New Builder Looking for Crossover Design Help: 2 Way Bookshelf

As an example of tweeter padding, I built a 5" 2 way designed by a kind Forum member, with a Peerless 830656 mid and a Vifa BC25 woofer. The Peerless was stated as 84.5dB and the Vifa, 90.5dB, so they have quite a severe 'L-Pad" (two resistors, one in series, one in parallel) to deal with the difference in the drivers' output, plus baffle step loss.

They sound really nice, but without the L-Pad, would sound pretty shrill, with far too much treble.

I also built a 6.5" two way with a Peerless SDS160 woofer and the same tweeter; the output of the SDS160 is around 5dB higher than the 830656, so the L-Pad is a lot milder. I tried a few different value resistors to get (almost) the sound I wanted.

Geoff
 
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Responding to Geoff's suggestion about using the Dayton RS180-8 7 inch. The sensitivity is listed at 87.1 dB and the tweeter I am considering (because it fits the current opening) is listed at 90 dB (Visaton SC5-8 Shielded 1/2" polycarbonate 8 ohm).
Will I need additional circuitry to math the sensitivity, or will they be close enough?

 
You would be able to hear a 3dB difference:, I can, even at my age; whether that sort of difference is acceptable might depend on where it is in the frequency response (i.e. because neither driver has a smooth, linear response); our ears are more sensitive to certain parts of the spectrum.

Your woofer - any woofer, as far as my limited understanding goes- will lose output when installed in a cabinet, so you may end up with, for argument's sake, 84dB from the RS180. Also, you can't assume that the Visaton measurement is correct.

I didn't twig that the Visaton is a 1/2" tweeter, I think you can ditch the RS180 as an option as the crossover point will be far too high for that woofer. From the specs, the Visaton seems like it needs to be crossed over at 4,000 Hz as its 'resonant frequency' is 2,000 Hz. Looking at the stated frequency response (below), it will need some crossover treatment to sound OK.

Have you tried a Google search for projects which use that tweeter? I would think that other products might fit and you're limiting your options if you just go for something which fits the cut-out: you can always enlarge it.

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Geoff
 
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I think you are correct. The Dayton RS 180 7" has a terrible frequency response curve and I've been trying to use Xsim to tame it. I think I will stay with the Tang Band W5" for now.
The Visaton tweeter is my choice because it matches the sensitivity of the Tang Band and the dimensions of the driver means it will fit in the box. As the box is, there is not a lot of room from the center of the tweeter's opening and the edge of the box. And the Visaton will cross around 4,000Hz (3,600 approx.) and the Tang Band begins to drop off at around 11kHz.
 

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In looking at those drivers, you’re assuming that the specs are accurate and that the mid woofer won’t lose any dB once mounted. Both of those assumptions are probably incorrect.

Re the RS180, the FR can be tamed by putting a small cap ( say 0.22 microfarad) on the woofer and careful selection of the parts values; relatively easy.

Geoff
 
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stv

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any woofer, as far as my limited understanding goes- will lose output when installed in a cabinet,
only in the range below baffle step and except in an "endless" (or very big) baffle.
baffle step is the driver's transition on the baffle from 2p (half space) to 4pi (full space, non directional) radiation.

(For the sake of completeness, the woofer does not lose sensitivity, but the sensitivity specification is related to half-space radiation per standards)
 
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Thanks STV, that's a more correct way to explain it.

An SB16pfc-8 might fit: outside width is stated as 183mm (7.2"). According to Madisound, F3 in a 10 litre vented box (1.5" x 5.3" port) would give you an F3 of 55Hz.

https://www.madisoundspeakerstore.c...sb16pfcr25-8-6-paper-cone-woofer-8-ohm-round/

I've used it in a two way with a Vifa BC25TG tweeter and it sounds really nice, although my cabinet is about 15% larger than the CVs. There are other tweeter options for it, including some from SB Acoustics.

Geoff
 
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Thank you all for your suggestions. That gives me more avenues to explore. I'm guessing that I will have to play around with extracting the frequency graphs from these web pages and see what I can generate. I did start messing around with VituixCAD today. But I'm getting the same results as with Xsim.
At some point I just need to buy a couple of drivers and try them out. Maybe purchase some cheap Amazon resistor/capacitor/inductors and play around until I get a satisfying result. Then get proper components to build the actual crossovers.
Eventually I may just have to spend some of my driver budget on a testing mic and get some additional software.
Building a sub-woofer was sooooo much easier!
 
GeoWorx DIY,

You can build the speakers the easy way also...

Are you willing to follow a proven/published design while accepting some change in the cabinet tuning (slightly higher/different bass extension)?

Would you be capable of making changes to the tweeter cut-out?

What I understand that you will be adding a layer of ply/MDF on top of the front baffle to make the woofers fit (as it might be difficult to find a woofer with the the same cut-out spec that will work in this cabinet)?

Another mid-bass that possibly can work in your existing cabinet:

https://www.parts-express.com/HiVi-F6-6-1-2-Bass-Midrange-297-440
 
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Excellent advice from zman!

I assume you:

  • want to make a pair of good sounding speakers;
  • don't want to spend money on measuring equipment you may not need again;
  • don't want to spend your $ on drivers which may not work well;
  • don't want to spend many $$ on crossover components you may not need.

