good thinking, out of the box
Great comment! It really works - the magnets on mine never became warm to the touch flat out for a couple hours at a gig. No doubt the coils were a little warmer though!
Some car audio boys do it for show, but it will help reduce power compression in the long term.
you need stiff diahpragms for good transient response
If you want good transient response it is important to know:
- you need a bass driver with a stiff cone - perhaps with kevlar reinforcement if you can find that
- low rms sounds more lively, so capton voice coils are better than aluminium voice coils
- you need a good enclosure which is stable - better use two smaller drivers with the drivers facing each other - like Linkwitz demonstrated in some projects - with one driver turned in phase and direction you get less distortion K2
you can see a good sounding subwoofer using the Linkwitz method here
Just wanted to show off my new 18in build
If you want good transient response it is important to know:
- you need a bass driver with a stiff cone - perhaps with kevlar reinforcement if you can find that
- low rms sounds more lively, so capton voice coils are better than aluminium voice coils
- you need a good enclosure which is stable - better use two smaller drivers with the drivers facing each other - like Linkwitz demonstrated in some projects - with one driver turned in phase and direction you get less distortion K2
you can see a good sounding subwoofer using the Linkwitz method here
Just wanted to show off my new 18in build
The Lavoce shift a lot of air so not sure it's suitable to reverse the driver. Running in free air its like a fan.
So my understanding is that the extra power to overcome the box spring, combined with the smaller air volume to heat up is the concern.
How is this overcome in retail subs? Say the JL Fathom with 3kw in 60litres.
The testing I reference for this sub is Ricci on DB which has this sub in about 120l and puts long-term outputs sweeps up to 145v through it so if I could have made more room for the enclosure i really wouldn't worry. Does 40 liters of sealed air space dissipate that much more heat?
So my understanding is that the extra power to overcome the box spring, combined with the smaller air volume to heat up is the concern.
How is this overcome in retail subs? Say the JL Fathom with 3kw in 60litres.
The testing I reference for this sub is Ricci on DB which has this sub in about 120l and puts long-term outputs sweeps up to 145v through it so if I could have made more room for the enclosure i really wouldn't worry. Does 40 liters of sealed air space dissipate that much more heat?
^ and be heck of a louder at the low frequencies. The heat must go up in too small cabinet because there needs to be EQ to boost the low end response (relative to higher frequencies). More power must go in for same SPL at same low frequency than with more optimal cabinet that doesn't require EQ = more heat for same SPL. 6dB boost requires 4 x power, it could be 3kW vs. 750W.
ps. it is rare to find products whose numbers are not exaggerated by the marketing team.
ps. it is rare to find products whose numbers are not exaggerated by the marketing team.
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Yes it would be more efficient, in 300l down at 20hz (+4db). It would be 100% more excursion at that point and running at its full rate xmax.
I am trying to figure out whether we are talking about real-world audible differences or mechanical theory by which every design has flaws. If we don't have some practicality applied every sealed design would be ib.
Unless winisd is very wrong (which I suspect it may be but I don't know by how much) then the lavoce is hitting 104db at 20hz (50% of xmax) and a pretty straight line up to 100hz at 125db.
So maybe a better way to approach it is to ask the question what driver is going to outperform it in the same cabinet and the same amp which are set limitations.
I am trying to figure out whether we are talking about real-world audible differences or mechanical theory by which every design has flaws. If we don't have some practicality applied every sealed design would be ib.
Unless winisd is very wrong (which I suspect it may be but I don't know by how much) then the lavoce is hitting 104db at 20hz (50% of xmax) and a pretty straight line up to 100hz at 125db.
So maybe a better way to approach it is to ask the question what driver is going to outperform it in the same cabinet and the same amp which are set limitations.
I am most interested in this idea @Hydrogen Alex
The PD2150 is no longer produced. Could you recommend an alternative driver?
Thanks
DM
Those Precision Devices drivers are so pretty they deserve glass enclosures. And they do one thing really really well: blow off heat from the voice coil. Is that an important goal?
Generations of posters to DIYaudio have assumed that power handling and hot-copper voice coil cooling ("power compression") are primary goals instead of selecting woofer drivers (maybe all drivers) for lowest possible resonance, low distortion, low-mass moving assemblies, and magnet smarts.
The reason is a badly estimated need for Power. And a confusion between instantaneous peak power capability (to avoid clipping on audible milisecond peaks) versus long-term power handling as in a dance venue. It may be that some settings really do need the long-term resistance to power compression and incendiary experiences. But for quality audio on quality recordings of music instruments your grandmother would recognize, not so.
My impression is that almost any driver labeled "Pro" sacrifices audiophile priorities in order to emphasize disco priorities.
Ben
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If you have the power available to drive them.
These will demolish a PD for sub use, no reason to go ported either.
A lightweight, untreated paper cone for 20hz, is rarely a benefit.
Almost 40 mm of excursion with a linear BL curve.
Good inductance control, linear Le /excursion and suspension linearity.
Low impedance, efficiency, price and weight is the downsides.
https://stereointegrity.com/product/hst-18-mkiii/
https://stereointegrity.com/product/hs-24/
https://stereointegrity.com/product/hst-18-mkiii/ Arez, these are for automotive use ie a small box for the driver inside a small box (car HGV cabin).
Have you bought a pair of these? In my opinion, they will be horrific for domestic audio use.
The first red flag is :
(1) Mms 567.8g (!!!) with just 16.6 Bl ....WOW! That is the worst ratio ie Weakest motor I have ever seen on any 18 inch driver.
Have you bought a pair of these? In my opinion, they will be horrific for domestic audio use.
The first red flag is :
(1) Mms 567.8g (!!!) with just 16.6 Bl ....WOW! That is the worst ratio ie Weakest motor I have ever seen on any 18 inch driver.
