For the last three replies: What I am trying to tell you desperately -and this will be my last attempt I promise- is the following: First, it is not only about halving the box volume, but the QUALITY of the bass that improves dramatically both in clarity, and impact, even its subjective extension is better, probably due to the reduced LF distortion. What is more (don't ask why, because I haven't figured it out yet) the PPC loading is almost totally free of one of the major plagues common in vented boxes, the upper bass coloration - present in most designs with very few exceptions.
Second. Try not not form an opinion like: bass starts at 8", before you either built, tried, compared a well executed PPC with decent 6" woofers against a single woofer 8 incher, because as I said earlier you might be in for a big surprise.
Best regards: Andrew
Second. Try not not form an opinion like: bass starts at 8", before you either built, tried, compared a well executed PPC with decent 6" woofers against a single woofer 8 incher, because as I said earlier you might be in for a big surprise.
Best regards: Andrew
This sounds like a firecracker so to start an ultra long new conversation.
Many people has the expectation that a single 8 incher woofer it can get down in the world of sub woofers.
No is not working that way, I got Philips FB815 3Way (150W) closed cabinet before many years back, because I wanted tight Bass which is not enough so to sound as sub woofer when needed.
I am not aware if technology advanced enough so to offer the same Bass output from an 6 incher woofer, but if it did? I would not be made by having a cone of carton and it would cost much higher than a regular 8 incher woofer.
Last but not least, diameter it does matters in frequencies range.
An 8" carton cone woofer has more chances playing some Mid frequencies in comparison with an 6" made by hard carbon fibers.
Dragonweed, I have some questions for you.
1. Which configuration do you prefer between A and B and whay ?
(A) l> <l . . . (B) l> l>
2. Do you think it is necessary to fill any sound absorbing material in the chamber between the two woofer ?
Even though the two cones are moving coherently, since there are physical obstacles such as magnets and frames in the chamber, reflection and diffraction are caused which can make unwanted peak and dip in the mid frequency. Or unwanted standing waves may be caused because of incomplete coherence between the moving of two cones, IMO.
Going step by step,
To Kirtakos: The answer is yes and no... Yes, technology has advanced somewhat is the aspects of better cone materials, stronger, more linear motor structures, using FEA in the driver design. No, there are still no miracles, no shortcuts to cheat basic laws of phisycs. We all know the mutually exclusive rules of driver size, efficiency, box volume, and low freq. extension. You still must sacrifice some of them to gain in other areas. A 5" driver in small box, with 90 dB/W/m going down to 30 Hz - that is still a dream, and I am afraid it will remain so for a while.
If you read carefully, in my case you will see that the 30 Hz -3dB point is achieved in a small box, the price you pay is the increased cost of two woofers, plus the complexity of the box, and last but not least the near-miserable sensitivity: 84 dB/W/m. So they will play thunder for you, but you must drive them hard to do so . Fortunately the woofers used here are extremely rugged designs both electrically, both mehanically, so they can take quite some beating. Still, do not except the LEVEL of bass you are able to get with a good 10" woofer in a 3 cu. ft. box...... Their optimal playing area is in a cca. 250-300 sq.feet room at least 3' away from walls.
To icsohn 94: good point, good question. The distance between the BACKS of the drivers (so it is config A) should be as small as phisycally possible -in this case about half an inch,- to keep the coupling of the drivers tight (stiff airspring). I layered the four internal walls with 1/2" thick felt, amd haven't noticed any detrimental effect -such as mid coloration, noise, or distortion during sine-sweep tests.
I am aware of the fact that the two drivers will always differ a little from each other causing residual distortion, but these distortions are still much less audible than the ones using a single woofer in a double sized enclosure.
To fishball 79: That is exactly how they are configured, except the volume is 14 liters (+the comp. enclosure) for the two D.6,8-s.
To Kirtakos: The answer is yes and no...
