Dr. Klaus Heinz of HEDD Audio (ex ADAM Audio) - measuring speakers, in particular speaker dynamics

[solderdude]

Talking about DSP... maybe someone is interested:

People are:
https://www.audiosciencereview.com/...unding-loudspeakers-currently-available.6995/
https://www.audiosciencereview.com/forum/index.php?threads/grimm-audio-ls1be-arrive-soon.7041/
https://www.audiosciencereview.com/forum/index.php?threads/grimm-audio-purité-audio.6970/

 

[andreasmaaan]

If @mitcho was using Reference 5 "big" speaker instead of his JBLs and Reference 1 small speaker instead of LS50 he would have a scenario where identical drivers would be used from upper bass to HF. Would the radiation pattern be different in that case or it would be pretty similar?

The horizontal radiation pattern would be very similar (although not identical) between the Reference 1 and the Reference 5, while the vertical pattern would be significantly different due to the much taller box and off-axis cancellation between the woofers of the Reference 5. The main differences would of course be in the operating band of the woofer(s), so under 350Hz.

 

[Krunok]

The main differences would of course be in the operating band of the woofer(s), so under 350Hz.

How so, as we assumed the FR is identical? Difference in max SPL?

 

[Soniclife]

How so, as we assumed the FR is identical? Difference in max SPL?

Frequency response is usually measured at 80db, so the louder peaks are likely to start showing compression a lot earlier for the single bass driver, distortion will be higher as well.

I've heard the 1, 3 & 5, I'd have 1 plus subs any day. Not that it's relevant to this conversion.

How much displacement do you need to do 100hz well?

 

[Krunok]

Frequency response is usually measured at 80db, so the louder peaks are likely to start showing compression a lot earlier for the single bass driver, distortion will be higher as well.

I've heard the 1, 3 & 5, I'd have 1 plus subs any day. Not that it's relevant to this conversion.

How much displacement do you need to do 100hz well?

Guys, I think we might have a misunderstanding here - I was talking about 2C + 8B vs 5.

I suggested using 2C instead of 1 to overcome shortage of SPL 1 might have in the 100-350Hz range.

 

[andreasmaaan]

How so, as we assumed the FR is identical? Difference in max SPL?

Guys, I think we might have a misunderstanding here - I was talking about 2C + 8B vs 5.

I suggested using 2C instead of 1 to overcome shortage of SPL 1 might have in the 100-350Hz range.

I was responding to your question in post #159 where you asked about differences in radiation pattern between the Reference 1 and the Reference 5.

You wrote (and I quoted):

If @mitcho was using Reference 5 "big" speaker instead of his JBLs and Reference 1 small speaker instead of LS50 he would have a scenario where identical drivers would be used from upper bass to HF. Would the radiation pattern be different in that case or it would be pretty similar?

I hope I understood your question correctly? My answer to that is in post #163.

I didn't attempt to answer anything to do with frequency response linearity or distortion, although @Soniclife's answer to that is spot-on

 

[Kvalsvoll]

Can you please elaborate on this? If @mitcho was using Reference 5 "big" speaker instead of his JBLs and Reference 1 small speaker instead of LS50 he would have a scenario where identical drivers would be used from upper bass to HF. Would the radiation pattern be different in that case or it would be pretty similar?

I admit there is a problem with mid bass when adding a sub to a small speaker like LS50. It would certainly be better if a speaker like one of these center speakers is used instead of a small "bookshelf" speaker.

View attachment 27451

When you look at it this way wouldn't you say that HEDD TM80, once you rotate it, actually looks a lot like a center speaker?

View attachment 27452

Comparing 1 with 4, yes, this will be like a small vs larger speaker, where many properties other than size are quite similar. The differences here are capacity in upper bass - lower mid, and radiation pattern. The 4 will have directivity control in the vertical direction. Arranging drivers symmetrically like this is very common for typical hifi-speakers, it controls vertical radiation, but of course does nothing to horizontal.

The @mitchco experiment was something else - here he compared two very different speakers. Some of the differences may be related to size, while others not so much. Such as directivity control and capacity at high frequencies - to achieve this does not require large size.

Comparing a larger speaker to a small with full-frequency-range radiation control is another interesting exersise. I have worked on this now recently, comparing the F105 - small with radiation control, to the larger speakers. It is interesting to realize what is possible and what can not be achieved due to physical constraints.

 

[andreasmaaan]

How much displacement do you need to do 100hz well?

It depends completely on driver attributes (particularly size of course) and desired SPL.

At 100Hz, a good 6" or 6.5" woofer with average efficiency and an Xmax of say 6mm or 8mm (presumably like that used in the KEF reference series) will manage about 100dB or slightly more @ 1m in 4pi space before hitting Xmax.

Such a woofer might produce in the order of 15-20% nonlinear distortion at Xmax.

