Chat with legendary loudspeaker engineer Laurie Fincham (THX, Harman, KEF)

[ErinH]

Here is my chat with an absolute legend in the audio community, Laurie Fincham. I am sharing here because I think it is important to learn from a master in their field who have decades of experience to teach from. The topics covered here I truly believe are helpful for us all to learn a bit more and gain some insight in to how a loudspeaker engineer views them. The number of things Laurie has invented, designed and/or headed in his years as an engineer at Celstion, Kef, Harman and THX are staggering and having the privilege to be able to talk to him so openly and even call him a friend is just incredible. Such a humble man, too. I hope you all enjoy this as much as I did.

Laurie doesn't participate on forums so he won't see this post, so please take the time to leave a comment on the video for Mr. Fincham thanking him for taking time to answer your questions.

Note: as with all my "interview" type videos, this video is not monetized by me so if ads run then that is purely on YouTube's doing.


I just want to again thank Laurie for joining me. If you any questions for a future video feel free to post it in the comments section.

Timestamps:
0:00 - Introduction
05:57 - Ports and Passive Radiators
12:06 - History in Car Audio
27:20 - Distortion
45:53 - Impedance
51:11 - Low vs High Sensitivity Speakers
59:47 - End

 

[shadyJ]

Scoring that interview is quite a coup! Great conversation and nice work!

 

[ErinH]

Thanks, James!

 

[Hetfield]

The part on sensitivity was personality very interesting as I'm rustling with this question right now.
Here are my thoughts on sensitivity when it comes to speakers but having no college degree to back this up. Feel free to call me an idiot.
High sensitivity speakers, like 95 or more to my thinking is much more than just playing extremely loud. To be the biggest benefit is at low volumes, or lower volumes the speaker will still sparkle and shine and retain is dynamics. So if I normally listen at -20 during the day if at night I'd like to turn it down to -25/-30 you will not lose the dynamics and will still sound fantastic just not as loud.
Am I way off on that? What would you consider high sensitivity? Anything over 90? You start at 95? Is 88 ok for retaining the dynamics at lower volumes?

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[ryanosaur]

What would you consider high sensitivity? Anything over 90? You start at 95? Is 88 ok for retaining the dynamics at lower volumes?

85-88 seems to be regarded as average, pretty commonly. 90 and above is usually considered high, while I think anything truly measuring over 95 is bordering on pro level or unicorn territory (and while it's not impossible, it's just not very common.
Dynamics, as I understand, falls more under the purview of design: how the individual drivers are chosen and integrated into the Speaker as a whole. This entails balancing the individual driver sensitivity, power handling, etc; up to and including the XO.
The thing about some very high sensitivity Drivers, especially in the Pro market, is that they have a tendency to have some noise at lower SPL. This isn't a problem in a large venue where the audience is not standing next to a speaker and where SPLs are much higher. It's been noted many times that many Pro drivers aren't really suitable for the home for that reason alone. (Though this is not entirely the case.)
Another consideration is the balance between the design goals: extension, sensitivity, etc. Pro drivers, for example, need to play LOUD, and handle gobs of power. The cost here is usually in the realm of poor extension and sometimes audible noise. A quick review of Pro Woofers and Subwoofer Drivers will show that while they are designed to easily handle, say, up to 2000w, and even have some crazy amount of Xmax.Xmech, they also have very high Fs (resonant frequency in free air). While making such a driver perform below Fs is possible, it requires more power and other methods to coax that performance out of the driver. The fad of Pro Sub drivers being used in home Subs is still quite strong, as evidenced by the Marty Subs and Devastators.
Regardless, there are no end to the designs people and companies are coming up with. I think JBL is a great example of using Pro designs in HT/Home Audio product. If you deep dive into their designs and Driver evolution, you can see how their old school Sound Reinforcement products have improved and how they utilize them through their entire lineup of Speakers.

Mind, I'm still not an experienced designer, and I may have some misunderstandings in my knowledge base. As always, corrections are welcome!

