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Old 29th November 2013, 04:54 PM   #171
Rewind is offline Rewind  Sweden
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How could I have missed this thread.

Great to know the difference between conicals and tractrix, and also beryllium diaphragms vs aluminum diaphragms as in the S2.

My current problem is a mismatch in sound in the aluminum diaphragms of the Yamaha JA6681B and the paper cones of the 12" JBL 2202H. I just ordered some aluminum dust caps and hopefully these will do the trick.

Also, I am looking for a good midbass horn for them. I am thinking a horn much larger than yours would be preferable, to reach 80Hz.

I would also prefer to have everything on passive - buying five more SETs is a drag. But I guess a 5-way is too complicated for 2nd order passive XOs. The Minidsp 4x10HD sounds good, but not good as it would analog.
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Old 29th November 2013, 07:30 PM   #172
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I know what you mean about missing interesting threads... I would have never seen this awakening were it not for an email notification.

Yes, even a few extra Hz bass extension needs bigger, bigger, bigger.

After many months of WAF Najda X/O I am really impressed with it - well bloody revelation acutally, once I went to my hybrid mode

The support from Charpark on this forum has been excellent.

I've spread the world and a couple of us multi horn users have them now, and are happy.

Passive all the way down is tough... Things are so much more controlled, punchy and impressive with DSP on the bass channels.
I actually use a hybrid of DSP and passive - thus:

Tapped horns subs - DSP 4th order with some room correction
Mid Bass horns - DSP - 4th order / 2nd order with a tiny amount of room correction.
Mid horns - DSP no correction
Upper mid horns - 1st order passive (no upper slope) and running through the DSP with no X/O in play
Tweeter ribbons - 1 st order passive (no upper slope) not running through the DSP but on own amp, time aligned physically to upper mid horns.

Lower 4 channels time aligned in DSP domain.

This gives the best sound I've found so far.

Here's how it looks now with wider horn placement.

Click the image to open in full size.

MVH Steve

Last edited by Speedysteve7; 29th November 2013 at 07:35 PM.
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Old 29th November 2013, 09:21 PM   #173
Rewind is offline Rewind  Sweden
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It is so easy to get stuck in the digital XO world, and not finish that analog active XO master piece.

How do you think Minidsp 4x10HD measure up to the Najda? Seems to be the same thing. Only yours is cheaper to buy. I am not fully satisfied with the sound of the Minidsp. You mentioned earlier how digital XO has bad sounding cymbals and I can hear where this comes from, both on the Tranmission Audio true ribbon and a Beyma TPL-150 Air Motion Transformer tweeter.

I also heard from a friend how FIR can really sort out bass and midbass, but I have not yet understood it. FIR is a heavy subject.
It is a moment 22. If I remember correctly, Romy wrote something about how digital XO can reduce resolution/bitrate, especially for bass, but it this is the area where digital room correction can really of good use.
I would prefer to just treat the room acoustically and use analog components in the XO. It will end up looking like a white padded room at a mental asylum.

I will have three channels with three identical pairs of JA6681B compression drivers, and I would like these to be passive, so that I can use one single 45 SET amp for all of them at once. If the six drivers are all identical, designing a working passive 3-way XO, within the minidsp or any future analog active XO, should not be so difficult. I will however, use some kind of inductor, 1st order or 2nd order, to reduce high frequencies for the two lower compression drivers. I have tried no limit and it does not sound good, especially on the two largest compression driver horns. The smaller AG Trio tweeter horn does not seem to care. The JA6681B is practical that way - it dies off at 12kHz before compression drivers usually start to sound harsh and annoying.

Midbass can have an okay EL84 amp, because the JBL 2202H is an old instrument speaker anyway. There is a pretty large mismatch in sound between 45 and EL84 tubes, but this will have to do for now. I doubt the 45 amp is powerful enough for the JBL 2202H anyway. I am still working to find the best horn for it. I am even building a 55" wide x 61" deep x 22" tall biradial horn. Why not, ey? I am dumbfounded when it comes to midbass. Better try everything.
When I first saw the size of your midbass horn I though "He won't get passed 110Hz with those", but apparently you did. I wonder though, if it is acting like a horn driver or a direct radiator all the way down to 80Hz.

Summary of my system:
25-80Hz LAB12 subwoofer, in horn, or without. Will have its own analog out channel from the Minidsp or analog active XO.

80-340Hz JBL 2202H, soon with custom alu dustcap (still prototyping horns). Will have its own analog out channel from the minidsp or analog active XO.

