Horn Loading RAAL Ribbon Tweeter --- Full Measurement Comparison

[Joseph Crowe]

@Joseph Crowe
Is there any benefit to a horn for the 5" woofer (or a 4" one)? I thought I saw something on your website with that approach. Mainly, I was thinking it might help match dispersion to a lower frequency. But maybe lower frequencies are too omnidirectional to be affected.

The best midrange I’ve been able to achieve is when it’s used in a large format front horn that provides controlled coverage down to 400Hz. However the horn ends up being at least 50cm wide to achieve this. The other challenge is integrating the tweeter. You can either put the tweeter in the midrange horn or you can use the NEO8 planar which covers 200Hz-20KHz all on its own.

 

[Joseph Crowe]

Honestly, I'm not so sure how much I trust the research that suggests wider directivity is better. The Salon 2 vs M2 blind really swayed me. The M2 was basically better in every way, yet it still lost because it had narrower dispersion. However, more and more, lately, I seem to be shifting towards preferring more narrow (and controlled) dispersion designs.

Like you said, those speakers in that test were different in many ways outside of just their dispersion widths. I think it's ok to say that the wider dispersion speakers were preferred, but it's not ok to say that they were preferred because they were wider. For a conclusion like that, I would think you would need speakers that were identical in every way except for their dispersion width.

Dispersion width preference is the aspect of speaker design I'm most interested in atm, and I'm here to learn. It seems like there are different opinions. Do you think this waveguide improves this tweeter in most loudspeaker designs? What about a speaker like the BMR?

The BMR has excellent off-axis performance as well. It then comes down to individual preference. There’s no right or wrong. I enjoy both. With ultra wide speakers I need to make sure my room’s acoustics are treated for flutter echoes and that there’s plenty of diffusion. The end result is great soundstage depth and width. However if I want to hear miles into the recording then more controlled coverage would achieve that.

 

[Ericglo]

Honestly, I'm not so sure how much I trust the research that suggests wider directivity is better. The Salon 2 vs M2 blind really swayed me. The M2 was basically better in every way, yet it still lost because it had narrower dispersion. However, more and more, lately, I seem to be shifting towards preferring more narrow (and controlled) dispersion designs.

Like you said, those speakers in that test were different in many ways outside of just their dispersion widths. I think it's ok to say that the wider dispersion speakers were preferred, but it's not ok to say that they were preferred because they were wider. For a conclusion like that, I would think you would need speakers that were identical in every way except for their dispersion width.

Dispersion width preference is the aspect of speaker design I'm most interested in atm, and I'm here to learn. It seems like there are different opinions. Do you think this waveguide improves this tweeter in most loudspeaker designs? What about a speaker like the BMR?

I haven't done the comparison, but I am thinking that for home theater a more controlled dispersion is preferable.

 

[KaiserSoze]

What does the polar response in the vertical plane look like? It would be interesting to see it in both the color chart and the waterfall. How does the vertical spacing between the woofer and the tweeter compare for the two designs? About the same, or different enough to produce a significant difference in the polar response for the vertical plane?

 

[Chromatischism]

The BMR has excellent off-axis performance as well. It then comes down to individual preference. There’s no right or wrong. I enjoy both. With ultra wide speakers I need to make sure my room’s acoustics are treated for flutter echoes and that there’s plenty of diffusion. The end result is great soundstage depth and width. However if I want to hear miles into the recording then more controlled coverage would achieve that.

Many people overlook matching the speaker to the room. For small, narrow rooms, controlled directivity with matching on-and-off axis sound becomes critical. If the distance to the side walls can be measured in tens of feet, it's not as important. There, direct sound will become more important.

 

[Lbstyling]

Mr crowe!

Good to see you here.

I am a subscriber of yours on YouTube.

I myself am playing with a JMLC 350hz profile horn mated to a JBL2452SL driver for the top end, crossed over to a AETD10m 10 inch bass driver.

You. An get away with a lot when you get the crossover down to 400hz.

