Hmmm... Those are some good points. In my mind I was using these drivers as mids (DA RS180 8ohm) since I would be integrating them with an external subwoofer. However I guess technically speaking they are making up the bass section as well as the mid so in reality what I am doing is a WTW set up with one of the woofers being cut off early and the 2nd being extended out. My goal of doing a 2.5way design was to help with directivity issues that many speak of with MTM designs. I would rather keep it simple and not use any more drivers than the current 3. Do you see any benefit of doing a 2.5way design with a WTW then? I feel in theory it could still help with directivity while still giving a strong bass response with that 6db parallel boost.
Re: "strong bass response with that 6db parallel boost." - I think that will turn the MTM into a MTW; perhaps a better way to get the boost is to port the MTM box.
Re:"integrating them with an external subwoofer" - at what frequency?
Re:"integrating them with an external subwoofer" - at what frequency?
I'm not sure what the proper terminology would be then in this case since both identical woofers extend unfiltered and make up the bass section, so I am not sure if the higher driver would be considered mid, however it is making up more of the mid section than the lower driver.
I am porting the box actually. I think more will be known once I do some enclosure measurements.
In winISD the designed enclosure shows an f3 at around 50hz, so I was think somewhere around 70-80hz, especially for the home theater purposes ( will have 3 of these making up the LCR). Perhaps for music I will play it at a lower cross but still a 2.1 setup. I will have to play with it though to see what sounds best to me.
Referenced to Fs same as the manufacturers recommended minimum XO point apparently is.
I think there is order a recap of the many things the OP want to do/achieve.
First of all, baffle step. You need first to measure or at least to simulate the effect of the baffle. You'll see a gradual 6db decrease toward low frequencies, see here for a real example: Baffle step effect. If you do a crossover simulation using the 4pi mfg provided frd files, you are simulating an in-wall speaker, and using this crossover on a real speaker with a baffle will result in a boomy speaker.
A 2.5 way design, if done correctly, will fully compensate the baffle step effect. This also means that you need to place the speakers way away from walls and corners. You can see an example of a 3.5 way crossover here, look how you should cope with the different woofers: ZTD3.5
Then, the choice of WTW vs TWW. If the choice of the crossover is 2.5, then you can use both layouts, but frankly if there aren't other constraints the TWW layout should be preferred.
OTOH, if your crossover is a plain 2 way, e.g. both woofers run up to the crossover point with the tweeter, you have to do a WTW layout, but in this case a 6.5" woofer is too large for a correct implementation.
About the crossover point and slope, I think that you should aim for LR4 acoustic slopes. I usually reach this target with a 2nd order electrical crossover on the woofer and a 3rd order one on the tweeter. This way a crossover point of 1.7KHz is doable but definitely on the low side, even for a robust tweeter. If you can go a little higher up to 2KHz it would be better. Try to not exceed 2-2.2KHz because else you will have directivity mismatch between the tweeter and the 6.5" woofer.
Last point is about the bass tuning and the sub. You want to achieve good integration between the woofers and the sub. As an idea, simulate also a closed box and see what is the F6 point (F3 doesn't mean anything in acoustics).
Ralf
First of all, baffle step. You need first to measure or at least to simulate the effect of the baffle. You'll see a gradual 6db decrease toward low frequencies, see here for a real example: Baffle step effect. If you do a crossover simulation using the 4pi mfg provided frd files, you are simulating an in-wall speaker, and using this crossover on a real speaker with a baffle will result in a boomy speaker.
A 2.5 way design, if done correctly, will fully compensate the baffle step effect. This also means that you need to place the speakers way away from walls and corners. You can see an example of a 3.5 way crossover here, look how you should cope with the different woofers: ZTD3.5
Then, the choice of WTW vs TWW. If the choice of the crossover is 2.5, then you can use both layouts, but frankly if there aren't other constraints the TWW layout should be preferred.
OTOH, if your crossover is a plain 2 way, e.g. both woofers run up to the crossover point with the tweeter, you have to do a WTW layout, but in this case a 6.5" woofer is too large for a correct implementation.
About the crossover point and slope, I think that you should aim for LR4 acoustic slopes. I usually reach this target with a 2nd order electrical crossover on the woofer and a 3rd order one on the tweeter. This way a crossover point of 1.7KHz is doable but definitely on the low side, even for a robust tweeter. If you can go a little higher up to 2KHz it would be better. Try to not exceed 2-2.2KHz because else you will have directivity mismatch between the tweeter and the 6.5" woofer.
Last point is about the bass tuning and the sub. You want to achieve good integration between the woofers and the sub. As an idea, simulate also a closed box and see what is the F6 point (F3 doesn't mean anything in acoustics).
Ralf
Hello Wolf. I just want to clarify that when you say it will be easier to blend in phase that you were speaking specifically about blending the woofer into the tweeter?
There are other aspects that can be optimize with the use of separate amp/dsp per driver in a 2.5 way is what I was getting at.
At least that was my impression...
I stumbled upon my stock images showing first order vs second for 2.5way. Since OP hasn't been back yet I'll post them.
Sorry for the late reply, but thank you for your response, Ralf. That is good feedback regarding the 3rd order vs 2nd order which I am sure makes it a little "safer" to go closer to the tweeters Fs.
As far as LR4 crossover, I did some brief reading about that, and they sound a little above my abilities at this stage unfortunately. I can however aim for your suggested 3rd order slopes and see if I can improve things a little.
Your remarks about baffle step compensation are well taken and I am aware and I do not intend to order the crossover as is until I can measure the speakers in the enclosure. This post was more or less to understand the theory about 2.5 way design more fully.
Sorry for the late response. What do you mean by "pull the lower woofer away"? I know modeling is not a replacement for real life measurements and will be doing so soon, but If my modeling does not show any significant notch, is there a reason why I should expect one even if I am using 2nd order?
My last post was intended to show this effect. I meant crossing it down and shifting the phase, which happen at the same time.
Would a 2.5 way TWW have a harder time to integrate with a subwoofer? Since the second woofer is wired inverse phase from the main woofer, and since it’s a first order low pass, would this create any problems if trying to use this speaker with a pair of subwoofers in a 2.1 or 2.2 setup?
This is a wrong way to implement a 2.5 way. Both W should be wired the same way