Kram:
With the oscilloscope and microphone, we have all we need to conduct frequency response tests for the tweeter. We will have to conduct them for the woofer as well, in any case.
There is no compelling reason to buy the Audax tweeters, unless you simply feel that you prefer new tweeters.
Anyway, let me know what you decide.
With the oscilloscope and microphone, we have all we need to conduct frequency response tests for the tweeter. We will have to conduct them for the woofer as well, in any case.
There is no compelling reason to buy the Audax tweeters, unless you simply feel that you prefer new tweeters.
Anyway, let me know what you decide.
Well, did some messing around with this setup, so here goes:
After downloading the oscilloscope, put it on the screen. Also make sure you have a microphone set in front of the tweeter-very close. Along the top of the oscilloscope are many pushbottuns. Counting from the left, press buttons #:
1 ,3, 6, 9, 11
When the waves go UP one division, they are 6 dB up. When they go down 1 division, they are 6 dB down.
Then just simply start at say, 8,000 Hz on the test generator, and work your way down until you see the response drop. Note the frequency where the response begins to drop, and note the frequency where the response is 2 horizontal lines down. It is 12 dB down at that point.
Then we will be able to tell how to crossover from the woofer to the tweeter.
After you have done that, you might want to test the woofer, just for accuracy's sake. Pay attention to that little anomaly around 2,000 Hz.
After downloading the oscilloscope, put it on the screen. Also make sure you have a microphone set in front of the tweeter-very close. Along the top of the oscilloscope are many pushbottuns. Counting from the left, press buttons #:
1 ,3, 6, 9, 11
When the waves go UP one division, they are 6 dB up. When they go down 1 division, they are 6 dB down.
Then just simply start at say, 8,000 Hz on the test generator, and work your way down until you see the response drop. Note the frequency where the response begins to drop, and note the frequency where the response is 2 horizontal lines down. It is 12 dB down at that point.
Then we will be able to tell how to crossover from the woofer to the tweeter.
After you have done that, you might want to test the woofer, just for accuracy's sake. Pay attention to that little anomaly around 2,000 Hz.
Hi
so far i have just measured the tweeters response, 1st with the cap and then a second time without it.
With cap
@8000Hz there was no output on the scope but i could hear it.
5039Hz 1 division on scope
4756 2 divisions
4000 4 divisions
3563 3 divisions
3363 3.5 divisions
3174 2.5 divisions
2923 2 divisions
2000 1 divisions
No cap
@8000Hz there was no output on the scope but i could hear it.
5339 1 division
5039 3 divisions
4756 6.5 divisions
4237 8+ divisions (off scope)
3177 7 divisions
2996 8 divisions
2828 6 divisions
2244 5 divisions
2000 4.5 divisions
i will get the woofer done at a later date. what frequency range should i be using for this?
Thanks.
so far i have just measured the tweeters response, 1st with the cap and then a second time without it.
With cap
@8000Hz there was no output on the scope but i could hear it.
5039Hz 1 division on scope
4756 2 divisions
4000 4 divisions
3563 3 divisions
3363 3.5 divisions
3174 2.5 divisions
2923 2 divisions
2000 1 divisions
No cap
@8000Hz there was no output on the scope but i could hear it.
5339 1 division
5039 3 divisions
4756 6.5 divisions
4237 8+ divisions (off scope)
3177 7 divisions
2996 8 divisions
2828 6 divisions
2244 5 divisions
2000 4.5 divisions
i will get the woofer done at a later date. what frequency range should i be using for this?
Thanks.
Kram:
I am thrown for a loop. The frequency response test you just did seems to indicate a tweeter with a peak at 4,000 Hz and a gradual rolloff in either direction from there.
Acoustic Research-a fine and respected company-would not make such a tweeter.
Just for a piece of advice, try putting the microphone as close to the tweeter as possible and see what happens. Just try 2 tones-8,000Hz and 4,000 Hz-to see if they are even remotely level.
