I am looking for some smaller drivers, 8" or less that are both shielded and have an impedence of 16 ohms or greater. Does anyone know of such drivers. They could actually be large if someone knows of something that fits the bill but usually the larger drivers are not video shielded.
Add a resistor to get your impedance up. If you are building a center channel get a quarter inch steel plate and it will be shielded fine. I have at least 20 lbs of alnico under my tv and with 1' of space and thin sheet of aluminum get no problems with the picture at all.
Alnico magnets are inherently self shielding, and so have much lower stray fields. Ceramic and neodymium mags are not. Some of my compression drivers will distort my TV from a couple of feet away, yet my alnico Tannoys don't.
Adding a series resistor will reduce the level to the driver, and probably change the tuning of any crossovers and low frequency tuning unless compensated for.
Adding a series resistor will reduce the level to the driver, and probably change the tuning of any crossovers and low frequency tuning unless compensated for.
Double M Cups
Pat O'brien
http://www.warco.com.au/awar.htm
used to stock a range of sizes of heavy guage steel, powder coated metal "cup" to fit over the back of, and enclose the magnet assembly for the pupose of magnetic shielding.
I am not sure if he still stocks them, but you've got the link above.
Also take a look at the drivers in typical modern AV systems and televisions - They typically use the cheapest cup shaped pressing you can find.
Others have an additional ferrite ring glued to the back of the magnet assembly.
It should not be too difficult to cook up something suitable.
Regards, Eric.
Pat O'brien
http://www.warco.com.au/awar.htm
used to stock a range of sizes of heavy guage steel, powder coated metal "cup" to fit over the back of, and enclose the magnet assembly for the pupose of magnetic shielding.
I am not sure if he still stocks them, but you've got the link above.
Also take a look at the drivers in typical modern AV systems and televisions - They typically use the cheapest cup shaped pressing you can find.
Others have an additional ferrite ring glued to the back of the magnet assembly.
It should not be too difficult to cook up something suitable.
Regards, Eric.
I would not because adding a resistor increase the Qes of the speaker driver and it decreases the SPL too.
markkanof, your best bet is to find dual voice woofers and hook their coils in series. This will not change the Qes too much because the wire used is a bigger diameter or lower gauge value. Next find a magnet called a bucking magnet. You can find bucking magnets at Parts Express, Madisound, etc. After you mount (on the back plating) the bucking magnet to the woofer, I suggest you measure the woofer.
Perhaps a little out in left field for your ap but i'm on a push-push kick right now.
If you take two drivers and mount them magnet to magnet you get a push-push bi-polar driver that is pretty well shielded. Wire a pr of 8s in series and you have 16 ohms. I took a pr of RS 40-1197s and i could get them within a couple inches of the monitor before it started going blooey. With one driver by itself maybe 18".
As mentioned earlier alnicos are inherently shielded. Your best source for these are the 2nd hand stores (either directly or from those of us scouring those stores for you and flogging them on eBay.
dave
If you take two drivers and mount them magnet to magnet you get a push-push bi-polar driver that is pretty well shielded. Wire a pr of 8s in series and you have 16 ohms. I took a pr of RS 40-1197s and i could get them within a couple inches of the monitor before it started going blooey. With one driver by itself maybe 18".
As mentioned earlier alnicos are inherently shielded. Your best source for these are the 2nd hand stores (either directly or from those of us scouring those stores for you and flogging them on eBay.
dave
Hi !
