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Old 12th July 2009, 04:09 PM   #11
art64 is offline art64  United States
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I have Bose 901 series V which I bought back in 1985. I have modded them to work as direct firing speakers. I replaced the back heavy cloth with wide gap nylon screen so that the sound will not be blocked. I turned the speakers around so all 8 speakers are facing forward. I mounted them to the wall using CRT TV wall mounts that can be adjusted horizontally and can be tilted up or down. They sounded like different speakers. The highs are alive and the sound dispersion is so wide that it feels the room with sound quite nicely. Hardly a hot spot or dead spot. Later on I augmented the sound with Klipsch subwoofer and a BBE 362 Sound Maximizer. Wow. The Denon Reciever that I've been using is only 100 watts per channel but no need to drive the amp all the way now. The sound is full, excellent mid range and highs. Voice sounds are incredible that sometimes it gives me goosebumps listening to the artist singing. I've never heard Michael Jackson's voice that different when he was singing his love songs. Totally sounded different. The songs are 20-30 years old and never heard them sounded like that. I almost gave up on these 901's. But not anymore. I just want to share the experience.
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Old 12th July 2009, 05:01 PM   #12
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Ironic how so many extensively designed things end up working better at something else or in a way not intended. I'll have the option of turning each of my 901's in which ever way I choose and they will be high up, sitting on 4' tall woofer enclosures, just below ear height while I'm standing.

I suppose from a geometrical stand point having them turned around and the baffles being ~120 degrees the dispersion is similar to how it is first reflected off of the back wall. It will come down to what sounds better after all options are tried regardless of the theory or design. This has been my experience with most of the things I've built so I try to incorporate that into my ideas, leave room for adjustment and try not to be too proud to ignore it when it happens.

How far are the speakers spaced from each other, the wall behind behind them, side walls, the floor/ceiling, the listener etc. ?
What are the dimensions of the room?
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Old 13th July 2009, 12:05 AM   #13
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I've consider this design before. Back in the day, there was a speaker component company that was selling Bose Clone kits. Though the speakers were nothing special. I had a friend who bough the array of speakers and the cabinet design plans and made some pretty good speakers considering how cheap they were.

But with that speaker combination they were an impedance nightmare. The worked fine at normal indoor party volumes, but for outdoor parties, they kept shutting down the amp.

I always assume a better configuration would have been three speakers on each side in the back, and two speakers spaced across the front for a total of 8 speakers. That at least would result in a reasonable final impedance.

But then I took it one step further. What if you used a combination of 4" and 3" full range speakers. Then combined one or two tweeters on the front.

The tweeter could either be in combination with all the speakers, so one 8 ohm tweeter with a gang of 8 midbass. Or, one 4 ohm tweeter with each gang of two 4" midbass, meaning two 4 ohm tweeters on the front.

The idea was that with the 4" full range, you could get a trace more bass extension with them. The result of adding the tweeter is obvious. If one wanted to cheat a bit, you could add one of the Piezo tweeters and skip the crossover. Though Piezo tweeters typically need a little taming.

So, in the two tweeter configuration, the tweeters would be combined with the larger full range speakers, and in a separate gang, the 3" full range would stand alone.

As an example, the Tang Band 4" (264-812) has a low end of about 65hz. The similar Tang Band 3" (264-812) has a response of about 100hz. 65hz isn't great, but it is some improvement. That would give you a resulting speakers with a 65hz to 20khz response.

These alternate Tang Band 4" and 3" (264-828, 264-844) speakers have corresponding low ends of 60hz and 105hz.

So, using 8 speakers, and making half of them 4", and mounting two of the 4" on the front, plus tweeters on the front, should certainly make a reasonable full range system.

This is never going to have great bass response with those small speakers, but it could be made acceptable, or more acceptable. I've got some cheap bookshelf speaker that have a rated low cut off of 80hz, though they also have a response bump above 80hz, and they actually sound like they have pretty good bass - all things considered.

If a person really wanted to put some money into it, a better quality full range like the Fostex might work better.

Me, I'm always looking for a way to do it on the cheap.

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Old 13th July 2009, 12:27 AM   #14
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From what I've read about Bose philosophy is that only 11% of what you hear at a live concert is direct sound, the rest is reflected sound that reaches you at different times and from varying angles. Thusly 11 + 88 = 99 so 1 + 8 = 9 or 9 drivers. I figure 3 drivers, two on the back and one on the front, with the front padded down a bit could produce the same percentage split and still be plenty loud enough.

The tweeters I plan to eventually use are Linaeum dipole ribbon tweeters that will simply mount on top of each 901 enclosure. They look like a figure 8 from above and radiate in almost a 360 degree pattern. I'll cross these over kinda high with just a cap, 1st order. I may even put these on the same channel as the 901's and use an L-Pad to keep them from screamin'.
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Old 13th July 2009, 02:10 AM   #15
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Holt sussed it out quite well on Page 3 here:
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Old 13th July 2009, 05:05 AM   #16
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I question the 11/88 ratio. It is not that I don't believe it as far as it has been stated, but I have to assume there is a huge context to it.

