uhmm…. Sounds like the Fulcrum approach may not offer any advantage.
This concept from kimmo‘s website over a decade ago, is intriguing, the Helmholtz absorber I assume, reduces the cabinet resonance, flattening the impedance spike, but does it also it’s attenuating the back wave? However the Q of the absorber will mean the attenuation won’t be constant over a wide frequency band.
This concept from kimmo‘s website over a decade ago, is intriguing, the Helmholtz absorber I assume, reduces the cabinet resonance, flattening the impedance spike, but does it also it’s attenuating the back wave? However the Q of the absorber will mean the attenuation won’t be constant over a wide frequency band.
Kimmo described it as variable volume resistance enclosure.
From the description in this archive it seems the helmotz part act as a filter:
https://web.archive.org/web/20170905054902/http://kimmosaunisto.net/CardSub/CARDSUB.html
The design presented in the link seems well tuned and gives good directivity behaviour below 500hz but seems to lack overall level capability.
With 2x12" maybe it's better?
From the description in this archive it seems the helmotz part act as a filter:
https://web.archive.org/web/20170905054902/http://kimmosaunisto.net/CardSub/CARDSUB.html
The design presented in the link seems well tuned and gives good directivity behaviour below 500hz but seems to lack overall level capability.
With 2x12" maybe it's better?
I don't know. Geithain monitors are a great example of good monitoring and great use of the principle, Genelec most recent subs are cardio too.
And i must say i've not encountered any studio implemented with multisub.
All in all i think it's great to have multiple options availlable to taylor to your own needs/preferences.
And as i have been involved into multisub implementation ( two times ) i won't say it is easy to implement: you need a bunch of da, cables with them, multiamps, a way to manage levels if not done in digital... it can be complicated quickly and can looks a lot like implementing a real theater system. And seting things up is not as easy as it seems: one of the guy i helped won't hear about measurements ever... happily he liked the results but the way to get there was sour to him.
And i must say i've not encountered any studio implemented with multisub.
All in all i think it's great to have multiple options availlable to taylor to your own needs/preferences.
And as i have been involved into multisub implementation ( two times ) i won't say it is easy to implement: you need a bunch of da, cables with them, multiamps, a way to manage levels if not done in digital... it can be complicated quickly and can looks a lot like implementing a real theater system. And seting things up is not as easy as it seems: one of the guy i helped won't hear about measurements ever... happily he liked the results but the way to get there was sour to him.
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It's like the old question of where to set your baffle step. Many allow it to happen above the room's Shroeder frequency. After thinking about, it many choose not to take it to the next step.. So not much is talked about, perhaps the low sensitivity we have to reflections in the midrange, so excuses not to do it.
That really depends on the setup but often 3 subs are enough.
Two of them can often be around the front mains anyway, you just have to hide one or two somewhere else?
That does tell something about the general acoustics knowledge of the average studio guy. Man they are conservative…
I was trying to be nice and polite about it, lol
But yes, the majority things that it's only to produce more bass. Doh!
Toole's book has been around for over a decade now. Go figure.
It can be enough. Or not. It depend how you approach things: STEREO subs close to loudspeakers, ok. Are they an added way to loudspeakers or independent subs part of a multi sub approach?
In the implementation i talked about we defined them as belonging to monitoring and implemented 3 more independent subs. Grand total: 2 more ways for augmenting loudspeakers, 3 mono ( M extracted through M/S processing+ eq+ xover) independent multi subs. At minimum 3 dacs which ended up as 5 dacs for individual processing ( eq) and level control through digital means.
I will not detail lines needed to drive the plate amps, supplementary main lines needed to give juice to all this... and as domestic room everything has to be non obstrusive in other use including the sub box...
All i want to say is it's not for everyone imho despite for small room specifically it's one of the few solution.
And there is the rendering: it doesn't please everyone.
Yes average studio guy. But i spent time in Hidley's, Malcur's, Lafont's or Deluc's designed rooms ( you might not know the french's one but they are on par Hidley reputation), seen and heard Exigy Limited owner's designed room ( including Exigy loudspeakers) or T Jeanjouan's room: none were multisub implemented.
But we are talking different requirements: control over a wide area is not a requirement as long it is ok at listening point ( i'm not saying it is unavaillable in some of this room either as i've heard this on some rooms).
I've heard Gethain monitoring but not on a room build around them but i'm sure it could give a usable rendering.
