shimizu@unix.sri.com (Dan Shimizu) (06/12/91)
Hi all, My cohort and I are on our devilish way to become speaker designers and we're trying to design a pair of subs to go along with some sattelite speakers we are building. I prefer sealed box designs, so I don't have to go through the hassle of tuning and estimating Ql (box loss) that is required for vented box designs. My question is what is a good driver to use for a sealed sub? I just heard about the Audio Concept 12" (AC12 Mk.2). They sound good, does anyone have any experience with these drivers? On the other hand, what drivers are good for vented subs? Thanks, DAN
moskowit@paul.rutgers.edu (Len Moskowitz) (06/13/91)
The AC12 has gone through numerous changes and no one was able to give me a set of T/S parameters that some other person didn't contradict. I ended up with three sets and no one knew which was correct. I'd steer clear of this one. Len Moskowitz
francis@chook.ua.oz.au (Francis Vaughan) (06/14/91)
In article <13024@uwm.edu>, shimizu@unix.sri.com (Dan Shimizu) writes: |> My cohort and I are on our devilish way to become speaker |> designers and we're trying to design a pair of subs to go |> along with some sattelite speakers we are building. I |> prefer sealed box designs, so I don't have to go through the |> hassle of tuning and estimating Ql (box loss) that is required |> for vented box designs. My question is what is a good driver |> to use for a sealed sub? I just heard about the Audio Concept |> 12" (AC12 Mk.2). They sound good, does anyone have any experience |> with these drivers? There is little problem about Ql really. It is easily measured by determining the final Q of your box after it is built. You need a signal generaror, counter, amp, accurate resistor and a DMM accurate at low frequencies (not hard). I would always measure the final box no matter what, sealed or vented. Stuffing in a sealed box is very important too, and the tolerances in both the driver you buy and the box you build mean that it is very unlikley you will ever build a box first time out that meets spec. Best trick is to build one to throw away (just like software really :-). Choose a driver, and calculate the box you figure you need, bang it together out of whatever comes to hand. Make sure it is reasonably rigid and leak tight, but hey, you can do this with no thought to cosmetics so it can be quick and cheap. Measure the driver. Get your own TS parameters. (If you decide on a sealed box, you will need to put a vent in the box for some measurments, and later seal it up again. You can tweak to your hearts content. You will almost always find that the box volume is wrong. Build the box oversize and add junk inside to get it right (heavy books are good, so are bits of wood). The stuffing will make a big difference. Once it is right THEN build it for real. Measuring the system resonances and Q for real are very good guides to how it will perform. Personally I prefer a sealed system Q of .707. Try a Dynaudio 30W100. Not cheap but very nice. Big too. Francis Vaughan.
miker@polari.UUCP (Mike Ranta) (06/17/91)
In article <13024@uwm.edu> shimizu@unix.sri.com (Dan Shimizu) writes: > >My cohort and I are on our devilish way to become speaker >designers and we're trying to design a pair of subs to go >along with some sattelite speakers we are building. I >prefer sealed box designs, so I don't have to go through the >hassle of tuning and estimating Ql (box loss) that is required >for vented box designs. My question is what is a good driver >to use for a sealed sub? I just heard about the Audio Concept >12" (AC12 Mk.2). They sound good, does anyone have any experience >with these drivers? I'm listening to a pair of AC12 subwoofers as I write this. I have tried several high quality 10" and 12" drivers in my quest for the perfect subwoofer, and have to admit the AC12s come awfully close! I like fast, clean, tight and solid bass down low without excessive distortion or non-linearity at high levels. The AC12s do this very well in a sealed 4.0 cubic foot enclosure. You can also use two per side in an isobarik configuration in a 2.0 cubic foot enclosure if you want to give up 3 db of efficiency (Audio Concepts does this with one of their subwoofer kits). They have a very linear cone suspension yet are reasonably resistant to "bottoming" when driven hard. With 150 watts driving each of them in my system, the amp usually clips before the drivers complain. They are an honest 90 - 91db at 1 watt/1 meter. My second choice (less expensive too) would be Madisound 10208 10" drivers in a 1.5 - 2.0 cubic foot sealed enclosure. They are a few db less efficient and their 3db down point is a half octave or so higher, but they have the same subjective "tight" sound and take power well. >On the other hand, what drivers are good for vented subs? In my opinion, there are very few drivers that work well in vented subwoofers. On the computer, several look great, but in practice, nearly all of them distort and/or bottom badly at frequencies well above and below the tuning frequency of the enclosure when driven hard. You are also correct about having to second guess box losses and other factors. As you're probably aware, ported designs also roll off at 12db per octave versus 6 for sealed systems. For this reason and the first one above, they do not respond to "EQ" well if they require it (or the owner likes it). There are exceptions to all this, but you'll likely be happier with a good sealed system. miker@polari.uucp (Mike Ranta)
miker@polari.UUCP (Mike Ranta) (06/17/91)
In article <13060@uwm.edu> moskowit@paul.rutgers.edu (Len Moskowitz) writes: > >The AC12 has gone through numerous changes and no one was able to give >me a set of T/S parameters that some other person didn't contradict. >I ended up with three sets and no one knew which was correct. I'd >steer clear of this one. Interesting. Are you referring to the folks at Audio Concepts not knowing the Thiel and Small parameters? My AC12s measured within 10% of the specs published in their catalog and they are simply the best sealed box 12" drivers I've ever come across. I can also only say nice things about the folks at Audio Concepts.
