Quad 11L filter & cabinet upgrade

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Hi there,

here is the Quad 11L stuff (mine, victim of my willing to get the best of what I've in hands...)

The victim:
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Filter in the cabinet:
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An externally hosted image should be here but it was not working when we last tested it.

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and mixed:
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French guys advised me to fit the cabinet with sound deadening mat in the inside back of the cabinet, inside bottom, famous green wool in half instead of the black.
How about the filter guys?

Hi Matthieu,

It's hard to make out the exact circuit from the picture (for me at least), but I'll guess the film cap is in series with the tweeter. This will be fine but you could try an expensive cap if you like. Even a Maplin / LCR film cap would be nice.

The resistor will be in series with the tweeter. I'd change this to a 5w Kiwame.

One of the 'lytics will be in parallel with the bass driver for the 2nd order part of the filter, and you could change for a cheap film cap. I can't work out what the other cap's doing, but you could just change it for a cheap film cap too. It won't hurt, and will give a more accurate value than the 'lytic.

The inductor in series with the bass driver should be changed for an expensive heavy-gauged air-cored type, if you want to mess with it.

The cabinet looks like chipboard, which is fine as it has a pleasant character. For less vibration you could try adding mass with bitumen. You could also add some dowel bracing to connect adjacent panels.

Another trick would be strips of bitumen on the bass driver basket spokes.

That's probably enough ideas for now.

Hi Matthieu

Firstly I know nothing about building or modding speakers!

However another mod I've seen suggested (apart from the cross bracing between sides) is to take turns off the coil one by one to tune the frequency response of the crossover/ rolloff but I'm not sure which.

He suggested removing the wadding and fitting the sound deadening mats we use in the CD63/53 etc, but I'm not sure what the effect would be - he liked it though. Same as Simon's idea.

His other idea was to coat the crossover in Blu-Tack or similar to stop vibrations, for the same reasons we add damping material to the case of our CD players.

Oh, and Blu-Tack between the driver chassis and the cabinet to improve the seal.

I haven't had the time or nerve to touch my pristine 11L's in case they become no longer pristine!!

I'm sure you're in good hands with Simon as he's built some very good speakers by all accounts.

Good luck.
You'll want some kind of acoustic damping material in there, not just bitumen. You need something to control standing waves. My personal favourite is carpet underlay, but only a specific type. The foamy ridged variety sounds much better than the standard acoustic wadding or profiled foam. You'll hear better mids and bass. To tune you could add some lamb's wool (if you find the midrange has become resonant). If you try the underlay I'd suggest covering the rear panel and one of the sides and the top.

I'd not bother with the blue-tac on the x-overs, as it won't do a lot for the sound but it will make the parts hard to access.

Thanks fellows, yes that's very good budget speakers.
I'll go for damping, but what do you mean by brace between sides ?

Right now it's:
Half synthetic black wool changed by a french good one (green named "Thibaude"), top and one side still black, other side and bottom the green one. Under the wool and in the back inside some sound mat.
About caps I'll go for simple MKP from Mundorf or Russian PIO or such for the blue cap (// with bass unit) and good caps (Mundorf, Auricap, PIO...) for the series Yellow... and bad looking black.

Now I've to make a wise choice according to price and what people advise me as good caps.

Already a big thanks as I've got almost all the answers within minutes!
Hehe, I like to help when I know someone will be getting stuck in, as I'm sure you will be ;)

Actually I'm just looking inside my crappy Tangent Monitor 6 speakers. This prompted me to look. In my current situation I can't listen to my big ones, so I'm gonna have to mod these, they're very poor.... And no wonder - they contain tiny elco caps and teeny-weeny coils!!!!
Hi Matthieu

Brace between the sides to help stop the cabinet vibrating.

Cut a piece of fairly thick dowel (round section wood) to the exact width of the inside of the cabinet.

Make it a good tight fit, so better to cut it slightly too long then cut a little off again.

Put it inside the cabinet halfway down, so it is in the centre of the sides.

Check that the driver chassis does not touch it, then take it out and glue it into place.

Use good quality woodworking glue. (sorry that's the craftsman builder in me coming out!)

That should help to stop the cabinet resonating.

Simon is probably right about the Blu-Tack!

Good luck. Jim
SimontY said:
That's exactly the kind of brace I had in mind!

As a bonus you could position it precisely so that the rear of the bass driver rests against it. This is a good idea if you can position the piece of wood with sufficient precision.

You know me, I want to do it perfect! But what is "thick" for this piece of wood? I think this will be a challenge to fit as I have no room to get inside a piece of wood wich is far bigger than the holes of speakers! (at least one side should be removed to do so).

But all this stuff added will lower the inside volume of air!? Will loose in some area? Anyway I can't figure how to fit in a big piece of oak...
25mm thick will do.

Initiative test.............

Oh alright.......

Put one end through the bass driver hole pointing up towards the top (corner if necessary) and keep going until it's all inside, then turn it.

Remember it's the width of the inside of the cabinet and the speaker is taller than its width, so it should fit....(I hope!)

Good luck
Hi Matthieu. While you're playing with the crossovers, why don't you remove them from the cabinet completely and house them externally. They will then be isolated from the internal vibrations which will defo improve the sound.

Regarding dowel struts I was reading some posts by Dave at Planet10 hi fi, who is a fantastic speaker designer btw. He reckons that dowel is not worth bothering with as it will just resonate with the cabinet, possibly making things worse. The best bracing is a panel running down the centre of the cabinet, front to back. This brace should be about 50% holes of differing sizes, which cancels the standing waves. Is there any way you could fit a brace like this in small sections a piece at a time?

These are what I built

The brace is the peice down the centre

I realise you won't be able to fit this easily, but maybe you could fit it in sections, sliding each piece up from the driver hole. And yes, holy like cheese, lol.

o/t Simon, these are what I built using the Creative Sound FR125 drivers, and they are fantastic for the money. They were far better than my £600 Ruark Templars and almost as good as my mates £1000 Ruark Preludes in a small space. The bass from the cabinet is awesome.

If Planet_10 says dowel doesn't work, I'd believe it doesn't, I just thought that connecting two sides could only be positive, and was easy enough to do...

Matthieu, you obviously cannot add a proper brace at this point, one the full length of the cabinet needs adding when the speaker is being built.

And with it being a fairly tiny box it doesn't really matter! Add some bitumen or similar to the walls and see what that does. Don't assume it will be perfect though - some speaker manufacturers have considered the resonance of the box and allow for it as part of the overall sonic signature. I'll let you know how I get on with my crappy Tangents too, see if any ideas can be transferred.

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