Your comments on directivity are interesting to me. I'm about to get a OSWG profile constant directivity 350hz horn for my system for evaluation which is much wider pattern than my current horn at the top end.

Considering the price, we really need a BMR based CBT speaker (or similar ) from you next

You know, just in your spare time

 

[Joseph Crowe]

Mr crowe!

Good to see you here.

I am a subscriber of yours on YouTube.

I myself am playing with a JMLC 350hz profile horn mated to a JBL2452SL driver for the top end, crossed over to a AETD10m 10 inch bass driver.

You. An get away with a lot when you get the crossover down to 400hz.

Your comments on directivity are interesting to me. I'm about to get a OSWG profile constant directivity 350hz horn for my system for evaluation which is much wider pattern than my current horn at the top end.

Considering the price, we really need a BMR based CBT speaker (or similar ) from you next

You know, just in your spare time

Let us know how the Oblate Spheroidal horn sounds. I’ve only done a few OS horns. I could possible do a hybrid OS+ES horn to see the results...maybe call it SEOS...oh no that won’t work! . There’s strong rationale for the wide pattern of OS. I struggled with proper loading and with dips in the response at 10kHz...first order reflections in the throat? I’m not sure. Are you doing the foam Gedes style?

 

[Lbstyling]

Let us know how the Oblate Spheroidal horn sounds. I’ve only done a few OS horns. I could possible do a hybrid OS+ES horn to see the results...maybe call it SEOS...oh no that won’t work! . There’s strong rationale for the wide pattern of OS. I struggled with proper loading and with dips in the response at 10kHz...first order reflections in the throat? I’m not sure. Are you doing the foam Gedes style?

Yes foam in current JMLC horn. I will see when it comes to the OS (or alternative) what works.

Foam has actually turned out to be very useful for EQ purposes for me. It rolls off the top end the more you add, smooths out the mid range peaks and dips though too, so I use it to 'tune' both of those a little.

Having hypex fusion amps makes it easy to make A/B comparisons on the fly. Adding foam makes it sound ...dryer? Even when EQed identical.

Pattern width is a controversial subject (to say the least!)

I take it the dips at 10khz you run into are not linear off axis then?

I'm personally a bit stuck. My JMLC measure extremely smooth, but gets narrower at above 10khz, so the 'sweet spot' is reasonably narrow Vs ideal. Perhaps I should try to 3D print a mount for a super tweeter to go in the horn somewhere. I would have to find an extremely small and excellent measuring tweeter to try that mind, then figure out where it would do the least damage to the FR without being too far away from the center....hmm.

The Dayton nd16-FA6 is very cheap. Most sure what the max SPL is like though.

I could 3D print a holder for it and place it near the middle of the throat in the position of the photo attached.?

Regardless, I'm not sure I can match what the JMLC can do with the hyper detailed way it sounds with so much of the early reflection removed. (Being narrow)

I think I have to purchase a pure CD horn to evaluate what the trade offs are. The M2 horn will fit my driver, so there's an alternative, all be it a rather expensive one!

 

[Joseph Crowe]

Yes foam in current JMLC horn. I will see when it comes to the OS (or alternative) what works.

Foam has actually turned out to be very useful for EQ purposes for me. It rolls off the top end the more you add, smooths out the mid range peaks and dips though too, so I use it to 'tune' both of those a little.

Having hypex fusion amps makes it easy to make A/B comparisons on the fly. Adding foam makes it sound ...dryer? Even when EQed identical.

Pattern width is a controversial subject (to say the least!)

I take it the dips at 10khz you run into are not linear off axis then?

I'm personally a bit stuck. My JMLC measure extremely smooth, but gets narrower at above 10khz, so the 'sweet spot' is reasonably narrow Vs ideal. Perhaps I should try to 3D print a mount for a super tweeter to go in the horn somewhere. I would have to find an extremely small and excellent measuring tweeter to try that mind, then figure out where it would do the least damage to the FR without being too far away from the center....hmm.

