Unveiling the secret to vertically stacking speakers

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[@adrianbarac3063]

Yet another brilliant video. Thank you.

[@TheVid54]

Great answer.

[@BuffSquadBigBenni]

Love these videos. Thank you for sharing, Matthew.

[@PoesAcoustics]

Glad you like them!

[@Roof_Pizza]

Pop the jumper on the bottom pair and use the woofers only to augment the other full-range speakers, you might be surprised. I used the two pairs of binding posts on my amp so I can do a quick A/B and I've decided the pros outweigh the cons *in my setup.

[@PoesAcoustics]

Are you saying you stacked speakers but just used the woofers to Augment the other pair?

[@Roof_Pizza]

@@PoesAcoustics yup

[@howardskeivys4184]

👍

[@Nikita-P]

@@PoesAcousticssounds like mid-bass kick bass sub

[@CycleCalm]

I suppose the exception to this is Line arrays used in live sound, but the point of that is to give each area of a venue it's own beam of high frequencies, not sum together or aimed at a single sweetspot?

[@PoesAcoustics]

Completely different situation. A line array in pro is using purpose built line array speakers with tightly controlled directivity and DSP to align everything. They do combine into a single summed planar beam. However to achieve that they use specially designed speakers made to be slacked. The vertical spacing between the Hf drivers is very critical. It needs to be very tight. If you simply stack residential speakers together you cannot achieve that.

[@fonkenful]

Then there are line arrays designed for home audio use - e.g. Roger Russell IDS 25, and numerous DIY projects that definitely take comb filtering into consideration with a variety of filtering and shading methods. Danny’s own NX-Treme consists of 10 cone woofer / mid bass drivers and one planar / ribbon per side, so as always it’s the implementation that counts.

[@howardskeivys4184]

Thank you Matthew for answering my question. Your response was pretty much what I expected. I’m going to level with you:- I went against all good advice and vertically stacked 2 identical pairs of speakers. Each pair of speakers driven by separate power amps. Each power amp connected to the same preamp. In my humble experience, the benefits far out weigh the caveats. My normal listening level is around 78db. I can now achieve that level with the volume control on the preamp turned to 43. Previously I had to turn it to 51. Previously at a listening level of 78db the dynamic swing would max out at 96db, now that dynamic swing peaks at 104db! I can easily and seamlessly execute an A-B-C comparison between, top speakers only, bottom speakers only or both playing simultaneously. I can detect absolutely no change in frequency response/range, tonal richness, acoustic mass or soundstage. If there is a caveat, maybe, just maybe, the high frequencies are fractionally more directional, more beamy. This though may be psycho acoustics playing tricks with my auditory system, as so many people told me, that’s what I should expect to find. I may be totally wrong about this, but, because I now have twice the surface area of speaker cone, I now hear a much higher ratio of direct sound to reflected sound. Which surely diminishes the influences of the room. As for 100 experts and 101 differing opinions. A few good examples are:- Speaker placement. There is 1 camp that swears by the equilateral triangle. Another swears by the 38% rule. Another the 1/3 rule, Etc. Cables. 1 camp swears that cables do make a difference. The other camp swears they don’t. DSP. 1 camp swears it’s the best thing since sliced bread. The other camp proclaim it’s just another processing stage in the signal path, which can only cause degradation to the purity of the signal. The list goes on with each camp having its own expert/s, fighting their cause. room.

[@PoesAcoustics]

Don’t conflate the expert with enthusiast. Most of what you have there relates to arguments from enthusiasts. Not experts. Real experts don’t really debate these things so much. As for your flip stacking experience. To each his own. You have certainly introduced issues. If they don’t bother you, it may be that you really were missing out on dynamics. But then I think you probably would be happier with speakers that have 6dB more output. A very significant difference. That is what you need to try next.

