Showing posts with label Altec. Show all posts
Showing posts with label Altec. Show all posts

Friday, March 8, 2024

OJAS 529B Horn



During my visit to the OJAS listening room late last year, Devon asked me to evaluate a pair of horns OJAS developed in collaboration with Lycan R&R. The OJAS 529B is a 500 Hz horn rescaled from the large format Altec 329A for use with 1" format Altec/GPA compression drivers.


  This horn was designed with a throat inspired by the Western Electric 32 horn to avoid the harshness and distortion I (as well as others πŸ˜‰) associate with the Altec 811 and 511 horns
For more details about this horn's evolution and construction, please click here.

Monday, January 8, 2024

JE Labs Man Cave 2024


This is the side of the man cave where I spend a lot of time listening and evaluating new projects.

In the coming months, I will be talking about phono preamps, autoformer volume control, revisit the transformer coupled line stage topology, SE amps, etc. I will also continue my classic Japanese idler-driven turntable series, feature a couple of SE-DHT amp-friendly drivers + more.

Most of the audio components listed below are hyperlinked if you mouse over the text. Those that are not will be linked once the article is uploaded.

I like to taste new sonic flavors that are within the DIY realm😊

JEL man cave tour


Sunday, December 17, 2023

3D printed WP12024 horn from Lycan R&R

In late September, I received a message from Trieu of Lycan R&R, asking if I'd be interested in evaluating his 3D-printed prototype pair of multi-cell horns.

Before proceeding further, this blog entry contains a lot of hyperlinked texts to either previous entries or other sites pertinent to the article (e.g. "Lycan R&R" above). Mousing over and clicking those texts will open the link on another page. Thanks!

Design notes from Trieu: "These horns are slightly wider. The original KS12024 has a rather narrow 50° horizontal dispersion. When updated to the 1" driver opening, the wider initial diameter of the of the 1" driver would not allow for the throat geometries to work correctly. I felt the slim vertical profile of the original KS12024 is important sonically.

The best way to maintain it is to increase the horizontal width via a wider angle. So I increased the horizontal dispersion to 62.5° allowing for the proper expansion and geometries of the throat piece. BTW, I used carbon fiber infused PLA filaments."

Saturday, April 1, 2023

Altec 405A

This ain't no April fool's joke!πŸ˜†

Since the mid-60s (scroll down to pdf page 31), stateside audio experimenters have been trying to squeeze the last ounce of performance from the Coral/Sony "Holey" and Foster/Fostex FE103/Realistic 40-1197 family of 4" drivers. Meanwhile, Japanese aficionados like Old Joe (above), whom I follow on YouTube, kept snapping up Anaheim-manufactured Altec 405As in multiple quantities to stuff into their mini A7 VOTT projects. 

Because of the dearth of units left in the States and my indifference towards engaging in a bidding war versus fellow Asian hobbyists, I patiently hunted them for 20+ years via other channels.

Altec 405A specs

The 405A is a 4"  60-15,000 Hz wide range driver with a sensitivity rating of 92dB/4ft/1W. It's equipped with a massive Indox magnet that's almost the same diameter as its cone.

IMHO and experience, Altec cabinet plans always deliver sonically. Aside from a full understanding of the physics of sound, their engineers used their ears as the final arbiter in a design brief. To me, that trumps any design completely derived from a mathematical formula or computer simulation. So I asked my buddy @ Hommage Audio to fashion a Bonsai pair of Altec 614-style boxes based on the above dimensions.

Interior stuffed with Dacron

For sentimental reasons, I have a pair Realistic Minimus 8s on my test bench. I always thought they were above average, although not extraordinarily special. Same deal with the "Holey Frame" drivers I pulled out of a Sony TC500A RTR machine. To my ears, both FE103 derivatives have an upper midrange resonance, which require an EQ/contour network to make them more listenable.

614 style 405A cabinet

I found the 5.25" Realistic 40-1354A more impressive in spite of its narrow band whizzer honk. Back in the 90s, I played with it in a ported box similar in size to the above Altec 405A cabinet, as well as in a TQWT. Both speaker projects came from the book Designing, Building, and Testing Your Own Speaker System by David B. Weems.

Silbatone box + 755C and 405A in a 0.4 cubic foot ducted port box

Spoiled by years of exposure to Altec 755As and 755Cs in open baffles or 2 cf boxes, and more recently, in Silbatone cabinets, I considered this Altec 405A + Bonsai 614 style enclosure project as a mere novelty experiment.

