serenechaos wrote:

Did you use LEAP or anything like that, or just cross everything over 1st order as a guess, and tune by ear?

Oh, no. I do not use any LEAPs or others tools, no time domain analyses or anything like this – there is truly no need for it. The MiniMe case is very simple, not to mention that I generally have attitude toward many questionable design and substitution methods if they were used with no need.

In MiniMe everything is very simple and the key is to determine the bandpass for the MF driver. No one prediction software in the world will tell you where to cross it – you need to hear it. The first order on MF driver is expected based upon the Macondo Axioms.

The tweeter is ribbon as any good ribbon it sounds a few Hz above better then a few Hz below; even though this particular tweeter has something that shell make him more midrange-capable. I still would like to do go with tweeter more then I need to in order to compliment the MF driver. The tweeter crossover is other story. I believe that a ribbon tweeter can’t have first order passive crossover. Even if we do a first order passive then the inductance in the transformer still make it to behave like second order. So, why bother and do not do a pure second order? In my case I used an external coil to work alone with the inductance in Primary to write a perfect 12dB per octave Bessel curve. I might move is up and down in crossover point but the second order Bessel will be there foe sure.

The woofer is tricky as they are in a way abnormal and I would like to use the Resonating Oops on them, if I might. Therefore I have no idea where to cross them. I have no idea how low my MF will be in the box that I have made… So we will see.  The connection of the woofers is a variable as well as I do not know how I will be driving it and if I need to have high impedance at LF. If the tail on LF will be too long then I might go for a subtraction crossover but I think what I sketched able is a good starting point.

As you see there is not room in there for LEAP modeling everything is arbitrarily but the actual sound.

I got today from my machinist the complete MiniMe enclosure, he did a good job.  It looks so simple but it was reportedly pain in ass to do it, not to mention that it turned out to be much more expensive then I originally expected. The good part is that the enclosure has a very good “feel” and surprisingly heavy. When I tap the enclosure it does not response like wood but rather as some kind of heavy cardboard. I kind of do not like it but it is not treated yet. It will be 4 ribs inserted into the bass enclosure and glued in. They are a 5” wide and have a special curved profile to be inserted through the drivers’ holes. Also the internal wall of the bass chamber will be damped. Let see how it will be response then. Well I say is as I know how it shell response – in really I have absolutely no idea…

The cost turned out to be high. The MiniMe is made with ½” G10 and glued by Loctite 454. The Loctite 454 is looks like very cool, those expansive: $20 per 10g. The G10 cost was around $1800. It took 31.5 hours for my machinist for the whole project. It is time $80 made $2500 for labor. So, the total cost so far is $4.300. The cost of the drivers $1300, plays the cost of damping, bolting, the weeks of testing and crossovering – it will be total around $7K – way far from the cheap and dirty MiniMe that I originally intended. Funny fanny but it will be more expensive then the Macondo Horns…

Anyhow, it is what it is. I do not necessary as much bitch about the cost as about the lock of assurance that the MiniMe might end up as another failed projects, as do many in recent times. I still have no idea how the MiniMe would be sounding but I do admit that it has some aspect of interest to navigate this project.

At the picture the speaker looks big but it is because it is white. What it will be black it will be less demanding. I still think how to finish it and when to finish – after I leans hot it sound or before it… A big dilemma as if it sound good then it will be textured back, if it sound like crap then it will be green with red stripes…

Thinking about the MiniMe this point I already know that I made a mistake with the MiniMe design.

The MiniMe might turn out to be an OK speaker but when I was thing about its dimension and the way how it will be used with Macondo I was thinking about MiniMe’ sound as a self-contained acoustic system that might be in away mimics what Macondo does in my room. It is hard to explain for people who did hear it but Macondo does have own unique imaging presentation manner. Good or bed but I very much appreciate this manner and I thought that it would be cool of MiniMe would be able if not mimic (I do not think it will) but at least to image in the same fashion.  So I made some decisions in the MiniMe enclosure design that I thigh would be positive and most likely they are but only in context of stand-alone loudspeakers.  This kind of shoot the ides of MiniMe in it’s foot as MiniMe shell not be “generally good” but shell be “a second speaker in the inhalation the fist acoustic system”. Generals’ it means the I was a fool presuming that MiniMe shell be doing anything the Macondo does and if I disregard this fatly intention then I would probably shell would do the MiniMe 1/3 times smaller. Then MiniMe might have more “limitations” then it might have but it would be much more incorporable in context of my current Macondo. I do not say that MiniMe is not incorporable as now but it think the MiniMe turn out to be a bit much more demanding they I though they need to be.  I think this time my selfishness for inches played a back joke with me…

