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Sansui SP-3005 project confusion

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Posted on October 4, 2016 at 23:01:53
maxhifi
Audiophile

Posts: 584
Location: Alberta, Canada
Joined: August 4, 2004
 Picked up a pair of these rather unique speakers a few years back in very poor shape, cabinets had got wet at some point (by previous owner) and bottoms totally rotted out. Left them in the garage as a future project Recently I Decided to have some fun, removed and tested all components and all drivers are good. Claimed sensitivity is 96 dB 1W/ 1m so that's why posting here.

Decided to then do some reverse engineering to figure out what the original design was all about.This is where I got a bit confused,

Woofers seem pretty good quality., 12" paper cone drivers with fairly heavy ceramic magnets

I measured the following parameters

Fs = 36.4 hz
Qms = 2.93
Qes = 0.987
Qts = 0.738
Vas = 2.22 ft^3

Volume of enclosure is 2.3 cubic feet, and port is really weird, 5.5 inches diameter and 2.75 inches long.

If I treat the enclosure as a helmholtz resonator, and use the basic formula for calculating resonant frequency, the box resonates at about 70Hz.

What confuses me is when I enter everything into boxplot 3.0, it gives a pretty nice response when I set h = 0.5. ( h being Fs/Fb), but the vent calculator tells me the port should be 14 inches long.

If I adjust h so that boxplot gives me a 2.75 inch port, the response it graphs has a massive peak which makes no sense at all, with h = 0.5 the response actually looks good.

My intention in reverse engineering is to evaluate if the original design has any potential to sound good before I bother with making new enclosures. I must be missing something, I don't really understand the discrepancy between the boxplot vent length result and the helmholtz resonant frequency calculation.

Update: I initially misinterpreted what h means in Boxplot. Assuming I measured the driver parameters correctly, the design indeed does have a big ugly peak, and is therefore not really suitable for hi-fi sound reproduction as-is.

 

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RE: Sansui SP-3005 project confusion , posted on October 5, 2016 at 07:52:49
Bill Fitzmaurice
Industry Professional

Posts: 5371
Location: New England
Joined: October 20, 2002
 That driver should never have been used in a vented enclosure, at least not one of that size. It can work reasonably well vented, but only in at least 8 cubic feet.
In 2.3 cu ft with the port size you listed it would have an Fb around 65Hz, with an 8 to 10dB hump at 70Hz. I can't imagine listening to that. Making the port 14 inches long would lower Fb to around 40Hz, lowering the hump to perhaps 5dB at 45Hz, which is better. But I'd put that driver into a sealed cab of 3 cu ft or so, heavily stuffed to get the Qtc down to around 0.8. That should give reasonably flat response with an F3 at 45Hz.

 

RE: "an 8 to 10dB hump at 70Hz. I can't imagine listening to that"..., posted on October 5, 2016 at 08:03:13
Ivan303
Audiophile

Posts: 48887
Location: Cadiere d'azur FRANCE - Santa Fe, NM
Joined: February 26, 2001
 You must have slept through the late 60's, early 70's, because there were a LOT of speakers with a big 'bump' in that area.

The audio store sales people called it 'Great Bass'.




First they came for the dumb-asses
And I did not speak out
Because I was not a dumb-ass

 

RE: Sansui SP-3005 project confusion , posted on October 5, 2016 at 09:07:44
maxhifi
Audiophile

Posts: 584
Location: Alberta, Canada
Joined: August 4, 2004
 I tried to input the same parameters into different software. The Sansui port appears to be tuned to 64Hz according to online calculators. I got around 70 using the helmholtz resonance formula, but that isn't really accurate. The big peak in the bass is present on every simulation I try.

When I measured the parameters of the driver, I used the me the methods in David Weems books, and the Elliot sound website. I used a signal generator, power amplifier, 10 ohm resistor, and radio shack DMM as a volt meter and frequency counter. I used the added mass method for calculating the Vas, I blu tacked a couple capacitors to the cone and then weighed them using my ortofon tracking force digital scale. I think I followed the method properly, but it's always possible I made a mistake since it's the first time I have measured a driver in over 20 years, and I am only a hobbiest.

