A few questions about amplifier & Bose 901 speakers

[Gene Cho]

Hello, fellow members!

I have a few questions about my Bose 901 series IV and SONY entry-level integrated amp STR-DH 130, 100 wpc. I'd really appreciate if someone can give me good advice.

I believe my Bose 901 with equalizer have blown up my NAD 3020 and a SONY higher-end integrated amps during the past years (Not 100% sure, but I became to realize only recently after I read posts from 901 users. I had thought those amps were faulty.)

I recently purchased the cheap SONY amp (STR-DH130) but am afraid of connecting Bose 901 to this amp. I'm currently connecting to Bose 141, a small speaker set.

My questions are
1. Has anyone been using EQ with a cheap integrated amp without a problem?

2. If I connect Bose 901 WITHOUT the equalizer, would that be OK? (I've read the EQ is the culprit that causes trouble rather than the speakers.)

3. What would you recommend for little bookshelf speakers (possibly with stands) instead of Bose 901 at used price under $300? I mostly listen to classical/vocal music at low to mid volume. In 1990s, I really liked the vocal expression of Bose speakers, and I probably still in impression that their vocal expression sounds great to me. But with my blown-up SONY amp (a mosfet amp at $1500 original,) I always felt lacking bass.

I really don't want to blow this amp again, and I thank you for all your valuable opinions!

Thank you.

 

[gdmoore28]

I've done about a half hour of searching for problems with 901 eqs that could wreck an amplifier, and I found none. Zilch. Not even at the repair sites. Some of these eqs are getting around 45 years old, so many problems are going to exist purely because of aged components. But amplifier killers? I can't find any.

Here's an idea, though. Contact this guy at DHS Speaker Service. He specializes in 901 eq repair and upgrades. Tell him the questions you have about possibly destroying your amplifier. If it's possible, I'll guarantee you he knows about it, and can advise you.

http://stores.ebay.com/DHS-Speaker-Service?_trksid=p2047675.l2563

or

http://www.dhsspeakerservice.com/

GeeDeeEmm

 

[OMGCat!]

I've never heard or Bose eqs causing a problem for amps but that doesn't mean it can't happen.
You don't want to use the speakers without the eq, they will sound very bad.

As for small bookshelves that do great with vocals I'd wholeheartedly recommend B&W. You won't find any new at that price but their older models hold up extremely well and they are known for their excellent mid range.They do like stout amplification however so your Sony might not be a good fit.

 

[dshoaf]

You're not going to have a problem connecting up the Bose 901IV EQ to that little Sony receiver. There's even a Tape In/Out where it can be connected easily. Here are a few things, though, to think about:

1) Power specs for the Sony are optimistic: It is rated at 100 wpc - but at 1Khz only and at 1% distortion. These are miserable specs intended for a buyer who doesn't care. This means that the Sony will, actually be closer to ~50 wpc, I'd estimate. This is enough, however, for a set of Series 4 901s in many rooms.

2) Poor audio back through the signal chain: But even with a more realistic derating of specs, the 901s w/EQ are going to allow you to hear back through the audio signal chain to it. With a good source, and the ability to rotate in a higher performance amp, it will quickly be clear what the real problem is.

3) Your room size: This is going to be the biggest variable - well, that and how loud you typically listen to music. If the room is small, you'll do fine with the items listed above being the limitations.

As for the EQ, assuming it is working ok, the internet blog-o-sphere is mis-leading you. They're quite high quality but, as GDM mentioned, it could use a refreshing but not until you move on to a different receiver/amp.
Lastly, on the use of 901s without the EQ, there's plenty of threads here at AK on that topic. Short answer: 901s without the EQ will result in poor sonic quality. It a speaker _system_ so use it that way.

Cheers,

David

 

[Gene Cho]

I've done about a half hour of searching for problems with 901 eqs that could wreck an amplifier, and I found none.

Hmm.. I've read warnings or experiences that Bose 901 EQ distorts the signal too much to make bass and treble from its small full range speaker units, and could damage amplifier, if amp's power is not enough. The pages might have been removed or something? I don't know, but I was worried because my two amps did get damage with Bose 901. The amps could have been faulty, but I had used NAD 3020 for a couple of years with another speakers without any trouble, but it stopped working a couple days after I connected 901. Thanks for the links! I don't know if I want to spend more money on Bose system. I would rather buy a different speaker set if I have to spend more money.

