I just saw these drivers on MCM for $10. It has good efficiency and decent xmax of 3.5mm but fs is high at 65 Hz and Qts is very low (almost unbelievable for such a cheap driver). At this price it may be worth an experiment and with enough of them can be EQ'd to produce bass down low.
MCM Audio Select 8" Woofer with Paper Cone and Cloth Surround - 100W RMS at 8ohm | 55-2950 (552950) | MCM Audio Select
Does anyone have experience with this one?
MCM Audio Select 8" Woofer with Paper Cone and Cloth Surround - 100W RMS at 8ohm | 55-2950 (552950) | MCM Audio Select
Does anyone have experience with this one?
If you model it and it appears to work well, I'll try it.
I have reached out to others who (I believe) have experience with MCM drivers generally, and we will find out if they know anything first hand about these 8"-ers.
OB wise, I am "dumber than a fence post", but I would be happy to move off of that as a starting point.
First go at something like this - heck, what to I have to loose at the price of two MCM 8" and two Vifas (which I already have)?
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I will sim the MCM's as soon as I get a chance but you will need at least 4 per side or 8 total to get enough air moving for bass from an OB. We will see what the sims say. Maybe get 4 at first for one side and if it works get more? Shipping will get you for breaking it up. I think the bigger question to ask if these drivers really measure to have a Qts in the 0.2 range? I doubt it as drivers with a Qts that low usually are pro audio drivers in the $80 range.
Slot OB with MCM 55-2950 driver
That $10 MCM 8inch woofer is not the best driver for this application as the low Qts makes the bass start to roll of pretty high up. However, it is very efficient and can make some serious mid bass if you have a dedicated sub woofer. It can be EQ'd to provide about 90 dB at 60 Hz - this is xmax limited. The peak at 200 Hz can easily be EQ'd out with the DSP.
Here is a sim for a 4 driver slot baffle woofer with driver box 5 in wide x 10 in deep x 20 in high with 1.75 in wide slot (no lip).
Plots: SPL vs Freq at max drive voltage of 22 volts rms, cone displacement at 22 volts rms corresponding to xmax.
That $10 MCM 8inch woofer is not the best driver for this application as the low Qts makes the bass start to roll of pretty high up. However, it is very efficient and can make some serious mid bass if you have a dedicated sub woofer. It can be EQ'd to provide about 90 dB at 60 Hz - this is xmax limited. The peak at 200 Hz can easily be EQ'd out with the DSP.
Here is a sim for a 4 driver slot baffle woofer with driver box 5 in wide x 10 in deep x 20 in high with 1.75 in wide slot (no lip).
Plots: SPL vs Freq at max drive voltage of 22 volts rms, cone displacement at 22 volts rms corresponding to xmax.
Attachments
Slot Loaded Woofer OB
I found some high quality double wall cardboard from a piano packing box. Too good to pass up without repurposing it to something useful, still related to music...
The design is similar to my sims for the 6.5 in PE buyout polycone woofer with a 12 in wide baffle. The slot loaded chamber was made from three of the boxes that the drivers came in and provided a 7 in deep x 7 in tall x 3 in wide chamber times three. The slots are 1.75 in wide x 6 in tall times three. The OB has 7.25 in deep wings that go up 22 in high and then angle in towards the baffle. The drivers are mounted asymmetrically to reduce hysteresis-induced distortion with one side having the basket inside the chamber. The Vifa fullrange is mounted 5 in from the top and 4.5 in from the side. The woofers are wired 3-series-2-parallel for a nominal 6 ohm load. The speaker is bi-amplified and the XO and EQ are performed with a miniDSP. The measurement was made with the speaker on the floor angled 45 deg from the walls with the mic 1.0 meter away at the same height at the Vifa driver.
Here are the results, and I think they turned out pretty nice. REW auto-generated bi-quad EQ's were used just for the woofer, and the Vifa's only had a boost from 17 kHz on up. I left the EQ on the fullrange as minimalist as possible to prevent mucking with the phase in the 500 Hz to 5kHz band. The XO was set at 210 Hz as -24dB/oct Butterworth on both the LPF and HPF.