That said if I did it all properly, the original enclosures do look like they have a big peak in the bass region. I don't want to build speakers with this characteristic, it won't sound any good. I never heard them before taking them apart so can't comment on original sound quality.

These speakers are from 1972, so definitely in the late 60s early 70s range.

For the rebuild, the consensus is to abandon the port and slightly increase enclosure size? I sure like how the response looks better when I simulate that version.

 

RE: Sansui SP-3005 project confusion , posted on October 5, 2016 at 18:57:01
Don Reid
Audiophile

Posts: 890
Location: Rural NW Georgia
Joined: February 2, 2001
Contributor
  Since: April 1, 2010
 MaxHifi, if you are approaching your Sansui speaker project as a research study to learn more about speaker drivers and enclosures I applaud you and urge you on. I have invested untold hours playing with speakers I literally picked up at a trash dump. If you hoping to end up with a great sounding speaker I suggest you invest your time and energies working with better drivers.

I heard many Sansui speaker systems back in the late 1960s and 70s. Many guys returning from tours in Viet Nam brought stereos home with them often featuring big fancy Sansui speakers, Also they were common in USA stereo stores. I don't wish to be thought a negative and overly critical person, but off hand I can't think of anything good to say about those old Sansui speakers except that the great big ones could make a great big sound.
I dream of an America where a chicken can cross the road without having it's motives questioned.

 

RE: Sansui SP-3005 project confusion , posted on October 5, 2016 at 22:18:10
maxhifi
Audiophile

Posts: 584
Location: Alberta, Canada
Joined: August 4, 2004
 Thank you for the encouragement. This project exists only for fun/learning. I don't think they will be competition for my good speakers.

I find it fascinating how these speakers appear to be very good quality (1" thick braced enclosures, heavy nice looking drivers, well veneered cabinets, etc) but the design is at the same time very poor. At first I didn't believe the cabinet alignment could be deliberately designed so poorly but it appears to be so. It's no wonder you didn't like the sound. All the same, what an interesting time and place in history these are from.

Once I get the cabinets sorted out I sure hope the crossovers and mids/tweeters don't need an equal amount of rework. One thing that raised a bit of an alarm is that two different types of mids are in parallel! Will cross that bridge later though, the fake JBL style acoustic lens has me convinced these are good, for now.



 

RE: Sansui SP-3005 project confusion , posted on October 6, 2016 at 09:57:57
Paul Joppa
Industry Professional

Posts: 7296
Location: Seattle, WA
Joined: April 23, 2001
 I can't help wondering whether the magnet has lost some strength, so the original design Qt could have been lower.

 

RE: Sansui SP-3005 project confusion , posted on October 6, 2016 at 10:08:55
Bill Fitzmaurice
Industry Professional

Posts: 5371
Location: New England
Joined: October 20, 2002
 >I can't help wondering whether the magnet has lost some strength, so the original design Qt could have been lower.

Maybe, or maybe it just had a large coil gap, not unusual with inexpensive drivers. Also consider that depending on how old it might have pre-dated T/S specs, and if not it still pre-dated modeling software, or even the PC for that matter. I remember Sansui being very popular when I was in college, and I graduated in '71, when all speakers were product of empirical design.

 

RE: Sansui SP-3005 project confusion , posted on October 6, 2016 at 10:45:22
maxhifi
Audiophile

Posts: 584
Location: Alberta, Canada
Joined: August 4, 2004
 I'm going to measure the other woofer tonight, and see how close they are to each other. You guys may have a point, there's definitely no sense in building enclosures if the speakers are shot.

 

RE: Sansui SP-3005 project confusion , posted on October 7, 2016 at 05:48:43
weltersys
Industry Professional

Posts: 685
Location: FL
Joined: September 28, 2004
 Maxhifi,

I bought a quite similar pair of Sansuis a decade ago, with both dual (different) mid "squawkers" and two tweeters, the only way for the woofer to "keep up" with that racket was the high Fb.

