Wanting to build 2 small subwoofers to go on either side of my fireplace - advice appreciated

[sarumbear]

I would talk to Rythmik. They used to sell their 8" servo woofer in a kit for custom installs. They no longer selll the kit, but I think you can piece it together with separate drivers and associated plate amp. They would be a good source for what's possible. BTW, their 8" servo woofers in a sealed enclosure go down to 20 Hz (-3 dB) when used with their complimentary amps

Rythmik Audio servo subwoofer 8" FM8

An 8” at 20Hz and at 2” peak to peak excursion (which is huge) will only generate 95dBSPL. A port will increase the SPL but not enough to satisfy a decent output. Naturally, decent is different on each scenario. I think a larger driver mounted sideways is a better solution. 8” driver is too small for a subwoofer.

 

[Pygmy]

Maybe I missed it? Its important to know what your using for main speakers?

I'm using DIY full range speakers.

 

[Keith Conroy]

I'm using DIY full range speakers.

Sorry to keep pressing with questions. Are you using these sub woofers to supplement the Low Frequency response of what I'll call your mains speakers? If so, it's very important to get some details on your main speakers. Size efficiency how low they go in Freq..........Etc?? I think you could possibly use multiple smaller sub woofers? It will be about how low you need to go & how much SPL needed?

 

[sarumbear]

Sorry to keep pressing with questions. Are you using these sub woofers to supplement the Low Frequency response of what I'll call your mains speakers? If so, it's very important to get some details on your main speakers. Size efficiency how low they go in Freq..........Etc?? I think you could possibly use multiple smaller sub woofers? It will be about how low you need to go & how much SPL needed?

He is using a small subwoofer. Have you checked the measurements he gave, noticed the image he posted?

Why would you care about the main speakers. That is to define the subwoofer amplifier/filter, which is not yet the topic.

 

[Keith Conroy]

He is using a small subwoofer. Have you checked the measurements he gave, noticed the image he posted?

Why would you care about the main speakers. That is to define the subwoofer amplifier/filter, which is not yet the topic.

I saw an image of a space he has on each side of a fireplace. Maybe I missed an image?? I'm not sure what your trying to say with your comment? If you design a subwoofer in a small space you have limits. Is this subwoofer meant to compliment main speakers? If so I want to know what those are? In my view what the main speakers do certainly impact the subwoofer design needs!

 

[sarumbear]

I saw an image of a space he has on each side of a fireplace. Maybe I missed an image??

Yes.

I'm not sure what your trying to say with your comment? If you design a subwoofer in a small space you have limits. Is this subwoofer meant to compliment main speakers? If so I want to know what those are? In my view what the main speakers do certainly impact the subwoofer design needs!

You are repeating yourself but you are not clarifying why we need to know the main speakers. What specification of a subwoofer will be affected by the speakers they will augment?

Obviously, the poster wants to extend the bass response of the existing speakers. What other use a subwoofer has?

 

[Keith Conroy]

Yes.

View attachment 239467


You are repeating yourself but you are not clarifying why we need to know the main speakers. What specification of a subwoofer will be affected by the speakers they will augment?

Obviously, the poster wants to extend the bass response of the existing speakers. What other use a subwoofer has?

I can appreciate another opinion. However its starting to sound like your trying to be a posting policeman. The original poster ask for some advice on a subwoofer design in a very small space. I ask for some additional system information from this poster. If he chooses not to give it that's his call? I tried to clarify at some level to you why I ask? From there for you to agree or disagree is up to you? What do you care if I want to know more about his system??

 

[Timcognito]

How about using a pair of KEF B-139. Several used on ebay <$100/pair. Or better use 4 with one each out phase per:

Tips making Isobarik Chamber Bass woofers with 4 x B139’s

Need basic advice to make a pair of magnet to cone configuration Isobarik sealed chamber bass woofers. I am confident with making the cabinets just not the technical side. I have 4 x B139 SP1044 2 Kef Concerto Falcon Crossover Dn12 Upgrade. Can I connect 2 bass units to one bass...

www.diyaudio.com

Or New: https://www.falconacoustics.co.uk/falcon-b139-8-ohm-kef-b139-sp1044-replacement-woofer.html

 

[Doodski]

How about using a pair of KEF B-139. Several used on ebay <$100/pair. Or better use 4 with one each out phase per:

Tips making Isobarik Chamber Bass woofers with 4 x B139’s

Need basic advice to make a pair of magnet to cone configuration Isobarik sealed chamber bass woofers. I am confident with making the cabinets just not the technical side. I have 4 x B139 SP1044 2 Kef Concerto Falcon Crossover Dn12 Upgrade. Can I connect 2 bass units to one bass...

www.diyaudio.com

I've had and used the B139 and it was a wonderful woofer BUT the suspension stuff hardens after time and the woofer becomes low compliance.

