# Surrounds on a (semi)budget



## watson b (Feb 18, 2013)

Now that I have built Zaph ZDT3.5s for my fronts, I am looking to upgrade and replace my side and back surrounds (little Onkyo HTIB speakers). My main constraint is that the sides need to be wall-mounted fairly flush, so it seems no BSC is required. Completely in-wall would probably not work as I don't have much wall cavity available, and I really don't feel like ripping out drywall.

The Modula MT would be a good match for the front drivers, but I'm not sure that really matters. My other issue with these is price. I just can't seem to justify to myself spending almost as much on the four surrounds as the three fronts, especially for the amount of work they do. I can see spending $300 or so but certainly not $600+.

So my question is this, does anyone know of an off-the-shelf MT design, probably sealed with no BSC and reasonably priced 5" or 6" drivers? That's not too much to ask, is it? :R


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## dougc (Dec 19, 2009)

I just built the Classix II as surrounds for the ZDTs for my dad. They sound great, and at $155/pr, I think hard to beat. They are a great match.


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## PassingInterest (Mar 29, 2009)

There is a small 2-way group-design described on PE's forum which is worth considering.

It was designed in 2010 but was resurrected recently when the original NHT Peerless 5 1/4" woofers became available again. Jeff Bagby designed the crossover and Charlie Laub designed the rest, as I understand it.

I built a pair for a friend's son and I enjoyed the sound for the few songs I heard through them. In fact, I intend to build another pair, so I can enjoy them myself.

Here is a link for more info. The price should be around $60.74/each.

If anyone here does build a pair, I hope you will document your build here at the Shack, so we fellow Shacksters can enjoy it. 

Here are two shots of the pair that I built, so you can see what they look like.


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## fbov (Aug 28, 2008)

watson b said:


> Now that I have built Zaph ZDT3.5s for my fronts, I am looking to upgrade and replace my side and back surrounds... wall-mounted fairly flush, so it seems no BSC is required. ...The Modula MT would be a good match for the front drivers, ...I can see spending $300 or so but certainly not $600+.
> 
> So my question is ...


The answer to your question is YES, as the small 2-way is easily the most common DIY design. And that's the downside... there are too many to choose from! Just look at InDIYana 2013!!

I'm familiar with XDT3.5's (a friend built them) and Jon Marsh's designs (have a NatP-based HT), and respect both for their ability to create excellent designs. It's fairly obvious that Jon aims high and his XO's have the parts count (and resulting high cost) to prove it. NatP is a "budget" XO design with 15 parts! Budget only compared with the Modula series... I use the Modula MTM CC so I understand your reticence regarding the Modula TM.

In contrast, Jeff Bagby's designs generally have half that number of components in his XOs, and is responsible for one of the finest TMs I've ever heard, Continuum. Does this fit your budget? They're my surrounds... wonderful dispersion characteristics, but not an on-wall design. 
http://meniscusaudio.com/continuum-pair-p-1324.html

The great downside of Continuum surrounds is sensitivity - they can't keep up with a big MTM, so they won't with ZDT3.5's. If your AVR has room correction, it will set your mains ~-6dB compared with these surrounds so the AVR sees equivalent output from all speakers. If you're just watching movies, that's not an issue as the audio is also anchored to the screen and ambiance content is low SPL. If you listen to multichannel music, that's not the case; all speakers need to be equal sensitivity or the surrounds will be a weak spot (4x the power, 1/2 the power handling capability). I'm working that direction...

On-wall mounting helps, as BSC gobbles up as much as 6dB of sensitivity. A larger driver than RS180 helps, as it brings some sensitivity and power handling. I'm looking at a 4ohm-based version of something like this so I stay in the driver family (RS mid-woofs and RS28 tweets), but with an on-wall design that's nearly the equal of the NatP MTMs:
http://www.audioheuristics.org/projects_gallery/RS225_RS28A_updates/dayton_reference_rs225.htm

But it may not fit your budget... if you like the approach, consider the reduced cost options Mark suggests. OF any of the many other options out there!

HAve fun,
Frank


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## watson b (Feb 18, 2013)

Thanks for the responses. I had actually looked at the NHT Peerless MT, although the clearance prices are gone. I estimate $100+ per pair, but still well within the range I was looking at. I may also look at Dayton BR-1s. I already have a pair where I could redo boxes into sealed.

I don't really do multi-channel music, and I don't expect a great deal from HT-only surrounds.

I still am stumped with a crossover design without BSC. Are these sealed bookshelf-type designs already designed for near-wall or on-wall mounting? If not, is it fairly simple to identify and modify the BSC components. I enjoy speaker building, but I don't think I want to get too far into the measurement tools and trial and error of crossover design.

Am I making this more complicated than it is?


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## fbov (Aug 28, 2008)

Somewhat...

BR-1 has 3dB of BSC out of a possible 6dB. I calculate that based on the advertised speaker sensitivity vs. the advertised driver sensitivity. Passive BSC is always a sensitivity hit. 

If you look at the Peerless design link, pay attention to the series inductor on the woofer. This component is primarily responsible for BSC. I've seen designers (Zaph) specify how may turns to remove from the coil. Mark simply shows different values, 2mH to start, 2.5mH after he decided he needed more BSC. Maybe 1.5mH is a good, no BSC option. You can always ask... no one with a well documented design thread minds folks asking about building their baby!

And don't forget that room correction routines are good at broadband issues like a BSC mismatch. 

HAve fun,
Frank


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## watson b (Feb 18, 2013)

fbov said:


> Somewhat...
> 
> BR-1 has 3dB of BSC out of a possible 6dB. I calculate that based on the advertised speaker sensitivity vs. the advertised driver sensitivity. Passive BSC is always a sensitivity hit.
> 
> ...


Thanks, I think I'll try the Peerless and see how it goes. As long as I know where to start tweaking I'm not afraid to unwind a coil or swap out resistors. The Emotiva has plenty of PEQ so if all else fails I think I can tame a broad band that way. 

I calculate about $150 a pair now.


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