mwiener Posted June 11, 2015 Share Posted June 11, 2015 (edited) I just completed this project doing a number of mods to my 77 La Scalas. During the last two years I built the La Scala risers for bass extension, added the ALK CSW crossovers to replace the aging AA crossovers, and I replaced the K77 horns with the Eliptrac DE120 also from ALK. Thanks Al K. for the recommendations, it was spot on. While doing this, I measured the incremental improvements in each mod to make sure that there was actually a measurable improvement. Chart showing frequency response improvements below. I can say now after the fact that I am really happy with all of the mods. I still have a little work to get to my perfect 2 channel setup, but the work I did hear in 2 years eliminated about 90% of the gap between where I was - to where I want to be. For the frequency testing I used a Studio Six Digital iTestMic which is a calibrated test mic equivalent to having a pro Type 2-class test & measurement mic. The mic is $200 from Audio Control. It plugs into the iPad directly and bypasses the mic on the iPad. Also on the iPad you run an app from the same company called Audio Tools. It is a $20 purchase on iTunes. The Audio Tools app has a number of applications, the ones I use the most are FFT, Real Time Analyzer, SPL Meter, and Signal Generator. The SPL Meter for home theater setup beats the radio shack analog meters hands down. I got much better results with that application and the iTestMic. When you buy an app in iTunes, you get the use of that application on up to 5 physical devices that are tied to the iTunes account. When I bought Audio Tools app, I have access to it on all 5 Apple devices I own. That allows me to run pink noise on the Signal Generator on 1 iPad and feed that through the stereo by using a standard RCA input into an unused preamp input from the iPad headphone output. I run a second iPad with the iTestMic running the Audio Tools FFT application to measure the results. With Signal Generator you can do sweeps, specific frequencies in a sine wave or square wave, white noise, and pink noise. I used pink noise for my tests which is equal intensity across the entire spectrum 20-20,000 hz on the signal generator application. Ideally the graph resulting from the Audio Tools FFT application would be a straight line representing exactly the same frequency response generated from the La Scalas across all frequencies 20-20,0000hz as heard by the iTestMic and the FFT application. My testing was as simple as setting up the volume on the amp, running pink noise on the signal generator at a pre set volume, putting test microphone on a tripod connected to second iPad running FFT, and testing each configuration one after the other without changing anything. I used the screen capture capability of the iPad to capture the frequency response in a jpeg image. I did get some coaching from Andrew at Digital Six Studio, I can share the details for FFT setup if you want them. Keep in mind these results are specific to my room. My stereo in your room could be perfect, or it could sound horrible. Also keep in mind low frequency measurement is dependent upon where the microphone is physically positioned. Move the microphone around the room, you change the measurement. Here is a picture of the testing setup: I built my risers a little different. I shortened the riser by 3/8” so I can place a grill using the same speaker cloth material as the material covering the tweeter and horns. BTW, I am looking for some black Heritage #17 cloth if anyone has any. Eventually I will make the grills and hold that in place with small neodymium magnets. I also used the Precision Port flared 4” port tubes from Parts Express. I started with the port tubes at 8” instead of the recommended 7”. I can always shorten them, but to my ears the 8” sounds like a good compromise between the lower frequencies and the fast bass response I am used to in my La Scalas. Interestingly with the flared ports, if you want an 8” port, you actually make the tube structure 9” because they do not count the second flare on the inside as part of the tube length. I also used ¾ dowels to add support around the doghouse. You can see the Precision Port 4” flared port I used at Parts Express, it is part number 268-352. You can also Google 268-352 and see it that way. I have switched back and forth several times. To make it easy to switch back to stock, I chose to put the sealing foam that goes between La Scala and riser on the bottom of the La Scala speaker itself. Then I can place the stock speaker on the original plywood base, or I place the speaker on my riser. I can clearly hear a loss in the low end without the risers, although with the test information you can see that the differences are not huge, they are measurable, and to my ear the difference is greater than indicated in the graph. Keep in mind that I listen 10 ft behind where the test microphone is placed, this could account for hearing a bigger improvement than is depicted on the graph because the bass response may be greater at that listening location. Here is a picture of the riser build. This shows the inside of the riser before I put top on with the doghouse cutout. The top is glued to those dowel sticks as well. It is pretty solid when all put together. The epoxy I used is really good stuff, we race wood boats made with it and it lasts for 10s of years running at or over 100 mph on the water. Here is a picture of the finished speaker and riser: If you want the information on the finish used on the risers, you can find that at: https://community.klipsch.com/index.php?/topic/148545-any-consumer-black-lacquer-spray-paint-that-matches-lascala/ I took measurements after each mod, but probably the best one is the comparison between the stock speaker and all the mods. To do that I had to do a photo shop modification of the stock measurement in one layer and the last measurement in a second layer with both graphs visible. This is where the differences are really apparent. The pink line is the original stock measurement, and the white line is the measurement after all the mods. The CWS cross over gives you the capability to bump both the tweeter and the squawker up by 1db increments. I currently have the squawker set to 1db above the factory preset of -6db I can see a spike at above 650-700 hz that I might be able to fix by pulling the squawker down to -6db. I will get to that eventually, but I suspect that while I might fix that anomaly, I might create other problems. I set the Eliptrac DE120 tweeter as high as it would go. You can see its better than it was, but I still have an anomaly I would like to fix at 7k where it steeply drops off then comes back at 8k. I like a hot tweeter, and this is getting close to perfect. I used to not like any recordings I had without adjusting the treble, but now depending on the recording I am pretty happy with it totally flat with the tone controls out of the music path. If I could get a little more out of the tweeter, I would probably like all my recordings without treble, that is why I am thinking if I can fix that 7k drop off, it might be perfect for me. Looking for any suggestions on flattening out between 7k and 8k. Let me know if you have any questions. I certainly have a lot more data, but I tried to keep this as brief as possible, otherwise it would be a pretty long and potentially boring read. Edited June 12, 2015 by mwiener 4 Quote Link to comment Share on other sites More sharing options...
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