If you use the same data inputs to a crossover program, you'll most probably get the same results.

I've posted this a few times, but here's the Xsim version of the well known Classix II speaker, for which I used the manufacturer supplied graphs and fp trace, compared with the real world measurement. The top graph is Xsim, the second is what it really looks like.

The same crossover values were used, so you can see from these graphs that if you rely on supplied data your results will not be accurate.

Geoff
 

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Zman, you are on to something. I have to tools and skills to build new cabinets. At this point it might be a more prudent idea. I will be building a set of tower speakers as my ultimate goal. In high school (1991) I bought a set of drivers from Radio Shack, a book on speaker design and some crossovers. Those speakers were among the best speakers I ever heard. Many of my musician friends were impressed and we listened to their original recording on those things. It was amazing. Every speaker I have purchased since then has let me down. Those speakers gave out on me about 15 years ago.
I have no idea how I was so lucky! So I naively, decided to have another go at it. Building a subwoofer was a proof of concept, then I thought rebuilding a set of Goodwill cheapos would be no big deal. I was wrong. So far I think I would be $400 into the $26 dollar pair in terms of drivers and crossover parts. So, while I could cut off the back panel and add volume to these Cerwin Vega!'s, and build new baffles, I could also drop $50 in MDF from Home Depot and the same $400 and make my own two ways.
But I rather save that all for my 3-way towers (dream build).

OR

I can try to tame these boxes as a primer to designing crossovers! It's only money and time after all. I think that if I can figure this out, I might have a decent set of bookshelf speakers to replace my Klipsch B-200 Blacks that I'm not too impressed with.

(Then maybe resign the Klipsch crossovers. 0
 
Geoff, Interesting. The testing environment from the supplier and the results from the end user "build" are going to differ for a variety of reasons. I'm guessing this is your point. Ultimately to accomplish a great set of speaker is going to require a measurement mic and a decent testing rig.

So far, i have been lucky in my speaker building experiments. So the question is do I keep going on luck, or do I turn this into more of a pursuit...... My goal is great sounding speakers. I'm tired of big box retail "trash." It's the same with car audio, you can't reply on the manufacturer to give you what you want. You have to build to the level of quality you want or can afford.
 
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Look at the Samba MT Bookshelf speaker at Parts Express - RS180P-8 (This is actually the RS180P-4) and Reference Tweeter. Detailed write-up and instructions in a PDF on the product page. If you built a new baffle for the Cerwin Vega cabinets, that would work. The Samba's have a bigger cabinet, but you could adjust the port tuning and the Cerwin Vega's size should work out okay. Note, the box tuning is only affecting things below about 80Hz, so if you are going to use the subwoofers, just cross to the sub at 100Hz or 80Hz and the box size and tuning aren't going to matter. (Building new cabs with Home Depot MDF that are the correct size to whatever existing design you might choose is not a bad idea.)

If you want to build your own...get ready to do a lot of reading and learning. But it is absolutely worth it. But don't think you can get a good speaker without investing the time and getting the right tools. You will need a measurement setup - it doesn't have to break the bank but don't try to skimp and avoid getting what you actually need, you'll eventually buy what you need anyway, wasting time and money along the way. You will definitely want to start with a two-way, so put the 3-way dream build on your calendar for a year or two.
 
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While some manufacturers' data and measurements are more 'accurate' than others, none of their drivers will be measured in your cabinet. I often use that Classix II comparison to illustrate that point.

Unless you want to dive into the hobby and intend to make at least a few speakers, I really think the best way to get something with which you'll be happy is to build an established design. There are many great designers and projects from which to choose, at various price points, configurations and degrees of SAF.

Pretty much all people who design those speakers - and do it for free, by the way - publish honest and detailed write ups about how to make them, how they sound and suggested applications.

You had a happy experience with Radio Shack drivers and (pre-built?) crossovers: what was it you liked about their sound and haven't liked about the others you bought? Were they 'monkey coffins' or bookshelves?

I'd start by looking at:
  • room size and configuration;
  • budget for drivers, crossover parts, accessories such as binding posts and feet, and cabinets;
  • music preferences;
  • desired SPL levels;
  • cabinet volume, weight, size and shape; and
  • whether you want a two or three way design
For our first pair of DIYs we had a large living room, a budget of A$1,000 for everything and limits on cabinet size/WAF. I ended up emailing the designer for his thoughts on using one of his designs for the room, but he recommended something much better in sound and suitability for the space.

With one exception, everything I've built has been others' designs and we've always been happy with the sound. The exception was where I adapted an existing crossover for a project which used the same drivers but the sound as specified was far too bright.

Geoff
 
An alternative approach, if you want to mess around a bit, might be to consider making a new baffle to fit on your Cerwin Vegas.

Then , choose a mid woofer and tweeter which have smooth responses (suggest getting ideas from Forum members) and are relatively easy to work with. As noted above by zman, you may have accept a little loss of bass performance due to cabinet size, but you say you have the bass covered in any case.

Once you've decided on the drivers you can cut a custom baffle.

Then, read up on the 'designing crossovers without measurement' thread on this Forum and your crossover book and have a play. Paul Carmody and Curt Campbell's web pages have good articles on this topic, too.

With your baffle width, I'd go for a 6"-6.5" mid woofer and a 1" tweeter to give a good range of options, paper rather than aluminium mid.

Geoff