OK there is a huge back story on these, but it explains what, why, etc.. At the end is the assumption I'm making about what a solution could be.
I had a friend help me build these in the early 1980s. I used to work at a Pioneer factory service center repairing VCRs and rebuilding optical platforms for laserdisc players there. The benefit was that I could get parts at cost. The crossover and drivers were previously all from Pioneer HPM-150 acoustic suspension (sealed) speaker systems, except the dome tweeters.
Those original excellent Pioneer 15" woofers were destroyed in an 'accident' with DC coupled Ling TP-850 amplifiers and replaced in the 1990s the Eminence woofers shown, which were the closest parts I could find/afford at the time. They aren't right for my cabinet but neither were the Pioneer woofers, though those were a slightly better match.
The two 5" square-frame mids shown are from the HPM-150 parts list, but it used only one. The crossover is the HPM-150 unit, and those mids are parellelled on the mid output, which is wrong but it works. The dome is on the crossover's tweeter output, and the small cone tweeter, from the HPM-150, is on the omnidirectional tweeter output, before the impedance transformer (as the omni tweeter was a strange, expensive device and I did not have them).
All has been well but I have been so busy with life and career. For the last 20 years the speakers and most of the old stereo stuff has been sitting unused in a room used for storage. Now I approach retirement and with time on-hand comiong soon, I want to get a few things done, and getting the best from those speakers and getting them back in service is high on the list. It's more like 'finishing the design' than anything else, since they have always had an issue with the low bass.
The main issue in my sealed cabinet is that the woofers seem to be 'unloaded' at low frequencies from about 35Hz down. This was untrue of the old Pioneer HPM-150 speaker systems which were rated to 25Hz.
I would demonstrate the HPM-150s down to an abusive 15.4Hz with the 1970 album "Five Improvisations on Magnetic Tape" by Oskar Sala, which specifically brags about that frequency and the album's ability to blow speakers on the reverse of the cover. (This vinyl can be had for very cheap now "Westminster Gold WGS-8110" on discogs.com, if anyone else wants to torture their woofers and anyone within earshot.)
Unfortunately, the HPM-150 woofers put in my larger cabinets, and the Eminence woofers after them, are what I can only call "unloaded" below about 35Hz, because the cones have way excessive excursion -the air volume seems too large/soft -not enough spring -for that one woofer.
I'm being very general here because I'm not a speaker expert, just a hobbyist. When those speakers were built 30 years ago neither of us knew anything about it except that bigger is better for bass, but the guy was a good cabinet maker. As far as audio, I'm a repair and tube amp guy mainly.
I'm tempted to see it this way:
That make any sense?
=========================================
About things mentioned:
Pioneer HPM-150 info/manual:
Pioneer HPM 150 (HPM 1500) Speaker Review, Specs and Price |Vintage Speaker Reviews, Specs, Prices, Repairs, Refoaming, Reconing
Ling TP-850 manual
http://69.36.164.11/lit/ling_TP850.pdf
Dynaco Stereo-120 info/manual:
Dynaco Stereo 120 - Manual - Stereo Power Amplifier - HiFi Engine
Stromberg-Carlson AP-80 schematic:
The Official Shrine of the Stromberg-Carlson AP80 Power Amplifier
=======================================
I had a friend help me build these in the early 1980s. I used to work at a Pioneer factory service center repairing VCRs and rebuilding optical platforms for laserdisc players there. The benefit was that I could get parts at cost. The crossover and drivers were previously all from Pioneer HPM-150 acoustic suspension (sealed) speaker systems, except the dome tweeters.
Those original excellent Pioneer 15" woofers were destroyed in an 'accident' with DC coupled Ling TP-850 amplifiers and replaced in the 1990s the Eminence woofers shown, which were the closest parts I could find/afford at the time. They aren't right for my cabinet but neither were the Pioneer woofers, though those were a slightly better match.
The two 5" square-frame mids shown are from the HPM-150 parts list, but it used only one. The crossover is the HPM-150 unit, and those mids are parellelled on the mid output, which is wrong but it works. The dome is on the crossover's tweeter output, and the small cone tweeter, from the HPM-150, is on the omnidirectional tweeter output, before the impedance transformer (as the omni tweeter was a strange, expensive device and I did not have them).
