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i read in the 515g in a tuba 36 thread, old guy mentioned that horn loading changes the impedance of the driver. is this true and is there a formula for this? a 16 ohm driver in an 828 cab yields? the reason i bring this up is that ive 16 ohm drivers and 8 ohm crossovers
By using an 8ohm XO with 16 ohms drivers the XO point would change. But it is not that critical since the impedance changes with frequency response anyway.
But there are certain basic rules to follow to build XO and that is the Drivers impedance and the
Xo point.
So my 02. cents advice would be to change the
Capacitors value and inductors value inside your N
crossover.
.........
<font color="#FFFFFF" size="1">[ November 10, 2007 01:46 PM: Message edited by: CONVERGENCE ]</font>
A box of almost any type, and it's tuning will affect the impedence an amplifier "sees" vs. any given driver's parameters as measured in free air, horn boxes in particular have a major effect on impedance.
Here's a long but very explanatory text on impedance from Peavey.
http://www.peavey.com/support/techno.../impedance.cfm
EDIT: For 99 bucks the Dayton WT3 woofer tester is a very handy tool. One of the things it can do is give you a very accurate impedence plot of your assembled speaker system as well as it's individual drivers.
It's the cheapest interface and software i know of that can show you graphic representation of the effect that box volume and tuning can have on the impedence of a driver. It's main purpose is to measure the T/S parameters of any woofer/driver.
<font color="#FFFFFF" size="1">[ November 10, 2007 03:05 PM: Message edited by: bowtie427ss ]</font>
hey bowtie..as per your suggestion awhile back, i got the woofer tester. i cant for the life of me, figure it out. i wrote back to the folks there at smith and larson. from what i gathered , perhaps i fried the tester, and thus have no way to calibrate the unit. when i ran initial tests, it would just run, i let it go all night and still no results. ill have more free time this winter for my projects, thats one of them
Valhallax, is this the "woofer tester 2" you're having problems with?
I used a friend's for a while, and of course missed it terribly when he took it back home. I tried to get WT2 for over 6 months, then PE finally told me it was discontinued and they'd be offering a similar product very soon. I'm wondering if the WT2 wasn't problematic or had conflicts in a large number of PC's.
Received an email from them several weeks back telling me that the new Dayton WT3 was now available in limited quantity. I placed an order only to be informed it was out of stock, but received correspondance just a few days later saying it was shipping that day.
WT3 is very much plug and play right outta the box, i'm running it on an XP system and it took less than 3 minutes to install the software and calibrate the interface, which is just a simple USB dongle with a pair of alligator test leads exiting the tiny "magic box".
This version seems to run very smooth, does it's sweep in just a few milliseconds and the numbers all pop up on the screen a few seconds later.
Calculating Vas takes some additional work and three methods are available, one is thru the use of a "test box", another thru the use of "added mass", you guessed it, a known mass firmly coupled to the cone, or "SPL method" where you need to know the driver's 1w/1m sensitivity.
Now if only they could have taken it one step further and included an RTA and test mic input on the interface.
indeed, it is the wt2, they have gotten back to me and stated there will be a new software driver update soon.
I think if you sim the horn you can figure the impedance increase, but don't quote me on that.
It's gonna vary by cab, an A-7 probably is less than an ohm. A Tuba 36 with the drivers I used was about 11 ohms. 3 in parallel is 3.66 ohms, which is close enough to 4 on my amps.
An upward mismatch is better for a crossover than a downward one. Proper crossover design takes into account the box.
<font size="2" face="Verdana, Helvetica, sans-serif">16 ohms nominally;Quote:
Originally posted by valhallax:
... a 16 ohm driver in an 828 cab yields?
http://www.lansingheritage.org/image...515g/page3.jpg
In this case, the horn BW is in the driver's ~flat impedance range, so the rear loading of the driver has more effect on the impedance than the horn,
If I understand you correctly though, you're hoping the cab would make your 16 ohm drivers look like 8s to your XOs? If that's the case, no such luck amigo, you needs the right pieces...
<font color="#FFFFFF" size="1">[ November 11, 2007 11:07 AM: Message edited by: bfish ]</font>
Wouldn't the OP's particular situation be an ideal app for the 15067 matching transformer?
You still haven't sold those things yet? http://www.hostboard.com/forums/