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Bassreflex - block the ports and add a subwoofer?

89.10.104.47
Posted on March 25, 2016 at 12:09:35
iodemus
Audiophile

Posts: 170
Joined: October 21, 2010
 I have Tannoy 12" Red's from the sixties in reinforced Tannoy-designed ~120 litres corner reflex-enclosures with rebuilt crossovers. Nice sounding apart from sloppy bass. Want to improve by blocking the reflex ports and add a B&W DB1 sub. Any opinions?

 

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RE: Bassreflex - block the ports and add a subwoofer?, posted on March 25, 2016 at 14:43:48
moray james
Manufacturer

Posts: 1599
Location: Calgary on the Bow
Joined: May 19, 2002
 block the vents and pack the cabinet solid with high density fiberglass on edge so the rear wave fires into the cut edge of the fiberglass board NOT into the flat surface of the material which is quite reflective. This makes for an astounding difference in absorption. You might find you don't need a sub.
moray james

 

RE: Bassreflex - block the ports and add a subwoofer?, posted on March 25, 2016 at 16:05:34
iodemus
Audiophile

Posts: 170
Joined: October 21, 2010
 I used wool felt and lots of Acousto-Q as recommended by Tannoy. Nothing on the front baffle.
Blocking the ports means loosing lower frequencies, but the DB1 will do it better. The DB1 is ordered. I think it will do a perfect job as it can be adjusted, phase corrected and equalized to fit the room acoustic in perfection with the help of a measuring microphone and test signals.
- I hope.

Regards,
Johnny

 

Seriously!? block the ports and add a subwoofer?, posted on March 25, 2016 at 18:38:16
bare
Audiophile

Posts: 1879
Joined: April 14, 2009
 Look to your inadequate amplifications/gear FIRST.
Rather than mutilating simple stoopid boxes to try and achieve what these things normally do with out any additional fooling with
These CAN produce Deep Clean Fast Bass... by Any yardstick.
Seriously Impressively so.
IF the Upstream gear is worthwhile.. Or even Passable :-)

Here Lookit these:
http://truefi.blogspot.ca/2016/02/the-truefi-tannoy-enclosure-manufacture.html

 

RE: Seriously!? block the ports and add a subwoofer?, posted on March 26, 2016 at 01:40:50
iodemus
Audiophile

Posts: 170
Joined: October 21, 2010
 I have been in doubt if I should comment your fart.

The article you are linking to is about a HORN-cabinet. I have a BASSREFLEX-cabinet. It has the same well known problem: "the paper cone was absolutely not able to perform its dedicated frequency ends, i.e. the lower frequencies below 150 hz"
The B&W DB1 can handle the low frequencies perfect, and it is NOT a cheap "home theater" device.
What is "inadequate" with McIntosh C2200, 275 and Sony's SACD flagship? Answer me.
I have made speakers and SEDHT amps for more than 50 years without getting a religious attitude to "hifi" .
Good luck.

 

RE: Seriously!? block the ports and add a subwoofer?, posted on March 26, 2016 at 07:08:44
Scott L
Audiophile

Posts: 353
Location: Knoxville
Joined: February 2, 2001
 Yes. Generally, systems with a devoted low frequency section sound better, if the next "up in progression" (mid-bass) section is sealed. The phase response is more linear and lends itself to the addition much better.

 

RE: Bassreflex - block the ports and add a subwoofer?, posted on March 26, 2016 at 14:51:00
moray james
Manufacturer

Posts: 1599
Location: Calgary on the Bow
Joined: May 19, 2002
 if you block the ports you will lose some bass level but you will actually widen your bandwidth and hear deeper bass. You will be switching from 24 db per octave roll of at resonance to 12 db per octave below resonance so you will in fact get to hear deeper bass when sealed than you will with the vents. Why not try it is easy to do and totally reversible. You might like it better this way. If you want more bass then add more cabinet damping to increase the apparent cabinet volume.
moray james

 

