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Discussion Starter #1 (Edited)
Hey ya'll,

For fun and entertainment purposes, I'm going to be messing around with 21" drivers for a while. To start with I picked up 4 Lavoce San214.50's.

Before we EVEN GET GOING don't talk to me about devastators or whatever. Not interested -at all. No offense to the wonderful sirs who have played a role in the development, I just like doing my own thing.

Main use: music. Before anyone starts spouting off about mid bass, I listen to stuff that goes low. "Ohhh but Chris, you fool, that's such a tiny percentage of music" Again, stop. If what I'm listening to doesn't go low enough, then I use a subharmonic synth to make sure damn near everything has fun (tastefully added, mind you) content down to around 15hz. So there. :p

Bottom line: I do the things I do for a reason.

Now let's talk preferences: I like sealed, low q alignments, low group delay and once in room, healthy boost down low. Easy to eq, smaller, not very efficient. That was all fine and well until I reached the point I couldn't really pull more power out of the available outlets for the next step up. I did a "re-think" about the system, locations, and resources and decided to constrain my bass duty's to no more than say, 3-4 crown xls2502's, which'll each do about 2400 watts into 4 ohms, but I have a slew of 1502's I could use should I need to.

I've designed and built very pleasing vented designs, but there are a couple things I really don't like; vent noise, chuffing of any sort, vent resonances that land in the (critical) upper bass. There are ways around this, but they all get harder and harder to employ when you want something that digs extremely deep.

I've also built some very satisfying passive radiator designs that seemed to combine the best of both worlds, of course at the expense of the passive radiator itself; it's (almost) always more expensive to do a PR sub vs vented. For the purposes of this build I simply decided to not care.

I decided on the San214.50 as the performance was outstanding and the cost was reasonable. They're 8 ohms, which simply means I should have dual drivers in each cabinet when all is said and done, or at least co-locate them if they're sealed.

Step 1: Buy drivers. Done.
Step 2: Build bs test box, about 6cuft, sealed. Done.
Step 3: Install and test single sealed driver in test box. Mostly done.
Step 4: Procure 21" passive radiator sample. On the way
Step 5: Install and test single 21" passive radiator sample (or samples, if I get more than one vendor). Not yet.
Step 6: Extrapolate in-room findings with test box into final design.
Step 7: Get the big ones built.
 

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Discussion Starter #2 (Edited)
So, let's talk PR's. I went on the hunt for 21" and 24" PR's. There really aren't any available. Stereo Integrity didn't respond. PSI told me they could make me one if I supplied them a 21" frame, which I acquired and shipped to them. Radio silence since, which isn't totally unexpected given the world situation. I'll update when and if I ever hear back. Side note: this isn't really economically feasible since I paid to get the stupid frame, then paid to ship it to PSI, which cost about a trillion dollars. I'll ride this one out in the event their PR's are the best PR's the PR world has ever seen.

Enter Mark at Mach5 audio. He was very responsive, we agreed on a price, and he started building it a little while ago. It's done, he'll ship to me sometime this week. See pics.

So, a couple sims are presented. It's really important to note this is not the final desired anything. I arbitrarily chose 6cuft as it was convenient and close enough to other designs (on a volume/driver basis) it wouldn't be hard to correct for results. It's going to raise the tuning of the PR compared to the (projected) final design, but it's low enough to be useful for test purposes.

Unmolested, here are the Mach5 PR parameters (no mass added)
Fs: 17.9hz
Qms: 8.7
Vas: 18.33 cuft
Cms: 0.136 mm/N
Mms: 580g
Rms: 7.45 kg/s
Sd: 1640sqcm

One way linear travel is "greater than 2 inches", which means one PR per LaVoce should be adequate. Particularly in light of how much power I'm going to give the LaVoce's.

For test purposes I'll be bringing Mms up to 2230, which will drop Fs to 9.139hz, raise Qms to 17.19. Final design wise, depends on how this behaves under tuning, but I'm prepared to add up to 3kg if needed.
 

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Discussion Starter #3 (Edited)
Test Box vs. Final Design: Initial thoughts, test box problems, etc.


1: Sealed cube = easy
2: Passive radiator with big surface area tuned low in small(ish) box = lots of mass
3: Lots of mass = she's going to dance pretty good. May need wife to sit on it for sweeps. (heh)
4: Fine for test box, but final design will have 2 PR's, dual opposed for force cancelling reasons
5: Hey, number 4 above works pretty good with the concept of running two San214.50's per box!

