Refoaming
I had used a pair of 901s for many years and had refoamed them but not with the kit on eBay. Honestly, I think the original suspension sounded a bit better. I changed the internal wiring to a single strand of KIMBER 4TC and also the crappy caps in the EQ to better but not so called "audiophile" grade ones. Well, its sounded I think much better in terms of clarity. Its strange people say there's no bass! Many people told me the 901s sound bad and I found out that most of these guys acquired them used WITHOUT THE EQ!!!! Now, the 901s reeeeally sounds bad without the EQ, not enough of everything!!! I am now using an pair of Eminent Technology LFT8s which is in a totally different league but I would say that the 901s ain't that bad but you need a listening area with walls in the right place otherwise the sound falls to pieces. However, I would say that imaging is its weakness as it plays on reflected sound! I read Bose bashers every where on the net but come on, if a product can sell for two decades, either the product is decent or you have a bunch of "audiophile clots" in America!! You can cheat everybody some time but not everybody every time! So do give refoaming a go! Its not really that difficult. I used paint thinner sparingly to remove the old foam which can be scraped off easily after they soften. Maybe you may even like the sound. Let me assure you that I know what music is all about and its strange to find reviewers saying a Compo sounded better!! I would say if its pin-point imaging and accuracy you're after, then nope! its not your cup of tea but if you want musicality without picking nits, give it a shot! Afterall, I have found a load of raved about so called audiophile products that actually sounded so so and equiment costing much less could easily out do them. For those curious, I run a Goldmund TT with Mcintosh amps and find hifi is fun when you explore with an open mind!! My 2 cts
I had used a pair of 901s for many years and had refoamed them but not with the kit on eBay. Honestly, I think the original suspension sounded a bit better. I changed the internal wiring to a single strand of KIMBER 4TC and also the crappy caps in the EQ to better but not so called "audiophile" grade ones. Well, its sounded I think much better in terms of clarity. Its strange people say there's no bass! Many people told me the 901s sound bad and I found out that most of these guys acquired them used WITHOUT THE EQ!!!! Now, the 901s reeeeally sounds bad without the EQ, not enough of everything!!! I am now using an pair of Eminent Technology LFT8s which is in a totally different league but I would say that the 901s ain't that bad but you need a listening area with walls in the right place otherwise the sound falls to pieces. However, I would say that imaging is its weakness as it plays on reflected sound! I read Bose bashers every where on the net but come on, if a product can sell for two decades, either the product is decent or you have a bunch of "audiophile clots" in America!! You can cheat everybody some time but not everybody every time! So do give refoaming a go! Its not really that difficult. I used paint thinner sparingly to remove the old foam which can be scraped off easily after they soften. Maybe you may even like the sound. Let me assure you that I know what music is all about and its strange to find reviewers saying a Compo sounded better!! I would say if its pin-point imaging and accuracy you're after, then nope! its not your cup of tea but if you want musicality without picking nits, give it a shot! Afterall, I have found a load of raved about so called audiophile products that actually sounded so so and equiment costing much less could easily out do them. For those curious, I run a Goldmund TT with Mcintosh amps and find hifi is fun when you explore with an open mind!! My 2 cts
Here, here on the EQ unit. Even a little messing around with the EQ will mess up the clarity. I think most people don't realize that it's supposed to work like some kind of outboard XO.
Even though I think Bose is expensive for the quality, it is not bad and I cannot fault the pair sitting in my friends living room. As I said... excellent for delivering good party, better than most cartable PA bins I've heard. And certainly better than anything I've heard from PSB or Energy.
ensen.
Even though I think Bose is expensive for the quality, it is not bad and I cannot fault the pair sitting in my friends living room. As I said... excellent for delivering good party, better than most cartable PA bins I've heard. And certainly better than anything I've heard from PSB or Energy.
ensen.Ron E said:
They were always coated, but the stuff they used to coat them with was pretty similar to yellow wood glue! Not really flexible, and after a time leaks would develop.
I think it is quite possible that they have gotten better since then, since there is certainly nothing inherently wrong with making a woven fabric matrix covered with a flexible sealant.
However, I do not know if the sealant situation has gotten better since back then. Do you know for a fact it has? And if so, what do they coat the fabric with now?
For a party, yes. For accurate reproduction of sound, no.