If not, try the opposite approach. Put the speaker on the floor facing up, and hold the microphone a yard away. Again, see if 8,000 Hz is any closer to the level of the 4,000 Hz tone.
Incidentally, what amp are you running this from? Is it hooked up to an equalizer? Is the equalizer turned off?
How are the tone controls set? Level, I hope. We want a flat signal from 1,500 Hz to 20,000 Hz.
If you have a disposable set of old Walkman headphones, you can cut one of the headphones off, plug it into the sound card, take the 2 wires from the removed headphone and attach them to the terminals of the tweeter-one wire to the "+", the other to the "-". This should measure the amplitude of the signal going to the tweeters-wheter it is flat, (equal amplitude at all frequencies), or not.
I am thrown for a loop. The frequency response test you just did seems to indicate a tweeter with a peak at 4,000 Hz and a gradual rolloff in either direction from there.
Acoustic Research-a fine and respected company-would not make such a tweeter.
Just for a piece of advice, try putting the microphone as close to the tweeter as possible and see what happens. Just try 2 tones-8,000Hz and 4,000 Hz-to see if they are even remotely level.
If not, try the opposite approach. Put the speaker on the floor facing up, and hold the microphone a yard away. Again, see if 8,000 Hz is any closer to the level of the 4,000 Hz tone.
Incidentally, what amp are you running this from? Is it hooked up to an equalizer? Is the equalizer turned off?
How are the tone controls set? Level, I hope. We want a flat signal from 1,500 Hz to 20,000 Hz.
If you have a disposable set of old Walkman headphones, you can cut one of the headphones off, plug it into the sound card, take the 2 wires from the removed headphone and attach them to the terminals of the tweeter-one wire to the "+", the other to the "-". This should measure the amplitude of the signal going to the tweeters-wheter it is flat, (equal amplitude at all frequencies), or not.
Kram:
Just to cover all the bases, you might try going to the Classic Speaker pages, registering, enter the AR section and post a question about these AR tweeters from the AR 18 BX. Here is the link:
http://www.arsenal.net/cgi-bin/dcforum/dcboard.cgi
I have some cookie situation that prevents me from entering some forums. Apparently, that is one. But there is no reason that should prevent you from benefitting from the knowledge of the people there.
Simply say that you are substituting an Audax AP210ZO for the original woofer, porting it, and plan on using the AR 18 BX tweeter. Ask them about the quality of the AR tweeter as opposed to a modern Audax tweeter-how much improvement would there really be?
Finally, ask them about the crossover point and slope, (6 dB, 12 dB or 18 dB) of the AR 18 BX tweeters.
Even if you get the answer, there is still no reason you should not have a successful frequency response test. But it is wise to use whatever avenues of knowledge are out there.
I will be checking that AR forum-I can read it, but I cannot post on it-to see what the answers are. Once you get an answer, (or even if you don't), come on back here and we can make a decision. I am not trying to shunt you off to another board, just trying to get a supplementary opinion.
You might even try copying the frequency response of the Audax woofer to that forum. They might even have some ideas on how to integrate it into the AR 18 BX tweeter.
Again, I am not trying to send you elsewhere. I am getting a kick out of this. I just want to see what people who fix and repair AR's have to say about that tweeter. Then come back.
Just to cover all the bases, you might try going to the Classic Speaker pages, registering, enter the AR section and post a question about these AR tweeters from the AR 18 BX. Here is the link:
http://www.arsenal.net/cgi-bin/dcforum/dcboard.cgi
I have some cookie situation that prevents me from entering some forums. Apparently, that is one. But there is no reason that should prevent you from benefitting from the knowledge of the people there.
Simply say that you are substituting an Audax AP210ZO for the original woofer, porting it, and plan on using the AR 18 BX tweeter. Ask them about the quality of the AR tweeter as opposed to a modern Audax tweeter-how much improvement would there really be?
