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Speaker - Amp Match

Postby damartin » Tue Apr 27, 2021 11:15 am

Hello everyone, please clarify this for me:
I own a Laney LC15R 110, so a 15w amp and I want to replace the stock speaker with a new one. I understand the matching of impedance (my amp has 8-16 ohm speaker out capability). But I am not clear about wattage. I intend to buy a Celestion VT junior 10", 16ohm, 50 W. Is this OK in terms of wattage? Cheers!
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Re: Speaker - Amp Match

Postby Sam Spoons » Tue Apr 27, 2021 11:25 am

Yes, that'll be fine :thumbup:
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Re: Speaker - Amp Match

Postby Wonks » Tue Apr 27, 2021 11:38 am

That's fine. Speaker wattage is purely a measure of how much power a speaker can take for a decent length of time without causing damage e.g. voice coil burning out.

Your Laney is 15W with a clean output, and will probably put out nearer to 25W with everything turned up fully and it distorting, so a reasonable margin of safety is always a good idea.

Celestion's wattage ratings are good ones, whilst some others manufacturer's wattage ratings are on the 'hopeful' side of things.

But I would suggest an 8 ohm speaker for the replacement. 8-16 ohms is the allowable range, but 8ohms will be the standard fitting and the best match for the output transformer.

A valve amp will normally cope with one standard speaker rating step up in impedance e.g. 8 to 16 ohms, but with less output and an altered frequency response. A lot will also cope with a step down, e.g. 8 to 4 ohms, but as Laney don't recommend this, the output transformer could well get damaged if you went that low. But the Laney is designed for an 8 ohm speaker, so that's what the replacement should be.

The external speaker output disconnects the internal speaker (unless it's been modified not to), so there's no benefit in fitting a 16 ohm speaker, as you wont get an equivalent 8 ohm impedance load if you pair it with a 16 ohm external speaker. You'll just get the external 16 ohm speaker.
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Re: Speaker - Amp Match

Postby damartin » Tue Apr 27, 2021 11:47 am

Thanks for substantial reply. The thing is that there is only a 16ohm version of this speaker available in the online shop I am using... I'll continue searching for the 8ohm version. Sounds convincing what you say. Especially that Laney's outputransforner tends to get hot...
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Re: Speaker - Amp Match

Postby Wonks » Tue Apr 27, 2021 11:53 am

Well, 16 ohms will reduce the power drawn slightly. But the fact that it isn't recommended to go down to 4 ohms does indicate that it's rather a lightweight transformer.

If you are in the UK, then have you used Lean Business? They are my normal supplier of speakers. They have the 8 ohm in stock and they ship Celestions free.

https://www.lean-business.co.uk/eshop/c ... gt825bmmh5
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Re: Speaker - Amp Match

Postby ef37a » Tue Apr 27, 2021 12:47 pm

Wonks wrote:Well, 16 ohms will reduce the power drawn slightly. But the fact that it isn't recommended to go down to 4 ohms does indicate that it's rather a lightweight transformer.

If you are in the UK, then have you used Lean Business? They are my normal supplier of speakers. They have the 8 ohm in stock and they ship Celestions free.

https://www.lean-business.co.uk/eshop/c ... gt825bmmh5

Hi Wonks, you might have some insight into that Laney design I don't but usually with output transformers the most efficient 'match' is when all the windings are used. Very high quality amplifiers use multiple secondary windings and series/parallel them to give the best result. Guitar OPTs never do that AFAIK so an 8R winding will only be using about 75% of the copper.

Not that it matters much in practice but I would like to read your comments?

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Re: Speaker - Amp Match

Postby Wonks » Tue Apr 27, 2021 1:44 pm

Well the standard speaker is 8 ohms.

8-16 ohms is the text on the external speaker socket.

Only one tapping on the transformer, not an 8 ohm and a 16 ohm output. The manual says the internal speaker is disconnected when external speaker is used.

Schematic here: https://www.thetubestore.com/lib/thetub ... ematic.pdf
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Re: Speaker - Amp Match

Postby ef37a » Tue Apr 27, 2021 6:04 pm

Wonks wrote:Well the standard speaker is 8 ohms.

8-16 ohms is the text on the external speaker socket.

Only one tapping on the transformer, not an 8 ohm and a 16 ohm output. The manual says the internal speaker is disconnected when external speaker is used.

Schematic here: https://www.thetubestore.com/lib/thetub ... ematic.pdf

Ah. Gotcha! I was under the impression from the OP's post that the amp had 16 and 8 Ohm taps.

As you were.

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Re: Speaker - Amp Match

Postby Wonks » Tue Apr 27, 2021 6:12 pm

If there had been both, then 16 ohms would be my choice as well.
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Re: Speaker - Amp Match

Postby ef37a » Tue Apr 27, 2021 6:16 pm

Wonks wrote:If there had been both, then 16 ohms would be my choice as well.

Quite. Rather mean of Laney not to give the two impedance choices? 16 Ohms is practically THE default impedance for guitar speakers.

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Re: Speaker - Amp Match

Postby Murray B » Tue Apr 27, 2021 8:25 pm

Make sure you have enough room for the new speaker in the cab. I only just got away with replacing the stock Jensen speaker in my Laney VC15 with an 8 ohm Ragin Cajun 10" speaker as the magnet and chassis was significantly larger than the Jensen.

The result is the the speaker magnet is about 5mm away from the power valves - sheer dumb luck and quite disconcerting - over 15 years later it still works but it still seems way to close to the valves for comfort!

While I was at it I added a extra speaker extension socket that adds an addition cab in series (due to the 8 ohm internal speaker) when the jack is plugged in so that I could use the internal speaker at the same time as an external cab. However if the contacts that keep the circuit made when the plug isn't in ever fail it will probably kill the amp - again 15 years in and it's still ok...

I'd thoroughly recommend going for the most sensitive / efficient speaker you can find. The difference the Ragin Cajun made was remarkable - the amp went from very early break up and running out of headroom to being able to keep up on fairly noisy stages with headroom to spare.
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Re: Speaker - Amp Match

Postby Sam Spoons » Tue Apr 27, 2021 11:37 pm

I built an '18 watt' from an Ampmaker.com kit a few years ago. It's been my goto amp for gigs and in the studio since and sounds great. I went for the most efficient speaker I could buy, a Celestion Vintage 30, at the time but many years earlier I had a Celestion Sidewinder as an extension speaker for my (much missed) MusicMan RP65 combo. The V30 has a sensitivity of 100dB and other current Celestion 12" guitar speakers range from 96dB to 100dB but the Sidewinder had an edgewound voicecoil like the big EV speakers MesaBoogie used in the Mk4 combo and a sensitivity of 103dB making it the most efficient guitar speaker I've come across.

After several years of using a cannibalised combo cab from a Chinese 'Tube 30' combo I've finally bought a nice cabinet for my 18 watt and am debating what speaker to install (the V30 can stay in the cab with the Tube 30 as a gig amp). I'm attracted to the idea of a Neodium magnet for light weight (2kg less than an equivalent Ceramic magnet chassis) but the most efficient is 3dB down on the V30. So I'm 'dazed and confused' and torn between going as loud as I can* and chasing tone... The frequency plots Celestion publish show the differences between their 12" guitar speakers to be fairly subtle but finding the perfect one to complement the voicing of my 18 watt is probably going to be a bit of a lottery.

* Max level is less of an issue now I'll have the Tube 30 as a gig amp but my regular drummer is a fairly heavy hitter so in rehearsal (in my studio) the 18 watt needs to be able to keep up) but I'm doubtful that 3 or 4 dB is significant enough to sway my choice.
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