Well, it is not the end of the word that MiniMe is a bit larger then it might be buy I would need to review the ways in which I will be using it…

I was listening last night the HF section of MiniMe. It was interesting and frankly very promising. The RAAL 70-20XR were fine and he JBL5 did splendid. They are not properly integrated, were not measured and were made up to work together well, it was juts ad-hock play but it was still very demonstrable that I will have absolutely no problem with HF section of MiniMe.  The enclose tune out to be also very good.

The RAAL 70-20XR crossover is exactly as it depicted here:

 The coils I use the air- core litz and the C1 cap is an assembly of 3 Vitamin Qs. However I wonder about the C2 cap for MF driver. It will be +- 5uF around 30uF, so what people use nowadays. I personally have no problem to do for electrolytic, perhaps with so beloved by me active biasing but I wonder if anything else exists out there worth to pay attention.  I do not like metalized film caps. The film and foils would do for me but 30uF is kind of hard to get in manageable size…

The LF filters, as well as the LF whole section will be more pain in ass to deal with. I drown all drivers in series juts for sake of simplicity but it will be different I am sure as I will be going into it.

Sure I was not able to do not listen it as the pain dried. It was incredible ad-hog sting of the drivers. All woofers are series. I know, I know but they are 4R each and I wanted to drive it with 2A3 just for the first test. The post is tuned - I have no idea where. I put my port’s flare into the hole, with no pipe, taped the wooer and said to myself: “There is an order to consider it  OK”. The woofers have no low pass filter. It is by amps with right and left channel of 6E5P-2A3, I have finished just one speaker. I did no measurement of any kind; I just checked the phases on each driver. I wanted to her this thing…

I have to tell that I think I will be getting from it more then I bargained. Even as it the MiniMe I think has some potency. Among the noticeable things it has very strong lover MF and upper bass beaming and if you are in the focus of the beaming then it hit you with very surprisingly-good upper bass. I think I need to work with this low-pass for woofers to minimize the line-array effect for MF. Whatever it is it abseil very different sound then hat I am accustomed. I need to start to tech this speaker to sound right but as not I have to tell that it is turning to be a very cute sounding machine…

Ok, I did play today with the MiniMe. I have to tell that then it turn black I kind got soften with it does not look to me as large and violent as I initially thought. I made some measurement and some listening. I peaty much know what I want to be and it took no time to make the MiniMe to sound more or less civilized.

The RAAL tweet is invariably inverted to MF and with crossover exactly as at in the drawing above. I do not feel that I got 93dB, I would more likely see 91dB, but it is OK, it is a ribbon and it might run softer. I had a lot of problem with MF driver. I have 4 LE5-2 drivers and all of them sounded very poor, with sensitively around 88 and a huge peak at 7khz. I figured that they might be discharged. They have an OK tone but not usable in MiniMe as they are now. I have a pair of 2105, that are the very same LE5-2 and they were absolutely perfect. I though them in but then had the same 5-6db peak at 7khz. I have no idea where it come from – the do not have the ugly JBL metal dust caps… I decided to let them to start to roll at 4.5K, unit the peak at 7khz and contra-balance to the engaging filter - I was .2mH large air-core coil. The MF was near fixed. It still has a small heal in there but not the one that I would feel need to be address as during my “quartet test” I did not detect any problems. I know, I know, the thinking reader would ask: “Romy, what are you doing? The story with Vitavox repeat itself? You again use the driver’s resonances in an auditable range, refusing to cure them?” Sure, I do, good luck to you.

The MF and bass are in phase. The woofers as I expected did not want to roll off – the freaking inductance of the driver sink the filter inductance. So I stated with a huge 7H air core coil. It has too fast roll off sonically and RTA showed the same.  I went for my favorite low-pass design techniques that I use for years – the “Trout Techniques”. The technique is very simple. I drive the LF section with a long cable that come across my listening reference spot. At the spot in the cable colder a coil intentionally larger then necessary – who know HOW those woofer’s VC will skew the coil up. The CD player plays in look the final from Schubert’s Piano quintet in A, the infamies Trout Quintet. At the listening spot I am listing the music and holding the large coils with signal passing through it, very slowly taking the turn out of the coil, looking when the integration between the upper knew of bass and lower MF will be right. I end up at ~5.1H that is around 1000Hz for woofers – well let it be so. I did not deal with the port and the lower knee of the LF section. I will leave it for later and have a large 4” hole in back –  in fact it is not bad but I am sure will be better.