Finally, ask them about the crossover point and slope, (6 dB, 12 dB or 18 dB) of the AR 18 BX tweeters.
Even if you get the answer, there is still no reason you should not have a successful frequency response test. But it is wise to use whatever avenues of knowledge are out there.
I will be checking that AR forum-I can read it, but I cannot post on it-to see what the answers are. Once you get an answer, (or even if you don't), come on back here and we can make a decision. I am not trying to shunt you off to another board, just trying to get a supplementary opinion.
You might even try copying the frequency response of the Audax woofer to that forum. They might even have some ideas on how to integrate it into the AR 18 BX tweeter.
Again, I am not trying to send you elsewhere. I am getting a kick out of this. I just want to see what people who fix and repair AR's have to say about that tweeter. Then come back.
Hi.
i just posted a message on the AR forum, im under the name of Kram on there too.
i dont know what went wrong with the frequency response test, i did what you asked me to do. do you think it could be the mic i was using? my brother said it is supposed to be used for micing instrument amps.
i guess i will just have to do it again.
thanks.
i just posted a message on the AR forum, im under the name of Kram on there too.
i dont know what went wrong with the frequency response test, i did what you asked me to do. do you think it could be the mic i was using? my brother said it is supposed to be used for micing instrument amps.
i guess i will just have to do it again.
thanks.
Kram said:
Yes, you did. I am not saying you did anything wrong, just trying to find a reason why the frequency response test did not work out well. Either the tweeters are severely damaged, or the signal it is being given is not at equal amplitude for all frequencies tested. I am not sure I have ever come across a damaged tweeter that played well at 4,000 Hz but sharply sloped down from there on either side.
When you do the test again, try testing both tweeters. Maybe one of them is damaged.
I would tend to think that it is not the microphone. Maybe the instrumentation amp. Try the output of the instrumentaion amp if you can with that Walkman setup, provided you have a set of phones to waste.
I will check your post in the AR forum, and get back to you.
Kram:
It is good that you decided to retest.
Make sure any equalizers are not in the system-turning them off is the best way to ensure that.
Make certain that any bass or treble controls are turned to "flat"-neither plus or minus. Neutral, as it were.
I have one theory as to why the tweeter peaks at 4,000 Hz and slopes down from there in both directions-up and down.
Most 8 inch 2-way speakers, (that is, only containing a woofer and tweeter), cross over between 2,000 Hz and 4,000 Hz. They can cross over elsewhere, but that range is most common.
The information at the Acoustic Research Clssic Speaker site seemed to indicate that most 8 inch AR woofers crossed over at 2,000 Hz, but there was no sure indication that the AR 18BX did so. So the possiblilty of a 4,000 Hz cross over for the AR 18BX exists.
Crossing over means that each respective driver stops playing at a certain point. So if a woofer starts to gradually play less loud at 4,000 Hz, the tweeter should start playing at 4,000 Hz and continue up to 15,000 Hz and beyond. The tweeter should begin to play less and less the farther below 4,000 Hz you go., just as the woofer should play less and less loud the farther above 4,000 Hz you go.
If you turn the treble tone control to cut the treble, at some point you will hit the place where the response begins to go down above 4,000 Hz.
So if the woofer is set to cross over at 4,000 Hz, then that is the reason for the slope on the low end. And if the trble contol is set to cut the treble, that would explain the rolloff on the high end.
Well, it's a working theroy anyway, LOL.
Anyhow, please retest. Let us see what we get.
It is good that you decided to retest.
Make sure any equalizers are not in the system-turning them off is the best way to ensure that.
Make certain that any bass or treble controls are turned to "flat"-neither plus or minus. Neutral, as it were.
I have one theory as to why the tweeter peaks at 4,000 Hz and slopes down from there in both directions-up and down.
Most 8 inch 2-way speakers, (that is, only containing a woofer and tweeter), cross over between 2,000 Hz and 4,000 Hz. They can cross over elsewhere, but that range is most common.