Do whatever you want :-), posted on March 26, 2016 at 20:17:04
bare
Audiophile

Posts: 1879
Joined: April 14, 2009
 Clearly you Have NO concept of what the Red is capable of.
You May be the ONLY Reds Owner on the Planet that thinks a Sub is required or even of Use.
IMO sell the rascals and Buy yourself: some Polks, a pair of Subs and a Holiday with the proceeds

 

RE: Do whatever you want :-) Holiday!, posted on March 27, 2016 at 02:08:51
iodemus
Audiophile

Posts: 170
Joined: October 21, 2010
 Of course I do, and today I go on a holiday with my wife.
When back the Bowers & Wilkins DB1 subwoofer will be delivered.
The Tannoy's bassreflex ports are blocked which have relieved them from the bothersome sloppy "bass".
They are ready to connect to the DB1 which do the job much better.
There has been some improvement the last 50 years worth to implement.
Sadly you haven't or will not discover that.
What kind of amplification do you use with your Polk speakers?

 

RE: Do whatever you want :-) Holiday!, posted on March 27, 2016 at 04:17:02
b.l.zeebub
Audiophile

Posts: 9361
Location: 52deg 28'N,1deg56'W
Joined: April 17, 2006
 You'll need two 'subs' and a relatively high xover frequency.

If you block the ports the Tannoys will start to roll off between 150 and 200Hz.
Enclosure size has very little influence on bass extension when sealed, doesn't make much difference if the box is 30L or 300L.

If you want to get deep tight bass from your Tannoys without turning them into 3ways you absolutely must use a high-current, high DF transistor amp. Regardless of age Tannoys never give their best with valve-powered amps and will suffer from mushy bass and consequently muddled mids.
The biggest improvement when I added woofers to my DCs was not in the bass but in the vastly increased clarity in the mids.

 

RE: Bassreflex - block the ports and add a subwoofer?, posted on April 1, 2016 at 16:38:54
Wojciech
Audiophile

Posts: 4123
Joined: June 23, 2009
 How's that rebuilt crossover working out for you compared to stock tannoy brick? I have reds 10 in closed in ~70 old Leak box (I like particle board enclosures ) on low stand it is partially filled . It only came to life with Leak TL50 amps which I had to sell. I could not find diagram for 10 reds .It is lost so I was going to use 12" version schematic and lose matching transformer for LF cone which has 2.8 ohms DCr.

 

RE: Bassreflex - block the ports and add a subwoofer?, posted on April 2, 2016 at 02:42:38
iodemus
Audiophile

Posts: 170
Joined: October 21, 2010
 The crossovers were rebuilt with better components of exactly the same values. Air coil inductors, drifted resistors replaced, changed to oil/paper caps and better wiring.
The Lancaster corner speakers sound better, more transparent. The cabinets were built of 25mm solid pine wood after Tannoys drawings. Further reinforced with internal rods and ribs Like Bowers & Wilkins do it. Dampened with glassfibres and Acousto-Q. Effective internal volume and bass port are similar to original design.

Don't use schematics for other Tannoy models! You must get the exact crossover designed for your unit.
I found X-over for the 10" monitor gold on the web, but I doubt they are similar to the reds. May be Troels Gravesen in Denmark can help.
Good luck!

 

RE: Bassreflex - block the ports and add a subwoofer?, posted on April 2, 2016 at 14:58:16
Wojciech
Audiophile

Posts: 4123
Joined: June 23, 2009
 Unfortunately , diagram for 10 Red is lost. Tannoy doesn't have it.It probably burned with their archives . I tried to ask around and even folks in Japan to no avail. Nobody wants to touch sealed , bitumen filled original crossover and I can't blame them since I'm not willing to do it myself either. Looking at entire Red line , meaning 3 models it's kind of obvious that the LF is not filtered just the low dcr coil gets matching transformer to bump up the impedance to 15 Ohm and HF filter must follow 12" model with discrete L pad to match output. Similarly to progression in tANNOY Gold line . I do have 10" Gold unit Troels worked on, and crossovers are not interchangeable.

