Modular Speaker - Basis for my DIY experimenting future

[Westy37]

Alrighty…… I’m fairly new to DIY audio but I have grand plans. I understand that designing an audio system is complicated and that it takes time and perseverance but I’m an obsessive kind of guy so really, this kind of hobby suits me.

I guess I should give you some background. Firstly, I’ve build the mini-manzanita version of these speakers Fast, fun, Inexpensive OB project and I’ve thoroughly enjoyed them. I’m also in the process of building these Zaph|Audio with my brother and look forward to completing them in the next few weeks hopefully. As far as commercial speakers are concerned, in the past I owned a pair of B&W602 s3 standmounts but they were sold to finance my mini-manzanitas.

More recently I’ve been listening to some DIY speakers; Mark Audio extended bandwidth drivers in some rough sealed boxes. I’ve been swapping back and forward between the Alpair 5s (Alpair 5 Grey | Markaudio ) and the Alpair 7s (Alpair 7 Driver | Markaudio ). I’m enjoying both drivers, and though the 5 is more of a mid-tweeter than the 7, neither fulfils my needs in the lower octaves. What bass they do is controlled and enjoyable but I find that I can’t quite track a double bass line the way I’d like to and electronica is a little lacking (these are two types of music that I listen to a lot).


So, I have an idea that I would like to float here…..

The basic idea is to build a speaker that is modular. Each driver will have its own separate cabinet essentially stacked on top of each other. This way I can indulge my fascination with audio and try out so many of the things I’ve read about for myself rather than rely on hearsay. I will be able to “try out” different modules for the midrange and treble whilst keeping the bass module constant.

Crossovers and room corrections will all be taken care of in the digital domain using a mini-dsp 2x8 kit (miniDSP 2x8 kit | miniDSP ). Amps will be a combination of SKA modules (SKA - Simple Killer Amplifier by Greg Ball ).

So firstly, the bass module. I plan on keeping this module fairly constant. Not too much playing around with this one as really it will just be relieving the upper modules of excursion and power handling, allowing them to do what they do best. I really enjoyed the bass output of the mini-manzanita using the Peerless 12” SLS woofer and was happy running the it up to about 1khz so I have no hesitation using them more conventionally as a woofer and crossing them over somewhere between 150hz-400hz (yet to be decided, and another factor to experiment with). I’ve already got a pair on hand which is nice as I plan on each channel having dual Peerless SLS 12”.

Each driver will be housed in their own sealed cabinet with a net volume of approximately 90L. Some quick modelling in WinISD seems to show that some modest EQ should get these down as low as I want to go, and by using two drivers per channel they should be able to match up to reasonably efficient upper modules. As always, there is no replacement for displacement. The cabinets for the bass modules will be approximately 550mm wide. Again this affords me the flexibility to experiment with using wide baffles on the upper modules (without it looking stupid). The cabinets will be heavily braced using a matrix construction. I plan to stuff the cabinets with fibreglass insulation which as I understand should increase the apparent volume of the box and lower the total q.


So, I want to make sure these bass modules are going to fulfil their role as a foundation for me to experiment upon. Does anyone foresee any issues with this design? Any feedback? Criticisms? Friendly advice?

[Westy37]

Oh and a quick question:

Is there any disadvantage to having the two woofers in a shared enclosure (of twice the volume obviously) than having them in their own seperate sealed boxes?

[DrDyna]

I'd probably do separate boxes. What you're almost going to have with 12's in their own boxes are basically passive subwoofers, a great benefit of which is positioning. If you do that, you may need to go with a slightly lower crossover point than 150, I kinda like 80 for mine, but your mileage may vary.

If you have 2 12's for each channel, you may try 2 of them tuned as subs and the other 2 under the mains tuned, enclosed and crossed over differently (20-50 sub, 50-400 on the other?). I haven't finished my coffee yet, so this may be a terrible idea, however the way you describe having separate enclosures for all the drivers along with a mini dsp, you should have a ton of room to experiment.

[Westy37]

DrDyna, I appreciate your input.

The plan with the 12" is to use them more as a woofer than a subwoofer. They will be crossed over high enough that they will be quite easily located (150-400hz) the goal of which is to relieve the small extended range drivers from bass duties. In the future I may add dedicated subs to the setup crossed low (somewhere between 40-80hz) as you suggest but that's a way off. For now I need this module to play happily up to 400hz and not be easily locatable. From what I understand that necessitates them being located near to the midrange and treble modules i.e. underneath them.

My real question is whether there is a detrimental effect on SQ of having the two drivers in a common sealed enclosure?

[DrDyna]

Originally Posted by Westy37

DrDyna, I appreciate your input.

The plan with the 12" is to use them more as a woofer than a subwoofer. They will be crossed over high enough that they will be quite easily located (150-400hz) the goal of which is to relieve the small extended range drivers from bass duties. In the future I may add dedicated subs to the setup crossed low (somewhere between 40-80hz) as you suggest but that's a way off. For now I need this module to play happily up to 400hz and not be easily locatable. From what I understand that necessitates them being located near to the midrange and treble modules i.e. underneath them.

My real question is whether there is a detrimental effect on SQ of having the two drivers in a common sealed enclosure?

Yeah, if you're using all 4 of the woofers at that crossover point then that's where they'd need to be.

There shouldn't be anything wrong with using them in the same space as far as I know, perhaps someone else has more insight as I've not tried that myself just yet.

[TerryO]

Originally Posted by DrDyna

Yeah, if you're using all 4 of the woofers at that crossover point then that's where they'd need to be.

There shouldn't be anything wrong with using them in the same space as far as I know, perhaps someone else has more insight as I've not tried that myself just yet.

There's no problem with using two drivers in the same cabinet as long as you design for it. Just remember that larger cabinets will likely need more extensive bracing, etc.

Best Regards,
TerryO

[Radugazon]

As you go for a modular speaker, stay coherent with the principle and make separate cabinets for your woofers. Maybe you will rediscover later the benefit of the Geddes multisub approach.

[Westy37]

I was originally going to have a seperate cabinet for each woofer but was concerned about having the bottom woofer so close to the floor as well as having quite a distance between the two woofers. I was worried about whether this would affect the imaging and drag it towards the floor?

[Radugazon]

I think that it's not a big issue, image is drawn also to the other drivers, usually much more. OTOH, if you have four woofers very close to the floor, they will see a Pi/2 space, then you gonna get some free dB. And if there is problem, you can almays stack them or put on stands.

[Westy37]

Originally Posted by Radugazon

I think that it's not a big issue, image is drawn also to the other drivers, usually much more. OTOH, if you have four woofers very close to the floor, they will see a Pi/2 space, then you gonna get some free dB. And if there is problem, you can almays stack them or put on stands.

Thanks for the advice. May go with seperate enclosures for each of the woofers then. Going to do up a cut list tonight and hopefully get in the workshop in the next week or so and get these constructed.