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Old 27th December 2014, 05:38 PM   #1
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Join Date: Mar 2013
Default Thinking of a small 2,5way for small rooms.

I find my current loudspeakers to be a little overpowered for my room. So I would like to maybe build a pair of smaller speakers that are better suited for my room and will hopefully perform with superior resolution.

So ideas/ideals: Small and LIGHT midwoofers in a 2,5 configuration in a sealed box with a slow sloping bass response (as the room will amplify the lower end).
As easy crossovers as possible, little interference to the signal and much easier to build (12dB). Drivers that if possible doesn't need any notch filters and stuff. Crossoverpoint 2,5-3K?

Drivers I consider:
Midwoofers:
NE123W-08 (Transducer Detail | Tymphany)
Seas W12CY003 (E0044-08S W12CY003)

NE vs W12: Cheaper, less mms(20%), higher sensitivity and more SD(10%).

Tweeters:
Scanspeak R2604/83300 (http://www.scan-speak.dk/datasheet/pdf/r2604-833000.pdf)
Scanpeak D2608/913000 (http://www.scan-speak.dk/datasheet/pdf/d2608-913000.pdf)
The D2608 seems to be the superior one looking at zaphs measurements, but as the R2604 differs a little from the XT25 that was tested makes we wonder if it could perform better. But D2608 seems better matched with impedance and sensitivity.

Here's 2 fast pics, first one is a flat panel where's the second has a 16mm 45*c stepped baffle.

Ideas?
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Old 27th December 2014, 07:01 PM   #2
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Join Date: Feb 2009
My ideas:

A 2.5 way is by nature a full baffle step compensation design, so it is better suited to medium to large rooms, as the speakers need to be distant to any boundary.

If you need 2 mid-woofer for higher SPL, then the correct design could be a MTM. A D'Appolito configuration could be feasible, and AFAIK the final version of this configuration calls for LR4 (acoustical) slopes. You can easily target the LR4 slopes with a 2nd order (electrical) on the woofers and a 3rd order on the tweeter(*), a 2.5-3KHz crossover point seems good.

The woofers of your choice are optimized for a vented enclosure, IMHO using a sealed enclosure you won't have any bass. The suitable volume for 2 woofers is better suited to a bookshelf kind of speaker, if you want to build a tower you need make an internal section and fill the bottom (sand).

The baffle and driver placement on the baffle should be simulated with an appropriate software, sometimes a careful placement can alleviate some irregularities of the FR (a dip or a bump). For example I had a success "placing" the baffle step bump where there was a dip in the FR of the woofer.

I haven't used the XT tweeter or its variants but I think that for a 2.5-3KHz crossover point and a LR4 slope I'd opt for that instead of the D2608.

Ralf

(*) For good phase alignment, no need for a stepped baffle.
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Old 27th December 2014, 11:21 PM   #3
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Even if the driver isn't "suited" for a closed cabinet doesn't mean that it won't work. I have to run my B&W bookself speakers sealed, and it works and they are not designed for it. Without sealing them the low end bass becomes way too powerful. I also had to move the speakers 70cm from the wall and the sofa 30cm from the wall in order not to get killed. I also live in a apartment, so my neighbors would probably be happy with a little less oomph. And I for one would be happy with something that sounds great at lower pressure.

I don't know how much bafflestep compensation would be ideal for my situation, but with 2,5way I could lose some filter in the chain.
Calculating on a 170x450mm baffle would give me 6dB boost at 500hz with 7,5dB boost peak at 1000hz accordingly to "Edge".

I would just be happy with less low-end than my current speakers as for bass.
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Old Yesterday, 12:46 AM   #4
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Your AVR doesn't have a bass adjustment?
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Old Yesterday, 01:43 AM   #5
jReave is offline jReave  Canada
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Using Unibox,

Vifa NE123-8, F3=136Hz sealed
Seas W12CY003, F3=150Hz sealed.

I can't imagine that either of those is going to give you enough bass no matter how much room gain you are getting.

Try using Jeff B's diffraction program, here. It will also give you a good look at how much gain you are likely to get from your room. You should discover that the gain from an average size room doesn't begin until much lower than the F3 of the above drivers.

And while you're at it, if you want to keep your xo to a minimum, you should be looking for a driver with a FR that when combined with baffle diffraction produces a workably smooth response. In particular, if you've got natural peaking at the same frequency in the driver that you get with diffraction, so around 1500Hz with a 6" wide cabinet for eg, you might want to re-think one or both of them.

Given your stated goals, I would think that the driver you want to be looking at is one of the 5" classic Revelators, like the Scanspeak 15W8530K-00. Sealed F3 is about 65Hz in 10L. And 1 of those will go plenty loud for a small apartment given its generous xmax. The crossover won't be the most simplistic but it will still sound fantastic. That's why it's considered one of the best mid/woofers out there. I speak from personal experience on this one.
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Old Yesterday, 08:22 AM   #6
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Adjusting the bass with EQ is cheating, where's the fun in that?

Jeff B's program needs Excel, and I don't have that. This: Tolvan Data is what I used to simulate the baffle step. As for the baffles size, I could go batshit crazy and do something like a 350x1500mm floorstander with offset drivers. Edge gives me +/- 1dB from 300hz with a 5inch driver on a 350x1500mm baffle.