So, the speaker is well balanced now and generally listenable. Yes, I took 16R LPAD and was forced to roll MF and tweet foe a few DB – do not forget that I have 16R of 4 woofers. Yes, I but a lot of sensitivity and I think now I am at I think 88dB-89dB, I did not measure it. I took a SS 70W amp with STR ships and decided to listen it. So, how did it sound? Well, I am sure that simpletons of the Joe Roberts caliber would consider that it was OK, in fact it was impressive when I was playing the pop cuts from my measurement disk. (I like the Sheffield Test tracks). When I went for civilized music it was revolting, I am not kidding. I was listing and even wondering if I need to make the second speaker for THAT result. I thought that it might be an amp and it was – I switched to 6E5P-2A3. It of cause has some severity but no power. Come on, it is a flimsy 2A3 driving 7K – too much to ask. I tried the full-range Milq that is 12W with single plate. It was better but still not where I would like it to be. I know what I need to try – there is the only one powerful amp the I would trust to do the job – the Lamm M1.1 but it is not the amp for MiniMe requirement. So, I was sitting and scratching my back – what an idiot – build a speaker and was not able to drive them.

Hey, does anybody in Boston have a single M1.1 that you can borrow me? At least then I will be able to found out how it might sound and would go from there…

Well, it is very obvious what MiniMe needs. The speaker is begging for multiamping. The speaker has 2 distinctly different sections. The HF section has 4-5db higher sensitivity and SET friendly. The LF section needs 100W of output impedance that deal with port’s current sinking, Sure it shell be SET/SS multiamped. I did try it to drive like his last night and it was almost tolerable. I did not play with SS bias and port setting on bass section but it was clear that 100W was the direction to go.  What suck in all this business that multiamping is fundamentally against the whole MiniMe idea. The MiniMe have to be cheap, simple and none-demanding. OK, I have blown the cheap part but the rest I would like to maintain. Theoretically if I found a cool-running 100W amp that would do OK on MiniMe’s HF channels then I would be fine but from what I feel that time of amps would be a large “class A” amp and I am not going here. Alternative would be to use the a little SET with some kind of very small A/B sub 500Hz bass amp, perhaps even class D amp, even if I doubt.  I would like to have all of it cool-running and be managed by a single switch.

BTW, here is another situation where there is very clear and rational need for a product but the industry does not offer anything.   There are huge numbers of speakers that are built in the MiniMe configuration – separate LF and MF section – Verity, Wilson and many-many others. It would be so good to have a dedicated bi-amplifier for them. Something not expensive – $2K-$3K, that has aboard a cheap DSET for MF/HF and a high current A/B class SS amp. If everything is arranged in a small and convenient packaged, supplemented with a reasonable 4-wire speaker cable then here is a ready to fly from the shelf product. I think if it doe properly then this “combined” amp might be very successful tool. The freaks out there you are in the industry take a note.

Actually in multi-amping is does work and I was able to get quite assessable sound that might be considered OK for MiniMe. The HF channels do very nice with SET and the bass section does Ok for MiniMe. I think now I am encouraged to complete the second speaker. I think that with all appeared complexity of multi-amping it is in fact is simpler way as it would be VERY difficult or expensive to found a full range SS amp that would do the job.

To finish the projects I need:

1)  Finish the second speaker

2)  Consider another SS amp, perhaps class D amp for bass

3)  Found gaskets for woofers as they resonate at 220Hz

4)  Put the Bass filter in bass amp

5)   Fine tune the position of MiniMe what the second speaker will be up.

In a long run I would be open for 100W class A/B SS small amp that would be a able to drive the MinIMe full range but surprisingly the MiniMe has a very good upper range section and it would be I think very hard to find one.

..."It won't be long now."

The progress looks good and no green with red stripes!

If you are really interested in moronizing your room, GTT Audio & Video are selling some Kharma Class-D's on audiogon.
http://www.audiogon.com/cgi-bin/cls.pl?ddampstran&1237509628&demo&3&4&
Looks like they are trying to sell them before they go in the trash...They are in New Jersey and are probably open to negotiation.