The information at the Acoustic Research Clssic Speaker site seemed to indicate that most 8 inch AR woofers crossed over at 2,000 Hz, but there was no sure indication that the AR 18BX did so. So the possiblilty of a 4,000 Hz cross over for the AR 18BX exists.
Crossing over means that each respective driver stops playing at a certain point. So if a woofer starts to gradually play less loud at 4,000 Hz, the tweeter should start playing at 4,000 Hz and continue up to 15,000 Hz and beyond. The tweeter should begin to play less and less the farther below 4,000 Hz you go., just as the woofer should play less and less loud the farther above 4,000 Hz you go.
If you turn the treble tone control to cut the treble, at some point you will hit the place where the response begins to go down above 4,000 Hz.
So if the woofer is set to cross over at 4,000 Hz, then that is the reason for the slope on the low end. And if the trble contol is set to cut the treble, that would explain the rolloff on the high end.
Well, it's a working theroy anyway, LOL.
Anyhow, please retest. Let us see what we get.
Someone called nigel got back to me on the AR forum but i didnt understand what he was trying to tell me with the link he suggested to me http://www.partsexpress.com/resources/xover.html
Im sorry i havent had time to redo the tests as ive been too busy earning some money at last. I will probably get them done when it rains (should be soon as im in England and its summer, apparantly ).
thanks.
Im sorry i havent had time to redo the tests as ive been too busy earning some money at last. I will probably get them done when it rains (should be soon as im in England and its summer, apparantly
).thanks.
I just glanced up to see that you are browsing the forum. Any progress on why the response is what it is? I strongly suspect some setting on the amp. Maybe it's the low volume compensation button or something. You've heard of low volume level compensation buttons? They used to have them-I don't know if the modern receivers do.
Probably laster today I will experiment with that Walkman headphone thing to convert to measure voltage.
Probably laster today I will experiment with that Walkman headphone thing to convert to measure voltage.
hello,
i just repeated the test with 1 tweeter ( i dont know if its the same one i tested before) and ill do the 2nd one in a little while.
Here are the results.
8000 nothing on scope but can hear it
7000 nothing on scope but can hear it
6000 nothing on scope but can hear it
5000 2 divisions
4500 6 divisions
4000 6.5 divisions
3500 4 divisions
3000 4 divisions
2500 2 divisions
2000 1 divisions
1500 1 divisions
1000 less than 1 division
i also turned the frequency up to 20kHz from 8000Hz and nothing was showing on the scope but i could hear it all the way up.
all tone controls are turned to flat and the loudness thingy is off.
i got another reply on the AR forum if you have time to take a look i would be most thankfull.
i just repeated the test with 1 tweeter ( i dont know if its the same one i tested before) and ill do the 2nd one in a little while.
Here are the results.
8000 nothing on scope but can hear it
7000 nothing on scope but can hear it
6000 nothing on scope but can hear it
5000 2 divisions
4500 6 divisions
4000 6.5 divisions
3500 4 divisions
3000 4 divisions
2500 2 divisions
2000 1 divisions
1500 1 divisions
1000 less than 1 division
i also turned the frequency up to 20kHz from 8000Hz and nothing was showing on the scope but i could hear it all the way up.
all tone controls are turned to flat and the loudness thingy is off.
i got another reply on the AR forum if you have time to take a look i would be most thankfull.
Kram:
Read the response. Nigel is doing his best, but he really does not have any reference as to what the crossover frequency is. So he is assuming the tweeter is 8 ohms, mostly because he has no other choice.
Everything Nigel says is right on the money-assuming that the AR tweeter is a constant 8 ohms throughout it's range.
Eight inch speakers do not genrally cross over at 6,000 Hz, however.
When a speaker-whether tweeter, midrange or woofer-is at resonance in a normally set up closed box, (Qtc of .7-1.0), usually two things happen:
A) The response rolls off at or around the resonance frequency
B) The impedance goes up.
