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Bose 901 series I active equalizer DIY
Bose 901 series I active equalizer DIY
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Old 17th October 2013, 01:16 PM   #11
Fast Eddie D is offline Fast Eddie D  United States
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I built a hard wired equalizer circuit for my 301s. They are hanging in my shop. The biggest limitation they have in my setup is dynamic range and dynamic compression. They sound decent in my system.

Everybody that hears them can't believe it. People that have 301s always ask why theirs don't sound like mine. I just tell them that it's because I hung them from the ceiling, just like the display in the store.

Bose 301s and 901s do need a decent amplifier. Without that, they will sound thin and anemic. I'm driving mine with an old Nakamichi Stasis amp that I got for free and repaired myself. The Nak can deliver big current. Without good current reserve, the Bose speakers will fall flat on their face if you try to play them loud. They are very inefficient, they have a very ragged frequency response, their impedance varies from 3 ohms to 9 ohms not counting woofer resonance (yes I measured mine), and the 301s really don't handle a lot of power. The reps that do the store setups know all this and they know how to make them sound good in the store. (Not allowing A/B comparison to other more capable speakers helps too.) You can do everything they do in the store at home if you have the knowhow, money, and space. (Not having a female around helps too because females hate big speakers and intrusive installations.)

I thought that my equalizer was simple, but the Bose one linked to is way simpler than mine. That would be easy as pie to build.
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Old 17th October 2013, 02:11 PM   #12
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Bose 901 series I active equalizer DIY
Default uploaded BOSE 901 schematic

uploaded BOSE 901 schematic
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File Type: png bose_901-I_eq_schem.png (802.6 KB, 292 views)
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Old 17th October 2013, 02:39 PM   #13
zobsky is offline zobsky  India
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Okay, ...
I believe I can add something to this discussion.

I've tried a couple of methods of equalizing the 901 (series II):
1. Implementing EQ (and optionally room correction) via a INUKE DSP amp.
2. Using the original factory EQ.

I could get method (1) to sound decent but never as good as (2).

Also, as already mentioned in this thread, .. the 901 (especially the series I and II) need power. I've tried various amps including a modest NAD C720BEE (50WPC), Mcintosh MC2100 (105 WPC) and a INuke 3000DSP (about 400 WPC, I'm guessing) and only the INuke managed to wake them up. I didn't believe that the difference would be that large
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Old 17th October 2013, 03:30 PM   #14
4Torr is offline 4Torr  United States
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The original Bose EQ sounds better than a multi-band equalizer because it has only 2 peaks - near the treble and bass extremes. From the peak at the bass, the slope is smooth down to the midrange and then goes smoothly back up to the treble peak.

On a graphic EQ, each slider introduces a peak or valley in the frequency response which gets nastier as the gain or cut is increased.
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Old 17th October 2013, 04:06 PM   #15
Fast Eddie D is offline Fast Eddie D  United States
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Quote:
Originally Posted by zobsky View Post
Also, as already mentioned in this thread, .. the 901 (especially the series I and II) need power. I've tried various amps including a modest NAD C720BEE (50WPC), Mcintosh MC2100 (105 WPC) and a INuke 3000DSP (about 400 WPC, I'm guessing) and only the INuke managed to wake them up. I didn't believe that the difference would be that large

901s can sound great if set up properly. If they are placed haphazardly in an acoustic environment, they will not sound so great.

Are they accurate? Certainly not. If you measured their specs, they would look positively lackluster. Even with EQ they do not go over 15 kHz. They roll off sharply below 80 Hz. But set up properly, around two feet from a wall and corners, without furniture or curtains anywhere near them, they give a subjective soundstage that is very pleasing when playing rock (especially live recordings!) or "pop" music. Is it real? Not at all.

They require gobs of power to sound good. At the Bose store (I know guys, I know) the salesmen used to wire them up to a power chord and plug them into a wall socket (120 V). It's super cheesy I know, but the amazing fact is that they took it- the salesman would hook them right back up to the distribution center (amplifier used is apparently a well guarded secret) and they didn't skip a beat.

