Improving Bass Response of Altec Bolero 890c

[bdp35]

I recently picked up a pair of Altec Bolero 890c speakers, because I heard they had a big sound in a small package. Well, they definitely impress me, and have seduced me enough to replace my AR 2AX's (which replaced New Large Advents) as my main speakers in my study. They WOW me in everything they do, except for the bass response. I am running them on an all tube system (100wpc monoblocks). I will be installing new caps, but I don't want to mess with the originality of the crossover pass that. I was wondering if anyone out there has any suggestions on mods or tweaks to the speaker cabinet, which would improve the bass of the Bolero (deeper and fuller) . Any advice or tips would be greatly appreciated. Thx!

[NickH]

Hi bdp35,

Welcome to the group. Its good to have another Houstonian here. I doubt you will find any tweaks or mods to improve you bass response. The only thing I can think of is playing with the virtual volume by adding more acoustic insulation if there's room. But its probably not going to get you much if there pretty filled already. I don't know much about them but since there altecs there high sensitivity that also limits the low frequency response.


Nick

[Mr. Widget]

Not a vintage solution, but I'd go with a REL subwoofer... perhaps an LE14 based JBL sub, but not the Performance Series since the plate amp isn't very flexible.


Widget

[bdp35]

Hi bdp35,

Welcome to the group. Its good to have another Houstonian here. I doubt you will find any tweaks or mods to improve you bass response. The only thing I can think of is playing with the virtual volume by adding more acoustic insulation if there's room. But its probably not going to get you much if there pretty filled already. I don't know much about them but since there altecs there high sensitivity that also limits the low frequency response.


Nick

Thanks for the replies. The Bolero cabs are only lined with dampening material, so adding loose dampening material is a definite possibility. I've read (Back-to-Basics Audio by Julian Nathan) that in doing so, it will increase the speakers power handling. Is this true? I've also read that placing a large baffle aroundthe loudspeaker (made out of 3/4 to 1" plywood) would increase the bass response as well, and that Altec did this on many theater models. Any idea what the baffle will look like? I am wondering if anyone has ever tried these things with their Boleroswith positive results?

[Don C]

You will get most of the same effect as the large baffle from putting the speakers up against a wall, or better, in a corner.

[NickH]

Ah, didn't think about corner loading. I'm with Widget though, a sub would be the optimal solution I think.



Nick

[bdp35]

Ah, didn't think about corner loading. I'm with Widget though, a sub would be the optimal solution I think.



Nick

I agree with both of you guys, that adding a modern sub would be the best solution - but, that would be considered cheating - way too easy and no fun!

[Ed Kreamer]

Greetings bdp35,

Years ago I modified a pair of 890C's by adding a mass disc to the passive radiator in a similar fashion to the JBL pr 10. In fact that is where I got the discs. As I recall it did produce better low bass, and it eliminated some of upper mid bass mud. I always like the sound of the 890c. Really good mids and highs.
But the ultimate solution is to add a VLF speaker.

Ed

[bdp35]

Greetings bdp35,

Years ago I modified a pair of 890C's by adding a mass disc to the passive radiator in a similar fashion to the JBL pr 10. In fact that is where I got the discs. As I recall it did produce better low bass, and it eliminated some of upper mid bass mud. I always like the sound of the 890c. Really good mids and highs.
But the ultimate solution is to add a VLF speaker.

Ed

Hmmm... interesting. What size, and how are they attached? Do you have a link where I can order them? BTW, I do have a PSB sub-woofer if I am not satisfied. Goal is to keep my power sub in 5.1 surround system (with Klipsch) for movies intact, and my music listening system (with the Altec's) as a two channel.

[Ed Kreamer]

The discs were made of a molded paper like cardboard, and were attached by a machine screw to another disc glued to the inside of what would have been the voice coil former. You could select how many discs to use depending on where the system was to be tuned. The more discs, the lower the tuning. As to where to get them, I think you'll have to build your own. suitable material( like a very thin 1/8 plywood ) might be available at a craft store such as Michaels or maybe a model airplane store.

When I did it, it took several times, adding or subtracting discs, as it was trial and error.

If you look on page 5 of the 1980 speaker building manual in the technical section you will see how they worked on the PR 15, which was exactly like the PR 10.

Good luck and have fun.

Ed

[bdp35]

I've opened up my speakers, and I noticed something odd. One speaker has a horn marked 21517-3, and the other is marked 21517-1. What's odd is the one marked 21517-1 has a much shorter neck (1 1/2" shorter) than the neck on the 21517-3. Did Altec do this, and would the shorter neck sound different? I was told by the gentlemen that I purchased them from that the speakers were all original. I also noticed that the interior of the cabs are not lined with damping material, and it doesn't appear it was removed or ever had it. Aren't all of the Bolero cabs lined, or should be lined?
Thanks!

[thundermud]

I am in the same boat as well. I just installed new caps and love these speakers however I would like to try adding mass to the PR, anyone have specific/detailed instruction on how to do this? I feel
there is some upper mid bass mud I would like to get rid of. For the record the speakers are completely filled with dampening material, guess that's the way they came?

[CORYK]

I've opened up my speakers, and I noticed something odd. One speaker has a horn marked 21517-3, and the other is marked 21517-1. What's odd is the one marked 21517-1 has a much shorter neck (1 1/2" shorter) than the neck on the 21517-3. Did Altec do this, and would the shorter neck sound different? I was told by the gentlemen that I purchased them from that the speakers were all original. I also noticed that the interior of the cabs are not lined with damping material, and it doesn't appear it was removed or ever had it. Aren't all of the Bolero cabs lined, or should be lined?
Thanks!

May I ask what the ink stamp was on your 10 LF drivers? 406-8c or 406-8y ? Thanks!

[Ed Kreamer]

Colleagues;

As to the fiberglass fill in the boxes; yes they were filled with a pink fiber glass damping material. As to the horn; Altec used 2 versions of the Heppner(sp?) horn. I think someone other than the factory swapped it. The longer version is the one you want for the 890c. The shorter one was used on the Madera I think it was called. These can be found occasionally on our favorite bidding site. The 406 was a good speaker, although not terribly good for low bass. I preferred it over the 414 12 inch woofer. As for the tuning, please see my previous post. Lowering the tuning will clean up the mid bass some as I recall, but that was 40+ years ago. 40 years? Oy veh how did this happen?