuff to fit some of those old baffles that also works well.. This is why many folks cut the old baffle out and replace it, or plug the holes so that they have a blank canvas to work from. If you want to rebuild them with all new drivers and not have to do this kind of wood working.... It is easier to make a hole bigger than to make it smaller. My suggestion would be to look in PE's pro audio section and look at waveguides that will fit, then find a horn driver to attach to the guide that will also work.

                  Waveguides: https://www.parts-express.com/cat/horns-waveguides/34

                  Horn Drivers: https://www.parts-express.com/cat/horn-drivers/33






                  Comment


                  • #10
                    Thanks for your response... so you are saying the waveguide plus the driver will be higher quality than the Pyle and greater range in Fs or crossover point? I guess that makes sense. One of my horns measures 4 ohms and the other measures 7, not good I am assuming. The previous owner must have zapped it good. The baffle contains 2 ports above the woofer hole, 75mm diameter, 155 long each. There are a few woofers with Qts down around .4 to.5.,
                    on PE website.

                    Comment


                    • #11
                      Am currently reading the "Bible"

                      Comment


                      • #12
                        3 ohms difference isn't good that is for sure. Before you give up on them, make sure the terminals are good and clean. a film of oxidization etc... can cause the discrepancy. Generally speakers either work or they don't. If you put enough current into it to fry the voicecoil it will almost always measure infinite and they simply will not make sound. If they were hot enough to simply make the voicecoil out of round and it drags on the pole piece, that shouldn't usually change the resistance much. It would still make sound but it would be distorted etc..

                        Yes with the right driver on a big wave guide you should be fine and it would be far better than that Pyle. Most of those drivers are going to be tweeters rather than mid or mid/tweeters so you'll have to dig a bit.

                        While QTS has some input on if a speaker can run ported or sealed, it's not a definitive answer. Many good speakers have been made by working around the rules and many woofers in the .4-.5 range work well in both sealed and vented enclosures. With the enclosure volume added to the port sizes you listed, we can help you determine a good woofer for it. What is the internal volume of the cabinet or at least it's internal dimensions?

                        Comment


                        • #13
                          Tried cleaning the posts, same result. I remember the old owner saying he thought every driver was blown. Oh well. The microphone I bought was the
                          Dayton Audio EMM-6 Electret Measurement Microphone
                          Part # 390-801

                          I will get the dimensions tonite.

                          Comment


                          • #14
                            Canyou use something like this to adapt microphone to usb?
                            https://www.bing.com/search?q=microp...0F4AD61DDCEF28

                            Comment


                            • #15
                              So long as the xlr to usb adapter supports phantom power, it will work. Some do, some don't. Look at something like a Behringer U-Phoria UM2

                              Comment

                              Working...
                              X