The rear elements are fairly directional on their own. When you split them into banks of 4 then they become a pair of even more directional arrays. The idea of the 30 degree angles was to reduce the energy to a wall bounce placed directly behind the system and send more in a left and right direction. That would encourage multiple bounces and a more diffuse sound field from the reverberant energy.
The -9 directivity index applies whatever the exact polar pattern. It determines that the early arriving direct sound is relatively weak compared to the reverberant sound. The question is what is the best proportion of early vs. late energy, and what is the proper frequency balance for the 2 components.
Regards,
David
If I had a couple of 901 cabinets to play with, I would give each of the 4" drivers its own little back chamber with damping & xover them to cut them off at 200 hz, add a front firing tweeter and use most of the volume of the enclosure for a decent sized long excursion bottom firing woofer or two that could possibly be ported down a (widened) support post and radiate at floor level, then xover the whole thing to shitcan the external equalizer.
The 4" Bose drivers have about the same amount of linear excursion as a 2" compression horn driver so would welcome help at LFs as well as at the top end. Your sheetrock won't be rockin' above 5Khz anyway.
The 4" Bose drivers have about the same amount of linear excursion as a 2" compression horn driver so would welcome help at LFs as well as at the top end. Your sheetrock won't be rockin' above 5Khz anyway.
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As far as early vs. late energy is concerned am turning to my Favorite book ( a bit dated but still seems to be full of good info ) Master Handbook of Acoustics by Author ... F.Alton Everest , maybe an answer lies in this book
" If I had a couple of 901 cabinets to play with "
"If I had a couple of 901 cabinets to play with, I would give each of the 4" drivers its own little back chamber with damping & xover them to cut them off at 200 hz, add a front firing tweeter and use most of the volume of the enclosure for a decent sized long excursion bottom firing woofer or two that could possibly be ported down a (widened) support post and radiate at floor level, then xover the whole thing to shitcan the external equalizer."
Unfortunately you would not have enough room inside the cabinet with a Bose 901 cabinet ( especially after series 2 when plastic was introduced..lol....It could be done with a properly designed 3d modeled home built cabinet ( 3d modeled )so you could really tweak the internal volume to what you are after without having to build and re-build till you get what you want.
"If I had a couple of 901 cabinets to play with, I would give each of the 4" drivers its own little back chamber with damping & xover them to cut them off at 200 hz, add a front firing tweeter and use most of the volume of the enclosure for a decent sized long excursion bottom firing woofer or two that could possibly be ported down a (widened) support post and radiate at floor level, then xover the whole thing to shitcan the external equalizer."
Unfortunately you would not have enough room inside the cabinet with a Bose 901 cabinet ( especially after series 2 when plastic was introduced..lol....It could be done with a properly designed 3d modeled home built cabinet ( 3d modeled )so you could really tweak the internal volume to what you are after without having to build and re-build till you get what you want.
Attachments
I don't know. You might be able to get two 8" woofers at the bottom of each cab, especially if you ditch the plastic baffles that aren't doing any sonic favors and rebate the 4" drivers in baltic birch a little closer to the grillclothes. Then you could have Bose with highs and lows.
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I've done a few custom built systems where the midrange drivers were 901 drivers, four off, mounted around a CD driver, they are very efficient and can handle heaps of power (edge wound flat aluminum voice coil wire wound on an aluminum former) and some of the higher MK order cones have rear cone treatments and tapered thickness profile cones to help tame top end response problems..
The plastic baffles are part of a full plastic inner cabinet. It is divided into 3 cavities with one for the front unit and two for the two groups of 4 on the back. All have the same volume per driver and are equally tuned. Cutting into it at all would be very messy and would have to sever the partitions.
No room for a 10" unit here. A better approach would be just to add a subwoofer. It would reduce the large amount of LF EQ normally applied.
David
Dave, are you working for the B..E company now ? I am just aksing because of your location info (Framingham).
Regards
Charles
Regards
Charles
Yes, since November. A good company with a huge investment in engineering and research.
David
So with a huge investment in engineering and research, any variations of the "Flagship" such as back to the wood sealed cabinets or ported wood cabinet or an Audiophile version or the use of higher quality drivers or maybe instead of 4.5" FR a 5 " FR driver instead or a 6.5" FR or 8" FR ....wow 9 - 8"FR version of the flagship maybe with the 200.00 Tang Band drivers ! anything interesting or is the "Flagship" just drifting at sea with little to no R & D ?
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Today I have mastered the not-very-difficult art of measuring impedance using REW and resistors and stuff on hand 🙂
Of interest to me, the Bose pimp, is what is the Fs of this ancient (CTS) driver? I measured a set of seven and get an average of 102.7 Hz. This is quite different from the Fs in the only T-S spec I've ever found (70 Hz)... sure, I could have goofed. But a test resistance (72 ohm) read ok. Now I guess I'm going to have to learn how to measure the entire T-S parameters and settle the matter once and for all 🙂
Of interest to me, the Bose pimp, is what is the Fs of this ancient (CTS) driver? I measured a set of seven and get an average of 102.7 Hz. This is quite different from the Fs in the only T-S spec I've ever found (70 Hz)... sure, I could have goofed. But a test resistance (72 ohm) read ok. Now I guess I'm going to have to learn how to measure the entire T-S parameters and settle the matter once and for all 🙂
Don't throw away any drivers, before checking to see if Freeman-Tuell can recone them.
