Sealed mini speaker, 3-way

[Mart68]

Question is, were they successful?

I can't really answer that. Anecdotally, I showed them at a meet and was quite surprised that they were very well received.

That's why I asked which measurements should be made and for what purpose. What should they say in terms of preference by a single person in their environment that nobody here knows?

Preference prediction at best can only be on general trends, I completely agree. It's better than nothing though.

I have seen a lot of pedantry here.

It's a hi-fi forum!

 

[thewas]

Have to disagree, these are quite clearly waveguides:

Interestingly on those B&O shown the mid drivers acts more as a "phase link" between the tweeter and the woofer:

B&O Tech: Uni-Phase Loudspeakers

#45 in a series of articles about the technology behind Bang & Olufsen loudspeakers Warning: In this page, I use a bunch of equations that might look very unfamiliar. T…

www.tonmeister.ca

 

[Mart68]

Interestingly on those B&O shown the mid drivers acts more as a "phase link" between the tweeter and the woofer:

B&O Tech: Uni-Phase Loudspeakers

#45 in a series of articles about the technology behind Bang & Olufsen loudspeakers Warning: In this page, I use a bunch of equations that might look very unfamiliar. T…

www.tonmeister.ca

Thank you, that's very interesting.

 

[DSJR]

I don't know about that Dave - I think it unlikely since being very much engineering-led companies in the 1970s and 1980s that KEF and B&W were unaware of the importance of even dispersion. Certainly B&O were since their speakers from 1983 use waveguides on both the tweeter and the midrange dome.

And almost all of them were awful Mart, the upper mid dome a kind of 'fill-in' phasey thing with deep suckouts either side of it done intentionally. The few measurement reviews of the time showing what I mean. The 1970s Beovox models were rather better I recall, the 2702, three way 3702 and (heavily) Goodmans based three way 3800 could still be well liked today I reckon if restored well and the 5702 was a kind-of squat Ditton 66 and really good i remember. The two top Beovoxes were good I remember (yours being one of them), but they were imposing and we didn't stock them (the godawful S80 and S80II were as far up as we went back then.

If you look up the BBC papers (not as high-brow as you'd think), dispersion does come into it (was it the LS5/5 paper or the 5/8 one, sorry, I need to look it up) and certainly they knew about it and did their best to aid it (slot in front of the large bass driver was one attempt to help). I agree that it's all way out of date now, but the aforementioned 801 and R105 really did move things forwards at the time.

 

[Heinrich]

Thank you, that's very interesting.

It looks quite good to the layman's eye. Another, more common term for it was "filler driver".

... upper mid dome a kind of 'fill-in' phasey thing with deep suckouts either side of it done intentionally ...

Exactly, the vertical is deeply affected by the basically first order part on the mids. And, not the least, the capabilities of the midrange were in parts wasted, while the tweeter may have seen overload quickly.

It's a hi-fi forum!

I see that, and my note wasn't meant as a rant. The tight focus on the spinorama can be critisized, though. Constructively speaking, there should be ways to evaluate a speaker without the 'spin'. It doesn't make too much sense to generate a spinorama for a real bookshelf speaker to be placed on a bookshelf into a wall of books ;-)

The spinorama is meant to show the on-axis response, and also to predict the in-room response. On-axis the little ones are o/k due to DSP and, measured in the dedicated room, they perform quite allright also; in actuality. What more could the 'spin' reveal?

Bass is meant to be a crucial factor for listener satisfaction. The aim to reach down to 30Hz, with enough spl to be actually perceivable, is something. Alas, it cannot be realized with bass reflex aka 'ported' in size restricted speakers (wind noise, too heavy drone/baffle size).

So, in the end I'm only wondering.

 

[Heinrich]

So, in the end I'm only wondering.

As time goes by, it came to me how to show the benefit of a three-way. Intermodulation at about 76dB@1m:

The green gras shows the intermodulation / distortion products, if the 17cm bass/midrange driver is driven alone, simulating a two-way design. The frequency response was equalized roughly to flat, bass boost included.

The red shows the results for the three-way speaker using the same bass/midrange driver and same bass boost and same box and position, now complemented by a 10cm midrange from 300Hz on.

Not to speak of a smoother directivity due to cone size, and a shorter center/center distance between mids/tweeter.

Bass driver: https://quint-store.com/media/files_public/54e892698ed662f7c44f370f449e5f4e/sds-160f25pr01-08.pdf
Midrange driver: https://hificompass.com/en/speakers/measurements/peerless/peerless-tc9fd18-08

 

[thewas]

Bass driver: https://quint-store.com/media/files_public/54e892698ed662f7c44f370f449e5f4e/sds-160f25pr01-08.pdf
Midrange driver: https://hificompass.com/en/speakers/measurements/peerless/peerless-tc9fd18-08

I really like your bass and mid choices, great performance and value for money, am not sure though about your tweeter as it has a too deep for its width waveguide, is it from Wavecor? Similar ones I have seen being measured by the two German DIY magazines didn't have a nicely continuous directivity due to that.

