Pundit
Post by papahemi on Jan 21, 2017 15:00:06 GMT 12
I have a soft spot for fullrange drivers, but do note their limitations in playing louder, more complex music. I have a soft spot for vintage Coral drivers and have a fair few of their Kabuki style speakers, as well as a pair of 4A-70 fullrangers. So why not use two pair of woofers from the BX1001 to make a pair of slot loaded w-frame subs - like this (image borrowed from www.hifizine.com/2012/12/subwoofer-origami/):  As always though the $ demands that it stays in the pocket and not squandered frivolously, so the cabinet material had to be made from what was on hand, namely a cabinet that had housed a Tannoy Monitor Silver that I scored a few years back (some may remember the thread from Audioenz). I liked the idea of repurposing the old cabinet for various reasons - the quality of the old ply, the nominal cost, the environment and the attractiveness of the timber - all misguided of course, the ply was of various thicknesses, had many voids, took hours to cut up into strips, heavily polluted our deck and yard with dust and the outsides of the cabinet were stained brown that continues to obscure any beauty in the grain. Nevertheless I persisted. Some pics:  This is the donor cabinet, put through my table saw to make the strips that stack together to form the cabinet.   image uploadProgress pics - a few months ago - this is a long term project.   Cabinets nearing completion - getting many coats of Tung oil in the hope it will hide the many flaws in my workmanship.  4 x Coral 10L-17A, cones treated with damar, frames painted with a slightly rubbery rust preventative (may provide some dampening)   post imagesPrototyping last week, using MiniDSP to x-over at 200hz, sounding OK, yet to implement any equalisation or time delay. Long post - time for a rest and a beer.
We are what we pretend to be, so we must be careful about what we pretend to be.
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Pundit
Post by Gryffles on Jan 21, 2017 16:25:06 GMT 12
Look good to me.
What was the rust preventative you used?
Only asking as I plan an OB project myself in the near future
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Pundit
Post by papahemi on Jan 21, 2017 17:06:25 GMT 12
Kia ora Gryffles, the paint is Gold-X Rust Kill, oil-based stuff. It is great, goes on stays on. I note that you and I share a birthday, heres to the eighth of the eighth.
We are what we pretend to be, so we must be careful about what we pretend to be.
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Fast Coral Jan 22, 2017 11:06:45 GMT 12
- Edited Jan 22, 2017 11:08:03 GMT 12 by Owen Y
Post by Owen Y on Jan 22, 2017 11:06:45 GMT 12
I like the stacked ply - is that what you did papahemi? I remember reading Pass talking about his slot-loaded woofers from his days at ESS/AMT.
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Pundit
Post by papahemi on Jan 22, 2017 11:42:03 GMT 12
Yes Owen, I cut the ply into 20mm strips and stacked the layers up (or down as I started from the top). A good idea I think, but my execution was not too hot. The last layer of tung oil is drying at the moment, and they look great as long as you don't look too closely. I will post some more pics later.
We are what we pretend to be, so we must be careful about what we pretend to be.
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Pundit
Post by papahemi on Jan 22, 2017 12:07:54 GMT 12
 
We are what we pretend to be, so we must be careful about what we pretend to be.
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Pundit
Post by papahemi on Jan 22, 2017 17:03:45 GMT 12
Pushing on, wiring, drivers and a pic of how it all works  
We are what we pretend to be, so we must be careful about what we pretend to be.
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Post by Owen Y on Jan 23, 2017 4:57:21 GMT 12
Papa - not sure what imped the Corals are, but do you think connecting the woofers in series (rather than parallel) might usefully offer more LF headroom? Anyway you can experiment.
