Help required : Bolton 15" woofer

[Lionx]

Gurus,
Recently I got chance to pick a good old Bolton from a scrap dealer, apparently was used in a single screen Cinema theater. It is a monster, weighs more than 15kg, solid build, cone was intact, I just picked even though there were no plans for it. I don't know much about it apart from the written info of 250W and 8ohm, please help me with more details of this if anyone has a similar one or experienced.
> Can this be a Full range one or can it be used as a sub woofer as well.
> What is the recommended amplifier wattage
> Any recommendation for the box designs.





My current setup is Marantz SR5200 with a pair of self made TriTrix (http://projectgallery.parts-express.com/speaker-projects/tritrix/) and NAD 808 center channel. Even though Tritrix has good bass for Music, the lowest it could go was 50Hz which was not doing justice for movies. I was looking to add a Sub to the setup and was thinking whether the Bolton would be a good fit with a 250W plate amplifier.

 

[diyaudio]

Looking at the back of the cone it looks like a woofer. For home use it would make a good subwoofer. Whats the coil size?

 

[Lionx]

Use it as a subwoofer. Whats the coil size?

Not sure about that but the magnet hole dia is 1.01inch so my guess would be 1inch.

 

[Lionx]

WE bass bin and it will shake the house, just one is enough if you have good space. Best bass you would have ever heard.

Thanks, any suggestions for the box. Ported or sealed?

 

[diyaudio]

18mm or 24mm ply. Construct a box of internal dimension about 24” wide and 30” high. Keep one side open and mount the driver from rear facing front. So it would look like a box with front open, and driver mounted on the rear wall facing front with side walls. It’s kind of awkward with driver chassis and magnet hanging out from the rear wall. You can put a grill in the front. Centre the driver on the rear wall.

Pls provide more links, photos etc
The rear of driver is closed at one end (ground) and open at the top. This forms a cavity which will result in strong quarter-wave resonance. 30" height corresponds to about 115 hz for this resonance which is in bass range

Anyway, it would be interesting to see more info of this dipole variation

 

[Lionx]

A picture would definitely help, that's a complex design.
How do you propose to measure the TS parameters, any instructions available?

 

[Lionx]

I am very much keen to try this setup, this would work without the horns, right? I don’t want to add more components into it.
Any good plate amplifier available locally, if not I will try to pick the Dayton 250w one from parts express.

 

[Lionx]

I am going to do just that, finding the TS parameters looks impossible. I have 3/4 mdf ta home, i hope that would do.

I understand this design works well with music, but can you tell me how good it for movies thats where I wanted it to shine. Any idea how low yours go.

 

[diyaudio]

The rear of driver is closed at one end (ground) and open at the top. This forms a cavity which will result in strong quarter-wave resonance. 30" height corresponds to about 115 hz for this resonance which is in bass range

The above concern is not valid. I had assumed the speaker to be corner loaded.

 

[Lionx]

The box is being made with 18mm ply as per the dimensions given by yogi, thanks brother. I need to find a good plate amp next.

 

[Lionx]

Yes i might go for the Dayton one from parts express as plate amplifiers are not available in local stores.

The box is completed and I admit it's quite intimidating by the size. I would do a sound test before doing the final touches.

 

[Lionx]

Good Luck ! I hope it sounds just as wonderful as mine did.

Try to buy sub plate amps with speaker level line inputs as well. You can always use these amps with any other project. These two look good:

https://www.parts-express.com/dayton-audio-spa250-250-watt-subwoofer-plate-amplifier--300-803

https://www.parts-express.com/yung-...-amplifier-module-with-6-db-at-30-hz--301-510

Sometimes, the woofers sound better with speaker level inputs as compared to line-level inputs. You should try both.

Can you please post a pic of yours for reference.

 

[Lionx]

You seems to have plenty of space to run this, it might be a problem in a flat living room.

 

[prem]

yogibear, Viren builds horns like these

 

[Lionx]

This is how it ended up with, apologies for the poor quality pics.





I haven't given any bracing yet as there are plenty of tasks left. I couldn't find a plate amplifier in the local market yesterday so hooked up with a puny 50W STK stereo amp and played some songs via Soundcloud from mobile. Oh boy, this is insane even when running as Full range and am sure it can do wonders as sub with 200W plate amp. The mid and low are so punchy and it fills the hall of size 10x20 with ease.

Now the hunt for plate amp begins, any pointers in the local market? Partsexpress shipping costs to india is more than the amp itsef.

 

[kapvin]

I remember this woofer.

this was part of their Pro range which included a horn tweeter as well. Very high efficiency. its also one of those rare woofers from bolton which came with a cast basket (it is sand cast instead of die cast). Most Bolton speakers had stamped baskets.

while Bolton never published T/S parameters, this looks like it was more a low qts product, so might not be excellent in an OB. Of course YMMV, and there is no subsitutes for a measurement check.

Kapil

Gurus,
Recently I got chance to pick a good old Bolton from a scrap dealer, apparently was used in a single screen Cinema theater. It is a monster, weighs more than 15kg, solid build, cone was intact, I just picked even though there were no plans for it. I don't know much about it apart from the written info of 250W and 8ohm, please help me with more details of this if anyone has a similar one or experienced.
> Can this be a Full range one or can it be used as a sub woofer as well.
> What is the recommended amplifier wattage
> Any recommendation for the box designs.

View attachment 26846

View attachment 26847
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My current setup is Marantz SR5200 with a pair of self made TriTrix (http://projectgallery.parts-express.com/speaker-projects/tritrix/) and NAD 808 center channel. Even though Tritrix has good bass for Music, the lowest it could go was 50Hz which was not doing justice for movies. I was looking to add a Sub to the setup and was thinking whether the Bolton would be a good fit with a 250W plate amplifier.

 

[Lionx]

I remember this woofer.

this was part of their Pro range which included a horn tweeter as well. Very high efficiency. its also one of those rare woofers from bolton which came with a cast basket (it is sand cast instead of die cast). Most Bolton speakers had stamped baskets.

while Bolton never published T/S parameters, this looks like it was more a low qts product, so might not be excellent in an OB. Of course YMMV, and there is no subsitutes for a measurement check.

Kapil

Thanks Kapil for identifying this, do you have any pics of a similar one along with the horn. It came from a theatre as per the shop owner but there are chances of being a PA.

 

[diyaudio]

Now the hunt for plate amp begins, any pointers in the local market? Partsexpress shipping costs to india is more than the amp itsef.

Do note that dipoles dont need much power to reach xmax.

 

[diyaudio]

Also the fact that 15" inch drivers designed for pro audio have a much higher sensitivity, probably you will reach xmax with just 50 watts

 

[diyaudio]

Pls provide Eq details, if you are using any?