Oh they're nice.. are you trying to better them with this build?
http://www.electrovoice.com/product.php?id=2583
The QSC's have quite a few issues that I don't really feel like going into right now but I'm already way past bettering them. They've served their purpose for the past three years and it's time to upgrade.
Sorry I wasn't trying to suggest the QSCs were the end all be all of powered speakers, they're a decent little box but they have been bettered by subsequent releases by QSC and others and I'm sure they can be bettered with a DIY design.
I am still working on acquiring those B&C compression drivers. In the mean time the Daytons work, and I want to throw in a little story here.
I do live sound reinforcement with the same band every Thursday night, but it isn't in a permanent location so we always have to load in and load out our own equipment. And sometimes the band likes to change around their instruments. Today I was told we would be doing an acoustic night, just the lead singer, two acoustic guitars, and a minimal acoustic drum set lacking a kick drum. Naturally, this means I would have no need to bring my huge sub, thus saving effort. Oh yeah, and the group right before us was scheduled to cut into our setup time, leaving us an hour where we normally have two or three.
It's a trap.
My drummer shows up with his electric drums. No time to change setup, we'll be sending the kick drum through the Beta-12LTA drivers without a HPF. These are 12" drivers keep in mind, in a sealed enclosure.
I was surprisingly very impressed with the performance of the LTAs. Defiantly, the bass was lacking impact. But it wasn't as if the kick drum was absent by any means. The over all level actually blended really well with the two acoustic guitars.
Beta-12LTA is a real workhorse. I will post frequency response measurements as soon as I get them; as soon as I find big, empty space.
I do live sound reinforcement with the same band every Thursday night, but it isn't in a permanent location so we always have to load in and load out our own equipment. And sometimes the band likes to change around their instruments. Today I was told we would be doing an acoustic night, just the lead singer, two acoustic guitars, and a minimal acoustic drum set lacking a kick drum. Naturally, this means I would have no need to bring my huge sub, thus saving effort. Oh yeah, and the group right before us was scheduled to cut into our setup time, leaving us an hour where we normally have two or three.
It's a trap.
My drummer shows up with his electric drums. No time to change setup, we'll be sending the kick drum through the Beta-12LTA drivers without a HPF. These are 12" drivers keep in mind, in a sealed enclosure.
I was surprisingly very impressed with the performance of the LTAs. Defiantly, the bass was lacking impact. But it wasn't as if the kick drum was absent by any means. The over all level actually blended really well with the two acoustic guitars.
Beta-12LTA is a real workhorse. I will post frequency response measurements as soon as I get them; as soon as I find big, empty space.
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Yes I've had many nightmares about being thrown into situations that were out of my control regarding live sound. One thing I have learned is that if anything can go wrong it will go wrong.
If you ever want to build a stellar sub I recommend an onken style enclosure being driven by the latest class D amps.
I was not previously aware of the Onken style design. To my new understanding, it's basically a large reflex alignment box? At this point I'm trying to get smaller, however. heh
Have you had any experience with the Cubo 15/18 or Cubo Sub or similar types of designs? They seem appealing because of retaliative small size and good extension/sensitivity.
Have you had any experience with the Cubo 15/18 or Cubo Sub or similar types of designs? They seem appealing because of retaliative small size and good extension/sensitivity.
Found this! http://www.diyaudio.com/forums/subwoofers/227548-dual-15-subwoofer-project-complete.html
Good Job--looks great.
Good Job--looks great.
I've seen the cubo designs but I've never heard them before. Two things stand out about the cubo that concerns me, first is the lack of any imperial data regarding frequency response and efficiency. Secondly the horn length is very short and therefore would not provide any low frequency extension which is probably why I haven't been able to find any data on it. The onken style enclosure is a very large box, but it's been my experience that to get good pitch definition you need a large box. I've seen people dismiss the onken design but after a lot of thought I think it's doing something a little more than a basic bass reflex function. It seems as though the symmetrical slot openings are coupling all the air inside the cabinet. In a traditional ported enclosure there are air pockets that act separate from the main event causing rippled in the impedance and FR curves. The result is less pitch definition since there are spurious acoustical events inside the cabinet.
You have me interested now. For various reasons including the one you stated, I have tried to avoid ported enclosures. Another big reason is as power increases port tuning increases in frequency-- not good!
The sub I built is sealed, but it's sealed isobaric push-pull. I am a huge proponent of isobaric push-pull. I don't have all the empirical data assembled to claim it can't be beaten by a single driver in cost or/nor performance, but I like what I've read and heard empirically.