As for small bookshelves that do great with vocals I'd wholeheartedly recommend B&W.

I once owned B&W speakers long time ago. I agree they're great for vocal music, but from my taste, it was just too neutral and especially I didn't like string sound. Not sure if it was due to my amplifier- I used a McIntosh 3050? Don't remember the model name. It had two dials on front panel with fans on the back to cool the heat.

You're not going to have a problem connecting up the Bose 901IV EQ to that little Sony receiver. There's even a Tape In/Out where it can be connected easily.
As for the EQ, assuming it is working ok, the internet blog-o-sphere is mis-leading you.
David

Thank you, David! I really hope that the posts that I've read were not based on actual technical facts, and the problem was from somewhere else, as three of you here suggested. I'd be really glad because except for the lacking bass, I enjoy the sound of 901 in our small room. Due to my experiences for these years with 901 and the pages that I've read, I became to think that 901 did damage my amps.

 

[dshoaf]

Nope. About the only way a speaker could damage an amp is:

1) Shorted or frayed stranded wire jumping the speaker terminals _and_ the amp doesn't have short circuit protection _and_ isn't fused.

2) Excessively low impedance, which draws too much current from the amp _and_ the amp doesn't have over-current protection or is not fused.

There are far more failures of the speaker due to failing amps! In my ~7 years as a Bose Warranty Repair Station back in the 70s, I _never_ saw a failed amp with a root cause being the 901s. That applies to the Series I, II, III, or IV. Further, I _never_ had to work on an 901 EQ.

If you had amp failures, it wasn't because of the 901s. Sorry to bust that myth but I've got the experience to back it up.

One last thing on the Series IV 901s: The driver are connected in series. This means that, if one driver becomes damaged and the voice coil opens. The speaker simply stops operating since the series connection has now been broken.

Cheers,

David

 

[Gene Cho]

If you had amp failures, it wasn't because of the 901s. Sorry to bust that myth but I've got the experience to back it up.

One last thing on the Series IV 901s: The driver are connected in series. This means that, if one driver becomes damaged and the voice coil opens. The speaker simply stops operating since the series connection has now been broken.

I'm very glad to hear that! I started to like Bose speakers in 1993? when Eric Clapton's unplugged album was released and had international hits. I was in Tokyo at that time and most music stores like Virgin record in Shinjuku used Bose speakers and the sound was fantastic! I think that strong impression still remains in me and might make me a bit biased in favor of Bose

One driver makes noise sometimes from left speaker and I fix it by pushing the cone a few times to realign it and the noise is removed most of the time. This should be fine, right?

Thanks!

 

[dshoaf]

Take some pictures of the drivers and post them here. If one is rubbing, the foam surround is likely bad. This is the most common problem with the older Bose speakers. Pictures will help the arm-chain bench techs diagnose what you have.

The Bose support engineers had us run a frequency sweep on any speaker returned for any reason as the best way to find problems like you report.

Cheers,

David

 

[Schurkey]

My 901Vs have been powered by a 35-watt receiver for a decade. Volume control tends to hang in the 2--3 range.

HOW LOUD are you playing? How big is the room? The equalizer will boost the bass considerably, could run the amp into clipping. If the driver surrounds are rotted, I expect the speakers will need even more power to maintain a given volume.

Sure, I can imagine a failed component in the equalizer causing problems. Anything can break. Doesn't seem to be common, though.

 

[bshorey]

The 901's will sound like crap without the EQ. I'll take a guess at how the Bose EQ could contribute to amp problems.

My understanding is that the EQ works by greatly cranking up the bass and treble. Given that, an artificially boosted bass curve would cause the amp to produce a lot more power than the volume knob might indicate. I.e., the amp could be delivering full power with the volume knob at 1/3 or 1/2 indicated volume.

I think that as long as you're aware of this, and are sensitive to clipping or distortion, then there shouldn't be a problem. But this is all just my theory.

HTH,

bs

 

[BilboBaggins]

I can see a pair of Bose 901 series 4 with EQ driving a NAD 3020 so hard that it eventually blew the amp. Think about all that current the amp needs to supply in order for the speakers to sound reasonably good, and then try to think of a 20 wpc amp trying to supply that kind of power. Depending on a number of things like soft clipping smoothing things out even more, and I could see the amp getting clipped to death. First off, I don't think it's very good practice to run an amp of such low power with a speaker know to draw lots of power. It's just asking for trouble. Personally, I think Bose shine most with 100 watts or more. Anything less, and it will not sound optimum.

