Modifying vintage Technics honeycomb speakers

[Taavip]

Hi Everyone!

Long time reader, first time poster here.
Recently acquired a pair of Technics SB-6 speakers with 10 inch honeycomb woofers: https://www.hifiengine.com/manual_library/technics/sb-6.shtml

First and probably the most important impression was that they didn't reproduce decent sub-bass frequencies: Between 30-40Hz. It made sense since most that era Technics speakers specs where similar: ~38Hz with -10dB. That's a big drop!
I enjoy bass music (rap, hip-hop, drum and bass, dubstep, ambient etc) where the main basslines lie between 30-40Hz, and really enjoy when those frequencies stand out.

As a background I'm a big fan of honeycomb speakers, and have multiple pairs of Soviet Estonian's produced Estonia honeycomb speakers:

And also their newer younger brothers Audes 012:

They both have 8 inch honeycomb woofers with similar bass response, below is the data for Audes:
Frequency range (±3 dB)36–20000 Hz
(−6 dB)32 Hz

Their box tuning frequency is also around 32-36Hz.

It seems to me that Technics have the box frequency (port frequency) between 50-60Hz:

and I'm wondering will it have any positive results if the port frequency is decreased?

I managed to get some data from the woofers from a Japanese blog site:
http://mikamiaudio.blog60.fc2.com/blog-entry-5.html
fs 41.4, vas 80.2, mms 29.7, qts 0.522, qms 12.9, qes 0.544, le 0.419, l1, 0.332, r1 1.7, re 4.6, sD 380

And did some quick calcs online with the default port (red) and with 200mm length (green) ~34Hz port frequency:

The results are of course not super accurate but it does show small improvement.

If anyone has experience with similar or vintage speakers or with a similar problem, would be happy if you could share it.

 

[A400]

Welcome to AK!

Assuming the woofers are in good condition the obvious answer here is a subwoofer or two. Modification is unlikely to be an overall improvement, otherwise Technics would have done it already. I’m assuming enclosure size can’t change. You might get a tiny bit more bass, but probably not significant and lose some transient response or power handling (guessing a bit here).

 

[jocko_nc]

What he said. Get a pair of musical subs and dial them in where the mains peter out. I prefer "passive" where I run a pair of separate power amps to the subs. EQ them to where they need to be. Amps built into the cabinets are not as flexible nor reliable, IMO. They can be used going forward with any future system or home theater.

 

[A400]

After looking into this a little more, Technics appear to have prioritized efficiency over bass extension, that's why the relatively large woofer doesn't go very deep.

I also started thinking about honeycomb subwoofers. It looks like there are a few options, but a KEF B139 could be interesting if you like vintage and can accept the relatively low power handling. A TL is the obvious choice but an active B139 with one or two passive versions would have quite a nice look to it

 

[Taavip]

Thanks for the welcome and feedback!
I agree and also remember that in order to have higher efficiency you sacrifice either low end or power handling.
In that sense the graphs make sense that a longer vent might not give the extra low end that I'm looking for.

I actually do have a pair of active honeycomb subwoofers that I built back in the days that were meant to play below 50Hz, so they might suit here well.

Out of curiosity I'm probably still gonna try the longer vents, I don't mind if I lose power, usually listen on low-medium volumes (but I appreciate any headroom of course )
I was very surprised that the speakers are in that good shape given the release year of 1981, maybe the previous owner already changed the foam surroundings, they look very flexible and in good condition. I might do a recap for the filters.