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Old 22nd Oct 2021, 12:37 pm   #1
david winter
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Default Modern speakers to improve sound in tube radios

I guess this question has been discussed before, but I wanted to know if one specific type of speaker is recommended to improve sound in restored tube radios, as some models clearly show bandwidth limitations.
Speakers to replace are usually 2.5 ohm types, with a diameter ranging from around 13cm to 21cm.
Thanks !
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Old 22nd Oct 2021, 12:54 pm   #2
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Default Re: Modern speakers to improve sound in tube radios

I think sound quality is really how good the production of it is from the amplifier / output section and possibly the stages before. Try looking at how good the capacitors are in the tone section of the set.

Hope this helps

Ken
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Old 22nd Oct 2021, 12:54 pm   #3
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Default Re: Modern speakers to improve sound in tube radios

Modern speakers are designed for a world full of transistors, where audio power is easily available in large quantities. So they've all sacrificed efficiency for quality improvement. If you change the main speaker expect a loss of volume.

You perhaps just need to add a tweeter, along the lines of the Grundig electrostatic ones that turned up even in some British sets.

Later, Motorola made some ceramic piezo-electric tweeters and one of these might help if you ever come across one.

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Old 22nd Oct 2021, 1:34 pm   #4
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Default Re: Modern speakers to improve sound in tube radios

Some modern speakers are efficient - those for automotive use are quite sensitive, and are typically 4 ohms impedance which is close enough to 3 ohms. It's doubtful if there would be a significant improvement to the sound though, and originality would be lost.
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Old 22nd Oct 2021, 2:14 pm   #5
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Default Re: Modern speakers to improve sound in tube radios

The original speakers in good vintage radios are actually very well matched to the application. They are sensitive, they're usually designed for a high output impedance (pentode) amplifier, and an open back cabinet, and the high frequency response usually is limited, which is a good thing in the application. I have yet to encounter a domestic radio where a wider range speaker wouldn't just show up limitations in the radio itself.
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Old 22nd Oct 2021, 2:54 pm   #6
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Default Re: Modern speakers to improve sound in tube radios

Hi David

This is a problem Roberts Radio had in their larger am only transistor radios and others expanded on by BVWS, - search Hacker Frequency response.

Celestion speakers, for example, showed a quite different response to Elac, both used by Hacker.

Roberts Radio designed their large early am transistor radio using a speaker which had a peaked response at approx 5kHz to "improve" the limited bandswidth of brick filter BBC transmission. Listen to the same on FM and it is not right.

Grundig, noted for the "Grundig Sound," a very listenable response, approached matters differently. First the AM IF bandswidth was chosen @ 3.5Khz, an engineered loudness circuit was constructed, often with lower and upper taps on the volume control, or graphic equalizer viz a Grundig 3028 and similar, which together with a loudspeaker to match the cone extension caused by the lf boost and cone lightness for hf uplift did wonders. Matched by Philips, Telefunken and Saba these made the table top radio sound larger than life.

Open backed radio require a different loudspeaker design to sealed HiFi units because the cone excursion needs to be limited in the first instance whilst the compressed air does it in the second. Use the wrong speaker and the bass notes will bottom the voice coil.

Perhaps, you could state which radio you have which, if from a family of models with varying degree of audio sophistication, might lend itself to retro fitting of tailored circuits.

Chris
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Old 22nd Oct 2021, 4:16 pm   #7
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Default Re: Modern speakers to improve sound in tube radios

I would say - as per David above - add a suitable tweeter. It will boost the treble and you can then have more usable control over the existing tone control(s) to boost the bass, whatever. Note that boosting the bass and treble regions slightly can have the effect of suppressing an often 'squawky' mid range, making vocals more lifelike.
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Old 23rd Oct 2021, 1:44 pm   #8
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Default Re: Modern speakers to improve sound in tube radios

Adding a Tweeter to an AM only Radio could result in very unpleasant sound/transients. A cheap and cheerful way of emphasising the limited bandwidth of an AM Radio would be to clear varnish the centre of the cone covering 1/3 of the cone nearest to the voice coil. As a penniless student I would dope the cone (many times) of a 3" or 4" speaker and that would become my first "Tweeter". The trouble with this thread is we still don't know what kind of set the OP has, nor its speaker size.....!
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Old 23rd Oct 2021, 6:57 pm   #9
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Default Re: Modern speakers to improve sound in tube radios

Quote:
Originally Posted by Edward Huggins View Post
The trouble with this thread is we still don't know what kind of set the OP has, nor its speaker size.....!
I assumed the question to be general rather than specific, as the OP refers to "radios" and "speakers" in the plural.
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Old 23rd Oct 2021, 9:45 pm   #10
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Default Re: Modern speakers to improve sound in tube radios

