About 15 years ago the church I go to was doing a clean out and they were gonna toss a pair of Argos column speakers in the dumpster so I asked if I could toss them in my car instead.
Maybe a year or two later I gutted the drivers and used the following drivers.
Four Dayton Audio DC-200-8 8" woofers wired in series/parallel for an 8 ohm load.
https://www.daytonaudio.com/product/25/dc200-8-8-classic-woofer-8-ohm
One Pyle Pro sealed back 8" midrange.
One Eminence APT-80 tweeter mounted to an adapter made out of a piece of wood so that it could mount to the 8" hole properly.
I used an Eminence three way crossover, a zobel network on the woofer and midrange and the proper resistors for the l-pads.
I proceeded to seal the cabinet up as best I could.
Until recently the speaker worked fine and I even built another one last year.
I recently found I had done the l-pads wrong so in the process of removing the back off one, the cabinet had to practically be destroyed.
The cabinets were made out of some type of chipboard or something not really meant for being hauled around like I use them as they were intended to be mounted to a wall for a few decades.
I used a third cabinet I have as the replacement.
I then realized only the original two (got two more for free for fixing an old Peavey powered mixer) are the exact same size and the other two are slightly different sizes.
So I came to the conclusion that it would be best to get two proper cabinets built for two reasons.
1. Much better durability and the ability to add handles and casters.
2. Can go with a larger cabinet for better bass response.
As is the speaker produces decent bass to about 35Hz and gradually rolls off below there.
Also the current cabinets when powered on about 200 watts sitting on concrete will walk backwards when lower bass is being played.
I can post measurements of the cabinet when I get home from work.
The cabinets just do fit in my car lengthwise. Given I'm using a small tweeter I could reduce the height of the speaker by maybe 3-4"
The speakers are arranged vertically and the cabinets are not much wider than the 8" drivers.
What should the width of the cabinet be?
I'd also like to make these powered speakers and install a decent quality full range plate amp that can put out at least 240 watts (higher wattage if used with a limiter) if there is such a thing. I'd recess the amp in the back panel so that the controls will not extend past the back panel of the speaker.
I know the depth of the cabinet will have to be increased for the plate amp to be able to fit inside.
For the drivers I may mount them from the front using t-nuts and will use grills that fit each speaker.
I may also use t-nuts for the rear panel so that I can easily open the cabinets if need be.
Also what should the thickness of the wood be?
Maybe a year or two later I gutted the drivers and used the following drivers.
Four Dayton Audio DC-200-8 8" woofers wired in series/parallel for an 8 ohm load.
https://www.daytonaudio.com/product/25/dc200-8-8-classic-woofer-8-ohm
One Pyle Pro sealed back 8" midrange.
One Eminence APT-80 tweeter mounted to an adapter made out of a piece of wood so that it could mount to the 8" hole properly.
I used an Eminence three way crossover, a zobel network on the woofer and midrange and the proper resistors for the l-pads.
I proceeded to seal the cabinet up as best I could.
Until recently the speaker worked fine and I even built another one last year.
I recently found I had done the l-pads wrong so in the process of removing the back off one, the cabinet had to practically be destroyed.
The cabinets were made out of some type of chipboard or something not really meant for being hauled around like I use them as they were intended to be mounted to a wall for a few decades.
I used a third cabinet I have as the replacement.
I then realized only the original two (got two more for free for fixing an old Peavey powered mixer) are the exact same size and the other two are slightly different sizes.
So I came to the conclusion that it would be best to get two proper cabinets built for two reasons.
1. Much better durability and the ability to add handles and casters.
2. Can go with a larger cabinet for better bass response.
As is the speaker produces decent bass to about 35Hz and gradually rolls off below there.
Also the current cabinets when powered on about 200 watts sitting on concrete will walk backwards when lower bass is being played.
I can post measurements of the cabinet when I get home from work.
The cabinets just do fit in my car lengthwise. Given I'm using a small tweeter I could reduce the height of the speaker by maybe 3-4"
The speakers are arranged vertically and the cabinets are not much wider than the 8" drivers.
What should the width of the cabinet be?
I'd also like to make these powered speakers and install a decent quality full range plate amp that can put out at least 240 watts (higher wattage if used with a limiter) if there is such a thing. I'd recess the amp in the back panel so that the controls will not extend past the back panel of the speaker.