 

[Timcognito]

I've had and used the B139 and it was a wonderful woofer BUT the suspension stuff hardens after time and the woofer becomes low compliance.

One can get new and improved units, see edit above.

 

[sarumbear]

The OP is limited with volume and especially depth behind the woofer. Isobarik is not exactly a volume saver option.

 

[Duke]

The OP is limited with volume and especially depth behind the woofer. Isobarik is not exactly a volume saver option.

True. A tall, narrow, and somewhat deep cabinet is theoretically a candidate for a vented box, as the cabinet height is reasonably likely to allow adequate port length, which is not always easy to shoe-horn into a subwoofer cabinet.

How about using a pair of KEF B-139. Several used on ebay <$100/pair. Or better use 4 with one each out phase per:

Tips making Isobarik Chamber Bass woofers with 4 x B139’s

Need basic advice to make a pair of magnet to cone configuration Isobarik sealed chamber bass woofers. I am confident with making the cabinets just not the technical side. I have 4 x B139 SP1044 2 Kef Concerto Falcon Crossover Dn12 Upgrade. Can I connect 2 bass units to one bass...

www.diyaudio.com

Or New: https://www.falconacoustics.co.uk/falcon-b139-8-ohm-kef-b139-sp1044-replacement-woofer.html

Wow that brings back memories. First pair of speakers I built in 1979 used KEF B139 SP1044 woofers in transmission lines. Back in those day the cool kids were into transmission lines, which did some things well and other things not so well, at least at my amateur level.

I subsequently put them in an isobaric subwoofer, and found out the hard way that as the inner woofer increases the effective box size seen by the outer woofer, the outer woofer becomes susceptible to over-excursion and snapping the voice coil against the backplate. Sounded like a machine gun, gave me a full-on adrenalin dump, and time slowed down while I lunged for the volume control knob. (Kept that little fiasco to myself to protect my imaginary "cool kid" status, but I'm no longer cool so there you go). The B139's one-way Xmax was about 4 mm, and its one-way Xlim (damage limited excursion, which I ran up against) was only about 6 mm. Those figures were probably not bad at the time, but would be considered abysmal today. Presumably Linn used a custom long-excursion version of the B139 in their big Isorarik speakers.

 

[sarumbear]

Presumably Linn used a custom long-excursion version of the B139 in their big Isorarik speakers.

I was a friend of late Julian Vereker. He opened a Linn Isobarik he was using to demo his amps and we saw the standard B139 woofers. I owned a tri-amped Isobarik with NAIM amps. it did hit bottom with loud bass.

 

[sarumbear]

One can get new and improved units, see edit above.

It has more power handling capacity but no mention about Xmax, which is most crucial parameter on a woofer.

4mm Xmax of the original is impossibly short for sub frequency use. They are near equivalent to a 10” driver, which will require 4mm Xmax at 90dBSPL at 1m even at 30Hz. Not much use for a subwoofer is it?

I also don’t get why they bothered to increase the power capacity to 150W. The driver’s sensitivity is 87dBSPL/W. At 150W the driver will produce 109dBSPL but that will be displacement limited below 85Hz. In other words a driver that can only match a modern 2-way speaker on the low end but can’t be used in a 2-way design as you need a mid-range driver to reach the tweeter crossover range. What is the use of a large 3-way design with a limited capacity woofer then?

I guess if they kept the TS parameters the same they can be used as replacement for vintage speakers.

 

[diyhobby]

I have a big drop down projector screen that drops in front of the fireplace.
Next to the fireplace - left and right - are two bookcases, BUT there's a 21cm space between the fireplace and those.
So - I have on both sides a spot of 21cm wide, 48cm high, 30cm deep that's not actively being used / could be used by a nice project..

I'd like to fill these 2 spaces with small subwoofers.
The width limitation means 8" drivers...

So - what's the best I can do within these limits - 21x48x30cm, with the driver on the 21cm side..?
What are the best 8" subwoofer driver options, and what can I do with them?
View attachment 239067

did you make the subwoofer if yes can you share how is it and what is used