bill@verdix.com (William Spencer) (06/18/91)
in article <13024@uwm.edu>, shimizu@unix.sri.com (Dan Shimizu) says: > I just heard about the Audio Concept > 12" (AC12 Mk.2). They sound good, does anyone have any experience > with these drivers? I got some AC10's recently. Sound pretty good I guess -- I still haven't incorporated them into my main design yet though. I have a couple of complaints though. They nicely don't glue on the front gasket so front mounting looks better. But the foam surround actually sticks out in front of the frame which can cause trouble. Even worse, the foam is caught between mounting screws and the frame. Tightening the screw can cause the foam to be pulled loose. I'm not sure how other speakers deal with this. Maybe the gasket just keeps you from seeing the damage, I don't know, but I've never seen this problem before. I used a 2.77 cu. ft. box, stuffed. By attempting to avoid booming with a low Q alignment I actually got more boom. The tuning is a low 32 Hz or so but that is all but inaudible due to rolloff. Meanwhile, room and floor effects cause booming in the 70-80 Hz region and suckout in the range above that. Raising it makes the bass even leaner but lowering it helps. However, only in subwoofer use can the low position work well in my experience. Too much distance between the woofer and midrange results. Porting seemed promising. Brought out that deep bass even in a marginal tuning. >From my understanding it looks like this woofer is best suited to a tuning with some peaking in the deep bass. If the room effect causes more peaking at a higher frequency though the over all effect may be better in a subwoofer application. I have heard that these woofers are made by Carbonneau. The have their own line which is both cheaper and possibly better including rubber surround types, carbon impregnated poly cones, and heavy paper cones. I don't know about multiple specs from Audio Concepts, but they have different response graphs. Of course they may all be right for different samples and test methods. Carbonneau now includes computer generated plots and real response curves in their documentation. The real curves all look poorer than the simulated ones. The Madisound woofers have fairly flimsy cones according to reports and my own experience. They can still work well I guess. The Precision/Swan woofers are not intended for sealed boxes but are better made from what I hear. Don't know about the Eclipse (Meniscus?) woofers. Pyles are sort of a compromise between the hi-fi types and sound reinforcement types and are good in some applications. The point about building an experimental box is a good one. You might be better buying boxes also -- life is too short to spend building very plain rectangular boxes. You can enclose drivers seperate for more flexibility when experimenting. When you're ready for 2" thick pyramids or whatever then you'll have to go custom. Bill Spencer P.S. A couple of addresses: Parts Express 340 E First St. Dayton Ohio 45402 800 338 0531 Eminence (Cast, Regular, "Thruster"), Pioneer, Sanyo (CHEAP!), MG ("Professional" components, not credited to MG in catalog), a few Phillips and Polydax components, Motorola (piezos) Best prices within selection. Not "high-end" oriented. Also VCR parts and other electronics, low cost boxes (including stage monitors). MCM Electronics 650 Congress Park Dr. Centerville Ohio 45459-4072 513 434 0031 Pyle, Electro-Voice (standard 12,15, and 18" only, at best prices), Pioneer, MG, Pyramid. Also repair parts, meters, oscilloscopes. Reasonably priced quality enclosures. Caution, I have found some errors in specs given (1W/1M != 1W/1ft.) Gold Sound P.O. Box 141 Englewood, CO 80151 303 789 5310 Catalog $2 JBL, E-V, Gold Sound (serious), Audax, Morel, SEAS. Good prices. Serious about "pro" components. Catalog includes tiny response graphs for most drivers. McGee Radio 1901 McGee St. Kansas City, Missouri 64108-1891 816 842 5092 Orders 800 87MCGEE Catalog $2 More expensive but some good bits. Polydax, Pyle (full line), Motorola (would you believe a deal on a Piezo driver and an E-V horn combo?), E-V (near full line), MTX. Madisound Speaker Components 8608 University Green Box 4283 Madison, Wisconsin 53711 608 831 3433 Peerless, Madisound (low cost, fairly flimsy but OK), Eclipse, Morel, KEF, Vifa, Focal, Dynaudio, Eton, many crossover components. A few good kits. *Catalog includes graphs, etc. for many drivers.