 

[Heinrich]

I really like your bass and mid choices, great performance and value for money, am not sure though about your tweeter as it has a too deep for its width waveguide, is it from Wavecor? Similar ones I have seen being measured by the two German DIY magazines didn't have a nicely continuous directivity due to that.

Can'tell for the moment. But the tweeter is an el cheapo likewise. Used down to 2kHz, while allowing for 0,5%HD2. No issues with directivity - as already said, the in-room response is as smooth as one can expect in real life.

 

[Heinrich]

Last updates:

The tweeter is an Omnes Audio T25H; no more available.

The measurement on intermodulation is redone for clearity. First, the frequency response of the woofer alone was matched to that of the finished 3-way arrangement up to roughly 3 Khz. In doing so it shows how the woofer would perform, if it was used in a 2-way arrangement, typically with 2,5kHz x/over. The match in frequency response:

The mismatch around 30Hz originates in environmental noises. The other discrepancies are due to different directivity in the nearfield. In the farfield both should be pretty flat. (Btw, in-room f/r is flat (!) down to 30Hz, and as you see from the slope towards subbass in the nearfield , room gain grants another 6dB; didn't need full e/q there.)

The difference in intermodulation at about 76dB@1m, woofer alone (2-way) in green, 3-way in red:

I think the difference of up to 20dB speaks for itself. And the skirts around the lines are pretty much narrower. I suspect the microphone contributes to IM as well, but didn't bother to double check. Additionally the raise below 300Hz or so may be due to inevitable environmental noises.

 

[Heinrich]

Last updates:

Very last update, for the archive;

- bass response is crucial, especially with notoriously weak small speakers
- a bass reflex design is not feasable, hence sealed with e/q
- directs towards real three-way as to keep intermodulation halfway in check
- DSP controlled x/over as low as possible
- small baffle, hence no directivity control possible, wide radiation is set
- allows to steer the vertical radiation pattern upwards in the x/over region mid/tweeter

+ e/d'ed to 20Hz f3 in-room (taking advantage of about 10dB of room gain, when seated on a shelf)
+ spl around 86dB stereo, 10% harmonic distortion at 33Hz single tone in 3m distance
+ at 86dB virtually no HD above 100Hz, IM likewise
+ full spectrum max spl might be 96dB; regular listening volume about 66dB, good dynamics alltogether
+ first null in the vertical (lobing) located at +80° up, -40° down respectively

o listening at 66dB or rarely at 76dB median, 20dB dynamics gives fully satifying results
o bass is as full and deep as one can wish for, no distortion is heard, no boominess, colorful, differentiated
o no need to be cranked up in search for more
o midrange is never affected by bass tones, remains clear and soft or forward, depending on program
o room integration / stereo effect is as great as w/ a coax, but wide

x the internal cavity to be sealed tight; otherwise leakage would generate quite elevated distortion, needs glue
x output is limited, subjectively running into a wall when overdriven, mostly compression in bass (amplifier?!)
x complicated design w/ DSP plus passive x/over mid/tweeter, 4 channel amp
x lots of off-axis intereferences due to baffle design, not as much mitigated by the shelf and books as hoped for; remaining +/-2dB
x too cheap to be taken serious
x no spinorama

=> if done by the industry it could be a nice little package, internal amp, programable DSP, ..., not for too many DIYers

Size: 30cm wide x 21 x 21 cm^2, internal volume 8l sealed (bass) + 0.5l (midrange), 9mm poplar plywood, braced extensively
Bass driver (35Euros): https://quint-store.com/media/files_public/54e892698ed662f7c44f370f449e5f4e/sds-160f25pr01-08.pdf
Midrange driver (15Euros): https://hificompass.com/en/speakers/measurements/peerless/peerless-tc9fd18-08
Tweeter (14Euros): https://www.lautsprecher-shop.de/pdf/omnesaudio/OAudio_t25h_Datasheet.pdf
x/over: 300Hz @ 24dB/oct (DSP), 2000Hz @ 12dB passive components (15Euros)
power req.: 50W peak bass and mid/tweeter each

 

[Arindal]

Bass driver (35Euros): https://quint-store.com/media/files_public/54e892698ed662f7c44f370f449e5f4e/sds-160f25pr01-08.pdf

- a bass reflex design is not feasable, hence sealed with e/q
...

