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Old 25th July 2012, 03:44 PM   #1
serum is offline serum  Netherlands
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Join Date: Oct 2008
Default Building, (WIP) of an active speaker..

I was a passive cross-over kind of guy, but fell in love with the simplicity of active crossovers. (i build an active cross-over box, inspired by the box of doom of Keith Kidder. I can post pics of a passive crossover, if anybody is interested) it's a neat test-box with fully adjustable 6, 12 and 18db/oct parallel filters, with a relative large range) it's been another time-absorbing project i've finished last year. It's been perfect for adjusting filters on speakers on the fly.

About these active speakers;
The goal is to get a linear response, with an in your face stereo-image and a low distortion, and capable of a higher low distorted listening-level

So far i've played with the idea of the BMS4592 and consorts, but i couldn't get a proper figure on their distortion, plus their frequency response wasn't all that either.

I came across a Limmer 042 horn. Pretty straight forward; 1" driver, 6" mid. The form/finish wasn't all that..

There are soooo many options; at a certain point you (I) need(ed) to start somewhere.

So i bought the Limmer 042, along with their Ciare advised mid-range. The Beyma CP380m is used for their high.

Listening/tweaking for a few weeks made me realize this wasn't making me too happy. The mid was way too harsh. They had a kind of quack you would expect form a horn (or a group of ducks in your bathroom, it was that bad..). I was planning on ditching the project an move on. I remembered i had a set of eighteensound 6nd410's wandering around, so i gave them a go. Didn't expect much from them, to be honest, but to my biggest surprise they did exactly what i was looking for. An in your face kind of stereo-image, no harsh mid, and at higher listening levels the ease of the sound/stereo image maintained well.

Some measurements of the mid-high response of this setup; (ignore the part bellow 800 hz, this is the poor quality of the woofer i've combined them with)

The Beyma CP380M;
Click the image to open in full size.

The Eighteensound 6nd410;
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Singing together;
Click the image to open in full size.

Note the response is made with a 1/24th octave smoothing.

Here is the measured distortion;
Click the image to open in full size.

I love their sound. I'm using a set of Kef 105/4 speakers currently, which are pretty good. but relative damped and flat stereo image. The voices are a tad too soft on them too IMO. they are the labrador retreivers among the speakers, i guess. They won't harm anyone and are a friend for about any record you throw at them.
i enjoyed the test-setup of these limmers way better. So I went on with the project.

Here is the design i'm following;

Click the image to open in full size.

Last edited by serum; 9th August 2012 at 05:52 AM.
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Old 25th July 2012, 05:14 PM   #2
serum is offline serum  Netherlands
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This is the Limmer horn, shaped to fit the design a bit better IMO. I

(it normally is a square, with relative round edges)

This is what it originally looked like;

Click the image to open in full size.

and here is the one that has seen the router;

Click the image to open in full size.

For the round parts; i needed an R75 (~3") and haven't got access to such a large cutter, so i started making making them from several layers;

they are shaped, so they can hold a panel of 22mm thickness

Click the image to open in full size.

This is the jig i've made to cut out the Limmer shape in the baffle; (the baffle bytheway will be made from 21mm thick bamboo, has anyone got any idea what this material is like to saw/route?)

Click the image to open in full size.

this is the backside that i will put over the backside of the Limmer; i'm filling up the space with dry sand.

Click the image to open in full size.

here it is with the horn and backside in place (the backside needs to be 2 parts, it's impossible to mount the driver in place without these two parts.

I've removed a large ring from the CP380's. All it did was resonate like crazy; It normally looks like this;

Click the image to open in full size.

The rough shape of the speakers;
Here i'm using templates to make room for the bamboo frontplate.

Click the image to open in full size.

The two of them;

Left and it's mirror brother, Right. Serious braces will be added, as well as a separate chamber for the amps

Click the image to open in full size.