LBJ

Lbjefferies7 wrote:

If you are really interested in moronizing your room, GTT Audio & Video are selling some Kharma Class-D's on audiogon. http://www.audiogon.com/cgi-bin/cls.pl?ddampstran&1237509628&demo&3&4& Looks like they are trying to sell them before they go in the trash...They are in New Jersey and are probably open to negotiation.

Do they come with a jar of Vaseline? Well, if Bill sells it and TAS approved it then it shell be a true crap. I am very much not a fan of class D amps; in fact I know that they shall not be good. They might works in my case for bass application. It however will definitely not be the Kharma’s off the shelf $50 amps rebranded as a “big name” manufacturer and hyped by marketing the whores. No one “invent” or “design” those class D amps. They are a dose of Asia-made modules and they pretty much all come from the same barrel. If I get a class D amp then it will be $250 max trial investment and if a person tell me that I need to pay more in order to get “better” sound then I would hiss in his face. BTW, if someone knows a good a good $250 around 100W class D amp then let me know.

miab wrote:

I've been following your project with some interest. I've been experimenting with a horn loaded mid bass cabinet and have isolated a resonance around the same 220hz mark you mention. I feel/felt the inadequate cabinet bracing is my problem but you mentioning gasket in the same breath as your resonance has me curious. I have not mounted a gasket between driver and cabinet but maybe I should try? Do you feel the gasket will help by air sealing or for giving a very minute buffer from cabinet? Perhaps even not fully tightening and perhaps playing a tightening tension vs. resonance control?

Miab, I can’t be certain as my experience in those speakers making is very limited but I think that it is not the enclosure resonance. It is too abrupt to be enclosure. It exist at 223Hz and gone at 237Hz. Also, when I stress the enclosure the resonance is not changing, however when I touch the screws with which I tight the drivers, juts very slightly turn them, than the resonance is gone completely. Well, it is not gone but moves to other frequency, uselessly from 210Hz to 263Hz. So, I have 4 driver 16 screws and I might play with them, juts one of them impact the resonance. I PRESUME that it might be cured by gasketing as my baffle is not wood but G10 is much harder, I was not able to drive screw into it and was forced to pre-drill the holes.

I was looking around and I was not able to found 4.5” gasket, so I think I will use viscosity dumping. A few year back I bought in Home Depot a brick of some kind palmer substance that was made for attaching it to the thin pipe assemblies in order to make the pipe do not buzz.  It feels like a rubbery butter and I used in to mount drivers in past and those techniques were in use in 70s by some manufactures. Let see if it help in my case. If not then it would be more pain in ass but let hope for the best.

jessie.dazzle wrote:

I feel a driver needs to be somewhat hard-mounted to the enclosure. Cork gives the right sort of balance between hard-mounting and floating, while still sealing.

Romy the Cat wrote:

BTW, if someone knows a good a good $250 around 100W class D amp then let me know. The Cat

I did put some gasketing under the driver, not thought but to so what it will do. I used the substance that I described above. It is Home Depot 3207680110 or the model #DS110 Pug duct seal by GB Electrical. The best thing about it that it is that plaster doe not glue itself to material and can be easily collected back.  I applyed the plaster only on one side of the driver, presuming the it shall jam them

The effect was very positive; the amplitude of the resonances went back and bandwidth of the resonances collapsed very much. However, the resonances did not go away and at higher amplitudes the speaker picks 1-2Hz wide resonances here and there, primary between 230 and 280Hz. Touching the screws do address them but it moved them to different frequencies. Now the problem not as bad as use to be and the resonances are not auditable during music playing.

At this point I do not know if I need to deal with it further. I never had an experience to have a good commercial speaker to drive at a lot of power from a generator with 1Hz steps and to see if it will resonate. I did it with a number of vintage speaker, those that conceded good one, and the resonated like hell, nowhere near what the MiniMe does. So, I do not know if it is acceptable.

Still, I think that it shall not be this way. I still do not think that it is the enclosure and to deal with it properly I need to eliminate any contact between the drivers and baffle.  Jessie was right – to use cork gaskets would be the right direction to do and I think if I would not found other means then I would need to buy the cork sheet and cut them myself. Meanwhile if someone knows any thick 4-5 gaskets then let me know. When I say “thick” I mean that I would like not to use .25 mm paper gaskets but rather 1-2mm cork-like gaskets…