I made some "knock off" 901s in high school. I used three 8" full ranges; two rear facing and one forward facing. I used an Electro Voice horn tweeter up front (had to pad it way down of course). I had a long, folded vented port facing the rear. Since my tube amp had multiple output taps, I was able to wire the three speakers up to the multiple taps. These babies really rocked! All the drivers, crossovers, and L-pads cost under $100 in the 70s.

Just FYI, Parts Express sells replacement drivers for the 901s (I think they fit other models too). Replacement Speaker Driver for Bose 901 4-1/2" 1 Ohm 290-922 They are 1 ohm drivers, so DIY applications are limited. Us wise guys could build an amplifier to drive them though.

Last edited by Fast Eddie D; 17th October 2013 at 04:11 PM.
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Old 17th October 2013, 04:32 PM   #16
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Bose 901 series I active equalizer DIY
Quote:
Originally Posted by 4Torr View Post
The original Bose EQ sounds better than a multi-band equalizer because it has only 2 peaks - near the treble and bass extremes. From the peak at the bass, the slope is smooth down to the midrange and then goes smoothly back up to the treble peak.

On a graphic EQ, each slider introduces a peak or valley in the frequency response which gets nastier as the gain or cut is increased.

I did not suggest or recommend a graphic EQ.
I would not for this application.

I did say that you could make the equivalent or better EQ using a modern DSP based EQ or perhaps a parametric EQ.

It's important to discern between the different methods.

Assuming you can duplicate the curves there should be nil differences.
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Old 9th November 2013, 11:08 PM   #17
Soldermizer is offline Soldermizer  United States
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Good to see another Bose fan. I've been a fan of the Series I and II for years now. Having had a Behringer DEQ2496 "before" I got into 901's, I have always used it -- or later, a MiniDSP 2x4 -- to do the room EQ + EQ curve at the same time. This works perfectly. I just sold my last Bose (Series II) EQ on Ebay -- I hardly ever used it. Yes, you can use a regular old GEQ too but you'll get best results with 1/3 octave, PEQ and/or some test gear. Look for my other posts here if you want to see how I do it. Unlike 1968, amp power is stupid cheap nowadays, if you can bring yourself to say "Behringer" or similar

Of course, many are here for the thrill of DIY. So go ahead and build a clone of the active EQ. But you will do a lot better -- and easier and more flexible -- with even a $20 used 10-band octave EQ. Yes, that works ok too.
Of course, you can buy the original thing on Ebay too...
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Old 12th November 2013, 03:57 AM   #18
zobsky is offline zobsky  India
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Quote:
Originally Posted by Soldermizer View Post
Good to see another Bose fan. I've been a fan of the Series I and II for years now. Having had a Behringer DEQ2496 "before" I got into 901's, I have always used it -- or later, a MiniDSP 2x4 -- to do the room EQ + EQ curve at the same time. This works perfectly. I just sold my last Bose (Series II) EQ on Ebay -- I hardly ever used it. Yes, you can use a regular old GEQ too but you'll get best results with 1/3 octave, PEQ and/or some test gear. Look for my other posts here if you want to see how I do it. Unlike 1968, amp power is stupid cheap nowadays, if you can bring yourself to say "Behringer" or similar

Of course, many are here for the thrill of DIY. So go ahead and build a clone of the active EQ. But you will do a lot better -- and easier and more flexible -- with even a $20 used 10-band octave EQ. Yes, that works ok too.
Of course, you can buy the original thing on Ebay too...
Can you post your minidsp config or screenshots?
Thanks
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Old 12th November 2013, 05:18 PM   #19
Soldermizer is offline Soldermizer  United States
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Default my tutorial

http://bmmoser.myweb.usf.edu/shared/...%20MiniDSP.doc

This has my unique curves. If you want the default Bose Eq curve I can send it or just search on the net.
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Old 12th November 2013, 08:07 PM   #20
zobsky is offline zobsky  India
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Thanks,
To date, I've been able to get the minidsp 2x4, using (REW, a UMik to generate biquads, and manually tweaking from there) to sound close to the original bose eq,.. but never quite as punchy. I'll give your document a read and try again.
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