Woofer (PE part no. 299-609, 4 ohm) SPL vs Freq:
Fullrange (Vifa TC9FD) SPL vs Freq:
System SPL vs Freq -3dB point is about 44 Hz on low end and above 20 kHz on high end:
Distortion - having 6 drivers really helped to bring the distortion low at about -30dB at 40 Hz (0.1% THD) - the cones barely move with normal music program levels. The distortion of the fullrange Vifa, is as usual, just excellent at circa -45dB to -50dB:
Impulse Response - very clean - indicating detailed crisp dynamics that should be possible:
I only had enough drivers to build one at this time so no stereo - but from what I can hear, it sounds very nice. I tested it with the Nautaloss set up as the left channel and the imaging and soundstage was superb. I played some jazz, female vocals, Baroque string quartet, classic rock, pop, it all sounded great. I think the fact that the response is flat and balanced makes it sound good with whatever you throw at it. This speaker was built completely out of cardboard - no foam core used, and no hot melt used (ran out) so screws and Titebond glue were it. It is quite sturdy - it has to be as the 6 drivers weigh a lot! This is one heavy speaker based on the drivers alone.
I found some high quality double wall cardboard from a piano packing box. Too good to pass up without repurposing it to something useful, still related to music...
The design is similar to my sims for the 6.5 in PE buyout polycone woofer with a 12 in wide baffle. The slot loaded chamber was made from three of the boxes that the drivers came in and provided a 7 in deep x 7 in tall x 3 in wide chamber times three. The slots are 1.75 in wide x 6 in tall times three. The OB has 7.25 in deep wings that go up 22 in high and then angle in towards the baffle. The drivers are mounted asymmetrically to reduce hysteresis-induced distortion with one side having the basket inside the chamber. The Vifa fullrange is mounted 5 in from the top and 4.5 in from the side. The woofers are wired 3-series-2-parallel for a nominal 6 ohm load. The speaker is bi-amplified and the XO and EQ are performed with a miniDSP. The measurement was made with the speaker on the floor angled 45 deg from the walls with the mic 1.0 meter away at the same height at the Vifa driver.
Here are the results, and I think they turned out pretty nice. REW auto-generated bi-quad EQ's were used just for the woofer, and the Vifa's only had a boost from 17 kHz on up. I left the EQ on the fullrange as minimalist as possible to prevent mucking with the phase in the 500 Hz to 5kHz band. The XO was set at 210 Hz as -24dB/oct Butterworth on both the LPF and HPF.
Woofer (PE part no. 299-609, 4 ohm) SPL vs Freq:
Fullrange (Vifa TC9FD) SPL vs Freq:
System SPL vs Freq -3dB point is about 44 Hz on low end and above 20 kHz on high end:
Distortion - having 6 drivers really helped to bring the distortion low at about -30dB at 40 Hz (0.1% THD) - the cones barely move with normal music program levels. The distortion of the fullrange Vifa, is as usual, just excellent at circa -45dB to -50dB:
Impulse Response - very clean - indicating detailed crisp dynamics that should be possible:
I only had enough drivers to build one at this time so no stereo - but from what I can hear, it sounds very nice. I tested it with the Nautaloss set up as the left channel and the imaging and soundstage was superb. I played some jazz, female vocals, Baroque string quartet, classic rock, pop, it all sounded great. I think the fact that the response is flat and balanced makes it sound good with whatever you throw at it. This speaker was built completely out of cardboard - no foam core used, and no hot melt used (ran out) so screws and Titebond glue were it. It is quite sturdy - it has to be as the 6 drivers weigh a lot! This is one heavy speaker based on the drivers alone.
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Great looking design. Foam core devolves into recycled cardboard thus a "green" enclosure. This could open a whole new group of people to the cause. Also Check out the dumpsters at your local big box stores that sell refrigerators. They are packed in similar material. If you want a more durable enclosure, spray them with auto primer and then you favorite color enamel.