As was mentioned, a lot of the Sansui cabinets came home with Vietnam vets, after listening to helicopters, machine guns and land mines, they liked their rock & roll LOUD, and the Sansui's delivered.

Considering most Pop, Rock & R&B vinyl records of the time had little content below 50 Hz (other than warped records ;^) ) 65-70 Hz is missing only about 1/3 octave of content. The Altec Lansing A7 "Voice of the Theater" was tuned in that range too, as were most PA cabinets of the era. The Sansui at least used ducted ports, it was more common to just cut holes in the cabinet, 3/4" deep "ducts" were typical.

Things have changed gradually through the decades, used to be a solid 40 Hz was the "real deal", then around 1990 bass players started adding a 31 Hz Low B string to keep up with all the synth basses, now even bluegrass recordings have plenty of 25 Hz content.

Art

 

RE: Sansui SP-3005 project confusion , posted on October 7, 2016 at 08:58:48
maxhifi
Audiophile

Posts: 584
Location: Alberta, Canada
Joined: August 4, 2004
 Hi Art,

Did you end up using your Sansui speakers? My living room system has klipsch la scalas, so this kind of bass roll-off isn't unfamiliar, and to be honest I listen to mostly older recordings on LP, so not a big problem. The la scalas however are well designed, and don't have any gross peaks or valleys in the response to color the sound.

still have yet to measure the second woofer, am curious to see if maybe they have deteriorate over time

Best regards

Max

 

Second Woofer Measurement, posted on October 7, 2016 at 13:46:24
maxhifi
Audiophile

Posts: 584
Location: Alberta, Canada
Joined: August 4, 2004
 First Speaker:

Fs = 36.38
Qms = 2.93
Qes = 0.987
Qts = 0.738

Second Speaker:

Fs = 34.79
Qms = 2.86
Qes = 1.06
Qts = 0.77

Looks like they're not all that different from each other.

 

RE: Sansui SP-3005 project confusion , posted on October 7, 2016 at 14:47:24
Don Reid
Audiophile

Posts: 890
Location: Rural NW Georgia
Joined: February 2, 2001
Contributor
  Since: April 1, 2010
 Now that you mention it, while I have heard Sansui speakers I have never had a chance to take one apart to see what's what. It is always possible that good drivers were crippled by badly designed enclosures and/or crossovers. Stranger things have happened. I might have been a negative and overly critical person when I bad mouthed the drivers so quickly.
I dream of an America where a chicken can cross the road without having it's motives questioned.

 

RE: Sansui SP-3005 project confusion , posted on October 7, 2016 at 15:52:15
hennfarm
Audiophile

Posts: 535
Location: Oregon
Joined: October 8, 2008
 Possibly your dmm does not measure voltages at varying frequency in a linear fashion, I had (have) the same issue recently using the 10ohm series resistor method. Fs le and re can be made but as for the remainder of t/s parameters its a crap shoot without a good bench meter...JH

 

RE: Sansui SP-3005 project confusion , posted on October 7, 2016 at 17:06:09
maxhifi
Audiophile

Posts: 584
Location: Alberta, Canada
Joined: August 4, 2004
 This is a good point, I think my DMM is pretty close, (claims to be true RMS over a broader range than I am testing) but will redo tests with a VTVM to confirm.

What I think is screwing up the results a bit more is my amplifier, it has a fairly high source resistance.

 

RE: Sansui SP-3005 project confusion , posted on October 7, 2016 at 19:43:18
Bill Fitzmaurice
Industry Professional

Posts: 5371
Location: New England
Joined: October 20, 2002
 >These speakers are from 1972, so definitely in the late 60s early 70s range.

They would not have used T/S specs in the design stage. T/S was pretty much unknown outside of Australia/New Zealand until 1971, and it took a few more years before cabs using them appeared. The use of such a large diameter port relative to the driver size is also a giveaway that it was a seat of the pants design. Too bad, sealed it probably would have sounded pretty good.