+ e/d'ed to 20Hz f3 in-room (taking advantage of about 10dB of room gain, when seated on a shelf)

Are we talking about the same Tymphany SDS 160F25PR01 driver?

Not sure if it is a good idea to incarcerate this one in an 8l enclosure Chebichev-style and EQ it down to a 20Hz f3. This would require something like a boost of up to 20+ dB in the lower bass, which is a thing I would not do with a woofer of limited power handling and xmax alike. Given the parameters and standard methods, this one looks rather like a candidate for a huge ported cabinet.

The list of 6.5" suitable for a very compact sealed enclosure ready for active compensation to 20Hz is rather brief. Peerless SLS P830946 or Reckhorn D-165 maybe.

 

[Salt]

Are we talking about the same Tymphany SDS 160F25PR01 driver?

Not sure if it is a good idea to incarcerate this one in a 8l enclosure Chebichev-style and EQ it down to a 20Hz f3. This would require something like a boost of up to 20+ dB in the lower bass, which is a thing I would not do with a woofer of limited power handling and xmax alike. Given the parameters and standard methods, this one looks rather like a candidate for a huge ported cabinet.

The list of 6.5" suitable for a very compact sealed enclosure ready for active compensation to 20Hz is rather brief. Peerless SLS P830946 or Reckhorn D-165 maybe.

 

[a4eaudio]

I was going to post "measurements or it never happened".

But I started to simulate it...sealed, with EQ boost, assume 12dB room gain...and I'm skeptical. So how about, at a minimum, "simulate it or it never happened".
I.e., can you even show us a simulation of that driver, in a sealed box, with EQ, and room gain, that produces anywhere near 83dB at 20Hz?

 

[Heinrich]

Are we talking about the same Tymphany SDS 160F25PR01 driver?
... Peerless SLS P830946 or Reckhorn D-165 maybe.

Sure, but I don't see any advantage in using a different model. Have I overlooked something?

I was going to post "measurements or it never happened".

Well, measurements can also be fabricated. However, I have explained the essential point above (post #49); it is the intermodulations that quickly become critical with a cheap driver. Even expensive ones will be pushed to their limits with Doppler distortions, for example. To really exploit the maximum excursion requires a midrange driver. Basically, proving this was the aim of the design. It exists, see post #1.

But I started to simulate it...sealed, with EQ boost, assume 12dB room gain...and I'm skeptical.

The goal was not to make a "better" loudspeaker in competition with the industry, but to subjectively prove the idea.

It's a safe bet that the sound radiation plays a major role; the baffle doesn't allow for a directional effect. The dispersion is definitely very wide.

With DSP, the box can be trimmed to any frequency response. Unfortunately, the edges of the cabinet are still distracting even when the bookshelf is packed. Interference causes irregularities of up to +/-2dB in any direction. The future user will have to accept this. The interaction with the bookshelf renders individual measurements arbitrary. Hence they are not available for publishing.

To the point of criticism: I have 24bit digitization depth available for equalization, which is also sufficient for huge corrections. One bit corresponds to 6dB. Above, the box was still tuned to 30Hz. However, I wanted to see (hear) whether the reproduction of asymmetrical, impulsive noises (the plucking of a bass guitar) could play a role in the sound impression. I think so, which is why it's now staying at 20Hz, even if the available level is ridiculously low. Somehow it still energizes the room.

The achievable level has also already been discussed. 66dB is significantly louder than a clear and distinct conversation. Playing twice as loud (76dB) is already perceived as very loud here. Then there is an unsuspected 20dB dynamic range, making 96dB. And that's what this speaker is capable of if the content is not limited to the lowest bass range. EDM will of course be a little difficult, but that's not the thing here.

 

[Arindal]

Have I overlooked something?

Vas=29.56l, Qts=0.49, fs=41.76

Standard calculation for Butterworth would come to a sealed 28l enclosure as an ideal. Your 8l in contrary would result in a resonance frequency of approx. 92Hz and a quality factor close to 1.1, which means almost Chebichev plus a certain degree of uncertainty if the mechanical part of the driver can cope with such a compact hence stiff air volume at frequencies below the aforementioned resonance.

xmax=6.1mm, Pmax=60W

As the response amplitude is quickly dropping below 90Hz, you need significant electronic boost for everything below 70Hz. The deeper, the more resources it will eat up. With just 141 sqcm of SD, limited linear excursion and power handling, that might mean a problem.

As mentioned, there are some 6.5" drivers meant for such an application, but not many. Interestingly, pro developers like Bruno Putzeys (Kii Audio) seemingly prioritize xmax, power handling and Vas for such an application over other factors. The Peerless SBS 160F35AL01 (which seems to be OEM-only) would not have been my first choice due to higher Qts and fs alike.

