Something stirs in the Undergrowth

Ray P · Post by **Ray P** » Tue Nov 09, 2010 6:26 am

Hi Mark, very interesting - keep going, it'll be worth it! Would love to hear the results in the fullness of time.

I've been trying to mail Martin using the address on his website but they keep bouncing - looks like his mailbox is full - do you have an alternative?

Inspired by Martin's push/pull design I'm also thinking about something along those lines using my lowther EX4s, trouple is I would need one of the larger azura horns.

Also, did you consider the Bert Doppenberg approach? His Orphean Mk 2 looks promising and seems to be well regarded. Trying to find out more and get sight of some bass cabinet drawings. In that context, the Blue Thunder bass unts look interesting - shame the Focal drve units are no longer available.

Ray

IslandPink · Post by **IslandPink** » Tue Nov 30, 2010 10:35 pm

Ok, here we go. Breaking the habit , I'm posting again in less than one year . Speaker no.1 is finished , essentially , barring one extra layer of varnish on two of the sides , which will have to wait until I can get them outdoors again .
Wide angle lens makes it look wider at the top, but it's actually parallel .

pre65 · Post by **pre65** » Tue Nov 30, 2010 10:51 pm

Hi Mark, I rather like the look of them.

Ray P · Post by **Ray P** » Wed Dec 01, 2010 5:25 am

Very nice Mark.

Had a listen yet?

Ray

Dave the bass · Post by **Dave the bass** » Wed Dec 01, 2010 5:27 am

"Papa Fonken"!

Ooooer Missus, thats a big un.

DTB

andrew Ivimey · Post by **andrew Ivimey** » Wed Dec 01, 2010 9:02 am

Now that's what I call a speaker cabinet!

-plenty of room on top for a bowl of petunias.

Dave the bass · Post by **Dave the bass** » Wed Dec 01, 2010 9:05 am

andrew Ivimey wrote:Now that's what I call a speaker cabinet!

-plenty of room on top for a bowl of petunias.

And a whale.

DTB

simon · Post by **simon** » Wed Dec 01, 2010 11:51 am

Monster. Come on Mark, spill the beans

.

Ali Tait · Post by **Ali Tait** » Wed Dec 01, 2010 1:15 pm

You could have a proper disco with them!

IslandPink · Post by **IslandPink** » Wed Dec 01, 2010 6:53 pm

Plenty of room on top for .... a horn and a ribbon, more like

Well I had a listen to some music ( full-range ) then some test tones, last two nights .
There was some good and some bad. I liked the extra bass extension and the satisfying power and low bass lines I was hearing . The midrange also sounded excellent , shame I won't be using much of it ! ( the 285GMF is nice and flat out to 5kHz ) . In the middle it was less good, bit muddy and congested somewhere in the low hundreds of Hz .
I checked panel resonances and could feel the upper part of the back vibrating on some things.
So, on the test tones I found a very obvious resonance around 320Hz , and not much at all elsewhere . This can be sorted, and hopefully the mid-bass will sound a lot better .
At the moment I only have internal bracing from the front to the back about 1/3 of the way up, as shown on the Supravox plan . I will have more of a go on this in the next few days , might get the router out and make a bracing panel with cut-outs as per some i've seen people make recently . The sides are quite well-damped, with the multiple spacer pieces for the vents .
I'm also just going to buy some chokes to run a temporary 2nd-order low-pass for 750 or 800Hz now. Ultimately that slope will be provided in the driving amp .

ILPS

Ali Tait · Post by **Ali Tait** » Wed Dec 01, 2010 8:18 pm

Might be worth getting hold of a Behringer so you can play around easily with crossover points before you settle on final points.

IslandPink · Post by **IslandPink** » Thu Dec 02, 2010 9:54 pm

That's possible Ali , might be helpful . I know pretty much where the lower crossover will be - about 700Hz, but the upper one is up for grabs . I'm not sure how easy it will be to use with two different amps supplying to the speaker though .
I think the bigger issue is measuring and understanding the measurements . I'm sure Nick can help more on this .
One thing that's bugging me is that when I borrowed Nick's microphone and pre-amp before, the horn drivers seemed to give up suddenly around 7kHz ; I was led to believe they would taper off well above 10kHz . It may be I made a mistake in the set-up .
The other thing is that I've heard from LynnO and Gary that the Aurum G3 ribbon is not anywhere near 100dB/W/m , but they said the dispersion angle of these may make up for the apparent low efficiency .. (?)

So there's a learning curve associated with all this . I'll get there .

steve s · Post by **steve s** » Fri Dec 03, 2010 9:09 am

Its hard work to get the supporting speakers right, i had roughly the same issues Mark, the fostex tweeter i use is very impressive and would recomend that .. i did lots of home work before commiting to them, in the quality and the spl's they produce

my bass drivers where only good up to a couple of hundred hz, the vitavox's kick in about 1 khz to i needed another driver to fill in, hence 4 ways...

best of luck...

cheers

simon · Post by **simon** » Fri Dec 03, 2010 9:13 am

Steve,

How far down do you reckon your EX4s reach? Or to put it another way if I wanted to cross them over with a bass helper in OB where would be a good place to do it?

Simon.

Ray P · Post by **Ray P** » Fri Dec 03, 2010 10:29 am

simon wrote:Steve,

How far down do you reckon your EX4s reach? Or to put it another way if I wanted to cross them over with a bass helper in OB where would be a good place to do it?

Simon.

I've also been looking at Lowther OBs, underpinned by a 15in bass driver and there are some designs out there already - I started by looking into a route similar to Mark's but have become intrigued by the OB concept

It should be possible to crossover from the lowther to the bass unit down around 150Hz so fullrange, with no crossover issues above that. Need to filter the lowther to stop it receiving bass signals that will potentially damage the unit by forcing it to make cone excursions greater than it is capable of (there is no 'suspension' behind an OB driver).

The advice I've received is that the EX drivers aren't good for OB because of the filter module on the back. The EX drivers are intended for back loaded horns and the filter module is designed to stop higher frequencies getting into the horn - in an OB this means you get no rear radiation. I've started to look around for some used drivers from the PM range - perhaps a PM6A to start with - as these are supposed to be wonderful in OBs.

Ray

audio-talk

Something stirs in the Undergrowth

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