Good morning everyone,
I am an Italian enthusiast and this is the first time I have written, sorry for any English mistakes.
I've been having fun with diy speakers for fifty years.
I am now in possession of two pairs of Altec 420a biflex.
I have seen the features and different achievements on the web.
But I have a particular idea:
In your opinion, is it possible to make a speaker with a D'Appolito type configuration with a possible tweeter in the center?
I also have two AMT1a and JBL 075 tweeters.
Programmable electronic crossover , biamp.
I'd like it in open baffle, maybe paired with the subwoofer I have: SVS PB16 ultra.
Or in a closed box even of large cubic capacity, I have no problems with space.
Thank you for your opinions.
I am an Italian enthusiast and this is the first time I have written, sorry for any English mistakes.
I've been having fun with diy speakers for fifty years.
I am now in possession of two pairs of Altec 420a biflex.
I have seen the features and different achievements on the web.
But I have a particular idea:
In your opinion, is it possible to make a speaker with a D'Appolito type configuration with a possible tweeter in the center?
I also have two AMT1a and JBL 075 tweeters.
Programmable electronic crossover , biamp.
I'd like it in open baffle, maybe paired with the subwoofer I have: SVS PB16 ultra.
Or in a closed box even of large cubic capacity, I have no problems with space.
Thank you for your opinions.
Hello, Guido,
To answer your first question, yes, it is possible to design a d'Appolito configuration. However due to the distance between the tweeter and the woodfers, the result is unpredictable as it may have serious peaks and dips. This is not to say that it will sound unpleasant. There are ways around such things but one needs a means of measure ing frequency response.
The use of an electronic crossover surely simplifies crossover design. Using a three way electronic crossover with a two way speaker system adds more creative versatility that would make some people wonder.
Below are two links, the first of which is for a spec sheet on the 075. Unfortunately, no actual data is supplied but if memory serves me well, its sensitivity is around 110dB, 1w1m.
The second link is to a page in my website pertaining to the Altec "biflex'.
https://www.lansingheritage.org/html/jbl/specs/home-comp/075.htm
https://www.ln271828.net/ALTEC415CBiFlex.html
Robert
To answer your first question, yes, it is possible to design a d'Appolito configuration. However due to the distance between the tweeter and the woodfers, the result is unpredictable as it may have serious peaks and dips. This is not to say that it will sound unpleasant. There are ways around such things but one needs a means of measure ing frequency response.
The use of an electronic crossover surely simplifies crossover design. Using a three way electronic crossover with a two way speaker system adds more creative versatility that would make some people wonder.
Below are two links, the first of which is for a spec sheet on the 075. Unfortunately, no actual data is supplied but if memory serves me well, its sensitivity is around 110dB, 1w1m.
The second link is to a page in my website pertaining to the Altec "biflex'.
https://www.lansingheritage.org/html/jbl/specs/home-comp/075.htm
https://www.ln271828.net/ALTEC415CBiFlex.html
Robert
On a lark -- have them point toward each other up/down-firing slot-loaded, tweeter in between. Align acoustic centers and minimize C2C.
Thank you Robert and WChang for your interventions and advice.
Robert: I know your website that I have already visited several times, it is full of useful information and advice.
For now studying the project, I have started using REW with Umik 1 microphone for measurements. It is very useful even if not simple. I have to learn.
I ask for some advice:
From the explanations of the D'Appolito theory that I read on the web, a third-order crossover filter is recommended. Is that correct and why 18db/Oct.? Is there a particular reason? However, for now I'm studying the size and the panel for open baffle. I have seen numerous achievements with the biflex 420s. I think I predict a cut-off between 100 and 200 hz to reduce the size, adding two woofers that I already have in separate closed boxes.
Thanks again and best regards
Guy
Robert: I know your website that I have already visited several times, it is full of useful information and advice.
For now studying the project, I have started using REW with Umik 1 microphone for measurements. It is very useful even if not simple. I have to learn.
I ask for some advice:
From the explanations of the D'Appolito theory that I read on the web, a third-order crossover filter is recommended. Is that correct and why 18db/Oct.? Is there a particular reason? However, for now I'm studying the size and the panel for open baffle. I have seen numerous achievements with the biflex 420s. I think I predict a cut-off between 100 and 200 hz to reduce the size, adding two woofers that I already have in separate closed boxes.
Thanks again and best regards
Guy
“”up/down-firing slot-loaded”” I didn't understand what that means. Excuse me, I don't know English well and I often use machine translation.