Steinway box... ha ha ha 
Don't they actually come in a box made out of 13 ply Baltic birch veneered with South American bubinga?
Spray paint it like a car huh? I suppose once primer is on, you can sand it pretty smooth and it will take on Porsche "Dessert Sand" color - one of my favorites.
The sound is very similar to the Nautaloss - it being a very flat neutral response. The bass is lower in SPL due to the inefficiency of a dipole woofer (they are terrible for bass punch and require lots of power and cone excursion to make an impact). But the sound that it does make is very low distortion - I don't think typical subs that reach 30 or 40 Hz can do it with -30dB THD - usually lucky to get better than -10dB or -15dB. So it is not quite a fair comparison as I have the Nataloss sub aimed into a corner for 8x more SPL (1/4th space and monopole vs dipole into 1/2-space) - the Nautaloss sub has a lot more punch. So, if I had a bigger amplifier that can really move the 6-cones to push air, it would probably sound very good. At 82 dB volume though, the slot OB and Vifa perform very well. There is the magic of the ambience created by the reflected back wave from the dipole woofer that makes the sound seem more natural and "live". I will only know once I get a stereo set going and have a bigger amp driving the woofers. I would bet that it will sound amazing.
I am pretty happy with the outcome and how it has been consistent with the thread title of cheap and fast to make.
Here is cost to make a system in stereo:
1. miniDSP $85
2. miniDSP 2x4 advanced XO & EQ plugin $10
3. Qnty 12 x PE 299-609 drivers $60
4. Qnty 2 x Vifa TC9FD $20
5. Qnty 4 x banana binding posts $12
6. Qnty 1 x TPA3116D2 2-channel 50watt/ch amp $15 for Vifa's
7. Qnty 2 x TPA3116D2 PBTL monoblock 100watt/ch amps for woofers $60
About $262 (all free shipping).
Don't they actually come in a box made out of 13 ply Baltic birch veneered with South American bubinga? Spray paint it like a car huh? I suppose once primer is on, you can sand it pretty smooth and it will take on Porsche "Dessert Sand" color - one of my favorites.
The sound is very similar to the Nautaloss - it being a very flat neutral response. The bass is lower in SPL due to the inefficiency of a dipole woofer (they are terrible for bass punch and require lots of power and cone excursion to make an impact). But the sound that it does make is very low distortion - I don't think typical subs that reach 30 or 40 Hz can do it with -30dB THD - usually lucky to get better than -10dB or -15dB. So it is not quite a fair comparison as I have the Nataloss sub aimed into a corner for 8x more SPL (1/4th space and monopole vs dipole into 1/2-space) - the Nautaloss sub has a lot more punch. So, if I had a bigger amplifier that can really move the 6-cones to push air, it would probably sound very good. At 82 dB volume though, the slot OB and Vifa perform very well. There is the magic of the ambience created by the reflected back wave from the dipole woofer that makes the sound seem more natural and "live". I will only know once I get a stereo set going and have a bigger amp driving the woofers. I would bet that it will sound amazing.
I am pretty happy with the outcome and how it has been consistent with the thread title of cheap and fast to make.
Here is cost to make a system in stereo:
1. miniDSP $85
2. miniDSP 2x4 advanced XO & EQ plugin $10
3. Qnty 12 x PE 299-609 drivers $60
4. Qnty 2 x Vifa TC9FD $20
5. Qnty 4 x banana binding posts $12
6. Qnty 1 x TPA3116D2 2-channel 50watt/ch amp $15 for Vifa's
7. Qnty 2 x TPA3116D2 PBTL monoblock 100watt/ch amps for woofers $60
About $262 (all free shipping).
