Getting the horn - well 2 to be precise...

After hearing Mr Coco's conical horns - esp when attached to Vitavox S2 drivers I must say I was impressed.
What sealed it was hearing them in my own home with lash up crossovers - they sounded mighty good! The GRF cab doing all the lovely mid bass and bass stuff of course!

A long informative chat with Mr Coco on what sort of compression drivers would be good set me a researching. One idea was just to get a pair of AH-300's like I'd heard.
Know what i am I getting and all that. But the price tag is quite stiff - $2700 full price and who knows if you get customs and vat on that as well.
Saving up for a pair of nice Vitavox S2's would be pretty expensive too!

Another idea was to have the wood cut by someone like Avon ply but they and all the places I tried ran a mile from this one - I guess too time consuming to do with a realistic price / to Avon's very exacting standards...

So could I cut 24 angled / tapered slats with simple DIY tools in my workshop? They challenge was on!

First some design - I have a pal who is a whiz with cad.

Here is the CAD drawing of what was to be achieved...



From what my CAD pal told me the cut angle needed would be 15 deg, Taper from 124.5mm down to 22.2mm - 0.2 of a mm, nice!

Mr Coco sent me an interesting link to a cool dude who had made similar cones but even bigger

http://sites.google.com/site/diyfirefly/100-hz-multi-sided-conical-midbass-horns

On that site is a link to a cool little calc prog that tells you what cut angle you need for an any number of sides pyramid...

http://jansson.us/jcompound.html

That calc was not saying 15 deg at all but 13.8!
So back to CAD pal who said "It is definitely 15° (hold down Alt + 0176) on the flat faces ... so I did a quick cut through the cone and then measured the resulting face angle - low and behold 13.886°
Didn't think to check that it would be different once off the flat surface, but of course, it will change as the slat is leaning inwards as well."



Out popped the concurring angle!

I was all set - well not quite. 13.88 deg would be hard to dial in on my trusty Wickes circ saw!

Next to mark up some wood and get cutting. I don't like waiting around...



I don't have a saw as cool as the dudes so I used this.





Here is a stack of 12 petals put roughly together...



And once glued together - no fancy clamps - I put PVA glue on all the edges and stood it up like a wigwam and worked it into position. Then put a large stretchy strap around the bottom weighted on for the base and a small one for the top.



Quite strong enough for it to fall from standing up on the thin end and twat the heavy large end on the floor and take it!


That's all for the time being... Tune in later, for more Around the horn!

 

More horns

Drivers... Having trawled the net for suitable drivers and 435Be's and 2435's being the commercial sister of the 435's I came across a pair. JBL 2435 1.5" throat, Beryllium dia and Neo mags. Nice spec and very affordable. Course, don't know how they will sound...
X/O around 800 to 1000Hz should be doable.
Plan is to start off with the Tannoy X/O'er and move on from there...

Hopefully they will arrive this coming week.

Here's a pic of what I am trying to achieve - the lovely AH-300's



Oh and some nice boxed X/Overs and stands to support them

The conical masters site - http://www.acoustichorn.com/products/300/
Personally I think those red edge addo-ons look well dodgy but like the the simpler sleek ones at the bottom / as Mr Coco has...


After a bit more (ahem, lots more) work there were 2.



Now the throat thingies are said to be pretty critical so no just bodging something up.
Need to match the 1.5" drivers and be nice and true so the temperamental little soundwaves stay well behaved as they make their bid for freedom!

AH-300's have petals that fit inside a cast ali machined throat adapter. This takes the flat slats from well, flat, to round over about 3".
I decided to do this using high tech 2 pack wood filler. This clever stuff blends into birch ply perfectly when you varnish it with mellow varnish.



Close up of throat.



Still needs final filling and throating to be pass my exacting standards but all in all I reckon it'll work.

a horn's eye view (final truing still left to do).



Apparently a rough'ish throat is good - so perhaps after first / 2nd varnish some sanded varnish like you use on sailing dinghies hull floors for grip is the ticket.
I've used that from my Mirror dinghy sailing days...

a quick snap of how they would look on the GRF's. Pre mellowed!



For those of you who followed the dedicated music room thread, Yes - the room has been changed around. Needs long speaker cables but long TNT Ubyte2's do work very well (much better than short ones for some reason) and 'we' are happier with the room like this as it means open to the patio door and you can look out + I sit close enough to the hifi rack to lean over and adjust the volume!
Cannot discern any loss in sound qual due to longer speaker cables and if anything the acoustics are better - perhaps not having a patio door behind the listening position helps?

Have to move the cave painting my daughter did for me to the other wall...