Let's be clear what we're talking about here. And to those who inevitably will pipe up and say its not worth trying for accurate reproduction, or prefer colouration or inaccuracy in whatever form tickles their fancy - good for you, I wish you the best of luck achieving the sound you like. Be aware however that most of us ARE trying for accurate reproduction, so by our standards, grossly coloured or inaccurate speakers that nonetheless sound more pleasing to the ear in some way, are still bad speakers.
Even if your preference tends towards that kind of sound, there are, IMO, far better ways to get it than with Bose. It seems to me you could build a 901 clone using some nice cheap widerange drivers, say, Tang Bands, and get a similar effect, possibly with no EQ, for a lot less $$$ and hassle than rebuilding vintage 901s or buying new ones.
Before you replace the surrounds, look at them and see if they need it. If the foam looks rotten and flakes off when you scratch it with a fingernail, it needs replacing. If not, you are simply driving the speakers too hard and you need a subwoofer to handle the low bass. Those little cones were never meant for ultra-low frequencies at high volumes.
PS - when your dad gets his new 5.1 Bose system, he'll probably wish he had never given you the 901s. Those are the only halfway decent speakers Bose ever made. The new home theater systems suck big time. I mean c'mon, a single 5" woofer to handle the bass for the whole system? Eighteen 4" drivers, while not great, are a heckuva lot better than one 5" driver.
PS - when your dad gets his new 5.1 Bose system, he'll probably wish he had never given you the 901s. Those are the only halfway decent speakers Bose ever made. The new home theater systems suck big time. I mean c'mon, a single 5" woofer to handle the bass for the whole system? Eighteen 4" drivers, while not great, are a heckuva lot better than one 5" driver.
catapult said:
I would say he needs it.
Click the link in this post to see for yourself:
http://www.diyaudio.com/forums/showthread.php?postid=533931#post533931
Bose(o) said:
Thank you very much for your decision to do this.
I think it will be very interesting for the forum to know this.
And as another poster said, who knows-maybe clones with cheaper/superior speakers might be a possibility?
After all, with series-parallel wiring, the eight 8 ohm or 4 ohm woofers wouldn't all have to be in series, the way 1 ohm woofers would.
PS: You might try physically removing the front speaker, and one of the back. Leave both hooked up electrically. Then run a signal from a signal generator, (http://www.satsignal.net/ click Audio Tools ), and measuring the voltage across the terminals of the front speaker, and the voltage across one of the back speakers.
It would be interesting to see how much wattage the front speaker gets, compared to one of the back speakers.
Well, I am a bit surprised. Now, I only measured up to 10kHz. because the RS SPL meter tends to be inaccurate above that point. Anyway, I don't think measuring any driver with original foam matters with these results.
I will be measuring T/S specs when I buy another Voltmeter since someone decided to throw mine out. (I am NOT happy!)
I will be measuring T/S specs when I buy another Voltmeter since someone decided to throw mine out. (I am NOT happy!)
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Here's a better graph for ya folks
An externally hosted image should be here but it was not working when we last tested it.
It might be interesting if you downloaded Speaker Workshop and posted a measurement using your RS SPL meter as a microphone. You use a RCA to miniplug cable (one side of a stereo miniplug to RCA - the thing for connecting a walkman or portable CD player to a receiver) and connect from the RCA connector of your RS meter to the line input (not the mic input) on your soundcard.
I made a cal file for the RS SPL meter by comparing it against my Behringer ECM8000 - it is essentially the same as the one you can download from ETF acoustics...
I made a cal file for the RS SPL meter by comparing it against my Behringer ECM8000 - it is essentially the same as the one you can download from ETF acoustics...
Bose(o):
Thanks for making the graph. Not great response up to 10KHz, but I guess it could be worse.
Here is a page which gives the readings for the output of three different Radio Shack SPL meters. Not just the modifications, but the readings as to how the SPL meter performs right out of the box. So if you want to go up to 20kHz, you can do it.
http://www.gti.net/wallin/audio/audio.html
By the way, what is the part number of your Radio Shack meter?
Thanks for making the graph. Not great response up to 10KHz, but I guess it could be worse.
Here is a page which gives the readings for the output of three different Radio Shack SPL meters. Not just the modifications, but the readings as to how the SPL meter performs right out of the box. So if you want to go up to 20kHz, you can do it.
http://www.gti.net/wallin/audio/audio.html
By the way, what is the part number of your Radio Shack meter?