 

As soon as I hooked them up to my near-field hifi system, I was pleasantly surprised that they play like their bigger brothers, albeit at a reduced scale. 

It's physically impossible for the 4" cone of the 405A to extend much below 90 Hz, but the roll off is gentle and there's enough harmonics to suggest bass lines. I hear a slight trace of peakiness in the presence region. For my taste though, an EQ filter isn't necessary. 

Although the Altec 405A can't replace the Altec 755C (much less the 755A) in my near-field set up, its midrange depth, micro dynamics, detail resolution and overall tonal balance makes it worthy of the Altec badge!πŸ‘πŸ˜Š







Wednesday, November 16, 2022

Snell Type JIII Finale - Sensitive Enough?

With the foam issue out of the way, it's time to wrap this up!

If I never allowed myself to be conned by the Junkyard Jukebox guy to subscribe to his Sound Practices audio rag in the early 90s, I may have soldiered on tweaking my classic push-pull EL84 and EL34 amps and upgrading my LS3/5As (or adding) to this pair of Snell Type JIIIs (or maybe even Type Es) in my listening room.

But things didn't turn out that way...

Altec 755C + Open Baffle + Simple 45 amp

I succumbed to the temptation of single ended triodes + Altecs!

 
In my reality check article, I used the above chart to associate frequencies with the vocal range of humans and acoustic musical instruments. Please use it as a guide to the RTA traces and discussion of frequency ranges below.

Lou Donaldson on Snell Type JIIIs

The Snell Types E, J, and K have developed a reputation as single ended triode (SET) amp-friendly speakers. Arguably, my pair of Type JIIIs can be a good stop gap but I'll try to explain in the simplest terms as to why, in the final analysis, they don't meet my criteria for flea power amplifiers designed with "it's the first watt that counts" ideology.

Snell Type JIII specs

Since I couldn't find a late 80s to early 90s Vifa catalog, I based all the specs from the above information provided by Snell. The low(ish) nominal impedance (Z) of 6 ohms is an advantage when driven by current source devices such as solid-state amplifiers, which can typically supply more power to a lower Z load. OTOH, vacuum tubes are inherently high impedance/voltage source devices, thus requiring output transformers to drive lower Z loads. However, any well-designed tube amp with an 8 ohm tap from the secondary of the output transformer shouldn't have problems driving the Type JIII.

Snell Type JIII

While the man cave is hardly anechoic, this RTA trace is smoother compared to anything I've taken from any of my Altecs. It pretty much tracks the manufacturer's specs.

Altec 753C

In spite of the fact that the Altec 753C's RTA isn't quite as smooth, it has a half octave greater extension in the low end. The top end also starts to roll off earlier, at around 13kHz. But as further discussed below, the performance of the Altec 802D compression driver + Altec 32C belies its 40s Western Electric roots.

Altec 414A vs. Vifa M21

The radiating area of the Altec 414A cone at 95 square inches is 2.5 times greater than the 8" Vifa M21's 38.5 square inches. Both use paper cones - the Altec cone is left bare and suspended by a treated accordion surround, while the Vifa uses high compliance foam and its cone is treated with some form of damping compound. The added cone mass from damping helps low frequency extension. Regrettably, it also reduces speaker sensitivity, among other things.

Altec 414A in wide range mode

In wide range mode, the 414A's 95 square inches of radiating area covers a frequency range of six and a half octaves, starting from around 40Hz-3500Hz. That's just a few notes shy of a piano's range at both extremes as well as the fundamental notes of most acoustic musical instruments and easily, the entire human vocal range. This driver sounds very natural to my ears and plays smoothly with no detectable glare or shout manifested when listening to music. I’m happy to report the tiny spike before 1kHz isn't audible to me. πŸ˜‰

The Vifa M21's smaller radiating area of 38.5 square inches tasked to reproduce five and a half octaves from 49Hz all the way to its 2700Hz roll off point is a greater challenge.

Altec 414A specs

The 414A goes lower than the Snell JIII but not quite solid down to the claimed 30Hz rated fundamental. With a 99dB/1W/4ft sensitivity, it has an 8dB advantage over the Snell Type JIII's 1.6 cubic foot (cf) ported box rating of 91dB/1W/1M. Housed in a 4 cf bass reflex cabinet, the 414A can definitely move a whole lot more air with minimal power input. 

Reverse engineered Snell JIII crossover

The type JIII's crossover is a bit more complicated than my Altec 753C XO below. Encircled in red is a paralleled choke/resistor/capacitor EQ network for the Vifa woofer. This shapes and/or controls cone resonance in the midrange. Unfortunately, the EQ network also absorbs power.