 

RE: Sansui SP-3005 project confusion , posted on October 8, 2016 at 14:18:03
weltersys
Industry Professional

Posts: 685
Location: FL
Joined: September 28, 2004
"Did you end up using your Sansui speakers?"

Yes, I used one pair of mids and tweeters for my kitchen speakers, using a separate sub woofer, the other pair of mids went into patio speakers, and the woofers were given away to another vendor at the Albuquerque Flea Market before I moved down into the path of Hurricane Matthew.

Power just came back on after a 27 hour outage, considering the amount of trees taking down power lines all over, I was quite surprised to get power back today.

Art

 

RE: Sansui SP-3005 project confusion , posted on October 9, 2016 at 16:09:52
maxhifi
Audiophile

Posts: 584
Location: Alberta, Canada
Joined: August 4, 2004



Wow, that's a lot to endure! Hope everything ends up okay!
It's cool you re-used some parts from the Sansui speakers. I've been drawing out a schematic for the crossover, it's a bit of a mess. There's switches to bypass it in order to use three separate amps and an active crossover (which makes little sense to me considering this isn't that good of a speaker)

The mid and treble level controls used tapped auto transformers, which double as inductors for the high pass filters. It is a full three way second order crossover though. Next I will measure all the chokes and driver impedance at crossover frequency and simulate it to see if anything weird is going on like with the bass alignment.

 

RE: Sansui SP-3005 project confusion , posted on October 11, 2016 at 14:38:47
Crazy Dave
Audiophile

Posts: 14371
Location: East Coast
Joined: October 4, 2001
 I owned Sansui SP-2000 speakers, and they had a similar bass alignment. I think it was deliberate. These speakers were designed for the Japanese market where people live in tightly packed apartments and low base would only get you complaints by the neighbors. On the plus side, they were efficient as hell and the drivers operated in the range where they were very pistonic. The SP-2000's are a bit older than the SP-3005's and had all alnico drivers, that I believe were made by Coral.

Dave

 

RE: Sansui SP-3005 project confusion , posted on October 12, 2016 at 14:32:53
maxhifi
Audiophile

Posts: 584
Location: Alberta, Canada
Joined: August 4, 2004
 Those ports look very similar to mine. I'm mid way done building new cabinets for the so-3005s, am excited to hear them!

 

More to this than I thought., posted on October 12, 2016 at 22:29:54
maxhifi
Audiophile

Posts: 584
Location: Alberta, Canada
Joined: August 4, 2004
 I measured all the crossover values, and the driver impedances at crossover frequencies.

Simulated using Passive Crossover Designer 7, It turns out the crossover is designed with a high Q to compensate for the peak the port creates, by creating its own peak at 300 - 400 Hz, rather than being designed for flat response. The two peaks together sum to a fairly flat response during the woofer pass band.

My info isn't good enough to do a full simulation, but I get the impression that the crossover is compensating for the peak the port creates, which would make the overall frequency response much flatter than simulating the box alone would let on.

In other words, I think I will stay with using a port for my rebuild - at least for now. And my apologies to the Sansui engineers who I thought badly of when I critisized the box design! I think they just sacrified a little flatness for sensitivity, rather than making a one note bass design.


 

RE: More to this than I thought., posted on October 13, 2016 at 07:02:11
Crazy Dave
Audiophile

Posts: 14371
Location: East Coast
Joined: October 4, 2001
 Usually, Sansui speakers have very flat impedances and are very easy to drive, but I am more familiar with the earlier speakers than the later.

