Hello my name is Jack and im new to these forums.
I have been wanting to build a TL sub for a long time, but havent gotten around to it because of work.
But ever since i heard of the DTS-20 over at avsforum.com, i've been wanting one of those bad boys badly!
So after alot of snooping around in varous forums (here, prosoundweb and others) i've gathered alot of info on Tom Danley's "tapped" design, although most of it is speculative since the technology is so new and practically imposible to model (in affordable programs anyway).
I have made a litle spreadsheet with the DTS-20 driver spec's and two possible alternatives. (All in all I think the Infinity Kappa Perfect 12d VQ would be the ideal choice because of the variable Q feature).
Regarding the cabinet construction itself, there will have to be a bit of tweaking to the new driver since you can't model the "tapped" alignment yet.
I will post my bid on the precise cabinet dimensions modelled to the Infinity driver, when i get a program i can draw in (other than paint!)
The main design ideas for the cabinet can be seen in the next post's attached picture
(The picture is from someone elses post here but i cant find the post so i hope it is ok with him that i just post the image)
I have been wanting to build a TL sub for a long time, but havent gotten around to it because of work.
But ever since i heard of the DTS-20 over at avsforum.com, i've been wanting one of those bad boys badly!
So after alot of snooping around in varous forums (here, prosoundweb and others) i've gathered alot of info on Tom Danley's "tapped" design, although most of it is speculative since the technology is so new and practically imposible to model (in affordable programs anyway).
I have made a litle spreadsheet with the DTS-20 driver spec's and two possible alternatives. (All in all I think the Infinity Kappa Perfect 12d VQ would be the ideal choice because of the variable Q feature).
Regarding the cabinet construction itself, there will have to be a bit of tweaking to the new driver since you can't model the "tapped" alignment yet.
I will post my bid on the precise cabinet dimensions modelled to the Infinity driver, when i get a program i can draw in (other than paint!)
The main design ideas for the cabinet can be seen in the next post's attached picture
(The picture is from someone elses post here but i cant find the post so i hope it is ok with him that i just post the image)
Here is the cabinet design idea since you are only allowed to upload one file at the time:
(and it takes hours to get your first post approved)
And just to be clear, since i dident actually post a question:
In the "tapped-horn whitepaper" Tom Danley says that the driver used in the DTS-20 is nearly 200 grams in order to impedance match the driver to the air resistance in the TH design.
Using Thielesmall.com and various other sites, i have looked at T/S parameters of over 100 12" drivers from varous manufactures with the:
Mms = "...Almost 200 grams..." as starting point and to me the Infinity seems to be practically the only possible driver?
(The LAB-12 weighs in at only Mms 146 grams but has a stronger moter)
(and it takes hours to get your first post approved)
And just to be clear, since i dident actually post a question:
In the "tapped-horn whitepaper" Tom Danley says that the driver used in the DTS-20 is nearly 200 grams in order to impedance match the driver to the air resistance in the TH design.
Using Thielesmall.com and various other sites, i have looked at T/S parameters of over 100 12" drivers from varous manufactures with the:
Mms = "...Almost 200 grams..." as starting point and to me the Infinity seems to be practically the only possible driver?
(The LAB-12 weighs in at only Mms 146 grams but has a stronger moter)
Attachments
From the little research I've done, I suspect the driver is a modded Lab12, they may well have just added mass to the cone to make it suitable for the new system. It's certainly something you could look at, you could test with modelling clay, then replace with coins superglued to the cone.
I too, would love to have a go at this sort of design, if only more info was available, so I look forward to your results.
I too, would love to have a go at this sort of design, if only more info was available, so I look forward to your results.
pinkmouse said:
Greets!
Yeah, I'm thinking he doped a LAB 12 with the same compound (or very similar) to what's used on the Contrabass and BT-7 drivers since it also makes the diaphragm considerably more rigid/damped. Anyway, the extra mass only flattens its response and lowers its HF corner a bit, so having less for a HIFI app shouldn't be a big deal if there's any room gain.
GM
How about using two drivers in a pushpull or also called, isobaric arangement. That way you get twise the motorstrengt and twise the cone mass. The cancelation of even order harmonics is a good bonus too.