Slot OB Sound Clips (mono)
I played around with the XO settings and decided to move the XO point up to about 300 to 350 Hz (depending on if HP or LP) and used a steep 48 dB Linkwitz Riley to reduce bleed of the woofer into the full range and vice versa. I also EQ'd the bottom end to enhance the bass down to 35 Hz given that the distortion was already pretty low that I could sacrifice it with some cone movement to get more body-felt punch. Well it really helped and the speaker sounds really good now - great bass that you can feel and still pretty low distortion. Not too bad for bass from a 12 in wide open baffle! I really like these now and when PE has more of these $4.88 drivers in stock I am going to buy two dozen more
Here is the new XO measured response for woofer, full range, and combined:
Here is the frequency response in 5 dB interval, I think the extension is now about 34 Hz for the -3dB point:
Here is the Harmonic Distortion - still very good:
Here is the Impulse Response - still clean:
Here are some clips (in mono right channel only) so it may be off but I did not miss any bass in these songs.
Sound clips include jazz, guitar solo from a pop song, and dance floor pop. Let me know what you think of the sound.
I played around with the XO settings and decided to move the XO point up to about 300 to 350 Hz (depending on if HP or LP) and used a steep 48 dB Linkwitz Riley to reduce bleed of the woofer into the full range and vice versa. I also EQ'd the bottom end to enhance the bass down to 35 Hz given that the distortion was already pretty low that I could sacrifice it with some cone movement to get more body-felt punch. Well it really helped and the speaker sounds really good now - great bass that you can feel and still pretty low distortion. Not too bad for bass from a 12 in wide open baffle! I really like these now and when PE has more of these $4.88 drivers in stock I am going to buy two dozen more
Here is the new XO measured response for woofer, full range, and combined:
Here is the frequency response in 5 dB interval, I think the extension is now about 34 Hz for the -3dB point:
Here is the Harmonic Distortion - still very good:
Here is the Impulse Response - still clean:
Here are some clips (in mono right channel only) so it may be off but I did not miss any bass in these songs.
Sound clips include jazz, guitar solo from a pop song, and dance floor pop. Let me know what you think of the sound.
Attachments
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I wonder if some delay adjustment will help bring the drivers into phase at the XO point.
How loud can you go around 40hz? This is still just one of those woofers?
EDIT - Ooops, just saw the picture on the previous page with 6 per side. That's some decent Vd to make bass. I'd like to hear this.
How loud can you go around 40hz? This is still just one of those woofers?
EDIT - Ooops, just saw the picture on the previous page with 6 per side. That's some decent Vd to make bass. I'd like to hear this.
I have not played with fine adjustments of time delay yet. I put delay equivalent to 4 inches which is about how far back the acoustic center of the slot baffle cavity is compared to the tweeter. Do you think very small changes to the delay will improve the XO phase alignment?
It can't get too loud without exceeding xmax according to my sims - maybe 93 dB at 1m - but listening to it, I can drive it louder and the cones do not seem to be moving that much yet.
It can't get too loud without exceeding xmax according to my sims - maybe 93 dB at 1m - but listening to it, I can drive it louder and the cones do not seem to be moving that much yet.
93db is decent output depending on your listening habits. Sometimes it's nice to have a chest pounding drum kick though. You could always add sealed subwoofers for that.
I think adjusting delay will improve your phase. Right now the combined response is directly overlaying the individual responses. Try 3 and 5 inches. It's a PITA.If 5" is better, try 4.5 and 5.5". If 3" is better, try 2.5 and 3.5". There should be 6db added output at the XO point.
I think adjusting delay will improve your phase. Right now the combined response is directly overlaying the individual responses. Try 3 and 5 inches. It's a PITA.If 5" is better, try 4.5 and 5.5". If 3" is better, try 2.5 and 3.5". There should be 6db added output at the XO point.
I will give it a try. Do you think a LR vs a Butterworth filter is better? That might have something to do with it too.
Within the minDSP XO graphic dialog I have the XO set so that it happens at exactly -3dB this a perfect 0 dB transition. The measured data shows a -3dB at the point where the two curves cross. so if you look at it carefully (10 dB per div scale).
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You have both the highpass and lowpass at that same frequency?
If so they really should add up at the crossover point, that is not evident in this graph:
Notice how the combined result follows the drop off from the filters. It should combine (sum) at that crossover point.