 

10" Red crossovers, posted on April 3, 2016 at 12:25:41
iodemus
Audiophile

Posts: 170
Joined: October 21, 2010
 "Nobody wants to touch sealed , bitumen filled original crossover"

In order to rebuild the crossovers for my 12" Reds, I opened one of them. Inside was no bitumen or other stuff, just the clean components in the enclosure. Hope you find one as the Reds are the very best of the old Dual Concentrics.

 

RE: 10" Red crossovers, posted on April 3, 2016 at 20:13:33
Wojciech
Audiophile

Posts: 4123
Joined: June 23, 2009
 Thank You . If that's the case I will open one of mine as well. I was convinced that the closed crossovers were filled with epoxy or bitumen and even if I open the box I will have to chisel the components and most likely ruin the assembly in the process.
Best, W

 

RE: 10" Red crossovers, posted on April 4, 2016 at 02:03:00
iodemus
Audiophile

Posts: 170
Joined: October 21, 2010
 I don't know if yours are similar to mine, but I heated the encosure on a hot plate and used a steel spatula to separate the soldered thin plates. Be careful not to destroy any parts. When opening and identifying the components you can make a schematic and build crossover with modern high quality parts. I used low-DCR air inductors, large oil/paper capacitors and the best resistors exactly as the original values. The plug was bypassed by soldering directly to the tags, and the crossover was built into a wooden box and attached in the lower end inside the cabinets. The small IIILZ cabinets are probably best to have them outside. What about stands with the X-overs inside?
Consider bracing/stiffeners inside the cabinets. At that time Tannoy used thin plywood, like in my Corner Lancasters which I burned. Better cabinets were made of 1" solid pine, heavily braced with braces and stiffeners. Internal volume is exactly as the originals.
Good luck!

 

RE: Bassreflex - block the ports and add a subwoofer?, posted on April 6, 2016 at 13:30:51
Retsel
Audiophile

Posts: 1238
Joined: April 17, 2000
 Something to consider. If the woofers use alnico magnets, one reason why the bass may sound a little sloppy is if the magnets have lost some of their strength. They, of course, can be remagnetized.

Retsel

 

Tannoy Ticonal-G magnets don't deteriorate by normal use., posted on April 6, 2016 at 15:47:18
iodemus
Audiophile

Posts: 170
Joined: October 21, 2010
There are 29 groups and numerous subgroups of Alnicomagnets.
Different alloys of 5-24% Cobalt, 8-10% Aluminium, 6% Copper, some Iron and Titanium. Even Dysprosium, Holmium and Niobium has been used in very small amount, but not in speakers. Tannoy call their Monitor Silver/Red/Gold Dual Concentrics magnets for Ticonal-G .
Loosing their magnetic force by time don't happen unless exposed to >450 centigrades or mechanical impact resulting in chipping or cracks.

Johnny

 

RE: Bassreflex - block the ports and add a subwoofer?, posted on April 19, 2016 at 04:34:48
thump
Audiophile

Posts: 416
Joined: April 19, 2016
 yeah yeah yeah!

block those ports! if it's ported... it's distorted! i've always been a fan of sealed speakers after liking a friend's pair of 4 1/4" infinity 2 ways that had the tightest bass i'd ever heard, if not the deepest and after learning more about acoustic suspension in audio magazine, decided i'd never own a pair of ported speakers.

port lovers really get bent out of shape when you point out all the ways ports distort: phase, overhang, transient smearing, less woofer control & that dreaded 1 note bass resonance and will deny the distortions no matter how many technical papers you throw at them.

if you want more bass out of acoustic suspension, either add more power with a bass boost/EQ or add more woofers for higher efficiency. bass rolloff is the ONLY negative with sealed.

i just bought a pair of nice 96dB 8" 2 way proels for $100 for a bicycle trailer system and plan to plug their ports as soon as i add a pair of 12" high efficiency 12s in a sealed car box.

what you lose in extension plugging ports, you gain in speed and clarity. resonant bass gives me a headache.

 

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