@fluid This is definitely interesting to read the process of design, how it was done the other way around. Pretty much all dome driver design is done through obtaining certain specs, mostly HD and FR, along with low Fs and Qts, in order to be able to use the driver from the lowest possible crossover point upwards. Qms is rarely cited, but does present a specific sound quality characteristic. This goes along with my theory that using the approach of best possible technical specs as a yardstick doesn't always result in the most organic and natural sound people are trying to chase. Paper or cellulose can have a very pleasant and wideband breakup behavior depending on the composition of fibers and binding agent chosen. I've always preferred the sound of a paper cone in gentle partial breakup mode when paired with other like drivers having similar traits, combined with shallow filter rolloff curves.
Kurt Müller makes some of the best dome diaphragms used in higher end designs. Audax and Seas have been long standing customers of theirs and the performance of the drivers using these domes are some of the best in existence. The T35-C002 is a good example and shows what can be accomplished using a carefully engineered 35mm fabric dome. This is my favorite tweeter combined with other large dome mids, specifically using shallow crossover slopes.
Perhaps the outside of the box thinking, creating a large paper dome mid is a better way to achieve a very natural sounding speaker. In the past, companies like Thiel have done it the other way around, using very neutral, low distortion drivers made from stiffer metal alloys to achieve close to perfect pistonic behavior in their most linear portion of bandwidth. This approach makes technical sense, but the use of highly dampened, low Qts and Qms drivers can strip the sound from most of its macro-dynamic, lower lying components. This usually leads to a very stale and dull presentation, especially at lower volume levels. It also proves the notion that our ears listen to and quantify music reproduction in a different way, expecting a certain amount and type of coloration to convey music in a more engaging and pleasant way. Its sort of like eating a really nice steak without any seasoning - its a beautiful piece of meat, but doesn't taste that interesting or pleasing its own.
I respect using the design approach of aiming for the best technical specs and theoretical performance, but it doesn't reflect the actual preference for some amount of even order HD people actually find pleasant. The problem with aiming for the lowest possible distortion numbers is low level detail usually gets lost. That also explains why many speakers that employ very low distortion, well dampened, low sensitivity drivers tend to sound un-engaging at lower volume levels. They typically require alot of amplifier power to wake up and deliver music in an interesting and energetic way. There's a subtle threshold where coloration and detail retrieval balance and combine properly to achieve natural and musically correct, ear pleasing presentation of music.
All this is likely why I prefer the sound of high sensitivity paper cone pro woofers to smaller, low sensitivity alloy cone drivers. The same holds true for treated cloth surrounds vs. heavier rubber surrounds found on woofers. The accordion style cloth surrounds usually tend to dampen less and allow more low level detail retrieval in the lower mids. These drivers typically have higher Qms, which is a good sign the motor is capable of reproducing very subtle, low level nuances in the upper bass and low mids.
Kurt Müller makes some of the best dome diaphragms used in higher end designs. Audax and Seas have been long standing customers of theirs and the performance of the drivers using these domes are some of the best in existence. The T35-C002 is a good example and shows what can be accomplished using a carefully engineered 35mm fabric dome. This is my favorite tweeter combined with other large dome mids, specifically using shallow crossover slopes.
Perhaps the outside of the box thinking, creating a large paper dome mid is a better way to achieve a very natural sounding speaker. In the past, companies like Thiel have done it the other way around, using very neutral, low distortion drivers made from stiffer metal alloys to achieve close to perfect pistonic behavior in their most linear portion of bandwidth. This approach makes technical sense, but the use of highly dampened, low Qts and Qms drivers can strip the sound from most of its macro-dynamic, lower lying components. This usually leads to a very stale and dull presentation, especially at lower volume levels. It also proves the notion that our ears listen to and quantify music reproduction in a different way, expecting a certain amount and type of coloration to convey music in a more engaging and pleasant way. Its sort of like eating a really nice steak without any seasoning - its a beautiful piece of meat, but doesn't taste that interesting or pleasing its own.
I respect using the design approach of aiming for the best technical specs and theoretical performance, but it doesn't reflect the actual preference for some amount of even order HD people actually find pleasant. The problem with aiming for the lowest possible distortion numbers is low level detail usually gets lost. That also explains why many speakers that employ very low distortion, well dampened, low sensitivity drivers tend to sound un-engaging at lower volume levels. They typically require alot of amplifier power to wake up and deliver music in an interesting and energetic way. There's a subtle threshold where coloration and detail retrieval balance and combine properly to achieve natural and musically correct, ear pleasing presentation of music.
All this is likely why I prefer the sound of high sensitivity paper cone pro woofers to smaller, low sensitivity alloy cone drivers. The same holds true for treated cloth surrounds vs. heavier rubber surrounds found on woofers. The accordion style cloth surrounds usually tend to dampen less and allow more low level detail retrieval in the lower mids. These drivers typically have higher Qms, which is a good sign the motor is capable of reproducing very subtle, low level nuances in the upper bass and low mids.
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On a narrow baffle it will almost certainly need a notch between 1.5 and 2.5 k. If you use it as a bass - mid, that's where you'll probably need to address it. On a big baffle its textbook, but that changes on a typical baffle width around 12". I had this issue with the paper cone version, which is why i mentioned it. The concave cone design my change this a little, but its mostly based on baffle geometry.
