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AR303 and classic 18 user

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  1. Ar303 info.

    I had some time to verify the calibration I was using. Although not strictly AR related, I thought it would important for people to be aware of the calibration since it is critical to the final result measurements. I went through the process of verifying the calibration of my RS meter using the stereophile review data as a reference. Although not strictly a true calibration, the resulting validation calibration should allow for a determination if the original calibration file I am using for my meter is reasonable or not. (I don’t have the equipment to do a full calibration.) To start out, I total took system measurements for my 303 speaker system. These measurements were performed at 1 m and 1 volt. The raw impulse data was saved so that the various calibration data could be applied to generate the various system responses. I started with calibration data in the RS 2050 manual, made, a system frequency response curve and compared it to the stereophile reference. This data is plotted in Fig 1. The match isn’t outstanding but I think one can see that there are major features in both the user 303 and the reference 303 that correlate like the dip at 1 kHz and the peak at 6 kHz. (Looking at the reference stereophile data it can be seen that the response of the AR 303 is very flat. ) With this first iteration complete, I calculated the difference between my system response and the reference system response (Fig 1. green plot). I then corrected the radio shack calibration by the same amount, generated a new system response with the corrected calibration and repeated this process for several iterations. The results for the final iteration are plotted in Fig 2. Since it is a different set of speakers, I will only use this calibration to compare against the calibration I had used previously to generate the plots in the first post. This original calibration file was from two data sets that are commonly found on the internet that over time I had merged together. (Only from 1000 Hz above is being validated and below 1000 Hz remains as is.) The results are graphed in Fig3 which shows the various calibration data. Over all, the validation matches the “internet calibration” quite well and I think this shows that the original calibration set is reasonable. Most of the differences are probably due to the fact that two different 303 speaker systems were used for measurements. However, there is a dip at ~4 kHz that the RS manual data shows that the internet calibration does not. Interestingly, the validation also has a large discrepancy at ~4 kHz here that might actually suggest a correction could be applied to the original calibration file? I think the conclusion that can be drawn here is that the raised tweeter response is not caused by a faulty calibration file. I will need to keep looking for the source of the raised tweeter response from the second post.
  2. Ar303 info.

    Well I finally managed to get through the process of building the response from the raw driver SPL data. To be clear about what is shown, a computer program is generating the transfer functions for the crossovers and applying that to the measured in cabinet SPL data shown in the previous post. The first attached image shows the schematic as entered into the program. I used the 303-a schematic as a basis which can be found in the library section of this website. A couple of things about the SPL data plots: 1)Overall the technique used to measure the data seems in general to be working. In particular when the crossover is applied to the SPL data for the woofer and the midrange something resembling the specified response is calculated. 2)The measured phase is consistent with the published phase and the computer program predicts that the tweeter needs to be hooked up with its positive lead attached to the negative terminal. (Drivers with reversed polarity are blue.) 3)The sore thumb here is the high frequency response. The tweeter SPL appears to be too high. Things to look into: 1)Revisit the microphone calibration file being used to measure the response. 2)Revisit the measurement conditions perhaps the assumptions that the conditions were the same for each driver was not correct. 3)Revisit the merge process between the near field and far field data, i.e. what determines what the best merge frequency should be and should priority be given to the far field or near field data? But even with the offset in the high frequency response I think one begins to get some sense of how the crossover interacts with each speaker to produce the total system response.
  3. Ar303 info.

    In addition to the measurments of the AR classic 18 I have been involved with, I have also been taking some measuremnts for my AR303s. As with the classic 18 the measuremsnts presented are for the raw drivers in the enclosure without crossover parts. (I thought I would post the results as a way to give back for all the great information I have received from this site.) Attached are the results. Here are a few notes on the setup. Its proably not ideal but works well enough for my purposes... The mike used was a radio shack analog sound meter that was calibrated to the radio shack spec in the manual. SPL data is relative only and was not calibrated to an absoulute level (same voltage used for each driver). All are measurements taken at 1.0 V rather than standard 2.83 V. (Did not want to risk tweeter...) Soundeasy MLS measurement system with realtek 2 channel sound card. The data is near field and far field data (1 meter) merged together to form the complete response.
  4. AR Classic 18 info.