The following three channels will hopefully share a passive XO that divides the signal from one digital out channel from the minidsp, that goes into a higher quality DAC and uses a fancy 45 SET tube amp.
340hz-~1000 Yamaha JA6681B in large custom made horn (still prototyping horns)
~1000-3500Hz Yamaha JA6681B in large custom made kugelwellen inspired by AG Trio midhorn
3500Hz-9000Hz Yamaha JA6681B in large custom made horn inspired by AG Trio tweeterhorn

9000-30 000Hz Transmission Audio 50cm true ribbon with RAAL trafo in custom horn. Will have its own analog out channel from the Minidsp, but I fear the cymbals will suffer greatly. Analog active XO would be preferred! This true ribbon is not as sensitive as the rest of the compression drivers and JBL 12". I am not sure yet what amp they like. This channel is somewhat of a mystery and it not in use yet.

I have found 2nd order to be good for everything except the LAB12 sub which seems to like LR24, for some reason.

I am guessing you are doing something similar. Are you still crossing a pair of crompression drivers down to ~340Hz? I have found an extreme way of doing so, using a replica of AG Trio's largest horn with a 4" to 1" adapter-extension. It is most certainly too big, but it sounds magical. I may reduce it slightly with wall paste. It is hornloading so low into the midbass area, that it is giving me a headache when I am trying to match that clarity of sound with a paper cone 12" JBL driver.

Your ribbon channel is the completely passive one? I could do this for my own ribbon.

Oh, and ignore the midbass horn with the oak rim in the picture. It is slowly being replaced with something larger. 4" throat was not enough for a 12" JBL driver.

//Rewind
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Last edited by Rewind; 29th November 2013 at 09:51 PM.
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Old 30th November 2013, 02:02 AM   #174
Rewind is offline Rewind  Sweden
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Turns out if I start preparing for a DSP-less lifestyle I can save some money on SET amps.

What can you tell me of this hypothetical solution?

BTW, how can you have a clean signal that does not go through the DSP unit for your ribbon tweeter? Do you start out with analog, convert it to digital and then analog again? This would be very deteriorating for the signal.

//Rewind
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Last edited by Rewind; 30th November 2013 at 02:24 AM.
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Old 30th November 2013, 02:47 AM   #175
Rewind is offline Rewind  Sweden
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I was also wondering about your midbass horn, since I am in the situation where I don't really know what I want here.

I think this type of horn works best with a larger driver, like an 18" or 15", because for it to work down to 80Hz, the throat need to be so big that it starts to work like a direct radiator. There is no reason to put a direct radiator behind a tiny hole - so lets keep it open!

I have started from another angle - the 8" Fane Studio 8M drivers. I first began with the AG Trio midbass horn - it sounded more like a waveguide than a horn. The next horn I built is in fact the same size as yours, around 80cm in diameter, 1.1m deep, but it has a smaller 4" throat. The signal is hornloaded down to 150 or 200Hz, which is perfect for a 6.5" or 8" driver. The drivers suitable for hornloading in that size usually don't offer much midbass around 80Hz. To get down to 80Hz I needed a driver like the 12" JBL 2202H, but for it to sound good, I would need to open the throat to your size. I will do so, but I will also need a much larger mouth and depth.
Am I all wrong? I really hope so, because I will have trouble fitting the only horn that I think would do the job.

It will probably not be the funny looking biradial midbass horn. After reading how the edgy looking conical horn sounded compared to the smoothly rounded off midbass horn you have now, I will be very careful of any designs that stray from the idea of smooth round horns.

About placement. I think proper hornloading is more important than perfect on axis listening. Some say it might be even better to place midbass horns closer to each other, probably so that they can pump the same air together.
I base this on someone who had previously been listening to Western Electric 15A horns using WE 555 that reaches 100Hz. When listening to a pair that stood close to each other they apparently sounded much better then the pair that stood far apart on a Hifi convention. He was convinced that this was the reason.

I have heard the same thing about Labhorns, that if you are not planning on building six of them, but just two, then forget about it.

Still, I am just guessing. Despite all my horns, I have not heard hornloading below 110Hz yet.


Rewind
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Last edited by Rewind; 30th November 2013 at 03:15 AM.
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Old 30th November 2013, 06:50 PM   #176
halo71 is offline halo71  United States
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Wow! I missed this thread as well. Truly amazing build Steve! I showed the pics to my wife. I told her "see, I could have something like these sitting in the den". lol I think she appreciates the big box Infinity's more now!
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Old 17th December 2013, 01:04 PM   #177
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Soz guys, been away from this one for a while...