Yes, technology has advanced somewhat is the aspects of better cone materials, stronger, more linear motor structures, using FEA in the driver design. No, there are still no miracles, no shortcuts to cheat basic laws of phisycs. We all know the mutually exclusive rules of driver size, efficiency, box volume, and low freq. extension. You still must sacrifice some of them to gain in other areas. A 5" driver in small box, with 90 dB/W/m going down to 30 Hz - that is still a dream, and I am afraid it will remain so for a while. If you read carefully, in my case you will see that the 30 Hz -3dB point is achieved in a small box, the price you pay is the increased cost of two woofers, plus the complexity of the box, and last but not least the near-miserable sensitivity: 84 dB/W/m. So they will play thunder for you, but you must drive them hard to do so . Fortunately the woofers used here are extremely rugged designs both electrically, both mehanically, so they can take quite some beating. Still, do not except the LEVEL of bass you are able to get with a good 10" woofer in a 3 cu. ft. box...... Their optimal playing area is in a cca. 250-300 sq.feet room at least 3' away from walls.
To icsohn 94: good point, good question. The distance between the BACKS of the drivers (so it is config A) should be as small as phisycally possible -in this case about half an inch,- to keep the coupling of the drivers tight (stiff airspring). I layered the four internal walls with 1/2" thick felt, amd haven't noticed any detrimental effect -such as mid coloration, noise, or distortion during sine-sweep tests.
I am aware of the fact that the two drivers will always differ a little from each other causing residual distortion, but these distortions are still much less audible than the ones using a single woofer in a double sized enclosure.
To fishball 79: That is exactly how they are configured, except the volume is 14 liters (+the comp. enclosure) for the two D.6,8-s.
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Be careful with ported isobaric enclosures. The two drivers do not couple properly at the port resonant frequency due to the compliance of the air between the drivers. The resonance in the enclosure minimises movement of the rear driver, but the front one can still move due to the "springiness" of the air between the drivers.
The attached graph shows the excursion of two MCM55-2421 drivers mounted face-to-face in a 30 litre enclosure tuned to about 30 Hz. The black line is excursion of the rear (inner) driver, the red line is excursion of the front driver, and the green line is the excursion if the two drivers were coupled rigidly (cone glued to cone). The difference rapidly gets worse if you increase the volume between the drivers, for example by mounting them in tandem (both facing out).
The attached graph shows the excursion of two MCM55-2421 drivers mounted face-to-face in a 30 litre enclosure tuned to about 30 Hz. The black line is excursion of the rear (inner) driver, the red line is excursion of the front driver, and the green line is the excursion if the two drivers were coupled rigidly (cone glued to cone). The difference rapidly gets worse if you increase the volume between the drivers, for example by mounting them in tandem (both facing out).
Attachments
Very important point.
I think it is not just for ported isobaric enclosure but for both ported and sealed one.
To minimize the volume between two cones shall be necessary for minimiaing this effect.
For that, l>l> is desirable than l><l.
But, the important thing is what is the influence on the sound actually due to the movement differency.
Is there any information on this ?
Correct. I am aware of the problem (which cannot be avoided in vented PPC), but its effect is not as detrimental as it seems. First, the drivers have a mechanically rather stiff suspension (their Vas is only 14 liters), second the air volume between the drivers is only 3 liters (the rest is "filled" with their frame and magnet structures), so the resulting air spring is rather stiff.
If it causes any distortion, it is around port resonnce (30 Hz),where the ears sensitivity to that aspect is not too high, and very likely still distorts less than a single woofer with its bending cone at that frequency.
Anyway this design went through already on a few hundred hours of listenings and demos for friends with good ears and gears, and none of them ever complained about any kind of distortion, actually almost all of them commented immediately the unusual clarity and articulation of the lower registers.
If it causes any distortion, it is around port resonnce (30 Hz),where the ears sensitivity to that aspect is not too high, and very likely still distorts less than a single woofer with its bending cone at that frequency.
Anyway this design went through already on a few hundred hours of listenings and demos for friends with good ears and gears, and none of them ever complained about any kind of distortion, actually almost all of them commented immediately the unusual clarity and articulation of the lower registers.
