Wembley

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About Wembley

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  1. I have a basic colorimeter and CALMAN Enthusiast I used for my own projector, but unfortunately I'm in Perth which isn't a lot of use to you in the short term. If you can't find any other options locally, message me and I may consider posting the colorimeter if you still need it. Regards, Damian.
  2. I've recently played around with acoustic treatment for a room myself, although I went for full height corner absorbers. I'll get around to writing up the experience and measurements when I finish playing and my trials with conversion of some speakers to active (both multi-year projects as I'm easily distracted). I suggest the following link for modelling different absorption options: http://www.stanleyhallstudios.co.uk/pacalc/ You will probably need a reference like Bob Gold's absorption coefficient information: www.bobgolds.com/AbsorptionCoefficients.htm For myself, I found some 22kg/m3 "fluffy" style batts (R2.5HD Wall Batts for the record) that I used to fill each of my 4 corners in a 430x580 triangle shape. The different sizes for the edges were to accomodate the windows and doors in the room and as it happened made for good use of a standard size batt, rather than any acoustic magic. The general rule is the more depth the better for absorbing bass frequencies. With only 3 of 4 corners filled to date I have taken T60 from over 1000ms to under 250ms which was a major part of what I wanted to address. From my general reading, on the question of high density vs low density, it's a matter of what depth of absorption you intend to have. High density is better for lesser depths while if you can get over 600mm then less density becomes preferred (all depending on which source you read, but that was my ultimate determination). I went for the middle ground option, in a "superchunk" style arrangement. You're probably aware already but there is limited measured data out there. A search on "superchunk" bass traps will get you some measurements, but not a lot, and a significant amount of debate over the best way to make one and the best materials and whether commercial options are a better use of your time and money. I don't have them to hand, but if you want any measurements I've done with corner traps let me know via a message and I'll see what I've got. I'm not entirely sure how much use it'll be as i didn't do any comparitive measures between different styles of fibreglass, but treated vs untreated room. And none of the calculators I have found do modelling for corner traps, just absorbers mounted on walls from which you have to extrapolate results. I plan to mount a 100mm deep panel on my rear wall for more trapping, and measure for a panel at first reflection points in the future, but it may be a while. I believe that some others have been purchasing and experimenting with polyester based panels so you might get some better information from them on higher density panels. Regards, Damian.
  3. And just to throw some more confusion at the subject, I have completed a build using the Exodus Audio Tempest II driver and Oaudio 500W plate amp and found it to be a very good combination. I went for a smaller sealed enclusure (120L from memory) and it still is far from a small subwoofer. Dimensions were 450x550x650 as I remember them, and the ratio looks nice. I get a quite flat response in room, but I have a 4x5m room that seals relatively well so I get a nice match between sealed rolloff and room gain with some additional boost which is built into the HP filter on the Audio amp. The build is very loosely documented on this forum. Which ever route you choose I'm quite sure you'll enjoy the journey and get a very good result.
  4. Updating yet again. I don't know what was happening last time with bass response in my listening position. Might have been finger trouble and forgetting to turn back on one of the miniDSP channels. All fixed now in any respect. Still doing some other measures in my room, which I'll post at a later date. First impressions are that there is a nodal dip that I might want to address in the bass region, but I want to measure around the room rather than just the listening position before I play. This is a dip left after Audyssey XT32 room correction (I happen to like the effect the correction brings). I still intend to try some insulating batts on my walls to see if there is an audible effect too. Might be interesting as I have a side door into my theatre room between the listening position and the speakers. The big change I have made lately was a change in the input sensitivity of my hifimediy tripath amplifiers, matching much better now with the output of the miniDSP. Previously calibration had set the mains about 7-8 dB higher than they are now, where now they match the rest of the passive speakers. Hand soldering SMT resistors isn't something I'd recommend for novices though. This hasn't made a difference to the sound, but it has given me some hope I can actually drive the amps to provide full power. I've also found that late at night when the room is quietest that a very faint noise is audible from the tweeters. Plans for the next few weeks are to test a class A/B amplifier instead of teh tripath for at least the tweeter. On a different note, I did find an odd effect during my measurements with the treble dropping off in relative measured level from an almost flat frequency response measured at 1m down till the treble drops significantly as I drew away from the speaker and to the listening position. I don't know whether this implies issues with my measurements, whether treble is being absorbed, or whether small variations such as measuring below the top of the seat back made a difference when the Audyssey calibration was done at a level slightly higher. Given the very "hard" untreated and uncurtained nature of my room currently I suspect that the carpet might be absorbing high frequencies while I'm getting re-inforcement in bass and mid levels from room reflections. Time for room treatment and testing to turn speculation into knowledge. Hopefully time will present for these experiments over the holiday period. Currently doing all my measurements with both REW and HolmImpulse to see the differences and get some experience with the tools.