I am guessing that you are not crossing over at 6,000 Hz. I am guessing that the tweeter has a resonance frequency around 2,000 Hz, and that AR decided to use that in it's crossover design. Therefore instead of an impedance of 8 ohms, the tweeter has an impedance of 26 ohms around the crossover frequency of 2,000 Hz. So a 3 uF cap is necessary to add another 6 dB to the crossover slope under these circumstances.
That is my guess. I don't now. But a 6,000 Hz crossover for an eight inch speaker seems unlikely.
That is why we are conducting these tests.
I am going to assume that you have, or can obtain, a cheap pair of Walkman style headphones that can be sacrificed for this project. No need to give incriminating details as to how you obtained them, LOL. But most people have spare ones lying around from Walkman type cassette and even CD players that have long ago given up the ghost.
Later today I will post how to use a sacrificed set of Walkman headphones to plug into your sound card to measure the output of your amp directly. I have my pair right here that I picked up at the Everything For A Dollar Store and will give instructions in a post later today.
Assuming it works.
I could advise you to pick up a set of probes for your sound card, but that would violate the dictum of this thread, which is to get good, honest, hi fideltiy sound out of a pair of old, damaged speakers for the absolute least amount of money possible. That is one of the reasons I am getting a kick out of this project.
Once you can measure the output of an amp directly in volts or millivolts, you can compare the output of the tweeter through that amp. You don't need to know the output of the amp in real numbers, just see whether it gives out the same voltage at 2,000 Hz that it does at 4,000 Hz and 8,000 Hz. Then you can tell if the tweeter is giving that odd result, or the amp is going through some kind of filter. Even if the amp is going through some kind of filter, by comparison of the amp output and tweeter output at selected frequencies-maybe only 15 frequencies or so-you can still get a reading on the tweeter's response.
Figuring out what the amp is doing is a separate question. We are now interested only in making a speaker with reasonably flat response.
Get back to you later today. Due to six hour time difference, that might mean tomorrow morning for you.
Read the response. Nigel is doing his best, but he really does not have any reference as to what the crossover frequency is. So he is assuming the tweeter is 8 ohms, mostly because he has no other choice.
Everything Nigel says is right on the money-assuming that the AR tweeter is a constant 8 ohms throughout it's range.
Eight inch speakers do not genrally cross over at 6,000 Hz, however.
When a speaker-whether tweeter, midrange or woofer-is at resonance in a normally set up closed box, (Qtc of .7-1.0), usually two things happen:
A) The response rolls off at or around the resonance frequency
B) The impedance goes up.
I am guessing that you are not crossing over at 6,000 Hz. I am guessing that the tweeter has a resonance frequency around 2,000 Hz, and that AR decided to use that in it's crossover design. Therefore instead of an impedance of 8 ohms, the tweeter has an impedance of 26 ohms around the crossover frequency of 2,000 Hz. So a 3 uF cap is necessary to add another 6 dB to the crossover slope under these circumstances.
That is my guess. I don't now. But a 6,000 Hz crossover for an eight inch speaker seems unlikely.
That is why we are conducting these tests.
I am going to assume that you have, or can obtain, a cheap pair of Walkman style headphones that can be sacrificed for this project. No need to give incriminating details as to how you obtained them, LOL. But most people have spare ones lying around from Walkman type cassette and even CD players that have long ago given up the ghost.
Later today I will post how to use a sacrificed set of Walkman headphones to plug into your sound card to measure the output of your amp directly. I have my pair right here that I picked up at the Everything For A Dollar Store and will give instructions in a post later today.
Assuming it works.
I could advise you to pick up a set of probes for your sound card, but that would violate the dictum of this thread, which is to get good, honest, hi fideltiy sound out of a pair of old, damaged speakers for the absolute least amount of money possible. That is one of the reasons I am getting a kick out of this project.