This is a graph of the ETF Acoustic calibration file for the RS SPL meter. My analog meter measures much the same, but the response is less smooth. Brown line is SPL, yellow is phase.
http://www.etfacoustic.com/micpreamp.html
The corrections on the wallin page are very rough and probably meant for band limited noise. Measurement equipment like Speaker Workshop, LspCAD or SoundEasy - or others - will need a "real" cal file such as the one provided by ETF Acoustic. Even then, there is enough unit to unit variation to make the resulting measurement +/-2 at best.....
http://www.etfacoustic.com/micpreamp.html
The corrections on the wallin page are very rough and probably meant for band limited noise. Measurement equipment like Speaker Workshop, LspCAD or SoundEasy - or others - will need a "real" cal file such as the one provided by ETF Acoustic. Even then, there is enough unit to unit variation to make the resulting measurement +/-2 at best.....
Attachments
Just reading Eric Wallin's adjustments for the digital 2055 SPL meter, I would take the few minutes to do the modifications as he spells it out, then send to Digi-Key for that mic capsule.
For amateur speaker testing, do you really need accuracy above 17 kHz, especially if you know it's 3 dB down at that point?
For amateur speaker testing, do you really need accuracy above 17 kHz, especially if you know it's 3 dB down at that point?
kelticwizard said:
First, I highly doubt the digital meter is much different in mic response from the analog one - they were made concurrently for many years and probably use the same capsule. I wouldn't trust third octave amateur corrections over a cal file, either. The DIY preamp and DIY mic described at Wallin's pages will work if you are a true DIYer, but they will not be much cheaper than the setup I describe below - perhaps you will spend $50 when all is told, and you have no guarantee that it will work unless you are experienced with circuits.
I wouldn't make any adjustments that affected the functionality of my meter in the way that the mods he described for the RS meter would. My meter's output is quite noisy, which is not good for a measurement rig, but it works in a pinch if you don't really care about accuracy.
If you want more accuracy, the cheapest ($80) way to go is to get a Behringer ECM-8000 and UB-802 (and for a further step up get it calibrated by Kim Girardin for about $40, IIRC). The UB-802 can do double duty as a small mixer for Karaoke or whatever else you might want to use it for
A follow-up!
So waaaay back before we got to the Bose debate and all these graphs, I had this problem with my Bose 901's and came here looking for advice. Here's what I did:
Ordered the CLOTH surround kit from Simply Speakers (~$60 on eBay).
With my dad, scraped and swabbed the old foam out. The foam was so brittle we just took a hand vaccuum cleaner and sucked most of it straight off. The rest came off with rubbing alcohol.
Installed new surrounds.
Spilled glue and rubbing alcohol all over the place.
Cranked the suckers up.
WHOLE NEW SOUND! Not only is the rattle gone, but the sound overall is so much richer and fuller than before.
The whole job, including prying off the staples off of one front panel (we'd done the other one a few weeks ago), took about 4 hours with 2 people working side by side. So I'd imagine if you're doing this yourself it would take in excess of 8 hours.
So I guess to all you hard core types, a simple surround job isn't a whole lot to shout about, but I came here without a clue and now have a lot more knowledge (and yes, skepticism about Bose) and a rockin' set of 901's. Now my kids can listen to the 1812 Overture just like I remembered it. At least we're excited and proud of ourselves.
Happy New Year,
Mark
So waaaay back before we got to the Bose debate and all these graphs, I had this problem with my Bose 901's and came here looking for advice. Here's what I did:
Ordered the CLOTH surround kit from Simply Speakers (~$60 on eBay).
With my dad, scraped and swabbed the old foam out. The foam was so brittle we just took a hand vaccuum cleaner and sucked most of it straight off. The rest came off with rubbing alcohol.
Installed new surrounds.
Spilled glue and rubbing alcohol all over the place.
Cranked the suckers up.
WHOLE NEW SOUND! Not only is the rattle gone, but the sound overall is so much richer and fuller than before.
The whole job, including prying off the staples off of one front panel (we'd done the other one a few weeks ago), took about 4 hours with 2 people working side by side. So I'd imagine if you're doing this yourself it would take in excess of 8 hours.
So I guess to all you hard core types, a simple surround job isn't a whole lot to shout about, but I came here without a clue and now have a lot more knowledge (and yes, skepticism about Bose) and a rockin' set of 901's. Now my kids can listen to the 1812 Overture just like I remembered it. At least we're excited and proud of ourselves.
Happy New Year,
Mark
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