Now I await drivers to make up the fins to secure the driver to the back etc. If ever going to use Vitavox S2's then a nice birch ply machined adpater suitably threaded on my lathe to screw on to the driver would be my preferred solution. Could perhaps impreg the thread with superglue to make it super strong / hard (DIY Panzerholz...) There are many ways to skin a cat.

 

They look fantastic ! would love to hear those

 

Drivers are at the depot... Just adpaters and a bit of wiring - won't be long now...

 

Collected the drivers - tiny little things compared to the Vitavox S2 and the big mumbas of RCA that Mr Coco is currently using...
Will they do it?! All share a 1.5" throat. 2435's have a pretty shallow back compared to their consumer 435Be cousins... Perhaps they need modding to give more volume behind the diaphragm? A nice lathe spun ring of nylon or birch ply came to mind...
Anyway a bit of measuring and a few saw cuts later and the the drivers are in place. Did not want to do anything too permanent to my conicals so went for a simple clamp the driver in place.



Those thoughtful JBL people put a rubber thin gasket on so perfect to get a gas tight fit. My solution uses felt pad cushioned threaded legs to press the driver on to the throat mounting face.
Works a treat! Easy to align and very secure with M8 and threaded birch ply plate. Birch ply rules



Here's how they look from the front.



Currently sitting on blutak and books and bungie strapped down at the rear - not going anywhere...

Plan was to run them up and see... Quick look at the Lpad calc that Mr Coco sent me... 12dB to start with. Just about had the parts to make it as Farnell did not deliver the 1 ohm'ers I ordered

Some of those special clip leads and time to power up the amp having checked everything over once again.

Moment of truth...

Ok they are working. Bit more vol - pop up and stick head in horns and to bass. all doing as should. Back off and turn up a bit. Hmm sounds pretty all right actually.

Crossover is Tannoy so working ~ 1000Hz. Plenty of bass and very clear mid and treble. At vol perhaps a bit too much bass perhaps, can fix that... Back to the calc - what does 11dB need.
Hold on this is CD for test. Lets try the vinyl first then see + this is a pretty bassy CD at that...

Here they are working...



Reckon there may be a lack of mid, noticeable on some stuff. Mr Coco's measuring will tell that...
Mod the rear chamber of the drivers and roughen throat spring to mind.

Many thanks to Mr Coco for bringing his gear here for me to hear and patiently answering all my dumb questions and helping me learn along the way...
Still need help with the crossovers proper I think...

So what have we got? On the road to some pretty decent sounding horns I think, nice bass weight I can adjust, all on a very low budget indeed. Done in less than 2 weeks too.
Listening closely - you just don't hear what is coming from where, GRF or conical - that's a good thing right...

What's more the wife thinks they look nice - no telling with them is there?!

Plenty more tweaking left to do - all part of the fun!!

 

Hi Steve, looking good.
Plenty of testing done over on Lansing as to the differences between rear chambers 435/2435 -they measure exactly the same AFAIRC.
Larger chamber = better LF was one theory subsequently not supported in the freq or distortion measurements, conclusion was that it is cosmetic.
Still, might be a fun project to tackle though.
Cooky

 

Yeah been cruising there a bit. Cosmetics then = draft window dressing then!

I think custom made crossovers may improve things a bit too. Hopefully Mr Coco will bring his box of tricks and we can test away...

 

Lol looks like you need to work out a price for horn builds to go along with the cab build ME WANTS !

 

Well a total package for horns and cab would be doable - esp if you use non Tannoy 15" drivers (under investigation) and compression drivers that are all off the shelf. Reckon on £2.5 - 3K complete though!
Still that's a pair of speakers that will gun with the best I think.
Another option would be to offer kits...

 

Had a really good listening session and opened the rear chamber hole on the drivers - just the stiff JBL label to take off (without damage) and there is a hole through. This leaves the rear chamber open to the air effectively increasing the volume some think. What def made a bigger impact is positioning. You can have from hard attack in your face but oh so clear and focused to softer and more diffuse all by angle out / upwards a bit.
This meant I could down the dB damping from -12 to -9 or -10 and get more mid loveliness and better balance.

My wife sat and listened for a couple of hours - partly due to the new room having a pair of seats in the sweet spot I think and also partly she is very sensitive to anything grating and these mids do not grate at all they are very pure and non-fatiguing.
Measurements this evening will be interesting.

 

Now for some measurements...

Mr Coco was over and I think he was impressed...

Could not get his netbook to play with a driver install so we loaded the DMX_6Fire on my lappy and off it went.