Once you can measure the output of an amp directly in volts or millivolts, you can compare the output of the tweeter through that amp. You don't need to know the output of the amp in real numbers, just see whether it gives out the same voltage at 2,000 Hz that it does at 4,000 Hz and 8,000 Hz. Then you can tell if the tweeter is giving that odd result, or the amp is going through some kind of filter. Even if the amp is going through some kind of filter, by comparison of the amp output and tweeter output at selected frequencies-maybe only 15 frequencies or so-you can still get a reading on the tweeter's response.
Figuring out what the amp is doing is a separate question. We are now interested only in making a speaker with reasonably flat response.
Get back to you later today. Due to six hour time difference, that might mean tomorrow morning for you.
Kram:
Well, I broke up a Walkman pair of headphones, and seemed to get a decent set of wires to hook up to the sound card.
But that oscilloscope program was giving me wierd readings. So did another program I downloaded.
However my little cheap analogue voltmeter was rock steady.
I will check to see what the problem is with the oscilloscope program. However, I strongly suggest that you start asking around to see if you can borrow an inexpensive voltmeter just to run a test to see if your amp is giving out flat response at all frequencies.
If you have Radio Shack stores over there, you can always buy one, use it and return it a few days later for a refund, if it has to come down to that.
I am all for keeping costs low, but we don't want to get too bogged down jerry-rigging test equipment either. I mean, all we want to know is if the amp is giving out flat response at all frequencies. With a voltmeter, that is a 30 second test.
Well, I broke up a Walkman pair of headphones, and seemed to get a decent set of wires to hook up to the sound card.
But that oscilloscope program was giving me wierd readings. So did another program I downloaded.
However my little cheap analogue voltmeter was rock steady.
I will check to see what the problem is with the oscilloscope program. However, I strongly suggest that you start asking around to see if you can borrow an inexpensive voltmeter just to run a test to see if your amp is giving out flat response at all frequencies.
If you have Radio Shack stores over there, you can always buy one, use it and return it a few days later for a refund, if it has to come down to that.
I am all for keeping costs low, but we don't want to get too bogged down jerry-rigging test equipment either. I mean, all we want to know is if the amp is giving out flat response at all frequencies. With a voltmeter, that is a 30 second test.
Analog Meter vs. Oscilloscope Reading
Analog Meter is more like Human Ear
Oscilloscope reveals the truth
we doesn't "know" (of)
Kinda Like "holy book"
them oscilloscope
gromanswe
can not .see what micro.scope can .... see
can not hear what oscilloscope can not see
poor guy he is
really
just a penny left
Analog Meter is more like Human Ear
Oscilloscope reveals the truth
we doesn't "know" (of)
Kinda Like "holy book"
them oscilloscope
gromanswe
can not .see what micro.scope can .... see
can not hear what oscilloscope can not see
poor guy he is
really
just a penny left
I think I may have erred in referring you to freeware programs that might well be worthy, but probably require a little time to get used to. I do not use computers to test my speakers at home, and I thought I could find some freeware programs to substitute.
This is the test rig that I think would work.
The computer tone generator seems to work fine, so we will use that.
A microphone, which you already have.
Borrow, buy or otherwise obtain a voltmeter. Analog is preferred, but digital will do. For your purposes, the cheapest voltmeter is just as good as the most expensive on the market. You are just measuring AC volts.
A second amp to amplify the microphone. We well call this the mic amp. This could be an old boombox that you or a friend had around the house. This really should not be difficult to come by extremely cheaply,or for free. Plus an inexpensive adapter, (maybe 2 pds), to hook your microphone up to this amp/receiver/boombox.
What we do is:
We run the tones from 10,000 Hz down to 1000 Hz through the main amp-the amp that is going to run the speakers. The voltmeter is hooked up to the main amp's speaker output. The output should be rock steady. It doesn't matter if your speakers are hooked up to the amp for this test.
Next, hook the microphone up to the input of your mic amp. The aforementioned inexpensive adapter might be necessary to accomplish this if your mic amp does not have the right size jack. The voltmeter should be hooked up to the speaker outputs of this mic amp-easy enough to do if they are spring clips.
