Tech Talk 18: Acoustic Center

[@99thDimension]

A good book on this subject is Sound System Engineering by Don Davis, Eugene Patronis & Pat Brown. Stewart Tyler of ProAc perfected the phase response of his systems as well. Customers of his early designs always wonder why the ProAc logo on the woofers were at different angles. Mr Tyler would do the finial phase tuning by ear which required shifting the axis of the woofer itself. ProAc speaker systems purr like a lion from the smallest models to his flagship designs.

[@ericschulze5641]

One of your best.very informative & you actually said how to fix it

[@TheDecguy]

When I listen to these discussions about design and at the same time I think back to the typical speakers that were used in studios to mix back in the 70s, 80s, 90s, etc. Speakers like the Yamaha NS 10 M, the JBL 4311b, and etc. I wonder how I can listen critically (when I put my audiophile hat on) to music that we mixed on these “ancient” speakers? And yes I still have my NS 10s and my 4311s which I still listen to. It would be crazy fun to check out the time alignment on the 4311s. Thanks for your presentation on speaker design.

[@AdryDoic]

ribbon tweeter is helping a lot to get that 3d stage ! it's way more difficult to get it with dome tweeter .. its much about how low the Ribbon can get in my eyes.

[@bleusound23]

Hi danny!! When you talk about "trick you can do in crossover to adresse the offset of acoustic center" did you make reference to make asymetric acoustic slope?? I had appreciate if you can elaborate little on this!! Thank you!! great video ;)

[@Rob1972Gem]

The KEF Q3 floor standing speakers sound great they have the tweeter in the centre of the main speaker works well on my system sound stage is done well and the base response is very good

[@porkchopspapi5757]

Good stuff thanks. Wouldn't the horn ameliorate the off axis problem due to making the sound wave front larger?

[@nathandaniels4823]

Danny, you mentioned that ideally, the best driver alignment would be concentric (at least conceptually). But I haven’t seen any GR-Research concentric speakers, so I’m guessing there’s a real world complication with the idea. I’d love it if you talked about that at some point.

[@mikafoxx2717]

The only speaker I know that does this is the QUAD ESL-63 and it's contemporaries. Although it's a electrostatic speaker, it uses concentric rings of stators and uses resistors to create a low-pass filter with the self capacitance of the panel as it furthers from the center of the panel. It imitates an infinitely small point source of sound.

[@j.t.cooper2963]

The answer is simple, It's too expensive to make it profitable.

[@paulb4661]

Hi Danny, It would be good to mention the effects of acoustic loading by the midwoofer cone, often under excursion, on the tweeter radiation pattern by the same token. This issue becoming especially evident in co-axial designs, where special consideration is necessary to evaluate cone profile, which by then effectively acts as horn loading. It is of less importance than getting the radiation centres close, but in a sense proves that there's no free lunch in acoustics - every solution leads to benign or severe issues elsewhere.

[@totobeni]

you shuld grow your mullet back. it was awsome!

[@cwtim]

Very nice video!! I so agree with this, sometimes I see monitor speaker placed on the side and it really annoys me. I see it that when placing the drivers horizontal you get more horizontal com-filter effect (same frequency time differences) and your ears are more sensitive for horizontal combs because the ear is placed horizontal apart from each other. Vertical combs need to be noticed by the ear of ears inner reflections. example, Stereo setup speakers with two drivers setup horizontal play 4x (spots) the crossover point 1kHz in horizontal axes, when placing them upright they only play 2x the crossover point 1kHz in horizontal axes.

[@paulgyro]

Do you believe the THX focus on even horizontal distribution and limiting vertical is a bad design goal?

[@MickeyMishra]

Yes Yes Yes.. Talk about your Corvette and Drag racing :-) I bet you got the BEST exhaust note at the track Dan! For April Fools? You should do one of those Videos where you get a Pair of Corvettes, and compare that to Intakes. THAT would be COOL!

[@brianshivers4735]

I'm thinking about building some 2-way towers for my home theater. I like the look of TMM designs, but this is making me think an MTM would function better, with the tweeter at the midpoint between the two woofers (wired in parallel or series). My understanding is that the acoustic center of the two woofers would be at the midpoint, which is where the tweeter is. Is this correct? Thanks!

[@mdocod]

TMM should be implemented with 2.5 way crossover. Lower midbass rolled off at the inverse of baffle step loss. This design approach gives basically the same "coherence" as a 2-way with single midbass, but with full BSC accomplished without having to "tilt/lower" the response of the whole speaker. MTM will typically have both midbass drivers playing up to the crossover, with the BSC compensation applied to the full signal of both midbass drivers. This results in some more pronounced cancellation in the vertical off-axis in the upper mid-range. Each design has advantages for particular applications. If you have a good damped listening environment, TMM is generally superior. In troublesome listening environments with hard floors and ceilings, MTM is generally superior.

[@kenthomas1613]

@Danny Richie. What NEO3 option would you consider the best for a sealed enclosure design? NEO3 with open back, shallow back cup, deep back cup?