Oh yeah..... Don't ask about the tweeters, they are the "one pair on the planet" type, put together from different parts sourced from China
How about doing a tweak similar to the tweak Dick Olsher does on the tweeters for his Black Dahlia speakers (from this page: The Black Dahlia - Dick Olsher offers a Do-It-Yourself Loudspeaker Kit):
The MB Electronics 1-inch titanium dome is one that I'm intimately familiar and still comfortable with. Its first break-up mode is at 26 kHz. Transients are fast and detailed, but in its stock form the tweeter is a bit too alive with a slight metallic aftertaste.
To minimize the MB's sonic signature, I modify it as follows. First, using a pair of pliers remove the plastic grill from the face plate and discard it. For the next step you'll need to purchase a spray can of a fixative with the trade name of Tuffilm, available at art supply houses. This fixative is normally used to apply a matte coating to paintings, but in this application it serves to dampen out low-level resonances in the titanium. Mask the surround of the dome with say masking tape to protect it from the spray. Then apply a 1-second burst of the coating, wait 5 minutes for the stuff to dry and repeat the application. After another 5 minutes, repeat the application for a third and final time. The treated tweeter visually appears duller, and sounds cleaner, although its measured frequency response is no different from that of the stock version.
Enjoy,
Deon
Thanks for the advice, but Tuffilm (under that brand name) is unobtanium in my country.. I was thinking on a similar treatment of the dome, but without being sure what I am doing, I don't want to risk ruining this -otherwise excellent- tweeter. You don't know by chance the material Tuffilm is made of? Or some other brand that might be available around here?
Find the MSDS for the Tuffilm that may tell the composition, then you can search for the equivalent product.
Was going to comment that the "magic" Qt for a driver is between 0.35 and 0.45. If you sim drivers in that range with a variety of enclosures, you will quickly see why that is so. Does not mean that they will be the "best" for any given situation in terms of sonics, that again, is another issue.
I think that the OP's request for "impact" needs to better defined. One can have impact without deep bass, one can have deep bass with impact, one can have "regular bass" with or without impact. Impact is subjective - the question is what subjective sense is being sought?
Was going to comment that the "magic" Qt for a driver is between 0.35 and 0.45. If you sim drivers in that range with a variety of enclosures, you will quickly see why that is so. Does not mean that they will be the "best" for any given situation in terms of sonics, that again, is another issue.
I think that the OP's request for "impact" needs to better defined. One can have impact without deep bass, one can have deep bass with impact, one can have "regular bass" with or without impact. Impact is subjective - the question is what subjective sense is being sought?
The effect is very much smaller for a sealed enclosure. It is related to the ratio of volume between the drivers to the volume of the enclosure. In a ported enclosure at resonance the effective volume of the enclosure seems very small, making the between-driver volume large by comparison.
I don't have any experience with it. I would expect it to matter most when the drivers are driven close to their maximum excursion. The outer driver will reach maximum excursion sooner than the inner one, limiiting the maximum attainable output by a few dB. The graph I gave was for face-to-face mounting. It doesn't take much additional volume, such as in-line or back-to-back mounting, to make the outer driver excurse up to 50% more at resonance than the inner driver.
In an isobaric config the inner driver reaches its Xmax well before the max power rating is hit and well before the outer woofer reaches its electro mech limit. The solution to this is to driver them with seperate amps. Both inner woofer are driven from a stereo amp and the outer two are driven with yet another stereo amp. Reduce the level to the inner drivers and problem solved.
To address the midrange coloration of iso is to limit the higher frequencies to the inner driver. Get a minidsp and experiment.
My mltl 6.5" sub works wonders. As has been mentioned "slam" requires a certain minimium spl for the room size, but also requires a light weight cone to pull off the higher frequency dynamics that make a rimshot sound realistic. Typically you would need a driver that has an upper bandwidth of 2k, and 5k being better (but increasingly difficult to find such a driver). The peerless 6.5's I use have an upper bandwidth of 5k, but really only usable to just above 2k to avoid breakup in the 4-5k regoin.