The test box is just rudimentary proof of concept, I'm too lazy to go through the hassle of a good test box build. I know how to do all the "correct" things, this is good enough for me to run some sweeps, listen a bit and let that info shape my next iterations.

Chris
 

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'then I use a subharmonic synth to make sure damn near everything has fun"

not to go too far OT
but
that ULF synth output
and the lack off any reliable source for such a signal was one of the major speed bumps
in the further development of
the DIY Rotary Subwoofer

Chris Hudlin – 19/04/15. link to this file:
http://www.filedropper.com/diysubwooferguidebychrishudlin


please , sir, .
tell us more about that synth

TY and now, back to your regularly scheduled thread . . .
 

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Following with extreme interest!


Sent from my iPhone using Tapatalk
 

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Discussion Starter #7
Update: Was suggested to try Pierce Audio by a nice sir here at AVS who sent me a PM. Shot them a message and will see what they say. Their models look kinda pricey but we'll see.
 

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sorry, that link pulled from the archives . .
I actually have that article as a PDF, it's 12 pages so no attachment here
To all interested , shoot me a pm - we'll find a way
TY
 

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Discussion Starter #10
'then I use a subharmonic synth to make sure damn near everything has fun"

not to go too far OT
but
that ULF synth output ...


please , sir, .
tell us more about that synth

TY and now, back to your regularly scheduled thread . . .
So, I have a bunch of different subharmonic synths. Hooked up to the computer system is an old AudioControl Phase Coupled Activator Series III, with the high pass chip tweaked from the factory 25hz at 18dB/oct to somewhere around 16hz (same slope). It is the epitome of adding distortion but man oh man can a little grumble add to enjoyment. I have other versions, other brands like some sought after dbx versions with individually adjustable aggression per frequency range, not all have I tweaked the same way -for example the subharmonic synth I use in the main system has the HPF at 7hz. This is profoundly different, and harder, on parts. I think I measured once that I use about 10x the power with it engaged "spritedly". Use with caution, you WILL blow your **** up if you're not careful.

You can see main tone, and subharmonic just above the knee of my high pass. You can also see that switching in "range" on the PCA Series III adds some third harmonic. This isn't driver distortion. FWIW, this graph shows it turned up pretty loudly. You wouldn't normally listen with that much subharmonic info added.


Chris



Chris
 

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Discussion Starter #11
I re-adjusted my subharmonic settings on the computer and grabbed an RTA capture from a mic in front of the sub for the same 15 seconds of the same song (Play Me Again by Kid Francescoli because that's what happened to be playing while reading this:
capture is from 3:30 to 3:45.

With and without the subharmonic synth set to what I consider the aggressive side of clean.

This song isn't demanding. Give it a listen, you could play it on literally any speakers. Add the subharmonic synth and she's pretty much full scale to 25hz, strong to below 20hz. Remember, this is on the system that only uses 4 12" JBL's (right by my feet), so they're high passed higher than I'd normally like. Maybe I'll swap to some 21's under the desk when this is all done. ;)

Chris
 

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Awsome project, will be very excited to follow ;)
 

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Chris,

Interesting project!

Unmolested, here are the Mach5 PR parameters (no mass added)
...One way linear travel is "greater than 2 inches", which means one PR per LaVoce should be adequate.

If that much travel is available on smaller frames, and relatively small boxes, perhaps a pair of 18's or even 15's would be sufficient, at substantially lower cost.
 

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Discussion Starter #14
Chris,

Interesting project!




If that much travel is available on smaller frames, and relatively small boxes, perhaps a pair of 18's or even 15's would be sufficient, at substantially lower cost.
Yes they would be (for the most part) sufficient, at least on the 18" front, and no I am not interested in going that route. See first post: "I do things I do for a reason". :)

Chris
 

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Sounds very interested indeed. And sounds very similar to some of the music I listen to. Nigel Stanford, Phutureprimitive, Solar Fields, etc.

My plan is to cover those frequencies with a ridiculously large horn ...
 

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I just finished two sealed Eminence NSW 21's. I'll be watching your build closely. Perhaps I'll do mine with 18" PR's (two per driver) in the near future since due to limited space, I have to keep the boxes on the small side. When you say 6cf, that's internal, correct? What are your box dimensions? Tuning in the mid-teens would provide you with great low bass with awesome mid-bass.
 

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Hmmmmmmm ...... from a zillion sealed JBLs with CNC'd boxes from China ... to custom PRs ...

