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Post by Deleted on May 29, 2012 22:37:02 GMT
Hi Dave I imagine that some other members may be interested in seeing what you have done, including an inside photo or circuit details. Those ebay tweeters seem worth having a play with at the asking price, especially if we can get further confirmation that it is all worthwhile. Regards Alex
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Post by Deleted on May 29, 2012 22:49:01 GMT
OH YES! Show us everything. Firstly we're interested and secondly pretty pictures always make a better read.
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Post by Deleted on May 31, 2012 23:13:22 GMT
A Correction. Barry Diament has asked that I correct my statement about him listening only using iTunes.
iTunes is what Barry chooses to use as his *server* application, although he has other apps including Amarra, Fidelia and Decibel. Barry prefers the iTunes interface, but has not heard the differences when using the other programs that others claim is there. Barry's main listening is via the software he uses in his work (soundBlade, Peak Pro XT and Wave Editor to name a few but not all). My sincere apologies to Barry for my previous errors. Alex
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mrarroyo
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Post by mrarroyo on Jun 1, 2012 10:37:00 GMT
Alex, don't let it happen again! I too find the iTunes interface very comfortable and thus why I use it. Specially in light of the portable Apple products both SWMBO and I use.
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Post by Deleted on Jun 1, 2012 10:55:44 GMT
And here was me thinking that you were just a cheapskate ! ;D Despite that though, you have been able to hear those "impossible"differences, back when the differences were far more subtle.
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mrarroyo
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Post by mrarroyo on Jun 2, 2012 11:21:05 GMT
The differences are there for those who listen.
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Post by Deleted on Jun 4, 2012 13:54:09 GMT
Hi Guys, At the request of cj and SandyK I offer the pics below of my super tweeter additions for your delectation . Sorry if they are not quite as crystal clear as you would like but my eyesight and the auto focus on my camera may not be what they once were . i664.photobucket.com/albums/vv4/DaveAndSue/DSCF0052.jpg[/IMG]The L-Pads and crossovers were provided by Reid Malenfant (Mark) on AoS and the bits were put together by Sean of Custom HiFi Cables. I did the butchery of the plastic Maplin boxes, housed everything and I actually soldered the speaker cable post connections .
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Post by Deleted on Jun 4, 2012 14:13:43 GMT
Two further pics that the last post insisted on not accepting: Dave.
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Post by Deleted on Jun 4, 2012 23:14:38 GMT
Dave Very nice work ! Do you know the crossover frequency,or the L and C values ? The chokes don't appear to have much inductance. Regards Alex
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Post by Deleted on Jun 5, 2012 5:47:08 GMT
Hi Dave,
I assume you use it upright instead of lying down. Otherwise the 'beam' would be be very narrow in the horizontal plane.
Here is a funny experiment,
have the wife (without you knowing) unplug and plug in one of the cables of both tweeters once every few days or so and try to see if you can detect which days it is on or off (no peaking !)
This will be more objective than when knowing when it is plugged in or not.
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Post by Deleted on Jun 5, 2012 6:24:56 GMT
Dave Better still do a series of at least 10 sessions of DBTs with and without the " Super Tweeters" using Foobar playing 120kBs MP3s. Document the results and send them to Frans for analysis. ;D Dave, the only person that you need to convince here is yourself,and you appear to have done that already. However, you could try simply disconnecting them for a week and see if you miss them or not.I am tipping that you will find something lacking, although you may not be immediately aware of it. Regards Alex
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Post by Deleted on Jun 5, 2012 9:14:10 GMT
Hi Dave, I assume you use it upright instead of lying down. Otherwise the 'beam' would be be very narrow in the horizontal plane. Hi Frans, You should know me by now, I know nothing . No, they have been used in the horizontal position because I thought they looked better in that position, their height being equal to the speakers' width . I have not really tried them in the vertical position but I will now and see/hear what difference it makes. Whilst I have your and Alex's attention can I ask a technical question of you but, to be fair, I have also asked the same question of Mark who did the chokes and crossovers etc.? If I turn up the volume on the system the RH chanel amp (Mini-T with a 2020 op-amp) clicks once and cuts out. Switching it off and back on again fixes the problem temporarily until the next time but turning the volume down a touch fixes it permanently. I am told it is probably impedance that is causing the problem - any ideas how I could reduce or remove the problem? TIA, Dave.
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Post by Deleted on Jun 5, 2012 9:29:00 GMT
Dave, how does the box sit on the speaker? Is there anything underneath to dampen vibrations from the main enclosure?