    The investigation into these speakers continues... Since the last post I have been able to get measurements of the raw drivers in the enclosure without crossover parts. Attached are the results. Here are a few notes on the setup. Its proably not ideal but works well enough for my purposes... The mike used was a radio shack analog sound meter that was calibrated to the radio shack spec in the manual. SPL data is relative only and was not calibrated to an absoulute level. All are measurements taken at 1.0 V rather than standard 2.83 V. (Did not want to risk tweeter...) Soundeasy MLS measurement system with realtek 2 channel sound card. The data is near field and far field data (1 meter) merged together to form the complete response. The observable bump at around 1 kHz on the midrange is interesting and falls in line with my listening perceptions of these speakers when directly compared to the AR303. More soon as I import this data into the crossover tool to get full system response.
  5. AR Classic 18 info.

    Here is some more info on the crossover.I was able to obtain an RLC meter and measure values for those components that were unknown in the previous schematic. I also found some corrections and the attached image is corrected. I thought it would be of interest to list the measurements since degrading cap performance is a regular topic here. The 90's era caps used in this model seem to be holding up real well so far. Below is shown the specified value followed by the value that I measured. Specification Measured L0 3.40 mH 4.3 mH 1.3 Ω C2 50 µF 52.4 µF R17 6 Ω 6.5 Ω C3 100 µF 105 µF C12 100 µF 107 µF L15 0.405 mH 0.351 mH 0.705 Ω C13 24 µF 28.2 µF R14 10 Ω 9.6 Ω R11 0.5 Ω 0.69 Ω C10(T1) ? 8.3 µF L8 ? 0.322 mH 0.672 Ω T1 does indeed appear to be a capacitor as had been previously suggested.
  6. Driving AR-303a speakers

    I drive my 303s as right and left mains in a 5.1 setup powered by a sunfire signature 400 seven. (Theater Grand IV as pre amp) Never any problems. At typical volumes with music, movies conatining < 25-32 Hz content expect around 50-60 watts. I agree with the 100+ watt recomendation for the clipping reasons mentioned previously. The AR suggested range printed on the back of the speaker is from 50 watts min to 250 max.
  7. AR Classic 18 info.

    I just realized I never posted the tweeter part number. Its 1210148-0. Installation is pretty simple as can be seen. Brian, I am glad you enjoyed the post. It was fun to put together and cool to see first hand the stuff up until then I had only read in book come to life in front of me. Well all is back together now and ready for more years of listening.
  8. Holographic series original prices?

    I thought a document I received from AR in 7/92 might be of interest here. Regards. HoloPrice1.pdf HoloPrice2.pdf
  9. AR Classic 18 info.

    Oh I forgot, the caps seem fine so I have left them alone for now...
  10. AR Classic 18 info.

    I was able to trace out the crossover today. L3 I was not able to determine as the label is underneath the inductor. Also what is T1? You can see from the pictures the large rectanglar object marked only "T1 made in mexico". AR18Classic_Crossover.pdf
  11. AR-303 Woofer specs

    Oh forgot to mention, I used 44 L for the box volume for the Vas measurement. I got this number from the library section and did not remove any allowance for the woofer in the box?
  12. AR-303 Woofer specs

    Well I was able to measure one in recent days. I was hoping to compare this data to a series of posts that make reference to DUT1-7 where DUT1 was a 303 woofer but I could not find the complete data set. Anyway, here is what the WT3 had to say about this woofer. AR part number 2-11-0001-1 * This data was exported from the Dayton Audio WT3 Woofer Tester * Free Air * Manufacturer: AR * Model: 303 * Piston Diameter = 24.76 mm * f(s)= 24.22 Hz * R(e)= 2.67 Ohms * Z(max)= 25.59 Ohms * Q(ms)= 4.732 * Q(es)= 0.552 * Q(ts)= 0.494 * V(as)= 145.0 liters * L(e)= 1.13 mH I also did a series where i removed the stuffing put it back in and attached the crossover to show the effects of each. Enjoy.
  13. AR Classic 18 info.

