Summoning planet10
While horn enclosure build of altec 515 is almost done to death and is huge,
I am thinking is it possible to compact the whole enclosure by using troels Dtqwt design.
So my idea is having the 288 compression drive ，mid woofer 515 , and a bass woofer (have not decide which yet）at the back. This combo should be relative compact than the traditionsl build but also compensate the lack of bass extension of 515 woofer.
however I don’t know how to estimate the relative size or whether this idea is correct
I believe the crossover section are the usual suspects, 500hz and 50hz.
I am not requesting a fish but just want to know the feasibility and is their a reduction in size.
While horn enclosure build of altec 515 is almost done to death and is huge,
I am thinking is it possible to compact the whole enclosure by using troels Dtqwt design.
So my idea is having the 288 compression drive ，mid woofer 515 , and a bass woofer (have not decide which yet）at the back. This combo should be relative compact than the traditionsl build but also compensate the lack of bass extension of 515 woofer.
however I don’t know how to estimate the relative size or whether this idea is correct
I believe the crossover section are the usual suspects, 500hz and 50hz.
I am not requesting a fish but just want to know the feasibility and is their a reduction in size.
When i need a horn or TL i call on Scottmoose.
I am not impressed with Troels design, but i will let Scott wade in.
dave
I am not impressed with Troels design, but i will let Scott wade in.
dave
The 'problem' of doing any cab alignment with most vintage spec horn drivers is its huge Vas, so to go low with any efficiency = humongous since we're always trading efficiency for BW, hence the huge bass horns of our forefathers; that, or use multiple vented boxes to shorten the horns to a ~manageable size relatively speaking like the pioneers did re Altec's 210-211, 825/8 cabs, at least when perched on its narrow side plus some folks cut them in half longways to be single driver stereo pair and at least one DIYer cut off the back boxes and converted them to true corner loaded compression horns ('to die for' performance IME 😉).
Re 'compact' vented, the pioneer's Vb = Vas/1.44, Fb = 1.56x Fs yields its ~ max practical relatively high SQ reflex efficiency.
Re DT-TQWT, It requires dual 515s (front/back) or might as well just make a single fold over/under layout TQWT/Voigt/TL-horn or stretch it ML-TQWT/Ml-horn if floored tuned to a lower Fb/c*.
* Did I forget any tapered 'nom de plumes'?
Re 'compact' vented, the pioneer's Vb = Vas/1.44, Fb = 1.56x Fs yields its ~ max practical relatively high SQ reflex efficiency.
Re DT-TQWT, It requires dual 515s (front/back) or might as well just make a single fold over/under layout TQWT/Voigt/TL-horn or stretch it ML-TQWT/Ml-horn if floored tuned to a lower Fb/c*.
* Did I forget any tapered 'nom de plumes'?
Have a look at the thread "Beyond the Ariel". It comes to a system running the GPA 416 in a app. 90l closed box and it is good for 60Hz. I have also tried it and it works very well. The GPA 416 lands somewhere inbetween the Altec 416 and 515 so something similar should work fine.
Anders
Anders
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Your post just reminded me that we need to know which 515 the OP wants to use, though GPA's newest one seems the 'no brainer' choice if wanting < ~50 Hz.
Hmmm if using 416 I think I will just use oken cabinet design, since we have our best member detailed a document how to do it.
Although altec smaller cabinet does uses dual 515, Google told me there are people having success using single 515 on oken cabinet. Similarly David ls design used single 515 in one of his cabinet so I don’t think dual 515 is necessary (or maybe I am wrong for smaller size cabinet)
The woofer I am aim at is the OG 515 16g
Although altec smaller cabinet does uses dual 515, Google told me there are people having success using single 515 on oken cabinet. Similarly David ls design used single 515 in one of his cabinet so I don’t think dual 515 is necessary (or maybe I am wrong for smaller size cabinet)
The woofer I am aim at is the OG 515 16g
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In the DTQWTII of Troels the 2x10 "are crossed at 150 Hz, I suppose that the 1x12 version must be similar. This information does not appear on your page, he replied to me via email due to my curiosity when I built them...
original
So yeah I am using the concept of his cabinet but the drivers are different, so the crossover have to be changed to suit the driver.
The idea is explore the feasibility therefore the single 515 goes 50hz only, and let a morden 15 inch low vas driver do whatever it need below 50hz.
OK, ~37 Hz then and presume a digital 50 Hz/2nd XO, but can't ideally design a single cab with two differing spec drivers without knowing the other's specs since Qts dominates, so you'll need to choose it before anybody can help with any type of cab alignment.
I think we don’t need to go digital as the whole thing is aiming at high efficiency driver, and I doubt there is a woofer lesss than 15 inch and can be articulate and go deeper below in the region around 70hz and 30hz without plate amp.
Yes , the dedicated bass woofer is the Biggest caveat, because I can imagine that this Dtqwt would have a larger bottom, at the end a 18 inch might be more suitable than a 15inch.
As you have point out if qts dominates the whole design do you mean I need to seek a woofer which have similar qts as 515-16g which is 0.215, so it seems 18XL2000 a close match with it qts 0.27
P.s I was apply the logic design from troel I.e design the front first then design the back. Or maybe I should do it another way around.
Yes , the dedicated bass woofer is the Biggest caveat, because I can imagine that this Dtqwt would have a larger bottom, at the end a 18 inch might be more suitable than a 15inch.
