I've done some work with HornRes, but always with a single driver, and never with a
front chamber. I was curious what an isobaric tapped horn might look like, so I did
a cartoon using:
Two Lab12 drivers, isobarically loaded
5:1 compression ratio
20 liter front chamber
150 liter horn volume
3.5 meter long horn
130 cm^2 throat
970 cm^2 mouth
If someone will run the numbers, I will try to fold a Tapped Horn.
~Don
front chamber. I was curious what an isobaric tapped horn might look like, so I did
a cartoon using:
Two Lab12 drivers, isobarically loaded
5:1 compression ratio
20 liter front chamber
150 liter horn volume
3.5 meter long horn
130 cm^2 throat
970 cm^2 mouth
If someone will run the numbers, I will try to fold a Tapped Horn.
~Don
Attachments
Hi guys,
I'm trying to come to terms with HornResp. I'm simming two drivers wired in parallel but
out of phase. Compared to a single driver, I believe isobaric loading will double Mmd and
Bl, while cutting Cms, Re, Rms, and Le in half. Sd will not change.
Am I missing something?
~Don
I'm trying to come to terms with HornResp. I'm simming two drivers wired in parallel but
out of phase. Compared to a single driver, I believe isobaric loading will double Mmd and
Bl, while cutting Cms, Re, Rms, and Le in half. Sd will not change.
Am I missing something?
~Don
I've been trying to wrap my head around how to do it since you posted the idea.
From the old car-audio design guidelines - the rule of thumb was that isobaric simply cuts the Vas of the driver in half. We know that there is more to it than that.
I think you'd be better modeling it as a single compound driver, but without measuring things, I would only be guessing at what the appropriate parameters would be.
From the old car-audio design guidelines - the rule of thumb was that isobaric simply cuts the Vas of the driver in half. We know that there is more to it than that.
I think you'd be better modeling it as a single compound driver, but without measuring things, I would only be guessing at what the appropriate parameters would be.
the more i fiddle around with FLHs, the more promising i feel they are for live sound apps.
just a heads up for all the thoughts im about to spew, ive been on speakerplans.com alot, drooling over some huge stacks.
ive been looking at the 186 and 1850 horns alot, and while unfortunately theres no distro for PD in north america, its been giving me ideas. ive also been experimenting with non-conically expanding horns, as i find that you can have a larger mouth/length in less space than a conical horn. so ive been using a combination of the first half of the line length being conical, and then rapidly expaning from there. from what i hear mouths that rapidly expand close to the end seem to work better for v coupling (which is also somewhat of a priority.
ive also figured out that alot of the time the excursion at the "knee" in the response at the low end, is much to great for the driver, so in essence you need to make a horn longer than your cutoff/highpass frequency for high SPL applications.
check out this design, it really only works in pairs with EQ or a stack of 4, but a pair of them EQed should do 140db from 40-200ish hz in 2 pi. in a stack of 4 they dont really need EQ(maybe just a tad to bring up the low end). this design will soak up a fair bit more than the 800w RMS of the driver i chose before it starts running into excursion problems, mechanically, things are still safe at around 1200watts!
downsides of this design: its big. like 575 litres big, and needs a mouth area of 7000 cm^2, any smaller and they start to droop off down low. not to mention, unless you can find a wall or a corner, these things are pretty much useless under 60hz in singles. also i dont yet know how im going to manage to fold that much length inside a box of that size, could require some creative folding schemes!
tell me what you guys think, driver and params below.
http://www.parts-express.com/pdf/264-387s.pdf
s1=404
s2=900
con=120
s3=7000
exp= 140
vrc=80
lrc=20
incase anyone is confused, i repeat, the first section is conical, the second one is exponential. and the other catch again is that these dont work well in singles, sim it in 1pi, and count on another ~5db of power handling(because youre doubling drivers+displacement as well by adding the other one(hence why you can EQ the pair of cabs to hit 140from 40hz)
just a heads up for all the thoughts im about to spew, ive been on speakerplans.com alot, drooling over some huge stacks.
