Mark 1 3 way speakers

Chluz

Member
2010-09-19 1:32 pm
I've been following a few threads on this forum, enough to know that you guys know what you're talking about! As I decided to build my own set of speakers, I though I would open a thread here so that you could give you're input and constructive criticism about this project.

This is my second speaker project, the first being a subwoofer which was a massive failure. All the details of this project can be found at this adress :
Mark 1 : 3 Way Speakers

To give you a quick rundown, the idea was to replace blown out speakers from a sony cabinet by changing the filters and the front faceplate. Therefore, the enclosure total size was pretty much pre-determined.

The drivers I used were :
- Tweeter : Hivi SD1.1A
- Mid : Visaton AL130m
- Low : Hivi F8

The Filters were completely built from scratch. The Project is still ongoing but is nearing completion. Any input is greatly appreciated, as I don't really have any experience in building these things; I'm finding it loads of fun though ;)

Thanks !
 
Hi Chluz,

I haven't looked very deeply but a couple things stand out. First, the picture loading is very slow. I had to go get a coffee while I waited. I hope that's something at this end or it might discourage others from getting into it.

Once the pics fully loaded I see the tweeter and midrange side by side. This means it will be better if the speakers are on their sides rather than upright.

Also, you might wish to reconsider the layout of the XO before you make it. In the pic you show, the coils are close enough together to interact. There are some suggestions for layout on the net that include running coils 90 degrees to one another to prevent this.

You might also wish to add a ring of foam around the tweeter if you cannot rebate the baffle (faceplate)

Make sure your cabinet is well braced internally and properly damped.

I hope this didn't sound discouraging, I kinda like it when you can upgrade a set of boxes. Good luck with the project and show us more pics as you go along.
 

Chluz

Member
2010-09-19 1:32 pm
Thanks for the input Cal !
I resized the images. I was accessing them from the same network as the server they were stored on... didn't realise that you guys had to go through my internet connection ;) it should be better now !

I would have liked to place them aligned, but there wasn't enough space for that (a couple of cm missing), so I put them side by side. I had read somewhere that that would give phase problems, but I wasn't sure what that meant in listening terms... could you explain what the actual difference is between aligned and not aligned (sorry newbie here)

For the coils, I hadn't thought about that at all , thanks !! only problems is, I already soldered the parts... Would it be possible to avoid the interaction by placing metal plates between them ? or would that cause interaction between the coils and metal plates ?

Thanks again for having had a look at my project.

EDIT : Forgot to ask, whats the purpose of the foam ring for the tweeter, is it to stop the tweeter vibration from reaching the cabinet ?
 
Last edited:
Hi,

Having the mid and tweet side by side means that you might have comb filtering or lobing issues between them where they overlap. You will notice this if you move around while listening. It's sort of a drop out at certain frequencies. It all depends on what the XO frequency is. The higher the better for avoiding this.

I don't know what putting metal between the coils would do to avoid coil interaction.

The foam around the tweeter helps to "smooth" the sound. It reduces the diffraction caused by the flange of the tweeter if it's not rebated flush with the baffle. You can make it about the thickness of the flange or slightly thicker and do some experiments to see how much of a difference you notice. Make it about 8" around and cut the hole tight to the tweeter. Change it around a bit to see what works best or if you notice any difference at all.

There are others here that are much smarter than me but hopefully those things will help.
 

Chluz

Member
2010-09-19 1:32 pm
Concerning the coils on the filter being too close together, I found this page : Placement of coils in crossover networks:.

Basically, putting aluminium next to the coil is going to make it worse. So I'm now thinking that i'm either going to have to live with it, or find a material that stops magnetic interactions, but doesn't react with the coils. I'm thinking some kind of very dense material (maybe schist in plates, the kind that was used on roofs before ?) but if it gets too crazy, I'm just gonna live with those 5-10% coil variations, and the eventual crosstalk...
 

Chluz

Member
2010-09-19 1:32 pm
Thanks for teh input.