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Pundit
Post by papahemi on Apr 1, 2017 8:50:57 GMT 12
Two and a bit months on - a long tweaking and settling in period and here are my conclusions to date: Time delay on the 4a-70 is essential, currently have 0.5ms to roughly align 4a-70 voice coil over woofer. The results are magnificent playing from Macbook through usb to minidsp - clarity, detail soundstage etc. never heard digital sound so good, then again I never put much effort into the digital side. Vinyl playback is not so good, a loss of presence. I made some measurements using REW and as far as I can ascertain (I am newbie to this, I primarily measure with my ears) fr is flat (I have lost the graphs but will put them up when I redo this. I am thinking that the adc/dac process in minidsp is the cause of the above. In digital mode there is only the dac in play and the results are more than adequate. With analogue in both conversions are in play -with the resulting loss of quality in the vinyl playback. Solutions? Most likely a passive crossover to eliminate the need for adc/dac - that will cost! Setting in dsp is LR 48db/octave - then time delay would have to be initiated physically. An analogue only system and a digital system - Don't know that SWMBO will buy that one - yet I remain astounded with what I can get away with. Pluses - The power amp section of my Sansui AU555 is dead silent, can't say the same for the pre-amp section. The concept is good - I just need to sort out execution for minimal $$. Any thoughts?
We are what we pretend to be, so we must be careful about what we pretend to be.
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Pundit
Post by papahemi on Apr 7, 2017 17:51:20 GMT 12
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Post by Owen Y on Apr 8, 2017 19:22:54 GMT 12
papahemi - the answer to your Q is - no, but.... Is your system schematic still pretty much as above diagram? What xover freq/s?
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Pundit
Post by papahemi on Apr 9, 2017 7:47:30 GMT 12
Yes Owen, pretty much as above. XO at 200hz.
We are what we pretend to be, so we must be careful about what we pretend to be.
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Post by Owen Y on Apr 9, 2017 15:56:17 GMT 12
So now you want to replace the minidsp with a passive xover?
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Pundit
Post by papahemi on Apr 9, 2017 18:01:05 GMT 12
That's my thinking - The minidsp just sucks too much of the analogue goodness out - works well for finding xo point, but then...
We are what we pretend to be, so we must be careful about what we pretend to be.
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Post by Owen Y on Apr 9, 2017 18:17:30 GMT 12
I'm no xover expert (something I had hoped to avoid messing with in my audio lifetime  ) - but I am thinking.... - hi-pass to the mid-HF amp (ie a series capacitor for 6dB/oct, or cap/coil for 12dB/oct). - lo-pass to bass amp (big ass coil, unless the bass has filter built in). ie Similar to regular lspkr xover except that signal voltages are much lower.
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Pundit
Post by papahemi on Apr 10, 2017 6:56:21 GMT 12
That was also my thinking Owen, but then you have to factor in the higher impedance of the power amp cf driver.
We are what we pretend to be, so we must be careful about what we pretend to be.
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Fast Coral Apr 10, 2017 10:24:59 GMT 12
- Edited Apr 10, 2017 10:25:17 GMT 12 by Owen Y
Post by Owen Y on Apr 10, 2017 10:24:59 GMT 12
OK....the amp input might be 50-100k ohms (?)... Theoretically 0.01 - 0.015uF will give you a RC hi-pass -3dB cutoff at ~200Hz.
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Pundit
Post by papahemi on Apr 10, 2017 16:36:18 GMT 12
yeah, Ive been looking for some circuits, I feel I need to study this a bit more, I am using 4th order on the DSP, but may not need this degree. Will try lower order xo with dsp.
We are what we pretend to be, so we must be careful about what we pretend to be.
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Post by Owen Y on Apr 10, 2017 19:50:55 GMT 12
For a simple 2-way, keep it simple with 1st order & reduce the resultant xover dip by implementing a 'Solen Split' config - reverse phase tweeter etc. I like to avoid complex xovers.
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Pundit
Post by papahemi on Apr 11, 2017 6:58:37 GMT 12
For a simple 2-way, keep it simple with 1st order & reduce the resultant xover dip by implementing a 'Solen Split' config - reverse phase tweeter etc. I like to avoid complex xovers. Me too, but must use something for this. It appears I have an even bigger dislike for adc/dac.
We are what we pretend to be, so we must be careful about what we pretend to be.
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) - but I am thinking....