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Help required : Bolton 15" woofer

Audiolab 6000A Amplifier

Lionx

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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.

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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.
 

diyaudio

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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?
 
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yogibear

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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.
 

Lionx

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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?
 

yogibear

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It’s neither ported nor sealed. It’s something suggested by a friend from Ukraine, a well read, seasoned audiophile. Well versed in almost everything related to audio.

To give you an idea of the box:

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.

I would suggest, measure TS parameters of the driver first. My driver was high Qts.

Needs to be placed away from corners.

Despite all the awkwardness and strange looks, bass is thundering, open, relaxed and nothing short of life like and concert level.

It’s essentially an H frame open baffle but no walls in the sides behind the driver but all on the front side and driver being placed deeper.

I call it kind of horn loaded open baffle. Very easy to construct.

All above dimensions good for a 15” driver.
 

diyaudio

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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
 

yogibear

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I will dig out pictures for you. But FM must measure your driver for TS parameters. It will help him decide other plans too. It looks like a great driver and just one can do wonders.

The rear of driver is not sealed. The above plan is "dipole horn loaded open baffle".

An H frame with sides walls only in the front. In other words, mount a driver with face inside the cabinet, take off the side its facing the cabinet. I hope you get the picture.
 

Lionx

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

yogibear

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Finally.....

Its called GIP 7331 system. Very popular in Japan. A horn setup. Not a complex design at all. See these pictures:

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These have sealed rear BUT keep it open, DONT seal it. Thats my version of GIP 7331 system.

Regarding TS parameters measurements, see if someone has Dayton Audio DATS V2 in your city. After you have TSP of your drivers and you are keen to try above design, I can help you with exact dimensions.
 

Lionx

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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.
 

yogibear

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If I were you with that Bolton 15" woofer, I will just go ahead and build a box. No, don't worry about rest of the horns etc.

Build a box, 24" wide, 30" high and 16" deep (all 4 side walls), mount the driver. keep it away from rear and side walls. Add a subwoofer plate amp to it and start crossing from 150Hz down to 100Hz and see where it sounds best depending on your front speakers. (keep the rear of the driver open, NOT sealed).

You may hit a jackpot with it ! Best bass I ever heard myself. Defies the Fs of the driver and digs deeper than you would expect.

My 15" woofer was high Qms and Qts and it would put sealed and ported subs to shame. It made "Concert Level Bass"

I wanted to try this with low Qts drivers as well but did not have any.
 

yogibear

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Take it as an experiment. Try not to spend much money. If it sounds great to your ears, build a sturdy box with bracing. Strong, effective bracing is must. Mine was made from scrap MDF pieces, no bracing and I had to put cement bricks inside the box..... But it was divine, musical, effortless, room filling bass. With closed eyes, one would not believe that its just one driver woofer playing. I made second but ran into room interaction problems as soon as I pushed first one near the corner to make room for the other. Hence had to abandon it.

It needs room to breathe, away from rear wall and side walls BUT its the quickest and cheapest way to integrate bass for a 2.1 system. I would prefer doing it with 15" or larger drivers. It has best aspects of both a "Horn" and "Dipole" bass. Can be experimented with 12" drivers too. Doesn't look bad from front as you can just put a grill/cloth in front. Will look like a common boxed speaker.

The person who taught me this, is well respected in audiophile community around the globe. Has made clones of largest, rarest JBL, Altec, Klangfilm, RCA, and other European speakers and swears by the above simple design.
 

Lionx

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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.
 

yogibear

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If successful, wud do just fine with HT too. Mine had as Fs of 40hz but did close to 32hz of room response. No dearth of low notes. Outsmarted my sealed subs doing well near 30 hz.
 

diyaudio

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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.
 

yogibear

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Ever heard a ship”s siren ? A few tracks it played, felt the ship has anchored just outside my door !
 

Lionx

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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.
 

yogibear

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Lionx

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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.
 
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