Here's a comparison:
If so they really should add up at the crossover point, that is not evident in this graph:
Notice how the combined result follows the drop off from the filters. It should combine (sum) at that crossover point.
Here's a comparison:
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I see what you are saying and the only thing I can think that is happening is that the -48dB/oct slope is steep or when I mute either the woofer or the tweeter in miniDSP - it does something different than physically disconnecting the woofer or tweeter for the measurement of one or the other. The XO freq is actually slightly different in the woofer vs tweeter because I noticed that setting at the same freq there was more than a -3dB level at the point where the crossed. So I manually adjusted the freq of the tweeter by about 30 or 50 Hz to get it to match so that the summed response was flat. Maybe it is the Linkwitz Riley crossover that behaves like this? I know with a Butterworth at -12dB the XO freq could be the same for both woofer and tweeter.
I will have to look at this again later.
Edit: just saw your plot. What do you get for a LR4 filter ?
Edit: I think I know why - the physical locations of the tweeter and woofer slot are not accounted for in the simple interpretation for adding responses which assumes they emanate from single point source and are in phase. If you account for the pathlength difference to microphone, the floorbounce cancellations and phase may or may not constructively add up. This is more accurately shown in my sim of this Slot baffle OB - note that the combined response sometimes adds up but at the XO point it kind of follows the woofer then the tweeter response.
I will have to look at this again later.
Edit: just saw your plot. What do you get for a LR4 filter ?
Edit: I think I know why - the physical locations of the tweeter and woofer slot are not accounted for in the simple interpretation for adding responses which assumes they emanate from single point source and are in phase. If you account for the pathlength difference to microphone, the floorbounce cancellations and phase may or may not constructively add up. This is more accurately shown in my sim of this Slot baffle OB - note that the combined response sometimes adds up but at the XO point it kind of follows the woofer then the tweeter response.
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In phase should sum 6db. Use LR for this. BW is a 3db XO, so you either get a 3db bump in the response, or out of phase but flat. You can adjust the points to be different, as long as the measured result is -6db at the same place. Don't worry much about changing the slopes, adjust the delay. That's what'll get it in phase.
Even at 10db division, it should be obvious if there is 6db over the individual driver responses. 6db is over half the division.
Once you get that, you might have a 6db bump in the response. You can eq this out, or better yet spread the driver cross over points apart so their -6db points are at the same place.
This is why first order filters don't work without delay.
LR2 or LR4 will give you more blend at the XO point so the change isn't abrupt. But the LR8 isn't bad either. Trade offs.
Even at 10db division, it should be obvious if there is 6db over the individual driver responses. 6db is over half the division.
Once you get that, you might have a 6db bump in the response. You can eq this out, or better yet spread the driver cross over points apart so their -6db points are at the same place.
This is why first order filters don't work without delay.
LR2 or LR4 will give you more blend at the XO point so the change isn't abrupt. But the LR8 isn't bad either. Trade offs.
Vifa TC6WD fullrange as tweeter in OB?
I saw these cute Vifa's on sale at PE for under $7 ea. They look like they may work well as a fullrange tweeter in an OB - or even other alignments calling for high Qts (0.70) in a compact 2 in driver size.
Peerless TC6WD00-04 Silver Series 2" Midrange | 299-008
There is also the similar TC6FD for $10 ea.
Vifa TC6FD00-04 2" Full Range Paper Cone Woofer 4 Ohm | 264-1126
Does anyone have experience with these drivers?
Thanks,
X
I saw these cute Vifa's on sale at PE for under $7 ea. They look like they may work well as a fullrange tweeter in an OB - or even other alignments calling for high Qts (0.70) in a compact 2 in driver size.
Peerless TC6WD00-04 Silver Series 2" Midrange | 299-008
There is also the similar TC6FD for $10 ea.
Vifa TC6FD00-04 2" Full Range Paper Cone Woofer 4 Ohm | 264-1126
Does anyone have experience with these drivers?
Thanks,
X