Hydrogen Alex, did you look at the HST MKIII Re? Bl^2/Re is the normalized motor force, taking Re into consideration. Horrific for domestic audio use? I'd say bollocks. Will it have the upper bass slam of a B&C or BMS driver, nope. It will shake your cupboards with 10 hz or lower tones, modulate doors in jambs, break light fixtures, or otherwise damage your home.
Yeah, seems counterintuitive to some, but the lower one goes and the narrower it's BW, the less effective motor strength required:
T/S theory: The box only loads the driver to its upper mass corner (Fhm):
Fhm = 2*Fs/Qts'
Qts': 2*Fs/Fhm
Fs: Fhm*Qts'/2
On a related, but even more counterintuitive subject to some, woofer 'speed'
(Qts'): (Qts) + any added series resistance (Rs): http://www.mh-audio.nl/Calculators/newqts.html
T/S theory: The box only loads the driver to its upper mass corner (Fhm):
Fhm = 2*Fs/Qts'
Qts': 2*Fs/Fhm
Fs: Fhm*Qts'/2
On a related, but even more counterintuitive subject to some, woofer 'speed'
(Qts'): (Qts) + any added series resistance (Rs): http://www.mh-audio.nl/Calculators/newqts.html
The only thing i can say is poor cars
These are not specifically for auto use, but yes the efficiency is on the low side, a lot of the mms comes from the massive vc assy.
They're HT, IB and HST is not aimed at the auto industry.
If anything a rarity, HT subwoofers for ELF use, 5-100hz is it's intended operating range
Made to fit in boxes that can be put into a actual home 5-15 cu. sealed.
Ending up with a F10 in the 17-20 hz region, without room gain or eq.
Also notice they use a foam suspension, not a rubber halfroll.
Although the 24" would be my preference if i had the space, and the ops goal, it has a better balance of param,.
The original, OP wanted a sealed cabinet eqd to -3db @ 10hz.
Not counting room gain.
You need loads of excursion/cone area., if you want high spls.
And these ones does that fairly well, they will manage 100db at 10hz@1m with a 18" ish cone in a sealed box, witout eq.
And why is that>?
What would be better and why.
First off as @diyuser2010 pointed out:
Bl^2/Re is the normalized motor force, taking Re into consideration.
Notice it's listed with a RE of 1,5.. so not a series connected d2 as the 24 example of TS.
And weakest motor in what way ?
It has 3x stacked Ferrite Y35 magnets, each one is thicker then the 2150's 1 FE magnet, that's a deep magnet gap.
The magnetic strength of it is quite impressive.
Remember BL is a stationary measure, at BL X=0.
Meaning it is a measure of the magnetic field-strength (in Gauss usually), at the resting position in the center of the gap.
Times the length of wire in the gap.
For example the 3 demodulation rings,the inner 'demodulation sleeve, and there is 8 layers of coil in the gap with alu. forrner for heat transfer and inductance control, that also makes it a wider gap.
There will also be some clearance especially with such high excursion drivers.
Now go and look at the Klippel testing of them and compare it to well anything you find, pretty much.
The PD.2150, while it has a BL of 34 it has a listed Xmax of 10mm.
Usually meaning that BL has reached 70%, some use 80%,some use other estimates.
So at 10mm X you have lost 30% of the drivers BL.
The motor strength varying betwen 34 at the center and 23 BL at the outwards positions, with a 20mm total travel,
You get high amounts of distortion, and this is a simple mathematical exercise, does not take suspension travel and nonlinearity into account.
It also does not account for the change in impedance or inductance modulation with excursion and heat.
The HST 18 at 20mm one way travel still has around 16 BL, with a completely linear suspension.
40mm of total travel with BL varying with only s few %.
The inductance over excursion is well controlled.
And the foam surround is again incredibly linear and well behaved over the entire range.
Another point about "speed" that many people forget is that the crossover that is applied to the driver is also limiting its bandwidth, which it turn reduces the "speed" at which it can response to a simulus, and introduces delay. Of course this is all standard stuff, but those people who seem obsessed with low Mms high BL low Qts driver often totally miss this point.
https://sound-au.com/project48.htm This link is to Rod Eliot who is a true legend.... He explains the ELF principals and why Pro drivers are best suited to the task. The 500g Mms coned brigade are not capable of making music, but they can "shake your cupboards" if thats your thing...
.Edit - I have attached a bunch of Beyma and PD driver sims, all ELF principal ie small sealed box with Eq and powerful amplifiers.
Also here is the new Presion Devices 21 inch driver...file:///C:/Users/emiii/OneDrive/Desktop/Audio%20and%20Adobe/PD-2155-21%20inch%20with%205.5%20inch%20VC.pdf It is a true work of art with a 5.5 inch voice coil it is rated at a genuine 1,500 watts continuous AES with, 6,000 watt peaks! But in real world domestic use it will sing with 100 to 500 watts of high quality power amplifier in an ELF design.
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Introducing Thermal Distortion by Ing. Michael Gerstgrasser
This is a superb paper by a DIY legend... Thermal Distortion is usually and incorrectly called "Power Compression" and this paper explains why large voice coils
(like Precision Devices) deliver such dynamic low distortion sound compared to the cheap small voice coil / huge Xmax /rubber surround automotive / HT type drivers.
This is a superb paper by a DIY legend... Thermal Distortion is usually and incorrectly called "Power Compression" and this paper explains why large voice coils
(like Precision Devices) deliver such dynamic low distortion sound compared to the cheap small voice coil / huge Xmax /rubber surround automotive / HT type drivers.
Sorry, I posted the wrong link above. https://www.precision-devices.com/w...D-2155-1F-Technical-Specifications-051022.pdf