Zenith Allegro 3000 Speakers - Surprising!

[onwardjames]

Yep, I had those way back. Got ‘em new from Elm Radio, a local haunt for $40. Floor models. They really worked nicely for an 8th grade kid. Wish I had a pair now for old times’ sake.

I know that YOU KNOW QUALITY. I spun some tunes thru my buddy's pair yesterday while visiting him, and I gotta say, they sure check many boxes. Great, open and airy sound, solid low end, imaging. Not just a great "intro" speaker......an actually good set of speakers.

I just wonder how much more performance could be squeezed out of them. Anyone think a quality crossover might improve them?? I think the woofer is just allowed to roll off around 2500 hz.

You are likely fine. I wouldn't do it unless the woofers were stiffened the way mine are. I don't think yours are the same woofer as mine. I have stripped one of the pair and I made some comparative measurements this morning. I will post the data later.
John

John, I really appreciate your tutelage. These aren't mine, they're my friend's, and I wanna do them right. Thanks!

 

[kevintomb]

I got a set of drivers on Ebay, made new boxes that did not vibrate, replaced Tweeter 3uf cap, and tried them out for several months.

At first, really like them a good bit for what they were (low priced vintage speaker) and found them far better than some claim, but after a few months.....

I started to really notice they were not all "that" great.
They were quite sensitive for sure, and could play fairly loud easily and with no strain at all.
They have great mid bass!

But while the tweeter sounded fairly good, the upper end of the woofer around 1500-2500 Hz was not that great, and somewhat strident sounding.
It was noticeable especially if one removed the tweeter and played Pink Noise on just the woofer.

The lack of a crossover at all on the woofer, for sure, caused this problem.

I could EQ the 2000hz band down about 3-4 db and then it was "okay" sounding, but still lacking somewhat.
I think just the idea of a biggish 10" woofer, with no crossover is the issue.

The other issue, the Woofer requires a VERY big box to do true Deep bass.

With my 1.8 cu ft box,(Same size as original Zenith box) it would do down to maybe 45-50 hz fine and then not a lot below that.

I have heard the same woofer used in a much larger console, (about 3.5-4 cu ft per woofer) and the bass was FAR deeper and powerful.

 

[onwardjames]

With my 1.8 cu ft box,(Same size as original Zenith box) it would do down to maybe 45-50 hz fine and then not a lot below that.

Altec 19's don't do much below that (IIRC) and nobody's complaing about them.

Thanks for giving your experience with these. If you could post some pics of the boxes you built, I think that'd be very interesting.

Also, I agree, if the crossover weren't just a simple cap, and maybe someone could put the parameters in a program, come up with an improved crossover design, plus perhaps adding more box, we might find out what these babies can do.

 

[kevintomb]

Altec 19's don't do much below that (IIRC) and nobody's complaing about them.

Thanks for giving your experience with these. If you could post some pics of the boxes you built, I think that'd be very interesting.

Also, I agree, if the crossover weren't just a simple cap, and maybe someone could put the parameters in a program, come up with an improved crossover design, plus perhaps adding more box, we might find out what these babies can do.

Not great looking mind you! Just made up quick to get an idea of what they would sound like. 1.875 cu ft. Tuned to 42hz with the port.

Mine had a cap and coil on tweeter and a variable level control. (the original layout)
Nothing at all on woofer, running free.
Sort of embarrassed to show them. Not bashing on them, I liked them in a way, but I guess just not great, more like sorta good!

 

[onwardjames]

Not great looking mind you! Just made up quick to get an idea of what they would sound like. 1.875 cu ft. Tuned to 42hz with the port.

Mine had a cap and coil on tweeter and a variable level control. (the original layout)
Nothing at all on woofer, running free.
Sort of embarrassed to show them. Not bashing on them, I liked them in a way, but I guess just not great, more like sorta good!
View attachment 2138823

Thank you for providing this. While these aren't some sort of giant slayers, with a good clean amp (friend is using a lowly Realistic ST-84, and it sounds ridiculously good) they really punch far above their weight.

Did you put much fiberglass or polyfill in the boxes? Might help upper bass region. Also, I defeated the pot for the tweeter, always ran it full range anyway. That seemed to make a significant difference.

 

[kevintomb]

Thank you for providing this. While these aren't some sort of giant slayers, with a good clean amp (friend is usi

ng a lowly Realistic ST-84, and it sounds ridiculously good) they really punch far above their weight.