Okay, have fun. But please don't lose the forest for the trees. I have mentioned before the 'numbers chasing' aspect of this. As in my own pride & obsession chasing RWHP numbers... and losing sight of actually getting out on the road and DRIVING! I hope that you can build something and ENJOY IT! I sincerely don't want to step on toes, but I see more and more of the obsessional sort of 'chasing' that tends to leave people perpetually unsatisfied all over this forum (not specifically pointing at you, Chris). There is a quality quite similar to that of the addict that is always 'chasing' that becomes more & more prevalent as our culture loses sight of real meaning in life.

I do appreciate the self-deprecating use of 'Foolishness' in the thread title! Just try & smell the roses along the way ;)
 

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Discussion Starter #19
Hmmmmmmm ...... from a zillion sealed JBLs with CNC'd boxes from China ... to custom PRs ...

Okay, have fun. But please don't lose the forest for the trees. I have mentioned before the 'numbers chasing' aspect of this. As in my own pride & obsession chasing RWHP numbers... and losing sight of actually getting out on the road and DRIVING! I hope that you can build something and ENJOY IT! I sincerely don't want to step on toes, but I see more and more of the obsessional sort of 'chasing' that tends to leave people perpetually unsatisfied all over this forum (not specifically pointing at you, Chris). There is a quality quite similar to that of the addict that is always 'chasing' that becomes more & more prevalent as our culture loses sight of real meaning in life.

I do appreciate the self-deprecating use of 'Foolishness' in the thread title! Just try & smell the roses along the way ;)
Dude, this IS the AVS DIY section! I have had fun all along the way, and it's been stupid all along the way. Helped out a bunch of people with the sealed JBL's, gave dozens of demos, introduced people to extreme nearfield experiences, and spent countless nights with the lights down and my wife next to me drinking a glass of wine and listening to beautiful music together. She used to run a school that taught music to disadvantaged children. Not only that, but the secondary system (my computer/workstation/office system) is nearly a copy of the main system for now, and gets used every day, without exception. Plenty of rose smelling. In fact, at the pace I do things, that's mostly what I do. I just don't fool around with half doing things, if I care I do it right or don't do it at all.

I get where you come from, one of my jobs is working with a turbocharger company, and am familiar with that chase too. I try to talk people out of it, especially when what they think they want isn't really what they want. If it makes you understand any better, I never got sucked into dyno racing or even track numbers. I like my personal (fun) car set up to my liking, with somewhere around 600 whp which is fast enough to be fun, but it's no race car. The shop race car in that platform has about twice the horsepower and I'm uninterested in that chase. Mine though? It's set up the way I like it, how I like it, according to my view on "how things should be done" for my application.

Same with audio. I like doing things my own way. That isn't to say that I don't learn or get inspiration from others. I enjoy bringing something from a rough concept through to final product. Honestly these big pro drivers are just begging for a PR alignment IMO. Huge motors, huge cone area, respectable swept volume... low distortion.... we ain't gonna stack port turbulence on that list too. They don't have 21" PR's? Hell, let's make some! Here is how you do it.... :D

Chris
 

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Discussion Starter #20
I just finished two sealed Eminence NSW 21's. I'll be watching your build closely. Perhaps I'll do mine with 18" PR's (two per driver) in the near future since due to limited space, I have to keep the boxes on the small side. When you say 6cf, that's internal, correct? What are your box dimensions? Tuning in the mid-teens would provide you with great low bass with awesome mid-bass.
Cool! The NSW 21 is an awesome speaker. I bet you love them.

Test box is 23.75" cubed, or about 6.3 cuft internal, or about 6cuft when all is said and done. No stuffing, no bracing, she be a test box this ain't for pretty!

Final design will likely be quite a lot larger. Increases low bass efficiency and allows me to get by without putting absolutely stupid amounts of mass on the PR's. As it is, they'll have quite a lot of weight on them.

Dual 18" PR's would more than suffice, provided you could load enough mass on them in your enclosure to reach your tuning goal. The very pretty ones parts express sells won't even come close to holding enough mass. PSI would handle it fine, but their frames are large enough that you may have to saw them down (shared to me via Tom Vodhanel in a cool email chain). The Mach5 one I'm getting should handle it fine, but I'll speak more once it's in hand and passes some tests.

As far as price goes... depends on what you're looking at. The high excursion 18" PSI units are significantly more than the 21" Mach5 unit. I haven't heard back from PSI yet about the frame I sent them and the cost to turn into a PR.

Chris
 
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