Digital Active Speakers - My experience to date

[Bencat]

Hello to All

I am new to this forum and as requested I put a welcome note . One of your fellow AOS members suggested it might be worth putting a thread on detailing some of things I have recently completed turning some passive units in to Active speakers. Not sure if too many will be interested but will detail a few things here ad see what the response is. If nothing else it will give a starting point for a little discussion on this area.

Up to June or so last year I had always been a passive buyer of Hi Fi equipment and like many did a little bit of box swapping to get a different perspective from time to time. Having had a room at the Wam Show last year I found that some of the systems in other rooms that I liked to sound produced were all active speakers often with a full construction of cabinets and crossovers.

Sadly my practical and technical skills are fairly limited but having go involved with setting up my own Music Server Network at home based on LMS , Raspberry Pi and various players I have found I am quite adept at following instructions and getting things in place .

A further chat (admittedly while very drunk) with some of those at the show who had already made active speakers I cam away with an itch that I needed to scratch . Looking at the problem as a whole I tried to get a plan together that would be as simple as possible and also that would cost as little as I could get away with .

So my first project was defined as a Two Way Speaker , With Bi Wire terminals and sealed baffle design as a personal preference . I already knew that I was going to buy a MiniDSP HD 24 as this would take most of the heavy lifting out of the crossover part of the build . So scoured E-bay and found a pair of cabinet distressed but driver good condition Monitor Audio MA11 Monitors from around the 1986 era. Bought them for £15 and the project was now a reality . Almost by chance a MiniDSP HD24 cam on e-bay and joined the speakers .
A UMIK Microphone soon followed and everything was in place.

Next with the help of two Wammers I was shown how to set up a speaker to measure the units and establish the crossover points for the drive units using REW software . The speakers were then taken apart and the cabinets got a little refurbishment and the passive crossover disconnected and the drive units wired directly to the Speaker binding posts . Running the MiniDSP software I was able to put the crossover points in and switch between different slopes and types of crossover .

I then used two power amplifiers that I had in store (Trio Basic 1 (treble ) Quad 405 (Bass) ) and played a little music through them for the first time . The results were very good much better as a first trial than I had expected and the active speed of sound (how the notes stopped and started ) was very evident . Best of all the speakers were now sounding so much better than they did as passive units .

Flushed with my brilliance (yeah right) I started to study the REW software a little more and found that using the original sound measurements I had done on the treble and bass drivers separately it was possible to generate an automatic filter that made the out put come closer to the flat ideal that is supposed to be the goal . After many days and nights playing with these different filters I what I would call finessed the speakers the basic sound was the same but the bass treble and mid all became a single sound without any jumps between them the sound also started to Image really well.

Again I was happy with what I had done and the sound was for me still much better than I had expected . Then on reading through some of the threads from other MiniDSP users I was introduced to Dirac Live which is available as a bolt on software download and changes my unit to a MiniDSP DDRC 24 . Now this was a whole new world . Not only would my MiniDSP take care of the crossover but I now had a really powerful DSP tool that would calibrate and measure the actual sound from the listeners position and offer a very comprehensive set of filters that would produce a sophisticated change to the sound.

The first time I heard these speakers with a full DIRAC treatment I knew I was never going to go back to using the REW filters . It did everything they did and so much more . Best of all for the results the process was very simple and one that anyone could complete without any technical knowledge . Full instructions are given including on screen step by step help . The results are a real syrprise with very extended and musical bass and real tangable imaging .

I have since given these units away and moved on to my second project but will see how this thread is received before I add that .

Comments , suggestions , questions all welcome .

[struth]

sounds great. youve done very well, and obviously got to grips with the problems. look forward to how the new set progress

[Macca]

How did you deal with the difference in output levels between the power amplifiers? Does the mini-DSP handle that?

[Bencat]

Hi @Macca , with the standard MiniDSP HD24 unit the differences in output levels are indicated in the REW measurements and you can then adjust the individual units up or down to compensate within the MiniDSP software controls . However if you use the MiniDSP DDRC 24 with DIRAC Live then this software does this automatically for you .

[Macca]

I guess that makes life easier and you can use whatever amps you have lying around instead of having to buy matching units.

[Bencat]

Hi Martin yes it does make things easier but my own paranoia still made me use two Quad 405 power amps and I had both sensitivity matched because if I did not then I would always have the nagging feeling that the digital adjustment would be too much or that it was stressing the unit . Silly I know but it amkes me breathe a little easier to know that the basic matching has already been done before I apply any treatment .

[Edward]

Hi Andrew

It was me that invited you to post about your DSP experiments. Not surprised to read that you found a big improvement to the sound, especially the speed of the sound. It will be interesting to see what next steps you take on this journey.

I've also played around with active crossovers but took a slightly different path to you (there is a thread somewhere I did where I got a lot of help from people here).

Essentially, as an experiment, I used an 7.1 AV amp (to access multi channels) and a 7.1 dac (again for multi channels) and use Roon to provide the active crossovers (via their parametric filters) driving a 3 way speaker (removed passive xovers and wired direct). So 6 (2*3) channels in total.

My next step is to measure the in-room response (via REW) and dial that into the picture (using Roon's convolution filters).