I know the push-pull with the two speakers with the front face against each other. If that's it doesn't seem like the case to me. I was thinking of putting the two speakers in a vertical line and tweeter in the center. Both headed forward
I know the push-pull with the two speakers with the front face against each other. If that's it doesn't seem like the case to me. I was thinking of putting the two speakers in a vertical line and tweeter in the center. Both headed forward
One issue with d'Appolito configuration is C2C being very large. Slot loaded means face-to-face with a gap in between, drivers in-phase (not push-pull). This usually reduces C2C, besides having on-axis low-pass-filter effect while extending bass lower. Horizontal dispersion is very good if gap is not too narrow (drivers point up/down).
There may be a language issue here, but what you're describing as I understand it is just wrong. Slots are fine for subwoofers. Not for midwoofers.
No problem, given the wide gap needed for tweeter, "slot-loaded" isn't the best description. This unusual clam-like configuration ought to reduce center-to-center distance and mid-high-frequency comb-filtering. OP might experiment using a pair of bookshelf speakers one placed over the other, varying the in-between gap and angle.
My highest-fidelity diy to-date happens to use a 5" biflex-like fullrange (multiple concentric zones) up-firing slot-loaded ML-TQWT (back horn) tower.
https://www.diyaudio.com/community/threads/full-range-speaker-photo-gallery.65061/post-7675238
(See also LX-configured OB/omni pairings in same thread.)
My highest-fidelity diy to-date happens to use a 5" biflex-like fullrange (multiple concentric zones) up-firing slot-loaded ML-TQWT (back horn) tower.
https://www.diyaudio.com/community/threads/full-range-speaker-photo-gallery.65061/post-7675238
(See also LX-configured OB/omni pairings in same thread.)
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By chance (search Bing "loudspeaker BR design" auto-display row of Images) found this:
https://fohonline.com/articles/tech-feature/dyi-loudspeaker-design-the-bc-215-dcx/
https://fohonline.com/articles/tech-feature/dyi-loudspeaker-design-the-bc-215-dcx/
For a real d'appolito system the two midwoofer centers distance must be max 2/3 wavelengths of the crossover frequency.
Considering the two 15" woofers and disregarding the dimension of the tweeter for now you need a crossover frequency of 680 Hz or lower. Every crossover frequency above that is not a real d'appolito system.
Thanks, Guy for the compliment on my website.
The advantage(s) of a third order filter are as follows, according to my understanding.
Higher order filters are more complex, have added insertion loss and can cost much more, especially if one uses AWG 12 or AWG 14 wire in air core coils and exotic capacitors. I've seen 10uF caps costing as much as $130 each. Higher order filters reduce having two speakers playing the same frequencies around the crossover point. Electronic crossovers sometimes use 4th order filters which reduces this property. Also, electronic filters are isolated from the load (the speaker). A filter works best when its output impedance matches the load impedance. Since impedance is frequency dependent, both the output impedance of the filter and that of the load are varying. The question is are they varying in unison. They might with perfect inductors and capacitors, but such devices don't exist. The voice coil is also an imperfect inductor. Impedance mismatch results in a change in power transfer but this effect might be small.
Your prediction of the cutoff below 200hz is in corroboration with that which was measured in my room. (bottom graph in that biflex page.)
The main disadvantage of electronic crossovers is the additional expense of amplifiers and the crossover itself unless one buys boutique priced passive components which can drive the cost of a passive network to the ceiling. Some advantages are the lack of insertion loss which, in all honesty is small, the ability to easily select crossover frequencies and as shown above, less phase shift.
I downloaded the Room EQ Wizard and user's manual as you aroused my curiosity. All I need is a USB mic and that UMIK mic is reasonably priced. After reading the calibration procedure of the REW, I see what you mean about the lack of simplicity. I've been spoiled with the LMS system and the CLIO, both of which are calibrated to their included mics.
I have not studied the workings of the d'Appolito configuration. STV (post #11) seems to have a much better understanding of it. Based on that and respect for Mr. d'Appolito's design, I'll refer to such a configuration as MTM.
The advantage(s) of a third order filter are as follows, according to my understanding.