I know the depth of the cabinet will have to be increased for the plate amp to be able to fit inside.
For the drivers I may mount them from the front using t-nuts and will use grills that fit each speaker.
I may also use t-nuts for the rear panel so that I can easily open the cabinets if need be.
Also what should the thickness of the wood be?
??? Obviously the baffle must be at least the width of the driver flange and we normally recommend 0.75"/1.8-9 cm thick no void plywood such as Baltic Birch, Apple Ply or marine grade for durability, rigid enough for bass response.
So are you wanting to know what net volume (Vb) for these drivers based on what depth, height? Vented or sealed or...?
Sealed.
Need to know the cabinet volume I need.
I did not get a chance yesterday to measure the original cabinet dimensions yesterday but will today.
Need to know the cabinet volume I need.
I did not get a chance yesterday to measure the original cabinet dimensions yesterday but will today.
According to BBP version 6 and using Dayton's published T-S parameters, 4 such speakers will require 1.7 cubic feet, optimum sealed with an f3 of 62hz.
As for material thickness, 3/4 inch (19mm) MDF will work fine and be a lot heavier than the chipboard of the originals. If you have money to spare, a high quality 3/4 inch birch plywood would be better but at a much higher cost. If plywood is your preference, keep in mind that so-called 3/4 inch plywood is only 23/32 inch thick, (18.25mm) 1/32nd thinner than 3/4 inch. This is not a problem if one keeps that in mind when making measurements for cutting the pieces.
Oh, BTW, these 4 units have the diaphragm radiating area of a 15".
On power limiting. I have seen demonstrated two such circuits. The first was in the early 70's at the Camelot Inn in Wappingers Falls, NY. The amp was a Dynaco 400 watt (arc welder). The turntable tonearm was raised and allowed to drop onto the record. The amplifier sensed the incoming surge and blocked the signal. Nothing was heard from the speakers.
The second was in Phoenix, AZ in the early 80's at a McIntosh demonstration at Jerry's Audio. Here, a squiggle tube (oscilloscope) was used to see the output waveform. A signal genny was used for the input. A resistive load was used to save the ears of attendees. The gain was cranked up and the sine wave increased until the gain was increased to the point of clipping the amp, which didn't happen. The protective circuit prevented that. Admittedly, this would cause compression at the point of clipping but that was easier to accept than blowing the tweeters, which are usually the first to suffer from a clipping amp. McIntosh patented that circuit under the name, PowerGuard.
As for material thickness, 3/4 inch (19mm) MDF will work fine and be a lot heavier than the chipboard of the originals. If you have money to spare, a high quality 3/4 inch birch plywood would be better but at a much higher cost. If plywood is your preference, keep in mind that so-called 3/4 inch plywood is only 23/32 inch thick, (18.25mm) 1/32nd thinner than 3/4 inch. This is not a problem if one keeps that in mind when making measurements for cutting the pieces.
Oh, BTW, these 4 units have the diaphragm radiating area of a 15".
On power limiting. I have seen demonstrated two such circuits. The first was in the early 70's at the Camelot Inn in Wappingers Falls, NY. The amp was a Dynaco 400 watt (arc welder). The turntable tonearm was raised and allowed to drop onto the record. The amplifier sensed the incoming surge and blocked the signal. Nothing was heard from the speakers.
The second was in Phoenix, AZ in the early 80's at a McIntosh demonstration at Jerry's Audio. Here, a squiggle tube (oscilloscope) was used to see the output waveform. A signal genny was used for the input. A resistive load was used to save the ears of attendees. The gain was cranked up and the sine wave increased until the gain was increased to the point of clipping the amp, which didn't happen. The protective circuit prevented that. Admittedly, this would cause compression at the point of clipping but that was easier to accept than blowing the tweeters, which are usually the first to suffer from a clipping amp. McIntosh patented that circuit under the name, PowerGuard.
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Here's the existing cabinet dimensions.
Height 49"
Width 9 1/2"
Depth 5 1/2"
Wood thickness 1/2"
The enclosure is 1.482 cubic feet not accounting the space taken up by the drivers.