You're right, i'm going to take out the two middle coils, and only move those out of the circuit board and onto a wooden support in front. That way the two remaining coils will be far enough from each other, and i'll have extra space to add better connectors for the cables !

I'll try and do that tonight and post some pics !!
Thanks again for your help.
 

Chluz

Member
2010-09-19 1:32 pm
I found another bug in the crossover : the L-pad on the woofer !!
That ,really sucks (energy) !!
You just can't put resistors before a woofer , only in some rare cases where
there is an impedance mismatch...damping factor...between the amplifier and the boxes

You're probably right. I looked dubious when I saw the L-pad that was needed to get balanced dB outputs from all speakers, and figured I can always add a couple of cables in and compare if I want to bypass the L-pad ;) If it sounds better to my ear, the woofer Lpad will be only cosmetics . Maybe i'll look into a Baffle Step Correction circuit also, although I'm not familiar with them.
 
Last edited:

Chluz

Member
2010-09-19 1:32 pm
Had a bit of time on sunday so I got to work on the speakers a bit more.

I had a quick listening test with and without the woofer L-Pad, and of course without sounded a lot more balanced towards the midrange. Overall a more 'groovy' sound. So the woofer L-pads have been taken out.

I've been siliconing the whole of the inside of the box, and mounted the crossover in. I'm waiting for the silicone to dry ATM, but I still have to go and get the wood panels for the mid enclosure, glue and screw them in, and then re-silicone that.

Then there the question of port tuning. The posrt is currently 51mm in diameter and 150mm in length, that gives an Fb of 33,05 Hz. I wonder if I'm not going to shorten it to bring it up to 40Hz, will see.

More pictures coming soon.
 

Chluz

Member
2010-09-19 1:32 pm
Had a first listen.

The high are a bit 'hissy', especially with words ending in s and female voices. I read somewhere else that thats the problem with lower end tweeters, oh well, I wouldn't have noticed it had I not been looking for it !!

The mid at first sounded fine, and then a punk rock song from greenday came on. It then sounded really confused and imprecise. So I opened up the box, and stuffed the mid enclosure with acoustic wool. The result is slightly less 500-600 Hz frequencies from the mid, but much better clarity.

For the bass, I find theres a pretty good reproduction of low end bass (typically base notes that before used to be all the same) compared to celestion ditton 22, the bass is drier and punchier (if these are acoustic terms :) ). I will keep listening to them and try and pick up defects. Also, I finally understand what lobbing issues are. When putting the speaker vertically, you do get some of the frequencies cancelled out. Thanks Cal for mentioning that.

Unfortunatly, I don't have enough knowledge to be able to tell what components of the filter need to be tweaked up or down , but I'm hoping that will come in time. I'm sure these can be improved miles on by more research and time, and there will probably be some tweaking as I design other speakers over the next 60 year !!
 

Chluz

Member
2010-09-19 1:32 pm
Painting and first listening impressions

For the paint job, I was gonna go for a piano gloss white, and read around about how hard it is to actually get this right. So I decided to do something close instead with paint and varnish instead of laquer. What I ended up with was a near piano white with orange skin effect (9 coats of paint, 3 of varnish). This was all done using a low pressure paint gun, and lots of manual sanding (it seems impossible to get 400 or 600 grit paper for circular sanders in this country...). I put down the orange skin effect to not enough sanding between layers (it felt like enough in my arms though, I can tell you that !). I painted the front plate and back seperatly... I'm now thinking this was a bad idea, as the tight fit between the two parts caused small chips of paint to come off when reassembling... I guess now I know not to do that again !

Details of the paint job and photos on my blog.
Painting and first listening impressions

I've noticed there is a very big problem with the tweeters at loud listening levels. This was tested with an old Marrantz hifi amp, and then with a power amp to see if the problem was not actually coming from the amp itself. What happens is that I hear loud (shrieking) levels of distortion in high frequency sound when I listen at loud levels. If anyone could give me some pointers on how to potentially get rid of this, I would be vey grateful !