| Open baffle With cheap, large, low Fs car drivers - Click HERE for Original Thread |
| bigwill |
I've had my eye on these woofers:
http://www.monacor.de/int/en/produk...typ=full&spr=EN
They seem to be quite suitable for open baffle operation, and you can get them for £35 each from CPC. They have a large surface area, low Fs and high-ish Qts. I'm a bit dubious about their x-max though, but they're not exactly PA drivers so they be alright. I'm thinking about buying four of them (two per side) and wiring them in SERIES to make a more benign 8 ohm load. Hopefully, this will raise their Qts value to something a bit more usable in an open baffle. Any reason why this wouldn't work? |
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| Volenti |
Going by the published specs they look allright, Le is nice and low, x-max probably isn't going to be all that much (as hinted at by the specs) but they seem to be efficient so you won't need much power.
I'd say their worth a shot. |
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| bigwill |
Hmm, if I bought just one as a test, would I be able to determine how suitable it was? I could buy a powerful resistor to raise the Qts to around the 0.7-1.1 range and put it on a baffle (I have quite a big peice of MDF I could use)
Could be fun |
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| hitsware |
putting them in series won't raise Qts
it'll still be the same |
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| bigwill |
| quote: | Originally posted by hitsware
putting them in series won't raise Qts
it'll still be the same |
Are you sure? How can the driver have the same electrical damping with another driver in series? |
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| hitsware |
| Re doubles, but so does Zmax so the result is the same as a single driver. Inverse is true when you parallel drivers. |
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| bigwill |
| Hmm, I see. I wonder what size resistor I would need in series with one of them to raise the Qts to 0.71, hopefully nothing too big. |
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| DoomPixie |
i actually have a couple of those EXACT drivers! they came in my first ever speakers i bought, they are in 3 way speakers with a 6" mid and a 4"tweeter but none of the drivers are original, someone just put them in the goodmans boxes..lol.. they actually sound pretty good, its the midrange and tweeters that let those speakers i have down not the subs, mabey if i wasnt moveing away over summer i would have been persuaded to rip the subs out and try them open baffle for you and let you know how i get on but at the moment it isnt going to happen, i have had them out and had them in ported boxes and they sounded pretty good in the ported boxes.. also had them in sealed boxes and they sounded pretty good but i have never tried open baffle before with any driers so i cant really comment on how they would respond.. they do seem to be quite cheaply made BUT they also seem to be very robust and have stood up to many a thrashing at parties at my place so they pass all my tests as far as good value.. hope this helps some..
Owen |
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| richie00boy |
Monacor have obviously fairly recently changed the design of that driver. Me and Nuuk were looking at getting them about a year or so ago, back then Qts was about 1.2 IIRC. So it would be worth checking that CPC stock the more recent version.
As for how to calculate the new Qts when inserting series resistance, here is a formula that should be what you want:
R = [(Qts_required / Qts) * Re] - Re |
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| bigwill |
| quote: | Originally posted by DoomPixie
i actually have a couple of those EXACT drivers! they came in my first ever speakers i bought, they are in 3 way speakers with a 6" mid and a 4"tweeter but none of the drivers are original, someone just put them in the goodmans boxes..lol.. they actually sound pretty good, its the midrange and tweeters that let those speakers i have down not the subs, mabey if i wasnt moveing away over summer i would have been persuaded to rip the subs out and try them open baffle for you and let you know how i get on but at the moment it isnt going to happen, i have had them out and had them in ported boxes and they sounded pretty good in the ported boxes.. also had them in sealed boxes and they sounded pretty good but i have never tried open baffle before with any driers so i cant really comment on how they would respond.. they do seem to be quite cheaply made BUT they also seem to be very robust and have stood up to many a thrashing at parties at my place so they pass all my tests as far as good value.. hope this helps some..