It would seem that every theater or large venue would have different acoustics. It also depends on where the measurement were taken in the venue. In front of the PA, is not the same as the balcony. Also, whether there were people there are the time the measurements were made. A full venue sounds very different than an empty venue.

Also, how did they make these measurements, and how did they determine what was direct sound and what was reflected sound. There are a lot of details left out of that basic 11/88 statement.

Further, I would think different styles of music would produce different levels of reflection. Soft acoustic, even with a PA, would seem to have fewer reflections than heavy metal, if based on nothing else than sheer intensity of sound.

Also, a living room is not a concert hall. It doesn't have the same space or acoustics.

Still, I'm not trying to discredit the basic 11/88 assumption, just saying that there are likely an endless list of variables and qualification to that particular fact.

If you want lower frequency response, you have to use bigger speakers. If you want a drivable impedance, then it has to be closer to the center of the 4 ohm to 16 ohm range. If you want better high frequencies, then you need a tweeter.

Based on my rough (very rough) calculations, using my design, we have about 25.14 InČ of speaker in the front, and about 39.36 InČ of speaker in the rear. Giving us a ratio of 1.00 to 1.57 (front to rear). That may not approximate a concert hall, but it does give better direct sound, lower frequency response, better impedance, but still with a degree of reflected sound that would give the music a sense of spaciousness.

It also allows you to wire the speakers so they are mechanically In-phase, which I think would be an improvement.

No it is not the exact design concept of the Bose 901, but we seem to have agreed that that design did not work all that well. But it is a similar design, based on similar design concepts, and would likely work better.

But, since I have never built it, I can't say with any certainty.

Again, not disputing the 11/88 concept, just concerned about the long list of missing variables and qualifications that go with it.

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Old 13th July 2009, 09:28 AM   #17
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When William Wright first went to M.I.T. he found that as a foreign student, he was restricted as to how much he could earn. In his sophomore year, he started a small company named Wright Electroacoustics where he was able to employ other students to build equipment. There, he became aquatinted with Dr. Ted Hunt who was editing a revision of his book. Interestingly enough, Arthur Janszen had worked for Dr. Hunt at Harvard's acoustics' research lab. Meanwhile, at M.I.T., an undergraduate student was designing a 'full range' ionic wind speaker. The resultant ozone damaged his lungs! (In the 1980's, Nelson Pass of Threshold wow were exhibiting at the Las Vegas Riviera, attempted the same. He had to be treated at the hospital, for lung problems.) One of the serious audiophiles there was David Klepper, who was working on his degree. He later went with Bolt. Beranik and Newman. Another was Dr. Bose who was attempting to build a spherical speaker by using an array of 4" speakers. He made a bid on a 'lot' of redundant Fisher stock as Fisher had ceased production of a small High Fidelity radio. But the 'lot' apparently involved more speakers than anticipated and The Bose Direct-Reflecting Speaker was the result. Even so the bass response was a little weak and a lot of Heathkit Preamps were converted to bass-boost equalizers. One of Dr. Bose' subcontractors was Bud Fried who was operating an Audio Store in Philadelphia located in City Line Center. But I digress.
in DAYTON WRIGHT - History and Background
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Old 13th July 2009, 01:31 PM   #18
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I think the design accomplished part of what it intended to do and used the EQ to force the rest.

If someone were to try and factor in the endless variables they would never build any speaker as they would never be able to settle on a design. I think the 11/88 ratio may be somewhat general or averaged but like any design after its built, the theory don't matter no mo, it either works well or it doesn't.

Let me refine my OT question. In the midrange frequencies, does the Bose901 accomplish a spaciousness and fullness that other speakers do not?

If I were to build something similar to a 901 I think it would be advantageous to have some sort of fader or L-Pad incorporated so as to adjust the 11/88 ratio. Your design, Blue Leader, with an L-Pad between the front and the back would allow adjustment for the direct/reflected ratio. I know its bad to try and pad woofers but what about mid rangers? Or is it the frequency range in question that determines it?

It would be very ironic if the 901 was a result of the combination of events described in your quote Inductor but it wouldn't be the first idea to be born in such a way.
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Old 6th November 2009, 01:07 PM   #19
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I just stumbled into this thread looking up info on the EQ used for the 801 speakers. I found a single 801 in the trash the other day. I picked it up thinking it might make a good midrange speaker for my bass guitar rig. I have an odd little Trace Elliot amp that features a slot loaded 10" woofer and a bullet tweeter. It gets great lows and highs but no mids.

The 801 is missing all the foam surrounds on the speakers, but I see there are kids for this. I haven't checked to see if the speakers are good yet.

Anyway, I figured I post this just to show how you can take something meant to be used in a different way and find some use for it.
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Old 6th November 2009, 05:05 PM   #20
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Really nice DavidSchwab,
In another note, I got some 301's that I'm changing (their signature) for a rubber surround from Goodhifi (.com) Netherlands.
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