In other words, for the sizes of woofers we're talking about here, 100dB or maybe 105dB (anechoic) is about as loud as the driver will play at 100Hz before sounding awful and potentially beginning to risk damage.

A speaker like the Reference 5 would be capable of approximately 12dB of additional output vs the Reference 1 at this frequency, since it has 4x the number of (presumably) identical woofers.

 

[Krunok]

A speaker like the Reference 5 would be capable of approximately 12dB of additional output vs the Reference 1 at this frequency, since it has 4x the number of (presumably) identical woofers.

Wouldn't it be better to leave 100Hz to be played by a sub and set XO to 160Hz? Sub like 8B can still handle 160Hz and Reference 1 would be more relaxed playing from 160Hz above than fighting with the 100Hz.

Btw, what exactly does this line mean in 8B specs: "LFE mode: 350Hz, 18dB/oct ". Does it mean it has a special mode in which it can play up to 350Hz?

 

[andreasmaaan]

Wouldn't it be better to leave 100Hz to be played by a sub and set XO to 160Hz? Sub like 8B can still handle 160Hz and Reference 1 would be more relaxed playing from 160Hz above than fighting with the 100Hz.

It would depend on your room, SPL requirements, and the location of the subs

Btw, what exactly does this line mean in 8B specs: "LFE mode: 350Hz, 18dB/oct ". Does it mean it has a special mode in which it can play up to 350Hz?

Yes but there are no filter variables in this mode, as it is intended to leave all filtering to the inbuilt DSP in an AVR preamp.

 

[Krunok]

It would depend on your room, SPL requirements, and the location of the subs

I don't really think speaker designers would choose XO point depending on my room and the location of the subs - there must be other criterias to choose optimal XO point between Reference 1 and 8B sub.

Yes but there are no filter variables in this mode, as it is intended to leave all filtering to the inbuilt DSP in an AVR preamp.

Ahaaa - LFE like Low Frequency Effect in 5.1 setup? Ok, but filtering would anyhow be handled by Audiolense filters so up to 350Hz is possible in the scenario we are discussing, right?

 

[andreasmaaan]

I don't really think speaker designers would choose XO point depending on my room and the location of the subs - there must be other criterias to choose optimal XO point between Reference 1 and 8B sub.

Speaker designers decide where the woofer goes in relation to the midrange. The user decides where the subs go in relation to the speakers. If there were a single best crossover point for all rooms and placements, KEF wouldn't include customisable filters on the subs

Ahaaa - LFE like Low Frequency Effect in 5.1 setup? Ok, but filtering would anyhow be handled by Audiolense filters so up to 350Hz is possible in the scenario we are discussing, right?

I would say yes... but cautiously.

 

[Krunok]

Speaker designers decide where the woofer goes in relation to the midrange. The user decides where the subs go in relation to the speakers. If there were a single best crossover point for all rooms and placements, KEF wouldn't include customisable filters on the subs

Sure, but let's assume sub will be somewhere near the standmount of the small speaker, like shown on @mitchco photo. Probably in that case XO point can be higher than 100Hz?

 

[svart-hvitt]

Comparing 1 with 4, yes, this will be like a small vs larger speaker, where many properties other than size are quite similar. The differences here are capacity in upper bass - lower mid, and radiation pattern. The 4 will have directivity control in the vertical direction. Arranging drivers symmetrically like this is very common for typical hifi-speakers, it controls vertical radiation, but of course does nothing to horizontal.

The @mitchco experiment was something else - here he compared two very different speakers. Some of the differences may be related to size, while others not so much. Such as directivity control and capacity at high frequencies - to achieve this does not require large size.

Comparing a larger speaker to a small with full-frequency-range radiation control is another interesting exersise. I have worked on this now recently, comparing the F105 - small with radiation control, to the larger speakers. It is interesting to realize what is possible and what can not be achieved due to physical constraints.

@Kvalsvoll , you wrote:

«It is interesting to realize what is possible and what can not be achieved due to physical constraints».

Could you elaborate on this?

As far as I understand, you’re as well about to launch a new speaker based on experiences with this one: https://www.kvalsvoll.com/Services/F2_en.htm

So it would be interesting to hear more about your experiences with «physical constraints».

 

[andreasmaaan]

Sure, but let's assume sub will be somewhere near the standmount of the small speaker, like shown on @mitchco photo. Probably in that case XO point can be higher than 100Hz?

Definitely

 

[Kvalsvoll]

@Kvalsvoll , you wrote:

«It is interesting to realize what is possible and what can not be achieved due to physical constraints».

Could you elaborate on this?

As far as I understand, you’re as well about to launch a new speaker based on experiences with this one: https://www.kvalsvoll.com/Services/F2_en.htm

So it would be interesting to hear more about your experiences with «physical constraints».

The new speaker is the F105 - the small one. The F2 (your link) is an old design. None of those are listed for sale at this moment. The new small F105 is not really based on anything from the F2.