Case in point, BBC engineers' extensive use of EQ in the LS3/5A crossover made it notoriously inefficient. But to their credit, whether it was the earlier 15 ohm or later 11 ohm version, it was a friendly load, especially to tube amplifiers.  

Altec 753C crossover

Since the 414A has no serious peaks or dips, which I verified through years of listening and later confirmed via RTA, I chose to run it in wide range mode in which the woofer rolls off mechanically. This preserves the efficiency/sensitivity of the woofer and makes the crossover simpler since it only involves a 4 uf capacitor acting as a high pass filter. By using non-inductive resistors, the Altec 802D compression driver is attenuated to match the 414A's sensitivity. Then I adapted the high frequency EQ circuit from the Altec 30923 to tweak the shape of its top end response. 

Left: Altec 802D + 20275
Right: Snell/Vifa D26

For the higher frequencies, Snell chose the Vifa D26 1.25" soft dome fabric diaphragm that has a radiating area of 1.23 square inches vs. the Altec's 2.25" diameter aluminum diaphragm with an equivalent 4 square inches of radiating area. 

Snell employed a sharper 12dB/octave slope high pass filter for the dome tweeter to cut in @ 2700Hz while I blended the 802D compression driver/32C horn combo at a gentler 6dB/octave slope @ 3500Hz in the Altec 753C just where the 414A top end response starts to taper off. 

Altec 802 + 32C horn

My old school high frequency horn loaded system uses the Altec 802D compression driver in conjunction with the 90° H x 60° V dispersion Altec 32C horn originally designed by Western Electric for their 753C monitor system. It's merely coasting along from 3500 Hz, generating the top most octaves and harmonic overtones compared to the hard-at-work direct radiating Vifa dome tweeter diaphragm of 1.23 square inches struggling to replicate the final octave of top end fundamentals from 2700Hz. Hence, the Altec horn system reproduces much faster and cleaner transients with ease, while also enhancing the already effortless presentation of micro and macro dynamics of the high efficiency 414A woofer.

I'm not set up to plot a reactance chart for the Altec 753C and Snell Type JIII but after using them with various amps in my collection, I guesstimate that both proffer a benign resistive load. However, the 16 ohm nominal impedance, simpler crossover of the Altec 753C and its greater efficiency are a godsend to low damping factor single ended directly heated triode amps.

Lou Donaldson on Altec 753Cs

How far has speaker design progressed?


Vifa M21WN-07-04 + Altec 755C

Ever since I built my first pair of open baffles, evaluating drivers in wide range mode in order to gauge their ability to reproduce an accurate midrange has become routine. Listening to the Vifa M21 woofer in this manner wasn't a very pleasant experience because it sounded very dull. This is in stark contrast to the snappier midrange of the Altec 414A, which I've been using in wide range mode for many years. Likewise, the Vifa 8" was totally outclassed by a handful other woofers and wide range drivers in my collection including the 10" Altec 406Z and Altec 756B.

It's a no brainer that the long travel foam suspension + cone damping extended the low frequency response of the 8" Vifa. But to my ears, this was achieved to the detriment of midrange performance. Is bass extension really more important than midrange accuracy in the high-end audio era? Why is cone damping so prevalent in modern drivers? Western Electric, Jensen, Altec, and their contemporaries all used bare cones.

During the era of Western Electric and Altec, engineers used their ears, guided by cutting edge technology test equipment. This can be gleaned from contemporary ads and press releases. I can't help but wonder if the Vifa woofer was designed merely to satisfy test instrument requirements and laboratory standards without any ear testing involved. If that is the case, is that what we consider progress?

I chose the Altec 755C over the near mythical Altec 755A for this feature because IMHO, it is a worthy benchmark for an 8" wide range driver that is still quite accessible and affordable in the real world. Based on the above specs, by the time Altec introduced the 755C in the late 50s (or early 60s?), they had conceded to the spec wars triggered by the commercialization of stereophonic equipment. I've listened to the 755C loaded in an OB, 2cf box or the Silbatone cabinet but never heard a solid 40Hz low end, merely well defined harmonics of that fundamental. 

Simple 46 amp  (1250mWpc) > Altec 755C in Silbatone enclosures

Granted the 755C can go a bit lower, subjectively, its low frequency extension isn't significantly greater than the 755A. I'm glad though that Altec was able to retain much of that captivating midrange + dynamics even if it's not quite as realistic as its older Western Electric-designed 755A sibling.

