Adding a ribbon tweeter to an Alpair 6.2m

[grahamgraham]

Hi all,

I've recently built a couple of Woden Designs Sasquatch full range with some great help and support from Dave, Chris and Scott:

http://www.diyaudio.com/forums/full-range/317942-alpair-6m-cyburgs-needle-br-design.html

These sound good but I still need to tweak. What I planned for these drivers was versatility so I could use them for a few projects (mains, surrounds and multi way - MLTL and BR). One I'd like to try is to use this as mid bass and add a tweeter to get a wider stereo stage.

I'm thinking about ribbon tweeters and don't have too much to spend. About £150. I have a Behringer active crossover rack unit which I will use for the crossover before I progress to making as passive crossover.

Which tweeters would pair well with this driver? I have found two that look like likely candidates but I am new to multi range so I am not aware of the immediate pitfalls of driver selection. If there is an article someone can recommend then great. If someone can shed a bit of light even better.

Fountek Ribbon NeoCD 3.5H Size 110x98mm

Monacor RBT-35SR Size 110x98mm

I plan to place them on top of the Alpairs MLTL in free air. Would there be an issue with this?

Any advice would be great, thanks!

 

[bbe22]

You do realize that same as ........
Vauxhall / Opel ......you are pointing to 2 products essentialy the same thing ??

 

[grahamgraham]

No, I didn't. Perhaps this is the first education. The shame the shame.

You do realize that same as ........
Vauxhall / Opel ......you are pointing to 2 products essentialy the same thing ??

 

[grahamgraham]

No, I didn't. Perhaps this is the first education. The shame the shame.

The specs are similar but I assumed they used the same premade horn.

 

[Bigun]

Hi GrahamGraham,

I think you're barking up the wrong tree. Something doesn't seem right to me - looking for a tweeter to add to cones that are designed to go past your ability to hear - i.e. at least 20kHz. I don't think there's any issue with your Alpairs in terms of treble.

I think stereo imaging is a fairly complex topic, but have you messed around with the positioning of your speakers and listening chair for starter ?

I've heard a pair of Alpair 10.3 in the Pencil boxes and the imaging was absolutely spooky, the best I have ever heard of any pair of speakers so far (driven by a SET amplifier). Interestingly, my experience was that the stuffing of the cabinet made a slight difference - not sure why, perhaps something about mid-treble leakage out the port, or re-radiating through the driver cone, but there was an optimal stuffing level for bass response and an optimal stuffing level for imaging and they were close but not exactly the same in terms of stuffing. I think there's a lot more tweaking you can do, possibly saving yourself a frustrating journey.

 

[planet10]

Graham, what is the rest of your system?

dave

 

[grahamgraham]

HI, thanks for your input. Sorry, I should have been more explicit. I intend to use these drivers to learn various different methods of speaker design. Also, I really like the Alpairs but they don't make for good listening for more than 1 person so I thought adding a tweeter would make things wider.

I would like to learn how crossovers and tweeter integration works.

I have tried several positions for the MLTLs and the position in the photos is not the best one I have found so I am confident I have got them in the best position for imaging.

Hi GrahamGraham,

I think you're barking up the wrong tree. Something doesn't seem right to me - looking for a tweeter to add to cones that are designed to go past your ability to hear - i.e. at least 20kHz. I don't think there's any issue with your Alpairs in terms of treble.

I think stereo imaging is a fairly complex topic, but have you messed around with the positioning of your speakers and listening chair for starter ?

I've heard a pair of Alpair 10.3 in the Pencil boxes and the imaging was absolutely spooky, the best I have ever heard of any pair of speakers so far (driven by a SET amplifier). Interestingly, my experience was that the stuffing of the cabinet made a slight difference - not sure why, perhaps something about mid-treble leakage out the port, or re-radiating through the driver cone, but there was an optimal stuffing level for bass response and an optimal stuffing level for imaging and they were close but not exactly the same in terms of stuffing. I think there's a lot more tweaking you can do, possibly saving yourself a frustrating journey.

 

[grahamgraham]

I have two Tang Band 6.5" sealed subs running from an iNuke amp going via MiniDSP for room correction. I have a HiFImeDIY amp for the Alpairs but I intend to invest in a second amp of some sort to accommodate either the tweeters or the alpairs.

The rest of my set up is Genelec 1029a for HT duties.

I also have the Behringer active crossover at my disposal.

Graham, what is the rest of your system?

dave

 

[Bigun]

Without the benefit of direct experience my guess is that the tweeter will not give you much and may cause problems with good imaging due to the separation of the driver acoustic centres at high frequencies where the sound has a short wavelength and is therefore much more sensitive to driver distance. As you are open to suggestions - mine would be to go in the direction of using the A6.2 as a mid-tweet and add a supporting high quality woofer that is known to have a smooth roll-off at high frequencies (a 6" to 8"). This will relieve the A6.2 of LF stress which will reduced distortion and improve it's performance, leaving it to do the job it's best at which is the mid and highs. Build new cabinets, larger front baffle, moving the edge diffraction further from the driver cone. I would consider designing the cross-over frequency to coincide with the baffle step of the box.

 

[eirik hansen]

The listening 'window' can also be enlarged with severe toe in, crossing in front of the listening position.

