What can I do without drivers in hand? (1 Viewer)

[Ryan Leemhuis]

Would it be better not to do MTM with these drivers then? I really wanted to, but if it really hampers performance I would consider other options. What about a higher quality 2-way design with only 1 woofer and tweeter? You guy have done this before so I regard your opinions very highly.

Here is some info about what I want to do:

I want to build bookshelves that have a lower end to them(not no sub worthy but enough to balance out the bass a bit more). I would like to make these a vented enclosure. They will be intended to be HT speakers but will be used more often for music as at engineering classes don't give me much time to watch movies. But I want them to be designed for movies. I wanted to try something a bit different so I was looking at cones other than paper which is why I stumbled accross the vifa's. Budget for drivers can be about $300(Lower is always better, more monet to put towards a higher end receiver ). Thank you.

 

[Todd Shore]

The efficiency of a series MTM and a MT 2-way will be the same. I think your overall logic was going in the right direction.

If you want to keep it an 8 ohm speaker then I think it would be worth looking into the GR-Research M130. These are available in 16 ohm versions (shielded, too) at http://www.gr-research.com/drivers.htm

The proprietor of GR Research is often on the Madisound board.

 

[Ryan Leemhuis]

are these the only optioned for 16 ohm speakers? I was hoping to get two 6.5". Also what is the reputation of these drivers? I ahve never heard of the company.

 

[Todd Shore]

The drivers are considered quite good. Excellant for the price, though I have not had an opportunity to hear them for myself. Do a search on Madisound board. Dannie Richie posts there often.

I don't know of any other 16 ohms drivers.

 

[Ryan Leemhuis]

So how do most people drive 4 ohm speakers? Seperate amps or $$$$ receivers?

 

[Michael R Price]

The word "nominal" in the receiver ratings doesn't mean they can't drive lower impedance loads. Unless it's a real piece of junk or has overly stringent protection circuits, any receiver is capable of driving 4 ohm loads. Better amplifiers sound better, but I wouldn't let impedance requirements get in the way of your speaker design.

 

[Todd Shore]

Exactly.

Ryan, the speaker drivers you are looking to use don't have a set impedance. They have a different impedance at different frequencies. Most speakers that are rated as 8 ohms dip down close to 6 ohms in the bass/midrange region. That is one of the things you have to watch out for when paralleling drivers and why impedance measurement is important.

Often times you won't know if the load will be a problem until you try it.

 

[Ryan Leemhuis]

well yeah I have seen the impedence curves and such but I would figure a driver rated at 4 ohms would dip even lower. If I am going to replace my fronts I want it to work in the end! What would you guys suggest doing in my case, I don't have the money for these not to work and to have to build a new pair, or buy a seperate amp. Right now I have a cheap($150) kenwood receiver and I will be selling it to my father this summer to buy myself a HK 335 or 435

 

[Seth_L]

You plug them in and use them.

Even a low end reciever can drive a 4 ohm speaker under many circumstances. You only run into problems at high volumes.

It also depends on how accurate the rating is. if a speaker is rated at 4 ohms, but is 6 ohms at most frequencies except for a dip to 4 ohms at 1kHz, prerty much anything will be able to drive them just fine. Bue, if you have a speaker that's rated at 8 ohms, but dips to 4 ohms in the 40-80Hz range it could cause a lot of recievers to shut down.

 

[Ryan Leemhuis]

so You think if I used two 8 ohm drivers in parallel I could get a loud output with a HK AVR 435? Looking at the impedence curve of the driver (MG18) it dips to 6 ohms at its lowest so wouldn't this mean that at these frequencies my speaker would tend to operate at 3 ohms nominal?

 

[Todd Shore]

Remember that it is going to take 1/4 the amp power to get the same SPL.

 

[Ryan Leemhuis]

Right I see that. I thought of something tough. If I have 4 ohm speaks mixed with 8 ohms...wouldn't they play at different volumes?

 

[Todd Shore]

If I remember correctly your tweeter is 90dB. The two woofs in parallel will be 87dB + 6dB = 93dB. If you figure that you will use 3dB of baffle step then you are right where you want to be.

It will just take a little contouring of the woofer response to make the BSC dip where you need it. Depending on what frequency you cross, the baffle step can be part of the crossover without additional circuitry.

 

[Ryan Leemhuis]

what I mean is that I will have two 4 ohm fronts and the rest(center surround) will be 8 ohms. Wouldn't they play the same material at different volumes?

 

[Todd Shore]

The HK receiver will allow you to set levels for each channel independently.

 

[Ryan Leemhuis]

I asked the question over in receivers and John Garcia says that it would not be 4 ohms stable

 

[Todd Shore]

That isn't quite what he said. Read it again.

 

[Todd Shore]

If you are looking for a definitive answer, you aren't going to get one UNLESS you happen upon someone that has built the same speakers you are looking to build and they are running off the same receiver you are looking to buy.

Ain't gonna happen.

 

[Ryan Leemhuis]

I don't think I am willing to risk having them built and end up not capable of working with my receiver that would be awful. Guess my options are those 16 ohm speakers, a MT design or a series MTM design. I will have to debate the pros and cons of each.

 

[Todd Shore]

In series or as an MT you should be able to get around 100dB at the listening position in an average room with the AVR435. Only you know if that is loud enough.