Altec 755C in the Silbatone box

The Silbatone + 755C combo loses about an octave at the frequency extremes vis a vis the Snell JIII but has a 5dB advantage in sensitivity. Despite the spikes and dips in its RTA trace, I much prefer listening to the Silbatone 755Cs. Maybe the dips and spikes = musical?πŸ€” 

Snell JIII = 1.6 cf vs. Silbatone 755C = 1 cf

Whether driven by my SET amps, Dynakit ST35 or Nobsound/JLH 1969 clone, the Snell Type JIII sounded veiled and anemic compared to the Altec 753C and Silbatone 755C. With the Snells, I have to turn up the volume a couple of notches to be engaged musically but with the Altec 753C or Silbatone 755C driven by my weakest 750mW per channel SE71A amp, I already hear subtle details even at background sound pressure levels (SPLs). Understandably, the JIII could not compete with the Altec 753C at the loudest end of the spectrum since it doesn't have the physical size to move as much air. But considering Snell's reputation, I expected better resolution and nuances at low to medium SPLs.

Music Reference RM9 amp > Snell JIIIs

The most convincing full range sound I got from the Snells was when they were driven by the Music Reference RM9 amp, a push-pull parallel/triode connected EL34 stereo amplifier producing 35 watts per channel with the negative feedback set at minimum. Alas, with this combination, the irresistible charm of the single ended directly heated triode amp is lost...I can't have my cake and eat it, too.πŸ˜” 

Altec 755C in Silbatone cabinet + 3000H super tweeter
Truth be told, lately, I find the use of a super tweeter redundant

Through the years, I’ve tested a few vintage and contemporary 8” wide range speakers but haven't found any which could closely approximate the 755C’s sound quality. The design isn’t rocket science and if Great Plains Audio still has the original tooling, I don’t see any reason why the humble 755C PA speaker can’t be reproduced at a reasonable price. That would be a great boon to single ended directly heated triode amp aficionados, especially those who have limited space in their listening room.😊 

Altec 753C + Snell Type JIII

Contrary to current trends in speaker cabinet design, the wider front baffle area of the Altec 753C cabinet (and to a lesser extent, even the Snell Type JIII), enhances projection by acting as an acoustic soundboard. Western Electric and Altec speaker systems were usually fitted with wings in theater installations, which is the main reason I've been an advocate of the wide open baffle. In principle, this is practically no different to the fully open lid of a grand piano during a performance in a concert hall.

Altec 753C + mini tour of the man cave 

The Snell Type JIIIs can give a glimpse of what directly heated single ended triode amplifiers can do. But these are definitely not end game speaker systems for those who want to indulge in the delights of flea powered single ended directly heated triode amps. As competent as the Snells are and given their already above average sensitivity (compared to typical high end audio speakers), they could never spook me into believing musicians come alive in my man cave the way my Altecs can at times. For some organic reason, I can also listen to my Altecs for extended periods without listening fatigue creeping in. Keep in mind though that the empirical and subjective observations embodied in this article only reflect my musical aesthetics and priorities. YMMV. 

I hope I was able to illustrate that there's no myth or magic to a fine sounding and efficient speaker system. All it takes is a basic understanding of the physics of sound and learning how to compromise.



Go back to Part 1 and Part 2







Monday, August 1, 2022

OJAS @ Lisson Gallery NYC

Our dear friends Charito and Joey, whom we haven't seen for over five years, were in NYC visiting for a couple of days. On short notice, Tish was able to take a day off so we were able to meet up with them. Joey is an avid audio DIYer and was a frequent collaborator especially during the annual November Hifi Show when I was still based in Manila. He represents G.I.P. Laboratory in the Philippines. 


It was also timely that Devon (OJAS) Turnbull's HiFi Dream Listening Room No. 1 exhibit at the Lisson Gallery NYC was on its penultimate week. So Joey and I agreed that this was going to be our meeting place! 


The OJAS loudspeaker system utilizes Great Plains Audio drivers, which are currently produced using original Altec tooling - GPA 416B 16" woofers + GPA 288H 1.4" compression drivers. The latter compression drivers are coupled to bespoke OJAS 1505 horns, which are remastered versions of the classic Altec 1505B multi-cells, while Pioneer PTR9 ribbon super tweeters fill-in the top-end octave harmonic overtones. At the center is a Fostex FW800HS super woofer. Devon starts with Werner Jagusch crossovers but driver loading and alignment are all developed in-house and then fine tuned by ear!