[@PoesAcoustics]

@@Echo-jg8is that isn’t correct. If you add an identical speaker and do not add a second identical amplifier. That is 3dB. If the speaker can handle it and you add an amplifier that is twice as powerful that is also 3dB. If you add two speakers with two amplifiers, one each, that is 6dB. Each addition adds 3dB. If what you said was true, every room modeling software, acoustic software, and SPL calculator I’ve ever used is wrong.

[@Echo-jg8is]

@@PoesAcoustics Thanks for that, I honestly thought that having 2 of the same boom box's for example playing the same signal at the same volume would result in 3db gain and not 6db. 😬😕

[@PoesAcoustics]

@@Echo-jg8is well you doubled both the speaker area and power. Classic calculation for that with fully coherent summing is 6dB. For subwoofers, you will largely see coherent summing if you stack. With higher frequencies it all depends on the distance between drivers. We have actually done some testing in the real world to confirm the accuracy of these calculations with actual products in actual rooms. We generally see exactly what is predicted or within a dB or so.

[@alont93]

EDIT: nevermind I found mentions of it in a past video of yours. It was indeed RP, short for recommended practice. Hey Matthew thanks for another great video. You mentioned a few groups where you got to work with experts and those groups sounded like RP1, RP22 and a few others. A quick Google search didn't yield any results so I must have heard you wrong. Can you provide some more info about these groups? Thank you!

[@PoesAcoustics]

Yes I am on RP1, RP23, and RP32. I will be on RP22 once it regroups. I joined them after RP22 was well underway. I started out joining on behalf of Grimani and this past year joined on my own so my name shows up in the group.

[@pulDag]

The biggest issue is sound wave lenght of the highest frequency speaker driver radiates. (More) Tweeters must be in some kind of perfectly calculated array to overcome this issue (aligned as close as possible to reach other). Lower the frequency more spaced out drivers have be to overcome this comb filtering. Simple math. This issue can be seen on most horizontally aligned 2-way centers in MTM configuration where it is even worse because human is more sensitive in horizontal pane than vertical.

[@bingdong8571]

Couldn't u use a dsp and make separate boxes for tweeters, midrange, woofer, each with their own xlr outputs to go into a 3 way dsp. Then you could make truly modular speakers. Pro audio does it

[@PoesAcoustics]

Sure but that’s completely different. And you still have a number of issues. First you need to maintain correct center to center spacing for the drivers. Second, you need to know how to set the crossover. It makes no sense to stack a bunch of unknown speakers and set the crossover based on crummy in room measurements. High end pro audio speakers are not a bunch of separate boxes. They have the midbass, midrange, and tweeter in a carefully designed system. Even if they are active, the DSP settings are based on proper anechoic characterization of the speaker. You simply can’t equal or better that on your own. And again, taking two random bookshelf speakers and combining them won’t achieve this or anything good. It will play louder. A lot louder even. But it won’t give good sound quality.

[@bingdong8571]

@PoesAcoustics thanks the detailed response. I really think I'm gonna try this but just very slowly because part of the point would be to have multiple choices for woofers, mids, tweets so that will be a lot of speakers and boxes. Maybe ill try to build adjustable rail system for the boxes to fine tune. Either way it will be fun. Thanks for all.

[@dannyrichie9743]

One of our customers sent me over a link to this video a few minutes ago. You are 100% correct regarding stacking full range speakers and subwoofers. I shot a video 4 years ago on stacking speakers and showed what happens via measured responses. It also confirms what you just said in this video. kzbin.info/www/bejne/Zni7dpykmpmdpsksi=eDTo7RELrGpsTq16

[@PoesAcoustics]

Hey Danny. I figured there was a misunderstanding. I initially misread the question and thought they were suggesting that you were claiming that stacking subwoofers would cause such issues. Then I realized they conflated the notion of stacking subs (one issue) vs standing speakers (a whole different issue). I also did a video for Gene on flip stacking where I also measured the results. They were terrible. I presented the data and showed why it was so problematic. I am still at a loss why people are doing this.

[@pulDag]

​@@PoesAcousticseasy. Most people always thinks they know better. Thank you for your education, Matt