I used this midrange
https://www.parts-express.com/Pyle-PDMR8-8-360-Watt-Sealed-Back-Midrange-Driver-292-2568?quantity=1
and this tweeter
https://www.parts-express.com/Eminence-APT-80-Super-Tweeter-with-80-Conical-Horn-290-532?quantity=1
Now the 1.7 cubic feet you mentioned does that take into account the space taken up by the drivers?
If so the internal dimensions should be
H 45" Took 4" off the height as the tweeter mounting flange is only 3.40" X 3.40".
W 10"
D 6.5"
For 1.693 cubic feet.
However given I have the midrange, tweeter and crossover along with the resistors for the l-pads and the resistors and caps for the zobel networks I may want to go to 1.8-2.0 cubic feet?
Taking into account that stuff the internal dimensions should be.
H 45"
W 11"
D 7"
for 2.005 cubic feet.
Now the speaker has always sounded good in the lower bass such that I really don't need a sub unless I want very heavy bass.
I suppose that without a measurement mic I would not get any precise measurements as to how flat the speaker is below 60Hz so I'd only be able to use my ears to approximate how it sounds.
Either way I can always add a powered sub for the bass.
I'd then get a speaker processor which would serve as the limiter and I could then EQ the system to the room I am in and save it as a preset.
These I am using primarily for DJ work.
I have the crossovers to build two more which I will do once I get the money to do so,
Do y'all think it's a good idea to build in a full range plate amp or should I just use an external amplifier?
Given the woofers, the speaker can handle 240 watts RMS, however I'd limit it to 200 watts RMS.
Height 49"
Width 9 1/2"
Depth 5 1/2"
Wood thickness 1/2"
The enclosure is 1.482 cubic feet not accounting the space taken up by the drivers.
I used this midrange
https://www.parts-express.com/Pyle-PDMR8-8-360-Watt-Sealed-Back-Midrange-Driver-292-2568?quantity=1
and this tweeter
https://www.parts-express.com/Eminence-APT-80-Super-Tweeter-with-80-Conical-Horn-290-532?quantity=1
Now the 1.7 cubic feet you mentioned does that take into account the space taken up by the drivers?
If so the internal dimensions should be
H 45" Took 4" off the height as the tweeter mounting flange is only 3.40" X 3.40".
W 10"
D 6.5"
For 1.693 cubic feet.
However given I have the midrange, tweeter and crossover along with the resistors for the l-pads and the resistors and caps for the zobel networks I may want to go to 1.8-2.0 cubic feet?
Taking into account that stuff the internal dimensions should be.
H 45"
W 11"
D 7"
for 2.005 cubic feet.
Now the speaker has always sounded good in the lower bass such that I really don't need a sub unless I want very heavy bass.
I suppose that without a measurement mic I would not get any precise measurements as to how flat the speaker is below 60Hz so I'd only be able to use my ears to approximate how it sounds.
Either way I can always add a powered sub for the bass.
I'd then get a speaker processor which would serve as the limiter and I could then EQ the system to the room I am in and save it as a preset.
These I am using primarily for DJ work.
I have the crossovers to build two more which I will do once I get the money to do so,
Do y'all think it's a good idea to build in a full range plate amp or should I just use an external amplifier?
Given the woofers, the speaker can handle 240 watts RMS, however I'd limit it to 200 watts RMS.
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Two cubic feet will do just fine. The 1.7 ft^3 from BBP is after all internal devices have been accounted for. The 4 magnets and the 4 cone frustrums sum to 140 in^3. Add to that the estimated volume occupied by the midrange and the tweeter of 35 in^3 for a total internal displacement of 175 in^3.
Now, if the 1.7 ft^3 enclosure was not adjusted for that, we'd end up with an internal volume of 1.6 ft^3, the yellow trace in the graphs below.
If you went to 2 ft^3 and didn't account for speaker and cleat displacement, we'd have 1.899ft^3, the blue/green trace.
The red trace is the exact internal volume of 1.7 ft^3 after all volume displacing components have been accounted for.
Volume displacing components not only includes the speakers but also any internal bracing, cleats and as you mentioned, the plate amplifier. Judging by the traces below, you're right about just going with an internal volume of 2 ft^3 with no concern for displacement by internal components. The end result will be close to any of these traces.