Higher order filters are more complex, have added insertion loss and can cost much more, especially if one uses AWG 12 or AWG 14 wire in air core coils and exotic capacitors. I've seen 10uF caps costing as much as $130 each. Higher order filters reduce having two speakers playing the same frequencies around the crossover point. Electronic crossovers sometimes use 4th order filters which reduces this property. Also, electronic filters are isolated from the load (the speaker). A filter works best when its output impedance matches the load impedance. Since impedance is frequency dependent, both the output impedance of the filter and that of the load are varying. The question is are they varying in unison. They might with perfect inductors and capacitors, but such devices don't exist. The voice coil is also an imperfect inductor. Impedance mismatch results in a change in power transfer but this effect might be small.
Your prediction of the cutoff below 200hz is in corroboration with that which was measured in my room. (bottom graph in that biflex page.)
The main disadvantage of electronic crossovers is the additional expense of amplifiers and the crossover itself unless one buys boutique priced passive components which can drive the cost of a passive network to the ceiling. Some advantages are the lack of insertion loss which, in all honesty is small, the ability to easily select crossover frequencies and as shown above, less phase shift.
I downloaded the Room EQ Wizard and user's manual as you aroused my curiosity. All I need is a USB mic and that UMIK mic is reasonably priced. After reading the calibration procedure of the REW, I see what you mean about the lack of simplicity. I've been spoiled with the LMS system and the CLIO, both of which are calibrated to their included mics.
I have not studied the workings of the d'Appolito configuration. STV (post #11) seems to have a much better understanding of it. Based on that and respect for Mr. d'Appolito's design, I'll refer to such a configuration as MTM.
Thank you Robert for your interest.
For Robert
I have several amplifiers in the house and already the electronic crossover in my Lyngdorf dpa1 preamplifier, with selectable frequencies and filters of different gradient.
It's easy to try. A friend can lend me a Behringer DCX2496 Ultradrive Pro (he knows how to use it well! Not me!).
For everyone.
Your answers are very useful.
Now I understand the proposed configuration and the criticality due to the large size of the speakers, which I partly feared.
I think it's better to test each speaker on an open baffle 100x100 cm flat panel and measure the response with REW and Umik microphone. Then I'll decide what to do. Checked the frequency response, as a final project I could mount them in vertical line, open baffle.
I cut the speaker closer to the floor at one frequency lower than the other as reinforcement on bass / medium bass, if necessary.
Tweeter jbl 075 or ess amt placed at the top.
Active bi/triamp to be defined after measurements.
What do you think?
P.S. I hope the content is clear despite the automatic translation.
For Robert
I have several amplifiers in the house and already the electronic crossover in my Lyngdorf dpa1 preamplifier, with selectable frequencies and filters of different gradient.
It's easy to try. A friend can lend me a Behringer DCX2496 Ultradrive Pro (he knows how to use it well! Not me!).
For everyone.
Your answers are very useful.
Now I understand the proposed configuration and the criticality due to the large size of the speakers, which I partly feared.
I think it's better to test each speaker on an open baffle 100x100 cm flat panel and measure the response with REW and Umik microphone. Then I'll decide what to do. Checked the frequency response, as a final project I could mount them in vertical line, open baffle.
I cut the speaker closer to the floor at one frequency lower than the other as reinforcement on bass / medium bass, if necessary.
Tweeter jbl 075 or ess amt placed at the top.
Active bi/triamp to be defined after measurements.
What do you think?
P.S. I hope the content is clear despite the automatic translation.
The automatic translation device you are using seems to be close to perfect.
I downloaded a pdf user's manual on the Lyngdorf amplifier. Quite the unit. A note of caution, if I may. Those Altecs are over 50 years old; the adhesives holding the cone to the voice coil as well as the adhesive holding the coil windings to the bobbin have also aged and may have become brittle. Excessive diaphragm excursion can cause the concentricity of the coil in the gap to be compromised. Also, percussive bass, depending on the power applied can cause the junction of the cone apex to the coil form to crack not to mention the possibility of the coil windings to unravel. I say this because that amplifier uses a microphone which implies it has automatic room eq. Unfortunately, the amplifier doesn't know the age of the Altecs. However, the manual suggests a subwoofer to mains filter of around 100hz to 200hz. IMHO, I'd set it as close to 200hz as possible. This will suppress percussive bass to the Altecs. The gap clearance in the motor assembly is very small, around 0.007" (0.18mm). The coil wire, if I am correct, may very well be aluminum. If the coil to cone junction is compromised, the wire(s) may break at that junction, rendering repair close to impossible.
Time takes its toll on everything, perhaps with one exception. It has been very eloquently said, and I quote, "All things fear time but time fears the pyramids."