The Dayton nd16-FA6 is very cheap. Most sure what the max SPL is like though.

I could 3D print a holder for it and place it near the middle of the throat in the position of the photo attached.?

Regardless, I'm not sure I can match what the JMLC can do with the hyper detailed way it sounds with so much of the early reflection removed. (Being narrow)

I think I have to purchase a pure CD horn to evaluate what the trade offs are. The M2 horn will fit my driver, so there's an alternative, all be it a rather expensive one!

The struggle is real. My solution is a small 3-way.
The Biradial horns provide close driver spacing with 600Hz and 4Hz crossover points. The horns are carefully sized to match coverage at the crossover points. This results in constant directivity and 100 degree coverage even in the upper treble. Subjectively the sound is just “right” with great soundstage width, or “perceived source width” ala Toole terminology.

Frequency response overlay...

Resulting Off-axis polar map for the midrange + high frequency horn...

A regular 29mm dome tweeter will have about a 60degree listening window at 15kHz. This solution provides much wider coverage at 100degrees coverage. So it’s providing the opposite of what most would suspect for horns...it’s controlled coverage but the coverage is nearly twice as wide than a traditional dome tweeter!

 

[Lbstyling]

The struggle is real. My solution is a small 3-way.
The Biradial horns provide close driver spacing with 600Hz and 4Hz crossover points. The horns are carefully sized to match coverage at the crossover points. This results in constant directivity and 100 degree coverage even in the upper treble. Subjectively the sound is just “right” with great soundstage width, or “perceived source width” ala Toole terminology.
View attachment 72004
Frequency response overlay...
View attachment 72005
Resulting Off-axis polar map for the midrange + high frequency horn...
View attachment 72006
A regular 29mm dome tweeter will have about a 60degree listening window at 15kHz. This solution provides much wider coverage at 100degrees coverage. So it’s providing the opposite of what most would suspect for horns...it’s controlled coverage but the coverage is nearly twice as wide than a traditional dome tweeter!

It's the solution that. Most end up with it seams.. however, the price is the vertical polar.

Does the vertical matter less- yes! Does it not matter at all though.....?

I don't know the specific data on this. That's why I don't plan to add a horn above myself, and my crossovers are STEEP. (8th order).

Off axis, above and below, the less area you have 2 drivers playing, the more consistent the vertical polar.

Not that I don't think for one second that your system doesn't sound way better than mine probably does right now!

(That's a great horizontal polar BTW!)

The other thing I'm investigating is the 'denovo CX15' coax driver.

Check this thing out...

That's 0-90 degrees! Pretty impressive I thought.

I have asked for distortion data. Nothing through yet.

 

[Joseph Crowe]

I’ve revised my distortion sweeps with a new diaphragm that’s been tensioned according to the RAAL procedure. Maximum SPL increased from 85dB to 100dB depending on the crossover point. More details available here.

 

[HooStat]

I also see that you are building a transmission line floor stander with the Purifi 6.5" woofer. Can't wait to hear more about that. Would the revised RAAL tweeter work in that application?

 

[AnalogSteph]

@Joseph Crowe, your distortion measurements always appear to be (white) noise limited at around the 60 dB SPL mark. Now I am not familiar with how good the ARTA algorithm is, but that seems quite high to me.

It appears you're using a Dayton UMM-6? Then I'd be checking the input gain setting. This may be turned down to 0 dB by default, but according to the datasheet even the +30 dB setting would still provide you with a 0 dBFS SPL of 113 dB SPL, which I imagine should get the job done in most cases. At this setting, you should be seeing a noise level of 43 dB(A). (Pretty noisy thing, really, though not unheard of in the world of measurement mics. That's a nominal SNR of 51 dB(A) ref. 1 Pa.)

 

[Lbstyling]

I’ve revised my distortion sweeps with a new diaphragm that’s been tensioned according to the RAAL procedure. Maximum SPL increased from 85dB to 100dB depending on the crossover point. More details available here.