In the graphs below, NA is normalized amplitude response, expressed in dB relative to the peak.
CA is custom amplitude response, expressed in Db SPL as a function of power, which can be changed.
AP is the acoustical output as a function of maximum power applied, expressed in dB at 1 meter.
EP is the maximum electrical input power the speaker can handle within its Xmax. It's expressed in watts as a function of frequency. At 40hz, the woofers can handle 16 watts. Any more will overdrive the speakers.
CD is cone displacement.
VV is vent air velocity, not applicable here.
I is system impedance, Z, applies to the 4 woofers only.
P is phase response, expressed in degrees.
GD is group delay, which is phase response expressed in milli seconds.
If you want the rest of the graphs, just ask.
As can be seen, slight closed box internal volume variations of as much as 20%, 1.6ft^3 to 2.0ft^3 are insignificant, at least for these speakers. If memory serves me well, such a volume variation in a vented box is not as forgiving.
Some noted data.
1.6ft^3 f3=62hz, Xmax reached at 50hz, peak impedance=21.7 ohms at 63hz
1.7ft^3 f3=62hz, Xmax reached at 52hz, peak impedance=22 ohms at 62hz
2.0ft^3 f3=61hz, Xmax reached at 54hz, peak impedance=22.3 ohms at 59hz.
What this shows that as a sealed box volume is increased, f3 may get lower but the caveat is that Xmax is reached sooner. Some will make a sealed box larger to get lower bass using a bass boost giving no thought to what's happening to Xmax.
I have 4 of those DC200-8 units and a pair of test enclosures of 3ft^3 each. They can be filled to 2ft^3 and a new front baffle added. I also have test equipment like LMS and CLIO and can run near field responses to get a better idea of how these things perform. Judging by the BBP traces, one speaker in 0.43ft^3 will perform the same as 4 in 1.7ft^3 with exception of the power handling capacity.
My apologies for the diatribe. At 81, I've seen and heard a lot that would very likely leave you aghast. You may find my website interesting. It's in my profile but this is easier. It's the loudspeaker main index that'll bypass the other audio paraphernalia there. https://www.ln271828.net/p3.htm
Robert
Now, if the 1.7 ft^3 enclosure was not adjusted for that, we'd end up with an internal volume of 1.6 ft^3, the yellow trace in the graphs below.
If you went to 2 ft^3 and didn't account for speaker and cleat displacement, we'd have 1.899ft^3, the blue/green trace.
The red trace is the exact internal volume of 1.7 ft^3 after all volume displacing components have been accounted for.
Volume displacing components not only includes the speakers but also any internal bracing, cleats and as you mentioned, the plate amplifier. Judging by the traces below, you're right about just going with an internal volume of 2 ft^3 with no concern for displacement by internal components. The end result will be close to any of these traces.
In the graphs below, NA is normalized amplitude response, expressed in dB relative to the peak.
CA is custom amplitude response, expressed in Db SPL as a function of power, which can be changed.
AP is the acoustical output as a function of maximum power applied, expressed in dB at 1 meter.
EP is the maximum electrical input power the speaker can handle within its Xmax. It's expressed in watts as a function of frequency. At 40hz, the woofers can handle 16 watts. Any more will overdrive the speakers.
CD is cone displacement.
VV is vent air velocity, not applicable here.
I is system impedance, Z, applies to the 4 woofers only.
P is phase response, expressed in degrees.
GD is group delay, which is phase response expressed in milli seconds.
If you want the rest of the graphs, just ask.
As can be seen, slight closed box internal volume variations of as much as 20%, 1.6ft^3 to 2.0ft^3 are insignificant, at least for these speakers. If memory serves me well, such a volume variation in a vented box is not as forgiving.
Some noted data.
1.6ft^3 f3=62hz, Xmax reached at 50hz, peak impedance=21.7 ohms at 63hz
1.7ft^3 f3=62hz, Xmax reached at 52hz, peak impedance=22 ohms at 62hz
2.0ft^3 f3=61hz, Xmax reached at 54hz, peak impedance=22.3 ohms at 59hz.
What this shows that as a sealed box volume is increased, f3 may get lower but the caveat is that Xmax is reached sooner. Some will make a sealed box larger to get lower bass using a bass boost giving no thought to what's happening to Xmax.