Yes to the big throat. When I modelled the exponential mid bass it was saying use a smaller throat. I found by measuring and trial and error (enlarging the throat bit by bit) that I liked the sound better with a larger throat. we are talking a couple of centimeters or so - can't remember exactly.

Below 100Hz you need tapped horns. They are fast and subtle but do not dominate or unbalance things - in my system at any rate.

Every man needs some massive horns in his den
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Old 19th December 2013, 05:40 AM   #178
Rewind is offline Rewind  Sweden
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Quote:
Originally Posted by Speedysteve7 View Post
Soz guys, been away from this one for a while...

Yes to the big throat. When I modelled the exponential mid bass it was saying use a smaller throat. I found by measuring and trial and error (enlarging the throat bit by bit) that I liked the sound better with a larger throat. we are talking a couple of centimeters or so - can't remember exactly.

Below 100Hz you need tapped horns. They are fast and subtle but do not dominate or unbalance things - in my system at any rate.

Every man needs some massive horns in his den
I read about several people who preferred other solutions after trying tapped horns, but I don't know yet. I will focus on the upper part of the bass and make a slightly shorter horn than a tall tapped horn, using a J horn. See pic of my unfinished J horn. It is missing the large mouth that is angled towards the listener. The tube looking thing will go on top of the triangle shaped mouth in the background.

For midbass I will also try a larger horn throat. I would like it to be large but when paired with the J horn below it might not have to be. Maybe a too large mouth on a midbass horn, like a WE 15A, will make frequencies around 200-1000Hz sound wrong.
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Last edited by Rewind; 19th December 2013 at 05:51 AM.
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Old 12th January 2014, 05:21 PM   #179
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Default DIY made 550Hz tractrix horns for my Vitavox S2's

The next twist in the tale.

I've set about making a pair of 550 or so Hz tractrix horns for my Vitavox S2's.

A bit of modelling in Hornresp to give the dimensions and also comparing with the ~600Hz Cube Audio GRP ones I currently run.
I've decided to use birch ply as I have lots of it and it's nice to work with.
6 rings of 24mm birch ply will do it. I cut these out today and they are gluing clamped up overnight.

The next thing was to make decent throat adapters. I lashed up some interference fit birch ply ones for the Cube Audio horns but want to do it right for these.
This means cutting in internal 2.620" diameter thread. 16 Threads Per Inch pitch, Whitworth (55 degree and correct radius etc).
There was a pair of these mounting rings in aluminium on ebay for 125 ouch! - and where would be the fun in just buying them...

I won't bore you with the need for an imperial lead screw / correct change gears on the lathe to cut the perfect thread, or the test cuts I made.

I am using my Super Mini Lathe as the correct change gears for 16TPI are not readily available for my bigger South Bend 9A lathe.

For this I decided to try some composite PVC sheet as the material - Cheap, strong, easy to cut and drill etc.
Here's a sized piece

Click the image to open in full size.

As I don't have a 4 jaw chuck (yet) for my Super Mini Lathe I used the mounting plate (the old fashioned way), with a ply spacer which can be 'cut' into so the cutting tool can cut all the way in and not hit the mounting plate.

Click the image to open in full size.

6 screws for good location

Click the image to open in full size.

Mounted up on the lathe ready for making round

Click the image to open in full size.

Rounded and inner hole cut

Click the image to open in full size.

Getting the ID sizing right using the internal cutting tool

Click the image to open in full size.

The cutting tool is then run forward at slow rpm cutting the thread. About 6-8 cuts are needed depending on material. Keeping the saddle 1/2 nuts engaged and using the neat reverse feature of the mini lathe's DC motor thread, cutting is easy.

Checking that the S2 actually fits

Click the image to open in full size.

Click the image to open in full size.

Here is the mounting ring screwed on flush (this will be countersunk and screwed onto the horn throat flange)

Click the image to open in full size.

I am very pleased how easily and precisely the thread matches / fits.
This is the first one - the next one will be even better. As you can see there is some tearing of the material at the very start - I made a too fast / too deep cut. The rest of the thread is nice though as I backed off.

As the horns will be small and pretty light these mounts will be plenty strong enough.

Next up the horns themselves - for this I have to use the bigger 9" swing vintage South Bend 9A lathe... TBC.
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Old 12th January 2014, 06:25 PM   #180
Squeak is offline Squeak  Denmark
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All that time and effort, and you'd think you'd have wanted to change the curtains. :-P After all it what you are looking at when it dark outside.
Really really impressive, and nice touch with the clocktower bass horn.
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