Did you put much fiberglass or polyfill in the boxes? Might help upper bass region. Also, I defeated the pot for the tweeter, always ran it full range anyway. That seemed to make a significant difference.

Yes, put a decent bit of polyfill for sure. It helped.

I get what you are saying, and agree, not audio perfection, but really great bang for the buck!

They play really loud and quite clean, with low watts.
I almost believe they are under rated as far as sensitivity, and seem to be 91-92 db with one watt.

 

[onwardjames]

They play really loud and quite clean, with low watts.

This. My friend's bone-stock Realistic ST-84 receiver sat in a dank basement for years. I cleaned it up, lubed everything, but not being much of a tech, left it alone. With only 30 or so rated watts, it plays these speakers louder and cleaner than I would ever need.

Like you said, great bang for the buck, indeed.

 

[Romeo Wolf]

Bought a pair of Allegro 3000's, the one with the non-removable covers and square ports.


I've always wanted a proper pair for years, and now I've got some to enjoy, play around with, and experiment

 

[roger2]

Just an FYI to anyone interested in the Allegro speakers. The '70s models, like those pictured above by Romeo Wolf, used at least three different woofers, as well as three different versions of the Foster tweeters. I mention this because T/S parameters posted will be different for woofers from different manufacturers. The '70s Allegros have been much discussed at diyaudio.com and that information can be searched. The Allegros posted by onwardjames and kevintomb were later ('80s?) models, about which I know nothing

I have two pair of the '70s 3000, one of which has been recapped and cabinets braced, and one pair of the 2000 with 8" woofers and the Foster tweeter.

I did some frequency response readings of the recapped 3000 Allegros, along with about a dozen other speakers. In my testing it appeared that the tweeter crossover design has it running a bit hot, meaning that the tweeter was a bit louder than the woofer. Two layers of acoustic foam placed over the tweeter brought its output very close to the output of the 10" woofer. They sound good either way though.

 

[Romeo Wolf]

Just an FYI to anyone interested in the Allegro speakers. The '70s models, like those pictured above by Romeo Wolf, used at least three different woofers, as well as three different versions of the Foster tweeters. I mention this because T/S parameters posted will be different for woofers from different manufacturers. The '70s Allegros have been much discussed at diyaudio.com and that information can be searched. The Allegros posted by onwardjames and kevintomb were later ('80s?) models, about which I know nothing

I have two pair of the '70s 3000, one of which has been recapped and cabinets braced, and one pair of the 2000 with 8" woofers and the Foster tweeter.

I did some frequency response readings of the recapped 3000 Allegros, along with about a dozen other speakers. In my testing it appeared that the tweeter crossover design has it running a bit hot, meaning that the tweeter was a bit louder than the woofer. Two layers of acoustic foam placed over the tweeter brought its output very close to the output of the 10" woofer. They sound good either way though.

The ones I had tested featured the textile dome foster horn tweets. I'll need to see about the woofers though.

 

[roger2]

As for the Foster tweeters there are three types that i am aware of:
1) red cloth-looking dome
2) silver metal-looking dome
3) bullet
Some of the frames are metal, some plastic I don't recall which is which

The different woofers, as far as I know, are all made by different manufacturers but were of similar (good) quality. Again, anyone who wants to really dig into this can google search here on AK and particularly on diyaudio.com

Also, I don't know of any way to remove those grills without destroying them. To be fair though, I didn't try all that hard On the 3000s that I recapped and braced, I simply tossed the grills. When I did the frequency response testing mentioned above it was with no grills, which could/would have made the tweeter output hotter to some unknown degree. In other words, the speakers might actually sound better with the grills intact, ugly though they may be.

@Romeo Wolf is that pic you posted all your gear, or the seller's?

 

[CoogarXR]

I haven't heard a pair of Zenith Allegro speakers that I didn't like. I just flipped a pair of 3000's and I thought they sounded great! Nice and crisp. The woofer doesn't go super deep, but it's punchy. And that horn tweeter adds that crispness. I liked em.

 

[roger2]

crisp is a good word for their sound
I like them too

 

[kevintomb]

Just an FYI to anyone interested in the Allegro speakers. The '70s models, like those pictured above by Romeo Wolf, used at least three different woofers, as well as three different versions of the Foster tweeters. I mention this because T/S parameters posted will be different for woofers from different manufacturers. The '70s Allegros have been much discussed at diyaudio.com and that information can be searched. The Allegros posted by onwardjames and kevintomb were later ('80s?) models, about which I know nothing

I have two pair of the '70s 3000, one of which has been recapped and cabinets braced, and one pair of the 2000 with 8" woofers and the Foster tweeter.