  5. Ok, some charts: First, the speakers with miniDSP and measured in room from 1m using REW. [ATTACH=CONFIG]26266[/ATTACH] This one looks pretty good, and the large dip at around 200Hz has been confirmed to be a measurement artifact by moving the microphone in slightly and seeing it change. Second, the same speaker measured at approximately listening position [ATTACH=CONFIG]26267[/ATTACH] That explains why I was lacking in bass while listening prior to the Audyssey calibration! I'm actually quite surprised at that, as I know there is a bit of a bass null in my listening position, but that graph implies somewhat more bass reduction than I expected. Note also that the microphone was only very roughly placed for the second measurement, but within 30cm or so of where I usually listen. I don't have a post-Audyssey graph for the listening position, but listening impressions are that the bass is restored and the sound is pretty good. I'm going to play with room treatments in the near future (standing insulation batts against walls) and see if it makes a discernable difference. I really don't know exactly what to expect from that though, so will be flying by the seat of my pants. As always, comments and critiques gladly welcome. I can certainly see that if I weren't using room correction through my AVR that the miniDSP would give me the power to adapt the speaker to suit my room. In the short term, I'm happy with the automated approach, and will debate the virtues of IIR filters vs FIR filters later. I actually have measurements in both HolmImpulse and REW, but using the REW graphs here as I'm more familiar with the tool, and I wanted to show the room responses.
  6. Time for an update on how things are progressing. I have finished putting together the amplifier and DSP combination, using the miniDSP and hifimediy T2 TK2050 tripath amplifiers, powered by a Meanwell S-350-27 SMPS and a LM7824 to power the DSP. It's all very industrial for now, just open on risers on a piece of aluminium sheet. It does fit nicely inside the slot port at the rear of the speakers though, so with some minor disturbance to airflow I have a place to hide them away :-) I elected to use cross-overs at 180Hz and 2kHz for initial testing. This was largely based on distortion data rather than maximising power handling at this stage. As it's on a 4x5m room, power is sufficient for now. I am running them through a Denon 4311 AVR, though testing was done using Holm Impulse and REW using a laptop and Behringer microphone. From measurements, the frequency response is very much flatter than before. Also, I have entirely filtered the breakup nodes of the SB Acoustic mid-range drivers on my system. I have done some elementary time alignment, but the initial values are based on guestimates of distance for now, rather than exact measurements. I will be following Paul's methodology to do some more exact time alignment later. Measuring absolute phase proved to be a little elusive initially using Holm Impulse (or rather, measuring the effects of delay, since Holm Impulse is a frequency - amplitude tool, rather than a time - phase tool). So the effects of time delay when measuring individual drivers cannot be measured, rather the effect on the total speaker response can be observed. The correct values are determined by calculation if you're like me and using only basic tools. Initial listening tests showed a changed sounds from the speakers. Changed doesn't necessarily equate to better, and I'm busy listening for how the active conversion has affected soundstage and imaging, clarity of vocals and music reproduction, etc. I have listened briefly with no room EQ applied, and this highlighted a decrease in the preceived bass response and an increase in treble. However, I am used to listening to these speakers after Audyssey calibration using my old Denon 1909 AVR. After calibration using the Denon 4311 the sound changed to include the "missing" bass response and reduce a touch of the treble emphasis. Imaging is good, though without the depth I have heard from at least one other speaker set I auditioned. Best impressions are that I have lost nothing in the imaging stakes, and perhaps gained a little. There is a "hum" or faint sound of white noise from the tweeter which is only audible from with about 300-400mm of the driver when the room is very quiet. Not at all audible from the listening position and has been reported in other places when using similar amps. I may try my older 1909 as a replacement for the tripath and see how I like the sound change. I'm testing both new crossovers and new amplifiers here, so two variables in these listening tests. Of note was that the gain of the active speakers was significantly lower than the passive crossover and all the other speakers in the 5.1 setup I have. I attribute this to the various input sensitivities of the DSP and tripath amp. In particular it appears that the particular hifimediy T2 amplifier I use have a full scale input of 1.5V while the full scale output of the miniDSP is less than 1V. The recommendation for the T2 is to change a pair of resistors (R3, R5) from 20kOhm to 47kOhm to increase the input sensitivity. Since these and surface mount resistors I'll tread carefully before I get around to making that modification on my boards. In the mean time, Audyssey calibration has set the speaker gains and adjusted for sensitivities, though I am aware that I won't get full power out of the amplifiers as they are. The big change to date (a day or two only) is that I was able to sit and listen for hours and feel no listening fatigue as I was listening to the changes and enjoying the different sound. It's amazing how changing a crossover can emphasize different parts of a song and make it sound different in detail to how you've heard a song before. In short, I'm happy with the changes, though there is a small amount of tweaking left to do, and the possibility of moving on to the centre speaker to change it from passive to active as well. On a different note, I received a call from Edward who offered to talk about the passive crossovers for my speakers and see if some improvement couldn't be had there too. I suspect mine were on of, if not the, first set to use the SB Acoustics midrange, and its characteristics weren't so well understood by him at the time. I will also point out that the change was my choice, and one I'd probably make again. Measurements and charts to follow in a later posting, but may be a little while.