Owen |
Thanks for commenting :)
The drivers sound promising, and I don't intend to thrash them at parties so they should easily cope with the relatively low SPLs I listen at :)
In the boxes you had them in - were they boomy? I expect they were because of the high Qts values, but if not, even better! I can then use them in sealed cabinets if this goes wrong (or sell them) |
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| bigwill |
| quote: | Originally posted by richie00boy
Monacor have obviously fairly recently changed the design of that driver. Me and Nuuk were looking at getting them about a year or so ago, back then Qts was about 1.2 IIRC. So it would be worth checking that CPC stock the more recent version.
As for how to calculate the new Qts when inserting series resistance, here is a formula that should be what you want:
R = [(Qts_required / Qts) * Re] - Re |
Yes, I will make sure they do. The old version's Qts is too high to be useful for anything IMO.
Hopefully they do stock them. |
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| DoomPixie |
| they wern't too bad, they sounded best by far in the sealed enclosure as opposed to the ported or the three way speakers (Also ported) they really dont need much power behind them either. i have no idea which version i have though if there are really two versions... but i suspect they are the old ones as i have had them for about 2 years now.. mabey even longer :eek: |
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| richie00boy |
| Don't forget you can always Linkwitz Transform them in a sealed box if the Qts is too high. |
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| bigwill |
| quote: | Originally posted by richie00boy
Don't forget you can always Linkwitz Transform them in a sealed box if the Qts is too high. |
Hmm, that's true. I think two in a big box with a transform could be pretty impressive :smash: |
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| bobo1on1 |
| quote: | Originally posted by hitsware
putting them in series won't raise Qts
it'll still be the same |
I don't think it's that simple, the frequency response in open baffle is the same, but resonances are less dampened, I think it's sort of like using a series resistor and an equalizer. |
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| richie00boy |
| No he's right, it's as he said. DCR doubles but so does Zmax, i.e. the impedance curve is exactly the same shape as with a single driver, just the scale is doubled. As Q is derived from the -3dB points either side of the Zmax peak, ergo Q must be the same as a single driver. |
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| bigwill |
| Actually, the fact that the Q stays the same is a good thing, because I can then easily build a gainclone that will drive 8 ohm loads but not 4 ohms with mixed mode feedback to have an output impendance of an exact value I need to raise the Qts (around 2 ohms) so no power will be lost in series resistors.. |
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| bigwill |
| The drivers I'm looking at have an air gap height of 6mm, does this translate into an X-Max of about 4mm, and if so, is this enough when you have four of the drivers? |
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| Volenti |
| quote: | Originally posted by bigwill
The drivers I'm looking at have an air gap height of 6mm, does this translate into an X-Max of about 4mm, and if so, is this enough when you have four of the drivers? |
Can't calculate x-max from that without knowing the height of the voice coil windings, but judging from the inductance and other specs I would say it's likley the x-max would be in the 4-6mm range. |
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| micb |
Low xmax drivers like 6mm are not often suited to LT.
If that driver is anything like the old Carpowers freeair/IB drivers from late 90's then they are most likely not worth the time. |
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| bigwill |
I wanted to use them OB
The choise of drivers in the UK is RUBBISH :mad: |
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| micb |
| quote: | Originally posted by bigwill
I wanted to use them OB
The choise of drivers in the UK is RUBBISH :mad: |
Yep.
Peerless XLS 10's from BKelec are just about the best bet for drivers. A pair in 2 cubes net with a couple of passive radaitors with and some adeed extra mass to ther PR for a low tune will be good though. |
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| richie00boy |
The drivers are cheap and probably not great, but for their price it's worth trying? Xmax may not be huge, but with 15 inch cones a fair amount of air will be moved.
Providing you don't want anechoic response to 20Hz you could LT those drivers fine I think. |
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| micb |
Personaly I think it will be a waste of time that is a driver suited to a very large IB application in a car boot (8-10 cubic foot) putting it in a small box and adding LT/EQ to alter the response is pretty much the opperste to what it was designed for......
They say they have altered the prams since the model I used that back in 98, still I can't imagine it would be that good, we got some output from them but found hard to get much good extention from it.
In the end its your choice you could give it a go or save the cash for a different project.
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| bigwill |
| I think I'll wait until I can find a better woofer now. Speakers are currently the least of my worries :( |
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