I have 4 of those DC200-8 units and a pair of test enclosures of 3ft^3 each. They can be filled to 2ft^3 and a new front baffle added. I also have test equipment like LMS and CLIO and can run near field responses to get a better idea of how these things perform. Judging by the BBP traces, one speaker in 0.43ft^3 will perform the same as 4 in 1.7ft^3 with exception of the power handling capacity.
My apologies for the diatribe. At 81, I've seen and heard a lot that would very likely leave you aghast. You may find my website interesting. It's in my profile but this is easier. It's the loudspeaker main index that'll bypass the other audio paraphernalia there. https://www.ln271828.net/p3.htm
Robert
Awesome. Thanks for the help. I appreciate it given I'm a novice at speaker building.
I did get fairly decent low bass, but that was when the l-pads for the midrange and tweeter were adjusted wrong and made them lower in output and the one was used for years like that. Perhaps that's why I thought these had good low bass.
I do have a zobel network on the woofers so that will tame the impedance peak, right?
Question is do I use a plate amp or do I use an external amplifier?
Last time I used these I used a Carver TFM-25 amp which did great.
I did get fairly decent low bass, but that was when the l-pads for the midrange and tweeter were adjusted wrong and made them lower in output and the one was used for years like that. Perhaps that's why I thought these had good low bass.
I do have a zobel network on the woofers so that will tame the impedance peak, right?
Question is do I use a plate amp or do I use an external amplifier?
Last time I used these I used a Carver TFM-25 amp which did great.
OMG. I've heard of that Carver Magnetic Field amplifier but have not seen or heard one or even knew anyone who did. If that thing is working and if you don't already have a plate amp, then use the Carver. Why spend money on something you don't need, unless, of course, you just have to have a new toy.
That I understand as I've been down that road many times. Heck, I've got 9 Revox A77's that I restored and they have new heads. There's tqwo Teac X1000 recorders and 3 Akai's and several portable recorders that date to the sixties. This place is a museum.
How did you figure the zobels and measure the result? Yes, a zobel will tame the impedance peak. They were invented at Bell Labs by a fella named Zobel way back in the early 20's
I've used them years ago, mostly out of curiosity. Most use them today to tame the rising impedance of a midrange unit, which may be 8 ohms at 500hz but can be as high as 20 ohms at 4khz. If designing a crossover for a 3-way and assuming the impedance to be 8 ohms at the upper end, the upper crossover point will more than double.
That I understand as I've been down that road many times. Heck, I've got 9 Revox A77's that I restored and they have new heads. There's tqwo Teac X1000 recorders and 3 Akai's and several portable recorders that date to the sixties. This place is a museum.
How did you figure the zobels and measure the result? Yes, a zobel will tame the impedance peak. They were invented at Bell Labs by a fella named Zobel way back in the early 20's
I've used them years ago, mostly out of curiosity. Most use them today to tame the rising impedance of a midrange unit, which may be 8 ohms at 500hz but can be as high as 20 ohms at 4khz. If designing a crossover for a 3-way and assuming the impedance to be 8 ohms at the upper end, the upper crossover point will more than double.
I used an online calculator for the zobel.
For the series/parallel connected woofers I used an 8 ohm resistor and 10uF cap.
For the midrange I used a 9.5 ohm resistor and 25uF cap I believe.
I measured the result with my ears as back then I had no real audio measurement tools.
I do have a Dayton Audio DATS V3 speaker tester. I mostly use it when making inductors. I'll start with one higher than what I need and unwind until the DATS reads the desired value.
EDIT:
Here's the l-pad and zobel schematic.
Here's how the drivers are arranged in the cabinet.
For the series/parallel connected woofers I used an 8 ohm resistor and 10uF cap.
For the midrange I used a 9.5 ohm resistor and 25uF cap I believe.
I measured the result with my ears as back then I had no real audio measurement tools.
I do have a Dayton Audio DATS V3 speaker tester. I mostly use it when making inductors. I'll start with one higher than what I need and unwind until the DATS reads the desired value.
EDIT:
Here's the l-pad and zobel schematic.
Here's how the drivers are arranged in the cabinet.
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That's not Zobel compensation, it only deals with the rise in impedance at higher frequencies, not the peak.