  7. I'm also in the middle of playing with the miniDSP and various measuring tools. I'm using both REW and HOLM impulse to make measurements and seeing what differences I find, and how gating affects the results. I am making a different design decision in that I'm trying to design the speaker to be flat in an open environment and then use my AVR to try and correct for room effects later. That allows me to measure the effect that the room is having, and to move the speakers around a little prior to doing final adjustments. If I think that the final measurements (particularly the subwoofer I expect) aren't to my taste, I can then either turn off the Audyssey correction or use it and a combination of further correction with the miniDSP. Flexibility is a wonderful thing. A common flat response I can apply to both speakers as a baseline is worth the extra effort I think, and means I can always go back to it later than going straight to a final in-room eq solution in my case. Very much a matter of taste I'd say though.
  8. I have got hold of a copy of holm impulse, and will try my luck with it soon. I've also put in an order for a new AVR with pre-outs this time. As for 5.1 vs 5.2, you're correct Paul in regards to how tracks are encoded, but from a decoder output perspective, some new AVRs for instance have the ability to independently output 2 subwoofer signals, each of which has different EQ applied, technically making the audio signals different and earning the .2 designation. I think last I saw a 5.1/7.1 signal was recoded to up to an 11.2 output using the mysteries of audio voodoo. :-) I think there's a bit of a move back to treating multiple subwoofers as a single unit for EQ purposes in any case. I will be borrowing a tripod in the near future, and will take some measurements once I do. Time is always at a premium though, so this was may not happen as fast as I'd like. I may even get into polar plots as gainphile suggests, if I get really enthusiastic.
  9. This is what I love about SNA. Plenty of people willing to increase my knowledge of audio and assist in projects. Its especially nice that manufacturers such as Aslan are happy to help out small fry such as myself in a field they retail in. Not to mention the great advice from everyone else. As for my own little project, I have started with a simple division of crossovers at roughly a decade apart. So for now the crossovers are at 200Hz and 2kHz, each being a 4th order LR filter. Nice simple stuff for me to start before I listen and then refine. I have a shelf filter to raise the response of the Vifa DX25 tweeter above 10kHz and a PEQ filter to raise the slight frequency drop in the SB Acoustics SB15NRXC30-8 midrange around 1.5kHz. The bass driver is a Peerless SLS830667. Intent is to take the speaker outdoors and do some measurements using ground plane and near field measurements. I may also try Paul's suggestion of Holm Impulse to see if I can have some success there. If I am happy after all my fiddling and measurement that the speakers actually sound better than they started, then I may move on to consider building a small set of 2 ways and match those with my Tempest X2 subwoofer. Perhaps even build a second subwoofer and run those in stereo and have some 2 or 2.5 ways sitting above. I haven't figured out if I can adapt that to a 3 way design using those two sets of components and still have all the ability to equalize the subwoofer section and have it perform as a HT subwoofer should. Essentially a 5.0 system with genuine full-range mains versus a 5.2 system with mains crossed to the subwoofers via an AVR. I'm thinking the second is easier for me to contemplate as it allows a basic 5.1 system and later a move to 5.2 if I feel the need (which I may not). I like music, but its still a minority of my system use at present, and likely to remain so in the near term. And the problem with DIY is that I don't have the experience to know if the end result will be better than the same money into a commercial system, though the fun of designing and tuning makes the project worthwhile for its own sake. First things first though, measuring what I have now and seeing what falls out after my changes.
  10. I am just using REW for measurements. Nothing too exciting there really, but between the information on the SB Acoustic's site and Zaph's measurements there is a fair amount of information for me to work with. My own measurements of the SB Acoustics midrange match pretty well with published figures and show a large increase in the frequency response at around 4.5kHz. In a passive filter I could have added a notch filter but with the DSP I have the chance to improve the response as well as play with time alignment and other filters. Taking care of effects like baffle step conpensation in software are a bonus. I need to take my speaker out of the room its in currently to build a baseline relatively flat frequency response curve, and then I can take them back into the room and make any further adjustments. The final test will come with testing using both speakers, but since my current AVR doesn't have pre-outs, I'll have to use a PC or CD player as the source initially, and forego things like room compensation.
