Infinity Primus 150 spinorama measurements (CTA-2034)

[Ageve]

Here are some measurements of the Infinity Primus 150 Bookshelf speaker.

The MSRP was $198/pair back in 2003.

Specifications:

Frequency range: 58Hz - 20000Hz (+/- 3dB)
Recommended Power: 10 - 100W
Sensitivity: 88 dB
Nominal impedance: 8 ohms
Crossover frequency: 3300 Hz; 24dB/octave
Low-frequency driver: 5-1/4" (130mm) MMD
High-frequency driver: 3/4" (19mm) MMD
Weight: 13.5 lb (6kg)


My measurements are quasi-anechoic, with near-field port+woofer, corrected for baffle edge diffraction, combined with gated measurements at 1m distance.

I have attached a 1m vs 2m comparison, pair matching and measurement axis comparison for those who are interested. I used the speaker with the smoothest response for the spin.

Recommended listening height is with the tweeter "approximately at ear level" according to the user manual. I got the flattest response ~40 mm below tweeter axis, so that's what I used for the spin.


Here's the CTA-2034 data:

It looks surprisingly good considering how inexpensive this speaker was. Most of the response errors should be fixable with EQ thanks to the smooth directivity.


Early reflections:

Horizontal, and total early reflections:

Estimated in-room response:

Quasi-anechoic response:

Horizontal directivity:

0-90 deg compared to measurement by John Atkinson:

Infinity Primus 150 loudspeaker Measurements

Sidebar 3: Measurements

www.stereophile.com

Vertical directivity:

Near-field response:

Steep roll-off thanks to the 24dB/octave crossover, but there are clear port and/or cabinet resonances, and a woofer resonance at ~8 kHz.

Distortion:

< 1% THD from 75 Hz and up. Very low tweeter distortion (less than 0.1%).


Comparison with Stereophile, 30 deg horizontal listening window:

Overall, I'm quite impressed by this speaker. It sounds better than most of the budget speakers I have measured so far. Sure, it's not perfect, but frequency response is ok, horizontal directivity is excellent, and distortion is quite low as well.

There's no deep bass though. A subwoofer is definitely needed.

 

[uwotm8]

I'm quite impressed by this speaker. It sounds better than most of the budget speakers I have measured so far. Sure, it's not perfect, but frequency response is ok, horizontal directivity is excellent, and distortion is quite low as well

That is VERY interesting! What's your subjective opinion on their sound, what's good and what's not so?

The very interesting part is here: back in the days when Primus was current and selling, it was sort of despised and oftenly considered cheap junk. At the same time, a lot was sold and used price was - at least a few years ago - very low as well. According to this one would never think these can be even remotely good.

There were some concerns about enclosure

And AFAIR a lot of used are selling with dead/damaged/replaced tweeters (kinda a weak point).

Does it sound sligtly V-shaped? Some complains were about that, again, if mind serves me well.

Unfortunately I never heard them presonally.

 

[Ageve]

I don't know if Infinity were highly regarded back in the day, but Stereophile seemed to like this speaker as well. I dont usually pay much attention to subjective reviews, but in this case I agree with their conclusion. At it's best, it sounds surprisingly open and detailed, especially on female vocals.

The Primus 150 has achieved a standard of performance at the $200-or-under price point that I didn't think was possible. Moreover, in the area of its greatest strength, its midrange detail and low-level dynamic resolution, it sounded like a $1000/pair speaker.

It was backed up by measurements as well:

Although I was a little bothered by its midrange resonances, the Primus 150's overall measured performance is excellent, considering the Chinese-made speaker's bargain price.

Infinity Primus 150 loudspeaker Measurements

Sidebar 3: Measurements

www.stereophile.com

The overall tonality could be described as a bit "cold", but not really v-shaped - It doesn't sound bright, but a bit thin due to the lack of bass below 80 Hz.

As for the cabinet resonance att 300 Hz, it could be audible, but maybe not. Those kinds of measurements are done with an accelerometer attached to the cabinet. It's not an acoustic measurement.

I bought these speakers after reading the Primus 360 review by Erins Audio Corner. I know this one is probably not as good, but still a nice budget speaker.

 

[Matias]

That is an excellent design, specially for the price. Bass could reach deeper, sure, but directivity is beyond reproach.

 

[AnalogSteph]

Nothing all too unexpected for a budget speaker, I agree.