All has been well but I have been so busy with life and career. For the last 20 years the speakers and most of the old stereo stuff has been sitting unused in a room used for storage. Now I approach retirement and with time on-hand comiong soon, I want to get a few things done, and getting the best from those speakers and getting them back in service is high on the list. It's more like 'finishing the design' than anything else, since they have always had an issue with the low bass.
The main issue in my sealed cabinet is that the woofers seem to be 'unloaded' at low frequencies from about 35Hz down. This was untrue of the old Pioneer HPM-150 speaker systems which were rated to 25Hz.
I would demonstrate the HPM-150s down to an abusive 15.4Hz with the 1970 album "Five Improvisations on Magnetic Tape" by Oskar Sala, which specifically brags about that frequency and the album's ability to blow speakers on the reverse of the cover. (This vinyl can be had for very cheap now "Westminster Gold WGS-8110" on discogs.com, if anyone else wants to torture their woofers and anyone within earshot.)
Unfortunately, the HPM-150 woofers put in my larger cabinets, and the Eminence woofers after them, are what I can only call "unloaded" below about 35Hz, because the cones have way excessive excursion -the air volume seems too large/soft -not enough spring -for that one woofer.
I'm being very general here because I'm not a speaker expert, just a hobbyist. When those speakers were built 30 years ago neither of us knew anything about it except that bigger is better for bass, but the guy was a good cabinet maker. As far as audio, I'm a repair and tube amp guy mainly.
I'm tempted to see it this way:
- The Pioneer HPM-150s had a volume of 166 liters / 5.8 cu FT and one 15" acoustic suspension woofer.
- My cabinets have a volume of 253 liters / 10 cu FT. There is one 15" acoustic suspension woofer. I should use two woofers since the volume is twice as much. Could put one on the back.
That make any sense?
=========================================
About things mentioned:
Pioneer HPM-150 info/manual:
Pioneer HPM 150 (HPM 1500) Speaker Review, Specs and Price |Vintage Speaker Reviews, Specs, Prices, Repairs, Refoaming, Reconing
Ling TP-850 manual
http://69.36.164.11/lit/ling_TP850.pdf
Dynaco Stereo-120 info/manual:
Dynaco Stereo 120 - Manual - Stereo Power Amplifier - HiFi Engine
Stromberg-Carlson AP-80 schematic:
The Official Shrine of the Stromberg-Carlson AP80 Power Amplifier
=======================================
Attachments
Do you have a pair of those monsters? You could do a lot better with more modern drivers and fewer of them but if the boxes are well made and you want to use them are they well braced side to side and front to back? Do you have a budget? Big woofers tend to cost fairly big dollars
Test or identify the woofer. Then we'll know what kind of box it wants.
In the meantime, try a bag of sand in there to reduce volume & see how it does.
Is the box stuffed at all?
In the meantime, try a bag of sand in there to reduce volume & see how it does.
Is the box stuffed at all?
Thak you folks for replying with help on this.
I do have a pair of the beasts. The high density particle board is the kind made for speakers, and although it looks a little dirty they are in good shape.
It has a brace from front to back above the woofer. The wood is 3/4" thick everywhere. The mids and tweeters and controls are in their own sealed inner box. That gives quite a bit of bracing there at the top front.
I am on a tight budget so if the present speakers can be used and solve the issue, that would be best. I've seen some of the low Fs 15" speakers on the speaker selection site and they are quite expensive.
I will have to remove the woofer from the accessible speaker cabinet to try and identify it. Hopefully the model or part number is on the back of the speaker. If not, I will need guidance on testing. Let me get it out first and go from there.
The box is not stuffed, but has some insulation on three sides internally, if I recall, as it was long ago when they were made. I can supply the info soon as I can get to it and pull the woofer.
Patrick
I do have a pair of the beasts. The high density particle board is the kind made for speakers, and although it looks a little dirty they are in good shape.
It has a brace from front to back above the woofer. The wood is 3/4" thick everywhere. The mids and tweeters and controls are in their own sealed inner box. That gives quite a bit of bracing there at the top front.
I am on a tight budget so if the present speakers can be used and solve the issue, that would be best. I've seen some of the low Fs 15" speakers on the speaker selection site and they are quite expensive.