Dealing with the rise in impedance at higher frequencies is zobel compensation.
How does one deal with the peak?
How does one deal with the peak?
Oh ok. There any calculators for that?
So I'd still need the zobel along with the RCL, right?
How important is it to deal with the impedance peak?
So I'd still need the zobel along with the RCL, right?
How important is it to deal with the impedance peak?
The following is from Vance Dickason's Loudspeaker Cookbook. Please excuse the crudity of the drawing. I took a photo instead of a scan which would have required me to fire up two other computers. I'll send a more legible one later.
The TS params in use are Fs=30.3 (59)hz; Re=6.41ohms; Qes=0.49; Qms=3.06
The number 59 in () is the resonance of the speaker in a 0.428 sealed box. It is the same as the four speakers in a 1.7 ft^3 box. The equations state Fs which is in open air but sometimes it may refer to the actual fs of the driver in the box, which makes more sense to me but I'm not an EE.
What you have in the woofer section is an impedance equalizer. It actually should be used in the Pyle. Most cone midrange speakers will have an impedance that rises with frequency. It may be 8 ohms at 500hz bit can be twice that or higher at 4khz. If 8 ohms is assumed at 4khz, the actual crossover point will be around 8khz or higher. That circuit will tame the rising impedance. I've used it a few times. If you poke around enough into my loudspeakers index, you might stumble on it.
AllenB got it right. The series RCL is the zobel and is wired in parallel with the speakers as per the above schematic.
Your DATS will measure impedance. To see if your zobel works, run a Z check on the four speakers in the box with the 4 Daytons disconnected from the crossover. If you see a hump around 60hz, the zobel is incorrect.
The values calculated from the equations above coincide with those stated by Mr. Dickason about the extremely high inductor and capacitor values, which are 16.7mh and 1689uF, resp. I should have enough components to cook up these values and check out the zobels calculated at 30hz and 60hz. If not, I'll visit Parts Express.
You wouldn't believe the stuff I have accumulated over the last 47 years. I'm a pak-rat on steroids.
The TS params in use are Fs=30.3 (59)hz; Re=6.41ohms; Qes=0.49; Qms=3.06
The number 59 in () is the resonance of the speaker in a 0.428 sealed box. It is the same as the four speakers in a 1.7 ft^3 box. The equations state Fs which is in open air but sometimes it may refer to the actual fs of the driver in the box, which makes more sense to me but I'm not an EE.
What you have in the woofer section is an impedance equalizer. It actually should be used in the Pyle. Most cone midrange speakers will have an impedance that rises with frequency. It may be 8 ohms at 500hz bit can be twice that or higher at 4khz. If 8 ohms is assumed at 4khz, the actual crossover point will be around 8khz or higher. That circuit will tame the rising impedance. I've used it a few times. If you poke around enough into my loudspeakers index, you might stumble on it.
AllenB got it right. The series RCL is the zobel and is wired in parallel with the speakers as per the above schematic.
Your DATS will measure impedance. To see if your zobel works, run a Z check on the four speakers in the box with the 4 Daytons disconnected from the crossover. If you see a hump around 60hz, the zobel is incorrect.
The values calculated from the equations above coincide with those stated by Mr. Dickason about the extremely high inductor and capacitor values, which are 16.7mh and 1689uF, resp. I should have enough components to cook up these values and check out the zobels calculated at 30hz and 60hz. If not, I'll visit Parts Express.
You wouldn't believe the stuff I have accumulated over the last 47 years. I'm a pak-rat on steroids.
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The subscripts should be more legible. Yes. NP caps are much preferred but you don't need the exotic ones. Plain old non-polarized caps available at Parts Express are adequate.
Oh ok.
I was expecting them to be expensive, but a 500uF non-polar cap from Parts Express is only $9.00
What would be the harm in leaving that RCL network out?
I was expecting them to be expensive, but a 500uF non-polar cap from Parts Express is only $9.00
What would be the harm in leaving that RCL network out?
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If the crossover point between the woofers and the midrange is above 300hz, the impedance peak at 60hz will have no effect on the crossover. In all the systems I've designed over the last 40 plus years, I've never used a zobel to tame a woofer's impedance peak. It's tantamount to removing an obstruction on the road when you can simply drive around it, assuming, of course, you have that option.
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