That's a huge increase!

 

[Joseph Crowe]

@Joseph Crowe, your distortion measurements always appear to be (white) noise limited at around the 60 dB SPL mark. Now I am not familiar with how good the ARTA algorithm is, but that seems quite high to me.

It appears you're using a Dayton UMM-6? Then I'd be checking the input gain setting. This may be turned down to 0 dB by default, but according to the datasheet even the +30 dB setting would still provide you with a 0 dBFS SPL of 113 dB SPL, which I imagine should get the job done in most cases. At this setting, you should be seeing a noise level of 43 dB(A). (Pretty noisy thing, really, though not unheard of in the world of measurement mics. That's a nominal SNR of 51 dB(A) ref. 1 Pa.)

It’s the MiniDSP 2x4 creating the noise floor. I had no other alternative to ensure I protected the tweeter for this type of test.

 

[Joseph Crowe]

I also see that you are building a transmission line floor stander with the Purifi 6.5" woofer. Can't wait to hear more about that. Would the revised RAAL tweeter work in that application?

If using a 2KHz crossover point the maximum SPL of the RAAL is 95dB. Pushing it up to 2.6kHz yields another 5dB. Personally I’d like to see another 5dB of headroom overall to match the PTT6.5. Perhaps the Viawave Ribbon on a horn would achieve this. Also, the 1198 baffle design could be changed to accommodate horn loaded ribbon.

 

[Lbstyling]

Nice! Looking forward to your views on the purefi driver.

 

[hvbias]

There is also Klipsch K-402 which controls directivity down to ~ 400 Hz with a wide bandwidth compression driver (people tend to use TAD) there is no need for a tweeter. The issue is it's absolutely massive, the K-402 on the right next to a Cornwall.

 

[Chris A]

Unless you're going to use diffraction to try to control directivity, like a line array, the mouth size of the waveguide/horn (horizontal, vertical) must be ~half wavelength of sound at the lowest frequency that you're attempting to control directivity. For the K-402, that number is 170 Hz horizontally. If you're willing to move that up to ~600 Hz, you can use a much smaller horn, but the loss of vertical/horizontal directivity at lower frequencies takes away the real performance of the loudspeaker. I think most people don't know what they're giving up when they make the decision to lose directivity at a much higher frequency than the room's Schroeder frequency (for home hi-fi applications, of course). Most people have never heard what happens when you use horns/waveguides that don't lose pattern control. It's a very big deal.

people tend to use TAD

Not really. I've only dialed in perhaps 3-4 installations of Jubilees using TAD TD-4002s (no longer in production) out of the perhaps 2-3 dozen Jubilee dial-ins that I've done. The rest seem to be a mixture of FaitalPRO HF20ATs, HF200s, B&C DE75s (modified phase plug to bring it closer to the pole piece, and with the Klipsch K-691 sticker on them), and Radian 950PBs (not the BE diaphragms). I've also dialed in a few JBL 2" compression drivers, but these all seem to have issues with diaphragm breakup above 10 kHz. The bi-amped BMS 4592NDs (bi-amped and dialed in) sound the best, and a close second is the FaitalPRO HF20ATs--mono-amped, of course)

If you want small loudspeakers, you can have them, but you're going to have the issues of small loudspeakers. Real high performance loudspeakers are much larger than miniature monkey coffins on a stick.

The problem with all line source radiators (like the RAALs), whether horn loaded or not) is that their vertical coverage basically collapses to whatever height the total ribbon height happens to be--and the longer the ribbon, the more this is true. This is a real problem once you listen to line sources in-room, in that if you stand up from a sitting position (if the line source is not floor-to-ceiling in length), they're no longer balanced to the lower frequency drivers/horns.

Point sources work a lot better--like the K-402.

Chris

 

[AnalogSteph]

@Chris A, you may want to contribute to this thread:
https://www.audiosciencereview.com/...narrow-directivity-and-more.15171/post-477932