Here is the JBL on it own (all are using the Tannoy crossover)



Here's the Tannoy HPD bass driver on it's own



Here's both 30 deg off axis



Here's both on axis at ear level



Yes - a little heavy on the bass so I backed the pad on the mid horn off another dB or two. Could probably try a tweeter on there too.

The bass is a bit choppy (cab / room reflections) but you hear it like that. Toning it down or rather the mid horn up may impact that a bit.

Bare in mind these graphs are not much flattened but tell it how it is - unlike most freq response curves that get published

Very happy with the result.

Thanks Mr Coco for all the help.

 

Well they are getting the cd response compensation from the Tannoy xover

Any chance you could slap a big cap on them(for protection) and rta without xover so we can see the naked horn/driver response?

Cooky

 

Not at the moment - don't have the bits...

Will be making up 3 way crossovers soon and am thinking about making a little pair of birch ply conicals for tweeters if they can go on conicals - would look pretty cool...

I aligned the drivers and must say it does sound very good indeed.

This weekend it will be dismantle and varnish and make some birch ply stands...

 

Next step is to add a couple of tweeters and build a new crossover once I have heard the Eminence bass driver.

 

Update:

Borrowed a pair of JBL Alinco mag 2405 tweeters (Mr Coco - thank you), set up and working. At first I did not think much was coming out of them but at a distance they are definitely doing their stuff and the freq response I briefly checked on pink noise seems to confirm that.

Had a fellow horn hifi enthusiast over tonight and a 2nd pair of ears confirmed there was tweeting going on and the rest does not sound too shabby

Next steps - 1. Hear BigD's Emeinences. 2. buy a pair same or similar. 3. build crossover for them. Lust over some Vitavox S2's some more and if possible borrow a pair to try them again to confirm memory of them (more crossover tweaking). If memory correct get a pair somehow....... and then relax! Yeah right!

 

Well, step 1 & 2 of the plan ticked off.

Step 1. Heard BigD's Eminence's in Berkeley cabs and what's more we plumbed my Conical/JBL2435's in to ensure the sort of X/O point I want to use with the 2435's would work. Sounded very good to me. All the Be goodness coming out and merging well with the bass. Bass was good - be interesting to hear them run in, in a pair of GRF's.
Step 2. Ordered up a pair and the bits to make up crossovers - hope they arrive soon as I hate wait once a course of action is decided;-)

 

wow steve,

completely missed this thread till now. you have been busy!

Is the plan to replace the dual concentric tannoy unit with a dedicated bass cone?

Good job by the way.

I love the fact you can knock up pretty much anything. It's cool

I absolutely love Tannoys, always have - but I soon discovered a dedicated seperate compression driver gave me what I felt was better mids. It sounds like you are finding this too - and in straight away with BE drive units and great horns. It took me ages to get there! lolol.

Well done on more excellent work

 

Yep that's the plan and now a reality.

I have dropped in some Eminence Kappa Pro 15's and am using a DIY crossover on one and the Tannoy one on t'other for the time being.

Still evaluating but it's a very immediate and accurate reproduction - pretty much like going to a gig in ones music room.
Loud without irritation or effort. The Be diaphragms do seem to suit me with a sound that is very pure, crisp and fast.
They do smokey jazz and Heavy metal no problem or as I prefer heavy rock. The bass drivers are still running in a bit but do kick well. Need to have the house to myself to really make it shake

I too have a soft spot for the HPDs and Golds but as you say there is an alt. that is alluring with immediate treble response and pure longer horn sound.

The bass is really rather good out of these Pro drivers - more evaluating needed and that is what it's all about.

Some pics to follow.

 

Rough freq measure done on my laptop mic. Proper measuring gear will be used on Monday...



This is the single Eminence kappa Pro 15" with JBL 2435 and JBL 2405 as Tweeters & low to mid X/O is for 8 Ohm drivers a 500Hz one but when measured it behaves more like 1kHz here. The 2435's reportedly don't do much below 800Hz... Both Kappa pro and JBL are 8ohm drivers but the Kappa seems to have an impedance that causes the cross over to work higher up the freq range.

If I move about the room then peak and troughs move about so don't read to much in to the ups and down at the moment.

This is from where I sit - Bass heads unite - sounds nice from here. Bass guitars really do sound like bass guitars - well so they should with Pro bass guitar drivers in GRF cabs but really it is not too much or out of hand IMO.
The treble part would be higher with the mic 1m / level with the horn. Perhaps it would be flat - have to wait until Mr Coco come round kindly bringing his measuring gear.

Keep in mind this was just my laptop with crappy lappy mic from where I sit cos' the lead ain't any longer and done out of curiosity more than anything.

Looking forward to lots of session with it turned up loud - this rig does loud much easier tbh.