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Post by Deleted on Jun 5, 2012 9:52:20 GMT
Dave I would be inclined to mount it horizontally, with it somehow angled down towards ear level,if it is higher than the seated position, and angled a little towards the seating position. I would also fit it with rubber feet.If you use larger rubber feet at the rear to angle it down a bit, you may need to fit some weight in the rear of the case to keep it stable. As for the digital amp, I know very little about them other than I would never personally use one on principle, and due in part to the problems they can cause with low level gear via the mains. Having said that, how hot is it getting internally ? Alex
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Post by Deleted on Jun 5, 2012 11:17:50 GMT
Hi Guys, I don't seem to be able to help being divisive but it's not intentional, honest . I'm talking about horizontal vs vertical positioning of the super tweeters. I'll try 'em both ways and let you know if I can perceive any difference. Meanwhile, to answer your questions: - Ian, if you look very carefully at the first pic above you can just about see one piece of blu-tac and slightly to the right even less of another piece. Because of the mould release taper (draft in technical terms ) the blu-tac serves two purposes - one. to level them up approximately and two, to hold them tighter for when I move them for a serious listening session. Alex, at the moment they have blu-tac at the front but they rest on the speaker cabinet at the rear. I am thinking of disconnecting them but I think they might be too light for rubber or even sorbothane to effectively do this. I can feel the main speaker cabinet vibrating when in use and that can also be felt on the tweeter casing. I have a couple of thin pieces of very light and open black plastic foam that are just about the right size that I will try underneath them and see if that helps. The Mini-Ts are fed from a linear PSU through a JLH RE and the PSU in turn is fed from a Belkin PF40 mains filter/conditioner whatsit. I have added a heavy gauge 'extra' earth from the wall socket that feeds the PF40 and that is firmly jubilee clamped to the incoming copper water main. Without any music playing, even with everything turned up to ridiculously high volume settings, the system is totally silent, no hums, no nowt . The Mini-Ts do not get at all hot in operation. Hope that helps you to help me but if you have any questions or comments, feel free. TIA, Dave.
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Post by Deleted on Jun 5, 2012 14:36:35 GMT
OK Dave, so it's fixed to the cabinet.
The box with the tweeter may resonate at a certain frequency being hollow mostly and I wondered whether it may need padding in there to dampen it down. Or even the old Pinkie bitumen trick on the inside to make sure that it doesn't go off at certain frequencies.
The reason I mention it is that way back, I made some speakers with the tweeters in a separate enclosure and after quite a long time, I started to feel that there was a strange resonance going on but not all of the time. It turned out that the enclosure for the tweeter was resonating when the speaker played certain notes and also notes that were harmonically related. So it didn't happen all of the time; only in certain keys!!!
I ended up putting the tweeters in heavier enclosures and padding them. I know this sounds mad, but I also played around with where I put them and in the end, bolted them to the side of the enclose on an adjustable bracket that could be tightened down hard. That way, I could point them at the listening position and they were very close to the main driver in the cabinet so that imaging was improved imo.
I think Tannoy eventually (or some other maker - Kef?) developed a speaker with the tweeter right in the middle of the main speaker cone for the same reasons. They felt that it helped imaging. Very odd to look at since it had just one cone and the tweeter was the bulls eye!!!
It's quite amazing how playing around with the position of the tweeter can affect what you hear at the listening position!! Even backwards and forwards so that the drivers line up with the main ones. (Or else you could hear the tweeters before the main speakers or vice versa!! - although it's hard to detect but affects imaging quite a bit)
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Post by Deleted on Jun 5, 2012 17:36:05 GMT
The T2020 starts to roll off in the audible band already (18kHz - 0.5dB !) What I found was that when something was rolled off at 12dB/oct and the filter was set to have -0.5dB off at 20 khz the phase shifts and frequency roll off was not noticeable as roll-off but as 'fuller bodied' sound. The JK acoustics CD filter, stock tube thingies and MANY MANY DAC's and amplifiers make 'use' of this phenomenon.
The TA2020 is rolled off 12dB/oct (output filter) so this also accounts for fuller sound, but t.b.h. IMO completely nullifies the usefullness of the added super tweeter as this starts where the amp 'stops' and the phase shifts that is talked about in the 'perception above 20kHz article clearly states there should not be any phase shifts in this region. The amp has a filter on it's output that is similar to a low pass filter (high-cutoff filter) in a speaker.
Anyway about the problems. These could be in the power supply, JLH (current limiter if present), amp and load.