Based on your description, you should look at GR-Research. The GR-165 is a 16 ohms, 6.5" and it's shielded. That's what's inside their A/V 3 kit which is a MTM with a series XO. It has good sonic reputation. You can buy the drivers separately and the price is good. They don't sell bigger driver though. They're being made by Peerless-India to their specifications.
http://www.gr-research.com/drivers.html#gr165
Good Luck
Based on your description, you should look at GR-Research. The GR-165 is a 16 ohms, 6.5" and it's shielded. That's what's inside their A/V 3 kit which is a MTM with a series XO. It has good sonic reputation. You can buy the drivers separately and the price is good. They don't sell bigger driver though. They're being made by Peerless-India to their specifications.
http://www.gr-research.com/drivers.html#gr165
Good Luck
Mark--- Get some old EV SP8s. 16 ohms, Alnico magnets. On ebay all the time. Also Altec-WE 755s, I think the 755 used Alnico. JBL might have made some Alnico, 16 ohm 8s, try Jammin Jersey at www.jamminjersey.com
If I may I offer my $.02 worth:
Try to stay away from cheap drivers. Vifa makes a superb 5.25" mid/woofer in 16ohms(their model#M13SG09-16). This is an excellent match for most high quality tweeters and large woofers/subs. Best of luck in your endeavors -Lee
Try to stay away from cheap drivers. Vifa makes a superb 5.25" mid/woofer in 16ohms(their model#M13SG09-16). This is an excellent match for most high quality tweeters and large woofers/subs. Best of luck in your endeavors -Lee
"adding a resistor increase the Qes of the speaker driver and it decreases the SPL to
Using Qes to tune Qts.
An observation using Unibox Software
A change in the voice coil Re does not effect Qts yet really drops Spl
If I raise Qes (driver Re at Fs) the Qts goes up to a very nice .38
and SPL drops by 1 db, mostly in the midrange leaving the bass intact.
Is the driver Re linked to Voice coil Re and Qms
Just changing the Qes is an ideal situation for this Eminence Pro driver. Can I do this ??
Power Applied 50W
Fs 38.2
Re 5.0 Ohm
Qms 7.73
Qes 0.32
Sd 858.0
Vas299.0L
Xmax 5.5mm
SPL at 1 W 1 m 99.1 db
SPL at 2.83 Vrms 1m 101.1 db
Qts 0.307
Effective Qts 0.307
Mms 60.03g
Cms 0.289mm/N
Rms 1.864 Kg/s
Bl 15.00Tm
Ref efficiency, n 5.007%
Applied voltage 15.81 Vrms
========================
Now with a change to Qes of .40
SPL at 1 W 1 m 98.1 db
SPL at 2.83 Vrms 1m 100.2 db
Qts 0.38
Effective Qts 0.38
Mms 60.03g
Cms 0.289mm/N
Rms 1.864 Kg/s
Bl 13.42Tm
Ref efficiency, n 4.006%
Applied voltage 15.81 Vrms
I can post a jpg of Parameters or SPL plot, just ask TIA
Using Qes to tune Qts.
An observation using Unibox Software
A change in the voice coil Re does not effect Qts yet really drops Spl
If I raise Qes (driver Re at Fs) the Qts goes up to a very nice .38
and SPL drops by 1 db, mostly in the midrange leaving the bass intact.
Is the driver Re linked to Voice coil Re and Qms
Just changing the Qes is an ideal situation for this Eminence Pro driver. Can I do this ??
Power Applied 50W
Fs 38.2
Re 5.0 Ohm
Qms 7.73
Qes 0.32
Sd 858.0
Vas299.0L
Xmax 5.5mm
SPL at 1 W 1 m 99.1 db
SPL at 2.83 Vrms 1m 101.1 db
Qts 0.307
Effective Qts 0.307
Mms 60.03g
Cms 0.289mm/N
Rms 1.864 Kg/s
Bl 15.00Tm
Ref efficiency, n 5.007%
Applied voltage 15.81 Vrms
========================
Now with a change to Qes of .40
SPL at 1 W 1 m 98.1 db
SPL at 2.83 Vrms 1m 100.2 db
Qts 0.38
Effective Qts 0.38
Mms 60.03g
Cms 0.289mm/N
Rms 1.864 Kg/s
Bl 13.42Tm
Ref efficiency, n 4.006%
Applied voltage 15.81 Vrms
I can post a jpg of Parameters or SPL plot, just ask TIA
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