I will have to remove the woofer from the accessible speaker cabinet to try and identify it. Hopefully the model or part number is on the back of the speaker. If not, I will need guidance on testing. Let me get it out first and go from there.
The box is not stuffed, but has some insulation on three sides internally, if I recall, as it was long ago when they were made. I can supply the info soon as I can get to it and pull the woofer.
Patrick
The Trautonium can produce some low frequencies for sure! The music on this particular record is a bit edgy, but Oskar Sala has some very beautiful compositions on other albums. My favourite is his series of Caprices.
He was a happy old man, i am glad he got the recognition he deserved in his old age.
He was a happy old man, i am glad he got the recognition he deserved in his old age.
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This will be best approached by measuring impedance and then have the software calculate the TS parameters. Prepare the weights for "delta mass" method, like 4 weights, each 25g equally spread around the dustcap. Some use blue tack, others rubber blocks or whatever works. It is important that these are accurately measured for their weight. Search for ARTAlabs measurement suite and the LIMP module is meant for impedance evaluation.
I fancy this kind of vintage junk for people mostly trash it and that translates into good find. The potential for solid sound is there, and as usual it is the implementation that will make all the difference, presuming drivers overlap in their FR in such a way that it is still managable to work out a filter. The impedance measurement jig.
I fancy this kind of vintage junk for people mostly trash it and that translates into good find. The potential for solid sound is there, and as usual it is the implementation that will make all the difference, presuming drivers overlap in their FR in such a way that it is still managable to work out a filter. The impedance measurement jig.
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Thanks to Bill McFadden's Home Page, there is a "List of Low Frequency Loudspeaker Drivers 12-May-99" and these woofers are on it.
~~~
Manufacturer_________MCM
Model________________55-785
Dia._________________15 inches
Power RMS____________100 W
Z Ohms_______________8
SPL 1W/1m____________93 dB
Vas cu ft____________31.13
Fs___________________18 Hz
Qts__________________0.35
xmax_________________ not specified
~~~
So, these seem to be a product made in 1993 for MCM Electronics. There is a date code on them. I'd forgotten the Fs of 18Hz - no doubt why I picked them. Said I didn't know much about speakers!
Xmax not specified- I have seen these move maybe 0.25 inch each direction without bottoming, no idea about linearity at that point but likely pushing things pretty far.
That's all the info I have on these. The speaker test on these woofers may not be worthwhile because the surrounds are about to go (small hole) and the 100W power rating is pretty small for what I'd like to do. 8 Ohms is also too high, want lower Z to make better use of the Ling 1 Ohm shaker amplifiers. Modern speakers give lots of better choices I can see now after looking at a few. I have no objection to 'house brand' stuff but it's time to move beyond the lowest budget performance. I might be able to go $200-300 each, but let that be stated with the caveat that I'm much more influenced by performance now than 20-30 years ago, and willing to save up $ and wait.
The cabinet is not totally stuffed but has quite a bit of insulation. Hmm. I think it's from my old friend the Pink Panther. The front to back brace is a 2x4. No side-to-side brace, but one could be added in there, a lot of trouble but do-able. There is a 1x1" cleat in each corner, running top to bottom. The cabinet can not be disassembled, that is 100% certain. What about the wofer attachment screws? The mounting holes seem OK, but I'd like to improve that situation, but no idea what hardware is appropriate. I have noticed that a lot of 'professional hi-fi' speakers have machine screws.
pictures worth 1000 words..
~~~
Manufacturer_________MCM
Model________________55-785
Dia._________________15 inches
Power RMS____________100 W
Z Ohms_______________8
SPL 1W/1m____________93 dB
Vas cu ft____________31.13
Fs___________________18 Hz
Qts__________________0.35
xmax_________________ not specified
~~~
So, these seem to be a product made in 1993 for MCM Electronics. There is a date code on them. I'd forgotten the Fs of 18Hz - no doubt why I picked them. Said I didn't know much about speakers!
Xmax not specified- I have seen these move maybe 0.25 inch each direction without bottoming, no idea about linearity at that point but likely pushing things pretty far.