With DSP, the box can be trimmed to any frequency response.

Frequency response does not equal satisfactory music reproduction at higher SPL, particularly in the lower bass bands with a driver in less than a third the enclosure volume it is meant for.

The achievable level has also already been discussed. 66dB is significantly louder than a clear and distinct conversation. Playing twice as loud (76dB) is already perceived as very loud here.

I don't know if your distinct conversations are that rich in energy below 70Hz, but any electronic music, densely-mixed rock or percussion-rich classical pieces would sound pretty poor with lower bass limited to 66 or 76dB.

 

[Heinrich]

Standard calculation ...

Of course this is meant to be non-standard.

... Interestingly, pro developers like Bruno Putzeys (Kii Audio) seemingly prioritize xmax, power handling and Vas for such an application over other factors. ...

So, it seems it works?

As said, an experiment in order to explore remote possibilities. The addressee is a woman with less interest in hifi. She will not ever, as we might do, crank it up just to feel the limits. She will experience high quality virtually unlimited bass from a tiny speaker, while playing at household sound pressure levels.

My personal interest was: is Doppler and other intermodulation relevant? So I built a testbed, to evaluate the case subjectively, because nobody else seems to care. Yes, better avoid Doppler and other IM. It can be done. More bass with a three-way.

 

[Arindal]

Of course this is meant to be non-standard.

Even non-standard has to give way to physics.

So, it seems it works?

If ´it´ = 8pcs of Peerless SBS 160F35AL01 per stereo pair plus 2300 Watts RMS of amplification, it seemingly works. Not my favorite in terms of lower bass, but it works.

Would assume that 2pcs of Tymphany SDS 160F25PR01 with half the xmax and 1/4 the DS, plus 100 Watts - rather not.

My personal interest was: is Doppler and other intermodulation relevant?

Legitimate and very interesting question which remains unanswered with your setup. I mean, what is the point in doing such experiments by driving an incapable woofer with limited xmax in 1/3 of the necessary volume, and not a fraction of the power needed to simulate a situation in which a common 6.5" would show audible Doppler and IM?

With compact designs prone to driver the bass into distortion, I would subjectively always tend to prefer a 3-way design in which the midrange would retain its clarity.

 

[M240i]

@Heinrich Send your speaker to Amir for NFS testing and see what that reveals.

 

[Heinrich]

Even non-standard has to give way to physics.

I own physics ;-)

If ´it´ = 8pcs of Peerless SBS 160F35AL01 per stereo pair plus 2300 Watts RMS of amplification, it seemingly works. ...

Don't forget for what it is made for ;-) Regular people ... .

I mean, what is the point in doing such experiments by driving an incapable woofer ...

O/k, got me. What I didn't talk about is the precursors
- extra long excursion, fine woofer/mid x/over @ 1.2kHz to a dome tweeter, a fail because of IM originating in the surround (measurements lost, so don't exist)
- this woofer w/ the midrange used up to the treble, too narrow, matt, uninspiring (measurements lost, so don't exist)
- this woofer w/ the tweeter alone x/over at 2kHz, lame, barfing (measurements lost, so don't exist)

From this I made up my working hypothesis. A three-way will solve the problems posed by the small enclosure, which was set as part of the sports. A just for fun thing right from the start. Otherwise I'm quite happy with massive speakers in 100liter class (pro drivers).
"A three-way will *not* show problems with extended bass in a small enclosure."
For now I couldn't falsify the hypothesis. As you point out, implicitely, I really tried hard.

With compact designs prone to driver the bass into distortion, I would subjectively always tend to prefer a 3-way design in which the midrange would retain its clarity.

Exactly.

@Heinrich Send your speaker to Amir for NFS testing and see what that reveals.

It would be easy because of the very lightweight poplar encasing. As I exemplified several times already, the difraction artifacts, the intererences laugh at the spinorama on and off. It made my yaw drop, that I don't bother at all. Seems that with a constantly very wide radiation and basically small enough wiggles there are no disadvantages.

You may take my word on the former part: as bad as it gets. We spare the postage fees and a lot of work better spent for something useful.

 

[M240i]

It would be easy because of the very lightweight poplar encasing. As I exemplified several times already, the difraction artifacts, the intererences laugh at the spinorama on and off. It made my yaw drop, that I don't bother at all. Seems that with a constantly very wide radiation and basically small enough wiggles there are no disadvantages.

You may take my word on the former part: as bad as it gets. We spare the postage fees and a lot of work better spent for something useful.

There's always somebody who thinks they can come up with a better mousetrap.
Without a proper understanding of the limitations involved, your April Fool's speaker is just that.