 

[planet10]

Have a good play. The rbbons like that are good, but as Bigun says, physical separation & an XO may bring more issues than they solve, but since you are doing this to learn, i encourage you.

Imaging/soundstage is something that is very important to us. The Alpairs are image kings, but then we are much more familiar with EnABLed versions which ar enotable by improvements in imaging.

We haven’t yet used A6 as a midTweeter but they should be excellent.

dave

 

[chrisb]

I've heard most Mark Audio drivers in a range of enclosures and applications, and the only two that come to mind that would need any assistance in extension in the top end are the A12PW and CHP70 Gen2. The former was intended as a woofer, and the latter was IIRC tailored for a particular "classic" FR tonal balance - it is definitely soft in the top octave, while the A6M are to my ears, certainly not.

 

[oon_the_kid]

I have tried something similar on a Faitalpro 3Fe22. I haven't tried on my markaudio 6.1. What u found is it actually sounded worse. The treble becomes disembodied with the main driver due to loss of coherence. As the wavelength is very short (only a few cm) the phase shift is quite severe. However I have very good results pointing it backwards as a rear facing tweeter. It adds in a lot of ambience and increases the Soundstage. A lot of hifi manufacturers uses that approach.
Such as this one. Since the front already reaches over 20Khz. The position the tweeter at the back in between the binding posts.

6moons audio reviews: Boenicke Audio W5

Hope that helps.

Oon

 

[oon_the_kid]

I also forgot to add that ribbon tweeters generally require 4th order crossover. So best to use your behringer dsp for the tweeters. You can also add in a delay... 30 ms to your tweeter, which makes the rear wall 5metres further away.

Oon

 

[grahamgraham]

Hi all, thanks for the input but just to clarify - I do not want to add a tweeter. I want to use the Alpair as a mid bass, insert a crossover and replace the top end of the alpair with a tweeter. It's an excercise in learning mid/tweeter crossovers. I did mention this in the first post.

Dave, thanks, I think I will play. As I used the second position in the Sasquatch that is higher up the cab I feel that there shouldn't be too much mismatch when it comes to distance and sitting the ribbon tweeter on the top. But I guess I'll see!

Perhaps someone can help with the title as it is a bit misleading? Like I say, this is my first dabbling in multi way.

 

[planet10]

there shouldn't be too much mismatch when it comes to distance and sitting the ribbon tweeter on the top.

You ar egoing to be limied to about a 3k XO. At 3k a quarter wavelength is 1.13” = 29mm. Half the height of the ribbon is 55mm. Add another 57mm for the A6 and you are already 4x as far apart as ideal.

dave

 

[Juhazi]

I have used the Fountek 3.5H version myself. It has nice sound but dispersion is so narrow that it is good only for the person in the spot.

Matching horizontal off-axis sound radiation is very important when designing multi-way speakers. Vertical lobing because of separation is overrated in my experience. With LR4 xo around 4-6kHz you must play only that xo ferquency sine to hear it! Most 20.000$+ hifi-speakers break the rule as well!

Dsp is a good toy for this kind of prototyping and testing. But you must do measurements to set acoustic responses and delay right. With delay setting you can point the vertical interference null a bit downwards, then it is very hard to notice! This applies to any kind of speaker systems!

Don't just measure, listen to different settings too! Then you wil learn how a specific measured response sounds. Making deliberate "mistakes" is also good for learnig to identify problems by listening.

 

[grahamgraham]

Hey, thanks. So, if this is a very directional tweeter is there one that is known for being wide? I have noticed in lots of other ribbon designs that the distance from the woofer and tweeter is quite a way, is this something that people tend to blissfully overlook?

I have used the Fountek 3.5H version myself. It has nice sound but dispersion is so narrow that it is good only for the person in the spot.

Matching horizontal off-axis sound radiation is very important when designing multi-way speakers. Vertical lobing because of separation is overrated in my experience. With LR4 xo around 4-6kHz you must play only that xo ferquency sine to hear it! Most 20.000$+ hifi-speakers break the rule as well!

Dsp is a good toy for this kind of prototyping and testing. But you must do measurements to set acoustic responses and delay right. With delay setting you can point the vertical interference null a bit downwards, then it is very hard to notice! This applies to any kind of speaker systems!

Don't just measure, listen to different settings too! Then you wil learn how a specific measured response sounds. Making deliberate "mistakes" is also good for learnig to identify problems by listening.

 

[grahamgraham]

So a smaller tweeter would reduce the distance thus making integration more likely to succeed?

A dome tweeter would do this. Are there any particularly wide or good ones for little £$. I have read the Zaph Audio tweeter run down but there aren't many he recommends that are either out of production or hard to get hold of in the UK.

You ar egoing to be limied to about a 3k XO. At 3k a quarter wavelength is 1.13” = 29mm. Half the height of the ribbon is 55mm. Add another 57mm for the A6 and you are already 4x as far apart as ideal.

dave

 

[Juhazi]

I took the 3.5H horn off and presto - very wide lateral dispersion! Vertical stays practically the same.

For minimal c-c distance and high xo, 3/4" neodyme tweeters that come without a flange/plate are the best. An example
Dayton Audio ND20FA-6 3/4" Soft Dome Neodymium Tweeter

My measurements of Fountek NeoCD3.5H outdoor in a narrow baffle with xo and indoor without the horn in a normal baffle (less distance) Both 5ms.