Having spent almost a decade studying at The Juilliard School twenty years before the Diller Scofido + Renfro reboot, I developed an immediate affinity for the brutalist vibe of the speakers!


The OJAS gestalt brought back cherished memories of the late Don Garber's Fi audio gallery from the early 90s, which was along 30 Watts Street in SoHo NYC. I wasn't able to ask Devon if he got the chance to meet Don. I bet they would have gotten along really well!


A pair of Altec/Peerless 4722 SUTs are mounted directly on a FET-based phono preamp using vacuum tubes as constant current sources. This was designed by jazz guitarist Steve Berger, who's also the man behind Aprilsound NYC. The adjacent chassis with two large knobs houses a transformer volume control wound by Dave Slagle of Intact Audio.


Being a devoted Garrard 301 listener for many years, Devon is cognizant of the finite supply of these idler driven classics. So for this project, he chose the platter + motor from a Technics SL1200G and mounted them in a custom layered plywood plinth. To assure absolute speed stability and smoothness in operation, a 3-speed linear power supply was specially designed by Linear Tube Audio. Having done DJ work during his younger years, he admits that his choice was partially in reverence to the marque.

Mounted at the back is an Ortofon RMA309 tonearm + a restored vintage SPU-A for stereo LPs and a Dynavector DV505 tonearm + SPU mono CG 65 Di for 78 rpm shellac discs.


Devon's pair of SE300B mono-blocks (fitted with Tango XE20S output transformers) is an homage - not a slavish copy but his own interpretation - to Herb Reichert's Flesh and Blood amplifier published in Sound Practices Issue 8. 


Unlike a typical hi-fi show swarming with silver-haired or balding guys, it was refreshing to be surrounded by a twenty-to-forty something crowd. Devon is attracting and developing a niche market uncharted by mainstream high-end audio publications such as Stereophile and The Absolute Sound. Due to his background in design and interaction with the upper echelons of the fashion and music industries, the whole Sound Practices ethos of music reproduction spearheaded in the early 1990s by Joe Roberts will hopefully reach a larger audience. 


Joey and I spent a couple of hours listening to Blue Note jazz, contemporary classical music, and talking shop with Devon. He was a very gracious host, who candidly gave credit to his collaborators as well as to those people who've influenced and inspired him.

Me, Devon, and Joey

Bravo, Devon, very well done! 
After several years of PMs, it was great to finally meet you. I look forward to more shop talk when you visit my man cave.


Devon's HiFi Dream Listening Room No. 1 exhibit at the Lisson Gallery in Chelsea NYC is really worth hearing and seeing! 

Open Monday - Friday from 11am - 6pm until August 5, 2022.


This 'zine contains comprehensive information about the whole hifi installation + more! 
The poster + 'zine is available at Printed Matter Inc.








 

Friday, April 8, 2022

Altec 756B + 32C + 806 + 23744 = mini 757

The WE756A is the middle child in the Western Electric series of wide range drivers introduced in the late 40s.

I've seen and heard a couple of WE/Altec 728Bs + a dozen or so pairs of 755As, but I've never heard a WE756A and have only seen one in the metal at a radio show many years ago. Although still quite scarce, its Altec 756B brother isn't quite as elusive.

Back: Blonde + Mahogany Altec Melodist 700A
Front L-R : WE728B, Altec 755A/pr. + Altec 756B

The few Altec 756Bs I've encountered all came out of the Altec Melodist 700A. It's a compact bass reflex speaker system loaded with the 756B, supplemented on top by a 3000A horn tweeter via an N3000B crossover. The 700A belonged to the Melodist monaural hifi system line, which Altec targeted at apartment dwellers in big cities of midcentury America.

 Subsequently, the 756B was replaced by an 8" Altec 401A and was re-designated as the Melodist 700B. With the introduction of stereo for the mainstream market in 1958, the Altec Melodist line quietly faded into oblivion.

 If found in good condition, the Altec Melodist 700A is a fine looking midcentury modern artifact! Unfortunately, the < 1.5 cf ported box doesn't allow the 756B to shine sonically, IMHO. Since it shares similar proportions to its more successful contemporaries like the Acoustic Research AR-1 and the Jensen Duette, the cabinet design may have been dictated by market positioning rather than sound engineering.

My once-in-a-lifetime lucky find 700A above has lived a hard life. The lower front edge of the cabinet was missing while the sweet and airy but very fragile 3000A horn tweeter element had been replaced by a tiny ferrite magnet dome tweeter.😏 A "mod" that has been circulating in the internet, so watch out.  