I did some frequency response readings of the recapped 3000 Allegros, along with about a dozen other speakers. In my testing it appeared that the tweeter crossover design has it running a bit hot, meaning that the tweeter was a bit louder than the woofer. Two layers of acoustic foam placed over the tweeter brought its output very close to the output of the 10" woofer. They sound good either way though.

I have heard both the older and newer versions, but in full disclosure, really hard to remember how they sounded in comparison, as it was over 20 years ago.

I have also heard the 70s version in a huge console, and THOSE did sound different. Still efficient, but with much more deep bass and more boomy sounding overall. Highs were not all that clear or airy sounding. But the console accented the bass due to a much larger air volume and a built in "Loudness" compensation.

 

[Romeo Wolf]

As for the Foster tweeters there are three types that i am aware of:
1) red cloth-looking dome
2) silver metal-looking dome
3) bullet
Some of the frames are metal, some plastic I don't recall which is which
@Romeo Wolf is that pic you posted all your gear, or the seller's?

Mine's the variant with the red textile dome tweets. I wonder if perhaps they're an early version?

The Allegros are now mine, the rest of the gear is up for grabs as I was at a record store where I bought them. They have loads of audio equipment in the back



They're huge, but they provide good lower bass and they shake my small 8' x 8' cube. Only issue is there's buzzing in the left woofer when bass is being reproduced, but it doesn't sound like the voice coil is rubbing or anything since the bass remains clean.

 

[roger2]

If it isn't the voice coil, that buzzing could be something vibrating. There aren't too many parts, but possibly something is a bit loose.

Some of the Allegros had removable backs, some did not. If the back is removable it could be buzzing, or anything really. The crossover, the vent, the short wood strips on the front panel that secure the vent and that you can't get to without removing the grill, the woofer mounting, the screws or nuts holding the woofer or tweeter, etc. If the back is not removable then you will be limited in where you can search for the problem. Visual inspection as well as "hands-on" probing while the buzzing is audible...

I don't know for sure about the chronological sequence of the different tweeter styles. If I had to guess I would go with what I posted above.

In an 8x8 room you will get cabin gain that will augment the bass.

 

[roger2]

I have a pair of 10" woofers from some old Allegro speakers. They are nicely made but the treated accordion surrounds are quite stiff. I managed to soften one up a bit by scrubbing with acetone using a toothbrush and paper towels.....

You are likely fine. I wouldn't do it unless the woofers were stiffened the way mine are. I don't think yours are the same woofer as mine. I have stripped one of the pair and I made some comparative measurements this morning. I will post the data later.
John

I am curious whether you might have any follow-up information? Do you still recommend this surround softening procedure, and do you have any test data? Those accordion surrounds are stiff for sure.

 

[WaynerN]

I found a pair of these at a garage sale this last summer for free. I passed on them because the vinyl covered cabinet looked like hell. I suppose I could have put some veneer on them......oh well.

 

[Romeo Wolf]

If it isn't the voice coil, that buzzing could be something vibrating. There aren't too many parts, but possibly something is a bit loose.

Some of the Allegros had removable backs, some did not. If the back is removable it could be buzzing, or anything really. The crossover, the vent, the short wood strips on the front panel that secure the vent and that you can't get to without removing the grill, the woofer mounting, the screws or nuts holding the woofer or tweeter, etc. If the back is not removable then you will be limited in where you can search for the problem. Visual inspection as well as "hands-on" probing while the buzzing is audible...

I don't know for sure about the chronological sequence of the different tweeter styles. If I had to guess I would go with what I posted above.

In an 8x8 room you will get cabin gain that will augment the bass.

So I checked for any air leaks or the cover letting loose, and it turns out there isn't any air leakage. The buzzing is actually coming from the woofer itself, either its very slightly blown or there's a loose connection somewhere, or something

Of course, I could always return them since I have a 100 day return guarantee.

 

[roger2]

Is the back not removable so you can investigate inside? If the buzz is coming from the woofer then yes, I would return them. Those Allegro 3000s are easy to come by. The 2000 (8" woofer, same tweeter) less common, but sound very nice too, perhaps better in some ways than the 3000. You'll likely come across a chance (or more) at another pair.