Freeman-Tuell Speaker Service LLC
Freeman-Tuell Speaker Service LLC
Thanks, Speaker Dave. The -6dB level of rear radiation sounds similar to what Duke LeJeune of AudioKinesis is doing with his latest horn speakers, which have a rear-facing woofer with an array of upwards-facing dome tweeters. I heard the A/B switch (rear radiators on/off) at the last RMAF show and the level sounded about right, adding convincing spatial ambience without degrading image specificity. If I recall right, the imaging got even sharper with the rear radiation turned on, which I thought was a good sign for the overall concept.
The trick seems to be avoiding rear radiation diffracting around the front of the cabinet and contributing a 1~1.5 mSec delayed sound to the front radiation. With careful angling of the rear radiators, and paying attention to their polar characteristics, it seems that the "blur" of sound diffracting around the cabinet can be minimized, at least in subjective terms.
Carefully aimed multidirectional rear radiation isn't what's usually seen with dipoles or so-called "bipoles". If the rear radiation elements are directional, and aimed at reflections on the ceiling and side walls, it'll be delayed enough (6 mSec or more) so it won't interfere with direct sound from the front of the speaker. This is a very different application of controlled directivity ... enhancing spaciousness without affecting the direct sound.
It seems like the most favorable direction for rear radiation is definitely not 180 degrees away from the forward radiation. Some angling to the sides, and the ceiling, illuminates the listening room more efficiently. This could even be simulated with lights behind the cabinet to get a sense of where the rear radiation is going. Hmm ... I wonder if that's what Amar did back in the old days?
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No, Amar had to use candles. The incandescent lamp hadn't been invented yet 🙄
Today I mastered the T-S measurements, which in terms of using REW means "you super-glue a Quarter to the dust cap and take a 2nd measurement." 🙂
Ran T-S tests on three sample drivers. At least the measurements are fairly close. My 72 ohm test resistance still was 72 ohms this morning.
Today I mastered the T-S measurements, which in terms of using REW means "you super-glue a Quarter to the dust cap and take a 2nd measurement." 🙂
Ran T-S tests on three sample drivers. At least the measurements are fairly close. My 72 ohm test resistance still was 72 ohms this morning.
McGee Radio in Kansas City had vast quantities of the 8" Essex woofers from the 301, they could be run in a 2-way with no low-pass filter. They were popular with hobbyists.
soldermizer
72 ohms at 102 hz you've got some dried up crusty speakers there.
these are the cloth surround types?
72 ohms at 102 hz you've got some dried up crusty speakers there.
these are the cloth surround types?
Not that bad at all. The 72 ohms is for three paralleled 220 ohm resistors for a reference. Of about 7 drivers, yes they are cloth surrounds, the blue cone with "Bose" on them, DC resistance is about 7.2 ohms. My Fs measure measurements were between about 90 to 115 Hz and the average was about 106 Hz.
have you considered treating the surrounds and spiders? the lower the Fs the better even in a sealed box.
Oh, my. Bose speakers are so quirky. They are ridiculously overpriced and marketed to dumb as dirt consumers with too much money.
I have owned several sets of Bose speakers in my lifetime, and still have a set of refurbished 301s in service. I also built 901 clones when I was in high school, using 3 8" full range drivers driven by two stereo amplifiers. I know you speaker purists are cringing, and I know why. But set up properly they sounded out of this world with rock music. My snobby older hi fi nerd friends turned their noses up at them (one of them had 901s set up just right which was my inspiration) but almost 40 years later they're still talking about them. In many ways they were a mess but they sure threw out a whole lot of sound.
Placement is critical with many Bose speakers. 301s sound terrible when haphazardly placed. Careful placement will yield mediocre sound. Mine are in my shop, hung from the ceiling. This is how they were displayed at the Bose stores, and this is way better than using the stands.
Their most popular product, the Acoustimass series, has no redeeming qualities whatsoever. Every system I have ever heard was "professionally installed" and every single one sounded so incredibly terrible. It just sounds like echoes to me.
Their waveguide radio is really nice, but the price is beyond stupid.
I have owned several sets of Bose speakers in my lifetime, and still have a set of refurbished 301s in service. I also built 901 clones when I was in high school, using 3 8" full range drivers driven by two stereo amplifiers. I know you speaker purists are cringing, and I know why. But set up properly they sounded out of this world with rock music. My snobby older hi fi nerd friends turned their noses up at them (one of them had 901s set up just right which was my inspiration) but almost 40 years later they're still talking about them. In many ways they were a mess but they sure threw out a whole lot of sound.
Placement is critical with many Bose speakers. 301s sound terrible when haphazardly placed. Careful placement will yield mediocre sound. Mine are in my shop, hung from the ceiling. This is how they were displayed at the Bose stores, and this is way better than using the stands.
Their most popular product, the Acoustimass series, has no redeeming qualities whatsoever. Every system I have ever heard was "professionally installed" and every single one sounded so incredibly terrible. It just sounds like echoes to me.
Their waveguide radio is really nice, but the price is beyond stupid.
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