ive been looking at the 186 and 1850 horns alot, and while unfortunately theres no distro for PD in north america, its been giving me ideas. ive also been experimenting with non-conically expanding horns, as i find that you can have a larger mouth/length in less space than a conical horn. so ive been using a combination of the first half of the line length being conical, and then rapidly expaning from there. from what i hear mouths that rapidly expand close to the end seem to work better for v coupling (which is also somewhat of a priority.
ive also figured out that alot of the time the excursion at the "knee" in the response at the low end, is much to great for the driver, so in essence you need to make a horn longer than your cutoff/highpass frequency for high SPL applications.
check out this design, it really only works in pairs with EQ or a stack of 4, but a pair of them EQed should do 140db from 40-200ish hz in 2 pi. in a stack of 4 they dont really need EQ(maybe just a tad to bring up the low end). this design will soak up a fair bit more than the 800w RMS of the driver i chose before it starts running into excursion problems, mechanically, things are still safe at around 1200watts!
downsides of this design: its big. like 575 litres big, and needs a mouth area of 7000 cm^2, any smaller and they start to droop off down low. not to mention, unless you can find a wall or a corner, these things are pretty much useless under 60hz in singles. also i dont yet know how im going to manage to fold that much length inside a box of that size, could require some creative folding schemes!
tell me what you guys think, driver and params below.
http://www.parts-express.com/pdf/264-387s.pdf
s1=404
s2=900
con=120
s3=7000
exp= 140
vrc=80
lrc=20
incase anyone is confused, i repeat, the first section is conical, the second one is exponential. and the other catch again is that these dont work well in singles, sim it in 1pi, and count on another ~5db of power handling(because youre doubling drivers+displacement as well by adding the other one(hence why you can EQ the pair of cabs to hit 140from 40hz)
Don Snyder said:
It would be much easier to sim in Akabak. You can assign two woofers to the same entry port and reverse the drive voltage on one woofer.
Rgs, JLH
I'm still trying to figure out why you'd ever want an isobaric driver config TH, when you are talking about PA?
The only place I could figure it would be helpful, is if you run out of pmax, but still have plenty of xmax on a single driver cabinet design. If you have that scenario, THEN, the isobaric allows you 2X motor per sd.
The designs I've looked at / built easily exceed xmax below passband without a steep high pass crossover, and usually come close to tapping out of pmax and xmax at the same time somewhere within the passband.
The only place I could figure it would be helpful, is if you run out of pmax, but still have plenty of xmax on a single driver cabinet design. If you have that scenario, THEN, the isobaric allows you 2X motor per sd.
The designs I've looked at / built easily exceed xmax below passband without a steep high pass crossover, and usually come close to tapping out of pmax and xmax at the same time somewhere within the passband.
The Lab12 drivers have plenty of xmax but will be thermally limited when used in singles. Moreover, they are not mechanically stiff and require a large box volume (this can be seen in Don's TH).
With isobaric loading, that box volume will get smaller, mechanical stiffness increases, max power for the 2 drivers is more than a single. It makes sense, more because it is relatively cheap. But whether it makes "TH sense" is the point?
By all standards, the LabSub and 12Pi remain the best DIY subs in the world; both use the same driver in dual configuration. A properly figured TH should be smaller, work from about mid 30Hz and give both the above mentioned designs a stiff competition, especially given the subjective performance of THs.
With isobaric loading, that box volume will get smaller, mechanical stiffness increases, max power for the 2 drivers is more than a single. It makes sense, more because it is relatively cheap. But whether it makes "TH sense" is the point?
By all standards, the LabSub and 12Pi remain the best DIY subs in the world; both use the same driver in dual configuration. A properly figured TH should be smaller, work from about mid 30Hz and give both the above mentioned designs a stiff competition, especially given the subjective performance of THs.
Right, just input 1/2 Vas and halve or double Re/Le if wired in parallel/series, then (re)calc Mmd, Bl, Rms.
Hmm, a 5:1 CR would make S1 = 506.7/5 = 101.34 cm^2 and HR calcs a ~169.5 L horn net Vb and that's with a slightly smaller expansion due apparently to its rounding off of Fta, so adding a 20 L Vtc makes it 190+L net.