[@nara4420]

when i've seen the teaser-image i thought that you want to talk about the baffle-step and chassis-positioning, but this was also an interresting topic.

[@dannyrichie9743]

I covered baffle step loss in another video.

[@SuperMoeLarryCurly]

How would you recommend to treat the ceiling, keeping the WAF in mind? ☺️

[@dannyrichie9743]

Absorption panels. See this one: kzbin.info/www/bejne/nKHMfX-nesyLbdk

[@seraphin_creates]

hi Danny, what is the maximum allowable distance between two drivers in relation to their crossover point. for example at 1k Hz the wavelength is 13.5 inches but the maximum distance surely isn't 13.5 inches? thanks

[@-IE_it_yourself]

i have the same question. a realistic xover point would be 2000hz being 6.75". would mounting the tweeter to closer or further have the same out of phase problem? could i put the tweeter then a 2x(6.75") to be in phase again?

[@alexw890]

Of the crossover point is 1k hz then 13.5 inches would in fact be the maximum distance.

[@davidmay3950]

Hehehe he said "short pants". So a coaxial speaker is ideal in design?

[@Tracks777]

nice video

[@scarmenl]

Is that not what Legacy Audio is doing?

[@mrctonyb]

Good stuff to take in consideration! 👍🏼

[@-IE_it_yourself]

ok, what what techniques are used to achieve this in a practical sense. you are very good at identifying the problem, but when it comes to an answer, and this is trend in your videos, the solution is "you need to design a speaker to avoid that". okay but how? i get a want the drivers in phase but how? is this dont with baffle position of the drivers, with the xover, what variables need to change? the higher the xover frequency the closer the drivers need to be. ok but what is the relationship here? another trend i notice your counter example are very extreme where as within ball park the what is the difference. im not listening to a speaker with a woofer in another room or with my ear on the floor, but im im in a general listening area say on a couch sometimes sitting up or laying down. where on the bell curve will we notice something. the topics you cover are very interesting, but after watching i dont feel like i came out with any practical tools to approach the problem.

[@tutnallman]

Is this why Tannoys sound so good even if they measure a bit up and down?

[@ekimandersom4478]

Yes, same with KEF

[@robertdavis5714]

What happened to the Hair. Early 70's when let's space the tweeter as far as possible from the woofer, that will look smart.

[@chuckmaddison2924]

Great video. I have seen some speakers on a Chinese site, buy 100 put your name on it. They had more drivers than a stationary freeway at peak hour. Pure crap.

[@ericschulze5641]

If it's the same sight I saw they had some good stuff & I suspect many of the speakers we see available are made at this plant also I think you're off by a few hundred units I don't think you can get your logo on it unless you order 500 or more

[@antoniojoseandreomartinez9710]

🙋👍❤️

[@zogzog1063]

Sir, may I make a gentle criticism. It is simply this: your videos are too long. Allow me develop this. I am a music loving lawyer and I think I have a longer than average attention span. Also I have a bit of an idea about Hi-Fi; For example I have hundreds of hours of elbow grease in modifying turntables. I do like technical explanations. It is more than obvious that you have serious content. You are providing a fabulous service to the audiophile community. And for this I thank you. As a trial lawyer I know that to get results you need to hold your audience's attention. This is a different skill. I guess you can call it something like 'brevity' or 'concentration'. What it amounts to is providing the same content with less words and with less time. I apologise for the patronizing tone but I will continue to give the thumbs up whenever (so far always) you provide such wonderful content.

[@Joshualbm]

I respectfully disagree zogster. I find these videos to be very thorough. Because our host's audience probably a big mixture of newbies, grouchy mid-fi bastards, aesthetic pedants, annoying audiophiles and idiots, sort of like a jury could be, there's a lot of ground to cover. So that everyone can get something useful to digest, there might be some things that you may find too basic or redundant that would be the "aha moment" for a moron. Since my personality runs the gamut of the aforementioned audience profile posit, I rest my case.

[@zogzog1063]

@@Joshualbm I guess you are right. The 'something for everyone' approach is not unknown. Another point that perhaps I should have acknowledged is the 'different strokes for ...' notion. For example many find the length of Beethoven's 3rd to be perfect. Others find it too long. In the present case the vid is too long for me but now that I think of it, it is because of covering ground that I already know.

[@Joshualbm]

@@zogzog1063 I hear you. That's why I like jazz.

[@-IE_it_yourself]

he references his conclusion with his thesis, that is the problem. he never gives and results and method. a drive sounds bad when it is out of phase, therefore when a driver is out of phase it sounds bad. when he does show a graph there is no comparison to show what is wrong, "look at this graph it has all this bad stuff here" what stuff do you mean, what are we trying to achieve and how can we manipulate it. Data/analysis and method of operations is generally lacking. nothing he said is repeatable. if i understood what he was talking about i could follow his points, but i dont that is why i am here, and im sorry to say, i have learned very little.