  11. I have had a set of Ascension Summoner speakers which although I'm generally happy with, I believe could do with a little improvement. I get a touch of listening fatigue in some instances, and looking at the graphs of the response plots it appears that the 2nd order filtering on the non-standard SB Acoustics midrange may be allowing the cone's breakup issues at around 4.5kHz to be heard. So I have decided to have a play with the miniDSP and active amplification of the speaker to see if I can improve it's response and to generally learn more about my own speakers and acoustic responses in general. To that end I have bought a couple of miniDSP (V1) and some small tri-path (class D) amplifiers along with an appropriate SMPS to drive them. Not the highest of audio but enough for me to learn some useful lessons and try some variations without breaking the bank. Alterations, such as using a class A/B amp for the tweeter may come later, if tests show an improvement. I have to know what I'm listening for to know whether to spend the money first. Some things I've learned about the Summoners from my experimentation: 1. The speaker is actually what I'd call a standard slot-ported design rather than a transmission line. It has a large moderately stuffed chamber behind the woofer and a folder slot port, rather than the very small chamber I'd expect to see in a true transmission line design. 2. The cross-over is a series design using no high cost components. Some, like the snubber used instead of seperate resistors and capacitors made it hard to draw out the circuit and surprised me a little. Seems to have 2nd order filters. 3. I'm much more comfortable in the digital domain than trying to modify or design passive cross-overs. I did play but I don't have the time or experience I'd really need to redesign a good passive filter. Note that I still think the speakers are good value for money, but can be improved. The (relative) low cost means I'm not afraid to experiment and to learn more about active speaker systems. I'm not sure if this will lead to restoring the current speakers to their original passive design and trying to go active with a new or second hand set of speakers, or whether I will like the results enough to stay with the active summoners. Money might also drive that decision. There are a nice pair of ZD5 speakers on the for sale section I note, but apart from cost it seems a shame to look at replacing a cross-over of such good reputation in the DIY world. Comments, advice and support all welcome. Pictures and graphs to follow when I get enough time to post more. Damian.
  12. Very nice work there Gainphile. Nice to know that the job isn't too tricky. I'm also very impressed with the measured in-room response. I'd be interested to know if that was measured with a close microphone or from the listening position. My room doesn't have any treatments yet, so never get anything that nice. Treatments will be next on the cards after I play with my speakers. Now to see if the listening impressions match the improvement in the FR charts. Also be curious if a mix of Class D and gainclone (driving woofer and tweeter respectively) is different again, assuming its a test you care to perform.
  13. So tell us how they sound! I'm actually about to embark on a similar experiment myself very soon. Will be modifying a set of speakers with the miniDSP and a similar class D chipamp. So very interested to hear how easy it all is/was, and how you like the listening experience at the end. Seems my decision not to buy an AVR with pre-outs might be one I live to regret though. I'll post in a seperate thread once I start on my own experiment, as see how the results compare to your own.
  14. Nick, Looks like a fair design to me. I'll throw in a few observations of my own though, given I have recently finished a sealed version using the same components (I had a thread on it). The Oaudio 500W plate amplifier has a peaking HPF, described in their documentation. That means the low end isn't flat as you'd expect, and that with the additional gain you can expect higher current draw for those boosted low frequencies. 19mm MDF seems a good choice, and the bracing is similar to what I went with. I suggest that some stuffing wouldn't go astray either. Attached are a couple of pictures of the response with the Oaudio amplifier as modelled in WinISD. The first is a model of a 20Hz HPF on the Oaudio amp, and the second a 16Hz HPF. Both using a 200L slotted port design. Note also I've reduced the power so that the peak power draw is 500W. In reality this would only apply if a pure sine wave of 16-20Hz was applied, in any real world situation expect a couple of extra dB output. [ATTACH=CONFIG]23299[/ATTACH] [ATTACH=CONFIG]23298[/ATTACH] In general, for a larger room than mine the ported design looks great. In my smaller room (5x4m) with room gain the sealed design is one I'm very happy with. Looking at my models, I'd suggest a 20Hz HPF setting to control the cone excursion.
  15. Paul's comments above are on the money for speaker blending. I'm a bit of a heathen however and currently use an AVR to do the work of crossing over from the various speakers to the subwoofer. That means I can ignore the rolloff of the inbuild LPF on the subwoofer amp and let the AVR control the process. For those purists with dedicated stereo amplifiers there's a lot more to worry about, as described above. I'm a few years and a lotto win away from that stage myself. Also don't forget that the Oaudio amplifier has gain around the high pass filter (HPF), with the level increasing as the frequency decreases. You'll probably want to match your HPF setting to your chosen port frequency. Ultimately, both are good amplifiers. Your biggest choices (in my opinion) are that of box size and port tuning frequency but it seems you've already made those choices. If you do go DIY make sure you post the results, success is always best shared.