Bottom line this sub achieves a low end responce of 27Hz and everyone that has heard it also is looking for the sub. Have had this configured as a two way, three way and a mtm three way.
To address the midrange coloration of iso is to limit the higher frequencies to the inner driver. Get a minidsp and experiment.
My mltl 6.5" sub works wonders. As has been mentioned "slam" requires a certain minimium spl for the room size, but also requires a light weight cone to pull off the higher frequency dynamics that make a rimshot sound realistic. Typically you would need a driver that has an upper bandwidth of 2k, and 5k being better (but increasingly difficult to find such a driver). The peerless 6.5's I use have an upper bandwidth of 5k, but really only usable to just above 2k to avoid breakup in the 4-5k regoin.
Bottom line this sub achieves a low end responce of 27Hz and everyone that has heard it also is looking for the sub. Have had this configured as a two way, three way and a mtm three way.
I was just thinking, how about using shallow-mount subwoofers. These are made to be shallow, so the drivers can be mounted closer together. Here are a few examples:
GRS 10SSW-4 10" Shallow Mount Car Subwoofer 4 Ohm @ $41.50 ea. from Parts Express
Tang Band W8-2022 8" RBM Subwoofer 8 Ohm @ $134.00 ea. from Parts Express
Peerless 835028 10" XLS Shallow Subwoofer @ $173.26 ea. from Parts Express
Aurasound NSF8-495-4A & NSF8-495-8B 8" woofers @ 139,00€ ea. from QUINT Audio
Rockford Fosgate R2SD4-10 Prime R2 Series 10" shallow subwoofer with dual 4-ohm voice coils @ $99.99 from Crutchfield
MTX FPR10-04 Shallow-mount 10" 4-ohm subwoofer @ $159.99 from Crutchfield
Pioneer TS-SW2502S4 Shallow-mount 10" 4-ohm subwoofer @ $159.99 from Crutchfield
Kenwood Excelon KFC-XW800F Shallow-mount 8" 4-ohm subwoofer @ $169.99 from Crutchfield
Kicker 40CWRT102 CompRT shallow-mount 10" subwoofer with dual 2-ohm voice coils @ $169.99 from Crutchfield
Something like the GRS 10SSW-4 10" Shallow Mount Car Subwoofer is cheap enough to experiment with. What do you guys think?
Deon
GRS 10SSW-4 10" Shallow Mount Car Subwoofer 4 Ohm @ $41.50 ea. from Parts Express
Tang Band W8-2022 8" RBM Subwoofer 8 Ohm @ $134.00 ea. from Parts Express
Peerless 835028 10" XLS Shallow Subwoofer @ $173.26 ea. from Parts Express
Aurasound NSF8-495-4A & NSF8-495-8B 8" woofers @ 139,00€ ea. from QUINT Audio
Rockford Fosgate R2SD4-10 Prime R2 Series 10" shallow subwoofer with dual 4-ohm voice coils @ $99.99 from Crutchfield
MTX FPR10-04 Shallow-mount 10" 4-ohm subwoofer @ $159.99 from Crutchfield
Pioneer TS-SW2502S4 Shallow-mount 10" 4-ohm subwoofer @ $159.99 from Crutchfield
Kenwood Excelon KFC-XW800F Shallow-mount 8" 4-ohm subwoofer @ $169.99 from Crutchfield
Kicker 40CWRT102 CompRT shallow-mount 10" subwoofer with dual 2-ohm voice coils @ $169.99 from Crutchfield
Something like the GRS 10SSW-4 10" Shallow Mount Car Subwoofer is cheap enough to experiment with. What do you guys think?
Deon
That can work. The best would be if you can get a spray that is something like dammar varnish dissolved in alcohol. You could even use it on your woofers.
Deon
So far I've already tried damar varnish (with turpentine solvent) an an odd soft dome lying around, but I wasn't very impressed, the sound became crisper but not the way I like it. It gives very good result however on most type paper cone woofers, but on domes I am not sure... Maybe on metal domes it is a different story, and if it's a no-go, it can be still removed easily. Will give it a try.
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