That woofer is really crying out for a series notch to take out the ~8.3 kHz breakup mode, which would also address the worst of the distortion peaks (~2.8 kHz H3, ~1.7 kHz H5). A metal membrane woofer might not have been the smartest choice for a budget speaker of limited XO steepness. I don't think the importance of proper breakup mode suppression with these was widely understood until some time in the 2000s or so.
The woofer XO could use some tweaking in general (some skimping on L going on?), and the tweeter seems the tiniest bit hot so may not mind a hair more series resistance.

Some stuffing should address the port resonances, although the position of the BR tube near the woofer may not leave an awful lot of space in between.

The cabinet seems a bit excited in the mid-hundreds of Hz, nothing that a bit of bracing couldn't fix I guess. Have seen worse either way.

I wonder what kills tweeters in these... ferrofluid? No ferrofluid and low electrical XO steepness (acoustic looks plenty OK but the waveguide would figure into that as well)?

The first H3 peak around 2 kHz seems peculiar. Issues like that have been caused by really strange things in the past, like loose wires or air leaking between tweeter and waveguide. A nearfield measurement of THD on both drivers may bring some illumination.

 

[DanielT]

Good job Ageve. Results as I suspected. In the thread below the Primus series is discussed. In #11,#15,#16 in the thread test results of Primus 250 and Primus 150 are reported (puffreis test results).

The thread also contains quite a few other tips on good budget speakers/subwoofers.In addition, here is a quote from the same thread,#5

"I-or, a technical consultant in acoustics and audio technology, about Erin's test and the Primus series:

It would have been nice if Harman wanted to revive the dormant Infinity brand and evict more than decently good-sounding three-way speakers for under SEK 15,000 ($1430) per pair. Unfortunately, they make significantly more money selling Revel speakers with slightly higher performance, nicer boxes and a completely different margin.

The Primus range is among the greatest finds on the HiFi market. For the Primus 360, it is really only a rather high lower limit frequency (however, it can be equalized for a lower limit frequency of approx. 35-37 Hz in a room) and a somewhat messy vertical dispersion that can be criticized. I would also guess that the port exhibits some turbulence problems, which are not revealed in the measurements. Otherwise, the performance is of a high class, although I would have liked to see even a little less distortion.

(I have the sister model Primus 150 standing on the computer desk (modified with plugged ports, back-angled, equalized and with together with bass (subwoofer) modules (boxes/speakers)) .... sound perfectly acceptable and have been with me for over 20 years without the slightest problem.)
.....
Primus 360 stands out quite a bit. The smaller Primus models are not quite as good, even though they offered high sound quality per krona ($) when they were new and nowadays some ten times (the value price-sound ratio) more than this on the used market today. Dispersion and distortion are good/okay."

Infinity Primus 250 discussion

Does anyone know about these Infinity Primus 250 floorstanders? There's a set available close to me for $100. Of course I can't find reputable reviews and especially not measurements. I'm sure it would be a healthy upgrade from the Panasonic Thrusters that I had that has a woofer not working...

audiosciencereview.com

The Primus 250 I bought for hardly any money at all is now used by my elderly parents and they are very happy with them.

 

[Spkrdctr]

Back in the day (1980's to 2005 or so) Infinity made some fairly good speakers. I heard a lot of them side by side with other much more expensive higher end brands and for some reason the Infinity's always sounded better overall. This was strictly A/B in the audio stores but it held true nearly every time. It might have been distortion or something else that made me think they always sounded so good. If Amir had been testing them we would know what the magic sauce was! I was listening to floorstanders and they usually had much better overall bass than other pricier speakers. I admit I have a soft spot in my heart for Infinity floorstanders but without any real Amir style testing, I can't say why. I wish some company could bring back the Infinity name and produce speakers in the Polk/SVS range. Not super cheap but low enough price that most people can afford them. Plus they would need massive bass, as I love rich full bass. No bass weaklings. I know, it is not that important with subs nowadays. But still, I like pants flapping bass.

 

[Juhazi]

Infinity Primus 360 Speaker Review

Infinity Primus 360 Speaker

www.erinsaudiocorner.com

I have the low budget Alpha 20 and 5 2-ways, purchaced as HT kit in 2004. Excellent value but problematic port resonance! The small 8" subwoofer has troubles to make 40Hz...

 

[Doenerkunde]

Current market price for used pairs in Germany is 50-80€ and availability is good. Pretty attractive as an upgrade for an all in one Yamaha Pianocraft type compact system. Or paired with a cheap Class-D amp for secondary TV setups. Or as a childs/teens first setup. Or for people who inherited/found an old amp and want to try it out.