Why would one have stereo subs?
The human ability to hear directional sounds (stereo) below 100Hz is practically zero.
In addition, room modes would mess that up completely.
Harman/Toole (and also Geddes) clearly showed that with 4 subs everything can easily made well.
Or the Geddes approach is two subs + an additional one randomly placed.
It is in any case better than one sub, even if it's not perfect.
Even for a single listening position.
Granted, that position could be accidentally in the perfect spot, but those changes are so extremely rare.
A cardioid system would do the same thing, just with a lot more hassle and less output.
If it's a dedicated studio room anyway, just shove a sub in every corner (more or less).
Camouflage one as a plant bin or something.
Get some decent 4 channel amplifier with DSP, start some measuring, calculate and simulate;
https://www.andyc.diy-audio-engineering.org/mso/html/index.html
Done.
How is that difficult and not pleasing?
The human ability to hear directional sounds (stereo) below 100Hz is practically zero.
In addition, room modes would mess that up completely.
Harman/Toole (and also Geddes) clearly showed that with 4 subs everything can easily made well.
Or the Geddes approach is two subs + an additional one randomly placed.
It is in any case better than one sub, even if it's not perfect.
Even for a single listening position.
Granted, that position could be accidentally in the perfect spot, but those changes are so extremely rare.
A cardioid system would do the same thing, just with a lot more hassle and less output.
If it's a dedicated studio room anyway, just shove a sub in every corner (more or less).
Camouflage one as a plant bin or something.
Get some decent 4 channel amplifier with DSP, start some measuring, calculate and simulate;
https://www.andyc.diy-audio-engineering.org/mso/html/index.html
Done.
How is that difficult and not pleasing?
Hey on Page 21 are measurements of my prototyp.
https://www.diyaudio.com/community/...eaker-insipired-by-d-d-8c.369939/post-7039293
I print it upside down. The tweeter Area was down.
Yeas i make my own waveguide for the tweeter and it took 4 prototypes.
Hi everyone. I think the key is to obtain an accurate polar plot and have a standard anechoic chamber to obtain the directivity plot of our speakers. I've searched many websites but there is no source for a small size ( I mean less than 2x2x2 meters) chamber that I can place in my room. I'm not allowed to perform the measurements outside because of neighbors. So, If you have a source about a small size anechoic chamber introduce it, please.
One time I forgot to check my levels when measuring a B&C 8NDL51 and I ended giving it around a hundred watts in a pink noise sweep. I think you could hear it a mile away. Whoops!
For your measurements, your best bet is to do them with a gate above 300hz-ish and do them nearfield for the lower frequencies then do your best to combine the two measurements.
I have a friend who builds speakers and lives in an apartment, and he gets clean measurements by taking the speakers out to a local parking that's deserted on the weekend. He's also measured speakers in the desert to get the noise floor down, but that's Next Level!
Parts Express sells dozens of amps that run on 12V, and you don't need a ton of power to make a good measurement, so you should be able to buy something cheap and just plug it into the cigarette lighter of your car. Just watch the current requirements so you don't blow a fuse. Or, y'know, buy a dedicated car amp.
Hi Sonce. Thank you for your response. I know the said anechoic chamber will not work in low frequencies. I think the hardest part of directivity control is mid frequencies and lower midrange ( about 1000 Hz). Because the polar behavior is unpredictable. I've found a source for a test chamber but the user is not able to rotate the speaker inside it. I mean something like this. If it is possible to implement it for an anechoic chamber it will be great. I should say its method is to use a calibrating curve to adjust the created bump in low frequencies.
https://audioxpress.com/article/pra...me-a-guide-for-building-your-own-test-chamber
https://audioxpress.com/article/pra...me-a-guide-for-building-your-own-test-chamber
Good idea but I'm looking forward to making a chamber. It will be the solution of many problems.
What is that chamber going to bring you that a gated measurement will not? Did you explore modern measurement techniques? Attached results were acquired in a room 8’ tall, 16’ wide and 27’ deep, measured at 3’ distance from the speaker. Valid up to 300Hz, the caveat being the resolution isn’t very high either.
Attachments
For those frequencies you don't need any anechoic chamber. Gated measurements with REW, ARTA or CLIO works equally well in a ordinary living room.
That chamber is for measuring drivers only, on-axis.
Once again: you don't need an anechoic chamber for measuring directivity at midrange frequencies.