The 15W8530K-00 seems like a very good driver accordingly to Zaphs measurements. I've also heard the System Audio Master 2K that has a driver based on the 15W and it was very impressive. And I've thought a lot about it earlier, even thought about doing a 2,5way MTMWW(would probably be awesome, but concerned that the tweeter and mid filter would get too complicated). The coating and low sensitivity are the only things that initially puts me off. What part of the crossover won't be simplistic? I could easily go 2,5way if it's the baffle step that you are thinking about. I also agree on that the earlier drivers I mentioned would probably not cut it in the bass region, don't know really why I didn't simulate them. Guess I got carried away by the idea of the midrange that a small and superlight driver maybe could reproduce. I know that there are a lot of speculation on that the acceleration-factor doesn't affect the drivers response within the usable range for a woofer, but I'm a little superstitious . And the lower Q on the 15W compared to NE123Ws bigger brother NE149W does mean that it's more damped than NE149W and even if the mms is higher, the membrane could stop faster? Link to NE149W: Transducer Detail | Tymphany The NE drivers intrigue me a little by using a newer design than most of the drivers on the market, even speakers have to evolve sometime.

I don't really know what to believe in to be honest, there are so many people saying against each other. Some say that a driver with high qts will sound better at lower levels because it's not as damped. So in that case the NE149W could sound better than the 15W. My current B&W 705 speakers probably breaks all the rules with its super damped 6,5" woofer in a sealed box crossed at 3700Hz with a 12dB filter, but it still sounds very good.

Money is not the biggest problem with this project, the problem is how a noob like me could end up with something good.

Room is 4,9x3,5x2,5meters btw.
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Old Yesterday, 11:54 AM   #7
ODougbo is offline ODougbo  United States
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Location: Maryland USA
Tobiasbredin,
If you want to play it safe, this might work for you. A very well liked, popular 2.5 design with affordable drivers. There are two xo designs on the page, series & parallel.
I built a pair last year with the parallel xo; very, very nice speakers, they just disappear in the room. The bass is impressive and will vibrate the floor now and then at moderate levels.
diVine Audio | Ansonica

Also have MTM's here, which are fantastic but you do have to have them up pretty high of the floor, center should be close to ear level.
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Old Yesterday, 12:40 PM   #8
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Quote:
Jeff B's program needs Excel, and I don't have that.
...
Money is not the biggest problem with this project, the problem is how a noob like me could end up with something good.
As I see it, if you want to design something on your own, you need the proper tools, in this case excel(*). I recently bought a new license for windows 7 pro and office 2003 basic and installed an old laptop.
You should also have measurement gear, but IMHO this should be in addition to simulation tools.

Quote:
Even if the driver isn't "suited" for a closed cabinet doesn't mean that it won't work. I have to run my B&W bookself speakers sealed, and it works and they are not designed for it. Without sealing them the low end bass becomes way too powerful.
The problem with a commercial speaker is that the bass tuning is fixed, but if you design the box you can tune it to your taste (and room). In this case a low tuning can blend better in your placement than the "ideal" flat FR. You can simulate the effect with Unibox.

The NE149 won't have any bass in a sealed box, but a 7L vented to 50Hz box should give IMHO a good bass.

Ralf

The really good thing about the Jeff B's suite is that they work together: simulate bass, simulate baffle step and diffraction, blend together, go into PCD and simulate a crossover. The only price to pay is excel ...
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Old Yesterday, 05:16 PM   #9
jReave is offline jReave  Canada
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+1 on trying to obtain Excel if you want to design your own. The Edge is good (especially if you are working with odd baffle shapes) but it doesn't allow you to see what the effects are of chamfered or rounded edges.

To give you an idea of what your room is contributing, see the chart below. This is from The Diffraction and Boundary Simulator program and shows you the LF gain in a room your size with about 60% leakage, an average amount.

Above about 30Hz, there is less than 3dB gain. So unless the F3 of your speakers is lower than that, you shouldn't be getting any bass boost above a flat response due to the room gain.

Which leads me to wonder if your problem isn't coming from boundary reinforcement instead. Do you have the speakers well out into free space or are they close to walls or on a shelf or something similar? Because this is a different scenario. The 2nd chart shows you the gain you can get when the drivers are 36" above the floor, 12" from the back wall and 6" from the side wall just as an example. Now you're looking at all kinds of gain in the 50Hz to 300Hz zone which will indeed give you boomy bass.

Identifying the source of the problem is important because each one will result in different design decisions and therefore different driver choices.

Then again, maybe your ears just happen to be super sensitive to LF??
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File Type: gif Gain1 16ft 60%.gif (11.6 KB, 31 views)
File Type: gif Boundary 36x12x6.gif (12.3 KB, 31 views)
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Old Yesterday, 09:12 PM   #10
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The left speaker stands 50cm from the sidewall and 70cm from the back wall, the right speaker stands 70cm out from the back wall and about 2meters from the right wall. Concrete apartment. I got some bass absorbers on the way, but they won't help very much and I can't go all out as I have to live there as well. Maybe stuffing the sofa with rockwool or build a resonator out of it could help.

Added a picture of the beasts, they are sealed as the bass is just WAY over the top with open ports.

I'm not very interested in vented designs are they are more complicated and can give some problems, and with low frequency response being the problem I don't see any need for it at all. A low qct sealed enclosure a slow sloping response looks to be what I want and not hunting the lowest -3dB point for marketing reasons like the companies.
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