Dave

 

RE: Simplify Sansui Speaker Crossovers And Enjoy, posted on October 15, 2016 at 08:53:55
FRG7SWL
Audiophile

Posts: 2109
Location: NorCali
Joined: March 26, 2003
 Greetings from Sactown, Maxhifi. Have had several 'sui speakers pass through audio arsenal, & found they all benefited from utilizing simple capacitor crossovers in lieu of stock x-over net to sound expressive-n-expansive. Got a pair of SP-2500s from Audio Karma's Robisme, which had no bass thump a'tall stock. Replaced stock 10 uf mid-squalker x-over cap with 12 uf Dayton polyprop, & wired mids in series since they were similar. Since there was tweet eq contour for either 4.7 uf or 2.2 uf, decided to put 4.7uf Dayton polyprop on bottom tweet, & 2.2 uf Dayton polyprop on top tweet. Sounds sweet with Superscope R-1240 amplification, & doesn't want for Winterlandish volume when needed. Oh yeah, replaced thin stock internal wiring with 16 gauge. ... Got a pair of SP-1500s from a guitar geek bud, which had sat in a closet for damn near two decades. Since mids were different sizes, put a 10 uf Dayton polyprop on larger mid, & 6.8 uf Dayton polyprop on smaller mid (6.8 uf was stock mid x-over, wired to both mids; giving each mid its' own x-over cap cleared up that slightly congested stock sound), 4.7 uf Dayton polyprop went on mid tweet, & 2.2 uf Dayton polyprop went on flank tweet. Semper Fi recipient loves them pups, powered by Sony STR-6055 amplification. Wife loves 'sui's Kabuki countenance. A pair of AS-100s needed a mere 4.7 uf Dayton polyprop tweet x-over replacement to sound sensational with Rotel RX-602 amplification. Neither the 1500s nor the AS-100s needed stock wiring upgraded. ... Had a pair of latter generation 'sui Classique 900s, & replaced stock woof with Titan kicker from late, lamented Marvac. Was used to generate studio reverb for KDVS'"Live In Studio A" series. ... 'Sui speakers were beautiful bruisin' house rockers back-in-da-daze, maxhifi. Freeing 'sui drivers from their constrictive stock x-overs helps them sound as beautiful as they look. They also sound exquisite with home theatre audio, too. So go simple, & go 'sui!!! 73s para Sactown

 

RE: Simplify Sansui Speaker Crossovers And Enjoy, posted on October 19, 2016 at 07:00:54
Crazy Dave
Audiophile

Posts: 14371
Location: East Coast
Joined: October 4, 2001
 I remember you posting this on the Vintage Asylum some years ago. It should work with the SP-2000, since the midrange layout is similar. The 2000's are parked right now. Your mod is simple, cheap and reversible. Sounds like an easy thing to try. They were rocking speakers when I had them hooked up. It doesn't take much power for them to blast. IMO, even stock, they are a much better sounding speaker than Klipsch Heresy, which I also own.

Dave

 

RE: Simplify Sansui Speaker Crossovers And Enjoy, posted on October 19, 2016 at 07:21:35
maxhifi
Audiophile

Posts: 584
Location: Alberta, Canada
Joined: August 4, 2004
 "even stock, they are a much better sounding speaker than Klipsch Heresy, which I also own."

Wow now this is encouraging! I really excited to get mine operational!

Those crossover modifications sound interesting too - did you compare it to the original crossovers with original components, or to rebuilt original crossovers? I need beg/borrow/buy some sort of calibrated mic before I go down that path though. I've done before/after recap frequency response plots of other 1970s speakers when I had access to a calibrated mic and the difference is not subtle.

 

RE: Simplify Sansui Speaker Crossovers And Enjoy, posted on October 19, 2016 at 16:56:39
FRG7SWL
Audiophile

Posts: 2109
Location: NorCali
Joined: March 26, 2003
 Changed x-overs out of curiosity, maxhifi. Was amazed by increase in clarity-n-clout in modded vs stock. Unlike SP-2500s, SP-1500s already had decent bass response. Adding 10 uf polyprop to larger Coral mid driver solidified nether region, whilst unleashing robust alnico mids (unleashing robust mids is why SP-2500s' squalkers were wired in series, too). Was raised with that guitarist's "Get thy tone from thy amp" mentality, & applied it to hi-fi hobby. Keep us posted on how your modded SP-3005s sound compared to your La Scalas. 73s para Sactown

 