Many use cases, so I'm thankful for the review! Driver layout makes me suspect that the Infinity Beta series might also perform decent. Would also be interesting to see how the Primus 250 performs.

 

[tw 2022]

another good speaker from infinity in the "vintage" era of 20 years ago.. if you guys remember: Erin did the primus 360 tower with similar results .. it seems these really are budget revel clones..edit : i have the infinity crescendo 3600's from the mid 90's.. they would hold up against most anything in today's under $1000/pr market , and they take to eq fairly well ...

 

[Cadillacofminds]

This compression gonna be audible in not-large rooms, listening to music with plenty of bass? Maybe the driver's compressiom behavior is a significant shortcoming?

 

[tw 2022]

View attachment 436945
This compression gonna be audible in not-large rooms, listening to music with plenty of bass? Maybe the driver's compressiom behavior is a significant shortcoming?

i was thinking that a sub is a given at this price point for critical listening..., plus that compression doesn't look like a deal breaker (to me) at that level.. most of the problem is sub 200 hz, at high output......

 

[markanini]

Back in 2003 these represented a very good value for objective performance. The measurements here show that this opinion was justified IMO. Plenty of cork sniffers wanted to dismiss them too, but that's par for the course.

 

[tw 2022]

Current market price for used pairs in Germany is 50-80€ and availability is good. Pretty attractive as an upgrade for an all in one Yamaha Pianocraft type compact system. Or paired with a cheap Class-D amp for secondary TV setups. Or as a childs/teens first setup. Or for people who inherited/found an old amp and want to try it out.

Many use cases, so I'm thankful for the review! Driver layout makes me suspect that the Infinity Beta series might also perform decent. Would also be interesting to see how the Primus 250 performs.

i had the alpha bookshelf speakers for a while.. they were decent, but they had some audible "hollow" sound that i would now describe as lower mid suck out.. if anything they tended to be , to my ears a bit bright.. the beta's were reported to be extremely similar in f.r. ....

 

[SMc]

I'm happy to see these measurements! I purchased 150s inspired by the Stereophile review long ago but they stayed in the closet due to a slight harshness despite their other good qualities. Today they're in my bedroom system and with a subwoofer and Denon 760h room correction I'm happy with them.

The woofer cone breakup and the high frequency lift might be explanation enough for my earlier perception. Maybe the Denon manual graphic eq is worth a try around that 800 Hz area.

 

[DSJR]

Not sure if we ever had this range over here (and they'd have doubled the US price anyway if so).

Tweeter failure? I bet it's not really the tweets at all, but cheap weedy amps hard clipping at parties or whatever, which regularly killed many Mission tweeters and even entire speakers back then!

 

[fordiebianco]

Excellent review, many thanks. Just like many others, I always had a soft spot for classic Infinity floorstanders. Great to see that the quality extends to their value ranges as well. Can now somebody please help Amir carry the Reference Standard IRS / V into his study?

 

[Heinrich]

At 9kHz there is something going on, maybe the bass/middriver; see off axis response and esp/ the peak in 3rd harmonic distortion. A steeper filter 3rd order would have been beneficial. Cost cuttings? The bass is pretty week, the port tuning is way too high to be practical. Considering the most likely positioning on a shelf an extended, softly falling response would have been an option.

 

[DanielT]

Would also be interesting to see how the Primus 250 performs.

You can find it in #11 and #15 in the thread linked below:

Infinity Primus 250 discussion

Does anyone know about these Infinity Primus 250 floorstanders? There's a set available close to me for $100. Of course I can't find reputable reviews and especially not measurements. I'm sure it would be a healthy upgrade from the Panasonic Thrusters that I had that has a woofer not working...

audiosciencereview.com

 

[uwotm8]

i had the alpha bookshelf speakers for a while.. they were decent, but they had some audible "hollow" sound that i would now describe as lower mid suck out.. if anything they tended to be , to my ears a bit bright.. the beta's were reported to be extremely similar in f.r. ....

Something like that was a typical complain about whole Infinity speakers of that kind

Current market price for used pairs in Germany is 50-80€ and availability is good. Pretty attractive as an upgrade for an all in one Yamaha Pianocraft type compact system. Or paired with a cheap Class-D

I wonder what %% of it has original, working and not damaged tweeters.
Also, cheap D-class combined with somewhat "cold", "bright" and "harsh" speakers may end up as an unpleasant b-b-bingo.