Not sure if the minidsp or the dirac software allows you to tweak the horizontal and/or vertical alignments, but if so you can increase quite dramatically the 'focus' of the sound.

All good fun ....

[Bencat]

Well with my first project having gone well with a few setbacks but nothing major I now felt that I could tackle the real project I had in mind . The MA Speakers were unknown to me and were a cheap option to use and cut my teeth on making a passive speaker active .

I have owned for about eight years a pair of 1973/4 KEF 103 Reference Speakers . I first heard these at a friends bake off and was astonsihed at how good they sounded . I managed to find a pair on e-bay in fair condition at the huge sum of £63.42 , had to collect them from Lincoln but that was just a pleasant day trip for myself and my wife .

These have been my front pair in my AV set up , my speakers in my spare room and the main speakers in my music system . In all these uses they have continued to amaze me how great they sound considering how long ago they were designed and made .

So given that these sound so good in passive mode once I was confident of what I could do practically as it was important I did not destroy these speakers in the process as I do love them this was my second project .

Firstly the plus points , This is a straight Two Way Speaker design so the MiniDSP DDRC 24 was perfect . Secondly they are sealed baffle unit my preference as in my view this type of loading means that units are able to be used hard or close to a wall and that bass output is tight and controlled . The crossover in these speakers is easily accessed with the front mount removed and is bolted in to place so the full board just needs desoldering and then removing along with the mounting legs etc (these are stored away in case i ever decide to go pack to passive ) .Thirdly KEF very kindly published full specifications for both drivers including the measured and correct crossover point so no need for any REW measurement sessions as I already have enough to put the correct values straigh in to the DDRC 24

Drawbacks these are very old drivers they are in superb condition but they are likes hens teeth to buy in paticular the tweeter as it is a version that was only really used in this speaker . Secondly these are single wired units and need to be converted to Bi Wire . The speaker connections are in a hard plastic exstrusion on the rear with a scooped out shape which is not condusive to adding a second pair of 4mm sockets.

So a very intense day of deconstruction and bagging of all bits removed . Careful removal of the foam padding inside the unit and a quick note of how it came out so it can be replaced the same way . I had considered looking at the internal padding and possibly looking changing the amount (reducing the amount) or even switching to some thing like long wool but I very quickly came to the conclusion that KEF knew what they were doing far more than I di so keep things as they were . Then it was heat up a suitable skewer and burn the new holes for the additional 4mm banana sockets . Would have preferred to drill this but the shape of plastic extrusion made this very difficult so quick burn was the best option. Burn a smaller hole then you need then use a srewdriver (flathead) to slowly gouge the whole to the right size testing the fitting of the sockets till you are happy that tey can go in tightly but easily . Another essential with a sealed baffle of this age is to source and buy some sealing foam gasket material . Help from KJF Audio here with the neoprene tape sealant he sells which has a very good ability to spring back to shape after sealing so in case you need to open the front again after construction the material will still provide a good sels .

THen it was a case of wiring the individual drivers to the sockets for me keep with the norm Bass to the bottom two sockets treble to the top two . Fit the gasket sealing strip then replace the front panel and tighten it up carefully to ensure a good all round seal . With all the mechanical work now complete it is just a plug in to the DDRC 24 start a DIRAC Live session take your time and measure out the ten measurement points . Then as shown on screen optomise the filter and apply to the speakers .

Final result is honestly one of the best sounds I have heard at home . All the good aspects of the KEF 103 units are maintained but then you add in the speed and clarity of active and you somehting very special . I know anyone reading this will think , well you would say that after all the work you put in and I am sure there is an element of that but I have been listening to music on good sytems for over fifty years and I know what a good sound is.

Rather than go on about it I woud like to make anyone interested in hearing this sytem an offer. I am going to have a room at the Hi Fi Wigwam Show which is held at the Kegworth Hotel in Kegworth in the Midlands . The show runs from Saturday 16th (Set up day) with the main show on Sunday the 17th . Anyone who wants to can come along and this will be my main system . Come along listen and see if you agree that this is now a very capable system indeed and worth the work that has been put in to achieve it.

If I review the costs involved they are not that cheap but many of the additional costs are only at my choice the whole thing could be done for well under £1000 which given the quality of sound you get for me is money well spent as this will last you for many years of happy music enjoyment .

Only draw back which I freely admit is real is that once you start down this road you do have a tendancy to keep fiddling , just one more meaurment session with really accurate positions , or slight higher , shlightly lower mic placements just to see if it changes . Various changes to the House curve you constructed a little tweak here a little tweak there . Use the Power Amps one left one right or one for treble and one for Bass . This can go on forever if you let it . I think I am over most of that now and just leave things alone and love the music .

Thank you to anyone who has bothered to read through this I know it is a bit long but it has helped me to get it out and written down . If you are thinking about trying this then I am always happy to help either with what little knowledge I have , practical help to set up or even just support. I think active and DSP is a very positive way forward with music in a domestic setting as it gives you the real chance to change the weak link in our music chain which is the listening room which for most of us were never designed or built to be listening rooms and are always a compromise.

[Edward]

Interesting read Andrew. Thanks for that. I plan on going to to Kegworth and will look you up. I see you are also doing the suitcase challenge.

[struth]

Great write up. Speaks sound great