I've never had any other speakers than Bose 901s that can cause my 1801 to peg!

 

[Gene Cho]

Take some pictures of the drivers and post them here. If one is rubbing, the foam surround is likely bad.

I had a typo: it's the speaker unit, not the cone that I push to temporarily remove static noise from one speaker - I learned that trick from a member in this forum some time ago.
I can upload a picture tonight, but I believe woofer cones looked OK-sorry for the confusion.

My 901Vs have been powered by a 35-watt receiver for a decade. Volume control tends to hang in the 2--3 range.

HOW LOUD are you playing? How big is the room? The equalizer will boost the bass considerably, could run the amp into clipping. If the driver surrounds are rotted, I expect the speakers will need even more power to maintain a given volume.

Thanks for the info and sharing your experience. My room is small and the volume won't go higher than 50% most of the time. I'll keep in mind not to raise the volume too high.

I can see a pair of Bose 901 series 4 with EQ driving a NAD 3020 so hard that it eventually blew the amp.

Yeh, I understand NAD 3020 might have been too less powered to run 901, but I still don't know another SONY mosfet amp (TA-F707ES) with 100 wpc that smoked and died was due to its own problem or by 901. But with the opinions here from experienced users, I think it was probably due to its own problem. I bought it off eBay and it went through several repairs, so it was probably not in good condition.

 

[Gene Cho]

Take some pictures of the drivers and post them here.

I finally hooked up the EQ and 901 to the amp and auditioned, but something is very wrong. The sound is dull and distorted, and the EQ doesn't work.

I think I connected correctly because I've done this before:
From EQ input (in "connections to amplifier" in EQ) to Tape Out in amplifier
From EQ output to Tape In in amplifier.

My source is from PC through Soundblaster Omni USB then CD input in amplifier.

I don't know if I'm missing something here, but changing base or treble in EQ doesn't make any change in the sound and the sound is so dull and distorted.

I have some questions:
1. Am I doing something wrong? Should I select Tape in source selector in the amp? I guess not-there's no sound if I do so. Maybe these tape in and out in the amp is not actual tape loop?
2. Can my EQ be mal-functioning? It worked fine with the previous amp before it smoked.
3. Or just the amp and speakers don't match well? I think I have normal ears to identify sound quality, and the sound is so distorted-I've rarely heard this dull sound.

Not sure if I need to return this amp or if I need to sell off my Bose 901 and EQ then buy another speakers. I'm uploading front and back image of the amp. I really appreciate your help here!

 

[JoeESP9]

I'm not certain but your amplifier does not seem have a tape loop or pre out main in jacks. Without either there is no way to connect the equalizer.

 

[dshoaf]

What does the description of the MD/Tape in the Owners Manual say about it? From a signal chain standpoint, the Tape loop must be further down from the CD input. This way, with the Tape loop engaged, the signal is routed through the Preamp.

Sounds like the EQ is wired correctly.

Cheers,

David

 

[whoaru99]

The amp probably does not have a true tape monitor circuit.

Likely gonna have to find something else to use the 901s with. Something with a true tape monitor, processor loop, or pre out/main in.

 

[Gene Cho]

What does the description of the MD/Tape in the Owners Manual say about it? From a signal chain standpoint, the Tape loop must be further down from the CD input. This way, with the Tape loop engaged, the signal is routed through the Preamp.

Sounds like the EQ is wired correctly.

Cheers,

David

The Owners manual doesn't say much about it. Just copying the whole section for the part:

Recording using thereceiver
You can record sound from an audio/video equipment using the receiver. Refer to the operating instructions supplied with your recording equipment.
1 Press the input button which corresponds to the playback equipment.
You can also use INPUT SELECTOR on the receiver.
2 Prepare the playback equipment for playing.
For example, insert the CD you want to
copy into the CD player.
3 Prepare the recording equipment.
Insert a blank MD, tapeor video tape into the recording equipment (connected to MD/TAPE AUDIO OUT or VIDEO AUDIO OUT jacks).
4 Start recording on the recording equipment, then start the playback equipment.
Notes

• Sound adjustments do not affect the signal output
from the MD/TAPE AUDIO OUT or VIDEO
AUDIO OUT jacks.
• While the source is being recorded, the auto
standby function of the receiver may start up and
interrupt the recording. In this case, set the
“AUTO.STBY” to “STBY OFF” (page 27).
• You can record the sound from the video
equipment connectedto this receiver. However,
you cannot record the image via this receiver

 

[Gene Cho]

The amp probably does not have a true tape monitor circuit.

