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In Reply to: RE: Drivers for existing cabinet posted by Bill the K on May 01, 2024 at 09:27:07
The low end "knee" or corner is tied to the sensitivity and interior cabinet volume. So the LF -3 point, box volume and 1w sensitivity are tied together by the wall of science aka Hoffman's iron law, not a suggestion haha.
While your HF response may be rolled off, you have also adjusted to that and will notice if what was is no longer. But a woofer that gives you lower bass also doesn't go up high and a 6.5 inch driver is too large to go up all the way without a wacky radiation pattern.
Before you decide what to do, consider dipping a toe in the speaker building water.
Take one of your speakers your considering working on and put it on the table or living room floor and look at the woofer.
Examine the mounting screws and carefully remove them. They might be wood screws -or- machine screws with fine thread and a"T-nut" or threaded insert in the wood.
The woofer may well be kind of stuck to the baffle board, good speakers have a back gasket to seal that connection. If the woofer seems stuck, get a couple small blocks and position the speaker front down raised at the corners by the blocks. Usually gravity will free the driver after a little while.
If not, use a small wood block on the baffle to protect it and use a flat blade screw driver to pry up the edge of the driver, you may have to pry up in several places if it's really stuck (there was a speaker in the old days that actually caulked the drivers in).
IF your cabinet happened to have a port in the right place on the back, if you can push on the magnet with a stick that can pop one out too.
With the driver out, you have "it" in your hands and now you can look at your mounting hole diameter and bolt circle for if/when you look at drivers. Hopefully the driver has push terminals or push on removable connection but note which wire went where.
Hope that helps
Tom
About how far is the closest edge of the lf cone to the center of the tweeter?
Follow Ups:
The distance between the edge and the centre of tweeter is 1.75 inch
Bill
Hi
Ok that small space means that your choice of crossover points is pretty wide open.
OTH, your thought about using a full range driver also has merit.
About 15 years ago at work i designed a small "fill" speaker that used a Fostex 126 full range driver with two small woofers.
Yesterday i had to see how the new version of the Fostex 126nv2 measured in that same cabinet.
There is a property the late Dick Heyser measured called Energy/Time Curve or Envelope which shows how fast the sound stops radiating from the driver after the signal ends.
The 126 has an unusually good ETC, at 10 inches distance the energy from the driver fell more than 50dB in just a few ms (50dB = 100,000:1 energy ratio) .
That is a very good sign as the biggest issue loudspeakers usually have is all the sound they produce and arrives that isn't directly tied to the input signal. That's the stuff that lets your ears triangulate on the speaker distance AND disrupts the acceptance as real of the illusion in the recording
This driver is large compared to 20KHz (wl about 5/8 inch) and I have not measured the polar pattern (it will have significant directivity up high) but on and near on axis, on a nice baffle (that doesn't cause re-radiations) that driver should provide an excellent stereo image. Like i said, that ETC property is a very good indicator so far as imaging.
At a modest distance, in the right bass tuning, this would be very satisfying speaker.
OTH, it will not produce much bass and if used in your box, you would want to model that driver in your box volume to see what port length gave the best results.
Your other options would be to use a tweeter that went down low and use a 6.5 inch woofer. That old speaker i was working on has 2x 5 inch woofers and the fostex .
For that you will need a new crossover. IF you have a lot of overlap, and drivers less than 1/4 wl at crossover, a first order crossover can sum into a "no phase shift" crossover like a single driver, unlike all the other named slopes 2nd order and above.
Alternately, if your boxes went down into the 60's alone, you would be able to hid a small subwoofer the do that bottom octave or more.
I have not looked at that driver so far as bass in many years but the measurements yesterday I thought were worth mentioning.
Subwoofers are the easiest speakers to make and with a low enough crossover can blend in.
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