Melon_Head Posted September 21, 2020 Share Posted September 21, 2020 No thread. I am new here. At some point I guess I should do a thread. Link to comment Share on other sites More sharing options...
dcathro Posted September 21, 2020 Author Share Posted September 21, 2020 Yes please! What drivers did you use? Link to comment Share on other sites More sharing options...
Melon_Head Posted September 21, 2020 Share Posted September 21, 2020 (edited) I used Full Range drivers from Audio Nirvana USA. I am extremely happy with them. I have some Seas FR drivers too, but I much prefer the Audio Nirvana Drivers When this bloody lock down is over, I guess I could bring some drivers around for you to compare etc. Edited September 21, 2020 by Melon_Head Link to comment Share on other sites More sharing options...
Melon_Head Posted September 21, 2020 Share Posted September 21, 2020 One thing you could try, to keep it nice and simple, I noticed Zu Audio run their FR without any upper Low pass filter but utilizing the natural high frequency roll off of the FR Driver and just using a first order high pass around 10kHz on the tweeter, seems to work well for them. Just ideas to try out and compare with what you already have. Link to comment Share on other sites More sharing options...
dcathro Posted September 21, 2020 Author Share Posted September 21, 2020 6 hours ago, Melon_Head said: I used Full Range drivers from Audio Nirvana USA. I am extremely happy with them. When this bloody lock down is over, I guess I could bring some drivers around for you to compare etc. Where are you located? I will definitely come round for a look and listen. Link to comment Share on other sites More sharing options...
dcathro Posted September 21, 2020 Author Share Posted September 21, 2020 6 hours ago, Melon_Head said: One thing you could try, to keep it nice and simple, I noticed Zu Audio run their FR without any upper Low pass filter but utilizing the natural high frequency roll off of the FR Driver and just using a first order high pass around 10kHz on the tweeter, seems to work well for them. Just ideas to try out and compare with what you already have. That is how I started off -running the full range with only a baffle peak correction and allowing the natural roll of at the top and the baffle termination at the bottom. However, it sounds better with the top and bottom pulled down a bit. Note that my filters are very mild, less than first order. Link to comment Share on other sites More sharing options...
Melon_Head Posted September 21, 2020 Share Posted September 21, 2020 Make sure you do plenty of AB listening tests. Sometimes going for what might seem like a near perfect response curve is sometimes not the most enjoyable result. I found trying to EQ the Seas driver with extra crossover components led to less transparency. So in the end took the EQ out. I guess it kind of depends where the issues are in the actual frequency range. Some areas are not so troublesome, other areas will sound terrible if not corrected. Link to comment Share on other sites More sharing options...
dcathro Posted September 21, 2020 Author Share Posted September 21, 2020 Nearly all my adjustments are done by listening. I measure and model to verify the result. Link to comment Share on other sites More sharing options...
Melon_Head Posted September 21, 2020 Share Posted September 21, 2020 Excellent. Link to comment Share on other sites More sharing options...
dcathro Posted November 27, 2020 Author Share Posted November 27, 2020 Have pretty much finished these, and am now just polishing. Here are the current graphs: 1 Link to comment Share on other sites More sharing options...
dcathro Posted November 27, 2020 Author Share Posted November 27, 2020 I am pretty pleased with the measured and simulated results as well as the subjective impression. The crossover points are 200hz and 7khz, which are not in the sensitive hearing zones. The drop in the high frequencies above 12khz is partially due to the measurements being taken off the tweeter axis - they were done on the Supravox axis. The phase angles are benign, and the impedance only drops a little below 4 ohms in the treble, meaning that the speakers are easy to drive. Some pictures of the crossover: 1 Link to comment Share on other sites More sharing options...
dcathro Posted June 23, 2021 Author Share Posted June 23, 2021 Time for an update. The crossover has changed significantly, with the tweeter now out o phase crossed over at 5k, the Supravox now with a 1st order low pass filter at 5K, and the midrange level dropped a bit. The improvement in performance is significant. Here is the new circuit and simulations: Here is a picture of the crossovers: A couple more pics of the speakers: 3 Link to comment Share on other sites More sharing options...
dcathro Posted August 30, 2021 Author Share Posted August 30, 2021 Since I have not been able to get out and visit or have friends over, I have gotten busy and done many of the little DIY projects that have been on the back burner. Firstly I have refined the speaker crossover further: There's not much difference in the measured response, but it sounds quite a bit better. I did some upgrades on my CD player which uses an Arcam Alpha as the transport, but has a NOS DAC board designed by Chris Bryant in the UK. The DAC board already had copper heatsinks and NX Black Gate decoupling caps round the 1541, but I upgrade the bridge diodes to ultrafasts, and change the DAC chip to a single crown. The Transport part was stock from the 90's and was struggling to play many discs, so it was time for a recap. Rather than modify my already working unit, I bought another Arcam Alpha, which I recapped, changed the 7805 heatsink to copper, added a clock module and the bridge diodes to ultrafast. The machine sounded better and now has no problem playing discs. I also can't get over how bright the display is. Next up was to replace the lids on the power supplies for the field coils. I bought some perforated perspex sheets from RS and measured up and cut the lids out. The supplies to the wideband Supravoxes are critical, so I wanted to try some mods to them. They are Chinese made regulated linear supplies, and I just changed the power supply diodes over to ultrafasts and changed the heatsinks over from aluminum to copper. I still have to figure out how to make some non metallic lids for these. Surprisingly the mods to these were very audible ans better dynamics and greater purity in the mids. Next up was a suggestion from another field coil user, Ralph Karsten from Atma-sphere amplifiers. Ralph said that he had found the gauge of the wire from the power supplies to the field coils to be critical, and the larger the better. The wires I had were pretty thin, so I made up some really beefy ones from Cat5 cables. Also with the bass supplies, I connected them to the back terminals of the supplies which provide higher current output. Final item was to connect up a dedicated earth to my isolation transformer which I have always had in the system, but with just the standard earth. Rather than putting copper poles in the back garden, I just connected a thick copper wire up to the hot water pipe under the kitchen sink. Now I have to think what else I can do for the rest of this lockdown. 3 Link to comment Share on other sites More sharing options...
Neo Posted August 30, 2021 Share Posted August 30, 2021 8 hours ago, dcathro said: Now I have to think what else I can do for the rest of this lockdown. Listen in bliss Neo Link to comment Share on other sites More sharing options...
dcathro Posted September 2, 2021 Author Share Posted September 2, 2021 On 31/08/2021 at 8:02 AM, Neo said: Listen in bliss Neo Thanks! Somehow, I think I will also need some projects as the bastards are going to keep us locked up until Christmas!!! Link to comment Share on other sites More sharing options...
dcathro Posted January 24 Author Share Posted January 24 Hard to believe that it has been over 2 years since I updated this. I ended up porting the bass boxes, in order to get more bass and efficiency. The woofer just didn't sound right sealed. I also had to reduce the box volume by about 20L to get the right bass response. I did this by adding some closed cell foam. The crossover has been modified quite extensively and the speakers sound a lot better. Interestingly the on axis frequency graphs have not changed a lot. Adding a slope on the midrange to counter the Supravox's rising upper mids has brought real dividends. The Crossover has gotten quite a bit more complicated and populated: Hopefully I won't be still working on these in 2 years time. 2 1 Link to comment Share on other sites More sharing options...
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