Likely gonna have to find something else to use the 901s with. Something with a true tape monitor, processor loop, or pre out/main in.

That's what I think.. I bought this amp because I thought this one had the tape loop from the picture of the back panel. But even considering the importance of EQ, the sound from 901 is just terrible with this amp.. It has never been this bad without EQ with previous amps, even with NAD 3020 with such low power.

 

[dshoaf]

That's what I think.. I bought this amp because I thought this one had the tape loop from the picture of the back panel. But even considering the importance of EQ, the sound from 901 is just terrible with this amp.. It has never been this bad without EQ with previous amps, even with NAD 3020 with such low power.

This means that it isn't - yet- installed in the signal chain. In other words, it is bypassed. The instructions are pretty useless from a technical standpoint, IMHO. Any way to find a schematic or block diagram? That's what's needed here.

I see from the instructions, however, there's both a video and a Tape/MD loop. I didn't see the jacks for the video, tho, leading me to believe it isn't as easy to patch another device into the signal chain with this receiver.

Essentially, it appears that the amp cannot support sending an audio signal out the TAPE OUT while waiting for the audio to return via the TAPE IN. This is what a 'loop' or a 'patch' is. Most newer receivers and amps don't need to accommodate patching so they're not well supported for that.

Cheers,

David

 

[Schurkey]

I finally hooked up the EQ and 901 to the amp and auditioned, but something is very wrong. The sound is dull and distorted, and the EQ doesn't work.

Wild guess: The sound is dull and distorted BECAUSE the EQ doesn't work.

I think I connected correctly because I've done this before:
From EQ input (in "connections to amplifier" in EQ) to Tape Out in amplifier
From EQ output to Tape In in amplifier.

Seems right.

My source is from PC through Soundblaster Omni USB then CD input in amplifier.

Does your "Soundblaster Omni USB" output a line-level signal? If the source isn't line-level, the CD input on the receiver is going to be useless.

I don't know if I'm missing something here, but changing base or treble in EQ doesn't make any change in the sound and the sound is so dull and distorted.

If the tone controls on the equalizer don't affect the sound, the equalizer is either non-functional, or not connected properly. Is the equalizer pilot light lit when you're trying to use this system?

I have some questions:
1. Am I doing something wrong? Should I select Tape in source selector in the amp? I guess not-there's no sound if I do so.

You will have to engage the tape loop if you want the equalized signal to be amplified by the receiver. If you don't have the tape loop engaged...the equalizer is not going to be effective.

Maybe these tape in and out in the amp is not actual tape loop?

The amp probably does not have a true tape monitor circuit.

How is a "MD/Tape" Audio Out/Audio In not a tape loop? Same for the "Video" Audio Out/Audio In--that's the second tape loop. I don't understand how an out/in wouldn't be a usable tape loop.

Essentially, it appears that the amp cannot support sending an audio signal out the TAPE OUT while waiting for the audio to return via the TAPE IN. This is what a 'loop' or a 'patch' is. Most newer receivers and amps don't need to accommodate patching so they're not well supported for that.

My God, that would be screwed-up. I can't imagine any reputable company providing the jacks, but not the usability.

'Course, we are talking about Sony. I wouldn't walk across the street for new, free Sony gear, and Toshiba may be even worse. Even so, I'd be more likely to believe that it's plain defective, and not designed that way. So perhaps the tape loop doesn't work properly.

2. Can my EQ be mal-functioning? It worked fine with the previous amp before it smoked.

Sure. Seems unlikely, though.

3. Or just the amp and speakers don't match well? I think I have normal ears to identify sound quality, and the sound is so distorted-I've rarely heard this dull sound.

Nope. What you're hearing isn't normal operation. SOMETHING is wrong, and you haven't gotten it figured out yet.

I would expect you need whichever source you want to listen to (CD input, from your prior description) engaged, as well as the tape loop that the equalizer is connected to--either the "MD/Tape", or the "Video" loops. Different receivers will allow--or not allow--the two tape loops to interact in evil ways, so make sure the other loop is not engaged.