This is something I tried but in a very small scale. 2 4½ inch car speakers in a 240 cm long folded pipe with an slowly expanding crosssection area. 78 cm2 to 200 cm2
This is something I tried but in a very small scale. 2 4½ inch car speakers in a 240 cm long folded pipe with an slowly expanding crosssection area. 78 cm2 to 200 cm2
I made something similar to this very recently (very close external measurements), but mine has a 2:1 decreasing taper ratio instead of a mass loaded expanding taper. With the 14 foot pipe I have strong response down to about 16 hz, but without the strong bump at the tuning frequency as indicated in the DTS-20 FR charts.
I chose my driver by a very different method. I asked for help simulating different drivers in my concept tl with MJK's tl spreadsheets. I chose the Dayton Quatro 15 because it was cheap and the Jensen Transflex used a 15. It showed good response as low as I wanted to go.
More recently I have been thinking about a smaller driver with lower q to really bring out the most of the bottom end (6db or so peak at tuning like the DTS-20). The Lab12 popped to mind but I had no idea that other people thought it might work too. I was also thinking about a Peerless 12.
I am very interested to find out how your project progresses.
I chose my driver by a very different method. I asked for help simulating different drivers in my concept tl with MJK's tl spreadsheets. I chose the Dayton Quatro 15 because it was cheap and the Jensen Transflex used a 15. It showed good response as low as I wanted to go.
More recently I have been thinking about a smaller driver with lower q to really bring out the most of the bottom end (6db or so peak at tuning like the DTS-20). The Lab12 popped to mind but I had no idea that other people thought it might work too. I was also thinking about a Peerless 12.
I am very interested to find out how your project progresses.
TD mentioned at some point that the driver output on the side closer to the terminus has little impact on response. If this is true then we do have a way to model this tapped horn. My approach has been to use MJK's mathcap spreadsheet for a TQWT, but focus only on the predicted port output.
My goal is extension not extreme output, so I've moddled my plan using a 16ft line and a larger CSA using 2 15's (push/pull but not isobarik). The extra CSA and Sd shows very flat port output all the way down to 10hz.
Also, if it doesn't work I can always mount the drivers outside of the line and EQ down the response above 20hz.
My goal is extension not extreme output, so I've moddled my plan using a 16ft line and a larger CSA using 2 15's (push/pull but not isobarik). The extra CSA and Sd shows very flat port output all the way down to 10hz.
Also, if it doesn't work I can always mount the drivers outside of the line and EQ down the response above 20hz.
I've also checked out the peerless XXLS drivers but ended up with the Infinity bacause of the low Q's, high Mms and Xmax of 3.35 cm peak-peak wich gives it a VD of 822,4cc which translates into ALOT of headroom : ) Not to mention the variable Q feature and the dual 4 Ohm voice-coil for 2 Ohm or 8 Ohm operation.
The only "bad" thing i read about it was on caraudiomag.com where it did'nt score to high in a subjective listening test (80%)
- I don't take subjective tests in magazines too seriously anyways.
Actually that was my first idea. I thought about two 9" Scanspeak "revalator" 23W/4557T02 in push pull, mounted in a folded QWTH. But their low Qms/Qts and the fact that they cost alot more than the 12" Infinity driver made me look at the DTS-20 design, with extremely low distortion in the first place.
Anyway i think you loose alot of the benefit of push-pull (even-order distortion reduction) in open cabinets since the drivers does'nt "see" each other that much compared to sealed cabinets.
-I have'nt tried it, so i would'nt know for sure.
To GM and pinkmouse:
Even if i modded a LAB-12 to make it heavier (>Mms <Fs <Qes <Qts) dosent the Infinity driver seem to surpass it anyway?
-Or is it just me? ; >
I think John is right. From my experiences (unfortunately without an SPL meter) it looks like you can predict to an extent what will happen by modelling the driver in a tl enclosure program.
In my case the sensitivity seems close to the model, the harmonic peaks are in exactly the same places and low frequency extension is very close to the chart. I wouldn't try a new driver in my box without modelling it, which unfortunately I can't yet do myself. I was surprised when I got the Dayton Series II and the Dayton Quatro simmed. Both driver's specs are fairly typical, but the Quatro modelled about 6 db louder with the same power in the same tl.