That's all the info I have on these. The speaker test on these woofers may not be worthwhile because the surrounds are about to go (small hole) and the 100W power rating is pretty small for what I'd like to do. 8 Ohms is also too high, want lower Z to make better use of the Ling 1 Ohm shaker amplifiers. Modern speakers give lots of better choices I can see now after looking at a few. I have no objection to 'house brand' stuff but it's time to move beyond the lowest budget performance. I might be able to go $200-300 each, but let that be stated with the caveat that I'm much more influenced by performance now than 20-30 years ago, and willing to save up $ and wait.
The cabinet is not totally stuffed but has quite a bit of insulation. Hmm. I think it's from my old friend the Pink Panther. The front to back brace is a 2x4. No side-to-side brace, but one could be added in there, a lot of trouble but do-able. There is a 1x1" cleat in each corner, running top to bottom. The cabinet can not be disassembled, that is 100% certain. What about the wofer attachment screws? The mounting holes seem OK, but I'd like to improve that situation, but no idea what hardware is appropriate. I have noticed that a lot of 'professional hi-fi' speakers have machine screws.
pictures worth 1000 words..
Attachments
Cool! 'Blast from the Past! Totally forgotten about his page and surprised it's still up.
OK, 10 ft^3 with these specs is a T/S max flat [~0.71 Qtc] sealed alignment, so did something right! As such, shouldn't need much stuffing, just enough to remove any 'hollow' sound when the cab is struck with a wooden hammer handle or similar.
Much too small for vented, but if wanting to try it, a 4" dia. x 7.5" long pipe tunes it to ~ 18 Hz or you can cut it long and shorten as required to get it exact or even higher. May want to just try a 4" diameter hole = ~30 Hz Fb.
Note this is much too small a vent for high power, but will work at low power to decide whether you want go vented.
I use T nuts, but a lot of folks have issues because they don't seat them properly, especially in particleboard, though threaded inserts is a good way [both use machine screws]. The main thing is just wood screws isn't a good plan for woofers, except at very low power
GM
OK, 10 ft^3 with these specs is a T/S max flat [~0.71 Qtc] sealed alignment, so did something right! As such, shouldn't need much stuffing, just enough to remove any 'hollow' sound when the cab is struck with a wooden hammer handle or similar.
Much too small for vented, but if wanting to try it, a 4" dia. x 7.5" long pipe tunes it to ~ 18 Hz or you can cut it long and shorten as required to get it exact or even higher. May want to just try a 4" diameter hole = ~30 Hz Fb.
Note this is much too small a vent for high power, but will work at low power to decide whether you want go vented.
I use T nuts, but a lot of folks have issues because they don't seat them properly, especially in particleboard, though threaded inserts is a good way [both use machine screws]. The main thing is just wood screws isn't a good plan for woofers, except at very low power
GM
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All the loudspeakers should line on vertical axis! How can a speaker sound right when this basic rule isn't observed?
That's (also...) a reason because g-normous woofers don't work at home, CTC distance becomes too high
That's (also...) a reason because g-normous woofers don't work at home, CTC distance becomes too high
At an XO of 300Hz the C2C can be up to a metre I see no problem with woofers only 400mm in diametre
And where do you put two woofers of 400 mm diameter in a room?
For continuity, you'd like two 200 mm midrange, right ?
What about vertical alignment of the drivers, does that suit you ?
Or do you find "no problems" if they are stacked horizontally and "casual" ?
For continuity, you'd like two 200 mm midrange, right ?
What about vertical alignment of the drivers, does that suit you ?
Or do you find "no problems" if they are stacked horizontally and "casual" ?
Close to the floor for the woofers and a single 6" midbass or 2*4" midrange.
Of course I know some European/British house have rooms too small to fit in speaker boxes this large but there are many houses here in Australia and very very many in North America that would have a large room suitable for such systems. Opposing woofers on the sides of large boxes also work. I have always found that a large woofer moving a short distance preferable to listen to [ more natural if you will] than smaller woofer moving a large distance.
My compromise has for a long time been dual 12" woofers if I can. Finances and WAF often mean larger compromises and much smaller woofers plus a compact sub or 3. I have never been a fan of small 2-Way speakers, even the best iterations seem somehow lacking in definition and midrange clarity compared to a good 3-Way
Of course I know some European/British house have rooms too small to fit in speaker boxes this large but there are many houses here in Australia and very very many in North America that would have a large room suitable for such systems. Opposing woofers on the sides of large boxes also work. I have always found that a large woofer moving a short distance preferable to listen to [ more natural if you will] than smaller woofer moving a large distance.