As you have point out if qts dominates the whole design do you mean I need to seek a woofer which have similar qts as 515-16g which is 0.215, so it seems 18XL2000 a close match with it qts 0.27
P.s I was apply the logic design from troel I.e design the front first then design the back. Or maybe I should do it another way around.
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Well, you certainly don't want to go analog with a 50 Hz XO point if wanting high efficiency, ditto 70 Hz.
Hmm, let's reduce this to a max flat BR for simplicity's sake:
net volume (Vb) (L) = 20*Vas*Qts'^3.3
box tuning (Fb) (Hz) = 0.42*Fs*Qts'^-0.96
515-8G specs = 37 Hz/351.6 L /0.27 Qts'
Vb = 93.45 L
Fb = 54.62 Hz
?? woofer specs = 25 Hz/150 L/0.4 Qts'
Vb = 145.85 L
Fb = 36.9 Hz
So in the BW where the 515 dominates, it would be over damped in the big box and woofer under damped in the small box, so what we want at least to the first approximation is the mean between the two, so ATM I'm assuming that averaging these yields the same as my normally averaging driver specs for calculations:
sqrt(93.45*145.85) = 116.75 L
sqrt(54.62*36.9) = 44.89 Hz
Not optimal for either, but one that can be corrected with modest EQ if required, but as you can see, the closer Vas, Qts is or the sums of the two, the better and as for Troels' way, I'll need to read it and driver specs when I'm not so tired, just noticed he apparently did it using impedance curves.
Horns can sometimes complicate 'things', so his designing as a bi-fold with a common 'vent' is obviously a good plan for when some of the drivers can be on the rear.
Note that there's always some series resistance, but using Qts = Qts' for example:
[Qts']: [Qts] + any added series resistance [Rs]: http://www.mh-audio.nl/Calculators/newqts.html
Hmm, let's reduce this to a max flat BR for simplicity's sake:
net volume (Vb) (L) = 20*Vas*Qts'^3.3
box tuning (Fb) (Hz) = 0.42*Fs*Qts'^-0.96
515-8G specs = 37 Hz/351.6 L /0.27 Qts'
Vb = 93.45 L
Fb = 54.62 Hz
?? woofer specs = 25 Hz/150 L/0.4 Qts'
Vb = 145.85 L
Fb = 36.9 Hz
So in the BW where the 515 dominates, it would be over damped in the big box and woofer under damped in the small box, so what we want at least to the first approximation is the mean between the two, so ATM I'm assuming that averaging these yields the same as my normally averaging driver specs for calculations:
sqrt(93.45*145.85) = 116.75 L
sqrt(54.62*36.9) = 44.89 Hz
Not optimal for either, but one that can be corrected with modest EQ if required, but as you can see, the closer Vas, Qts is or the sums of the two, the better and as for Troels' way, I'll need to read it and driver specs when I'm not so tired, just noticed he apparently did it using impedance curves.
Horns can sometimes complicate 'things', so his designing as a bi-fold with a common 'vent' is obviously a good plan for when some of the drivers can be on the rear.
Note that there's always some series resistance, but using Qts = Qts' for example:
[Qts']: [Qts] + any added series resistance [Rs]: http://www.mh-audio.nl/Calculators/newqts.html
This is how it should be done, only that paragraph caught my attention.
TG's DTQWTII concept isn't "nothing new under the sun" as he puts it, but it does have its benefits and drawbacks. One of the reasons I was excited to go with them was reading that "we have a two way with the addition of a subwoofer". Extraordinary, I thought, but my knowledge at that time did not allow me to understand many things, if it had been so, I would have gone for the simple conical tube, not double. Because the rear speakers of this design must go against the wall at a distance of no more than 20 cm, to "harden or loosen" the compliance "of them and force the low waves to be directed (proportionally) to the center horn .... He also proposed in DTQWTII an addition of plush and " experiment ". I didn't do it, maybe it would have worked....
As in my living room, I can't place them close to the front wall, (as is conventionally recommended with front-radiating speakers only), they are located approx. 1 meter from the side and front walls.
The lower bass was missing, obviously no room boost there. But it makes up for it, no rumbling bass either, and reading through "TG said DTQWTII could do "no problem 40hz".
It's like that, but 40 Hz (and not at 0 DB, I don't even think they would be at F3, but TG graphs always start at 200 Hz, because he considers that by not having an anechoic room, below that frequency all the Measurements will be influenced by the room, which is absolutely true.
But, the 40hz limit (undefined to how many - DB) "doesn't quite reach the frequencies that a "real" subwoofer should cover, so I had to build two of them - the monsters you can see on my avatar , that was fun, really - to "fill" those two octaves that I lacked in the lower zone. Unnecessary for those who can leave the cabinets close and fixed against the wall once they have found the ideal distance, but for me they were necessary - Its construction was very fun and enjoyable - and they fulfill their function very well integrated with the satellites.
I repeat, against the wall, they reach lower and that is how they should be used and were conceived. But you have to think about how they will be located in the room before building something similar. If it happens to you like me, I would not use the rear woofer, I would go for the single horn . Or I would add a speaker designed for a crossover subwoofer further down, but this will depend on whether it complements well with the speaker I see you want to use for the mid/bass area.
Just my two cents, I'll follow the thread carefully. 😉
http://www.troelsgravesen.dk/JA8008_DTQWT.htm
http://www.troelsgravesen.dk/DTQWT-mkIII.htm
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