I can't see how a tweeter could make a valve radio sound better, it has limited frequency output upto around 16kHz, transistor radios may benefit from a tweeter.
It does help to know what the set is to determine what speaker is suitable.
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Old 24th Oct 2021, 8:55 am   #11
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Default Re: Modern speakers to improve sound in tube radios

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Originally Posted by Glowing Bits! View Post
I can't see how a tweeter could make a valve radio sound better, it has limited frequency output upto around 16kHz, transistor radios may benefit from a tweeter.
It does help to know what the set is to determine what speaker is suitable.
Most tweeters cover 5khz to 20khz, the issue not being the upper end capability of a valve radio, but the 'boost' that the tweeter provides from say 5khz upwards. It could make a lot of difference.
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Old 24th Oct 2021, 9:14 am   #12
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Default Re: Modern speakers to improve sound in tube radios

Interesting technical discussion as usual but is it is just me that’s wondering why?

Most domestic valve radios aren’t hifi and weren’t designed as such so if you want to improve the sound by adding a modern speaker why not the whole hog and add a modern radio?

Compared to modern ‘transistor’ domestic radios a well serviced valve radio should sound better even with the original speaker and this is mostly down to the size of the speaker and the cabinets.

John
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Old 24th Oct 2021, 9:17 am   #13
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Default Re: Modern speakers to improve sound in tube radios

The thread doesn't define "modern" in chronological terms. There is no question that the
first generation of moving coil speakers where the coil was mounted on a rigid "spider"
suspension attached to the magnet will not be as sensitive as or have the same
frequency response of the later designs where the coil is attached to a fabric or
rubber suspension.
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Old 24th Oct 2021, 9:19 am   #14
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Default Re: Modern speakers to improve sound in tube radios

A number of top-of-the-range sets from several makers sported tweeters. I don't recall them being switched out when long or medium waves were selected, so they must have thought there was no detriment to the sound.

However, since that era, broadcasters were shifted to the 9kHz spacing channels and their modulated bandwidth curtailed to protect adjacent channels. This reduces the audio bandwidth that can be conveyed. So even with excellent speakers and a wide-ish receiver, AM quality is no longer what it once was. I wouldn't want to lose any more.

Perhaps a dual-cone speaker does as much as can be done?

David
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Old 24th Oct 2021, 9:31 am   #15
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Default Re: Modern speakers to improve sound in tube radios

I'm guessing this is to make them sound more like modern equipment which is better at dealing with the Boom and ting that has been an increasing dominance in pop music probably starting in the 1960's with Disco*.

As anyone who has heard Yoof going down the street with the windows rattling and the Boom Boom Boom it's going to be hard to get that sound on your DAC90A (although if the rubbers are worn the tuning scale will rattle so you're half way there!)

I don't think I would bother, easier to use a smart speaker for that kind of service hidden inside the Radio case if necessary.

* There is always room to speculate when any trend started this is just my take on it.

Cheers

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Old 24th Oct 2021, 9:36 am   #16
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Default Re: Modern speakers to improve sound in tube radios

I am currently playing with a Philips mono knob radio. Have removed the electronics and have re installed the speaker in the cabinet. Playing 78's via an Ortofon 78 mm cartridge and a a Quad 303 power amp, the sound is most impressive.

The speaker has a fixed flared cone which looks like the whizzer cones on 19 50's / 60's Goodmans speakers. Since it is rigedly fixed the idea must have been to disperse the treble.
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Old 24th Oct 2021, 11:13 am   #17
david winter
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Default Re: Modern speakers to improve sound in tube radios

I realize I totally forgot one essential parameter: my initial question concerns radios that I convert to the FM band with my FM module (which preserves the tube amplifier and allows tuning using the dial).
In many cases, the FM sound quality gets limited by the actual speaker (especially in radios from the 1930s / 1940s) and therefore I wanted to know what wideband speaker (or similar) would improve the quality to hear the FM with a better sound.
Sorry for having forgotten that detail (I never considered improving the sound in an old, unconverted radio).
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Old 24th Oct 2021, 11:28 am   #18
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Default Re: Modern speakers to improve sound in tube radios

That would make little difference to me although it may to others, adding FM is just about getting a choice of stations (rather limited on AM these days).

I would still be happy for my 30's radio to sound as it does, just with more choice

Same applies to Bluetooth and DAB conversions.

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Old 24th Oct 2021, 12:13 pm   #19
david winter
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Default Re: Modern speakers to improve sound in tube radios

Of course, but some speakers are more limited in bandwidth than others, hence my question to improve the sound quality for FM-converted radios.
In most cases I'm fully satisfied with the sound quality, but in some cases it can obviously be much better and that's where the question becomes interesting.
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Old 24th Oct 2021, 3:33 pm   #20
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Default Re: Modern speakers to improve sound in tube radios

Quote:
Originally Posted by david winter View Post
I radios that I convert to the FM band with my FM module (which preserves the tube amplifier and allows tuning using the dial).
Sorry for the slight off topic but is this something commercially available?
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