My compromise has for a long time been dual 12" woofers if I can. Finances and WAF often mean larger compromises and much smaller woofers plus a compact sub or 3. I have never been a fan of small 2-Way speakers, even the best iterations seem somehow lacking in definition and midrange clarity compared to a good 3-Way
Pages like that need to be kept linked - so much great info on the older personal sites.
There's no hollow sound at all when knocking on the speaker cabinet.
I was getting tuned port data from a book, for 20Hz/10 cu ft, so to compare the length for 18Hz:
18Hz___12.567 sq in.,___7.50" long___(4" dia. pipe)
20Hz___14.000 sq in.,___6.375" long___(3.75" square pipe)
I need a program for this, just the simplest kind to get me started leanring more about it.
Why do you say that this is much too small a vent for high power? I don't understand completely - is this statement for a 4" hole or for a 4" pipe 7.5" long?
Is it for reasons of disagreeable noises from the port?
Called chuffing and it can be disturbing
GM posted a link in another post that advised the port diametre to be driver size / 3 so a 4" or 6" port for a 15" woofer, as the port gets bigger it needs to be longer tho but in a box that size I see no problem
Assuming you keep that box.
GM posted a link in another post that advised the port diametre to be driver size / 3 so a 4" or 6" port for a 15" woofer, as the port gets bigger it needs to be longer tho but in a box that size I see no problem
Assuming you keep that box.
Hmm, 15" = ~128"2/3 = ~42.67"^2
[~42.67*4/pi]^0.5 = ~7.37" dia. pipe = [4] 4" dia.[ i.d.] traditionally or if just modest power, dual dual 5" [i.d.].
GM
[~42.67*4/pi]^0.5 = ~7.37" dia. pipe = [4] 4" dia.[ i.d.] traditionally or if just modest power, dual dual 5" [i.d.].
GM
Agreed, there's a bunch of good ones that's long gone.
Good book since it matches Hornresp. 😉
If you can run a DOS program there's some super simple programs still downloadable last time I checked. I used Boxplot, Bullock's & White's for many years and earlier an HP hand held calculator program published in the AES. The only modern day 'simple' programs are only on-line AFAIK. A good DIY site: HiFi Loudspeaker Design
True of either one and the better programs can sim this, but in general we want vent mach < ~17 m/s [~55.77 ft/s].
GM
Good book since it matches Hornresp. 😉
If you can run a DOS program there's some super simple programs still downloadable last time I checked. I used Boxplot, Bullock's & White's for many years and earlier an HP hand held calculator program published in the AES. The only modern day 'simple' programs are only on-line AFAIK. A good DIY site: HiFi Loudspeaker Design
True of either one and the better programs can sim this, but in general we want vent mach < ~17 m/s [~55.77 ft/s].
GM
That book with the 20Hz figure, believe it or not is Radio Shack "Building Speaker Enclosures" 2nd edition 1984, cat no. 62-2309. It's actually a rebranded TAB book by David Weems.
I'm keeping the box. I don't mind a big port, or 2, or whatever is needed.
GM mentioned a 4" pipe, or dual 5" pipes. What happens when two identical pipes are used? In electricity, two capacitors or inductors in parallel have a definite effect over one part.
I don't know what is meant by modest power. Acoustic or electrical? I think the 15" in there was doing all it could, but would benefit by a port to tune the box. It's done for now, new drivers have to be bought.
I am limited by piston size and excursion. The only way to increase that product is a longer throw speaker or a bigger one. Or two 15 inchers, seems once you get above 15" they get really expensive.
But I have 2x 850W amps to drive the woofers, so.. is that modest power these days? It used to be high power.
I had used winISD before, but it won't run right on this computer, won't save files or edit the database. etc.
Going to look at HiFi Loudspeaker Design site now.
----------
There's an old book that seems useful when thinking abour cone size and excursion and acoustic power.
"Acoustic Design Charts" by Frank Massa 1942. It's on archive.org.