Also, the linearity of the WO24TX is deceptively neutral and linear in FR. There are two major odd order lumps from 1.5k upwards that can be audible. Being very picky here, I personally wouldn't use it past 500 hz without attending to these things, but perhaps to most people's ears these things are benign. I also had similar experiences with the MR13TX, but at higher frequencies.
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Some good news regarding the SB34NRXL. I've been trying a surround edge coating on a test woofer and it appears the bump/wiggle past 700 can be tamed to a large extent. This would at least be enough to make a 2nd order 400 - 450 hz HP possible, possibly higher. If the problem area can be conquered, this woofer could be a great solution to bridge the gap on a 3 way with the D7608.
Its been tricky getting a clean measurement on this woofer in a large baffle due to reflections, requiring near field mic placement. This doesn't allow for a proper 1m on axis measurement. Ground plane mic placement is also a problem. I'm going to try this outside on a 3 x 4 ft baffle.
Its been tricky getting a clean measurement on this woofer in a large baffle due to reflections, requiring near field mic placement. This doesn't allow for a proper 1m on axis measurement. Ground plane mic placement is also a problem. I'm going to try this outside on a 3 x 4 ft baffle.
Ah... Forgot to mention I'm using it open baffle just about nude & use miniDSP DSP/PEQ. Probably changes a lot. It really sounds great in this context.
@mikessi That WO24TX is very tidy in the low end and goes low in an average sized reflex box. I'm curious how well it does OB with a moderately low Q. I think it can make up for the low Q with excursion. I do warn that the motor on these WO24 series is prone to bottoming out with larger transients. It has a raised inner plate for induction control which contacts the back of the VC surprisingly early. I killed one when my finger bumped into the scaling switch on my sine generator, accidentally switching it 10 dB louder. The VC former is thin and coupled with aluminum windings, its somewhat fragile. Luckily it was covered under warranty...
PE may be sending me a pair of the new Tang Band 75-1558SH to evaluate. We'll see if its as good as the previous SE model.
Can't see letting it go below 150Hz LR4; there's too much bass signal otherwise with no trapped air in an enclosure to help. I've briefly tested it 125~250Hz. >200, the subs aren't good; below 150, I think I risk the WO24TX, so 150~200Hz is the right point, methinks. The end user likes to play his music loud often. I used 100Hz LR4 with the 8" Seas mid in Linkwitz Orions but felt it pushed the driver excursion unnecessarily, so moved it up to 125Hz with no audible consequence. Ditto my 521-inspired clones -- created too much vibration in the top baffle.
Slight change in discussion: Most dome mids have a sealed enclosure built into the driver. In my case, the Bliesma M74A I am using has a nice aluminum case which acts as a rear chamber. Is there an advantage to constructing a sub-enclosure for this driver (or similar drivers) to shield them from the woofer radiation inside the box?
@jkatchy asked me this by PM, and I have been curious about this as well...
@jkatchy asked me this by PM, and I have been curious about this as well...
@hifijim I wouldn't touch the back chamber on the M74A. No, its not the most inert construction, but its optimized for the driver from an acoustical aspect. Can you do better? Yes, I'm sure. All the back chamber really needs is a piece of dynamat or like dampening material. Thats my view on the whole subject after having played with these drivers and I'm rather picky when it comes to these things.
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In essence all tweeters and midranges can be modified and improved in some way. They are all sealed enclosures. I guess production has to decide what is economical. As DIYers we can go to the n-th degree with refining the enclosure design, and are allowed to get carried away with it.
Thanks!... I was not clear in my question. Assuming I leave the existing back chamber unmodified, is there an advantage to constructing an additional sub-enclosure to isolate the rear of the midrange from the woofer?
No. Not at all, unless you want piece of mind that there are no smaller air leaks behind the mid chamber. As most of people on here know, I had one of my T34Bs come.through with a chamber detached, so now I tend to be paranoid, especially where there's alot of structure born vibration. The glue Bliesma uses isn't the fanciest, so I would at the very least wrap a thin layer of kapton tape around the outer seam where the chamber meets up with the magnet. I also usually play it safe and put a chambered driver in its own small compartment.
The evidence is not clear to me on that one Jim. Some tweeters, if you tap on the back of the chamber are quite resonant, Some manufacturers use decoupling to isolate internal chambers from external chambers. Others decouple midrange from the baffle too.
I've not seen any studies that show the benefit to an added sub-enclosure to midrange or tweeter, in steady state sine waves, let alone the dynamic frequencies and pressure levels seen inside a cabinet during music.
I've not seen any studies that show the benefit to an added sub-enclosure to midrange or tweeter, in steady state sine waves, let alone the dynamic frequencies and pressure levels seen inside a cabinet during music.
OTOH, putting the mid or tweeter in a sealed chamber would do no harm. So why not, if you want total peace of mind on that issue? Even just gluing a cup-like structure onto the back of the baffle at the mounting hole & lining it with dense damping would give you that insurance.
Im really curious about the bliesma 7" domes. I wonder how they pair up to a small horn with the high sensitivity. Could be an interesting match. But the price..... :/
Yes, I have been tempted to bring up the Bliesma M142 in this thread also to see what people think. I have T34Bs, so wondering what to pair them with.
Bill
Bill
Yes: midrange installation including screw holes etc. does not have to be airtight.