    Now that I seem to have the process down for the measurements I decided to tackle the woofer measurements. Its up above but I will repeat the part number for the woofer is 1210152-5. Here are the parameters I was able to measure: Fs = 28.26 Hz Re= 3.65 Ohm Qms=2.81 Qes=0.55 Qts=0.459 Sd= 205.9 cm2 Vas = 68.0 L Xmax= ? (Anybody care to guess??) Le=0.61 I had to guess at the enclosure volume, I have decided on 30.4L, which I actually calculated from unibox by simulated the woofer in an empty box with no stuffing and matching this to the measured data. After a few iterations the numbers seemed to converge on 30.4 L for the box size with a Vas of 68 liters for the driver. This seems reasonable for a driver with this Fs as I compared to a couple of other make drivers with similar (but higher say 33 Hz Fs). If this isn’t appropriate way to measure these parameters, please let me know. (But, it’s going to be rather difficult to actually calculate the box volume due to all the odd angles of the cabinet construction.) I did however, to test the method out, use this same method to “guess” at the midrange enclosure which yielded a result of the correct volume 0.9 L, which I was able to calculate reasonably accurately. As before are attached the measured data and the simulation results from unibox. Curiously, or consistently the Fbs for the measured data are slightly lower than those predicted by Unibox. I thought maybe before this effect was caused by the small volume of the enclosure I was trying to simulate. Has anybody else seen this effect? Anyway also interesting in the measured data I believe you can see a standing wave resonance at around 180 Hz which disappears when the AR stuffing is added. I did not have enough fiberglass to try the cabinet stuffed with this material. However the Qts of the system with the AR stuffing is ~0.7 so I may not do this. That’s all for this week. I still need to get the tweeter part number trace the crossover and oh yes finally measure the caps (the original goal). Oh the fun of a hobby and the while you are at it effect…
  14. AR Classic 18 info.

    I had some time over the week to start playing around with the WT3 tester. I also was able to remove the 5.25 midrange from its enclosure. Attached are the photos. The part number of the midrange is 1210150-5. Also can be seen is the sub enclosure of the midrange unit. Once I saw its construction I realized I had an easily measureable volume and hence a pretty good case study for my first speaker to measure. So I hooked it up to the woofer tester. Here are the parameters I was able to measure: Fs = 49.80 Hz Re= 6.83 Ohm Qms=2.12 Qes=0.64 Qts=0.492 Sd= 66.5 cm2 Vas = 8.0 L Xmax= ? Is 2.0mm a reasonable estimate? Le=0.87 I then was able to repeat measurements under different box conditions, empty, stuffed with the AR stuffing and then stuffed with fiberglass. No surprises here there are other threads in the group that show the same trends fiberglass giving the most damping. The graph shows the measurements. Well now that I had the thiele-small parameters I wanted to simulate the system to see how it would compare to the measurements. I obtained the latest version of Unibox and setup a model for the AR midrange using the parameters that I measured above. I am using a volume of 0.9 L for the simulation model as this is as close as 0.93L that I calculated for the enclosure which is the enclosure volume of 1.2 L with allowances made for the volume taken by the speaker magnet and motor assembly. There is also a graph attached that show the results of the simulation. The stuffing was modeled by adjusting the Qa parameter in Unibox. The fiberglass is modeled with a value of 5 which corresponds to the heavy fill item in Unibox. The AR stuffing required a number of nine for the adsorption Qa. I not sure how to tell if the numbers are reasonable or not, obviously the simulation Fbs are skewed a little higher than the measured values and the Qtcs are a little lower however overall the attached results seemed to fit the best?
  15. AR Classic 18 info.

    The latest info for this week. I was able to obtain a Dayton Audio WT3. I have always been interested in speaker measurements and decided it was about time I had that capability on my own. I won't have much more time this weekend but it did arrive today so thought at the very least I should take it our of the box and measure something to see if it works. So I started with the speaker I did not take apart, so it is still 100% original never been opened etc. Here is the impedance and phase curves for this speaker. Not too bad the in box resoance seems to be at ~37 Hz right in line with the -3dB, 40 Hz spec. Should I expect the in-box resonance to be near or slightly below the -3dB point? What does the curve of the midrange indicate? The AR spec says the midranges are in their own sub-enclosure and have a -3dB point of 200 Hz. I am assuming the second peak in the impedance curve is for the midranges. The resonace from the curve would seem to be at ~250 Hz. How should this data be interpreted? Does having two parallel midranges effect the measurements? or is it reasonable to assume that the midranges can respond below the enclosure resonance? Also the nominal impedance does seem to be 4 Ohms as advertised by Ar with a couple of dips to 3.5 as I was speculating about above. Cheers.