 

[Hetfield]

85-88 seems to be regarded as average, pretty commonly. 90 and above is usually considered high, while I think anything truly measuring over 95 is bordering on pro level or unicorn territory (and while it's not impossible, it's just not very common.
Dynamics, as I understand, falls more under the purview of design: how the individual drivers are chosen and integrated into the Speaker as a whole. This entails balancing the individual driver sensitivity, power handling, etc; up to and including the XO.
The thing about some very high sensitivity Drivers, especially in the Pro market, is that they have a tendency to have some noise at lower SPL. This isn't a problem in a large venue where the audience is not standing next to a speaker and where SPLs are much higher. It's been noted many times that many Pro drivers aren't really suitable for the home for that reason alone. (Though this is not entirely the case.)
Another consideration is the balance between the design goals: extension, sensitivity, etc. Pro drivers, for example, need to play LOUD, and handle gobs of power. The cost here is usually in the realm of poor extension and sometimes audible noise. A quick review of Pro Woofers and Subwoofer Drivers will show that while they are designed to easily handle, say, up to 2000w, and even have some crazy amount of Xmax.Xmech, they also have very high Fs (resonant frequency in free air). While making such a driver perform below Fs is possible, it requires more power and other methods to coax that performance out of the driver. The fad of Pro Sub drivers being used in home Subs is still quite strong, as evidenced by the Marty Subs and Devastators.
Regardless, there are no end to the designs people and companies are coming up with. I think JBL is a great example of using Pro designs in HT/Home Audio product. If you deep dive into their designs and Driver evolution, you can see how their old school Sound Reinforcement products have improved and how they utilize them through their entire lineup of Speakers.

Mind, I'm still not an experienced designer, and I may have some misunderstandings in my knowledge base. As always, corrections are welcome!

Excellent info, thank you. I'm still trying to find the right balance and understand what all this means. Super high sensitivity or average at 87 that like the SVS Ultra bookshelf speakers are. I was told their specs are honest and truthful. That's the other thing, who has honest specs and who doesn't.
Look at the new Def Tech demand series speakers. I'm quite surprised how low the sensitivity is, 84 I think.

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[ryanosaur]

Excellent info, thank you. I'm still trying to find the right balance and understand what all this means. Super high sensitivity or average at 87 that like the SVS Ultra bookshelf speakers are. I was told their specs are honest and truthful. That's the other thing, who has honest specs and who doesn't.
Look at the new Def Tech demand series speakers. I'm quite surprised how low the sensitivity is, 84 I think.

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That's why so many of us here value what Shady and Erin do for the community. Hell, even Amir over at ASR if you can get past some of his antics.
Klipsh is known for fibbing about their Speaker Sensitivity, just like DefTech was known for fibbing about their extension. Good third party reviews mean a lot!

I don't remember what the DT Demand series looks like from a Power Handling perspective, but if they are designed to take gobs of power, the only flaw is that you need expensive amps to deliver that power so the lower sensitivity design can hit the SPL you want.
At 84dB, it would require about 250w in a medium room (boundary reinforcement is a must) to get you to reference level dynamic peaks at 2 meters/~6'. If you are in a larger room where you don't have the boundary reinforcement, and you may well be sitting further away... you may find yourself needing 500-1000w to hit those peaks: something I expect would likely fry those new DTs.
Conversely, a Speaker with 95dB Sensitivity is outperforming the 84dB Speaker quite significantly: 128w to the former should yield 116dB @ 1m, vs 105dB for the latter... To equal that 116dB, you would need to again have a Speaker rated at 84dB capable of taking ~1000w!

In the end, a lot of this then comes down to being an educated consumer and taking the time to shop for what is right for you and your listening habits. Having a budget is one thing, but when you start weighing the pro/cons, across the board, it becomes readily evident that the greater the budget allowed gives one the freedom to navigate beyond the drawbacks. There will always be some point of diminishing returns, but finding the balance point that is right for you is what is important. And its not going to be the same as the balance point for Jim-Bob up the street or Jerry in LA. Sometimes, it's the difference of Brand A to Brand B, and maybe an extra $100-200; other times it might be the difference between the entry level and the mid-level offering of one company (Monitor Audio Bronze to Silver, for example, and $1000-1500).

 

[TLS Guy]

That was a really great interview.

My greatest take, that I agree totally with, is that passive speakers have had their day. The benefits of active speakers and intelligent use of DSP has the power to be totally transformative.

I have been saying for ages, that amps belong in speakers and NOT receiver boxes. Someone has to lead the market here.

He is also right about sensitivity and amp headroom for classical music. The peaks are huge, and so sensitivities in the 89 to 91 db 2.84 V 1 meter are really required, otherwise very few affordable and practical amplification systems will have the head room. That is what it takes to really produce that "like being there" effect, among other virtues. But without that reserve you don't stand a chance.

Lasly, I would say that coincident designs have enormous benefits in center speakers.

Center speakers are definitely hurt by not being coincident or good full rangers. So I have now done coincident, full range and three way center, speech clarity and performance at power are in that order. I'm sorry, but the majority of center speakers are just not fit for purpose.

He alluded to poor bass performance, but that is a bigger issue than just ports and ABRs.