It shows peak excursions needed for certain acoustic wattages and sound pressures. It does give Watts (chart 61), but where sound pressure is concerned it gives "dynes/cm^2 * distance in feet" (chart 62), so where the usual SPL at 1M is concerned the book's units have to be converted to dB. dB in sound is not easily converted to power unless a reference value is used. The accepted reference is 20uPa (20 micropascals).
There is an online calculator that does this:
Convert dyne/square centimeter [dyn/sq. cm] <—> sound pressure level in decibels [dB SPL] • Acoustics — Sound • Sound Pressure Level (SPL) Converter • Compact Calculator
chart 61:
0.15 inches peak (not p-p) excursion of a 15" piston at 20Hz gives 0.01W acoustic power.
chart 62:
0.15 inches peak (not p-p) excursion of a 15" piston at 20Hz gives 10 dynes/cm^2 at 3 FT (close enough to a meter here). The 10 dynes/cm^2 at the same 3 ft is 94dB SPL.
so much for the sensitivity on that Eminense/MCM speaker being 93dB@1M @1W. Or there could be a decimal off somewhere in my work or even the online calc since dynes/cm^2 conversion to dB SPL requires a reference level based on human hearing.
I'm keeping the box. I don't mind a big port, or 2, or whatever is needed.
GM mentioned a 4" pipe, or dual 5" pipes. What happens when two identical pipes are used? In electricity, two capacitors or inductors in parallel have a definite effect over one part.
I don't know what is meant by modest power. Acoustic or electrical? I think the 15" in there was doing all it could, but would benefit by a port to tune the box. It's done for now, new drivers have to be bought.
I am limited by piston size and excursion. The only way to increase that product is a longer throw speaker or a bigger one. Or two 15 inchers, seems once you get above 15" they get really expensive.
But I have 2x 850W amps to drive the woofers, so.. is that modest power these days? It used to be high power.
I had used winISD before, but it won't run right on this computer, won't save files or edit the database. etc.
Going to look at HiFi Loudspeaker Design site now.
----------
There's an old book that seems useful when thinking abour cone size and excursion and acoustic power.
"Acoustic Design Charts" by Frank Massa 1942. It's on archive.org.
It shows peak excursions needed for certain acoustic wattages and sound pressures. It does give Watts (chart 61), but where sound pressure is concerned it gives "dynes/cm^2 * distance in feet" (chart 62), so where the usual SPL at 1M is concerned the book's units have to be converted to dB. dB in sound is not easily converted to power unless a reference value is used. The accepted reference is 20uPa (20 micropascals).
There is an online calculator that does this:
Convert dyne/square centimeter [dyn/sq. cm] <—> sound pressure level in decibels [dB SPL] • Acoustics — Sound • Sound Pressure Level (SPL) Converter • Compact Calculator
chart 61:
0.15 inches peak (not p-p) excursion of a 15" piston at 20Hz gives 0.01W acoustic power.
chart 62:
0.15 inches peak (not p-p) excursion of a 15" piston at 20Hz gives 10 dynes/cm^2 at 3 FT (close enough to a meter here). The 10 dynes/cm^2 at the same 3 ft is 94dB SPL.
so much for the sensitivity on that Eminense/MCM speaker being 93dB@1M @1W. Or there could be a decimal off somewhere in my work or even the online calc since dynes/cm^2 conversion to dB SPL requires a reference level based on human hearing.
I learned about multiple ports - -they are like an inductor, put them in parallel and the value (length) goes down.
Here's the room, which I am willing to reconfigure but there are limits. It's a modest home in Dallas.
The place is pier and beam foundation - so the poor old AT-PL120 turntable will suffer some vibration, though its weight has served it well before
Here's a WinISD project using the Cerwin Vega 15" sub -it has two 2-Ohm coils and Fs 19Hz, Xmax 24mm. There is a port, 5", tuned as shown.
Here's the room, which I am willing to reconfigure but there are limits. It's a modest home in Dallas.
The place is pier and beam foundation - so the poor old AT-PL120 turntable will suffer some vibration, though its weight has served it well before
Here's a WinISD project using the Cerwin Vega 15" sub -it has two 2-Ohm coils and Fs 19Hz, Xmax 24mm. There is a port, 5", tuned as shown.
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