If you have 2 amps and only 1 acts up exchange the power supplies (incl JLH). If the problem shifts channel check out PS/JLH. When the problem remains change L and R speaker (or amp) and see if the problem shifts channel/amp If it is always the same speaker disconnect the tweeter and check again.
let me know what you find.
If the tweeter was 'aimed' at the listening position horizontal or vertical doesn't matter. When aimed 'in the room' vertical (as they always are) would be best because the tweeter has a better spread to L and R and considerable worse in the up and down plane, so in essence a band tweeter/planar speaker has lousy spread upwards and downwards but a good spread of sound L and R. The higher the frequency the worse the effect.
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Post by Deleted on Jun 5, 2012 21:22:45 GMT
Dave If you aren't using the Current Limiter section of the JLH, then it will be straight through. It would take a complete JLH failure to drag down the PSU rail, and it would stay in that situation. Alex
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Post by Deleted on Jun 5, 2012 21:33:40 GMT
Alex, I'm 99% certain that I had the current limiter removed or bypassed on the JLH RE(s) that feed(s) the Mini-Ts but I will need to confirm that. Because of the unique (being polite here ) layout of my kit I may not be able to get round to this for a day or two. Frans, I have swapped over the power supplies to the Mini-Ts but again, (Jubilee celebrations and family visits) again it might be a day or so before I can try it out. I'll keep you both posted . Cheers, Dave.
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Post by Deleted on Jun 5, 2012 22:00:23 GMT
You are going to visit Phil in hospital ?
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Post by Deleted on Jun 5, 2012 22:43:52 GMT
Nah, our schoolteacher daughter has spent the long weekend with us and both ladies gang up on me so, being a peaceful sort of guy I take the easy way out and go with the flow - in other words I do what I'm told and they tell me what is going to be on the telly - and no music because neither of them share my tastes . Phil will get along fine without my company ;D . And so to bed , G'night cobber, Dave.
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Post by Deleted on Jun 6, 2012 9:28:07 GMT
Dave Very nice work ! Do you know the crossover frequency,or the L and C values ? The chokes don't appear to have much inductance. Regards Alex Alex, I asked Mark the above questions and here is his response: - "Crossover frequency is approximately 16KHz. Assuming the capacitors I sent to your builder were changed for the same value they should be 1uf, 1 micro Farad. The inductors are approximately 95uh or 95 micro Henry." Sean has advised about the capacitors he swapped: "The caps I used were 1.00uF, matched within 2% i think. They're Solen metallised polyprop caps to 400V if anyone asks - can't remember the model as it's 2 am and i've had a few drinks but can confirm if anyone is mega-interested " Hopefully that will enable you to fully understand what I've got. Cheers, Dave. EDIT, One of the guys on AoS, Ali Tait, has confirmed similar benefits were heard at one of our bake-offs' - see here: - theartofsound.net/forum/showthread.php?p=333393#post333393 post no. 7. Dave.
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Post by Deleted on Jun 6, 2012 9:55:58 GMT
Dave Thanks for the clarification about the filters. When mine are returned, I also intend to use large Jiffy boxes, and angle them down slightly as my DCM QED 1A are about 1M tall. My ribbon tweeters are supposed to go to 40kHz, and I will crossover at closer to 18kHZ where my existing Philips ADO160 T8 start to droop. A question though . Pussyman ? Kind Regards Alex
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Post by Deleted on Jun 6, 2012 10:16:08 GMT
Dave A question though . Pussyman ? Kind Regards Alex Ah, Pussyman - that dates from a period a few months ago when the guys on AoS were changing their 'description'. We have 3 Persian house cats - I haven't got round to changing it. Dave.
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Post by Deleted on Jun 6, 2012 10:58:06 GMT
16kHz Butterworth type filter (Q= around 0.7) and explains why you hear a difference when switching it on and off (at least to me) The 774 tweeter reaches to 20khz (-3dB) and together with the relatively low crossover, which causes phase shifts and combfilter effects in the audible band probably right upto the point where you can still detect highs (I figure 13 to 15kHz). Ofcourse if it enhances the experience I am all for it. 'Proof' you can detect subsonics it is not I am afraid... it is proof you can hear 2 different tweeters with a certain distance that both squeek in the same part of the spectrum it is. Walpurgis is using/advising 0.1 or 0.2uF (6dB/oct) must be kidding. this constitutes a 200kHz (and 100kHz for 0.2uF) high pass filter at 20kHz this filter would be down -20dB It's great though he can hear that.
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