The F105 is a concept design I have used to test out some new solutions for cabinet design and improved radiation pattern for small speakers. They are not expensive enough to generate any interest, but for their purpose they are nice - easy to move around, good enough for evaluation of the technical solutions.

What can not be achieved is exactly what the HEDD designer discuss in the movie - dynamics. The improved radiation at lower frequencies improves clarity and imaging, gives less coloring, but the impact and slam of the larger speakers simply is not there. And they can not play loud enough for what I call "full-scale" music reproduction. Some of this can be improved with better drivers, but it is not possible to generate the wavefront that a larger speaker creates. There is a difference even at moderate volume. Soundstage and presentation of the instruments are also different, but not necessarily better or worse than the larger speaker - this changes dramatically though, in a room without the acoustic treatment in Room2, the radiation pattern is quite wide and you will not get the deep reflection free gap I have here in Room2 in a room with reflective surfaces close to the speakers.

("Dynamics" here is a term I believe most of us understand the meaning of - it would be better to use the term "transient reproduction." The definition of dynamics is the difference in loudness between quiet and loud parts, and that is not what we mean here. Here "dynamics" means sense of power and realism and immediacy of attack on drums and all other sorts of percussive instruments.)

What I am doing in this exercise with the F105 (very small) and the F2 (slightly larger) is to find how to make a small speaker with the sound of a large speaker. The presenter in the HEDD video talks about how to make a speaker with the dynamics of a large speaker of the old studio monitor type combined with the resolution, smoothness and imaging of newer hifi-type designs. That is not the same. Because he (HEDD) - as I understand it - does not mind if the speaker is big.

I already have a speaker with both dynamics and resolution and imaging, one that is more like slightly larger in size. But this speaker does not sound like a big hifi-speaker, because the radiation pattern is very different. The HEDD speaker looks like the presentation would be more in the traditional hifi-direction. This does not mean he (HEDD) is wrong an I am right, it is a matter of choice.

I have several articles on the blog-page about this now, one about "Can a small speaker perform like a large", one where the F105 is presented with both measurements and sound impressions. I will not spam this post with links, those interested can easily find it on my web-page in the blog-section.

 

[pozz]

"Dynamics" here is a term I believe most of us understand the meaning of - it would be better to use the term "transient reproduction."

Excellent choice of words. I read something similar about hornspeakers, where the author wrote that their characteristic strength is providing a different sort of transparency than is usually talked about: transparent-to-source dynamics.

 

[pozz]

Ultimately what you hear is limited to what plays out on your eardrums, with the added factor of full-body tactile response to bass. Reducing speaker designs to that fact makes size far less important.

Heinz mentioned that he designed the towers to have an equal amount of driver area across the frequency spectrum. That's not something that can be said for 2-way or 3-way monitors and that aspect would be one of the main differences between any big/small speaker, regardless of type. It would be really interesting if driver area/frequency can be correlated to other measurements.

 

[Biblob]

Could it be that because they are a closed design, which is seriously under represented these days, that provides the biggest advantage in terms of transient response?
And gives the advantage over most bass-reflex speakers in terms of "clarity" and "details".

 

[andreasmaaan]

Could it be that because they are a closed design, which is seriously under represented these days, that provides the biggest advantage in terms of transient response?
And gives the advantage over most bass-reflex speakers in terms of "clarity" and "details".

That’s certainly one of the claims made by closed-box advocates. There’s no doubt that closed boxes (assuming no signal processing) are capable of superior transient performance. There are two possible means by which this is the case.

Firstly, a closed box will have approximately half the phase shift of a ported box (180 deg vs 360 deg), translating into half the group delay for a given F3. This is a low-frequency only phenomenon.

Secondly, a closed box can be stuffed more densely, more effectively absorbing the woofer’s back wave and potentially thus improving its transient behaviour by reducing interference on the cone’s motion from internally reflected waves. (Well, you can stuff a ported box very densely if you like, but the port will stop functioning beyond a certain point.) This is primarily a mid-frequency phenomenon.

As to the first point, I’m not aware of any published scientific evidence demonstrating that a phase shift in the range of 360 deg (as is caused by a vented box) is audible at any frequency, let alone this low down; that’s not to say there is nothing to the claim, but rather that it is yet to be scientifically demonstrated.

Similarly, I’m not aware of any specific research into the audibility claim regarding back-wave interference, although it seems more plausible to me personally that this should be an audible concern - albeit possibly not due to time-domain effects specifically.

Also keep in mind that, with digital signal processing, the transient response of both sealed and vented boxes can be corrected, at the cost of (pre- and post-) ringing.

The main disadvantages of closed boxes - as alluded to by Mr Heinz - are related to excursion, with closed boxes tending to result in higher distortion, less extension, and reduced max. output compared to their vented counterparts (with many complicating variables at play ofc). These issues have nothing to do with transient response per se.