As a home theater sub, what I built is fantastic. Plenty of extension with more clarity than you could dream of at the price point for the drivers I selected. It doesn't do fantastically on stage though. Just well. It's a good sub, but it isn't amazing like I want it to be.
As you may or may not know, isobaric configuration reduces the Vas to half of the single driver, thus reducing box size requirement by half. Unfortunately, it isn't all magic as you are still required much physical space to link two drivers where there would otherwise be just one.
None the less, I would like to get your opinion on the theoretical possibility of combining onken with isobaric push-pull. Based on your experience, is reducing the Vas of the drivers by half a good thing in the onken alignment? Would reducing the Vas translate to reducing box size in onken? If the answers to these questions are yes, then I will seriously contemplate building an onken box.
I will probably build a Cubo-something along the way anyway, if nothing else to take measurements. If it does actually work I rather like the concept.
Yes isobaric will also work with the onken enclosure thus reducing the required internal volume to half. The other benefit is that the effective Fs of the drivers is cut in half so for example if your pro audio drivers have an Fs of 40hz, you would now have an Fs of 20hz! There is no free lunch though. With a traditional dual onken each drivers efficiency is combined so 92db x2 = 95 Db. But with an isobaric configuration your looking at 92 Db /2 = 89 Db. Which is why you don't see it used in pro applications. However for home theater it's perfect. Save space, get deep bass, and class d power is cheap. Isobaric does have another advantage too which is lower distortion, especially if the drivers can oppose each other, thus cancelling out the physical non linearities in the cone's travel. Also any non linearities caused by poor motor design will be overcome, so bad drivers tend to sound their best aka cheap inexpensive drivers on clearance from parts-express.
You know your stuff!
Ahh, the language of happiness to me!
Just so it's unnecessarily clear, you say opposing and I say push-pull, meaning the same thing.
I went out on an unproven limb on a whim and actually made quadruple opposing drivers. Two of the drivers are push-pull magnet-magnet, the other pair is push-pull cone-cone.
I have yet to determine if it actually helped to further decrease distortion. The result of the dual opposing pairs--whether or not there are benefits beyond a single opposing pair--was not immediately evident.
Ahh, the language of happiness to me!
Just so it's unnecessarily clear, you say opposing and I say push-pull, meaning the same thing.
I went out on an unproven limb on a whim and actually made quadruple opposing drivers. Two of the drivers are push-pull magnet-magnet, the other pair is push-pull cone-cone.
I have yet to determine if it actually helped to further decrease distortion. The result of the dual opposing pairs--whether or not there are benefits beyond a single opposing pair--was not immediately evident.
When I say apposing I mean either back to back or front to front. Some designs are back to front ,like standing in a lineup for example. The other thing is that isobaric doesn't require identical drivers. You can even use the next size down if that simplifies cabinet construction.
The mass of air trapped between the two drivers contributes to lower the Fs. I would think magnet to magnet would allow a larger air mass thus an even lower Fs, but we are talking only a few Hz as compare to cone to cone.
My father has a sony push pull subwoofer (sa-wx700) that is very clean sounding and goes very low. Another great design although not isobaric.
The mass of air trapped between the two drivers contributes to lower the Fs. I would think magnet to magnet would allow a larger air mass thus an even lower Fs, but we are talking only a few Hz as compare to cone to cone.
My father has a sony push pull subwoofer (sa-wx700) that is very clean sounding and goes very low. Another great design although not isobaric.
Exactly, that is precisely what I mean by push-pull. When drivers are apposing, one is pushing in the instant the other is pulling. Forgive my slip of interchanging apposing with opposing, it was late last night.
Right, so those designs wouldn't be push-pull. The only reason for confusion I can see is you can design a push-pull speaker without isobaric alignment, for example with two radiating drivers in a single enclosure, one being turned "backwards" in relation to the other. This is also considered push-pull. I have adopted most of my terms from this website Audio Innovation - by Dan Marx www.danmarx.org And Vance Dickason calls it push-pull isobaric too I believe in his book.
Until now I have only heard the opposite of this. I've always read you must use identical drivers, otherwise you may get the worse of both. Also, if you link a 21" driver with a 15" driver, the 21" would have it's effective xmax cut in half. I can't imagine very many if any instances where mis-matching drivers is a good thing, but I would love to be enlightened if you know otherwise.
This is true, and honestly may be the source of my disappointment. I have been evaluating the cost and effort of switching the cone-cone pair around for dual magnet-magnet pairs. Then I saw the cubo sub design and noted it would be extremely easy--virtually free--to do cone-cone isobaric alignment. As to boot, the drivers can be flipped either way in the cubo designs.