Also, if you model it, I think you will find that the drawing you selected, if you stay with the DTS external measurements, will tune the box closer to 30 hz than the DTS's 20 hz. But very, very sensitive, very loud.
In my case the sensitivity seems close to the model, the harmonic peaks are in exactly the same places and low frequency extension is very close to the chart. I wouldn't try a new driver in my box without modelling it, which unfortunately I can't yet do myself. I was surprised when I got the Dayton Series II and the Dayton Quatro simmed. Both driver's specs are fairly typical, but the Quatro modelled about 6 db louder with the same power in the same tl.
Also, if you model it, I think you will find that the drawing you selected, if you stay with the DTS external measurements, will tune the box closer to 30 hz than the DTS's 20 hz. But very, very sensitive, very loud.
This is only true in the low end of the frequency range, When ½ wavwleght is produced the speakers are driving the horn with both back and frontside in a pushpull arranement. That is the "tapped" thing. You tap into the horn in two places..TDs white paper describes this quite well.
Johannes.
The Infinity Kappa Perfect 12d VQ spec. is on the last page of this document:
http://manuals.harman.com/INF/CAR/Owner's%20Manual/Perfect%20VQ%20OM%20FINAL%20
Where have you seen the modded LAB-12 spec?
Hmmm. I can't seem to get the direct link to work.
Try downloading the user-manual instead:
http://infinitysystems.com/caraudio/product.aspx?ProdId='KAPPA+PERFECT12DVQ'&Ser=KPE&Cat=SUB
Try downloading the user-manual instead:
http://infinitysystems.com/caraudio/product.aspx?ProdId='KAPPA+PERFECT12DVQ'&Ser=KPE&Cat=SUB
Circlomanen said:
Johannes,
TD said that the radiation of the driver side closest to the mouth is effectively decoupled from the horn at very low frequencies. Since I plan to cross mine in the 30-35hz range and my "horn" is 5m long, I interpret that all of the frequencies are very low.
The MJK spreadsheet sims show that only below 20hz, the backside driver output via the terminus will swamp the front output. That is fine with me because that's where the front output via the terminus starts to fall off, so I maintain over 90db output down to near 10hz. Add in floor+wall placement 1/4 space loading, not to mention room gain of my well sealed, mostly concrete walled, room, and potential output should be far greater than I need.
Greets!
I calc'd them based on adding 50 g of mass to the published specs.
Yes, the Infinity has a greater dynamic headroom WRT the LAB 12 driver if you have the amp power, but it will have to be mass loaded also to get comparable performance, though pipe CSA will be less due to its lower Vas. Like Al said though, without knowing the DTS-20's design details, there's no way to know for sure whether either of these can be modded to make them drop-in replacements.
GM
I calc'd them based on adding 50 g of mass to the published specs.
Yes, the Infinity has a greater dynamic headroom WRT the LAB 12 driver if you have the amp power, but it will have to be mass loaded also to get comparable performance, though pipe CSA will be less due to its lower Vas. Like Al said though, without knowing the DTS-20's design details, there's no way to know for sure whether either of these can be modded to make them drop-in replacements.
GM
Danley has said that his Unity horn inspired the tapped horn. I threw together three images in Visio, based on what he's saying. Or at least what I *believe* he's alluding to! Check 'em out here:
Is a tapped horn a unity horn?
In the meantime I'm building one!
:: PB ::
Is a tapped horn a unity horn?
In the meantime I'm building one!
:: PB ::
my take on this....
I think that Tom is saying that the So of a Tapped Horn should be equal to driver Sd. If you dropped the driver down along the path of the horn (from the apex) to where the cross sectional area equaled the Sd of the driver then you could use that space (above the driver) to open up the mouth (terminus) of the horn a little bit more which would not hurt. Regards Moray James.
I think that Tom is saying that the So of a Tapped Horn should be equal to driver Sd. If you dropped the driver down along the path of the horn (from the apex) to where the cross sectional area equaled the Sd of the driver then you could use that space (above the driver) to open up the mouth (terminus) of the horn a little bit more which would not hurt. Regards Moray James.
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