Judging by the sim though, I imagine you'll be looking for a different design. Anyway, assuming a ~12.5" i.d. width to find S1's acoustic center and assuming a ~6.25" L34, parallel wired VC's/1 W@3 ohms:
GM
Hmm, a 5:1 CR would make S1 = 506.7/5 = 101.34 cm^2 and HR calcs a ~169.5 L horn net Vb and that's with a slightly smaller expansion due apparently to its rounding off of Fta, so adding a 20 L Vtc makes it 190+L net.
Judging by the sim though, I imagine you'll be looking for a different design. Anyway, assuming a ~12.5" i.d. width to find S1's acoustic center and assuming a ~6.25" L34, parallel wired VC's/1 W@3 ohms:
GM
Attachments
jbell said:
Reducing bulk. For a given alignment/peak SPL it halves net horn Vb and increases linear output down low at the expense of 2x the number of drivers and amp power. Considering the driver assortment available for most folks though, it doesn't seem worth it except where driver selection is limited, especially if they are high Vas and or high Qts units.
GM
To model more than 1 driver in Hornresp, just use the "Driver Arrangement" window in the tools menu. I guess this assumes the drivers are wires in phase tho, I think Akabak would have to be used if they are not in phase...
EDIT: Ignore this, I just realised the driver arrangement thing won't help for isobaric as it assumes the drivers are mounted normally...
Brain not engaged before posting it seems! 😱
EDIT: Ignore this, I just realised the driver arrangement thing won't help for isobaric as it assumes the drivers are mounted normally...
Brain not engaged before posting it seems! 😱
I didn't in the end, I've been pretty busy recently plus also I'm a little short of space... I must admit as I mainly use mine for music I'm tempted to make a smaller box tunes to 40Hz instead of 30. 🙂Don Snyder said:
That said, the non folded version is performing wonderfully, I recently picked up a Citronic PPX2400 amp and gave it a whirl with the TH today and it felt like the whole house was shaking...
I've got another 4012HO in a midbass horn, going from 100Hz-1Khz, and it seems to work well with the TH. I just need to get something a little better than old midi hifi speakers for 1KHz+. Piccy:
An externally hosted image should be here but it was not working when we last tested it.
GM said:
Exactly. That's my point.
In PA, coming up with a solution that requires double power/double drivers, that 'may' get you a slightly smaller cabinet, is going in the exact opposite direction of where you want to go. Also, in my playing around with an isobaric lab12 for TH.. I just couldn't get anything really workable for PA. (starting from GM's hornresp params)
If it can't do (in my opinion) 100db efficiency from 40-100, it can't play in the PA sandbox, single driver or dual in isobaric config. And size... well it's usually defined by what fits in the truck or trailer, so 'reducing bulk' is a relative term. (and may actually be measured in comparison to the Labsub at over 700liters.)
Now, if your goal is small... this doesn't make 100db, however it's only 153 liters. Which for reference is the exact same size as eminence suggested 1x15 ported cabinet for a 3015lf, and it makes roughly the same noise. The advantage is it's a FLH, vs a direct radiator. I'd much rather have a pair of these, vs an isobaric lab12 TH in the 300liter range, from what hornresp tells me. Also for comparison, 4 of these are smaller than a labsub, and louder from 40-100hz. (which makes perfect sense with 4 drivers)
Regardless, my 2c is I have yet to see an isobaric config (TH or not) that makes sense for PA. AND.. (this is a really important and...) If it was a great idea, and provided great benefit.. Tom would have probably already done it.
I don't mean to discourage anyone looking for an isobaric TH solution for PA, so... go.. design.. and post your results
Attachments
2.83v on 3ohm, which is 2 3/4 watt?
I guess I should have been more specific... How about 100db efficiency from 40-100hz, at either 1W/1M, or 2.83v@8ohm.
I guess I should have been more specific... How about 100db efficiency from 40-100hz, at either 1W/1M, or 2.83v@8ohm.
~2.67 W....... I just chose 2.83 V since it's the default sensitivity reference. At 1 W/1.73 V/3 ohm, it takes ~572.3 L net horn Vb.
GM
GM
GM said:
jbell said:
The above 2 conclusions nail it..... Lab12 driver, single or isobaric, in a TH is not for PA.
Thanks everyone who being proficient in HR, participated and arrived at exactly the same conclusion, helping me shelve an idea that's been around for some time now.
Keeping with the title, this thread must still go on!!!