 

Fortunately, the 756B is very well preserved. If memory serves me right, the WE756A frame is more substantial than the Altec 756B. That’s probably the reason why the back handles were omitted in the Altec. The 756B has an 8 ohm voice coil, while the WE756A is 4 ohms.

J-Rob's Altec 756B at 
Capital Audio Fest 2016

Joe Roberts has already done a great job of describing the sonic qualities and proper implementation of the Altec 756B in his (Geekstar) "My big ten inch --Altec 756B" post at the Altec User's Board. He also gave insight on the shifting Asian market for vintage Western Electric and Altec gear. A guaranteed fun and informative read!

Since I don't have Joe's networking skills, I resigned myself to the reality that my Altec 756B will be the main speaker of my monophonic hi-fi set up, just as Altec intended.

Click for a videoclip

Meanwhile, I repurposed (sealed) a Heathkit AS10 (almost 2 cf) cabinet to familiarize myself with the 756B. I listened to it as a wide range driver with and without top end assistance from either a 32A/802/34852 + an XO based on this schematic or 3000H with an L-Pad + 0.5 uf - 1 uf paper in oil cap. The simplest XO I used was a 0.22uf paper in oil cap in series with the + terminal of the 3000H, no L-pad needed. That also sounded good, albeit, with slightly less sparkle.   

JE Labs mini 757
inspired by the Western Electric 757A

After extensive listening in wide range mode, I determined that a mono hifi set up will benefit from a wider baffle + the dispersion pattern of the Western Electric-derived 32 horn. So I sketched a slant front ~ 2.5 cf infinite baffle that has a provision for an Altec 32C horn + 802 driver and sent it to John Piro of Hommage Audio.

728B vs. 756B

As expected, the 756B is more extended at the top end than the 728B with almost, but not quite, equal bass extension. However, music through the 728B held my attention appreciably longer without my reaching for a clip-lead to fill in the top octaves with the 32/802 horn/driver for more harmonic overtones above 5 kHz. 

RTA = Altec 756B in a ~ 2.5 cf infinite baffle 

I confirmed this during one of my shop talks with J-Rob, who also found it more rewarding to listen to 728Bs in wide range mode than to his 756Bs. It makes me wonder if the 756B and its WE756A brother were designed with a middle-child syndrome gene in their sonic DNA.πŸ€”

After many years of collecting Altec 1" compression drivers, I've only landed a single Altec 23744 "light" aluminum diaphragm, which was fitted to an 806 motor that was used in the Altec 9849 monitor speaker.

Things started to crystalize when my friend Dave V. aka Salectric,πŸ™ sent me his spare .085 mH choke. It was a proprietary part found in the EQ circuit of the Altec 9849 crossover, which is an 8 ohm speaker system. This EQ circuit shapes and boosts the response of the 32/806 horn/driver combo. Incidentally, Dave's "Last PAS" articles written for The Audio Amateur contributed to my 80s Dynaco hacking activities.

RTA = Altec 32C + 806 + 23744

 The 4 uf paper in oil capacitor serves as a first order high pass filter hinged around 5 kHz with a gentle 6dB/octave slope, while the variable 8 ohm L-pad shapes and controls upper frequency overtones to taste. 

inside the mini 757

John P did a great job of building a very rigid cabinet, which saved me the time and trouble of having to experiment with damping. I just lined the interior panels with Kimpak and I was ready to listen.

RTA = JE Labs mini 757

This project transpired as an opportune moment to assemble all the singleton Altecs from my collection - 756B + 32C + 806 + 23744 - into a formidable monaural hifi speaker system.😊

JE Labs mini 757

My ears hear close to half an octave of bass extension from the mini 757 compared to the 755A in a Silbatone or 618 cabinet. Due to its greater efficiency, it plays louder while dynamics at micro and macro levels are less compressed. The larger cone area of the 756B + wide baffle + 90° horizontal x 60° vertical dispersion of the 32C horn, portray a bigger sense of scale. All of these were achieved without compromising the midrange realism I enjoy from my beloved 755A. 

However, the Altec 753C is perceptibly more efficient, offers at least an octave lower of extension with more authority. It also produces higher SPLs. 

Alas, we can't defy the physics of sound...

JE Labs monophonic hifi

...so I focused on the aesthetics by spicing it up with a touch of Charles Eames and Dieter Rams! πŸ˜‰