RE: Simplify Sansui Speaker Crossovers And Enjoy, posted on October 20, 2016 at 08:52:18
maxhifi
Audiophile

Posts: 584
Location: Alberta, Canada
Joined: August 4, 2004
 I really like the sound of your approach, I wish I could work that sort of magic working empirically! will definitely post back with impressions of the completed rebuild! I will probably not modify crossovers from stock without a microphone and measurement software to check my work, but I don't really trust me ears enough :) my fear is I would alter the tone to suit one type of music and ruin it for others. I am from an engineering background, not a musical one, soI feel like my judgement is better when I can quantify it somehow. I envy the sort of people who can adjust the speed of a turntable by ear, I'm the type who can notice when it's wrong but needs equipment to get it right.

I have read a lot of reviews of the old Sansui speakers online, and the positive ones all seem to speak about a very large sound, which is something I really enjoy. Negative ones talk about them making a lot of sound, but not a good sound. Reading between the lines, I am quite hopeful that these will do it for me, based on my own musical and sound system related preferences, and the simulations I have done to date.

I hurt my back fairly badly on the weekend doing some home repairs, and am only now back up to the task of using the table saw and wood working tools... Will post a pic when I am done.

 

Japanese Brochure & specs, posted on October 25, 2016 at 14:57:28
maxhifi
Audiophile

Posts: 584
Location: Alberta, Canada
Joined: August 4, 2004



I could find barely any info on these in English, so decided to search yahoo.jp. Up came lots of stuff, of course, I can only look at the photos, but the frequency response graph doesn't show any huge peaks in the bass region.

I tried doing OCR and then google translate, but the result is beyond gibberish.

 

RE: Japanese Brochure & specs, posted on October 27, 2016 at 11:44:27
FRG7SWL
Audiophile

Posts: 2109
Location: NorCali
Joined: March 26, 2003
 Looks like SP-3005s were intended for Japanese market, maxhifi. Using experience from previous 'sui speaker projects, put a 12 uf polyprop on large mid-range driver along with direct-wiring woof(no coils nor inductors). You'll elicit bomb-tastic bass from woof, combined with fat mid response. For those mid squalkers surrounding the tweets, wire them in series & a 6.8 uf polyprop should suffice. Will solidify upper mid response quite nicely. Put a 4.7 uf polyprop on one tweet, & 2.2 uf polyprop on the other. Being positioned side-by-side rather than one on top of the other(like with SP-2500), it shouldn't make much difference which tweet gets which polyprop value. So just use personal preference. Mod one speaker, then compare it to stock. Results should be quite startling. 73s para Sactown

 

RE: Japanese Brochure & specs, posted on October 27, 2016 at 12:09:03
maxhifi
Audiophile

Posts: 584
Location: Alberta, Canada
Joined: August 4, 2004
 Thanks for the ideas! I am about to make a cap order at parts express for the original values, wil toss in some polypropylene caps too for later experimentation. Looking at the frequency response chart I can see this speaker is naturally very strong in the mids! I have an idea that I could also use my minidsp to fix things up a bit, with a small single ended triode amp on the mids and tweeters, and the big powerful push pull amp on the woofers.

I have to wonder how such a pair of foreign speakers, for which Information only seems to exist in Japan first of all ended up here in Canada, only to be abandoned and mistreated and eventually rebuilt.

Cabinets are coming along, so far I've got them built out of 3/4" birch plywood, all corners blocked and glued and screwed, in the spirit of how Sansu made cabinets. The baffles are mounted, and next step is to make cutouts for all the drivers, and then Have them finished. I am going to make a mirrored pair rather than two identical speakers, just because I can so why not. Definitely a bit slower going than I had hoped but should have some sound in a few weeks!

 

New cabinet, posted on December 5, 2016 at 09:11:32
maxhifi
Audiophile

Posts: 584
Location: Alberta, Canada
Joined: August 4, 2004



Here's one of the almost complete new cabinets

Note to self : never buy Chinese made plywood again!

The other one is a mirror image of this one

 

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