Robert
I downloaded a pdf user's manual on the Lyngdorf amplifier. Quite the unit. A note of caution, if I may. Those Altecs are over 50 years old; the adhesives holding the cone to the voice coil as well as the adhesive holding the coil windings to the bobbin have also aged and may have become brittle. Excessive diaphragm excursion can cause the concentricity of the coil in the gap to be compromised. Also, percussive bass, depending on the power applied can cause the junction of the cone apex to the coil form to crack not to mention the possibility of the coil windings to unravel. I say this because that amplifier uses a microphone which implies it has automatic room eq. Unfortunately, the amplifier doesn't know the age of the Altecs. However, the manual suggests a subwoofer to mains filter of around 100hz to 200hz. IMHO, I'd set it as close to 200hz as possible. This will suppress percussive bass to the Altecs. The gap clearance in the motor assembly is very small, around 0.007" (0.18mm). The coil wire, if I am correct, may very well be aluminum. If the coil to cone junction is compromised, the wire(s) may break at that junction, rendering repair close to impossible.
Time takes its toll on everything, perhaps with one exception. It has been very eloquently said, and I quote, "All things fear time but time fears the pyramids."
Robert
Vented w/slots with a directed MTM as pictured, makes more sense than the front-loaded slot I was understanding it, which was up and down firing drivers (like a PPSL sub with push-push) and a tweeter nestled in there.
Robert, thank you very much for the advice. I know they are delicate speakers and of course I will cut them at least 200 hz.
The lingdorf drc luckily works in attenuation and not increase. Anyway I'll be very careful.
I will return to the topic when I have made progress.
Regards
Guido
The lingdorf drc luckily works in attenuation and not increase. Anyway I'll be very careful.
I will return to the topic when I have made progress.
Regards
Guido
Guido, If by your words "works in attenuation" you refer to its equalizer, that is the first I've heard about for decades. I recall reading a paper some time in the late seventies about such equalization, especially in the lower register. Many times I've tried to write a brief explanation as to why but it always ended up in a lengthy diatribe. Basically, serious peaks and dips in the bass response in a room are due to the relationship between the frequency wavelengths and the room's dimensions. Attempts to briefly explain why boosting doesn't work proved futile. All the happens is driving the amplifier to the point of clipping and possibly destroying a pair of woofers and sometimes a pair of tweeters. That may be what happened to the tweeter in the 602D I have that was converted to a 415C prior to my acquisition of it. When an amplifier clips, it's output is loaded with harmonics of the fundamental that caused the clipping and those harmonics are at full power output which can destroy a tweeter in milliseconds, especially if the amplifier is of what I refer to as an arc welder. (>300W)
Robert
Robert
It serves absolutely no benefit what so ever.
As noted to actually work you lower the crossover
frequency much much lower to work
Since spreading out 2 mids or 2 woofers
makes the center to center.
WAY to far apart.
It is that simple. It looks neat and magical to
people for some reason.
Your stuck finding or stressing tweeters
to cross lower. That is it.
It is expensive and difficult enough to cross a 15"
at 700 to 800 Hz
So why spread them apart even farther.
and move down too 500 or 300 Hz
Together it is 30 inches, add the tweeter distance
The question is, what crossover frequency/driver
for a 50 inch woofer.
As noted in post 17, since you are raising a woofer
way to high above the floor, and then no where close
to the ceiling. Then expect a whole bunch of response
dips from the floor and sidewall. By having a second woofer
WAY to high and WAY to far apart in the first place.
So even if you fix the tweeter issue.
You have a woofer TOO high and expect dips
in the response regardless
As noted to actually work you lower the crossover
frequency much much lower to work
Since spreading out 2 mids or 2 woofers
makes the center to center.
WAY to far apart.
It is that simple. It looks neat and magical to
people for some reason.
Your stuck finding or stressing tweeters
to cross lower. That is it.
It is expensive and difficult enough to cross a 15"
at 700 to 800 Hz
So why spread them apart even farther.
and move down too 500 or 300 Hz
Together it is 30 inches, add the tweeter distance
The question is, what crossover frequency/driver
for a 50 inch woofer.
As noted in post 17, since you are raising a woofer
way to high above the floor, and then no where close
to the ceiling. Then expect a whole bunch of response
dips from the floor and sidewall. By having a second woofer
WAY to high and WAY to far apart in the first place.
So even if you fix the tweeter issue.
You have a woofer TOO high and expect dips
in the response regardless
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