Hook your speaker or tweeter-whichever you are measuring-to the main amp. Send your test tones to the main amp. Make the volume low, but audible.
Hold the mic in front of the speaker to be tested.
Observe the voltmeter. Turn up the volume knob on the microphone amp until the voltmeter is at a suitable level to measure any voltage variations as you change frequencies.
These tests wiul tell us if the amp output is flat at all frequencies, and what the frequency response is.
This is the test rig that I think would work.
The computer tone generator seems to work fine, so we will use that.
A microphone, which you already have.
Borrow, buy or otherwise obtain a voltmeter. Analog is preferred, but digital will do. For your purposes, the cheapest voltmeter is just as good as the most expensive on the market. You are just measuring AC volts.
A second amp to amplify the microphone. We well call this the mic amp. This could be an old boombox that you or a friend had around the house. This really should not be difficult to come by extremely cheaply,or for free. Plus an inexpensive adapter, (maybe 2 pds), to hook your microphone up to this amp/receiver/boombox.
What we do is:
We run the tones from 10,000 Hz down to 1000 Hz through the main amp-the amp that is going to run the speakers. The voltmeter is hooked up to the main amp's speaker output. The output should be rock steady. It doesn't matter if your speakers are hooked up to the amp for this test.
Next, hook the microphone up to the input of your mic amp. The aforementioned inexpensive adapter might be necessary to accomplish this if your mic amp does not have the right size jack. The voltmeter should be hooked up to the speaker outputs of this mic amp-easy enough to do if they are spring clips.
Hook your speaker or tweeter-whichever you are measuring-to the main amp. Send your test tones to the main amp. Make the volume low, but audible.
Hold the mic in front of the speaker to be tested.
Observe the voltmeter. Turn up the volume knob on the microphone amp until the voltmeter is at a suitable level to measure any voltage variations as you change frequencies.
These tests wiul tell us if the amp output is flat at all frequencies, and what the frequency response is.
Kram:
I just wanted to add that I think that once we get this test rig squared away, all that we might have to do is put a notch filter on the Audax woofer for around 3000 Hz and we are all set. And notch filters are easy to do.
I am showing two graphs. The first will be a test speaker that AR had in an AR 17-an 8 inch only slightly larger than your AR 18BX. Forget the response hump at 100 Hz for the AR test speaker-note the high frequency response around 2,000 Hz.
I have read that AR used basically one speaker in all their 8 inch boxes. If the high frequency response of the AR 17 test speaker is the same as the regular AR speakers, (and I think that is likely), then note how the response is flat until 2,000 Hz, then goes down at 12 dB/octave.
I think a simple, inexpensive noltch filter will render the Audax very close to the AR woofer's response.
The main difference is that we will port the Audax, and the Audax looks to be about 2 dB more sensitive. I think the AR tweeters should still be able to keep up with it, though.
Here is the response curve of the AR 17 test speaker:
I just wanted to add that I think that once we get this test rig squared away, all that we might have to do is put a notch filter on the Audax woofer for around 3000 Hz and we are all set. And notch filters are easy to do.
I am showing two graphs. The first will be a test speaker that AR had in an AR 17-an 8 inch only slightly larger than your AR 18BX. Forget the response hump at 100 Hz for the AR test speaker-note the high frequency response around 2,000 Hz.
I have read that AR used basically one speaker in all their 8 inch boxes. If the high frequency response of the AR 17 test speaker is the same as the regular AR speakers, (and I think that is likely), then note how the response is flat until 2,000 Hz, then goes down at 12 dB/octave.
I think a simple, inexpensive noltch filter will render the Audax very close to the AR woofer's response.
The main difference is that we will port the Audax, and the Audax looks to be about 2 dB more sensitive. I think the AR tweeters should still be able to keep up with it, though.
Here is the response curve of the AR 17 test speaker:
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