I think another dissatisfaction may come from the xo I am using. It's currently a Radio Labs stick on, I think much could be gained from using a driverack or similar speaker management.
Cool!
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Darn, the B&C DE120 is out of stock until 3/20/2014.
In the mean time, I don't think I will be able to pursue an onken enclosure due to height increase requirements. Assuming the box compliance remained the same, (which it won't) I would still have to add several inches to the height of my already huge box. It is barely just not too big as it is. Attached is a photo with the grill removed to demonstrate the tight spacing of the 18" driver. Maybe I could downgrade to 15" and keep the same box size, but I really don't want to lose SD. I already get plenty of depth from this isobaric configuration, so porting isn't precisely advantageous to me.
In the mean time, I don't think I will be able to pursue an onken enclosure due to height increase requirements. Assuming the box compliance remained the same, (which it won't) I would still have to add several inches to the height of my already huge box. It is barely just not too big as it is. Attached is a photo with the grill removed to demonstrate the tight spacing of the 18" driver. Maybe I could downgrade to 15" and keep the same box size, but I really don't want to lose SD. I already get plenty of depth from this isobaric configuration, so porting isn't precisely advantageous to me.
Attachments
Found this: "Push-pull drive is particularly attractive when used in a horn subwoofer. The front chamber and mass-rolloff tend to reduce third and higher harmonics. Push-pull drive reduces the second harmonic. This in addition to the already low distortion due to reduced excursion from horn loading. Horn subwoofers with push-pull drive offer excellent low-distortion performance even at very high power levels."
Here: AudioRoundTable.com: Pi Speakers => Push-pull verses shorting rings
The cubo design looks even more attractive, although I think the designer does not claim it is an actual "horn" but simply calls it a "hybrid." What he means by that is not something I am aware of.
Here: AudioRoundTable.com: Pi Speakers => Push-pull verses shorting rings
The cubo design looks even more attractive, although I think the designer does not claim it is an actual "horn" but simply calls it a "hybrid." What he means by that is not something I am aware of.
The cubo concerns me because the back of the driver is exposed which would cancel out any sound waves that are longer than the length of the horn.
The b&c website has plans for a similar design type horn but they've wisely enclosed the back of the driver. This design gives good extension down to 40hz.
I've learned a lot from studying various manufactures suggested designs. They know what they are doing.
http://bcspeakers.s3.amazonaws.com/2013/02/12/16/15/57/205/file
Fostex includes plans with their drivers and they are in Japanese, but man they seem to have an attention to detail and at first you wonder what the heck they are doing but then it all comes together. Unfortunately they are not available online.
I ordered my DE120's and the ME20 horn together because b&c added special mounting holes to that particular horn special for the de120 since it's so small. It's a tiny little thing, but it sounds marvellous.
The b&c website has plans for a similar design type horn but they've wisely enclosed the back of the driver. This design gives good extension down to 40hz.
I've learned a lot from studying various manufactures suggested designs. They know what they are doing.
http://bcspeakers.s3.amazonaws.com/2013/02/12/16/15/57/205/file
Fostex includes plans with their drivers and they are in Japanese, but man they seem to have an attention to detail and at first you wonder what the heck they are doing but then it all comes together. Unfortunately they are not available online.
I ordered my DE120's and the ME20 horn together because b&c added special mounting holes to that particular horn special for the de120 since it's so small. It's a tiny little thing, but it sounds marvellous.
Your concern is duly noted.
Looks like research needs to be done. In the near future I will put my spare time towards understanding the cubo designs.
Today I spent a lot of time evaluating the PPSL design concept. Interestingly enough, it would be possible to apply my 4 18" drivers towards a dual isobaric pair PPSL onken hybrid alignment. Just combine all the things!
Apposing isobaric + PPSL is redundant. There seems to be a lot of advantages to PPSL but I still favor isobaric at the time of this posting.
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There are response graphs for the Cubo in the forum pages on freespeakerplans, I don't think it can be considered to be a horn as it's just too small but it delivers the goods regardless. I was curious about it so I built a 15 extended version last fall with a driver I had in a reflex box and sure enough it's about 3-9db more sensitive between 35hz and 100hz.
Thanks for the feedback! Did you notice any audio quality differences with the cubo vs the reflex box?
Response is somewhat peaky with the Cubo so it will require more EQ to flatten. There are 2 driver loading options too, frame out or cone out and each one produces a slightly different response. I have not had a chance to measure it cone out but my ear tells me that config produces a smoother response.. in my listening room at least. I noticed both the cubo and reflex box have a similar peaky response when I measured them originally so obviously the room is affecting things.
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