* Woodstyle enclosures. Audio Concepts 901 S. 4th St. La Crosse, WI 54601 800 346 9183 tech questions 608 784 4570 Kits, Dynaudio, Focal, SEAS (very limited selection of most popular pieces on these 3), Audio Concepts (I called them, the JC12 subwoofer _really_ has an Xmax of 11 cm.!). Crossover components, speaker designs, info, Loudspeaker Design Cookbooks. A & S Speakers 3170 23rd St. San Fransisco CA 94110 415 641 4573 Scan-Speak, VMPS (complete speakers AND drivers), Eton, Dynaudio, Audax/Polydax, Eminence (short list), Focal, Morel, Peerless, MB-electronics (titanium dome tweeters), Phillips, SEAS, Nelson-Reed, Crossover parts & assemblies, Woodstyle cabinets. Speaker designs. SRS Enterprises "The Speaker Shop" 318 S. Wahsatch Ave. Colorado Springs, Co. 80903 719 475 2545 Pyle, Pioneer. Prices good. Full Pyle line. Carbonneau 609 Myrtle N.W. Grand Rapids Michigan 49504 616 456 9528 3 lines of woofers: 20% graphite reinforced polypropylene cone with foam suspension, same with rubber suspension (lower frequency & efficiency), and treated paper cone with rubber. Includes dual voice coil subwoofers. Range 5.25" to 12". Good prices. Caution: my catalog has "preliminary" specs. Zalytron Industries 469 Jericho Turnpike Mineola, NY 11501 516 747 3515 Polydax, Siare, Vieta, SEAS, Dynaudio, Focal, Cabasse, Phillips, Zalytron, crossover compenents, etc. Transducer Technology (Division of Watters Sound Wave Co.) 4320 Spring Valley Rd. Dallas, TX 75244 214 991 6994 Cabasse (full line of concave diaphram/dome drivers), Accuton (Thiel GmbH, not the other Thiel; very neutral concave _ceramic_ dome mids and tweeters) Vieta, Audiom by Focal (professional Focal line, pricey), Stage Accompany (professional ribbon/leaf drivers, woofers, systems, pricey), Tekton (sub-bass)
sbhattac@cmcl2.NYU.EDU (Shankar Bhattacharyya) (06/18/91)
In article <13174@uwm.edu> miker@polari.UUCP (Mike Ranta) writes: >>On the other hand, what drivers are good for vented subs? > >In my opinion, there are very few drivers that work well in vented >subwoofers. On the computer, several look great, but in practice, >nearly all of them distort and/or bottom badly at frequencies well >above and below the tuning frequency of the enclosure when driven >hard. You are also correct about having to second guess box losses >and other factors. As you're probably aware, ported designs also >roll off at 12db per octave versus 6 for sealed systems. For this >reason and the first one above, they do not respond to "EQ" well >if they require it (or the owner likes it). There are exceptions >to all this, but you'll likely be happier with a good sealed system. I agree that closed boxes have the merit that they are almost impossible to mess up entirely, and so they make a most desirable way to enter the world of low bass. But good vented boxes are possible. I don't know much about vented boxes, so I will refrain from making too many specific recommendations, but many of Madisound's drivers look as if they were designed for vented boxes. Audio Concepts seems to lean towards sealed boxes, if their selection of drivers is any indication. The Eton drivers are designed for vented boxes (thanks, Seth), and the Dynaudio 30W54 works in one, although it requires rather large internal volume. For what it is worth, the 30W54 cannot produce F3 below 40 hz in a sealed box without bass boost. In a B4 alignment, without any equalization at all, the F3 would be in the neighbourhood of 25 hz, depending on the sample. The reason vented systems bottom is that they are wildly unprotected below resonance. This suggests the need for some subsonic filtering. Sixth order alignments provide this "for free", and may solve many of the complaints people have about vented boxes. Seth Bradley and Len Moskowitz have posted information on building such systems using the Precision TA305, and its successors, which achieve serious bass at serious spl. Also, the question of whether vented boxes or sealed ones have lower bass is open to discussion. While sealed boxes roll off with shallower slope below their F3, their F3 is significantly higher than driver Fs. For a vented box, in a B4 alignment, F3 is about the same as Fs. I am not making any cosmic inferences based on this, but it is something to think about. I have stuck with sealed boxes, and the related aperiodic designs, basically because they are easy. I confess to some prejudice against vented systems, but I know that my prejudice is not well-founded. If you are prepared to biamp (and most woofer users are eventually likely to), adding the low frequency filtering is not a pain. - Shankar