For amplification i'm using Hypex amps; for mid and high i'm using the UCD180, and for the woofer 2 UCD400's in bridge. Powersupplies are the SMPS400/180 and the SMPS1200/400

i've made 2 aluminium plates per enclosure, well, 4 actually; 2 for the amplifiers (1 for low, 1 for mid and high) and 1 for the inaudible fan, and 1 for the power-inlet/on/off switch. No XLR input on these speakers; I'm directly feeding the amps' input from the cross-over.

here is one of the plates;
Click the image to open in full size.

Combined with the power inlet;
Click the image to open in full size.

Backside of the total amp-plate;
Click the image to open in full size.

result of hours of milling;
Click the image to open in full size.

Not the best pic, but here are the amps on the back of the speaker;
Click the image to open in full size.

In the meantime, i've finished the speakers with white HPL, i'll get some pics of that up later.

Last edited by serum; 25th July 2012 at 05:35 PM.
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Old 26th July 2012, 06:15 AM   #3
serum is offline serum  Netherlands
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Finished them with HPL; Need to stop making pics with the phone, so it seems.

Click the image to open in full size.
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Old 26th July 2012, 06:50 AM   #4
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You seem to be Mr CNC !
Very nice and professional looking build !

Did you do the measurement inside ? I am not sure but I guess the response irregularities are not caused by your woofer but by room interaction. And if it really IS an in-room measurement then I must say it is even veeeeery good.

Regards

Charles
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Old 26th July 2012, 08:08 AM   #5
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It looks amazing.
I wonder if for good high fidelity the mid horn wouldn't sound better without that phase plug-like bulge in the middle? Is it necessary?
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Old 26th July 2012, 10:38 AM   #6
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Outstanding CNC work but why the asymmetrical design (curved on 1 side)?
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Old 26th July 2012, 02:54 PM   #7
serum is offline serum  Netherlands
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Thanks for Your comments.

Measurements;

Yes, these are in-room measurements. But i also performed a close-range measurement on the driver/reflexport, it's pretty bad. The undeep enclosure of the bass-speaker made it sound pretty bad too. I didn't paid too much attention to the woofer to be honest. It would be replaced anyway.
I hope/expect the new woofer to perform a tad better.

About the horn;

if i take out the phase-plug (that's what it is) it will increase the A1 of the horn, as well as the entire geometry. It sounded/measured good as it is; i'm debating whether or not to make a new phase-plug, and integrate this directly with the mid-range driver. (remove the dust-cap and make a plug that is mounted on the driver) Soundstage was pretty consistent, and the speakers had a nice and even roll-off when measured under an angle. (no large diffractions) It's not my first priority to do tests with the phase-plug setup. If i take out the phaseplug to replace the dustcap though, there is a cosmetic defect on the horns, which i'm not too fond off. Removing it never crossed my mind, to be honest.

asymmetrical design;

The last picture isn't how the speakers will be used. Perhaps that makes it look weird? the left is standing on the right and visa versa. The first picture (design drawing) is actually the left speaker. I'm really fond of the extra curve. if you combine the two speakers, it falls together nicely. (i won't argue your taste, if you don't like it )

Last edited by serum; 26th July 2012 at 03:13 PM.
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Old 27th July 2012, 09:45 PM   #8
serum is offline serum  Netherlands
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Default Twaron damping?

I'm planning on using twaron elves/angel hair for the the low/mid range;

Has anyone got experience using this stuff in a reflex cabinet? (elves hair, that is) I'm used to the basics that a reflex cabinet needs damping on the walls only, but this stuff seems to be used throughout the entire cabinet? Or a large dab behind the woofer?

This is the xo filter i'll be using; a 2496 with a modified output stage.

Click the image to open in full size.

Click the image to open in full size.
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Old 28th July 2012, 10:32 AM   #9
serum is offline serum  Netherlands
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Default Few more pics;

Tiny jig to make the round edges on the bamboo;

Click the image to open in full size.

bamboo plate in place;

Click the image to open in full size.

amplifiers in their enclosures (they will be glued in the cabinets);
Click the image to open in full size.

Click the image to open in full size.

Mid and high amp;

Click the image to open in full size.

And for low;

Click the image to open in full size.
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Old 2nd August 2012, 04:24 PM   #10
serum is offline serum  Netherlands
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The bamboo is nice to work with, didn't expect it to handle this way.
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